JP2012105481A - Voltage regulating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage regulating device that operates as a step-up circuit until an input voltage Vin reaches a prescribed voltage and operates as a step-down circuit when the input voltage Vin is equal to or higher than the prescribed voltage, where it is sufficient that a switching element 3 is provided at only one location and thus cost reduction is possible.SOLUTION: Provided between a first coil 1 and a switching element 3 are a capacitor 4, which is charged through the first coil 1 when the switching element 3 is under an off-state, and a second coil 5 to which a discharge current of the capacitor 4 flows when the switching element 3 is under an on-state. A chopper control circuit 10 is provided that controls a duty ratio, at which the switching element 3 is turned on/off, in accordance with a monitor voltage Vm of a monitor circuit 9, so it becomes possible to step down and step up an output voltage Vout given from the second coil 5 to a load 8 through a diode 6 in accordance with the duty ratio. As a result, it is sufficient that the switching element 3 is provided at only one location and thus cost reduction is possible.

Description

  The present invention relates to a voltage regulator that has a step-down function that steps down an input voltage to produce an output voltage and a step-up action that steps up an input voltage to produce an output voltage. In particular, the present invention relates to a voltage adjustment device used as a power supply device for an automotive instrument using an in-vehicle power supply as an input voltage.

  Conventionally, “concept of chopper circuit” described in Non-Patent Document 1 describes a basic step-down circuit and a step-up circuit. Therefore, when the input voltage is stepped down or stepped up, it is conceivable to connect both circuits in series. FIG. 4 is an electric circuit diagram of the step-down device and the step-up device described in Non-Patent Document 1.

  4A shows the step-down circuit 20 described in Non-Patent Document 1. FIG. The step-down circuit 20 includes a transistor Tr, a diode D, a coil L, and a capacitor C. When the transistor Tr is on, a current flows from the battery E through the coil L and the load R, and when the transistor Tr is off. A current flows from the coil L to the load R and the capacitor C via the diode D.

  The step-down circuit 20 is a circuit in which current flows intermittently into the capacitor C via the coil L. In order to step down the voltage, the current flowing into the coil L may be reduced, and the ON time Ton per cycle T of the transistor Tr that repeats ON / OFF periodically may be reduced. That is, the duty ratio may be reduced. Since the output voltage Vout is a product of the input voltage Vin and the duty ratio (α = Ton / T), the output voltage Vout decreases when the duty ratio is small.

  FIG. 4B shows the booster circuit 21 described in Non-Patent Document 1. In the booster circuit 21, when the transistor Tr is turned on, a current flows through the coil L and electromagnetic energy is stored in the coil L. When the transistor Tr is turned off, a current flows through the coil L, the diode D, the capacitor C, and the load R by the high voltage induced in the coil L and the input voltage Vin.

  The booster circuit 21 is a circuit that causes the electromagnetic energy stored in the coil L to be suddenly released by turning off the transistor Tr, and generates a high induced voltage in the coil L. In order to boost the voltage, it is preferable to lengthen the ON period, increase the duty ratio α of the transistor Tr, and repeatedly turn off the transistor Tr after flowing a large current through the coil L. The output voltage Vout is expressed by the product of the input voltage Vin and (1 / 1-α).

Katsuya Hiraji, “Technical Memo No. 20060918 of Chopper Circuit, Concept of Chopper Circuit, 2006/9/18, Maizuru National College of Technology, [Search November 2, 2010], Internet <URL: http: //hirachi.cocolog-nifty .com / kh / files / 20060918-1A.pdf # search = 'Concept of chopper circuit'>

  When the power supply voltage is a car battery, it usually varies from 10 volts to 16 volts. When such a power supply voltage is used to supply power to, for example, a load in an automotive instrument panel, and the specification of a preferable input voltage of the load is about 16 volts, the booster circuit 21 of the prior art is usually used. Is used.

  However, when the power supply voltage is an automobile battery, sometimes the power supply voltage jumps to about 18 volts due to a sudden decrease in the in-vehicle electric load. In the case of such a power supply voltage, the required specification cannot be satisfied if the booster circuit 21 is used. That is, the booster circuit 21 cannot obtain an output voltage Vout that is equal to or lower than the input voltage Vin of about 18 volts. Thus, when the specification of the output voltage Vout required for the vehicle instrument panel is about 16 volts, it operates as a booster circuit when the input voltage is 10 to 16 volts, and is stepped down when the input voltage is 16 volts or more. What is needed is a voltage regulator that operates as a circuit.

