JP2017169378A - Switching power source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching power source device capable of detecting a semi-collapsed state of an inductor.SOLUTION: A switching power source device includes a switching element and an output stage including an inductor and a capacitor. The switching power source device includes: a feedback control unit that performs switching control of the switching element using a feedback voltage based on the output voltage, and a comparison unit that compares the difference between the average voltage of the pulsed switching voltages in which the approximately input voltage and the approximately ground potential are repeated by the switching of the switching element, and the output voltage with a predetermined threshold, and outputs a detection signal in accordance with 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, and some of them include an inductor (coil) and a capacitor in an output stage such as a step-down DC / DC converter.

  Conventionally, in the switching power supply as described above, when the inductor is completely destroyed and becomes open or short-circuited, this is detected and protected.

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

JP 2008-99518 A

  However, in the above conventional switching power supply device, it has been difficult to detect a half-destructed state of the inductor such that the ESR (Equivalent Series Resistance) of the inductor increases.

  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 electric / electronics of automobiles, has been established, in order to place more importance on safety, only complete destruction of elements can be achieved. In addition, it is desirable to be able to detect a semi-destructed state.

  In view of the above situation, an object of the present invention is to provide a switching power supply device that can detect a half-broken state of an inductor.

In order to achieve the above object, a switching power supply according to an aspect of the present invention is a switching power supply comprising a switching element and an output stage including an inductor and a capacitor,
A feedback control unit that performs switching control of the switching element using a feedback voltage based on an output voltage;
A comparison unit that compares a difference between an output voltage and an average voltage of a pulsed switching voltage that repeats a substantially input voltage and a substantially ground potential by switching of the switching element, and outputs a detection signal according to a comparison result (First configuration).

The first configuration further includes a low-pass filter that filters the switching voltage and outputs a filter output voltage,
The comparison unit may generate the detection signal based on the filter output voltage and the feedback voltage (second configuration).

  Further, in the second configuration, the comparison unit has a comparison target input voltage terminal to which a voltage based on the filter output voltage is applied, a lower limit voltage input terminal to which the feedback voltage is applied, and the feedback voltage as a predetermined value. A window comparator including an upper limit voltage input terminal to which a voltage increased by a voltage is applied may be included (third configuration).

In the first configuration, the low-pass filter that filters the drive signal output from the flip-flop included in the feedback voltage control unit and outputs the filter output voltage;
An amplifier that amplifies the filter output voltage at a predetermined amplification factor and outputs an amplified voltage; and
The comparison unit may generate the detection signal based on the amplified voltage and the feedback voltage (fourth configuration).

The feedback voltage control unit includes a flip-flop that generates a drive signal and a driver that generates a control signal to be applied to a control terminal of the switching element based on the drive signal. A power supply unit,
A level conversion unit that generates a conversion signal obtained by inverting the High level and the Low level of the control signal;
A low-pass filter that filters the converted signal and outputs a filter output voltage;
An amplifier that amplifies the filter output voltage at a predetermined amplification factor and outputs an amplified voltage; and
The comparison unit may generate the detection signal based on the amplified voltage and the feedback voltage (fifth configuration).

  In the fourth or fifth configuration, the comparison unit includes a comparison target input voltage terminal to which a voltage based on the amplified voltage is applied, a lower limit voltage input terminal to which the feedback voltage is applied, and the feedback voltage. It is also possible to have a window comparator including an upper limit voltage input terminal to which a voltage obtained by increasing the voltage by a predetermined voltage is applied (sixth configuration).

  In any of the fourth to sixth configurations, the amplification factor may be variable according to the input voltage. (Seventh configuration)

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

  In any one of the first to eighth configurations, the feedback control unit may perform feedback control by PWM control (9th configuration).

  In any one of the first to ninth configurations, a semiconductor device configured by integrating the feedback control unit and the comparison unit may be further provided (tenth configuration).

  Moreover, the vehicle-mounted electronic device which concerns on another aspect of this invention is supposed to be provided with the switching power supply device of the structure in any one of the said 1st-10th.

  According to the present invention, it is possible to detect a half-broken state of the inductor.

1 is an overall configuration diagram of a switching power supply device according to a first embodiment of the present invention. It is a figure which shows the example of 1 structure of a comparison part. It is a wave form diagram for demonstrating the behavior of the switching voltage when a coil is half-broken. It is a wave form diagram for demonstrating the behavior of the switching voltage when an upper side switching element is half-broken. It is a whole block diagram of the switching power supply device which concerns on 2nd Embodiment of this invention. It is a whole block diagram of the switching power supply device which concerns on 3rd Embodiment of this invention. It is a whole block diagram of the switching power supply device which concerns on 4th Embodiment of this invention. It is an external view which shows an example of the vehicle by which a vehicle-mounted electronic device is mounted.

