JP2017158289A - Switching power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching power supply device capable of effectively detecting abnormalities within a specification range of an output voltage.SOLUTION: A switching power supply device comprises: a switching element; an oscillator that generates a clock signal; a feedback controller that performs switching control of the switching element on the basis of a feedback voltage based on an output voltage and the clock signal; a comparator that compares the feedback voltage with a predetermined reference voltage; and an abnormality detection unit that compares the number of pulses generated in a comparison signal outputted from the comparator with the number of pulses generated in the clock signal or a signal synchronized with the clock signal, and outputs a detection signal indicating whether or not the number of pulses is normal on the basis of the comparison result.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a switching power supply device.

  Conventionally, various switching power supply devices have been developed. Some of them detect an abnormality by detecting that the output voltage of the power supply device exceeds the upper limit of the specification or the lower limit of the specification.

  As an example of the related art related to the above, Patent Document 1 can be cited.

JP 2012-257444 A

  However, in a switching power supply device that detects an abnormality in which the output voltage exceeds the specification range as described above, for example, a spike voltage in which the output voltage fluctuates greatly in a short time within the specification range, or an output voltage that occurs within the specification range It was difficult to detect abnormalities within the specification range such as oscillation.

  For example, when the switching power supply is for in-vehicle use, in a situation where ISO 26262, which is an international standard for functional safety related to automobile electricity / electronics, has been formulated, safety is more important. There is a high demand for detecting anomalies that occur within the range.

  In view of the above situation, an object of the present invention is to provide a switching power supply device that can effectively detect an abnormality within a specification range of an output voltage.

In order to achieve the above object, a switching power supply device according to the present invention provides:
A switching element;
An oscillator that generates a clock signal;
A feedback control unit that controls switching of the switching element based on a feedback voltage based on an output voltage and the clock signal;
A comparator for comparing the feedback voltage with a predetermined reference voltage;
The number of pulses generated in the comparison signal output from the comparator is compared with the number of pulses generated in the clock signal or a signal synchronized with the clock signal, and a detection signal indicating whether the signal is normal or not is output based on the comparison result. And an abnormality detection unit (first configuration).

  In the first configuration, the abnormality detection unit includes a first count unit that counts the number of pulses generated in the comparison signal in a predetermined cycle, and a signal that is synchronized with the clock signal or the clock signal in the predetermined cycle. A second count unit that counts the number of pulses generated in the first count unit, and a first count value by the first count unit is larger than a second count value by the second count unit by a predetermined first threshold, or And a determination unit that determines that an abnormality has occurred and outputs the detection signal when the first count value is smaller than the second count value by a predetermined second threshold or more (the second count value). Constitution).

  In the second configuration, the abnormality detection unit may further include a register in which the first threshold, the second threshold, and the predetermined period can be set (third configuration).

  In any one of the first to third configurations, a ripple voltage whose voltage value fluctuates periodically based on a drive signal for switching driving the switching element output by the feedback control unit is used as the reference. It is good also as providing the ripple voltage generation part produced | generated as a voltage (4th structure).

  In the fourth configuration, the feedback control unit includes an error amplifier to which the feedback voltage and a reference voltage are input, and the ripple voltage generation unit is based on the drive signal and the reference voltage. A ripple voltage may be generated (fifth configuration).

  In any of the first to third configurations, the reference voltage may be a fixed reference voltage (sixth configuration).

  In any one of the first to sixth configurations, the signal synchronized with the clock signal may be a drive signal for switching driving the switching element output by the feedback control unit ( Seventh configuration).

  In any one of the first to seventh configurations, the abnormality detection unit may output the detection signal to an external microcomputer (eighth configuration).

  The switching power supply device having any one of the first to eighth configurations may be a step-down converter that further includes an inductor connected to the switching element (a ninth configuration).

  Moreover, it is preferable that the switching power supply device having any one of the first to ninth configurations is for vehicle use.

  According to the switching power supply device of the present invention, it is possible to effectively detect an abnormality within the specification range of the output voltage.