  FIG. 5 is an electric circuit diagram of a voltage regulator configured based on the prior art. In this way, it is conceivable that the step-down circuit 20 and the step-up circuit 21 are combined as shown in FIG. 5 and the power supply voltage is first stepped down and the stepped-down voltage is stepped up to meet the output voltage specification. However, in such a circuit, it is necessary to provide at least two switching elements shown as transistors Tr in FIG. Accordingly, the number of field effect transistors (also referred to as FETs) that form switching elements increases, resulting in an increase in cost.

  In view of the above problems, the present invention operates as a step-up circuit until the input voltage reaches a predetermined voltage, and operates as a step-down circuit when the input voltage exceeds the predetermined voltage. An object of the present invention is to provide a voltage regulator that can be used. The content of Non-Patent Document 1 described as the prior art can be introduced or incorporated by reference as an explanation of the technical elements described in this specification.

  In order to achieve the above object, the present invention employs the following technical means. That is, according to the first aspect of the present invention, there is provided a voltage adjusting device that adjusts an input voltage and applies the load to a load, the first coil to which the input voltage is applied, A switching element that conducts current, a capacitor that branches from between the first coil and the switching element, and that is charged via the first coil when the switching element is off, and that the capacitor is discharged when the switching element is on The second coil through which the current flows, the diode that rectifies the voltage across the second coil and applies it to the load, the monitor circuit that monitors the voltage applied to the load between the second coil and the load, and the monitoring result by the monitor circuit Accordingly, a chopper control circuit for controlling a duty ratio at which the switching element is turned on / off is provided.

  According to the present invention, the capacitor is branched from between the first coil and the switching element and is charged via the first coil when the switching element is in the off state, and the capacitor is charged when the switching element is in the on state. Since the second coil through which the discharge current flows is provided, the current flows from the first coil side to the second coil side via the capacitor as the switch means is turned on and off, and the switch means is turned on and off at both ends of the second coil. A voltage corresponding to the duty ratio is generated. In addition, since it has a chopper control circuit that controls the duty ratio at which the switching element is turned on / off according to the monitor voltage of the monitor circuit, the voltage applied to the load from the second coil via the diode is adjusted according to the duty ratio. Can do. Therefore, the switching element may be provided at one place in order to turn on / off the current of the first coil, and the cost can be reduced.

  In the invention according to claim 2, the chopper control circuit sets the duty ratio for turning on and off the switching element to be higher than the reference duty ratio when the value resulting from the monitoring is lower than the reference value, and the value resulting from the monitoring is The duty ratio at which the switching element is turned on / off when higher than the reference value is lower than the reference duty ratio.

  According to the present invention, the duty ratio at which the switching element is turned on / off when the value resulting from the monitoring is lower than the reference value is set higher than the reference duty ratio, and the switching element is turned on / off when the value resulting from the monitoring is higher than the reference value. Since the duty ratio is lower than the reference duty ratio, the voltage applied to the load can be automatically adjusted to a predetermined voltage.

  The invention according to claim 3 is characterized in that the reference duty ratio is between 30% and 70% of the duty ratio, which is the ratio of time during which the switching element is turned on / off at a constant time period. It is said.

  According to the present invention, since the reference duty ratio is between 30% and 70%, a sufficient range of voltage to be stepped down or boosted can be obtained, and the output voltage specification is easily satisfied.

  The invention according to claim 4 is characterized in that an output-side capacitor is provided in parallel with the load, and the output-side capacitor is charged via a diode.

  According to the present invention, the output-side capacitor is provided in parallel with the load, and the output-side capacitor is charged via the diode, so that a smoothed voltage can be supplied to the load.

  According to a fifth aspect of the present invention, the monitor circuit includes a voltage dividing circuit that detects a voltage across the output side capacitor.

  According to the present invention, the monitor circuit includes the voltage dividing circuit that detects the voltage across the output-side capacitor, so that the value of the monitor result smoothed by the output-side capacitor can be supplied to the chopper control circuit.

  The invention described in claim 6 is characterized in that the input voltage is a vehicle battery voltage, and the load is an electric load for display in the instrument panel of the vehicle.