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

<First Embodiment>
FIG. 1 is a diagram showing an overall configuration of a switching power supply apparatus according to the 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 a semiconductor device 10, a coil (inductor) L1, a capacitor C1, a resistor R1, and a resistor R2.

  The semiconductor device 10 includes an error amplifier 1, a slope voltage generation unit 2, a comparator 3, an oscillator 4, an RS flip-flop 5, a driver 6, a filter 7, a comparison unit 8, an upper switching element Q1, This is an IC in which the lower switching element Q2 is integrated. An output stage is constituted by the coil L1, the capacitor C1, the resistor R1, and the resistor R2, which are discrete elements.

  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. . The gate signals G1 and G2 are both pulse signals.

  By the feedback control unit including the error amplifier 1, the slope voltage generation unit 2, the comparator 3, the RS flip-flop 5, and the driver 6 as described above, the upper switching element Q1 and the lower switching are performed using the feedback voltage FB and the clock signal CLK. Feedback control for switching the element Q2 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.

  Here, the switching voltage SW generated at the connection point P between the upper switching element Q1 and the lower switching element Q2 is substantially equal to the input voltage Vin because the upper switching element Q1 and the lower switching element Q2 are switched complementarily. It has a pulse-like waveform in which a certain high level and a low level that is substantially the ground potential are repeated.

The relationship between the switching voltage SW and the output voltage Vout is expressed by the following equation (1) based on the voltage drop due to the ESR of the coil L1.
Vav−ESR × Iout = Vout (1)
Where Vav: average voltage of switching voltage SW, ESR: ESR of coil L1, Iout: output current flowing through load Z1

  Here, Vav = Vin × Duty (Duty: PWM on-duty). An example of the waveform of the switching voltage SW when the coil L1 is normal is shown in the upper part of FIG. In this case, since ESR is a small value, the duty (that is, the pulse width of the switching voltage SW) becomes small. At this time, ΔV which is the difference between Vav and Vout, that is, the value of ESR × Iout becomes small. For example, if ESR is 5 mΩ and Iout is 1 A, ΔV = 5 mV.

  In contrast, a waveform example of the switching voltage SW when the coil L1 is partially broken is shown in the lower part of FIG. When the coil L1 is partially broken toward the open state, the ESR increases. Then, the duty (that is, the pulse width of the switching voltage SW) increases due to normal regulation that maintains the output voltage Vout constant by feedback control. At this time, the value of ESR × Iout, that is, ΔV increases, and the difference between Vav and Vout increases. For example, if ESR increases to 5Ω and Iout is 1A, ΔV = 5V.

  Therefore, it is possible to detect the half-broken state of the coil L1 based on the magnitude of ΔV that is the difference between the average voltage Vav of the switching voltage SW and the output voltage Vout. In order to detect the half-break of the coil L1 based on such a principle, the switching power supply device 15 is provided with a filter 7 and a comparison unit 8.

  The filter 7 is a low-pass filter configured by, for example, an RC circuit, and filters the input switching voltage SW to output the filter output voltage Vf to the comparison unit 8. The filter output voltage Vf corresponds to the average voltage Vav of the switching voltage SW.

  The comparator 8 receives the filter output voltage Vf and the feedback voltage FB. FIG. 2 is a diagram illustrating a configuration example of the comparison unit 8. The comparison unit 8 illustrated in FIG. 2 includes a constant voltage source 801, a window comparator 802, an inverter 803, and voltage dividing resistors R81 and R82.

  The filter output voltage Vf is divided by resistors R81 and R82, and the divided voltage Vfr is applied to the comparison target voltage input terminal vin of the window comparator 802. The feedback voltage FB is applied to the lower limit voltage input terminal vl of the window comparator 802. A voltage FBU whose level is increased by the amount of voltage generated in the constant voltage source 801 by the feedback voltage FB is applied to the upper limit voltage input terminal vu of the window comparator 802.

  The window comparator 802 is a circuit that compares the voltage applied to the comparison target voltage input terminal vin with the upper limit voltage and the lower limit voltage. When the voltage Vfr has a relationship of FB <Vfr <FBU, the comparison signal is at a high level. Cp is output, otherwise, the comparison signal Cp at the low level is output. The inverter 803 inverts the comparison signal Cp and outputs it as the detection signal DET. The detection signal DET is output to the host computer 20 disposed outside the switching power supply device 15 (FIG. 1).

