Omnipolar magnetic switches

TECHNICAL FIELD

0001The invention relates generally to magnetic sensors and more particularly to facilitating omnipolar behavior in magnetic field switches.

BACKGROUND

0002Magnetic field switches, such as Hall effect switches, are a type of magnetic sensor with a digital output that toggles from high to low and from low to high when certain levels of the magnetic field intensity are sensed. Such switches are often used for proximity sensing, and the magnetic field-versus-output voltage characteristics include a certain amount of hysteresis in order to provide noise immunity.

0003The output behavior of these switches can be unipolar, bipolar or omnipolar. In unipolar switches, the output is dependent upon both the magnitude of the field and the polarity. For some applications, however, dependence on the polarity is not desired, and omnipolar switches are therefore desired. Conventional omnipolar switches use, for example, two cross-coupled hysteresis comparators with digital processing or other solutions typically requiring multi-step evaluation to create omnipolar behavior. For some applications, such solutions are not appropriate because they are too slow or exhibit other undesirable characteristics.

0004Therefore, there is a need for improved omnipolar magnetic field switches.

SUMMARY

0005Embodiments relate to omnipolar magnetic switches, systems and methods.

0006In an embodiment, an omnipolar magnetic switch comprises a magnetic sensor configured to generate an electric signal from a sensed magnetic field; switching circuitry coupled to the magnetic sensor to receive and selectively invert the electric signal; a first comparator coupled to the switching circuitry to receive the electric signal or an inverted electrical signal as input from the switching circuitry and to evaluate an amplitude of the input and toggle high or low when the amplitude passes above a first threshold or below a second threshold; a second comparator coupled to inputs of the first comparator to detect positive-to-negative and negative-to-positive transitions of the electric signal generated by the magnetic sensor; and polarity detection circuitry coupled to the second comparator to detect a positive-to-negative transition and coupled to the switching circuitry to instruct the switching circuitry to selectively invert the electric signal when a positive-to-negative transition is detected.

0007In an embodiment, a method of providing an omnipolar magnetic switch comprises sensing a magnetic field signal; converting the magnetic field signal into an electric signal; detecting a positive-to-negative transition of the electric signal; inverting the electric signal upon detection of a positive-to-negative transition; and toggling an output when an amplitude of the electric signal passes above a first threshold or below a second threshold.

0008In an embodiment, an omnipolar switch comprises a magnetic sensor; switching circuitry coupled to an output of the magnetic sensor; first comparator circuitry coupled to an output of the switching circuitry; second comparator circuitry coupled to the output of the switching circuitry; polarity detecting circuitry coupled to an output of the second comparator circuitry and to an input of the switching circuitry.

0009In an embodiment, an omnipolar magnetic switch comprises a magnetic sensor configured to generate an electric signal from a sensed magnetic field; a first comparator coupled to the magnetic sensor to receive the electric signal and to evaluate an amplitude of the input and toggle high or low when the amplitude passes above a first threshold or below a second threshold; a second comparator coupled to inputs of the first comparator to detect positive-to-negative and negative-to-positive transitions of the electric signal generated by the magnetic sensor; polarity detection circuitry coupled to the second comparator to detect positive-to-negative and negative-to-positive transitions and coupled to the first comparator to instruct the first comparator to selectively invert the electric signal when positive-to-negative and negative-to-positive transitions are detected; and hysteresis and offset generation circuitry coupled between the polarity detection circuitry and the first comparator.

0010In an embodiment, a signal modulus extraction circuit comprises an electrical signal generator to generate an electrical signal; switching circuitry coupled to the signal generator to receive and selectively invert the electrical signal; a comparator coupled to an output of the switching circuitry to detect positive-to-negative and negative-to-positive transitions of the electrical signal generated by the electrical signal generator; and polarity detection circuitry coupled to an output of the comparator to instruct the switching circuitry to selectively invert the electrical signal when a positive-to-negative transition is detected.

