Magnetic field sensor
14 claims: 6 independent, 8 dependent
- 1(57)【特許請求の範囲】 【請求項1】印加される磁界に応じた電圧を出力するホール素子と、 前記ホール素子から出力された電圧を、第1のタイミングと第2のタイミングとで逆極性になるように切り替えて出力するスイッチ回路と、 前記スイッチ回路から入力された電圧を増幅して出力する増幅器と、 一端が前記増幅器の一方の出力端子に接続され、前記増幅器から出力された電圧を保持する記憶素子と、 前記増幅器の他方の出力端子と、前記記憶素子の他端との間に接続されたスイッチとを備え、 前記第1のタイミングで、前記スイッチが閉じて、前記増幅器から出力された電圧を前記記憶素子に保持させる一方、前記第2のタイミングで、前記スイッチが開いて、前記増幅器の前記他方の出力端子と、前記記憶素子の前記他端との間の電圧が出力されるように構成されるとともに、 前記スイッチ回路は、 第1の入力用記憶素子と第2の入力用記憶素子とを備え、 前記第1のタイミングで、前記ホール素子から出力された電圧を前記第1の入力用記憶素子に保持させるとともに、前記第2の入力用記憶素子に保持された電圧を前記増幅器に出力する一方、 前記第2のタイミングで、前記ホール素子から出力された電圧を前記第2の入力用記憶素子に保持させるとともに、前記第1の入力用記憶素子に保持された電圧を前記増幅器に出力するように構成されたことを特徴とする磁界センサ。
- 2【請求項2】請求項1の磁界センサであって、 前記記憶素子、前記第1の入力用記憶素子、および前記第2の入力用記憶素子のうちの少なくとも何れか1個の記憶素子が、キャパシタであることを特徴とする磁界センサ。
- 3【請求項3】請求項1または請求項2の何れかの磁界センサであって、 前記スイッチ、および前記スイッチ回路を構成するスイッチのうちの少なくとも一つが、 それぞれ第1の導電特性のトランジスタと第2の導電特性のトランジスタとが並列に接続されて構成された第1、第2、および第3のスイッチ素子を備え、 前記第1のスイッチ素子が、前記スイッチの一端と他端との間に設けられ、 前記第2のスイッチ素子の両端が、共に、前記第1のスイッチ素子の一端に接続され、 前記第3のスイッチ素子の両端が、共に、前記第1のスイッチ素子の他端に接続されるとともに、 前記第1のスイッチ素子の前記第1の導電特性のトランジスタ、前記第2、および第3のスイッチ素子の前記第2の導電特性のトランジスタと、 前記第1のスイッチ素子の前記第2の導電特性のトランジスタ、前記第2、および第3のスイッチ素子の前記第1の導電特性のトランジスタとが、互いに異なる論理値の2値信号で駆動されるように構成されたことを特徴とする磁界センサ。
- 4【請求項4】印加される磁界に応じた電圧を出力するホール素子と、 前記ホール素子から出力された電圧を、第1の信号期間と第2の信号期間とで逆極性になるように切り替えて出力するスイッチ回路と、 前記スイッチ回路から入力された電圧を反転及び非反転増幅して出力端子対に出力する増幅器と、 前記増幅器の前記出力端子対の一方に一端が接続されたキャパシタと、 前記増幅器の前記出力端子対の他方と前記キャパシタの他端との間に挿入接続され、第1の信号期間で閉じ第2の信号期間で開くスイッチ部と、 前記スイッチ部両端の電圧を所定の電圧と比較して、その比較結果を2値信号として出力する比較器と、 を備えたことを特徴とする磁界センサ。
- 5【請求項5】印加される磁界に応じた電圧を第1及び第2の端子対に出力するホール素子と、 第1及び第2のコンデンサと、 前記第1の端子対と前記第1のコンデンサ両端とを各々接続する第1の接続部と、 前記第2の端子対と前記第2のコンデンサ両端とを各々接続する第2の接続部と、 前記第1の接続部に挿入接続されこの第1の接続部を所定の第1の信号で閉じ第2の信号で開く第1のスイッチ部と、 前記第2の接続部に挿入接続されこの第2の接続部を前記第1の信号で開き第2の信号で閉じる第2のスイッチ部と、 入力端子に与えられた信号を増幅して出力端子に出力する増幅器と、 第1の出力端子と、 前記第1のコンデンサの一端と前記増幅器の入力端子と、及び前記第1のコンデンサの他端と前記第1の出力端子とを各々接続する第3の接続部と、 前記第2のコンデンサの一端と前記増幅器の入力端子と、及び前記第2のコンデンサの他端と前記第1の出力端子とを各々接続する第4の接続部と、 前記第3の接続部に挿入接続されこの第3の接続部を前記第1の信号で開き第2の信号で閉じる第3のスイッチ部と、 前記第4の接続部に挿入接続されこの第4の接続部を前記第1の信号で閉じ第2の信号で開く第4のスイッチ部と、 第2の出力端子と、 前記増幅器の出力端子に一端が接続され前記第2の出力端子に他端が接続された第3のコンデンサと、 前記第1及び第2の出力端子に両端が個々に接続され前記第1の信号で閉じ第2の信号で開く第5のスイッチ部とを備え、 前記第1、第2の出力端子間に信号を取り出すことを特徴とする磁界センサ。
- 6【請求項6】請求項4の磁界センサであって、さらに、 前記2値信号が入力され、前記第2の信号期間内の所定の位相に同期して、前記2値信号を保持し、出力するラッチ回路を備えたことを特徴とする磁界センサ。
- 7【請求項7】請求項5の磁界センサであって、さらに、 前記第1の出力端子と前記第2の出力端子との間の電圧を所定の電圧と比較して、その比較結果を2値信号として出力する比較器と、 前記2値信号が入力され、前記第2の信号の所定の位相に同期して、前記2値信号を保持し、出力するラッチ回路と、 を備えたことを特徴とする磁界センサ。
- 8【請求項8】請求項6または請求項7の磁界センサであって、 前記比較器の前記所定の電圧が、前記ラッチ回路の出力信号に応じて異なるように構成されたことを特徴とする磁界センサ。
- 9【請求項9】印加される磁界に応じた電圧を出力するホール素子と、 前記ホール素子から出力された電圧を、第1のタイミングと第2のタイミングとで逆極性になるように切り替えて出力する第1のスイッチ回路と、 前記第1のスイッチ回路から入力された電圧を反転及び非反転増幅して出力端子対に出力する増幅器と、 前記増幅器から出力された電圧を保持するためのキャパシタと、 前記第1のタイミングで、スイッチが閉じて、前記増幅器から出力された電圧が前記キャパシタに保持されるように、前記増幅器の出力端子対と前記キャパシタとを接続する一方、前記第2のタイミングで、スイッチが開いて、前記増幅器から出力される電圧と、前記キャパシタに保持された電圧とが、前記増幅器に入力された電圧の増幅成分が同極性で加算されるように、前記増幅器の反転出力端子および非反転出力端子、前記キャパシタとを直列に接続し、この直列接続の両端を出力端子対に接続した第2のスイッチ回路と、 前記第2のスイッチ回路の前記出力端子対の電圧を入力して所定の電圧と比較して、その比較結果を2値信号として出力する比較器と、 前記2値信号が入力され、前記第2の信号期間内の所定の位相に同期して、前記2値信号を保持し、出力するラッチ回路とを備えたことを特徴とする磁界センサ。
- 10【請求項10】印加される磁界に応じた電圧を出力するホール素子と、 前記ホール素子から出力された電圧を、第1のタイミングと第2のタイミングとで逆極性になるように切り替えて出力する第1のスイッチ回路と、 前記第1のスイッチ回路から入力された電圧を増幅して出力する増幅器と、 前記増幅器から出力された電圧を保持する記憶素子と、 前記第1のタイミングで、前記増幅器から出力された電圧が前記記憶素子に保持されるように、前記増幅器の出力端子間と前記記憶素子とを並列に接続する一方、前記第2のタイミングで、前記増幅器から出力される電圧と、前記記憶素子に保持された電圧とが、前記増幅器に入力された電圧の増幅成分が同極性で加算されるように、前記増幅器の出力端子間と前記記憶素子とを直列に接続する第2のスイッチ回路とを備え、 前記第1のスイッチ回路は、 前記ホール素子から出力された電圧を一旦保持した後、前記ホール素子から切り離された状態で出力する入力用記憶素子を備えたことを特徴とする磁界センサ。
- 11【請求項11】請求項10の磁界センサであって、 前記記憶素子がキャパシタであることを特徴とする磁界センサ。
- 12【請求項12】印加される磁界に応じた電圧を出力するホール素子と、 前記ホール素子から出力された電圧を、所定の第1の信号期間と第2の信号期間とで逆極性になるように切り替えて出力するスイッチ回路と、 前記スイッチ回路から入力された電圧を反転及び非反転増幅して出力端子対に出力する増幅器と、 前記増幅器から出力された電圧を保持するためのキャパシタと、 前記増幅器の出力端子対の一方と前記キャパシタの一端との間に挿入接続されたスイッチ部と、 前記スイッチ部両端の電圧を個々に出力する出力端子対とを備えた磁界センサ を用い、前記スイッチ部を前記第1の信号で閉じ第2の信号で開くとともに、 前記スイッチ部両端の電圧を所定の電圧と比較して、その比較結果を2値信号として出力し、前記第2の信号の所定の位相に同期して、前記2値信号を保持して出力することを特徴とする磁界検出方法。
- 13【請求項13】請求項12の磁界検出方法であって、さらに、 前記出力端子対の間の電圧を所定の電圧と比較して得られる比較結果の2値信号を、前記第2の信号の所定の位相に同期して保持させるとともに、 前記所定の電圧を、前記保持された2値信号に応じて異ならせることを特徴とする磁界検出方法。
- 14【請求項14】請求項12記載の磁界検出方法であって、さらに、一定周期毎に1回の検出動作をさせることを特徴とする磁界検出方法。
Independent claims14
213 paragraphs in 1 section, as filed
Description: TECHNICAL FIELD [Detailed description of the invention]
【0001】
[Technical field to which the invention belongs]
The present invention relates to a magnetic field sensor that includes a Hall element and an amplifier that amplifies the output voltage of the Hall element, detects a magnetic field at an installed location, and outputs a signal according to the strength of the detected magnetic field.
【0002】
[Conventional technology]
A typical magnetometer composed of a bipolar IC or a CMOS IC uses a Hall element that outputs an output voltage proportional to the strength of the magnetic field, an amplifier that amplifies the output voltage of the Hall element, and an amplifier output voltage as a predetermined reference. It is equipped with a comparator that outputs the comparison result in comparison with the voltage, and is a binary signal (0 or 1, high level or low level) depending on whether the magnetic field at the place where the magnetic field sensor is installed is stronger or weaker than a certain standard. Is to be output.
【0003】
Another magnetic field sensor includes a similar Hall element and an amplifier, and outputs an analog signal based on the output of the amplifier.
【0004】
