JP2008306824A - Switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To equalize the on/off duty of a transistor MP0 and the duty of an output modulation signal of a comparator which conducts pulse width modulation to provide a constant dead time. <P>SOLUTION: An error signal Ec between an output detection signal Eo and a reference value Er is obtained by an error amplifier 4, and a pulse width modulation signal PWM1 is obtained by comparing by the comparator 2 the error signal Ec with a triangular wave signal Et output from a triangular wave/rectangular wave oscillation circuit 1, and the transistor MP0 is driven by a driver circuit 5. A pulse width modulation signal PWM2 is obtained in a pulse generation circuit 3 by the output signal PWM1 of the comparator 2 and a rectangular wave signal Ek output from the triangular wave/rectangular wave oscillation circuit 1 to drive a transistor MN0 by a driver circuit 6. The pulse generation circuit has a capacitor C3 which is recharged by the AND signal of the pulse width modulation signal PWM1 and the rectangular wave signal Ek and a comparator 302 which compares the charging voltage of the capacitor C3 with the reference value V1 to output the pulse width modulation signal PWM2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a switching power supply device, and more particularly to a switching power supply device that operates as a synchronous rectification type DC-DC converter power supply device.

<First Conventional Example>
FIG. 6 shows a basic circuit of a zero volt switch pulse width modulation (ZVS-PWM) type switching regulator as a first conventional switching power supply device, and FIG. 7 shows a control circuit thereof (see, for example, Patent Document 1). In FIG. 6, MN11 and MN12 are N-channel MOS power transistors as switching elements, C4 and C5 are capacitors connected in parallel with the transistors MN11 and MN12, L1 is a choke coil, C1 is an output capacitor, and RL is a load resistor. , Vi are input terminals (input voltage Vi), and Vo is an output terminal (output voltage Vo).

  By applying a signal to the gate terminals G1 and G2 of the transistors MN11 and MN12 so that the transistors MN11 and MN12 are alternately turned on and off, an output voltage Vo that is stepped down with respect to the input voltage Vi is obtained. Signals applied to the gate terminals G1 and G2 are generated by the control circuit of FIG.

  In FIG. 7, 4 is an error amplifier that detects and amplifies an error between the output voltage Vo and the reference voltage Er and outputs it as an error signal Ec, 11 is a triangular wave oscillation circuit that oscillates a triangular wave signal Et, and 12 is an error output from the error amplifier 4. A comparator which compares the signal Ec with the triangular wave signal Et output from the triangular wave rectangular wave oscillation circuit 11 and outputs the pulse width modulation signal PWM1, and 13 inverts the output modulation signal PWM1 of the comparator 12 and outputs the modulation signal PWM1X. Inverter, 14 is a T flip-flop that receives modulation signal PWM1, 15 is a T flip-flop that receives modulation signal PWM1X, 16 and 17 are integration circuits, and 18 and 19 are XOR circuits.

  The operation of the control circuit in FIG. 7 will be described. FIG. 8 shows waveforms of signals at various parts of the control circuit. The error signal Ec generated from the output voltage Vo of the switching power supply device and the reference voltage Er is compared with the triangular wave signal Et of the triangular wave rectangular wave oscillation circuit 11 by the comparator 12, and a modulation signal PWM1 is generated. As shown in FIG. 8, when the error signal Ec is higher than the triangular wave signal Et, the modulation signal PWM1 is at a low level, and when it is low, it is at a high level.

  This modulation signal PWM1 is input to the T flip-flop 14 and is also input to the T flip-flop 15 by the inverter 13 as an inverted modulation signal PWM1X. The T flip-flops 14 and 15 perform a toggle operation in which the output level is inverted every time the input signal rises. Therefore, the output level of the output signal Q1 of the T flip-flop 14 is inverted at the rising edge of the modulation signal PWM1, and the output level of the output signal Q2 of the T flip-flop 15 is inverted at the falling edge of the modulation signal PWM1. In FIG. 8, when the waveforms of the output signals Q1 and Q2 of the T flip-flops 14 and 15 are compared, it can be seen that the timing is shifted by the time when the modulation signal PWM1 becomes high level.

  When the output signal Q1 of the T flip-flop 14 is input to the integration circuit 16, a signal INT1 having a waveform with a small rising / falling slew rate is output as shown in FIG. When the exclusive OR of the signal INT1 and the output signal Q2 of the T flip-flop 15 is taken by the XOR circuit 18, the waveform of the modulation signal PWM3 is obtained. The modulation signal PWM3 rises with a delay time td from the rise of the output modulation signal PWM1 of the comparator 12 due to the slew rate of the output signal INT1 of the integration circuit 16 and the threshold value of the XOR circuit 18.