It is a figure which shows the structure of the switching power supply device which concerns on 1st Embodiment of this invention. It is a block diagram which shows one structural example of a logic part. It is a timing chart which shows the example of various signal waveforms in case an output voltage is a normal state. It is a timing chart which shows the example of various signal waveforms when the abnormal state where an output voltage raises arises. It is a timing chart which shows the example of various signal waveforms when the abnormal state where an output voltage raises arises. It is a timing chart which shows the example of various signal waveforms in the case of the abnormal condition which a spike voltage produces in an output voltage. It is a timing chart which shows the example of various signal waveforms when the abnormal state which an output voltage oscillates within a specification range arises. It is a figure which shows the structure of the switching power supply device which concerns on 2nd Embodiment of this invention. It is a figure which shows the structure of the switching power supply device which concerns on 3rd Embodiment of this invention. It is an external view which shows the example of 1 structure of the vehicle carrying a switching power supply device.

  An embodiment of the present invention will be described below with reference to the drawings.

<Configuration of switching power supply device>
FIG. 1 is a diagram showing a configuration of a switching power supply apparatus according to an embodiment (first embodiment) of the present invention. A switching power supply device 15 shown in FIG. 1 is a step-down DC / DC converter that steps down an input voltage Vin to generate an output voltage Vout and supplies the output voltage Vout to a load Z1.

  The switching power supply device 15 includes an upper switching element Q1, a lower switching element Q2, a coil L1 (inductor), a capacitor C1, a resistor R1, a resistor R2, an error amplifier 1, a slope voltage generating unit 2, a comparator 3, an oscillator 4, and an RS flip-flop. 5, a driver 6, a ripple voltage generation unit 7, a comparator 8, and a logic unit 9 (abnormality detection unit). In the configuration shown in FIG. 1, for example, a driver IC (semiconductor device) is formed by components other than the upper switching element Q1, the lower switching element Q2, the coil L1, the capacitor C1, the resistor R1, and the resistor R2, which are discrete elements. Is configured.

  An input voltage Vin is applied to the source of the upper switching element Q1 formed of a P-channel MOSFET (MOS field effect transistor). The drain of the upper switching element Q1 is connected to the drain of the lower switching element Q2 formed of an N-channel MOSFET, and the source of the lower switching element Q2 is connected to the ground terminal.

  A connection point P between the upper switching element Q1 and the lower switching element Q2 is connected to one end of the coil L1. The other end of the coil L1 is connected to the output terminal To together with one end of the capacitor C1. The other end of the capacitor C1 is connected to the ground terminal.

  The resistor R1 and the resistor R2 are connected in series between the output terminal To where the output voltage Vout is generated and the ground terminal. A feedback voltage FB generated by dividing the output voltage Vout by the resistors R 1 and R 2 is applied to the inverting input terminal (−) of the error amplifier 1. A reference voltage Vref1 is applied to the non-inverting input terminal (+) of the error amplifier 1.

  The error amplifier 1 amplifies the difference between the feedback voltage FB and the reference voltage Vref1, and generates an error voltage SE. The output terminal of the error amplifier 1 is connected to the inverting input terminal of the comparator 3.

  The slope voltage generator 2 generates and outputs a sawtooth wave or triangular wave slope voltage SLP. The slope voltage SLP is applied to the non-inverting input terminal of the comparator 3.

  The comparator 3 compares the error voltage SE with the slope voltage SLP, and outputs a comparison signal SC1 as a comparison result to the reset terminal of the RS flip-flop 5. The oscillator 4 generates a pulsed clock signal CLK having a predetermined frequency. The clock signal CLK is input to the set terminal of the RS flip-flop 5.

  The RS flip-flop 5 generates a pulse-like drive signal DRV_LGC based on the clock signal CLK and the comparison signal SC1 and outputs it to the driver 6. The driver 6 generates a gate signal G1 and a gate signal G2 based on the drive signal DRV_LGC, applies the gate signal G1 to the gate of the upper switching element Q1, and applies the gate signal G2 to the gate of the lower switching element Q2. .

  By the feedback control unit including the error amplifier 1, the slope voltage generation unit 2, the comparator 3, and the RS flip-flop 5 as described above, the upper switching element Q1 and the lower switching element Q2 are changed using the feedback voltage FB and the clock signal CLK. Feedback control for switching control is performed, and the output voltage Vout is controlled to be constant. That is, the on-duty of the drive signal DRV_LGC is adjusted by PWM (pulse width modulation) control.