In order to obtain an accurate comparison result or an analog signal according to the strength of the magnetic field, any of the above magnetic field sensors suppress the offset signal component contained in the signal output from the amplifier, and the magnetic field sensor ( It is necessary to keep the variation of the signal output from the amplifier small for each product). The main factors that cause the offset signal component are the offset signal component included in the output voltage of the Hall element (hereinafter referred to as "element offset voltage") and the offset existing at the input terminal of the amplifier (generally a differential amplifier). It is a signal component (hereinafter referred to as "input offset voltage"). The former is generated by the stress that the Hall element body receives from the package. Further, the latter occurs due to variations in the characteristics of the elements constituting the input circuit of the amplifier. Hereinafter, conventional techniques for suppressing these offset signal components will be described.
【0005】
(Conventional technology 1) As a technique for reducing the influence of the element offset voltage, for example, those disclosed in US Pat. No. 4,037,150 are known. That is, the Hall element used in the magnetic field sensor is generally formed in a plate shape having a geometrically equivalent shape with respect to the four terminals A, A', B, and B'as shown in the Hall element 61 shown in FIG. ing. Here, the geometrically equivalent shapes are the shape shown in the figure and the state rotated 90 degrees (A-A'), as in the quadrangular Hall element 61 shown in the figure. It means that the shape is the same as the shape in the state (rotated so as to match B-B'). The voltage generated between terminals B and B'when a power supply voltage is applied between terminals A and A'of such a Hall element 61, and terminals A and A when a power supply voltage is applied between terminals B and B'. The active signal component corresponding to the strength of the magnetic field is in phase with the voltage generated between them, and the element offset voltage is in opposite phase. Therefore, the power supply voltage from the power supply (not shown) is sequentially applied between the terminals A and A'and between the terminals B and B'of the Hall element 61 via the switch circuit 62, and between the terminals B and B'and the terminals A and B. By taking out the voltage between A'as the element output voltage and taking the average of these two element output voltages, the element offset voltage can be offset and only the effective signal component can be obtained.
【0006】
(Conventional technology 2) Further, as a magnetic field sensor capable of reducing the influence of the element offset voltage and also reducing the influence of the input offset voltage generated in the amplifier, those disclosed in Japanese Patent Application Laid-Open No. 8-201491 are known. As shown in FIG. 7, this magnetic field sensor includes a Hall element 61, a switch circuit 62, a voltage-current conversion amplifier 64/65, capacitors 66/67 as storage elements, switches 68/69, and a resistor 70. Has been done. The voltage-current conversion amplifiers 64 and 65 have high input / output impedance, and convert the input voltage into a current for output. The switch 68 closes in response to the pulse of the first phase in the first phase signal (a) shown in the timing chart of FIG. 8, while the switch 69 closes the second phase in the second phase signal (b). It is designed to close in response to the pulse of. Further, the switch circuit 62 has a power supply and voltage / current conversion amplifier 64 (not shown) and terminals A of the Hall element 61, as described later, in response to the first phase pulse and the second phase pulse. The connection with A', B, B'is switched. That is, this magnetic field sensor outputs a voltage corresponding to the strength of the magnetic field by the two-step operation of the first and second timings corresponding to the pulses of the first and second phases as described below. It has become like.
【0007】
First, at the first timing, the power supply voltage is applied between the terminals A and A'of the Hall element 61 via the switch circuit 62, and the voltage Vh between the terminals B and B'is applied to the voltage-current conversion amplifier 64. Entered. Therefore, as shown in the following equation (1), the voltage-current conversion amplifier 64 outputs a current IOUT1 proportional to the sum of the voltage Vh between the terminals B and B'and the input offset voltage Voff.
【0008】
IOUT1 = α (Vh + Voff) (1) Here, α is the mutual conductance of the voltage-current conversion amplifier 64 (a proportionality constant that is a conversion coefficient from voltage to current), and Vh is the voltage between terminals B and B'of the Hall element 61 (input to the voltage-current conversion amplifier 64). Voltage), Voff is the input offset voltage of the voltage-current conversion amplifier 64.
【0009】
Further, at this first timing, the switches 68 and 68 are closed, while the switches 69 and 69 are opened, so that the current IOUT1 output from the voltage-current conversion amplifier 64 flows into the capacitors 66 and 67, and the capacitors 66 and 67 Is charged and a charging voltage is generated. The difference voltage between the charging voltages of the capacitors 66 and 67 is input to the voltage-current conversion amplifier 65, and the voltage-current conversion amplifier 65 has a magnitude proportional to the difference voltage of the charging voltage, and the voltage-current conversion amplifier 64 and the voltage-current conversion amplifier 64. Outputs the current in the opposite direction (the direction that cancels the charging current to the capacitors 66 and 67). This current increases as the charging of the capacitors 66 and 67 progresses, and eventually the same magnitude as the output current of the voltage-current conversion amplifier 64, that is, all the current output from the voltage-current conversion amplifier 64 is drawn into the voltage-current conversion amplifier 65. When this happens, the charging current to the capacitors 66 and 67 becomes 0 and the equilibrium state is reached. At this time, the current IOUT2 output from the voltage-current conversion amplifier 65 has the opposite polarity to IOUT1 and has the same absolute value as the following equation (2).