  According to the present invention, since the input voltage is the vehicle battery voltage and the load is the display electrical load in the vehicle instrument panel, the display electrical load in the vehicle instrument panel even if the battery voltage fluctuates. A stable voltage can be supplied to the display, and the operation of the electric load for display can be stabilized and failure can be prevented.

It is an electric circuit diagram of the voltage regulator in 1st Embodiment of this invention. In FIG. 1, it is an electric circuit diagram which shows the flow of an electric current when a switching element turns on. In FIG. 1, it is an electric circuit diagram which shows the flow of an electric current when a switching element turns off. 2 is an electric circuit diagram of a step-down device and a step-up device described in Non-Patent Document 1. FIG. It is an electrical circuit diagram of the voltage regulator comprised based on a prior art.

(One embodiment)
Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3. FIG. 1 is an electric circuit diagram of a voltage regulator according to an embodiment of the present invention. In this embodiment, a booster circuit unit having a first coil 1 and a charge / discharge rectifier circuit unit having a second coil 5 are coupled by a capacitor 4 to boost the voltage when the input voltage Vin is 16 volts or less. When the voltage Vin exceeds 16 volts, the voltage is stepped down.

  First, the circuit configuration will be described. In FIG. 1, a power terminal 2 to which a power source from a battery mounted on a vehicle is connected is present at one end of the first coil 1. The specification of the power supply voltage from the battery, that is, the input voltage Vin of the circuit of FIG. 1 is normally about 10 to 16 volts, but it is increased to a voltage of about 18 volts exceeding 16 volts due to a sudden change in the on-vehicle load of the battery. May be.

  When such a power supply voltage is used as it is, for example, when a fluorescent display tube that is a load of an automotive instrument having a preferable voltage of about 16 volts is energized, the voltage is too low or too high, and the voltage is high. There is a possibility of failure, and when the voltage is low, flicker may occur or display may not be possible.

  This problem cannot be solved by using only a step-down circuit or only a step-up circuit, and requires a circuit that steps down the voltage once and boosts it, or a circuit that steps up the voltage when there is a step-down. . In the prior art of FIG. 4 described above, the step-down circuit and the step-up circuit are cascade-connected to step down the voltage once and then the step-up circuit is configured. In this embodiment, however, the step-up circuit is stepped up when there is a step-up circuit. Configure.

  The other end of the first coil 1 in FIG. 1 is connected to the ground potential via the source and drain of a field effect transistor that constitutes the switching element 3. A capacitor 4 is connected between the first coil 1 and the switch means 3, and the other end of the capacitor 4 is connected to the second coil 5 and the anode of the diode 6. The diode 6 is a Schottky diode with good high-speed response.

  The current flowing through the diode 6 is charged in the output-side capacitor 7, and the load 8 is connected to both ends of the output-side capacitor 7. Resistors 9a and 9b forming a voltage dividing circuit are connected in parallel with the output side capacitor 7. The resistors 9a and 9b constitute a voltage dividing circuit 9 that forms a monitor circuit that monitors the output voltage Vout as a whole. The voltage between the resistors 9a and 9b is a monitor voltage Vm for monitoring the output voltage Vout, and is supplied to the chopper control circuit 10 (hereinafter also referred to as chopper IC10).

  The chopper IC 10 is connected to the gate of the switching element 3 and controls the on / off state of the switching element 3. Thereby, even if the power supply voltage of the power supply terminal 2, that is, the input voltage Vin is about 10 to 16 volts in a normal state and sometimes about 18 volts, the voltage across the output side capacitor 7, That is, the specification of the output voltage Vout is maintained at about 16 volts.

  The chopper IC 10 controls a duty ratio (conduction rate) that is a ratio of time during which the switching element 3 that performs the chopping operation is turned on and off in a certain period. The electric circuit in FIG. 1 is boosted when the duty ratio of the switching element 3 exceeds a predetermined reference duty ratio (50% in one embodiment), and the duty ratio is increased to the predetermined reference duty ratio. The constants of the circuit elements of the electric circuit are set so that the voltage is stepped down as it decreases. That is, when the duty ratio is 50%, which is the reference duty ratio, the input voltage Vin applied to the power supply terminal 2 is selected as a circuit constant that appears as the output voltage Vout as it is without being stepped down or boosted.