  When the output signal Q2 of the T flip-flop 15 is input to the integrating circuit 17, a signal INT2 having a waveform with a small rising / falling slew rate is output as shown in FIG. When the exclusive OR of the signal INT2 and the output signal Q1X of the T flip-flop 14 is taken by the XOR circuit 19, a modulation signal PWM4 is obtained. The modulation signal PWM4 rises with a delay time td from the fall of the output modulation signal PWM1 of the comparator 12 due to the slew rate of the output signal of the integration circuit 17 and the threshold value of the XOR circuit 19.

  The fall timing of the modulation signal PWM3 is the same as the fall of the modulation signal PWM1, and the fall timing of the modulation signal PWM4 is the same as the rise of the modulation signal PWM1. Therefore, the waveforms of the modulation signals PWM3 and PWM4 have opposite levels, the modulation signal PWM3 becomes the control signal for the gate terminal G1 in FIG. 6, and the modulation signal PWM4 becomes the control signal for the gate terminal G2 in FIG. The transistors MN11 and MN12 are repeatedly turned on / off alternately. Further, the signal is simultaneously at a low level for a certain time td. This period is a dead time in which the transistors MN11 and MN12 are simultaneously turned off, and the transistors MN11 and MN12 are simultaneously turned on and a through current flows to reduce the efficiency. Can be prevented.

<Second Conventional Example>
FIG. 9 shows a second conventional switching power supply device (see, for example, Patent Document 2). In FIG. 9, MP0 is a P-channel power MOS transistor as a switching element, MN0 is an N-channel power MOS transistor as a switching element, D1 is a freewheel diode, L1 is a choke coil, and RB1 and RB2 are for output voltage detection. A resistor, C1 is an output capacitor, and RL is a load resistor. An error amplifier 4 compares the divided voltage value Eo of the output voltage Vo detected by the resistors RB1 and RB2 with the reference voltage Er and outputs an error signal Ec. A comparator 21 compares the error signal Ec with the triangular wave signal Et output from the triangular wave oscillation circuit 11, and 22 indicates a value Es obtained by level-shifting the error signal Ec by ΔE in the positive direction by the level shift circuit 23 and the triangular wave signal Et. A comparator 24 for comparison is an amplifier for driving the transistor MP0 with the output of the comparator 22, and 25 is an amplifier for driving the transistor MN0 with the output of the comparator 24.

  Next, the operation will be described. The signal waveform of each part is shown in FIG. By comparing the error signal Ec and its shift value Es with the triangular wave signal Et in the comparators 21 and 22, modulation signals PWM5 and PWM6 are generated. The output modulation signal PWM5 of the comparator 21 is at a low level when the error signal Ec is larger than the triangular wave signal Et, and is at a high level when the error signal Ec is smaller than the triangular wave signal Et.

  On the other hand, the output modulation signal PWM6 obtained by comparing the shift value Es and the triangular wave signal Et by the comparator 22 rises with a delay of τ from the rise of the output modulation signal PWM5 of the comparator 21, and falls of the output modulation signal PWM5 of the comparator 21. Fall earlier by τ.

The output modulation signals PWM5 and PWM6 of the comparators 21 and 22 become drive signals for the transistors MP0 and MN0. In FIG. 10, it represents on / off. In the period τ between the output signal of the comparator 21 and the output signal of the comparator 22, a dead time occurs when both the transistors MP0 and MN0 are turned off, and the transistors MP0 and MN0 are simultaneously turned on to prevent a through current from flowing. Thus, a reduction in efficiency can be avoided. Note that the dead time τ can be changed by changing the voltage shift amount ΔE of the level shift circuit 23.
JP-A-8-168239 JP-A-6-225522

  In the first conventional example described with reference to FIGS. 6 to 8, the modulation signal PWM3 rises with a delay of td from the rise of the output modulation signal PWM of the comparator 12, and rises almost simultaneously with the fall of the output modulation signal PWM1 of the comparator 12. Go down. The modulation signal PWM4 falls almost simultaneously with the rise of the output modulation signal PWM1 of the comparator 12, and rises with a delay of td from the fall of the output signal of the comparator 12. As a result, both the modulation signals PWM3 and PWM4 have the same timing as either the rising or falling edge of the output modulation signal PWM1 of the comparator 12, and the duty of the output modulation signal PWM1 of the comparator 12 and the modulation signal PWM3 or the modulation signal There was a problem that the duty of PWM4 was different.