  The switching power supply device 15 according to the present embodiment further includes a ripple voltage generation unit 7, a comparator 8, and a logic unit 9. The ripple voltage generation unit 7 includes an operational amplifier 71, a resistor 72, a resistor 73, and a capacitor 74. The reference voltage Vref1 for the error amplifier 1 is applied to the non-inverting input terminal (+) of the operational amplifier 71. One end of a resistor 72 is connected to the inverting input terminal (−) of the operational amplifier 71. The drive signal DRV_LGC is applied to the other end of the resistor 72. One end of a capacitor 74 and one end of a resistor 73 are further connected to the inverting input terminal of the operational amplifier 71. The output terminal of the operational amplifier 71 is connected to the other end of the capacitor 74 and the other end of the resistor 73.

  Resistor 72, resistor 73, and capacitor 74 pulse drive the negative feedback loop of operational amplifier 71 in accordance with drive signal DRV_LGC. As a result, the ripple voltage Vrp output from the operational amplifier 71 has a waveform in which the voltage value periodically varies with reference to the reference voltage Vref1 (see FIG. 3 and the like described later).

  The reference voltage applied to the operational amplifier 71 is not limited to the reference voltage Vref1 for the error amplifier 1, and may be a voltage obtained by shifting the reference voltage Vref1, for example.

  The ripple voltage Vrp output from the ripple voltage generator 7 is applied to the non-inverting input terminal of the comparator 8. A feedback voltage FB is applied to the inverting input terminal of the comparator 8. The comparator 8 compares the ripple voltage Vrp and the feedback voltage FB, and outputs a comparison signal SC2 as a comparison result.

  The logic unit 9 detects the state of the output voltage Vout based on the input clock signal CLK and the comparison signal SC2, and outputs a detection signal DET indicating whether or not the output voltage Vout is in a normal state. The detection signal DET can be notified to the microcomputer of the state of the output voltage Vout, for example, by transmitting the detection signal DET to the microcomputer outside the switching power supply device 15. In addition, when the switching power supply device 15 is for in-vehicle use, for example, the microcomputer can be included in an ECU (Engine Control Unit).

<Abnormality detection operation>
Next, the abnormality detection operation of the output voltage Vout in the switching power supply device 15 will be described using the timing charts of FIGS.

  FIG. 3 is a timing chart showing examples of various signal waveforms when the output voltage Vout is in a normal state. 3, the drive signal DRV_LGC, the feedback voltage FB (solid line), the ripple voltage Vrp (broken line), the clock signal CLK, and the comparison signal SC2 are shown in order from the top (the same applies to the other timing charts hereinafter). When the output voltage Vout is in a normal state, the feedback voltage FB also has a normal waveform.

  When the clock signal CLK rises to a high level, the RS flip-flop 5 is set and the drive signal DRV_LGC rises to a high level. Accordingly, the upper switching element Q1 is turned on by the gate signals G1 and G2, and the lower switching element Q2 is turned off. Then, a current flows from the application end of the input voltage Vin to the load Z1 via the upper switching element Q1 and the coil L1, and the output voltage Vout increases. That is, the feedback voltage FB also increases.

  The slope voltage SLP starts to rise by the slope voltage generator 2 at the rise of the clock signal CLK, and when the slope voltage SLP reaches the error voltage SE, the comparison signal SC1 rises from the Low level to the High level, and the RS flip-flop 5 Is reset. As a result, the drive signal DRV_LGC falls to the Low level, and the upper switching element Q1 is turned off and the lower switching element Q2 is turned on by the gate signals G1 and G2. That is, the ON period Ton of the upper switching element Q1 is adjusted by the error voltage SE and the slope voltage SLP.

  When the upper switching element Q1 is turned off, a current flows through the switching element Q2 and the coil L1, and the output voltage Vout decreases. Therefore, the feedback voltage FB also decreases. When the clock signal CLK rises to a high level, the RS flip-flop 5 is set and the drive signal DRV_LGC rises to a high level. The period from the falling edge to the rising edge of the drive signal DRV_LGC is the off period Toff of the upper switching element Q1.

  The ripple voltage Vrp decreases during the on period Ton when the drive signal DRV_LGC is at a high level, rises during the off period Toff when the drive signal DRV_LGC is at a low level, and the voltage value periodically varies according to the drive signal DRV_LGC. It becomes.

  Near the end timing of the off period Toff, the rising ripple voltage Vrp exceeds the decreasing feedback voltage FB, so that the comparison signal SC2 rises to a high level. Thereafter, in the vicinity of the start timing of the next ON period Ton, the decreasing ripple voltage Vrp falls below the rising feedback voltage FB, so that the comparison signal SC2 falls to the Low level. As a result, a pulse is generated in the comparison signal SC2 in the vicinity of the switching timing from the off period Toff to the on period Ton.

  In the example shown in FIG. 3, since the output voltage Vout is in a normal state, the pulses of the comparison signal SC2 are generated in one-to-one correspondence with the pulses of the clock signal CLK, and the number of both pulses is the same in a predetermined period. It has become.

  Next, FIG. 4 is a timing chart showing an example when an abnormality occurs in which the output voltage Vout rises in the middle. In FIG. 4, the feedback voltage FB rises during the period T1 due to the rise of the output voltage Vout. The feedback voltage FB is raised between the upper limit voltage Vlim1 and the lower limit voltage Vlim2 corresponding to the specification.

  In this case, since no pulse is generated in the comparison signal SC2 near the timing at which the pulses P1 and P2 are generated in the clock signal CLK, the number of pulses of the comparison signal SC2 is larger than the number of pulses of the clock signal CLK in a predetermined period. It is running low.

  Next, FIG. 5 is a timing chart showing an example when an abnormality occurs in which the output voltage Vout drops in the middle. In FIG. 5, due to the fall of the output voltage Vout, the fall of the feedback voltage FB occurs in the period T2. The feedback voltage FB is lowered between the upper limit voltage Vlim1 and the lower limit voltage Vlim2.

  In this case, the feedback voltage FB continues to fall below the ripple voltage Vrp after the ripple voltage Vrp exceeds the feedback voltage FB at the timing t1 and the comparison signal SC2 rises to the high level due to the fall of the feedback voltage FB. Maintains a high level. Accordingly, only one pulse is generated in the comparison signal SC2 with respect to the pulses P3 to P5 generated in the clock signal CLK, and the number of pulses of the comparison signal SC2 is smaller than the number of pulses of the clock signal CLK in a predetermined period. It has become.

  Next, FIG. 6 is a timing chart showing an example in the case where an abnormality that causes a spike voltage occurs in the output voltage Vout. Since the consumption current in the load Z1 increases rapidly, a spike voltage that increases after the voltage value decreases within a short time in the output voltage Vout is generated, so that the spike voltage Vsp1 and the spike voltage Vsp1 in the feedback voltage FB as shown in FIG. Vsp2 is generated. The spike voltages Vsp1 and Vps2 are generated between the upper limit voltage Vlim1 and the lower limit voltage Vlim2.

  In this case, pulses P6 and P7 are generated in the comparison signal SC2 according to the spike voltages Vsp1 and Vsp2, and the number of pulses of the comparison signal SC2 is larger than the number of pulses of the clock signal CLK in a predetermined period.

  Next, FIG. 7 is a timing chart showing an example in the case where an abnormality that causes oscillation within the specification range occurs in the output voltage Vout. As shown in FIG. 7, the feedback voltage FB oscillates at a period longer than the switching period. Oscillation occurs between the upper limit voltage Vlim1 and the lower limit voltage Vlim2.

  In this case, the comparison signal SC2 rises to a high level at timing t2 when the feedback voltage FB falls below the ripple voltage Vrp. Then, after the High level is maintained, the comparison signal SC2 falls to the Low level when the feedback voltage FB exceeds the ripple voltage Vrp at the timing t3. Accordingly, only one pulse is generated in the comparison signal SC2 with respect to the five pulses generated in the clock signal CLK shown in FIG. 7, and the number of pulses of the comparison signal SC2 is the number of pulses of the clock signal CLK in a predetermined period. Less than the number of

  From the above, when the output voltage Vout is abnormal, the difference between the number of pulses generated in the clock signal CLK and the number of pulses generated in the comparison signal SC2 is larger than in the normal state. It can be seen that an abnormal state can be detected by comparing the numbers.

  A logic unit 9 is provided to perform such a comparison process. FIG. 2 is a block diagram illustrating a configuration example of the logic unit 9. As illustrated in FIG. 2, the logic unit 9 includes a first count unit 91, a second count unit 92, a determination unit 93, and a register 94.