【0010】
IOUT2 = -α (Vh + Voff) (2) Next, at the second timing, switches 68 and 68 open and switches 69 and 69 close. Therefore, the electric charge accumulated in the capacitors 66 and 67 is retained as it is (therefore, the charging voltage is also maintained), and the voltage-current conversion amplifier 65 continues to flow the output current IOUT2. Further, in this second timing, the power supply voltage is applied between the terminals B and B'of the Hall element 61 via the switch circuit 62, and the terminal A has the opposite polarity to the first timing. -The voltage between A'-Vh'is input to the voltage-current conversion amplifier 64. Therefore, the voltage-current conversion amplifier 64 outputs the current IOUT3 represented by the following equation (3).
【0011】
IOUT3 = α (-Vh'+ Voff) (3) That is, since the effect of the input offset voltage Voff is the same as the first timing regardless of the polarity of the input voltage, the output current IOUT3 of this voltage-current conversion amplifier 64 has terminals A and A'with the opposite polarity to the first timing. The current is proportional to the sum of the voltage between -Vh'and the input offset voltage Voff.
【0012】
The total current of the output current IOUT3 of the voltage-current conversion amplifier 64 and the output current IOUT2 of the voltage-current conversion amplifier 65 flows to the resistor 70 via the switches 69 and 69, and the voltage across the resistor 70 is the output of the magnetic field sensor. The voltage becomes V. Therefore, as shown in the following equation (4), the output voltage V can be obtained by canceling the influence of the input offset voltage Voff. Further, in this output voltage V, the output voltages Vh and Vh'from the Hall element 61 at the first and second timings are added. Therefore, as described in US Pat. No. 4,037,150 in the above-mentioned conventional technique 1. In addition, the effect of the element offset voltage is also offset.
【0013】
V = (IOUT2 + IOUT3) × R = -α (Vh + Vh') × R (4) (Conventional technology 3) Further, as another magnetic field sensor capable of reducing the influence of the element offset voltage and the input offset voltage, the following is also known. As shown in FIG. 9, this magnetic field sensor includes a Hall element 61, a switch circuit 62, a voltage amplifier 71, capacitors 72 and 73 having equal capacities as storage elements, and switches 74 to 76. .. The switches 74 to 76 are closed according to the pulses of the first to third phases in the first to third phase signals (a) to (c) shown in FIG. 10, respectively. That is, this magnetic field sensor outputs a voltage corresponding to the strength of the magnetic field by the operation of three steps of the first to third timings corresponding to the pulses of the first to third phases as described below. It has become like.
【0014】
First, at the first timing, as in the conventional technique 2, a power supply voltage is applied between the terminals A and A'of the Hall element 61 via the switch circuit 62, and between the terminals B and B'. The voltage Vh is input to the voltage amplifier 71. Therefore, assuming that the voltage amplification factor of the voltage amplifier 71 is β, the voltage from the voltage amplifier 71 is proportional to the sum of the voltage Vh between the terminals B and B'and the input offset voltage Voff as shown in the following equation (5). V1 is output.
【0015】
V1 = β (Vh + Voff) (5) Further, at this first timing, the capacitors 72 are charged to the voltage V1 by opening the switches 75, 75, 76, and 76 while the switches 74 and 74 are closed.
【0016】
Next, at the second timing, the power supply voltage is applied between the terminals B and B'of the Hall element 61 via the switch circuit 62, and the terminal A has the opposite polarity to the first timing. -The voltage between A'-Vh' is input to the voltage amplifier 71. Therefore, the voltage V2 represented by the following equation (6) is output from the voltage amplifier 71.
【0017】
V2 = β (-Vh'+ Voff) (6) That is, since the effect of the input offset voltage Voff (as described for the voltage-current conversion amplifier 64 in the prior art 2) is the same as the first timing regardless of the polarity of the input voltage, the output voltage of the voltage amplifier 71 V2 is a voltage proportional to the sum of the voltage -Vh'between terminals A and A', which has the opposite polarity to the first timing, and the input offset voltage Voff. Further, at this second timing, the capacitors 73 are charged to the voltage V2 by opening the switches 74, 74, 76, and 76 while the switches 75 and 75 are closed.
【0018】
Next, at the third timing, switches 74, 74, 75, and 75 open, while switches 76 and 76 close, and the capacitors 72 and 73 are the terminals 72a and 73b, and the terminals 72b and 73a, respectively. Connected in parallel so that they are connected. Therefore, since the capacities of the capacitors 72 and 73 are equal to each other as described above, the voltage V across the capacitors 72 and 73 is the average voltage of -V1 and V2 as shown in the following equation (7).
【0019】
V = (-V1 + V2) / 2 = -β (Vh + Vh') / 2 (8) Therefore, similarly to the conventional technique 1, the output voltage V that offsets the influence of the input offset voltage Voff and the influence of the element offset voltage can be obtained.
【0020】
[Problems to be Solved by the Invention]
However, the above-mentioned conventional magnetic field sensor has a problem that it is difficult to keep the circuit scale small for suppressing the influence of the input offset voltage. That is, conventional technology 2 requires two voltage-current conversion amplifiers, two capacitors, and four switches. Conventional technology 3 requires one voltage amplifier but two capacitors and six switches. I need. Moreover, the voltage-current conversion amplifier and the voltage amplifier are two-output type amplifiers having a non-inverting output (plus output) and an inverting output (minus output), and such an amplifier has a large number of elements constituting the output section. In addition, it occupies a large chip area when forming an IC.
【0021】
Further, in recent years, magnetic field sensors have come to be used in devices operated by batteries such as mobile phones, and reduction of current consumption of the magnetic field sensors has also become an important technical issue. As a means used to reduce the current consumption, it is common to adopt an intermittent operation in which the current consumption is reduced to zero for a certain period of time by using a counter or the like.
【0022】
However, depending on the set in which the magnetic field sensor is used, there is a limit to the time during which the sensor operation can be stopped, and the problem is how many steps can be achieved for one detection operation. Specifically, in the first conventional example, the magnetic field is measured in two steps of the first phase and the second phase. In the second conventional example, the magnetic field is measured in three steps from the first to the third phase.
【0023】
In view of the above points, the present invention can detect the magnetic field with high accuracy by suppressing the influence of the offset signal component (variation) included in the output of the magnetic field sensor, particularly the input offset voltage generated in the amplifier, and the circuit scale. The challenge is to make it possible to reduce the manufacturing cost. Another object of the present invention is to reduce the number of steps required for the detection operation to reduce power consumption.
【0024】
[Means for solving problems]
The solution taken by the invention of claim 1 in order to solve the above-mentioned problems is a magnetic field sensor, which is a Hall element that outputs a voltage corresponding to an applied magnetic field and a voltage output from the Hall element. A switch circuit that switches and outputs the voltage so that the first timing and the second timing have opposite polarities, an amplifier that amplifies and outputs the voltage input from the switch circuit, and one end of the amplifier. A storage element connected to the output terminal of the amplifier and holding the voltage output from the amplifier, and a switch connected between the other output terminal of the amplifier and the other end of the storage element. At the timing of 1, the switch closes to hold the voltage output from the amplifier in the storage element, while at the second timing, the switch opens to the other output terminal of the amplifier. The switch circuit is configured to output a voltage between the other end of the storage element, and the switch circuit includes a first input storage element and a second input storage element, and the first input storage element is provided. At the timing of, the voltage output from the Hall element is held by the first input storage element, and the voltage held by the second input storage element is output to the amplifier, while the second At the timing of, the voltage output from the Hall element is held by the second input storage element, and the voltage held by the first input storage element is output to the amplifier. It is characterized by that.
【0025】
As a result, the input offset voltage of the amplifier can be canceled by the simple circuit as described above, so that the input offset voltage of the amplifier is not affected, and therefore, the circuit is highly accurate, has a small variation between products, and is a circuit. It is possible to construct a small-scale and inexpensive magnetic field sensor. Furthermore, since the strength of the magnetic field can be detected in the two steps of the first and second timings, the time required for detection is short, and therefore power consumption can be reduced.
【0026】
Here, the operation of the first timing and the operation of the second timing may be performed repeatedly, or may be performed only once in response to an external request or the like. .. Further, when it is repeated, the cycle, the ratio of the operation time at the timing, the length of the period that does not belong to the operation period at any timing, etc. do not matter. For example, the same effect can be obtained by operating the magnetic field sensor intermittently at regular long intervals.
【0027】
Moreover, the voltage output from the Hall element can be once held in the first or second input storage element, and then input to the amplifier in a state of being separated from the Hall element. In this case, even if one end of the storage element is connected to an arbitrary potential, the voltage held by the storage element does not change. Therefore, as an amplifier, one of its input terminals has a predetermined potential or impedance with respect to the power supply. Can be used. (Specifically, for example, an amplifier that converts the difference voltage between two terminals of a Hall element into a voltage with respect to the potential of one output terminal of a magnetic field sensor and amplifies the voltage with respect to the potential of the one output terminal. In this case, the potential of the one output terminal may be a constant reference potential (including ground) or not the reference potential.) And, as described above, of the input terminal. An amplifier, one of which has a predetermined potential with respect to the power supply, uses a single-output amplifier that amplifies the input voltage and outputs either a non-inverting output voltage or an inverting output signal, such as an operational amplifier. It can be easily configured by forming a positive phase amplification circuit or the like. Therefore, since the number of elements constituting the output unit of the single-output amplifier as described above is considerably smaller than that of the two-output amplifier, the magnetic field sensor can be configured with a significantly smaller circuit scale and a smaller chip area.
【0028】
The invention of claim 2 is the magnetic field sensor of claim 1, wherein at least one of the storage element, the first input storage element, and the second input storage element. The storage element is a capacitor.
【0029】
By using a capacitor as a storage element as described above, it is possible to realize a magnetic field sensor that is compact and suitable for IC conversion.
【0030】
Further, the invention of claim 3 is the magnetic field sensor according to claim 1 or 2, wherein at least one of the switch and the switch constituting the switch circuit has the first conductive property. The first, second, and third switch elements are configured by connecting the transistor of the above and the transistor of the second conductive property in parallel, and the first switch element is one end and the other end of the switch. Both ends of the second switch element are connected to one end of the first switch element, and both ends of the third switch element are both of the first switch element. The transistor having the first conductive property of the first switch element, the transistor having the second conductive property of the second and third switch elements, and the transistor having the first conductive property, which are connected to the other end, and the first switch. The transistor having the second conductive property of the element and the transistor having the first conductive property of the second and third switch elements are configured to be driven by binary signals having different logic values from each other. It is characterized by that.
【0031】
As a result, even when a switch having a MOS structure is used, for example, the charge is charged between the gate-source or gate-drain parasitic capacitance and the storage element according to the change in the voltage of the gate terminal for opening and closing the switch. Since the change in the voltage held in the storage element due to the movement is prevented, a more accurate magnetic field sensor can be configured.
【0032】
Further, the invention of claim 4 is a magnetic field sensor, in which a Hall element that outputs a voltage corresponding to an applied magnetic field and a voltage output from the Hall element are used as a first signal period and a second signal. A switch circuit that switches and outputs so as to have opposite polarities depending on the period, an amplifier that inverts and non-inverting the voltage input from the switch circuit and outputs it to the output terminal pair, and the output terminal pair of the amplifier. A capacitor with one end connected to one side, and a switch unit inserted and connected between the other end of the output terminal pair of the amplifier and the other end of the capacitor, closed in the first signal period, and opened in the second signal period. It is characterized by including a comparator that compares the voltage across the switch unit with a predetermined voltage and outputs the comparison result as a binary signal.
【0033】
Thereby, as described in claim 1, the input offset voltage of the amplifier can be offset by a simple circuit, and an accurate comparison result can be output. Therefore, it is possible to realize a compact and inexpensive magnetic field sensor that is not affected by the input offset voltage and has a small variation between products.
【0034】
The invention of claim 5 is a magnetic field sensor, which comprises a Hall element that outputs a voltage corresponding to an applied magnetic field to the first and second terminal pairs, first and second capacitors, and the first and second terminals. A first connection portion that connects one terminal pair and both ends of the first capacitor, a second connection portion that connects the second terminal pair and both ends of the second capacitor, and the first connection portion. A first switch unit that is inserted and connected to the connection unit 1 and closes the first connection unit with a predetermined first signal and opens with a second signal, and a second switch unit that is inserted and connected to the second connection unit. A second switch unit that opens the connection unit with the first signal and closes it with the second signal, an amplifier that amplifies the signal given to the input terminal and outputs it to the output terminal, the first output terminal, and the above. A third connection portion connecting one end of the first capacitor and the input terminal of the amplifier, the other end of the first capacitor and the first output terminal, and one end of the second capacitor. A fourth connection portion that connects the input terminal of the amplifier, the other end of the second capacitor, and the first output terminal, and a third connection portion that is inserted and connected to the third connection portion. A third switch unit that opens with the first signal and closes with the second signal, and a second signal that is inserted and connected to the fourth connection and closes the fourth connection with the first signal. A fourth switch unit opened by, a second output terminal, a third capacitor having one end connected to the output terminal of the amplifier and the other end connected to the second output terminal, and the first and first It is characterized by having a fifth switch section in which both ends are individually connected to the second output terminal and closed by the first signal and opened by the second signal, and a signal is taken out between the first and second output terminals. And.
【0035】
As a result, as described in claim 1, the input offset voltage of the amplifier can be canceled by a simple circuit, so that there is little variation between products without being affected by the input offset voltage. A small and inexpensive magnetic field sensor can be realized. Moreover, with a simple circuit configuration, the difference voltage between the two terminals of the Hall element is converted into the voltage with respect to the potential of one output terminal of the magnetic field sensor, and the voltage with respect to the potential of one output terminal of the magnetic field sensor is converted into a single output type amplifier. A single-output amplifier can be used as an amplifier that amplifies the voltage with respect to the potential of one output terminal of the magnetic field sensor, and a magnetic field sensor having a smaller circuit scale can be configured. Here, the potential of one output terminal of the magnetic field sensor may be a constant reference potential or may not be a constant reference potential.
【0036】
The invention of claim 6 is the magnetic field sensor of claim 4, further, the binary signal is input, and the binary signal is transmitted in synchronization with a predetermined phase within the second signal period. It is characterized by having a latch circuit for holding and outputting.
【0037】
As a result, the strength of the magnetic field is detected with high accuracy as described above, so that an accurate comparison result based on this can be latched and output.
【0038】
The invention of claim 7 is the magnetic field sensor of claim 5, further, comparing the voltage between the first output terminal and the second output terminal with a predetermined voltage and comparing them. It includes a comparator that outputs the result as a binary signal, and a latch circuit that holds and outputs the binary signal in synchronization with a predetermined phase of the second signal to which the binary signal is input. It is characterized by that.
【0039】
As a result, since the strength of the magnetic field is detected with high accuracy as described above, it is possible to output an accurate comparison result based on this.
【0040】
Further, the invention of claim 8 is the magnetic field sensor of claim 6 or 7, wherein the predetermined voltage of the comparator is configured to be different depending on the output signal of the latch circuit. It is a feature.
【0041】
As a result, it is possible to give hysteresis to the judgment of the comparator and output a stable signal in which chattering to the noise signal is suppressed from the comparator, and by giving this signal to the latch circuit, the discrimination accuracy is high and stable. The signal can be output from the latch circuit.
【0042】
Further, the invention of claim 9 is a magnetic field sensor, in which a Hall element that outputs a voltage corresponding to an applied magnetic field and a voltage output from the Hall element are used as a first timing and a second timing. A first switch circuit that switches and outputs so as to have opposite polarities, an amplifier that inverts and non-inverting the voltage input from the first switch circuit and outputs it to the output terminal pair, and an output from the amplifier. A capacitor for holding the voltage, and a pair of output terminals of the amplifier and the capacitor so that the switch is closed at the first timing and the voltage output from the amplifier is held in the capacitor. On the other hand, at the second timing, the switch is opened, and the voltage output from the amplifier and the voltage held in the capacitor have the same polarity as the amplification component of the voltage input to the amplifier. A second switch circuit in which the inverting output terminal, the non-inverting output terminal, and the capacitor of the amplifier are connected in series and both ends of the series connection are connected to an output terminal pair so as to be added, and the second switch circuit. A comparator that inputs the voltage of the output terminal pair of the switch circuit, compares it with a predetermined voltage, and outputs the comparison result as a binary signal, and the binary signal is input and within the second signal period. It is characterized by including a latch circuit that holds and outputs the binary signal in synchronization with a predetermined phase of the above.
【0043】
As a result, the voltage output from the Hall element is amplified and added with the same polarity, while the input offset voltage of the amplifier is added with the opposite polarity and canceled out, so that the magnetic field is small in circuit scale. It is possible to detect a highly accurate magnetic field in which the offset signal component included in the output of the sensor is reduced. In addition, since the strength of the magnetic field can be detected in the two steps of the first and second timings, the time required for detection is short, and therefore power consumption can be reduced.
【0044】
Further, the invention of claim 10 is a magnetic field sensor, in which a Hall element that outputs a voltage corresponding to an applied magnetic field and a voltage output from the Hall element are used as a first timing and a second timing. A first switch circuit that switches and outputs so as to have opposite polarities, an amplifier that amplifies and outputs the voltage input from the first switch circuit, and a storage element that holds the voltage output from the amplifier. And, at the first timing, the output terminals of the amplifier and the storage element are connected in parallel so that the voltage output from the amplifier is held by the storage element, while the second timing. Then, the voltage output from the amplifier and the voltage held in the storage element are added between the output terminals of the amplifier and the voltage so that the amplification components of the voltage input to the amplifier are added with the same polarity. A second switch circuit for connecting a storage element in series is provided, and the first switch circuit once holds the voltage output from the Hall element and then outputs the voltage output from the Hall element in a state of being disconnected from the Hall element. It is characterized by being provided with an input storage element.
【0045】
The invention according to claim 11 is the magnetic field sensor according to claim 10, wherein the storage element is a capacitor.
【0046】
As a result, the voltage held in the storage element does not change even if one end of the storage element is connected to an arbitrary potential, and the voltage held in the storage element in a state where the storage element is separated from the Hall element. Is output, so that an amplifier having one of its input terminals having a predetermined potential or impedance with respect to the power supply can be used. Then, as described in claim 1, such an amplifier can be easily configured by forming a positive-phase amplifier circuit using a single-output amplifier, and thus a significantly smaller circuit scale. The magnetic field sensor can be configured with a small chip area.
【0047】
The invention of claim 12 is a magnetic field detection method, in which a Hall element that outputs a voltage corresponding to an applied magnetic field and a voltage output from the Hall element are combined with a predetermined first signal period. A switch circuit that switches and outputs the voltage so that it has the opposite polarity in the signal period of 2, an amplifier that inverting and non-inverting the voltage input from the switch circuit and outputs it to the output terminal pair, and an amplifier that outputs the voltage from the amplifier. A capacitor for holding the voltage, a switch unit inserted and connected between one of the output terminal pairs of the amplifier and one end of the capacitor, and an output terminal pair that individually outputs the voltage across the switch unit. The switch unit is closed by the first signal and opened by the second signal, and the voltage across the switch unit is compared with a predetermined voltage, and the comparison result is used as a binary signal. It is characterized in that it outputs, synchronizes with a predetermined phase of the second signal, and holds and outputs the binary signal.
【0048】
Thereby, by the same mechanism as described in claim 1, the input offset voltage of the amplifier can be canceled by using a small and inexpensive magnetic field sensor with a simple circuit, and an accurate comparison result can be output. be able to. Therefore, it is possible to detect with little variation between products without being affected by the input offset voltage.
【0049】
The invention of claim 13 is the magnetic field detection method of claim 12, and further, the binary signal of the comparison result obtained by comparing the voltage between the output terminal pairs with a predetermined voltage is obtained. It is characterized in that the predetermined voltage is held in synchronization with a predetermined phase of the two signals, and the predetermined voltage is changed according to the held binary signal.
【0050】
As a result, the strength of the magnetic field is detected with high accuracy as described above, so that an accurate comparison result based on this can be output, and the comparison result is provided with hysteresis to chatter with respect to the noise signal. A suppressed and stable signal can be obtained.
【0051】
Further, the invention of claim 14 is the magnetic field detection method according to claim 12, further characterized in that a detection operation is performed once at regular intervals.
【0052】
Thereby, for example, the power supply to the magnetic field sensor can be stopped during each detection operation, and the average power consumption can be suppressed to a small value.
【0053】
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
【0054】
(Embodiment 1) FIG. 1 is a circuit diagram showing the overall configuration of the magnetic field sensor according to the first embodiment of the present invention. In the figure, 1 is a Hall element, 2 is a switch circuit, 3 is a voltage amplifier, 4 is a capacitor (capacitor) which is a storage element, and 5 is a switch. The Hall element 1 is formed in a plate shape having a geometrically equivalent shape with respect to the four terminals A, A', B, and B'. The switch 5 and the switch circuit 2 are controlled by, for example, a phase signal output from a clock generation circuit (not shown). More specifically, the switch 5 closes in response to a pulse of the first phase in the first phase signal (a) shown in the timing chart of FIG. Further, the switch circuit 2 has a power supply and voltage amplifier 3 (not shown) and a Hall, as described later, in response to the pulse of the first phase and the pulse of the second phase in the second phase signal (b). The connection with each terminal A, A', B, B'of the element 1 is switched. That is, this magnetic field sensor outputs a voltage corresponding to the strength of the magnetic field by the two-step operation of the first and second timings corresponding to the pulses of the first and second phases as described below. It has become like.
【0055】
First, at the first timing, the power supply voltage is applied between the terminals A and A'of the Hall element 1 via the switch circuit 2, and the voltage Vh between the terminals B and B'is input to the voltage amplifier 3. To. Therefore, assuming that the voltage amplification factor of the voltage amplifier 3 is β, from the voltage amplifier 3, the sum of the voltage Vh between the terminals B and B'and the input offset voltage Voff of the voltage amplifier 3 as shown in the following equation (8). The voltage V1 proportional to is output. More specifically, the voltage of the non-inverting output terminal 3b (+) with reference to the inverting output terminal 3a (-) of the voltage amplifier 3 is V1.
【0056】
V1 = β (Vh + Voff) (8) Further, at this first timing, the capacitor 4 is charged to the voltage V1 by closing the switch 5. (The voltage of terminal 4b with reference to terminal 4a of capacitor 4 is V1.) Next, at the second timing, the power supply is supplied between terminals B and B'of Hall element 1 via the switch circuit 2. As the voltage is applied, the voltage -Vh'between the terminals A and A'is input to the voltage amplifier 3 so as to have the opposite polarity to the first timing. Therefore, the voltage V2 represented by the following equation (9) is output from the voltage amplifier 3.