  In the second conventional example described with reference to FIGS. 9 and 10, since the output modulation signal PWM5 of the comparator 21 is input to the gate of the transistor MP0 via the amplifier 24, the duty of the output modulation signal PWM5 of the comparator 21 is increased. Since the transistor MP0 is turned on / off, there is no problem with the first conventional example. However, if the frequency of the triangular wave signal Et is changed while keeping the shift value Es constant, there is a problem that the dead time during which the transistors MP0 and MN0 are simultaneously turned off changes depending on the frequency.

  The present invention solves the above problems, the duty of the output modulation signal of the comparator that performs pulse width modulation and the on / off duty of the switch element are the same, and a constant dead time is obtained regardless of the triangular wave oscillation frequency. An object is to provide an existing switching power supply.

A switching power supply device according to a first aspect of the present invention includes a first switch element connected to a high potential power supply, a second switch element connected to a low potential power supply, and a common connection of the first and second switch elements. An inductive element connected between a point and an output terminal; a first capacitive element connected between the output terminal and the low-potential power supply; a voltage detection element that detects an output voltage of the output terminal; An error amplifier that detects an error between the voltage detection signal detected by the voltage detection element and the first reference value and outputs an error signal, and compares the error signal with the triangular wave signal to obtain a first pulse width modulation signal. A first comparator to be generated; a first driver circuit that receives the first pulse width modulation signal to drive the first switch element; and a high level at a rising edge of the triangular wave signal and the triangular wave signal; Low when going down A triangular wave rectangular wave oscillating circuit for oscillating a rectangular rectangular wave signal; a pulse generating circuit for receiving the rectangular wave signal and the first pulse width modulated signal and generating a second pulse width modulated signal; And a second driver circuit that receives the pulse width modulation signal of 2 and drives the second switch element complementarily with the first switch element, wherein the pulse generation circuit comprises: A first current source; a second capacitive element that is charged and discharged by a current of the first current source by a logical product signal of the first pulse width modulation signal and the rectangular wave signal; and the second capacitance And a second comparator for comparing the charging voltage of the element with a second reference value and outputting the second pulse width modulation signal.
According to a second aspect of the present invention, in the switching power supply device according to the first aspect, the triangular wave signal and the rectangular wave signal of the triangular wave rectangular wave oscillation circuit are generated as the first current source in the pulse generation circuit. It is characterized by using a current of a current source for the purpose.
According to a third aspect of the present invention, in the switching power supply device according to the second aspect, the pulse generation circuit sets the second reference value to a value proportional to the current of the first current source. Features.

According to the first aspect of the invention, since the first switch element is driven by the first pulse width modulation signal, the on / off duty of the first switch element is equal to the duty of the first pulse modulation signal. The same. In the pulse generation circuit, the reference voltage of the first current source that charges and discharges the second capacitor and the second comparator that detects the charge voltage of the second capacitor is related to the oscillation frequency of the triangular wave signal. Therefore, there is an advantage that the dead time can be made constant regardless of the frequency.
According to the second aspect of the present invention, the current for generating the triangular wave signal and the rectangular wave signal of the triangular wave rectangular wave oscillation circuit is used as the first current source for charging and discharging the second capacitive element in the pulse generation circuit. Since the current of the source is used, the charging voltage waveform of the second capacitor element of the pulse generation circuit is similar to the triangular wave signal waveform. Therefore, in the invention according to claim 1, since the second capacitor element is charged with a constant current, it takes a long charge time when the oscillation frequency is low, and the voltage of the second capacitor element is saturated with the power supply voltage. However, the invention according to claim 2 has an advantage that the voltage of the second capacitive element is not saturated regardless of the frequency of the triangular wave signal.
According to the invention of claim 3, by making the reference voltage for detecting the charging voltage of the second capacitor element in the pulse generation circuit proportional to the oscillation frequency of the triangular wave signal, the dead time is made constant regardless of the frequency. There are advantages that can be made.

<First embodiment>
FIG. 1 is a block diagram showing the overall configuration of a switching power supply apparatus according to a first embodiment of the present invention. In FIG. 1, a P-channel power MOS transistor MP0, an N-channel power MOS transistor MN0, a freewheeling diode D1, a choke coil L1, output voltage detection resistors RB1 and RB2, an output capacitor C1, a load resistor RL1 and The error amplifier 4 is the same as that shown in FIG.

