Regulator circuit

The present invention relates to a power supply circuit, and more particularly to a regulator circuit that reduces the number of parts used, sufficiently reduces the generation of noise, and outputs a stable output voltage.

In the field where high output is required in the power supply circuit used for various devices using a battery as a power source, high efficiency operation is particularly required. In response to this requirement, if the input voltage input from the battery is higher than the output voltage, the voltage is stepped down with high efficiency, the battery is consumed, and if the input voltage input from the battery is lower than the output voltage, it is high. A buck-boost switching regulator that boosts the voltage efficiently is used as a power supply circuit.

As a buck-boost switching regulator of this type, the one shown in FIG. 7 is known (see, for example, Patent Document 1). FIG. 7 is a circuit configuration diagram showing a regulator circuit, and FIG. 8 is a configuration diagram of a regulator control circuit.

As shown in FIG. 7, the regulator circuit 100 disclosed in Patent Document 1 includes a voltage detection circuit 103, an SPDT (Single Pole Double Throw) switch SW100, a step-down regulator section 121, a step-up regulator section 122, a capacitor C102, and a load resistor. It consists of 106 and the output terminal Out. Then, the input voltage Vin is input to the regulator circuit 100 from the power supply 102 made of a battery.

The voltage detection circuit 103 inputs an input voltage Vin, compares the input voltage Vin with the output set voltage, and connects the power supply 102 to the step-down regulator section 121 or the step-up regulator section 122 depending on the magnitude of the input voltage Vin. The selection signal is output to the SPDT switch SW100.

The SPDT switch SW100 connects the power supply 102 and the step-down regulator section 121 when the input voltage Vin is higher than the output set voltage, and connects the power supply 102 and the step-up regulator section 122 when the input voltage Vin is lower than the output set voltage. And connect.

The step-down regulator unit 121 includes a step-down regulator control circuit 104, a first switch SW101, a diode D100, an inductor (coil) L100, and a capacitor C100.

The first switch SW101 and the inductor L100 are longitudinally connected between the SPDT switch 100 and the output voltage Vout side. The step-down regulator control circuit 104 inputs an input voltage Vin and outputs an output signal to the first switch SW101. The first switch SW101 inputs an output signal output from the step-down regulator control circuit 104, and operates on / off by this signal. The diode D100 is provided between the first switch SW101 and the inductor L100 and between the grounded 110, and the capacitor C100 is provided between the inductor L100 and the output voltage Vout side and between the grounded 110. There is.

On the other hand, the boost regulator unit 122 includes a boost regulator control circuit 105, a second switch SW102, an inductor L101, a diode D101, and a capacitor C101.

The inductor L101 and the diode D101 are longitudinally connected between the SPDT switch 100 and the output voltage Vout side. The boost regulator control circuit 105 inputs an input voltage Vin and outputs an output signal to the second switch SW102. The second switch SW102 is provided between the inductor L101 and the diode D101 and between the grounding 110, inputs an output signal output from the boost regulator control circuit 105, and operates on / off by this signal. The capacitor C101 is provided between the diode D101 and the output voltage Vout side and between the ground 110.

As shown in FIG. 8, the regulator control circuit is used in the step-down regulator control circuit 104 and the step-up regulator control circuit 105, and is composed of a triangular wave generation circuit 107, a comparison circuit 108, a comparator COMP, and resistors R101 and 102. ing.

Then, the comparator COMP inputs the potential Va divided by the resistors R101 and R102 provided between the output voltage Vout side and the ground 110 and the reference potential Vref, and compares and amplifies the potential Va and the reference potential Vref. , This signal is transmitted to the comparison circuit 108. On the other hand, the triangular wave generation circuit 107 generates a triangular wave and transmits this signal to the comparison circuit 108.

The comparison circuit 108 compares the output signal output from the comparator COMP with the output signal output from the triangular wave generation circuit 107, generates a pulse signal having a different pulse width depending on the magnitude of the signal level difference, and switches this signal. Send to (first switch SW101 or second switch SW102).

Here, the step-down regulator unit 121 inputs pulse signals having different pulse widths to the switch SW101 to turn the switch SW101 on and off. Then, the intermittent DC voltage is input to the LC circuit composed of the inductor L100 and the capacitor C100 by this on / off operation, and the intermittent DC voltage is lower than the input voltage Vin due to the charge / discharge phenomenon, and the capacitor is used as a continuous DC voltage. It is output via C102 and load resistance 106, and is input to the output terminal Out.

On the other hand, the boost regulator unit 122 first passes a current through the inductor L101 to charge the inductor L101. Then, when the switch SW102 is turned on, the current flowing through the inductor L101 increases and energy is stored, and when the switch SW102 is turned off, the energy charged in the inductor L101 is discharged, and a DC voltage higher than the input voltage Vin is a continuous DC voltage. It is output via C102 and load resistance 106, and is input to the output terminal Out.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2003-180072 (Page 8, Fig. 11 and Fig. 12)</text></patcit>

<p> In the regulator circuit described above, circuit components such as inductors and capacitors are provided in the step-down regulator section 121 and the step-up regulator section 122, respectively, and switches for step-down and step-up operation selection are provided, so that the circuit becomes large-scale. There is a point.</p><p> Further, since the switches for the step-down regulator section 121 and the step-up regulator section 122 are turned on and off after turning on / off the switch for selecting the step-down and boosting operation, there is a problem that frequency-multiplexed noise is generated. ..</p><p> The present invention has been made in view of the above problems, and an object of the present invention is to provide a regulator circuit that reduces the number of parts to be used, sufficiently reduces the generation of noise, and outputs a stable output voltage. There is.</p>

<p> In order to achieve the above object, the regulator circuit of one aspect of the present invention is a regulator circuit in which a voltage is supplied from an external power source and a voltage stepped down or boosted from the input voltage is output as an output voltage. A first potential in which a first potential and a first reference potential are resistance-divided by a resistor provided between the voltage side and the ground are input, and the first potential and the first reference potential are compared and amplified. The second potential and the first potential are resistance-divided by the comparator and the resistance provided between the input voltage side and the ground, and the first potential is compared with the second potential. A second comparator to be amplified, a first pulse generation circuit that inputs a signal output from the first comparator and generates a pulse signal having a different pulse width by this signal, and an output from the first comparator. A second pulse generation circuit that inputs a signal to generate a pulse signal with a different pulse width, a signal output from the second comparator, and an output from the first and second pulse generation circuits. A switching control circuit that inputs a pulse signal and controls the output of the pulse signal according to the signal level output from the second comparator, and a switching control circuit that outputs the pulse signal from the first pulse generation circuit and controls the output of the pulse signal. The output-controlled pulse signal is input to the gate to operate on / off, and the pulse signal output from the second pulse generation circuit and output-controlled by the switching control circuit is used as the gate. type in,A second switch that operates on and off, an inductor that stores or releases energy by the on / off operation of the first switch and the second switch, and an on / off operation of the first switch. When a capacitor for storing or releasing energy is provided and the sum of the input voltage and the voltage drop inside the regulator circuit is larger than the output voltage, the first switch is turned on / off to perform the operation. When the step-down operation is performed by charging and discharging the inductor and the capacitor, and the sum of the input voltage and the voltage drop inside the regulator circuit is smaller than the output voltage, the first switch is turned on and the second switch is turned on. It is characterized in that a switch is turned on and off, a boost operation is performed by charging and discharging the inductor, and a constant voltage is output.</p><p> Further, in order to achieve the above object, the regulator circuit of another aspect of the present invention is a regulator circuit in which a voltage is supplied from an external power source and a voltage stepped down or boosted from the input voltage is output as an output voltage. The first potential and the first reference potential, which are resistance-divided by the resistance provided between the first output voltage side and the ground, are input, and the first potential and the first reference potential are compared and amplified. The first comparator and the second potential and the first potential whose resistance is divided by the resistance provided between the input voltage side and the ground are input, and the first potential and the second potential are input. A second comparator that compares and amplifies the potential, a first pulse generation circuit that inputs a signal output from the first comparator and generates a pulse signal having a different pulse width by this signal, and the first pulse generator. A second pulse generation circuit that inputs a signal output from the comparator and generates a pulse signal with a different pulse width by this signal, a signal output from the second comparator, and the first and second pulse generation. A switching control circuit that inputs a pulse signal output from the circuit and outputs and controls the pulse signal according to a signal level output from the second comparator, and a switching control circuit that outputs the pulse signal and outputs the pulse signal from the first pulse generation circuit. The pulse signal whose output is controlled by the switching control circuit is input to the gate and is operated on / off by the first switch and the pulse which is output from the second pulse generation circuit and whose output is controlled by the switching control circuit. Input the signal to the gate,A second switch that operates on and off, an inductor that stores or releases energy by the on / off operation of the first switch and the second switch, and an on / off operation of the first switch. It is composed of a capacitor that stores or releases energy, a comparison circuit, and an output transistor. The comparison circuit has a third potential and a third potential that are resistance-divided by a resistor provided between the second output voltage side and the ground. A reference voltage of 2 is input, the third potential and the second reference potential are compared and amplified, and the output transistor uses the first output potential as a power source and a signal output from the comparison circuit. This output voltage is provided with an amplifier having a feedback loop structure that is input to the comparison circuit again as the resistance-divided third potential, and the input voltage and the regulator circuit. When the sum of the internal voltage drops is larger than the first output voltage, the first switch is turned on and off to charge and discharge the inductor and the capacitor to lower the voltage, and the input voltage is combined with the input voltage. When the sum of the voltage drops inside the regulator circuit is smaller than the first output voltage, the first switch is turned on, the second switch is turned on and off, and the inductor is charged and discharged. The boost operation is performed, a constant voltage is output as the first output voltage, and the amplification circuit uses the first output voltage to generate the second output voltage that is more stable than the first output voltage. It is characterized by outputting to the output terminal.If it is smaller than, the first switch is turned on, the second switch is turned on and off, the inductor is charged and discharged to boost the voltage, and a constant voltage is output as the first output voltage. The amplifier circuit is characterized in that the first output voltage is used and the second output voltage, which is more stable than the first output voltage, is output to the output terminal.If it is smaller than, the first switch is turned on, the second switch is turned on and off, the inductor is charged and discharged to boost the voltage, and a constant voltage is output as the first output voltage. The amplifier circuit is characterized in that the first output voltage is used and the second output voltage, which is more stable than the first output voltage, is output to the output terminal.</p>