  The first count unit 91 counts the number of pulses generated in the comparison signal SC2, and outputs the first count value CT1 to the determination unit 93. The second count unit 92 counts the number of pulses generated in the clock signal CLK and outputs the second count value CT2 to the determination unit 93. The first count unit 91 and the second count unit 92 count the number of pulses in a predetermined period Ts (predetermined period) set in the register 94.

  The determination unit 93 compares the first count value CT1 and the second count value CT2, and if the first count value CT1 is greater than a predetermined first threshold value N1 or more than the CT2, or the first count value CT1 is CT2. It is determined that there is an abnormality in the output voltage Vout when it is smaller than the predetermined second threshold value N2 by more than the second threshold value N2, and it is determined that it is normal otherwise. The determination unit 93 outputs a detection signal DET according to the determination result.

  The first threshold value N1, the second threshold value N2, and the predetermined period Ts can be set in the register 94, respectively. Actually, there may be a slight difference in the number of pulses generated in the clock signal CLK and the comparison signal SC2 even when the output voltage Vout is in a normal state due to the fluctuation of the load current in the load Z1. Therefore, the first threshold value N1 and the second threshold value N2 are set to predetermined values larger than zero, respectively. The first threshold value N1, the second threshold value N2, and the predetermined period Ts are set in the register 94 according to the load current characteristic of the load Z1.

  As described above, according to the present embodiment, even when an abnormality occurs within the specification range of the output voltage Vout, the abnormality can be detected. Therefore, the switching power supply device 15 can be made more important in safety.

<Modification>
FIG. 8 is a diagram showing a configuration of the switching power supply device 20 according to the second embodiment of the present invention. The difference of the configuration of the switching power supply device 20 from the first embodiment (FIG. 1) is that the voltage applied to the non-reverse input terminal of the comparator 8 is not a ripple voltage but a reference voltage Vref2 that is a predetermined fixed voltage value. It is that you are.

  In the first embodiment using a ripple voltage, when the output voltage Vout is in a normal state, the feedback voltage FB has a waveform that protrudes upward, whereas the ripple voltage Vrp has a waveform that protrudes downward. Therefore, it is possible to prevent the feedback signal FB from being unnecessarily lower than the ripple voltage Vrp due to noise or the like and causing a pulse in the comparison signal SC2. However, if the feedback voltage FB has a waveform that protrudes significantly upward, even if the reference voltage Vref2 to be compared with the feedback voltage FB is a constant value as in the present embodiment, erroneous detection in the normal state is detected. Can be suppressed.

  Next, FIG. 9 is a diagram showing a configuration of the switching power supply device 25 according to the third embodiment of the present invention. The difference of the configuration of the switching power supply device 25 from the first embodiment (FIG. 1) is that the drive signal DRV_LGC is input to the logic unit 9 instead of the clock signal CLK.

  As shown in FIG. 3 and the like, since the drive signal DRV_LGC is generated one-to-one with the pulse of the clock signal CLK, the number of pulses generated in the comparison signal SC2 and the pulses generated in the drive signal DRV_LGC are generated in the logic unit 9. By comparing the number of output voltages, the abnormal state of the output voltage Vout can be detected as in the first embodiment.

<Application to vehicles>
FIG. 10 is an external view showing a configuration example of a vehicle on which the switching power supply device is mounted. The vehicle X of this configuration example includes a battery X10 and various electronic devices X11 to X18 that operate by receiving the input voltage Vin from the battery X10. In addition, about the mounting position of the battery X10 in FIG. 10, and the electronic devices X11-X18, it may differ from the actual for convenience of illustration.

  The electronic device X11 is an engine control unit that performs control related to the engine (such as injection control, electronic throttle control, idling control, oxygen sensor heater control, and auto cruise control).

  The electronic device X12 is a lamp control unit that performs on / off control such as HID [high intensity discharged lamp] and DRL [daytime running lamp].

  The electronic device X13 is a transmission control unit that performs control related to the transmission.

  The electronic device X14 is a body control unit that performs control (ABS [anti-lock brake system] control, EPS [electric power steering] control, electronic suspension control, etc.) related to the motion of the vehicle X.

  The electronic device X15 is a security control unit that performs drive control such as a door lock and a security alarm.