【0057】
V2 = β (-Vh'+ Voff) (9) That is, since the effect of the input offset voltage Voff is the same as the first timing regardless of the polarity of the input voltage, the output voltage V2 of the voltage amplifier 3 is the voltage between the terminals A and A'that have the opposite polarity to the first timing. The voltage is proportional to the sum of -Vh'and the input offset voltage Voff.
【0058】
Further, at this second timing, the switch 5 is opened, and the inverting output terminal 3a and the non-inverting output terminal 3b of the voltage amplifier 3 and the capacitor 4 are connected in series between the output terminals 6 and 7. .. At this time, the charging voltage of the capacitor 4 does not change while being held by the output voltage V1 of the voltage amplifier 3 at the first timing, so that the voltage V between the output terminals 6 and 7 (the output voltage of the magnetic field sensor) V is , The sum of the voltage V2 of the non-inverting output terminal 3b based on the inverting output terminal 3a of the voltage amplifier 3 and the voltage -V1 of the terminal 4a based on the terminal 4b of the capacitor 4, that is, the following equation. As shown in (10), the voltage V2 is subtracted from the voltage V1.
【0059】
V = V2-V1 = -β (Vh + Vh') (10) Therefore, the voltage V that offsets the influence of the input offset voltage Voff is obtained as the output voltage of the magnetic field sensor. Further, in this output voltage V, the output voltages Vh and Vh'from the Hall element 61 at the first and second timings are added. Therefore, as described in US Pat. No. 4,037,150 in the above-mentioned conventional technique 1. In addition, the effect of the element offset voltage is also offset.
【0060】
As described above, compared to the magnetic field sensors (Figs. 7 and 9) described in the conventional techniques 1 and 2, the offset signal component (variation) contained in the output of the magnetic field sensor is suppressed and the accuracy is high on a smaller circuit scale. Can detect magnetic fields.
【0061】
Further, compared to the magnetic field sensor of the conventional technique 3 requiring 3 steps for one detection operation, the magnetic field sensor of the present embodiment requires only 2 steps, so that the time required for the detection operation is required. short. Therefore, for example, when the detection operation is performed once every fixed cycle and the power supply to the magnetic field sensor is stopped during each detection operation, the average power consumption can be suppressed to a small value.
【0062】
Further, since the capacitor 4 is not charged by the current output amplifier but by the voltage output voltage amplifier 3, the variation in the output voltage due to the variation in the capacitance of the capacitor 4 can be suppressed to a small extent.
【0063】
(Embodiment 2) FIG. 3 is a circuit diagram showing the overall configuration of the magnetic field sensor according to the second embodiment of the present invention. In the following embodiments, the components having the same functions as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.
【0064】
In the figure, 20 is a switch circuit and 30 is a voltage amplifier.
【0065】
The switch circuit 20 is configured by providing switches 5 ... 8 ... and capacitors 9 and 10 which are storage elements. The switches 5 ... and the switch 5 connected to the capacitor 4 in the same manner as in the first embodiment respond to the pulse of the first phase in the first phase signal (a) shown in the timing chart of FIG. On the other hand, each of the switches 8 ... Closes according to the pulse of the second phase in the second phase signal (b). The switch circuit 20 is further provided with a switch for connecting a power supply (not shown) to the Hall element 1 in response to the pulses of the first and second phases. Since the switch circuit of the first embodiment and the same switch circuit as conventionally known switch circuits can be applied, the description thereof will be omitted.
【0066】
Further, the voltage amplifier 30 has the same function of outputting a voltage proportional to the input voltage as compared with the voltage amplifier 3 of the first embodiment, but has a single output with a differential input such as an operational amplifier. It is composed of the high gain amplifier 31 of the above and two resistors 22 and 23 that determine the amplification factor (feedback amount), one of the input terminals is common to one of the output terminals, and also the output terminal 6 of the magnetic field sensor. The difference is that they are common (common terminal 30a) and that this common terminal 30a does not have high impedance with respect to the power supply. The reason why such a voltage amplifier 30 can be used will be described later.
【0067】
As described below, this magnetic field sensor generates a voltage according to the strength of the magnetic field by repeating the two-step operation of the first and second timings corresponding to the pulses of the first and second phases. It is designed to output.
【0068】
First, at the first timing, the power supply voltage is applied between the terminals A and A'of the Hall element 1 via a switch (not shown) of the switch circuit 2. At this time, the voltage Vh generated between the terminals B and B'of the Hall element 1 is applied to the capacitor 9 by closing the switches 5 and 5 connected to the capacitor 9, and the capacitor 9 is charged. Further, when the switches 5 and 5 connected to the capacitor 10 are closed, the voltage Vh held in the capacitor 10 at the second timing preceding is input to the voltage amplifier 30. (More specifically, the capacitor 10 is connected to the common terminal 30a and the non-inverting input terminal (+) of the high gain amplifier 31 via switches 5 and 5.) Therefore, from the voltage amplifier 30, the above-described implementation is performed. Similar to the second timing of Form 1 (Equation (9)), the voltage V2 (voltage of the output terminal 30b with reference to the common terminal 30a) shown in the following equation (11) is output, and the capacitor 4 is also output. The capacitor 4 is charged to this voltage V2 by closing the switch 5 connected to.
【0069】
V2 = β (-Vh'+ Voff) (11) Here, β means the amplification degree of the high gain amplifier. Next, at the second timing, the voltage Vh'between terminals A and A'is opposite to the voltage Vh between terminals B and B'at the first timing above via a switch (not shown) of the switch circuit 2. A power supply voltage is applied between the terminals B and B'of the Hall element 1 so as to have polarity. At this time, the voltage -Vh'between the terminals A and A'is applied to the capacitor 10 when the switches 8 and 8 connected to the capacitor 10 are closed, and the capacitor 10 is charged (this voltage -Vh'). Will be input to the voltage amplifier 30 as described above at the next first timing.) Further, when the switches 8 and 8 connected to the capacitor 9 are closed, the voltage Vh held in the capacitor 9 is input to the voltage amplifier 30 at the first timing. Therefore, the voltage V1 represented by the following equation (12) is output from the voltage amplifier 30 in the same manner as the first timing (equation (8)) of the first embodiment.
【0070】
V1 = β (Vh + Voff) (12) Further, at this second timing, the switch 5 connected to the capacitor 4 is opened, and the common terminal 30a and the output terminal 30b of the voltage amplifier 30 and the capacitor 4 are connected in series between the output terminals 6 and 7. It becomes a state. At this time, the charging voltage of the capacitor 4 does not change while being held by the output voltage V2 of the voltage amplifier 30 at the first timing, so that the voltage (output voltage of the magnetic field sensor) V between the output terminals 6 and 7 is , The sum of the voltage V1 of the output terminal 30b when the common terminal 30a of the voltage amplifier 30 is used as a reference and the voltage -V2 of the terminal 4a when the terminal 4b of the capacitor 4 is used as a reference, that is, the following equation (13). As shown in, the voltage V1 is subtracted from the voltage V2.
【0071】
V = V1-V2 = β (Vh + Vh') (13) As described above, similarly to the first embodiment, the offset signal component included in the output of the magnetic field sensor can be suppressed to detect the magnetic field with high accuracy. In the magnetic field sensor of the second embodiment, three steps of the second, first, and second timings are required to perform the detection operation only once, but the detection operation is performed a plurality of times. In that case, it is sufficient to simply repeat the first and second timings, and therefore the number of steps required for each detection operation can be close to two steps.
【0072】
Further, the voltage amplifier 30 is configured by using a single-output high-gain amplifier 31 with a differential input, and such a high-gain amplifier 31 has two outputs as shown in the conventional technique and the first embodiment. Since the number of elements constituting the output unit is considerably smaller than that of the type amplifier, the magnetic field sensor can be configured on a significantly smaller circuit scale. Hereinafter, the reason why the voltage amplifier 30 can be configured by using the single output high gain amplifier 31 with the differential input as described above will be described.
