JP2006353095A - Power supply device, its control circuit and control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply device capable of switching smoothly, without operating the conditions that do not fluctuate by output voltages, and to provide its control circuit and control method. <P>SOLUTION: A power supply device has a voltage converter circuit for converting input voltages and outputting a first converted voltage and a second converted voltage; a first switching element which is provided with rectifying elements in parallel to which a first converted voltage is applied, and performs a switching function, in response to a first control signal given, a second switching element which is provided with rectifying elements in parallel to which a second converted voltage is applied, and performs a switching function, in response to a second control signal given; and a detection circuit for detecting output currents controlled by the first switching element and the second switching element, wherein the first switching element and the second switching element are controlled by output currents. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power supply device, a control circuit thereof, and a control method, wherein a voltage conversion circuit that converts an input voltage and outputs a first conversion voltage and a second conversion voltage, and a rectifier element are provided in parallel. While the first conversion voltage is applied, a first switching element that performs switching according to a given first control signal, and a rectifying element are provided in parallel, and a second conversion voltage is applied, A power supply device comprising: a second switching element that performs switching according to a second control signal applied; a first switching element; and a detection circuit that detects an output current controlled by the second switching element; The present invention relates to a control circuit and a control method.

  FIG. 1 is a block diagram of an information processing system.

  The information processing system 1 includes an AC power supply 11, an AC-DC conversion unit 12, n main boards 13-1 to 13-n, and a network 14. The AC power supply 11 supplies an AC voltage (current) to the AC-DC converter 12. The AC-DC converter 12 converts an AC voltage (current) from the AC power supply 11 into a DC voltage (current).

  The DC voltage (current) converted by the AC-DC converter 12 is supplied to the main boards 13-1 to 13-n. The main boards 13-1 to 13-n are information processing apparatuses that are connected via the network 14 and perform processing while communicating with each other, and each main board is a DC-DC converter 21-1 to 21-21. -3, a CPU 22, a storage device 23, and a communication device 24.

  The DC-DC converter 21-1 generates a predetermined DC voltage based on the DC voltage (current) from the AC-DC converter 12 and supplies it to the CPU 22. The CPU 22 is driven by the DC voltage from the DC-DC converter 21-1 and performs processing. The DC-DC converter 21-2 generates a predetermined DC voltage based on the DC voltage (current) from the AC-DC converter 12 and supplies it to the storage device 23. The storage device 23 is driven by the DC voltage from the DC-DC conversion unit 21-2 and stores data processed by the CPU 22 and data supplied from the communication device 23. The DC-DC converter 21-3 generates a predetermined DC voltage based on the DC voltage (current) from the AC-DC converter 12 and supplies the DC voltage to the communication device 24. The communication device 24 controls communication with the network 14.

  FIG. 2 is a block diagram of the DC-DC converter 21-1.

  The DC-DC conversion unit 21-1 includes DC-DC conversion circuits 31-1, 31-2 and diodes D1, D2. The DC-DC conversion circuit 31-1 converts the DC voltage from the AC-DC conversion unit 12 into a predetermined voltage. The DC-DC conversion circuit 31-1 detects the output current and the output voltage, and performs control so that the output voltage becomes constant. The output voltage of the DC-DC conversion circuit 31-1 is supplied to the CPU 22 via the diode D1. The DC-DC conversion circuit 31-2 has the same configuration as the DC-DC conversion circuit 31-1, and the output voltage is supplied to the CPU 22 via the diode D2.

  During normal operation, direct current from the DC-DC conversion circuit 31-1 and the DC-DC conversion circuit 31-2 is supplied to the CPU 22. When the rise of the output voltage of the DC-DC conversion circuit 31-1 is earlier than the rise of the output voltage of the DC-DC conversion circuit 31-2 at the rise, the diode D2 causes the DC-DC conversion circuit 31-1 to No current flows through the conversion circuit 31-2. That is, the reverse flow of the current to the DC-DC conversion circuit 31-2 can be prevented by the diode D2.

  When the rise of the output voltage of the DC-DC conversion circuit 31-2 is earlier than the rise of the output voltage of the DC-DC conversion circuit 31-1 at the rise, the diode D1 causes the DC-DC conversion circuit 31-2 to move from the DC-DC. No current flows through the conversion circuit 31-1. That is, the reverse flow of the current to the DC-DC conversion circuit 31-1 can be prevented by the diode D1.

  Next, the DC conversion circuits 31-1 and 31-2 will be described in detail.

  FIG. 3 is a block diagram of the DC-DC conversion circuit 31-1.

  The DC-DC conversion circuit 31-1 includes an inverter circuit 41, a transformer 42, switching elements Q1 and Q2, diodes D11 and D12, a control circuit 43, a coil L0, an output current detection resistor Rs, and a capacitor C0. Yes.

  A DC voltage from the AC-DC converter 12 is applied to the inverter circuit 41. The inverter circuit 41 converts the DC voltage from the AC-DC converter 12 into an AC voltage.

  The AC voltage converted by the inverter circuit 41 is applied to the primary coil L1 of the transformer 42. An alternating current corresponding to the alternating voltage from the inverter circuit 41 flows through the primary coil L1 of the transformer 42, and a magnetic flux corresponding to the flowing current is generated. The magnetic flux generated by the transformer L1 is transmitted to the secondary coils L21 and L22 of the transformer 42. A secondary current corresponding to the magnetic flux from the primary coil L1 flows through the secondary coils L21 and L22 of the transformer.

  One end of the secondary coil L21 is grounded via the source-drain of the transistor Q1, and the other end is connected to one end of the choke coil L0. One end of the secondary coil L22 is grounded via the source-drain of the transistor Q2, and the other end is connected to one end of the choke coil L0. The transistors Q1 and Q2 are composed of, for example, a MOS-FET (metal-oxide-semiconductor field effect transistor).

  The gates of the transistors Q1 and Q2 are connected to the control circuit 43, and are switched according to the switching pulse from the control circuit 43. A diode D11 is connected in parallel between the source and drain of the transistor Q1. The diode D11 is connected such that the anode is on the ground side and the cathode is on the secondary coil L21 side.

  The other end of the choke coil L0 is connected to the output terminal Tout via the output current detection resistor Rs. A smoothing capacitor C0 is connected between the output terminal Tout and the ground terminal Tgnd. The potential at the connection point between the secondary coil L21 and the secondary coil L22 of the transformer 42 is smoothed and output by the choke coil L0 and the smoothing capacitor C0.

  The control circuit 43 is supplied with the voltage across the output current detection resistor Rs and the output voltage at the output terminal Tout. When the output voltage Vout from the output terminal Tout decreases, the control circuit 43 decreases the pulse width or period of the switching pulse supplied to the gates of the transistors Q1 and Q2, and increases the output voltage Vout from the output terminal Tout. Then, the pulse width of the switching pulse supplied to the gates of the transistors Q1 and Q2 is increased or the period is decreased.

  At this time, a switching pulse is supplied to the gate of the transistor Q1 and the gate of the transistor Q2, and the transistor Q1 and the transistor Q2 are switched alternately.

  The control circuit 43 detects the output current from the voltage across the output current detection resistor Rs. When the output current is smaller than a predetermined threshold, that is, when the load is light, the transistors Q1 and Q2 are always turned off. Diode rectification is performed by the diodes D11 and D12. Since diode rectification eliminates the need for unnecessary switching, power loss due to switching can be reduced.

  Further, the control circuit 43 detects the output current from the voltage across the output current detection resistor Rs, and when the output current is larger than a predetermined threshold, that is, during heavy load, the transistors Q1 and Q2 are set to the output voltage Vout. The synchronous rectification is performed by switching with the corresponding switching pulse. By performing synchronous rectification, the on-voltage of the transistors Q1 and Q2 is about 0.01 [V], which is sufficiently smaller than the on-voltage of the diodes D11 and D12 of about 0.7 [V]. Since the voltage drop due to the switching element can be reduced and the current can be efficiently supplied to the load, power loss can be reduced.

  However, in this type of conventional power supply device, when switching between synchronous rectification and diode rectification by a voltage difference in on-resistance between a switching element for performing synchronous rectification and a switching element for performing diode rectification, a solid line in FIG. As shown in the figure, there was a problem that the output voltage fluctuated.

  When this type of power supply device such as a computer is applied, it is necessary to suppress the voltage fluctuation to several tens of m [V] or less. In order to reduce fluctuations in the output voltage as shown in FIG. 4, it is necessary to increase the inductance of the choke coil L0 and the capacitance of the smoothing capacitor C0. By increasing the inductance of the choke coil L0 and the capacitance of the smoothing capacitor C0, fluctuations in the output voltage can be reduced as shown by the broken line in FIG. However, when the inductance of the choke coil L0 and the capacitance of the smoothing capacitor C0 are increased, there are problems such as an increase in size of the device and an increase in cost.

  Further, in a power supply system having a redundant configuration of these power supply devices, a diode is connected between the output of the power supply device and the load so that the direction from the power supply device to the load is the forward direction as shown in FIG. Therefore, there are problems such as a loss due to the diode and an increase in the number of parts, resulting in an increase in cost.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a power supply apparatus that can smoothly switch the operation state without fluctuation of the output voltage, a control circuit thereof, and a control method.

  In the present invention, a voltage conversion circuit that converts an input voltage and outputs a first conversion voltage and a second conversion voltage, and a rectifying element are provided in parallel, and the first conversion voltage is applied, A first switching element that performs switching in response to a given first control signal and a rectifying element are provided in parallel, and a second conversion voltage is applied, and switching is performed in accordance with a given second control signal. A second switching element that performs the detection, a detection circuit that detects an output current controlled by the first switching element and the second switching element, a first control signal when the output current is smaller than a predetermined threshold, and A first operation state in which the output of the second control signal is stopped, and a second operation state in which the first control signal and the second control signal are alternately output when the output current is larger than a predetermined threshold value. By When the control is performed and the transition from the first operation state to the second operation state is performed, the first switching element and the second switching per unit time of the first control signal and the second control signal And a control circuit for gradually increasing the on-time during which the element is turned on.

  The control circuit gradually increases the pulse widths of the first control signal and the second control signal to thereby increase the first switching element and the second control unit per unit time of the first control signal and the second control signal. The on-time when the switching element is turned on is gradually increased. The control circuit is a triangle wave generating circuit that generates a triangular wave, a time constant circuit that generates an integrated waveform of a signal in response to power-on, and the magnitude relationship between the triangular wave generated by the triangular wave generating circuit and the integrated waveform output from the time constant circuit A comparison circuit for outputting a comparison result according to the first switching element and the second switching element per unit time of the first control signal and the second control signal according to the output of the comparison circuit. The on-time for turning on is gradually increased.

  Further, the control circuit gradually increases the frequencies of the first control signal and the second control signal to thereby increase the first switching element and the second control unit per unit time of the first control signal and the second control signal. The on-time for turning on the switching element is gradually increased. The control circuit is a triangle wave generating circuit that generates a triangular wave, a time constant circuit that generates an integrated waveform of a signal in response to power-on, and the magnitude relationship between the triangular wave generated by the triangular wave generating circuit and the integrated waveform output from the time constant circuit A comparison circuit that outputs a comparison result according to the frequency, a pulse generation circuit that outputs a pulse waveform of a constant frequency, and an AND circuit that outputs a logical product of the comparison result of the comparison circuit and the pulse waveform of the pulse generation circuit. The on-time for turning on the first switching element and the second switching element per unit time of the first control signal and the second control signal is gradually increased according to the output of the comparison circuit. To do.

  In the present invention, a voltage conversion circuit that converts an input voltage and outputs a first conversion voltage and a second conversion voltage, and a rectifier element are provided in parallel, and the first conversion voltage is applied. In addition, a first switching element that performs switching according to a given first control signal and a rectifying element are provided in parallel, a second conversion voltage is applied, and a second control signal that is given A second switching element that performs switching in response, a detection circuit that detects an output current controlled by the first switching element and the second switching element, and a first circuit when the output current is smaller than a predetermined threshold value. A first operating state in which the output of the control signal and the second control signal is stopped, and a second operating state in which the first control signal and the second control signal are alternately output when the output current is larger than a predetermined threshold value. Action When the transition from the second operating state to the first operating state is performed, the first switching element and the second switching unit per unit time of the first control signal and the second control signal And a control circuit for gradually reducing the ON time during which the two switching elements are turned on.

  Further, according to the present invention, a voltage conversion circuit that converts an input voltage and outputs a first conversion voltage and a second conversion voltage, and a rectifying element are provided in parallel, and the first conversion voltage is applied. In addition, a first switching element that performs switching in accordance with a given first control signal and a rectifying element are provided in parallel, and a second conversion voltage is applied, and in response to a given second control signal. And a detection circuit for detecting an output current controlled by the first switching element and the second switching element, wherein the output current is predetermined. A first operation state in which the output of the first control signal and the second control signal is stopped when the output current is larger than a predetermined threshold, and the first control signal and the second control signal when the output current is larger than the predetermined threshold. System When the control is performed in accordance with the second operation state in which signals are alternately output and the transition from the first operation state to the second operation state is performed, the unit of the first control signal and the second control signal The on-time for which the first switching element and the second switching element per time are turned on is gradually increased.

  A first switching element and a second switching element per unit time of the first control signal and the second control signal by gradually increasing the pulse widths of the first control signal and the second control signal. The on-time for turning on is gradually increased. At this time, a triangular wave generating circuit that generates a triangular wave, a time constant circuit that generates an integrated waveform of a signal in response to power-on, and a magnitude relationship between the triangular wave generated by the triangular wave generating circuit and the integrated waveform output from the time constant circuit A comparison circuit for outputting a comparison result according to the first switching element and the second switching element per unit time of the first control signal and the second control signal according to the output of the comparison circuit. The on-time for turning on is gradually increased.

  Also, by gradually increasing the frequencies of the first control signal and the second control signal, the first switching element and the second switching per unit time of the first control signal and the second control signal The on time for turning on the element is gradually increased. At this time, a triangular wave generating circuit that generates a triangular wave, a time constant circuit that generates an integrated waveform of a signal in response to power-on, and a magnitude relationship between the triangular wave generated by the triangular wave generating circuit and the integrated waveform output from the time constant circuit A comparison circuit that outputs a comparison result according to the frequency, a pulse generation circuit that outputs a pulse waveform of a constant frequency, and an AND circuit that outputs a logical product of the comparison result of the comparison circuit and the pulse waveform of the pulse generation circuit. The on-time for turning on the first switching element and the second switching element per unit time of the first control signal and the second control signal is gradually increased according to the output of the comparison circuit. To do.

  Further, according to the present invention, a voltage conversion circuit that converts an input voltage and outputs a first conversion voltage and a second conversion voltage, and a rectifier element are provided in parallel, and the first conversion voltage is applied. In addition, a first switching element that performs switching according to a given first control signal and a rectifying element are provided in parallel, a second conversion voltage is applied, and a second control signal that is given And a detection circuit for detecting an output current controlled by the first switching element and the second switching element, wherein the output current is A first operating state in which the output of the first control signal and the second control signal is stopped when the output current is larger than the predetermined threshold when the output current is larger than the predetermined threshold. The control is performed in accordance with the second operation state in which the control signals are alternately output, and when the transition from the second operation state to the first operation state is performed, the first control signal and the second control signal It is characterized in that the on-time for turning on the first switching element and the second switching element per unit time is gradually reduced.

  In the present invention, a voltage conversion circuit that converts an input voltage and outputs a first conversion voltage and a second conversion voltage, and a rectifying element are provided in parallel, and the first conversion voltage is applied. In addition, a first switching element that performs switching in accordance with a given first control signal and a rectifying element are provided in parallel, and a second conversion voltage is applied, and in response to a given second control signal. And a second switching element that performs switching, and a step of detecting an output current controlled by the first switching element and the second switching element; A step of transitioning to a first operating state in which the output of the first control signal and the second control signal is stopped when the output current is larger than a predetermined threshold; A step of transitioning to a second operation state for alternately outputting a signal and a second control signal, and a transition from the first operation state to the second operation state, the first control signal and the second control signal And a step of gradually increasing the ON time during which the first switching element and the second switching element are turned ON per unit time of the control signal.

  In the present invention, a voltage conversion circuit that converts an input voltage and outputs a first conversion voltage and a second conversion voltage, and a rectifying element are provided in parallel, and the first conversion voltage is applied. In addition, a first switching element that performs switching in accordance with a given first control signal and a rectifying element are provided in parallel, and a second conversion voltage is applied, and in response to a given second control signal. And a second switching element that performs switching, and a step of detecting an output current controlled by the first switching element and the second switching element; A step of transitioning to a first operating state in which the output of the first control signal and the second control signal is stopped when the output current is larger than a predetermined threshold; A transition to a second operating state that alternately outputs a signal and a second control signal, and a transition from the second operating state to the first operating state, the first control signal and the second control signal And a step of gradually decreasing an ON time during which the first switching element and the second switching element are turned ON per unit time of the control signal.

  As described above, according to the present invention, when the output current is smaller than the predetermined threshold, the first operation state in which the output of the first control signal and the second control signal is stopped and the output current are lower than the predetermined threshold. When the transition is made in the second operation state in which the first control signal and the second control signal are alternately output when the first control signal and the second control signal are also larger, the first per unit time of the first control signal and the second control signal By gradually changing the ON time during which the switching element and the second switching element are turned on, it is possible to smoothly switch the operating state, thereby reducing the fluctuation of the output voltage.

  FIG. 5 is a circuit diagram of a DC-DC conversion circuit according to an embodiment of the present invention. In the figure, the same components as those in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted.

  The DC-DC conversion circuit 100 of the present embodiment is different from the conventional DC-DC conversion circuit 31-i shown in FIG.

  FIG. 6 shows a block diagram of the control circuit 101.

  The control circuit 101 includes an output voltage detection circuit 111, a triangular wave generation circuit 112, a control pulse generation circuit 113, an output current detection circuit 114, a pulse modulation circuit 115, a power switch 116, a soft start circuit 117, and AND gates 118 to 121. It is said that.

  An output voltage Vout output from the output terminal Tout is applied to the output voltage detection circuit 111. The output voltage detection circuit 111 generates and outputs an analog signal corresponding to the difference between the output voltage Vout and the reference voltage Vref.

  FIG. 7 shows a circuit configuration diagram of the output voltage detection circuit 111.

  The output voltage detection circuit 111 includes an error amplifier 131 and a reference voltage source 132. In the error amplifier 131, the output voltage Vout is applied from the output terminal Tout to the inverting input terminal, and the reference voltage Vref of the reference power supply 132 is applied to the non-inverting input terminal. The error amplifier 131 outputs a signal corresponding to the difference between the output voltage Vout output from the output terminal Tout and the reference voltage Vref.

  An output signal of the output voltage detection circuit 111 is supplied to the control pulse generation circuit 113. In addition to the output of the output voltage detection circuit 111, the control pulse generation circuit 113 is supplied with a triangular wave signal from the triangular wave generation circuit 112. The control pulse generation circuit 113 generates a control pulse based on the output of the output voltage detection circuit 111 and the triangular wave signal from the triangular wave generation circuit 112.

  FIG. 8 shows a circuit configuration diagram of the control pulse generation circuit 113.

  The control pulse generation circuit 113 includes a comparator 141, a soft start circuit 142, an AND gate 143, a flip-flop 144, and NAND gates 145 and 146.

  In the comparator 141, the output signal of the output voltage detection circuit 111 is supplied to the non-inverting input terminal, and the triangular wave signal from the triangular wave generating circuit 112 is supplied to the inverting input terminal. The comparator 141 compares the output signal of the output voltage detection circuit 111 with the triangular wave signal generated by the triangular wave generation circuit 112, and the output signal level of the output voltage detection circuit 111 is greater than the triangular wave signal level generated by the triangular wave generation circuit 112. If it is larger, the output is at a high level, and if the output signal level of the output voltage detection circuit 111 is smaller than the triangular wave signal level generated by the triangular wave generation circuit 112, the output is at a low level. The output of the comparator 141 is supplied to the AND gate 143.

  The soft start circuit 142 detects the power-on of the power switch 116, and the output of the comparator 141 and the output of the soft start circuit 142 are supplied to the AND gate 143 according to the power from the power detection circuit when switching at the time of soft start. Is done. The soft start circuit 142 outputs an output signal whose pulse width gradually increases when the power is turned on.

  FIG. 9 shows a circuit configuration diagram of the soft start circuit 142.

  The soft start circuit 142 includes a triangular wave generation circuit 151, a delay circuit 152, and a comparator 153. The triangular wave generation circuit 151 generates a triangular wave signal having a frequency lower than the frequency of the triangular wave generated by the triangular wave generation circuit 112. The triangular wave signal generated by the triangular wave generating circuit 151 is supplied to the inverting input terminal of the comparator 153.

  The delay circuit 152 includes a voltage source 154, a transistor Q11, resistors R11 and R12, and a capacitor C11. The transistor Q11 is composed of an NPN transistor and is turned on when the output of the power switch 116 is at the high level, that is, when the power is turned on.

  The capacitor C11 is connected to the voltage source 61 via resistors R11 and R12 and a transistor Q11. When the transistor Q11 is turned on, current is supplied to the capacitor C11 via the resistors R11 and R12, and the capacitor C11 is charged. The charging voltage of the capacitor C11 is divided by resistors R11 and R12 and supplied to the non-inverting input terminal of the comparator 153.

  FIG. 10 shows an operation waveform diagram of the soft start switch circuit 142. 10A shows the output signal of the power switch 116, FIG. 10B shows the solid line with the voltage at the connection point between the resistor R11 and the resistor R12, the alternate long and short dash line with the output triangular wave signal of the triangular wave generating circuit 151, and FIG. Indicates the output of the comparator 153.

  When the power switch 116 is turned on at time t1 and the output signal of the power switch 116 shown in FIG. 10A rises from the low level to the high level, the potential at the connection point between the resistor R11 and the resistor R12 becomes the resistance R11, R12. It gradually increases according to the time constant determined by the capacitor C11.

  The voltage at the connection point between the resistor R11 and the resistor R12 indicated by the solid line in FIG. 10B and the triangular wave signal indicated by the alternate long and short dash line in FIG. The comparator 153 sets the output to a high level when the voltage at the connection point between the resistor R11 and the resistor R12 indicated by the solid line in FIG. 10B is larger than the triangular wave signal indicated by the dashed line in FIG. 10B. An output pulse signal whose pulse width gradually increases as shown in FIG. The output signal of the comparator 153 shown in FIG. 10C is supplied to the AND gate 143. The AND gate 143 takes an AND logic between the output of the error amplifier 141 and the output of the soft start circuit 142.