0011In an embodiment, an omnipolar magnetic switch comprises a magnetic sensor configured to generate an electric signal from a sensed magnetic field; switching circuitry coupled to the magnetic sensor to receive and selectively invert the electric signal; a first comparator coupled to the switching circuitry to receive at least one of the electric signal or an inverted electric signal as input from the switching circuitry and to evaluate an amplitude of the input and toggle high or low when the amplitude passes above a first threshold or below a second threshold; a second comparator coupled to the magnetic sensor to receive the electric signal and detect positive-to-negative and negative-to-positive transitions of the electric signal; and polarity detection circuitry coupled to the second comparator to detect positive-to-negative and negative-to-positive transitions and coupled to the switching circuitry to instruct the switching circuitry to selectively invert the electric signal when positive-to-negative and negative-to-positive transitions are detected.

BRIEF DESCRIPTION OF THE DRAWINGS

0012The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:

0013<figref idref="DRAWINGS">FIG. 1</figref> depicts a block diagram of circuitry according to an embodiment.

0014<figref idref="DRAWINGS">FIG. 2</figref> depicts graphs of unipolar, bipolar and omnipolar behavior according to embodiments.

0015<figref idref="DRAWINGS">FIG. 3</figref> depicts simulation results according to an embodiment.

0016<figref idref="DRAWINGS">FIG. 4A</figref> depicts a block diagram of circuitry according to an embodiment.

0017<figref idref="DRAWINGS">FIG. 4B</figref> depicts a comparator circuit diagram according to an embodiment.

0018<figref idref="DRAWINGS">FIG. 5</figref> depicts a block diagram of circuitry according to an embodiment.

0019While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

0020Embodiments relate to omnipolar magnetic field switches. In one embodiment, omnipolar behavior is generated in a Hall effect switch by extracting the modulus of the electric signal generated by the Hall transducer and feeding it to a single high-precision comparator, without any sampling or additional number of processing steps. The modulus extraction and threshold evaluation can be done in parallel.

0021Referring to <figref idref="DRAWINGS">FIG. 1</figref>, an embodiment of an omnipolar magnetic switch <b>100</b> is depicted. In one embodiment, switch <b>100</b> comprises a magnetic sensor <b>102</b>, a block of switches <b>104</b>, a main comparator <b>106</b>, a polarity comparator <b>108</b>, polarity detector circuitry <b>110</b> and an output <b>112</b>.

0022In one embodiment, magnetic sensor <b>102</b> is a Hall sensor. In other embodiments, some other appropriate magnetic field sensor or element is used. Sensor <b>102</b> senses a magnetic field and converts the sensed magnetic field into a differential electrical signal, which is fed to switches block <b>104</b>, which comprises one or more switches. In embodiments, switches block <b>104</b> can pass the signal unaltered or invert its sign, as will be discussed herein below.

0023From switches block <b>104</b>, the signal is fed to main comparator <b>106</b> and polarity comparator <b>108</b>. Referring also to <figref idref="DRAWINGS">FIG. 2</figref>, comparator <b>106</b> generates four thresholds of omnipolar behavior: Bop<b>1</b>, Brp<b>1</b>, Bop<b>2</b> and Brp<b>2</b>. Within pair Bop<b>1</b> and Bop<b>2</b>, as well as pair Brp<b>1</b> and Brp<b>2</b>, each has the same amplitude but opposite signs, with the equality generated by the fact that comparator <b>106</b> sees only the modulus of the magnetic signal. Bop<b>1</b> occurs when the output switches from high to low while the magnetic field is positive. Brp<b>1</b> occurs when the output switches from low to high while the magnetic field is positive. Bop<b>2</b> occurs when the output switches from high to low while the magnetic field is negative. Brp<b>2</b> occurs when the output switches from low to high while the magnetic field is negative.

0024In one embodiment, main comparator <b>106</b> is a high-precision comparator with incorporated offset and hysteresis. Offset is defined as (Bop+Brp)/2, and an omnipolar switch has two offsets, one positive and one negative. Ideally, the values are equal. Hysteresis is defined as (Bop−Brp), and an omnipolar switch again has two which are also equal, ideally.

0025Comparator <b>108</b> is designated as a polarity comparator and is, in one embodiment, a relatively small-area, low-precision comparator when compared with comparator <b>106</b>. Comparator <b>108</b> is operable in embodiments to detect a zero-passing of the electric signal. In embodiments, some form of hysteresis is generally required by polarity comparator <b>108</b> for noise immunity at the transitions through zero.