【0073】
For example, the potentials of the terminals B and B'when a power supply voltage is applied to the terminals A and A'of the Hall element 1 have a certain potential difference with respect to the reference potential of the power supply and the like. Therefore, when the above terminals B and B'are connected to the two input terminals of the amplifier, both of these input terminals must have a high impedance with respect to the power supply, that is, a floating potential with respect to the reference potential of the power supply and the like. There is. Further, in order to perform highly accurate detection, the amplifier needs to have a constant and accurate amplification factor. Then, in order to satisfy the above conditions, it is necessary to use a conventional technique or a two-output amplifier as shown in the first embodiment.
【0074】
On the other hand, in the magnetic field sensor of the present embodiment, for example, at the first timing, a voltage Vh between the terminals B and B'of the Hall element 1 is applied to the capacitor 9 to accumulate an electric charge, and the charge is accumulated between the two terminals. After charging so that the voltage becomes Vh, the capacitor 9 is separated from the Hall element 1 and connected to 30 at the second timing. In this case, the voltage between both terminals of the capacitor 9 does not change regardless of the potential to which one terminal is connected, unless there is an inflow or outflow of electric charge. Can be connected to. Therefore, as an amplifier, it is possible to use a single input amplifier in which one input terminal has a certain potential difference (a certain impedance) with respect to a reference potential of a power source or the like. Then, such an amplifier is formed by forming a positive phase amplifier circuit by using a high gain amplifier 31 having a small output circuit scale with a differential input, such as the voltage amplifier 30 described above (in this case). The voltage amplifier 30 itself has a single output), and can be easily configured. Therefore, it is possible to configure a highly accurate magnetic field sensor with a circuit scale smaller than that of the magnetic field sensor of the first embodiment. Further, as a simple example in principle regarding the potential of the input terminal as described above, for example, it is conceivable to use a drain grounded FET and use the gate and the ground as input terminals. However, consideration must be given to keep the amplification factor accurately constant.
【0075】
Since the potential of the common terminal 30a may be any potential as described above, it may be, for example, a fixed voltage reference potential or a potential having a predetermined potential difference from the reference potential. Further, the single output type amplifier can be used by the present invention even in a magnetic field sensor in which the potential of the negative output terminal is not a constant reference potential (including ground).
【0076】
Further, the switch 5 may be provided between the output terminal 30b and the terminal 4b, and both ends of the switch 5 may be used as output terminals.
【0077】
(Embodiment 3) FIG. 4 is a circuit diagram showing the overall configuration of the magnetic field sensor according to the third embodiment of the present invention. This magnetic field sensor is provided with a comparator 13 and a latch circuit 14 in the configuration of the first embodiment, and is a binary digit of 0 or 1 (for example, low level or high level) depending on the strength of the magnetic field. It is configured to output a signal.
【0078】
In FIG. 4, 1 to 7 are the same as those in the first embodiment. 13 is a comparator, 14 is a latch circuit, 15 is a clock generation circuit, 16 is a first phase clock generation circuit, and 17 is a second phase clock generation circuit. The comparator 13 compares the voltage output between the output terminals 6 and 7 with a predetermined reference voltage, and outputs a binary digital signal. The latch circuit 14 holds the output from the comparator 13 at the time when the pulse of the second phase falls. Further, the first phase clock generation circuit 16 and the second phase clock generation circuit 17 have the first and second phase pulses having the first and second phase pulses described in the first embodiment (FIG. 2), respectively. The phase signals (a) and (b) of are output.
【0079】
The operation of the magnetic field sensor configured as described above will be described below. In this description, it is assumed that a constant magnetic field penetrates the Hall element 1 and the Hall element output voltage is constant if offset is not taken into consideration. In the following operation, the process is the same as described in the first embodiment until the voltage corresponding to the strength of the magnetic field is output from the output terminals 6 and 7. That is, first, a clock that determines the first phase (timing) is generated by the first phase clock generation circuit 16, and according to this clock, between two terminals of a pair on one diagonal line of the Hall element 1. A power supply voltage is applied, and a Hall element output voltage proportional to the strength of the magnetic field is generated between two pairs of terminals on the other diagonal line. The switch circuit 2 operates so that this output voltage is applied to the two input terminals of the voltage amplifier 3. Therefore, a voltage proportional to the output voltage of the Hall element 1 is output from the voltage amplifier 3 and applied to the capacitor 4 via the switch 5 controlled by the first phase clock generation circuit 16, and the capacitor 4 is charged. Accumulate. When the first phase ends, the switch 5 opens and the output voltage of the voltage amplifier 3 in the first phase is held by the capacitor 4.
【0080】
Next, the second phase clock generation circuit 17 generates a clock that determines the second phase, and in response to this clock, the Hall element output voltage is generated in the Hall element 1 at the time of the first phase. The power supply voltage is applied between the pair of two terminals on the other diagonal line, and the voltage between the pair of two terminals on the other diagonal line is input to the voltage amplifier 3. Here, the switch circuit 2 switches so that the positive and negative polarities of the Hall element output voltage input from the Hall element 1 to the voltage amplifier 3 are opposite to those in the first phase. Therefore, the components of the output voltage of the voltage amplifier 3 according to the output voltage from the Hall element 1 also have the opposite polarity to those in the first phase. At this time, since the switch 5 opens, the sum of the output voltage in the first phase of the voltage amplifier 3 stored in the capacitor 4 and the output voltage in the second phase of the voltage amplifier 3 (of the above voltage). Difference depending on how the reference is taken), that is, the voltage-2βVh at which the input offset voltage Voff is offset becomes the voltage between the output terminals 6 and 7.
【0081】
Therefore, the voltage between the output terminals 6 and 7 is input between the input terminals of the comparator 13. In the comparator 13, the input voltage is compared with a predetermined reference voltage set in advance, and the comparison result (0 (for example, low level) digital signal if the input voltage is lower than the reference voltage) is high. For example, 1 (for example, high level) digital signal) is output from the output terminal of the comparator 13.
【0082】
The above comparison result is input to the latch circuit 14, and the second phase signal (b) from the second phase clock generation circuit 17 is also input, so that the end of the second phase (of the second phase) is input. It is set to latch the input voltage (comparison result) at the timing when the pulse falls). Therefore, the output terminal 18 of the latch circuit 14 outputs the latched constant value (digital value of 0 or 1) until the end of the next second phase.
【0083】
Further, in order to prevent chattering, it is preferable to feed back the output value from the output terminal 18 to the comparator 13 to change the reference voltage so that the determination has hysteresis.
【0084】
In the above example, the configuration of the first embodiment is further provided with the comparator 13 and the latch circuit 14, but the present invention is not limited to this, and the configuration of the second embodiment includes the comparator 13 and the like. May be provided.
【0085】
(Detailed example of switches that make up the magnetic field sensor) In the magnetic field sensor of each of the above embodiments, in order to perform more accurate detection, it is preferable to use the switches 5 and 8 having feedthrough countermeasures taken. That is, for example, switches 5 and 8 are used by using a bidirectional switch element having a transistor having a MOS structure in which a binary voltage corresponding to the phase signals (a) and (b) as described above is input to the gate and is controlled to open and close. When the voltage of the gate terminal of the above transistor is changed to open and close the switches 5 and 8, the parasitic capacitance between the gate and the source or between the gate and the drain is connected to the switches 5 and 8. If a charge moves between the capacitors 4, 9 and 10, the voltage between both terminals of the capacitor may fluctuate. Such fluctuations in voltage can be reliably prevented by using switches 5 and 8 as shown in FIG. That is, in FIG. 5, the switch elements 50 to 52 are configured such that N-channel and P-channel MOS transistors are connected in parallel and a binary voltage is applied to the gate of each transistor to drive the switch elements 50 to 52, respectively. It is a thing. (Here, the parasitic capacitance in the switch element 50 is set to be equal to, for example, the total parasitic capacitance in the switch elements 51 and 52.) In the switch element 50, the input / output terminals 50a and 50b are switched, respectively. It is connected to the connection terminals 5a and 5b of 5 and 8 to connect and disconnect between them. Further, the input / output terminals 51a and 51b of the switch element 51 are both connected to the input / output terminals 50a of the switch element 50, while the input / output terminals 52a and 52b of the switch element 52 are both input and output of the switch element 50. It is connected to terminal 50b. The switch element 50 and the switch elements 51 and 52 are controlled so that the phase signals (a) and (b) are controlled by voltages having opposite logics of two values output via one or two inverters, respectively. It has become. More specifically, for example, at the gate of the N-channel transistor in the switch element 50, at the high level, at the gate of the P-channel transistor. When a low-level voltage is applied, a low-level voltage is applied to the gate of the N-channel transistor in the switch elements 51 and 52, and a high-level voltage is applied to the gate of the P-channel transistor. Therefore, the movement direction of the electric charge due to the parasitic capacitance of the switch element 50 and the movement direction of the electric charge due to the parasitic capacitance of the switch elements 51 and 52 are opposite to each other, so that the movement of the electric charge is canceled. Therefore, the voltage fluctuation due to the transfer of electric charge with the capacitor 9 and the like is surely prevented.
【0086】
(Detailed example of the resistors that make up the magnetic field sensor) In the magnetic field sensor of each of the above embodiments, in order to perform more accurate detection, at least one predetermined resistor among the resistors that determine the gain (amplification rate) of the voltage amplifiers 3 and 30 is the Hall element 1. It is preferable that the product is formed by the same manufacturing method as that of the above, that is, the same material and manufacturing process. That is, for example, in the magnetic field sensor of the second embodiment (FIG. 3), when the Hall element 1 and the voltage amplifier 30 are formed on the same semiconductor chip, the resistance value of the Hall element 1 is generally also the resistance 22. The resistance value of 23 also varies due to variations in constituent materials and manufacturing conditions. When the resistance value of the Hall element 1 is small, the output voltage of the Hall element 1 becomes high. On the other hand, when the resistance value of the resistor 22 inserted between the output terminal of the high gain amplifier 31 and the inverting (minus) input terminal of the resistors 22 and 23 is small, the gain of the voltage amplifier 30 is small. Therefore, when the Hall element 1 and the resistor 22 are formed by the same material and the manufacturing process, more specifically, for example, N-type impurities are diffused on a P-type semiconductor substrate to form the Hall element 1 and the resistor 22, and the resistance is formed. When 23 is formed by a polysilicon resistor having little variation in characteristics, the output voltage becomes high when the resistance value of the Hall element 1 is small, but at that time, the resistance 22 formed in the same manner as the Hall element 1 Since the resistance value of is also small, the gain of the voltage amplifier 30 is small. On the contrary, when the resistance value of the Hall element 1 is large, the output voltage is low, but the resistance value of the resistor 22 is also large, so that the gain of the voltage amplifier 30 is large. Therefore, since the influence of the variation in the resistance value of the Hall element 1 and the influence of the variation in the resistance 22 cancel each other out, it is possible to obtain an output voltage having a small variation from the output terminals 6 and 7.
【0087】
[Effect of the invention]
The present invention can cancel the input offset voltage of the amplifier with a simple circuit. As a result, it is possible to obtain an output with little variation without being affected by the input offset voltage, and it is possible to obtain an advantageous effect that a small and inexpensive magnetic field sensor can be realized.
【0088】
Further, according to the present invention, since the magnetic field can be detected with a small number of steps, that is, in a short time, it is possible to obtain an advantageous effect that a magnetic field sensor having low power consumption can be realized.
【0089】
Further, according to the present invention, the output signal of the difference voltage of the Hall element can be converted into a voltage with respect to the reference potential or the like with a simple circuit, and the voltage with respect to the reference potential or the like can be input to the single output type amplifier. As a result, it is possible to realize a magnetic field sensor that amplifies the output signal of the difference voltage of the Hall element by a single output type amplifier having a simple output circuit and a small chip area. Therefore, an advantageous effect that a smaller and cheaper magnetic field sensor can be realized can be obtained.
【0090】
Further, according to the present invention, it is possible to obtain an advantageous effect that a magnetic field sensor capable of suppressing the variation in the output voltage to be small regardless of the variation in the resistance value of the Hall element can be realized.
【0091】
Further, according to the present invention, it is possible to realize a magnetic field sensor using a storage element that is compact and suitable for IC conversion. This has an advantageous effect that a small and inexpensive magnetic field sensor can be realized.
【0092】
Further, according to the present invention, it is possible to obtain an advantageous effect that a magnetic field sensor having a small variation in output voltage due to a variation in the capacity of a capacitor can be realized.
[Simple explanation of drawings]
[Figure 1]
It is a block diagram of the magnetic field sensor of Embodiment 1 of this invention.
[Figure 2]
It is a timing chart of Embodiments 1 to 3 of this invention.
[Fig. 3]
It is a block diagram of the magnetic field sensor of Embodiment 2 of this invention.
[Fig. 4]
It is a block diagram of the magnetic field sensor of Embodiment 3 of this invention.
[Fig. 5]
It is a block diagram of the switch of the magnetic field sensor of this invention.
[Fig. 6]
It is a block diagram of the magnetic field sensor of the prior art 1.
[Fig. 7]
It is a block diagram of the magnetic field sensor of the prior art 2.
[Fig. 8]
It is a timing chart of the conventional technique 2.
[Fig. 9]
It is a block diagram of the magnetic field sensor of the prior art 3.
[Fig. 10]
It is a timing chart of the conventional technique 3.
[Explanation of symbols]
1 Hall element 2 switch circuit 3 Voltage amplifier 3a Inverted output terminal 3b Non-inverting output terminal 4 Capacitor 4a terminal 4b terminal 5 switch 5a / 5b connection terminal 6 7 output terminal 8 switches 9 Capacitor 10 capacitors 13 Comparator 14 Latch circuit 16 First phase clock generation circuit 17 Second phase clock generation circuit 18 Output terminal 20 switch circuit 22 resistance 23 resistance 30 Voltage amplifier 30a common terminal 30b output terminal 31 High gain amplifier 50 ~ 52 Switch element 50a / 50b input / output terminals 51a / 51b input / output terminals 52a / 52b I / O terminal
10 sheets
Sheet 1 Sheet 2 Sheet 3 Sheet 4 Sheet 5 Sheet 6 Sheet 7 Sheet 8 Sheet 9 Sheet 10
Every citation, both ways
| Document | Relation | Office | Cited during |
|---|---|---|---|
| TWI504915B | Cited by | Taiwan Province of China | Examiner |
| 【文献】国際公開99/21023(WO,A1) | Non-patent | – | – |
15 members in 4 offices
Priority claims2
| Document | Office | Kind | Date |
|---|---|---|---|
| 200082115(P200082115) | Japan | – | |
| 2000082115 | Japan | A |
Members15
| Document | Office | Kind | |
|---|---|---|---|
| EP1136835A1 | European Patent Office (EPO) | A1 | |
| CN1319765A | China | A | |
| JP2001337147A | Japan | A | |
| JP3315397B2This record | Japan | B2 | |
| JP2002236160A | Japan | A | |
| JP2002303661A | Japan | A | |
| US2003205996A1 | United States of America | A1 | |
| JP3544537B2 | Japan | B2 | |
| US6777932B2 | United States of America | B2 | |
| US2004196033A1 | United States of America | A1 | |
| US2004196034A1 | United States of America | A1 | |
| CN1576874A | China | A | |
| US6861839B2 | United States of America | B2 | |
| CN1201164C | China | C | |
| US7049812B2 | United States of America | B2 |
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Numbers
- Publication
- 3315397
- Application
- 85945
Titles2
- Japanese
- 磁界センサおよび磁界検出方法
- English
- INDUSTRIAL APPLICABILITY: Magnetic field sensor and magnetic field detection method
Classification
- IPC, 2
- G01R33 07
- H03K17 90