  The electronic device X16 is an electronic device that is incorporated in the vehicle X at the factory shipment stage as a standard equipment item or manufacturer's option product such as a wiper, an electric door mirror, a power window, a damper (shock absorber), an electric sunroof, and an electric seat. It is.

  The electronic device X17 is an electronic device that is optionally mounted on the vehicle X as a user option product such as an in-vehicle A / V [audio / visual] device, a car navigation system, and an ETC [electronic toll collection system].

  The electronic device X18 is an electronic device that includes a high-voltage motor such as an in-vehicle blower, an oil pump, a water pump, and a battery cooling fan.

  Note that the switching devices 15, 20, and 25 described above can be incorporated in any of the electronic devices X11 to X18 as power supply means to the load Z1. In particular, in order to satisfy the regulations such as ISO26262 relating to in-vehicle use, the function of detecting an abnormality in the output voltage within the specification range as in this embodiment is important.

<Others>
The configuration of the present invention can be variously modified in addition to the above-described embodiment without departing from the gist of the invention. That is, the above-described embodiment is an example in all respects and should not be considered as limiting, and the technical scope of the present invention is not the description of the above-described embodiment, but the claims. It should be understood that all modifications that come within the meaning and range of equivalents of the claims are included.

  For example, the present invention can also be applied to an asynchronous rectification step-down converter in which the lower switching element Q2 is a diode.

  The present invention can be used for a switching power supply device mounted on a vehicle, for example.

DESCRIPTION OF SYMBOLS 1 Error amplifier 2 Slope voltage generation part 3 Comparator 4 Oscillator 5 RS flip-flop 6 Driver 7 Ripple voltage generation part 71 Operational amplifier 72 Resistance 73 Resistance 74 Capacitor 8 Comparator 9 Logic part 91 1st count part 92 2nd count part 93 Determination part 94 Register 15, 20, 25 Switching power supply L1 Coil Q1 Upper switching element Q2 Lower switching element C1 Capacitor R1, R2 Resistance Z1 Load X Vehicle X10 Battery X11-X18 Electronic equipment

Claims (10)

A switching element;
An oscillator that generates a clock signal;
A feedback control unit that controls switching of the switching element based on a feedback voltage based on an output voltage and the clock signal;
A comparator for comparing the feedback voltage with a predetermined reference voltage;
The number of pulses generated in the comparison signal output from the comparator is compared with the number of pulses generated in the clock signal or a signal synchronized with the clock signal, and a detection signal indicating whether the signal is normal or not is output based on the comparison result. An anomaly detector,
A switching power supply device comprising: The abnormality detection unit
A first counting unit that counts the number of pulses generated in the comparison signal in a predetermined period;
A second count unit that counts the number of pulses generated in the clock signal or a signal synchronized with the clock signal in the predetermined period;
When the first count value by the first count unit is larger than the second count value by the second count unit by a predetermined first threshold value or when the first count value is by comparison with the second count value A determination unit that determines that an abnormality has occurred and outputs the detection signal when less than a predetermined second threshold;
The switching power supply device according to claim 1, comprising:   The switching power supply device according to claim 2, wherein the abnormality detection unit further includes a register in which the first threshold value, the second threshold value, and the predetermined period can be set.   And a ripple voltage generation unit that generates a ripple voltage whose voltage value periodically fluctuates as the reference voltage based on a drive signal for switching and driving the switching element output by the feedback control unit. The switching power supply device according to any one of claims 1 to 3. The feedback control unit has an error amplifier to which the feedback voltage and a reference voltage are input,
The switching power supply according to claim 4, wherein the ripple voltage generation unit generates the ripple voltage based on the drive signal and the reference voltage.   The switching power supply according to any one of claims 1 to 3, wherein the reference voltage is a fixed reference voltage.   7. The signal according to claim 1, wherein the signal synchronized with the clock signal is a drive signal for switching and driving the switching element output by the feedback control unit. Switching power supply.   The switching power supply according to any one of claims 1 to 7, wherein the abnormality detection unit outputs the detection signal to an external microcomputer.   The switching power supply according to any one of claims 1 to 8, wherein the switching power supply is a step-down converter further including an inductor connected to the switching element.   The switching power supply device according to any one of claims 1 to 9, wherein the switching power supply device is for in-vehicle use.

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