0026The digital output of comparator <b>108</b> is fed to polarity detector circuitry <b>110</b>, a digital circuit sensitive only to the positive-to-negative transitions of the electrical signal generated at the output of switches block <b>104</b>. When such a transition is detected, circuitry <b>110</b> generates a signal that triggers switches block <b>104</b> to invert its output signal. Thus, the output signal of switches block <b>104</b> would then become positive again. A negative-to-positive transition, however, would not affect polarity detection circuitry <b>110</b>.

0027Thereby, comparator <b>106</b> can always have a positive signal at its input. This signal is the modulus of the electrical signal generated by sensor <b>102</b>. Main comparator <b>106</b> behaves like a normal comparator in a unipolar switch, but because the modulus of the magnetic signal is present at its input, omnipolar behavior is seen at output <b>112</b>.

0028Simulated signal values are depicted in <figref idref="DRAWINGS">FIG. 3</figref>, which shows the output of switch <b>100</b>, main comparator output, toggling high and low when the magnetic signal reaches the positive and negative thresholds of switch <b>100</b>. This is enabled by the polarity comparator output toggling the polarity detector output each time the magnetic field crosses zero. In one embodiment, polarity detection circuitry <b>110</b> requires a reset at start-up, and a reset signal in included in <figref idref="DRAWINGS">FIG. 3</figref>.

0029Embodiments provide advantages over conventional solutions. First, less die area is required and current consumption is reduced, at least in part because only a single high-precision comparator <b>106</b> is used and polarity comparator <b>108</b> does not require high accuracy. Further, all thresholds are symmetrical in embodiments because they are generated in a single comparator. Compared with other conventional solutions, embodiments also offer continuous time evaluation of the magnetic signal, with no extra delay on the signal path to induce omnipolar behavior. Additionally, if polarity detection circuitry <b>110</b> is kept in reset mode, switch <b>100</b> will behave as a unipolar switch, providing versatility.

0030Switch <b>100</b> can comprise additional components in other embodiments. For example, a bias block can be added to generate reference voltages and currents for other circuitry components. An oscillator and sequencer can be required in embodiments if a current spinning technique is used by Hall sensor <b>102</b> or to put the switch <b>100</b> into a different working mode, e.g., low-power. A voltage regulator can supply an internally regulated voltage to the components of switch <b>100</b>, such as if high voltage capabilities are required. An amplifier can be added if the amplitude of the signal generated by Hall sensor <b>102</b> is too small to be processed correctly. An output stage can also be added according to the output type desired, such as open-drain, push-pull, and current interface as examples. Embodiments can therefore comprise one, some or all of these and other additional components, as appreciated by those skilled in the art.

0031Another embodiment of a switch <b>120</b> is depicted in <figref idref="DRAWINGS">FIG. 4A</figref>. Switch <b>120</b> is similar to switch <b>100</b> but omits switches <b>104</b> and includes a modification to internal connections in comparator <b>106</b> to facilitate a direct coupling of polarity detection circuitry <b>110</b> to comparator <b>106</b>. A modified differential stage of comparator <b>106</b> according to an embodiment is depicted in <figref idref="DRAWINGS">FIG. 4B</figref>. Switch <b>120</b> also comprises hysteresis and offset generation circuitry <b>122</b>. Circuitry <b>122</b> generates hysteresis and offset for the output behavior of the chip. Because the signals in comparator <b>106</b> are cross-coupled after the input stage, where the hysteresis and offset are added, the latter are generated according to the polarity of the input signal. Although only specifically depicted in <figref idref="DRAWINGS">FIG. 4A</figref>, hysteresis and offset generation circuitry <b>122</b> can be included in other embodiments, including switches <b>100</b> (<figref idref="DRAWINGS">FIG. 1) and 130</figref> (<figref idref="DRAWINGS">FIG. 5</figref>).

0032In another embodiment, the inputs of polarity comparator <b>108</b> can be coupled before switches <b>104</b>, and the polarity detector <b>110</b> can be sensitive to both positive-to-negative and negative-to-positive transitions. This is depicted in circuitry <b>130</b> in <figref idref="DRAWINGS">FIG. 5</figref>.

0033Various embodiments of systems, devices and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the invention. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the invention.

0034Persons of ordinary skill in the relevant arts will recognize that the invention may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the invention may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the invention may comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art.

0035Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein.

0036For purposes of interpreting the claims for the present invention, it is expressly intended that the provisions of Section 112, sixth paragraph of 35 U.S.C. are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim.