JP6681232B2 - Switching power supply - Google Patents

Description

  The present invention relates to a switching power supply device.

  Conventionally, various switching power supply devices have been developed, and among them, there are some which are provided with an inductor (coil) and a capacitor in an output stage, such as a step-down DC / DC converter.

  Conventionally, in the switching power supply device as described above, when the inductor is completely destroyed and becomes open or short-circuited, there is one that detects and protects it.

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

JP, 2008-99518, A

  However, in the conventional switching power supply device described above, it is difficult to detect a semi-destroyed state of the inductor in which the ESR (Equivalent Series Resistance) of the inductor increases.

  For example, when the switching power supply is for a vehicle, in a situation where ISO26262, which is an international standard for functional safety related to electric / electronics of automobiles, is also established, in order to put more importance on safety, it is necessary to completely destroy the element. In addition, it is desirable to be able to detect a semi-damaged state.

  In view of the above situation, an object of the present invention is to provide a switching power supply device capable of detecting a semi-destructed state of an inductor.

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

Further, in the above-mentioned first configuration, a low-pass filter for filtering the switching voltage and outputting a filter output voltage is further provided.
The comparison unit may generate the detection signal based on the filter output voltage and the feedback voltage (second configuration).

  In the second configuration, the comparison unit sets the 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 to a predetermined value. A window comparator including an upper limit voltage input terminal to which a voltage increased by the voltage is applied may be provided (third configuration).

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

Further, the feedback voltage control unit includes the flip-flop that generates a drive signal, and the driver that generates a control signal to be applied to the control end of the switching element based on the drive signal. Power supply,
A level conversion unit that generates a conversion signal by inverting the High level and the Low level of the control signal;
A low-pass filter for filtering the converted signal and outputting a filter output voltage,
An amplifier that amplifies the filter output voltage at a predetermined amplification factor and outputs an amplified voltage,
The comparison section 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. May have a window comparator including an upper limit voltage input terminal to which a voltage increased by a predetermined voltage is applied (sixth configuration).

  Further, 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 section may output the detection signal to an external host computer (eighth configuration).

  Further, in any one of the first to eighth configurations, the feedback control unit may perform feedback control by PWM control (ninth configuration).

  Further, 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 (a tenth configuration).

  An on-vehicle electronic device according to another aspect of the present invention includes the switching power supply device having any one of the first to tenth configurations.

  According to the present invention, it is possible to detect a semi-damaged 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 one structural example of a comparison part. It is a waveform diagram for explaining the behavior of the switching voltage when the coil is partially broken. It is a waveform diagram for explaining the behavior of the switching voltage when the upper switching element is partially destroyed. 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 in which the 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 device according to a first embodiment of the present invention. The 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 the 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, The lower switching element Q2 is an integrated IC. An output stage is composed of the coil L1, which is a discrete element, the capacitor C1, the resistor R1, and the resistor R2.

  The 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 composed 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 end.

  The resistor R1 and the resistor R2 are connected in series between the output terminal To that produces the output voltage Vout and the ground terminal. The feedback voltage FB generated by dividing the output voltage Vout by the resistors R1 and R2 is applied to the inverting input terminal (−) of the error amplifier 1. The 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 to generate the 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 the comparison signal SC1 as the 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 pulsed 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 the gate signal G1 and the 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 pulsed signals.

  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 uses the feedback voltage FB and the clock signal CLK to perform the upper switching element Q1 and the lower switching. Feedback control for switching control of the element Q2 is performed, and the output voltage Vout is controlled to be constant. That is, the drive signal DRV_LGC has an on-duty 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 almost equal to the input voltage Vin because the upper switching element Q1 and the lower switching element Q2 are complementarily switched. It has a pulse-like waveform in which a certain High level and a Low level, which is almost 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)
However, 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 the ESR is a small value, the duty (that is, the pulse width of the switching voltage SW) is small. At this time, the difference ΔV between Vav and Vout, that is, the value of ESR × Iout becomes small. For example, assuming that ESR is 5 mΩ and Iout is 1 A, ΔV = 5 mV.

  On the other hand, a waveform example of the switching voltage SW when the coil L1 is half broken is shown in the lower part of FIG. When the coil L1 is semi-destructed toward the open state, the ESR increases. Then, the duty (that is, the pulse width of the switching voltage SW) increases due to the normal regulation that maintains the output voltage Vout constant by the 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 1 A, ΔV = 5V.