  The chopper circuit 10 includes a comparison circuit 10a that compares the monitor voltage Vm with the reference value Vb, and a pulse generation circuit 10b that changes the duty ratio of the pulse signal according to the deviation from the reference value detected by the comparison circuit 10a. Have

  Next, the operation of the voltage regulator for the power supply voltage having the above circuit configuration will be described. 2 is an electric circuit diagram showing a current flow when the switching element 3 is turned on in FIG. 1, and FIG. 3 is an electric circuit diagram showing a current flow when the switching element 3 is turned off in FIG. As shown in FIG. 2, when the switching element 3 is turned on, a current flows through the first coil 1, and electromagnetic energy is stored in the first coil 1.

  Specifically, when the switching element 3 is turned on, a current starts to flow through the first coil 1. As is well known, this current gradually increases so as to have a predetermined time constant. When the duty ratio of the switching element 3 increases, the ON time of the switching element 3 per cycle increases. Therefore, the amount of current passing through the first coil 1 increases.

  Thus, when the switching element 3 is turned on, a current flows through the first coil 1 as indicated by an arrow Y21, and a discharge current of the capacitor 4 that has been charged previously flows as indicated by an arrow Y22 via the switching element 3. . Due to the discharge of the capacitor 4, electromagnetic energy is accumulated in the second coil 5, and a downward voltage is generated in the second coil 5.

  Next, as shown in FIG. 3, when the switching element 3 is turned off, no current flows through the first coil 1 through the switching element 3, so that an induced voltage is generated in the first coil 1 and electromagnetic energy is released. Due to the input voltage Vin of the power supply terminal 2 and the induced voltage, a current flows through the capacitor 4 through the diode 6 as indicated by an arrow Y31 in FIG. 3, and the capacitor 4 is charged. This charging current also flows through the output-side capacitor 7. Further, an upward voltage is generated in the second coil 5 as indicated by an arrow Y32.

  Thus, the current rectified by the diode 6 flows into the output-side capacitor 7, and the voltage across the output-side capacitor 7 is provided as the output voltage Vout. The capacitor 4 is charged via the first coil 1 when the switching element 3 is turned off, and is discharged via the switching element 3 and the second coil 5 when the switching element 3 is turned on.

  When the duty ratio of the switching element 3 is 50% and the ON time and the OFF time in one cycle of ON / OFF of the switching element 3 are equal, the both-ends voltage of the output side capacitor 7, that is, the output voltage Vout is the power supply terminal The circuit constants of the first coil 1, the second coil 5, and the capacitor 4 are selected so that they are substantially equal to the input voltage Vin of 2, and are not balanced and boosted.

  If the duty ratio of the switching element 3 is slightly shifted to the increase side or the decrease side from the state where the capacitor 4 is repeatedly charged and discharged with the duty ratio of 50%, the balance is lost. When the duty ratio is shifted to the decreasing side as compared with the 50% duty ratio state, a voltage lower than the input voltage Vin of the power supply terminal 2 appears as the output voltage Vout at the voltage across the output-side capacitor 7, It was found that an antihypertensive effect occurs.

  Conversely, when the duty ratio is shifted to an increase side as compared with the 50% duty ratio state, a voltage higher than the input voltage Vin of the power supply terminal 2 is applied to the output voltage Vout across the output-side capacitor 7. It was found that a pressurizing action occurs. This is because when the duty ratio is shifted to the increasing side, the current flowing into the first coil 1 increases exponentially, and then when the switching element 3 is turned off, a higher induction is generated in the first coil 1. As the voltage is generated, the capacitor 4 is sufficiently charged with a higher voltage, and the energy stored in the capacitor 4 for one period and discharged through the second coil 5 is larger, the both ends of the second coil 5 are It is considered that the effective value of the AC voltage generated at the output voltage increases, and the voltage across the output capacitor 7 obtained by half-wave rectifying the AC voltage with the diode 6, that is, the output voltage Vout increases.

  That is, the only way to increase the output voltage Vout is to increase the amount of charging current flowing through the capacitor 4 per cycle. For this purpose, since the capacitance of the capacitor 4 is constant, the voltage applied to the capacitor 4 via the first coil 1 can only be increased. For this purpose, it is necessary to slightly increase the duty ratio of the switching element 3.