<p> According to the present invention, it is possible to provide a regulator circuit that reduces the number of parts to be used, sufficiently reduces the generation of noise, and outputs a stable output voltage.</p>

Hereinafter, examples of the present invention will be described with reference to the drawings.

First, the regulator circuit according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit configuration diagram showing a regulator circuit.

As shown in FIG. 1, the regulator circuit 1 operates as a buck-boost switching regulator, and has a first pulse generation circuit 3, a second pulse generation circuit 4, a switching control circuit 5, a first comparator COMP1, and a second comparator. It consists of COMP2, first switch SW1, second switch SW2, diodes D1, D2, inductor (coil) L1, resistors R1, R2, R3, R4, and output terminal Out. Then, the input voltage Vin is input to the regulator circuit 1 from the power supply 2 composed of the battery.

The first comparator COMP1 inputs the first potential Va1 and the first reference potential Vref1 whose resistance is divided by the resistors R3 and R4 provided between the output voltage Vout side and the ground 6, and the first potential. Va1 and the first reference potential Vref1 are comparatively amplified, and the comparatively amplified signal is transmitted to the first pulse generation circuit and the second pulse generation circuit 4.

The first pulse generation circuit 3 and the second pulse generation circuit 4 function as a pulse generation circuit that transmits a pulse signal to the gate of the switch, and are composed of a triangular wave generation circuit and a comparison circuit. The comparison circuit compares the signal generated from the triangular wave generation circuit with the signal output from the first comparator COMP1 and generates pulse signals having different pulse widths depending on the magnitude of the signal level difference. Then, the first pulse generation circuit 3 and the second pulse generation circuit 4 transmit this pulse signal to the switching control circuit 5. Here, the first pulse generating circuit 3 is used for step-down and boosting, and the second pulse generating circuit 4 is used for boosting. Instead of the first pulse generating circuit 3 and the second pulse generating circuit 4, a simplified pulse generating circuit or the like that generates a step-down or boosting pulse signal by a pulse signal input from the outside may be used.

The second comparator COMP2 has a first potential Va1 whose resistance is divided by resistors R3 and R4 provided between the output voltage Vout side and the ground 6, and a resistor provided between the input voltage Vin side and the ground 6. The second potential Va2 whose resistance is divided by R1 and R2 is input, the voltage level difference between the first potential Va1 and the second potential Va2 is comparatively amplified, and the comparatively amplified signal is transmitted to the switching control circuit 5. To do.

The switching control circuit 5 inputs the pulse signal output from the first pulse generation circuit 3 and the second pulse generation circuit 4 and the signal output from the second comparator COMP2, and outputs the signal from the second comparator. Depending on the signal level, the optimum pulse signal is transmitted to the first switch SW1 and the second switch SW2 according to the step-down or boost operation of the regulator circuit 1.

The inductor L1 and the diode D2 are connected in cascade between the resistor R1 and the resistor R3. The first switch SW1 is provided between the resistor R1 and the diode D1 and inputs the pulse signal output from the switching control circuit 5 to operate for step-down and step-up. On the other hand, the second switch SW2 is provided between the inductor L1 and the diode D2 and the ground 6, and inputs the pulse signal output from the switching control circuit 5 to operate for boosting. The capacitor C1 is provided between the diode D2 and the resistor R3 and the ground 6.

Next, regarding the operation of the regulator circuit 1, when the sum of the input voltage Vin and the voltage drop inside the regulator circuit is larger than the output voltage Vout (denoted as A region), the input voltage Vin and the voltage drop inside the regulator circuit The case where the sum is smaller than the output voltage Vout (denoted as the B region) will be described separately with reference to the figure.

FIG. 2 is a pulse signal waveform diagram input to the switch of the regulator circuit, FIG. 2 (a) is a pulse signal waveform diagram input to the first switch, and FIG. 2 (b) is an input to the second switch. The pulse signal waveform diagram, FIG. 3 is an input voltage input voltage input voltage and output voltage waveform diagram of the regulator circuit.

As shown in Fig. 2, in the A region (denoted as Vin + α&gt; Vout) where the sum of the input voltage Vin and the voltage drop inside the regulator circuit is larger than the output voltage Vout, the first switch SW1 is the switching control circuit 5. The pulse signal output from is input to perform on / off operation. Here, when the input voltage Vin is large, for example, when the power supply 2 composed of a battery used for in-vehicle use has a high voltage of 14 V, the pulse signal output from the first pulse generation circuit 3 and input to the first switch SW1. Has a large pulse width and a coarse number of pulse signals. When the input voltage Vin approaches the output voltage Vout (3.3V or 5V for in-vehicle use), the pulse signal output from the first pulse generation circuit 3 and input to the first switch SW1 has a small pulse width. And the number of pulse signals becomes dense.

In the regulator circuit 1, the intermittent DC voltage is input to the LC circuit consisting of the inductor L1 and the capacitor C1 by the on / off operation of the first switch SW1, and the intermittent DC voltage is the input voltage due to the charge / discharge phenomenon. It is output as a continuous DC voltage lower than Vin.

At this time, the output voltage Vout output from the regulator circuit 1 is expressed by Vout = {Ton1 / (Ton1 + Toff1)} × Vin ..... equation (1). Here, Ton1 is the time when the first switch SW1 is on, and Toff1 is the time when the first switch is off. As can be seen from the above equation (1), the output voltage Vout can be controlled by changing the duty ratio {Ton1 / (Ton1 + Toff1)}.

On the other hand, in the B region (denoted as Vin + α Vout) where the sum of the input voltage Vin and the voltage drop inside the regulator circuit is smaller than the output voltage Vout, the first switch SW1 and the second switch SW2 are switching control circuits. The pulse signal output from 5 is input to perform on / off operation respectively. Here, when the difference between the input voltage Vin and the output voltage is small, the pulse signal is output from the first pulse generation circuit 3, is output from the pulse signal input to the first switch SW1, and is output from the second pulse generation circuit 4. The pulse signal input to the switch SW2 of 2 has a small pulse width and a coarse number of pulse signals. Then, when the difference between the input voltage Vin and the output voltage becomes large, it is output from the first pulse generation circuit 3, the pulse signal input to the first switch SW1, and the second pulse generation circuit 4. The pulse signal input to the switch SW2 of is large in pulse width and the number of pulse signals is dense.

In the regulator circuit 1, when the first switch SW1 is turned on, a current flows through the inductor L1 and the inductor L1 is charged. Then, when the second switch SW2 is turned on, the current flowing through the inductor L1 increases and energy is stored, and when the second switch SW2 is turned off, the energy charged in the inductor L1 is discharged and the DC voltage is higher than the input voltage Vin. Is output as a continuous DC voltage (Vout).

At this time, the output voltage Vout output from the regulator circuit 1 is expressed by Vout = {(Ton2 + Toff2) / Toff2} × Vin ... Equation (2). Here, Ton2 is the time when the second switch SW2 is on, and Toff2 is the time when the second switch SW2 is off. As can be seen from the above equation (2), the output voltage Vout can be controlled by changing {(Ton2 + Toff2) / Toff2}.

As shown in FIG. 3, the output voltage Vout output from the regulator circuit 1 is a constant value regardless of the magnitude of the input voltage Vin. Here, a slight ripple is generated in the output voltage Vout, but since the switching frequency and the value of the inductor L1 are optimized, the ripple level is reduced as compared with the output voltage Vout.

As described above, in the regulator circuit of this embodiment, the number of switches is reduced from 3 to 2, the number of inductors is reduced from 2 to 1, and the number of capacitors is reduced from 2 to 1, so that the circuit scale is larger than before. Can be made smaller. Therefore, the cost of the device having a built-in regulator circuit can be reduced.

Further, since the switches are operated independently during the step-down and step-up operations, frequency-multiplexed noise does not occur.

Since a switching regulator is used for step-down and step-up operations, it operates with high efficiency regardless of the magnitude of the input voltage Vin supplied from the power supply consisting of the battery.

Further, since the optimum pulse signal is input to the switch according to the step-down and step-up operations to perform the step-down and step-up operations, a stable output voltage can be output.

Next, the regulator circuit according to the second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a circuit configuration diagram showing a regulator path, and FIG. 5 is a waveform diagram of an input voltage input to the regulator circuit and an output voltage waveform output.

Hereinafter, in the present embodiment, the same components as those in the first embodiment are designated by the same reference numerals, the description of the parts will be omitted, and only the different components will be described.

As shown in FIG. 4, the regulator circuit 1a is composed of a buck-boost switching regulator 10 and a series regulator 7. Then, the input voltage Vin is input to the regulator circuit 1a from the power supply 2 composed of the battery.

The buck-boost switching regulator 10 includes a first pulse generation circuit 3, a second pulse generation circuit 4, a switching control circuit 5, a first comparator COMP1, a second comparator COMP2, a first switch SW1, and a second switch. It is composed of SW2, diodes D1, D2, inductor (coil) L1, and resistors R1, R2, R3, and R4, and has the same circuit configuration as regulator circuit 1 shown in FIG.

The series regulator 7 controls the output voltage Vout to be constant regardless of the magnitude of the load current, and is composed of an amplifier AMP, resistors R5 and R6, and an output terminal Out.

The amplifier AMP consists of a comparison circuit and an output transistor, and the comparison circuit is divided by the second reference potential Vref2 and the resistors R5 and R6 provided between the second output voltage Vout2 side and the ground 6. The potential Va3 of 3 is input, the second reference potential Vref2 and the third potential Va3 are compared and amplified, and this signal is transmitted to the output transistor.

The output transistor uses the first output voltage Vout1 output from the buck-boost switching regulator 10 as the power supply, operates by the signal output from the comparison circuit, and outputs the second output voltage Vout2. Then, the output second output voltage Vout2 is input to the comparison circuit again as the resistance-divided third potential Va3. By this feedback loop, a constant voltage is generated from the series regulator 7, and is output to the output terminal Out as an output voltage Vout.

As shown in FIG. 5, the output voltage Vout output from the regulator circuit 1a is a constant value without ripple generation regardless of the magnitude of the input voltage Vin. Since the potential difference between the first output voltage Vout1 output from the buck-boost switching regulator 10 and the second output voltage Vout2 output from the series regulator 7 is very small, the efficiency reduction in the series regulator 7 is sufficient. Can be suppressed.

As described above, in the regulator circuit of this embodiment, since the series regulator 7 is provided in the output portion of the buck-boost switching regulator 10, it is possible to eliminate the ripple of the output voltage in addition to the effect of the first embodiment.

Further, since the series regulator 7 operates with high efficiency, it operates with high efficiency as in the first embodiment.

Next, the regulator circuit according to the third embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a circuit configuration diagram showing a regulator circuit.

Hereinafter, in the present embodiment, the same components as those in the second embodiment are designated by the same reference numerals, the description of the parts will be omitted, and only the different components will be described.

As shown in FIG. 6, the regulator circuit 1b includes a buck-boost switching regulator 10a, a series regulator 7, a load resistor 8, and a third switch SW3. Then, the input voltage Vin is input to the regulator circuit 1b from the power supply 2 composed of the battery.

The buck-boost switching regulator 10a includes a first pulse generation circuit 3, a second pulse generation circuit 4, a switching control circuit 5, a first comparator COMP1, a second comparator COMP2, a first switch SW1, and a second switch. It consists of SW2, diodes D1, D2, inductor (coil) L1, and resistors R1, R2, R3, and R4.

The load resistor 8 and the third switch SW3 are longitudinally connected between the first output voltage Vout1 side of the buck-boost switching regulator 10a and the amplifier AMP.

The first output voltage Vout1 output from the buck-boost switching regulator 10a is input to the third switch SW3 via the load resistor 8 and operates on / off by the signal output from the second comparator COMP2.

The buck-boost switching regulator 10a has the same circuit configuration as the buck-boost switching regulator 10 shown in FIG. 4, except for a portion where the signal output from the second comparator COMP2 is input to the third switch SW3.

As described above, in the regulator circuit of this embodiment, in addition to the effect of the second embodiment, the on / off operation is performed between the buck-boost switching regulator 10a and the series regulator 7 by the signal output from the second comparator COMP2. Since the third switch SW3 is provided, the load is reduced until the output voltage of the buck-boost switching regulator 10a reaches a predetermined voltage value. Therefore, the rising speed of the power supply can be improved.

The present invention is not limited to the above embodiment, and various modifications may be made without departing from the spirit of the invention.

For example, in the above embodiment, the first switch SW1 and the second switch SW2 are turned on / off in the B region of Vin + α Vout to perform the step-up operation, but the first switch SW1 remains on. The second switch SW2 may be turned on / off to boost the voltage. As a method of keeping the first switch SW1 on, the switching control circuit 5 may transmit a control signal for always turning on the first switch SW1 by the signal output from the comparator COMP2.

Further, in the above embodiment, the regulator circuit is used for in-vehicle use, but it may be used as a DD converter provided inside an IC or LSI in the audio / portable field.

<figref num="1">The circuit block diagram which shows the regulator circuit which concerns on Example 1 of this invention.</figref><figref num="2">FIG. 5 is a waveform diagram of a pulse signal input to a switch of the regulator circuit according to the first embodiment of the present invention.</figref><figref num="3">The input voltage input voltage and output voltage waveform diagram which are output to the regulator circuit which concerns on Example 1 of this invention.</figref><figref num="4">The circuit block diagram which shows the regulator circuit which concerns on Example 2 of this invention.</figref><figref num="5">The input voltage input voltage and output voltage waveform diagram which are output to the regulator circuit which concerns on Example 2 of this invention.</figref><figref num="6">The circuit block diagram which shows the regulator circuit which concerns on Example 3 of this invention.</figref><figref num="7">The circuit block diagram which shows the conventional regulator circuit.</figref><figref num="8">The circuit block diagram which shows the conventional regulator control circuit.</figref>

Code description

1, 1a, 1b, 100 Regulator circuit 2, 102 Power supply (battery) 3 First pulse generation circuit 4 Second pulse generation circuit 5 Switching control circuit 6, 110 Grounding 7 Series regulator 8, 106 Load resistance 10, 10a Lifting and lowering Pressure switching regulator 103 Voltage detection circuit 104 Step-down regulator control circuit 105 Boost regulator control circuit 107 Triangular wave generation circuit 108 Comparison circuit 109 Output voltage 121 Step-down regulator section 122 Boost regulator section AMP Amplifier C1, C100, C101, C102 Condenser COMP Comparator COMP1 1st comparator COMP2 2nd comparator D1, D2, D100, D101 Diode L1, L100, L101 inductor (coil) R1, R2, R3, R4, R5, R6, R101, R102 Resistance Out Output terminal SW1, SW101 1st switch SW2, SW102 2nd switch SW3 3rd switch SW100 SPDT switch Va potential Va1 1st potential Va2 2nd potential Va3 Third potential Vin Input voltage Vref Reference potential Vref1 First reference potential Vref2 Second reference voltage Vout Output voltage Vout1 First output voltage Vout2 Second output voltage