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

  The filter 7 is, for example, a low-pass filter configured by an RC circuit, filters the input switching voltage SW, and outputs 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 filter output voltage Vf and the feedback voltage FB are input to the comparison unit 8. 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 resistors R81 and R82 for voltage division.

  The filter output voltage Vf is divided by the 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. The voltage FBU in which the level of the feedback voltage FB is raised by the voltage generated in the constant voltage source 801, 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, and is a high level comparison signal when the voltage Vfr has a relationship of FB <Vfr <FBU. Cp is output, and otherwise, the comparison signal Cp that is 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 arranged 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

If the voltage division ratio by the resistors R1 and R2 and the voltage division ratio by the resistors R81 and R82 are the same voltage division ratio α, the equation (2) can be rewritten as the following equation (3).
0 <Vav · α-Vout · α <ΔVth · α (3)

  The above equation (3) shows 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, and if ΔVth · α is set to the voltage generated in the constant voltage source 801, then Vfr> FB and Vfr <FBU. Become. At this time, the window comparator 802 outputs the high-level comparison signal Cp.

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

The 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 low-level comparison signal Cp.

  From the above, the detection signal DET becomes Low level when the coil L1 is normal, and becomes High level when the coil L1 is in a partially destroyed state. 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, the detection signal DET can inform the host computer 20 to that effect. At this time, the host computer 20 can stop the switching of the upper switching element Q1 and the lower switching element Q2, for example, by performing control to invalidate the enable signal of the switching power supply device 15. As a result, it is possible to prevent abnormal heat generation in the coil L1 due to an increase in ESR due to the coil L1 being partially destroyed. The control for stopping the switching may be performed inside the semiconductor device 10 without passing through the host computer 20.

  Further, according to the present embodiment, by providing the filter 7 and the comparison unit 8 inside the semiconductor device 10, it is possible to detect the half-damage of the coil L1, and it is not necessary to add a component 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, so that the coil L1 has a large deviation. The destruction of the capacitor C1 can be detected by the detection signal DET in the same manner as the half destruction.

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

  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 amplified voltage Vfa to the comparison unit 82.

  The amplified voltage Vfa and the feedback voltage FB are input to the comparison unit 82. The configuration itself of the comparison unit 82 is similar to the configuration shown in FIG. 2, and in the comparison unit 82, not the filter output voltage Vf but the amplified voltage Vfa is divided by the resistors R81 and R82.

Here, the relationship between the pulsed drive signal DRV_LGC and the average voltage Vav of the switching voltage SW is as follows.
Vav = Adrv × Duty × (Vin / Adrv) (6)
However, Adrv: amplitude of drive signal DRV_LGC

  In the equation (6), Adrv × Duty corresponds to the filter output voltage Vf which is the output of the filter 72. Then, if 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 becomes, and Vav is input to the comparison unit 82. As a result, the configuration is equivalent to that of the first embodiment. Therefore, according to the present embodiment as well, it is possible to detect the semi-destruction of the coil L1 by the detection signal DET as in the first embodiment. Further, similar to the first embodiment, not only the coil L1 is half broken but also the short circuit of the capacitor C1 can be detected by the detection signal DET.

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

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

  Note that the amplification factor of the amplifier 92 may be a fixed value, that is, the value of (Vin / Adrv) may be a fixed value, or the input voltage Vin may fluctuate. Therefore, 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 configuration of the switching power supply device 153 differs from that of the second embodiment (FIG. 5) in that the level conversion unit 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 which becomes Low level when the upper switching element Q1 is on and becomes High level when the upper switching element Q1 is off. The level conversion unit 13 generates and outputs a pulsed conversion signal Glt which is the inversion of the High level and the 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 at a predetermined amplification factor and outputs the amplified amplified voltage Vfa to the comparison unit 83.

  The amplified voltage Vfa and the feedback voltage FB are input to the comparison unit 83. The configuration itself of the comparison unit 83 is the same as the configuration shown in FIG. 2. In the comparison unit 83, the amplified voltage Vfa, not the filter output voltage Vf, is divided by the resistors R81 and R82.

If the amplification factor of the amplifier 93 is set to the ratio of the input voltage Vin and the amplitude of the converted signal Glt, the amplified voltage Vfa output from the amplifier 93 is given by the following equation.
Vfa = Aglt × Duty × (Vin / Aglt) (7)
However, Aglt: amplitude of the converted 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 the same configuration as that of the first embodiment. Therefore, according to the present embodiment as well, it is possible to detect the half-damage of the coil L1 by the detection signal DET, as in the first embodiment. Further, according to the present embodiment, similarly to the second embodiment, not only the coil L1 being partially destroyed but also the short circuit of the capacitor C1 and the upper switching element Q1 can be detected.

<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 gate signal G2 applied to the gate of the lower switching element Q2 is input to the level conversion unit 14. The gate signal G2 is a pulse-like signal which becomes Low level when the upper switching element Q1 is on and becomes High level when the upper switching element Q1 is off. The level conversion unit 14 generates and outputs a pulse-shaped conversion signal Glt which is the inversion of the High level and the Low level of the gate signal G2.

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

<Application to vehicle>
FIG. 8 is an external view showing a configuration example of a vehicle equipped with the switching power supply device. The vehicle X of the present configuration example is equipped with a battery X10 and various electronic devices X11 to X18 that operate by receiving the supply of the input voltage Vin from the battery X10. Note that the mounting positions of the battery X10 and the electronic devices X11 to X18 in FIG. 8 may be different from the actual positions for convenience of illustration.

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

  The electronic device X12 is a lamp control unit that performs lighting 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 related to the motion of the vehicle X (ABS [anti-lock brake system] control, EPS [electric power steering] control, electronic suspension control, and the like).

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

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

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

  The electronic device X18 is an electronic device equipped with a high withstand 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 a power supply unit to the load Z1. In particular, in order to meet the requirements of ISO26262 related to mounting on a vehicle, the function of detecting the semi-destructed state of the element as in this embodiment is important.

<Other>
In addition to the above-described embodiment, the configuration of the present invention can be modified in various ways without departing from the spirit of the invention. That is, the above-mentioned embodiments are exemplifications in all respects, and should be considered not to be restrictive, and the technical scope of the present invention is not the description of the above-mentioned embodiments but the claims. It is to be understood that it is to be understood that it is intended to include all changes which come within the meaning and range of equivalency and scope of the claims.

  For example, although the switching power supply device by PWM control is 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 type step-down converter using the lower switching element Q2 as a diode.

  INDUSTRIAL APPLICABILITY The present invention can be applied to, for example, a vehicle-mounted switching power supply device.

1 Error Amplifier 2 Slope Voltage Generation Section 3 Comparator 4 Oscillator 5 RS Flip-Flop 6 Driver 7, 72, 73, 74 Filter 8 Comparison Section 801 Constant Voltage Source 802 Window Comparator 82, 83, 84 Comparison Section 803 Inverter 92, 93, 94 Amplifiers 10, 102, 103, 104 Semiconductor device 13, 14 Level converter 15, 152, 153, 154 Switching power supply device 20 Host computer L1 Coil C1 Capacitors R1, R2, R81, R82 Resistance Z1 Load X Vehicle X10 Battery X11 to 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 controls switching of the switching element using a feedback voltage based on the output voltage,
A comparison unit that compares the difference between the average voltage of the pulsed switching voltage that repeats substantially the input voltage and the substantially ground potential by the switching of the switching element and the output voltage with a predetermined threshold value and outputs a detection signal according to the comparison result. When,
A switching power supply device comprising: Further comprising a low pass filter for filtering the switching voltage and outputting a filter output voltage,
The switching power supply device 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 receives 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. 3. The switching power supply device according to claim 2, further comprising a window comparator including an upper limit voltage input terminal that includes: A low pass filter for outputting a filter output voltage filters the drive signal output from the flip-flop included in said feedback control section,
An amplifier that amplifies the filter output voltage at a predetermined amplification factor and outputs an amplified voltage,
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. Said feedback control section, the switching power supply device according to claim 1 comprising a flip-flop for generating a drive signal, and a driver for generating a control signal to be applied to the control terminal of the switching element on the basis of the drive signal And
A level conversion unit that generates a conversion signal by inverting the High level and the Low level of the control signal;
A low-pass filter for filtering the converted signal and outputting a filter output voltage,
An amplifier that amplifies the filter output voltage at a predetermined amplification factor and outputs an amplified voltage,
The switching power supply device, 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. The switching power supply device according to claim 4 or 5, further comprising a window comparator including an upper limit voltage input terminal.   7. The switching power supply device according to claim 4, wherein the amplification factor is variable according to the input voltage.   The switching power supply device according to any one of claims 1 to 7, wherein the comparison unit outputs the detection signal to an external host computer.   The said feedback control part performs feedback control by PWM control, The switching power supply device of any one of Claims 1-8 characterized by the above-mentioned.   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 on-vehicle electronic device comprising the switching power supply device according to any one of claims 1 to 10.

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