  On the other hand, when the duty ratio is slightly reduced, the capacitor 4 is not sufficiently charged, and the energy moving from the primary side (left side in the figure) to the secondary side (right side in the figure) of the capacitor 4 decreases, resulting in the output voltage. Vout decreases, and finally becomes lower than the power supply voltage that becomes the input voltage Vin and is stepped down.

  In the present invention, the duty ratio at the boundary from the step-up to the step-down is referred to as a reference duty ratio. The reference duty ratio is set to 50% in this embodiment. When the duty ratio is less than 50%, the energy supplied from the primary side to the secondary side of the capacitor 4 is reduced, and as a result, the output voltage Vout is lowered, and finally becomes lower than the power supply voltage that becomes the input voltage Vin. Is done. When the duty ratio exceeds 50%, the energy supplied from the primary side to the secondary side of the capacitor 4 increases, and as a result, the output voltage Vout rises and is finally boosted to a level higher than the power supply voltage that becomes the input voltage Vin. The

If the capacitor 4 is not provided and the first coil 1 and the switching element 3 and the second coil 5 are directly connected, the resistance of the second coil 5 is small, so that a large current is switched off. Sometimes it flows through the first coil 1 and the second coil 5. Due to the presence of the capacitor 4, even if the resistance of the second coil 5 is small, the current flowing through the first coil 1 and the second coil 5 when the switching element 3 is off can be limited as the charging current of the capacitor 4. .
(Hypertensive action)
Next, in FIG. 1, the antihypertensive action will be further described. When the voltage of the power supply terminal 2 connected to the battery, that is, the input voltage Vin of the circuit of FIG. 1 exceeds 16 volts, the chopper IC 10 to which the monitor voltage Vm from the voltage dividing circuit 9 is input changes the duty ratio to a predetermined duty ratio. The switching element 3 is chopped to be less than (in this embodiment, the duty ratio is less than 50%). That is, the duty ratio is set lower than the reference duty ratio as a predetermined boundary value.

  The higher the input voltage Vin is 16 volts or higher, the more energy is supplied from the primary side to the secondary side of the capacitor 4 when compared at a constant duty ratio (50%). The monitor voltage Vm increases. The monitor voltage Vm is compared with the reference value Vb by the comparison circuit 10a in the chopper IC, and in proportion to the difference higher than the reference value Vb, the pulse generation circuit 10b has a duty of a pulse signal that becomes an output signal of the chopper IC10. Reduce the ratio.

As a result, the duty ratio of the switching element 3 driven by the pulse signal serving as the output of the chopper IC 10 also decreases in proportion to the above difference, and as a result, the output voltage Vout across the output-side capacitor 7 decreases and the voltage decreases. Operation is performed. Thereby, even if the power supply voltage jumps to, for example, 18 volts, a predetermined preferable output voltage Vout can be supplied by the step-down action.
(Pressurizing action)
Next, referring to FIG. 1, the boosting action will be described. When the power supply voltage from the battery, that is, the input voltage Vin applied to the power supply terminal 2 in FIG. 1 is 10 volts to less than 16 volts, the circuit in FIG. At this time, the chopper IC 10 to which the monitor voltage Vm from the voltage dividing circuit 9 is input sets the switching element 3 so that the duty ratio is equal to or higher than a predetermined reference duty ratio (in this embodiment, the duty ratio is 50% or higher). Control chopping. That is, the duty ratio is set higher than the reference duty ratio as a predetermined boundary value.

  When the switching element 3 is on, current starts to flow through the first coil 1. As is well known, this current gradually increases so as to have a time constant. When the duty ratio of the switching element 3 increases, the ON time of the switching element 3 per cycle increases. Therefore, the current flowing through the first coil 1 increases.

  In this way, by increasing the duty ratio of the switching element 3 and causing a large current to flow through the first coil 1, the voltage on the secondary side of the capacitor 4 increases. Specifically, the switching element 3 is turned on, sufficient electromagnetic energy is accumulated in the first coil 1, and a voltage of about 20V is applied to the output-side capacitor 7 via the diode 6 when the switching element 3 is turned off. Boost the pressure.

  The lower the input voltage Vin is below 16 volts, the less energy is transferred from the primary side to the secondary side of the capacitor 4 when compared with a constant duty ratio (50%). Vm decreases. The monitor voltage Vm is compared with the reference value Vb by the comparison circuit 10a in the chopper IC10. Assuming that the monitor voltage Vm is lower than the reference value Vb, the pulse generation circuit 10b is proportional to the low difference. Increase the duty ratio of the pulse signal that becomes the output signal.

  As a result, the duty ratio of the switching element 3 driven by the pulse signal serving as the output of the chopper IC 10 also increases according to the difference, and as a result, the output voltage Vout increases according to the difference, and the boosting operation is performed. As a result, even if the power supply voltage drops to, for example, about 10 volts, a predetermined preferable output voltage Vout of about 16 volts can be supplied by the boosting action.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and can be modified or expanded as follows. For example, in the first embodiment described above, the voltage dividing circuit 9 that monitors the output voltage Vout is connected to both ends of the output side capacitor 7, but may be connected to both ends of the second coil 5. However, in this case, a diode for rectifying and smoothing the monitor output and a smoothing capacitor are required in the chopper IC 10.

  The output voltage Vout is monitored and the step-down operation is performed by setting the duty ratio of the switching element 3 to be less than a predetermined reference duty ratio according to the magnitude of the output voltage Vout, or the output voltage Vout is monitored and the magnitude of the output voltage Vout In response to this, the chopper IC 10 switches whether the boosting action is performed with the duty ratio of the switching element 3 equal to or higher than a predetermined reference duty ratio. However, it is essential to set the reference duty ratio at the boundary of this switching to 50%. It is not, but it is chosen to this extent.

  The reference duty ratio at the boundary where the step-down action and the step-up action are reversed can be arbitrarily set according to the load specification and the voltage fluctuation range of the power source such as a battery. However, if the predetermined duty ratio is set to exceed 70%, there is no margin on the boost side, and it is difficult to satisfy the required specifications. Moreover, the loss in the switching element 3 also increases.

  Therefore, it is preferable that the reference duty ratio is between 30% and 70%. Further, although the output side capacitor 7 is provided on the load side for smoothing action, the output side capacitor 7 may be omitted if smoothing is not necessary, or a smoothing means such as a battery is provided on the load side. In some cases, it may be substituted. A smoothing capacitor may be provided in the load.

  Further, although the voltage dividing circuit 9 is used as the monitor circuit, other voltage detecting elements such as a thermistor may be provided as long as the voltage is detected. Moreover, the voltage regulator of this invention can be used not only for vehicles but for other uses. For example, the battery can be charged with a solar cell or used for a power supply device that rotates an electric fan for ventilation.

DESCRIPTION OF SYMBOLS 1 1st coil 2 Power supply terminal 3 Switching element 4 Capacitor 5 2nd coil 6 Diode 7 Output side capacitor 8 Load 9 Voltage divider circuit which makes a monitor circuit 10 Chopper IC which makes a chopper control circuit
Vin input voltage Vm Monitor voltage Vout Output voltage

Claims (6)

A voltage adjusting device for adjusting an input voltage and applying it to a load,
A first coil to which an input voltage is applied;
A switching element that causes a current to flow through the first coil by the input voltage in an on state;
A capacitor branched from between the first coil and the switching element, and charged via the first coil when the switching element is in an off state;
A second coil through which a discharge current of the capacitor flows when the switching element is on;
A diode that rectifies the voltage across the second coil and applies it to the load;
A monitor circuit for monitoring a voltage applied to the load between the second coil and the load; and a chopper control circuit for controlling a duty ratio at which the switching element is turned on / off according to a monitoring result by the monitor circuit. The voltage regulator characterized by the above-mentioned.   The chopper control circuit sets the duty ratio for turning on and off the switching element higher than a reference duty ratio when the value resulting from the monitoring is lower than a reference value, and the value resulting from the monitoring is greater than the reference value. 2. The voltage regulator according to claim 1, wherein the duty ratio at which the switching element is turned on / off at a higher value is made lower than the reference duty ratio.   3. The reference duty ratio is between 30% and 70% of the duty ratio, which is a ratio of time during which the switching element is turned on and off at a constant time period, and is turned on in one period. The voltage regulator described.   4. The voltage regulator according to claim 1, wherein an output side capacitor is provided in parallel with the load, and the output side capacitor is charged via the diode.   5. The voltage regulator according to claim 4, wherein the monitor circuit includes a voltage dividing circuit that detects a voltage across the output-side capacitor.   6. The voltage regulator according to claim 1, wherein the input voltage is a vehicle battery voltage, and the load is an electric load for display in an instrument panel of the vehicle.

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