Here, when the coil L1 is normal, ΔV = Vav−Vout satisfies the following expression (2).
0 <Vav−Vout <ΔVth (2)
However, ΔVth is a predetermined threshold value.

Assuming that the voltage dividing ratio by the resistors R1 and R2 and the voltage dividing ratio by the resistors R81 and R82 are the same voltage dividing ratio α, the expression (2) is rewritten as the following expression (3).
0 <Vav · α−Vout · α <ΔVth · α (3)

  The above equation (3) indicates that Vav · α> Vout · α and Vav · α <Vout · α + ΔVth · α.

  The filter output voltage Vf corresponds to Vav, and Vout · α is the feedback voltage FB. Therefore, when the coil L1 is normal, Vfr> FB and Vfr <FB + ΔVth · α are satisfied. If ΔVth · α is set to the voltage generated in the constant voltage source 801, Vfr> FB and Vfr <FBU are satisfied. Become. At this time, the window comparator 802 outputs a comparison signal Cp having a high level.

On the other hand, when coil L1 is partially broken and ESR increases, ΔV = Vav−Vout satisfies the following expression (4).
Vav−Vout ≧ ΔVth (4)

Equation (4) can be rewritten as the following equation (5).
Vav · α−Vout · α ≧ ΔVth · α (5)

  Therefore, when the coil L1 is partially broken, Vfr ≧ FBU is satisfied, and the window comparator 802 outputs the comparison signal Cp at the low level.

  From the above, when the coil L1 is normal, the detection signal DET is at a low level, and when the coil L1 is in a half-broken state, the detection signal DET is at a high level. In this way, it is possible to detect whether the coil L1 is normal or partially broken by the detection signal DET.

  When the coil L1 is partially broken, it can be notified to the host computer 20 by the detection signal DET. At this time, the host computer 20 can stop the switching of the upper switching element Q1 and the lower switching element Q2 by performing control to invalidate the enable signal of the switching power supply device 15, for example. As a result, it is possible to prevent abnormal heat generation in the coil L1 due to an increase in ESR due to the partial destruction of the coil L1. The control for stopping the switching may be performed inside the semiconductor device 10 without using the host computer 20.

  Further, according to the present embodiment, the filter 7 and the comparison unit 8 are provided inside the semiconductor device 10, so that it is possible to detect the half-break of the coil L <b> 1, and there is no need to add components outside the semiconductor device 10.

  Further, according to the present embodiment, when the capacitor C1 is short-circuited due to destruction, the output voltage Vout decreases and the difference between the average voltage Vav of the switching voltage SW and the output voltage Vout increases. Like the half destruction, the destruction of the capacitor C1 can be detected by the detection signal DET.

Second Embodiment
Next, a second embodiment of the present invention will be described. FIG. 5 is a diagram showing an overall configuration of a switching power supply apparatus 152 according to the second embodiment of the present invention. The difference of the configuration of the switching power supply device 152 from the first embodiment (FIG. 1) is that a filter 72 to which the drive signal DRV_LGC that is an output of the RS flip-flop 5 is input instead of the switching voltage SW, an amplifier 92, The comparison unit 82 is provided in the semiconductor device 102.

  The filter 72 is a low-pass filter that outputs a filter output voltage Vf by filtering the input drive signal DRV_LGC. The amplifier 92 amplifies the filter output voltage Vf with a predetermined amplification factor, and outputs the amplified voltage Vfa after amplification to the comparison unit 82.

  The comparison unit 82 receives the amplified voltage Vfa and the feedback voltage FB. The configuration of the comparison unit 82 is the same as that shown in FIG. 2. In the comparison unit 82, not the filter output voltage Vf but the amplified voltage Vfa is divided by the resistors R 81 and R 82.

Here, the relationship between the pulsed drive signal DRV_LGC and the average voltage Vav of the switching voltage SW is expressed by the following equation.
Vav = Adrv × Duty × (Vin / Adrv) (6)
Where Adrv: amplitude of drive signal DRV_LGC

  In the above equation (6), Adrv × Duty corresponds to the filter output voltage Vf that is the output of the filter 72. When the amplification factor of the amplifier 92 is set to the value of (Vin / Adrv) in the above equation (6), the amplified voltage Vfa = Vav which is the output of the amplifier 92 is obtained, and Vav is input to the comparison unit 82. As a result, the configuration is the same as that of the first embodiment. Therefore, according to the present embodiment, it is possible to detect the half-breakage of the coil L1 by the detection signal DET as in the first embodiment. As in the first embodiment, not only the coil L1 is partially destroyed but also a short circuit of the capacitor C1 can be detected by the detection signal DET.

  In the present embodiment, when the upper switching element Q1 is partially destroyed, the High level side of the switching voltage SW may be smaller than the input voltage Vin. An example of this state is shown in the lower part of FIG. 4 (the upper part is a normal state). In this case, the PWM on-duty duty is controlled to be larger than that in the normal state so as to maintain the output voltage Vout constant by feedback control.

  Therefore, when the upper switching element Q1 is partially destroyed, the amplified voltage Vfa that is the output of the amplifier 92 becomes higher than that in the normal state, so that the comparison signal Cp output from the window comparator 802 becomes the Low level, and the detection signal DET Becomes High level. Thus, according to the present embodiment, not only the coil L1 is partially broken but also the upper switching element Q1 is partially broken.

  The amplification factor in the amplifier 92 may be a fixed value, that is, the value of (Vin / Adrv) may be a fixed value, and the input voltage Vin may fluctuate, so that the amplification factor may be variable according to the input voltage Vin. Good.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. FIG. 6 is a diagram showing an overall configuration of a switching power supply device 153 according to the third embodiment of the present invention. The difference of the configuration of the switching power supply device 153 from the second embodiment (FIG. 5) is that the level converter 13 to which the gate signal G1 applied to the gate of the upper switching element Q1 is input, the filter 73, and the amplifier 93 and the comparison unit 83 are provided in the semiconductor device 103.

  The gate signal G1 is a pulse-like signal that is at a low level when the upper switching element Q1 is on and is at a high level when the upper switching element Q1 is off. The level converter 13 generates and outputs a pulsed conversion signal Glt obtained by inverting the High level and Low level of the gate signal G1.

  The filter 73 is a low-pass filter that outputs a filter output voltage Vf by filtering the input conversion signal Glt. The amplifier 93 amplifies the filter output voltage Vf with a predetermined amplification factor, and outputs the amplified voltage Vfa after amplification to the comparison unit 83.

  The comparison unit 83 receives the amplified voltage Vfa and the feedback voltage FB. The configuration of the comparison unit 83 is the same as the configuration shown in FIG. 2. In the comparison unit 83, not the filter output voltage Vf but the amplified voltage Vfa is divided by the resistors R 81 and R 82.

When the amplification factor of the amplifier 93 is set to a ratio between the input voltage Vin and the amplitude of the conversion signal Glt, the amplified voltage Vfa that is the output of the amplifier 93 is expressed by the following equation.
Vfa = Aglt × Duty × (Vin / Aglt) (7)
Where Aglt: amplitude of the conversion signal Glt

  Therefore, the amplified voltage Vfa corresponds to the average voltage Vav of the switching voltage SW, and as a result, the present embodiment has a configuration equivalent to that of the first embodiment. Therefore, according to the present embodiment, it is possible to detect the half-break of the coil L1 by the detection signal DET as in the first embodiment. Further, according to the present embodiment, as in the second embodiment, it is possible to detect not only the half destruction of the coil L1 but also the short circuit of the capacitor C1 and the half destruction of the upper switching element Q1.

<Fourth embodiment>
Next, a fourth embodiment of the present invention will be described. FIG. 7 is a diagram showing an overall configuration of a switching power supply device 154 according to the fourth embodiment of the present invention. In the switching power supply device 154, the level conversion unit 14, the filter 74, the amplifier 94, and the comparison unit 84 are provided in the semiconductor device 104.

  The level conversion unit 14 receives a gate signal G2 applied to the gate of the lower switching element Q2. The gate signal G2 is a pulse-like signal that is at a low level when the upper switching element Q1 is on and is at a high level when the upper switching element Q1 is off. The level conversion unit 14 generates and outputs a pulsed conversion signal Glt obtained by inverting the High level and Low level of the gate signal G2.

  In the present embodiment, based on the same principle as in the third embodiment, the amplified voltage Vfa that is the output of the amplifier 94 corresponds to the average voltage Vav of the switching voltage SW. As a result, the configuration is the same as that in the first embodiment. Become. Therefore, according to the present embodiment, it is possible to detect the half-breakage of the coil L1 by the detection signal DET as in the first embodiment. Further, according to the present embodiment, as in the second embodiment, it is possible to detect not only the half destruction of the coil L1 but also the short circuit of the capacitor C1 and the half destruction of the upper switching element Q1.

<Application to vehicles>
FIG. 8 is an external view showing a configuration example of a vehicle equipped with a switching power supply device. 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. 8, 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 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.

  The switching devices 15 and 152 to 154 described above can be incorporated in any of the electronic devices X11 to X18 as power supply means for the load Z1. In particular, in order to satisfy the regulations such as ISO26262 relating to in-vehicle use, the function of detecting the half-destructed state of the element 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, although the switching power supply device by PWM control has been described in the above embodiment, the present invention is not limited to this, and the present invention may be applied to a switching power supply device by PFM (Pulse Frequency Modulation) control or the like.

  The present invention can also be applied to an asynchronous rectification step-down converter using the lower switching element Q2 as a diode.

  The present invention can be used, for example, in an in-vehicle switching power supply device.

DESCRIPTION OF SYMBOLS 1 Error amplifier 2 Slope voltage generation part 3 Comparator 4 Oscillator 5 RS flip-flop 6 Driver 7, 72, 73, 74 Filter 8 Comparison part 801 Constant voltage source 802 Window comparator 82, 83, 84 Comparison part 803 Inverter 92, 93, 94 Amplifier 10, 102, 103, 104 Semiconductor device 13, 14 Level converter 15, 152, 153, 154 Switching power supply device 20 Host computer L1 Coil C1 Capacitor R1, R2, R81, R82 Resistance Z1 Load X Vehicle X10 Battery X11-X18 Electronics

Claims (11)

A switching power supply device comprising a switching element and an output stage including an inductor and a capacitor,
A feedback control unit that performs switching control of the switching element using a feedback voltage based on an output voltage;
A comparison unit that compares a difference between an output voltage and an average voltage of a pulsed switching voltage that repeats a substantially input voltage and a substantially ground potential by switching of the switching element, and outputs a detection signal according to a comparison result When,
A switching power supply device comprising: A low-pass filter that filters the switching voltage and outputs a filter output voltage;
The switching power supply apparatus according to claim 1, wherein the comparison unit generates the detection signal based on the filter output voltage and the feedback voltage.   The comparison unit is applied with a comparison target input voltage terminal to which a voltage based on the filter output voltage is applied, a lower limit voltage input terminal to which the feedback voltage is applied, and a voltage obtained by increasing the feedback voltage by a predetermined voltage. The switching power supply according to claim 2, further comprising a window comparator including an upper limit voltage input terminal. A low-pass filter that outputs a filter output voltage by filtering a drive signal output from a flip-flop included in the feedback voltage control unit;
An amplifier that amplifies the filter output voltage at a predetermined amplification factor and outputs an amplified voltage; and
The switching power supply device according to claim 1, wherein the comparison unit generates the detection signal based on the amplified voltage and the feedback voltage. 2. The switching power supply device according to claim 1, wherein the feedback voltage control unit includes a flip-flop that generates a drive signal, and a driver that generates a control signal to be applied to a control terminal of the switching element based on the drive signal. Because
A level conversion unit that generates a conversion signal obtained by inverting the High level and the Low level of the control signal;
A low-pass filter that filters the converted signal and outputs a filter output voltage;
An amplifier that amplifies the filter output voltage at a predetermined amplification factor and outputs an amplified voltage; and
The switching power supply apparatus according to claim 1, wherein the comparison unit generates the detection signal based on the amplified voltage and the feedback voltage.   The comparison unit receives a comparison target input voltage terminal to which a voltage based on the amplified voltage is applied, a lower limit voltage input terminal to which the feedback voltage is applied, and a voltage obtained by increasing the feedback voltage by a predetermined voltage. 6. The switching power supply device according to claim 4, further comprising a window comparator including an upper limit voltage input terminal.   The switching power supply according to any one of claims 4 to 6, wherein the amplification factor is variable according to the input voltage.   The switching power supply according to any one of claims 1 to 7, wherein the comparison unit outputs the detection signal to an external host computer.   The switching power supply according to any one of claims 1 to 8, wherein the feedback control unit performs feedback control by PWM control.   The switching power supply device according to any one of claims 1 to 9, further comprising a semiconductor device configured by integrating the feedback control unit and the comparison unit.   An in-vehicle electronic device comprising the switching power supply device according to any one of claims 1 to 10.

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