  In this embodiment, in addition to this, a triangular wave rectangular wave oscillation circuit 1 that oscillates a triangular wave signal Et and a rectangular wave signal Ek, an error signal Ec output from the error amplifier 4 and a triangular wave signal Et output from the triangular wave rectangular wave oscillation circuit 1. And a comparator 2 that outputs a pulse width modulation signal PWM1 and an output modulation signal PWM1 of the comparator 2 and a rectangular wave signal Ek output from the triangular wave rectangular wave oscillation circuit 1 and inputs a pulse width modulation signal PWM2 A pulse generation circuit 3 for outputting, a driver circuit 5 for driving the transistor MP0 by the output modulation signal PWM1 of the comparator 2, and a driver circuit 6 for driving the transistor MN0 by the output modulation signal PWM2 of the pulse generation circuit 3 are provided.

  FIG. 2 is a circuit diagram of a circuit embodying the control circuit 7 including the triangular wave rectangular wave oscillation circuit 1, the comparator 2, and the pulse generation circuit 3 in FIG. The triangular wave rectangular wave oscillation circuit 1 includes a current source I2, P channel MOS transistors MP4, MP5 and MP6 constituting a current mirror, N channel MOS transistors MN4 and MN6 constituting a current mirror, and an N channel MOS which controls transistors MN4 and MN6. A transistor MN5, a capacitor C2, comparators 103 and 104, and NOR circuits 103 and 104 are included. A high potential voltage VH is applied to the comparator 101, and a low potential voltage VL is applied to the comparator 102 as a comparison voltage. Then, the triangular wave signal Et is output to the drain common connection point of the transistors MP4 and MN4, and the rectangular wave signal Ek is output to the output point of the NOR circuit 103.

  The pulse generation circuit 3 includes a current source I1, P-channel MOS transistors MP1, MP2, and MP3 that constitute a current mirror, N-channel MOS transistors MN1 and MN2 that constitute a current mirror, and an N-channel MOS transistor MN3 that controls the transistors MN1 and MN2. , An AND circuit 301, a capacitor C3, and a comparator 302 that compares the voltage of the capacitor C3 with the reference voltage V1. The transistors MP1 to MP3, MN1 to MN3, and the current source I1 constitute a charge / discharge circuit that charges and discharges the capacitor C3.

  Next, the operation will be described. 5 shows the error signal Ec, the triangular wave signal Et and the rectangular wave signal Ek output from the triangular wave rectangular wave oscillation circuit 1, the output modulation signal PWM1 of the comparator 2, the output modulation signal PWM2 of the comparator 302, the voltage VC3 of the capacitor C3, the reference The waveform of the voltage V1 is shown. In the triangular wave rectangular wave oscillation circuit 1, the triangular wave signal Et rises when the rectangular wave signal Ek is high level, and the triangular wave signal Et falls when the rectangular wave signal Ek is low level. The comparator 2 sets the output modulation signal PWM1 to the low level when the error signal Ec output from the error amplifier 4 is larger than the voltage of the triangular wave signal Et, and sets it to the high level when it is smaller. The output modulation signal PWM1 rises when the rectangular wave signal Ek is at a high level and falls when the rectangular wave signal Ek is at a low level due to the output relationship between the rectangular wave signal Ek and the triangular wave signal Et.

  Therefore, when the AND of the rectangular wave signal Ek and the modulation signal PWM1 is taken by the AND circuit 301, when both the rectangular wave signal Ek and the modulation signal PWM1 are high level, the output of the AND circuit 301 becomes high level and the transistor MN3 is turned on. Therefore, MN1 and MN2 are turned off, and the capacitor C3 is charged by the transistor MP1 that is turned on. At this time, since the transistors MP1 and MP3 are current mirrors, they are charged with a constant current proportional to the current source I1. When the rectangular wave signal Ek is at a low level, the output of the AND circuit 301 is at a low level and the transistor MN3 is turned off, so that the transistors MN1 and MN2 are turned on. At this time, if the area of the transistor MN1 is set to be twice that of the transistor MP1, the same current as the current flowing through the transistor MP1 is drawn from the capacitor C3, and the capacitor C3 is discharged. As a result, the voltage VC3 of the capacitor C3 becomes a triangular triangular wave signal during the period in which the modulation signal PWM1 is at a high level. Therefore, by comparing the voltage VC3 with the reference voltage V1 in the comparator 302, a new modulation is performed. Signal PWM2 is generated.

  The modulation signal PWM2 rises with a delay of time tDr from the rising edge of the modulation signal PWM1, and has a waveform that falls earlier by the time tDf than the falling edge of the modulation signal PWM1, and serves as an input signal to the driver circuit 6. The transistors PM0 and MN0 are turned on / off by the modulation signals PWM1 and PWM2. The transistor PM0 is turned on when the modulation signal PWM1 is at a low level and turned off when the modulation signal PWM1 is at a high level. The transistor MN0 is turned on when the modulation signal PWM2 is at a high level and turned off when the modulation signal PWM2 is at a low level.

  As shown in FIG. 5, since the period during which the modulation signal PWM2 is at the high level is shorter than the period during which the modulation signal PWM1 is at the high level, both the transistors PM0 and MN0 are off during the period of the times tDr and tDf. It becomes. This period is a dead time, and, as in the conventional example, the transistors PM0 and MN0 are simultaneously turned on to prevent a reduction in efficiency due to the flow of through current.

  In this embodiment, since the output modulation signal PWM1 of the comparator 2 that performs pulse width modulation is applied to the gate of the transistor MP1 by the driver circuit 5, the duty of the modulation signal PWM1 is the same as the on / off duty of the transistor MP1. . Further, in the pulse generation circuit 3, since the current source I1 for charging the capacitor C3 and the reference voltage V1 are not related to the triangular wave signal Et, the dead time is constant regardless of the frequency.

<Second embodiment>
FIG. 3 is a circuit diagram of a second embodiment in which the control circuit 7 including the triangular wave rectangular wave oscillation circuit 1, the comparator 2, and the pulse generation circuit 3 in FIG. 1 is embodied. Here, a part of the pulse generation circuit 3 that generates the modulation signal PWM2 is configured in common with the circuit that charges and discharges the capacitor C2 of the triangular wave rectangular wave oscillation circuit 1. The charge / discharge circuit is composed of transistors MP1 and MN1. The gate of the transistor MN1 is connected to the gate of the transistor MN4 so that the drain current of the transistor MN1 flows at the same timing as the drain current of the transistor MN4. The current value is proportional to the transistor MN4. Further, the gate of the transistor MP1 is connected to the gate of the transistor MP4 so that the drain current flow timing of the transistor MP1 is the same as the drain current flow timing of the transistor MP4 so that the current value is proportional to the transistor MP4. To do. That is, the current source I2 of the triangular wave rectangular wave oscillation circuit 1 is shared as the current source of the pulse generation circuit 3.

  When the rectangular wave signal Ek of the triangular wave rectangular wave oscillation circuit 1 becomes high level, the transistor MN5 is turned on, the transistor MN4 is turned off, the capacitor C2 is charged by the drain current of the transistor MP4, and the voltage of the triangular wave signal Et rises. At this time, in the capacitor C3, if the output modulation signal PWM1 of the comparator 2 is at a low level, the transistor MN7 is turned on and the drain current of the transistor MP1 flows so that charging is not performed, but the output modulation signal PWM1 is at a high level. At this point, the transistor MN7 is turned off, and charging is started. When the capacitor C3 is charged, the voltage VC3 increases.

  When the rectangular wave signal Ek becomes low level, the transistor MN5 is turned off, and the transistors MN5, MN4, and MN1 operate as a current mirror. If the drain current of the transistor MN4 is set larger than the drain current of the transistor MP4, the capacitor C2 is discharged by the drain current of the transistor MN4, and the voltage of the triangular wave signal Et drops. Also, in the capacitor C3, when the modulation signal PWM1 is in a high level state, the transistor MN7 remains off by the inverter 303. Therefore, if the drain current of the transistor MN1 is set larger than the drain current of the transistor MP1, the capacitor C3 C3 is discharged by the drain current of the transistor MN1, and the voltage VC3 drops. Similar to the configuration of FIG. 2, when the voltage VC3 of the capacitor C3 is compared with the reference voltage V1 by the comparator 302, a waveform similar to the modulation signal PWM2 having the waveform of FIG. 5 is obtained.

  According to the present embodiment, since the charge / discharge current of the capacitor C3 of the pulse generation circuit 3 can be made proportional to the charge / discharge current of the triangular wave rectangular wave oscillation circuit 1, the voltage waveform of the capacitor C3 of the pulse generation circuit 3 is a triangular wave. Similar to the signal Et. Therefore, if the capacitor C3 is charged with a constant current as in the first embodiment, the charging time becomes longer at a low frequency, and the voltage of the capacitor C3 may be saturated with the power supply voltage. In the second embodiment, however, Regardless of the frequency of the triangular wave signal, the voltage of the capacitor C3 can be prevented from being saturated with the power supply voltage.

<Third embodiment>
FIG. 4 is a circuit diagram of a third embodiment in which the control circuit 7 including the triangular wave rectangular wave oscillation circuit 1, the comparator 2, and the pulse generation circuit 3 in FIG. 1 is embodied. Here, in contrast to the circuit shown in FIG. 3, a transistor MP6 connected to the current source I2 and a P-channel MOS transistor MP7 serving as a current mirror are newly provided, and a resistance is provided between the drain of the transistor MP7 and the ground. R1 is connected, and a current proportional to the current source I2 is passed through the resistor R1. At this time, the voltage generated in the resistor R1 is set as a reference voltage V1. By doing so, since the oscillation frequency of the triangular wave signal Et is determined by the current source I2, the value of the reference voltage V1 is proportional to this oscillation frequency.

  Thus, according to the present embodiment, the reference voltage V1 of the comparator 302 that generates the modulation signal PWM2 is proportional to the frequency of the triangular wave signal Et, so that the dead time can be made constant regardless of the frequency.

1 is an overall block diagram of a switching power supply device according to a first embodiment of the present invention. It is a detailed circuit diagram of the control circuit of the switching power supply device of FIG. It is a detailed circuit diagram of the control circuit of the second embodiment. It is a detailed circuit diagram of the control circuit of the third embodiment. It is a wave form diagram of each signal of the control circuit of FIGS. It is a circuit diagram of the switching power supply device of the 1st prior art example. It is a block diagram of the control circuit of the switching power supply device of FIG. It is a wave form diagram of each signal of the control circuit of FIG. It is a circuit diagram of the switching power supply device of the 2nd prior art example. It is a wave form diagram of each signal of the switching power supply circuit of FIG.

Explanation of symbols

Eo: Divided value of output voltage Vo Er: Reference voltage Ec: Error signal Et: Triangular wave signal Ek: Rectangular wave signal 1: Triangular wave rectangular wave oscillation circuit 101, 102: Comparator, 103, 104: NOR circuit 2: Comparison Unit 3: Pulse generation circuit, 301: AND circuit, 302: Comparator, 303: Inverter 11: Triangular wave oscillation circuit 12: Comparator 13: Inverter 14, 15: T flip-flop 16, 17: Integration circuit 18, 19: XOR Circuits 21, 22: Comparator 23: Level shift circuit 24, 25: Amplifier

Claims (3)

A first switch element connected to a high-potential power supply; a second switch element connected to a low-potential power supply; and an inductive element connected between a common connection point of the first and second switch elements and an output terminal A first capacitance element connected between the output terminal and the low-potential power source, a voltage detection element that detects an output voltage of the output terminal, a voltage detection signal detected by the voltage detection element, An error amplifier that detects an error from a reference value of 1 and outputs an error signal; a first comparator that compares the error signal with a triangular wave signal to generate a first pulse width modulation signal; A first driver circuit that receives the pulse width modulation signal and drives the first switch element, and oscillates the triangular wave signal and a rectangular wave signal that is at a high level at the rising edge of the triangular wave signal and at a low level at the falling edge. Triangular wave square wave A circuit; a pulse generation circuit that receives the rectangular wave signal and the first pulse width modulation signal to generate a second pulse width modulation signal; and the second pulse width modulation signal that receives the second pulse width modulation signal. A switching power supply comprising a second driver circuit for driving a switch element in a complementary manner with the first switch element,
The pulse generation circuit includes: a first current source; a second capacitive element that is charged / discharged by a current of the first current source by a logical product signal of the first pulse width modulation signal and the rectangular wave signal; And a second comparator for comparing the charging voltage of the second capacitor element with a second reference value and outputting the second pulse width modulation signal.   2. The pulse generation circuit uses the triangular wave signal of the triangular wave rectangular wave oscillation circuit and a current of a current source for generating the rectangular wave signal as the first current source. Switching power supply.   3. The switching power supply device according to claim 2, wherein the pulse generation circuit sets the second reference value to a value proportional to the current of the first current source.

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