  The output of the AND gate 143 is supplied to the clock terminal CLK of the flip-flop 144. In the flip-flop 144, the clear terminal CLR and the preset terminal PR are fixed at a high level, and the non-inverted output Q and the inverted output / Q are inverted according to the rising edge of the output pulse of the AND gate 143 supplied to the clock terminal CLK. Let The non-inverted output Q of the flip-flop 144 is supplied to the NAND gate 145, and the inverted output / Q of the flip-flop 144 is supplied to the NAND gate 146.

  The NAND gate 145 takes NAND logic between the non-inverted output Q of the flip-flop 144 and the output of the error amplifier 141. The output of the NAND gate 145 is supplied to the AND gate 118. The NAND gate 146 takes NAND logic between the inverted output / Q of the flip-flop 144 and the output of the error amplifier 141. The output of the NAND gate 146 is supplied to the AND gate 119.

  The AND gate 118 outputs an AND logic between the output of the NAND gate 145 and the output of the pulse modulation circuit 115. The AND gate 119 outputs an AND logic between the output of the NAND gate 146 and the output of the pulse modulation circuit 115.

  Here, the pulse modulation circuit 115 will be described in detail.

  FIG. 11 shows a circuit configuration diagram of the pulse modulation circuit 115.

  The pulse modulation circuit 115 includes an inverter 161, transistors Q21 and Q22, a capacitor C21, a comparator 162, a current source 163, and a resistor R21. A detection signal is supplied from the output current detection circuit 114 to the pulse modulation circuit 115.

  FIG. 12 is a circuit configuration diagram of the output current detection circuit 114, and FIG. 13 is an operation waveform diagram of the pulse modulation circuit 115. 13A shows the output of the output current detection circuit 114, FIG. 13B shows the base voltage of the transistor Q21, FIG. 13C shows the base voltage of the transistor Q22, FIG. 13D shows the charging voltage of the capacitor C21, The triangular wave signal output from the triangular wave generation circuit 112 and FIG.

  The output current detection circuit 114 includes a differential amplifier 171, a comparator 172, and a reference voltage source 173.

  The differential amplifier 171 detects a potential difference between both ends of the output current detection resistor Rs. The output of the differential amplifier 171 is supplied to the inverting input terminal of the comparator 172.

  A reference voltage is applied from the reference voltage source 173 to the non-inverting input terminal of the comparator 172. The comparator 172 sets the output of the differential amplifier 171 to be lower than the reference voltage, that is, the output is high level when the load is light, and the output of the differential amplifier 171 is higher than the reference voltage, that is, the output is set to the low level when the load is heavy. To do.

  The output of the comparator 172 is supplied to the pulse modulation circuit 115. The output of the comparator 172 is supplied to the base of the NPN transistor Q22 by the pulse modulation circuit 115 and also supplied to the base of the NPN transistor Q21 via the inverter 161.

  At light load, that is, when the output of the comparator 172 is at high level, the base of the transistor Q21 is at low level and the base of the transistor Q22 is at high level, so that the transistor Q21 is turned off and the transistor Q22 is turned on.

  When the transistor Q22 is turned on, the capacitor C21 is discharged, and the non-inverting input terminal of the comparator 162 becomes low level. A triangular wave signal is supplied from the triangular wave generation circuit 112 to the inverting input terminal of the comparator 162. The comparator 162 sets the output to a low level if the triangular wave signal is larger than the charging voltage of the capacitor C21, and sets the output to a high level if the triangular wave signal is smaller than the charging voltage of the capacitor C21. When the load is light, the charging voltage of the capacitor C21 is at a low level and is smaller than the triangular wave signal, so that the output of the comparator 162 is at a low level.

  When shifting from a heavy load to a light load at time t11, the output of the comparator 172 changes from a low level to a high level as shown in FIG. At this time, the base of the transistor Q21 is changed from the high level to the low level as shown in FIG. 13B, and the base of the transistor Q22 is changed from the low level to the high level as shown in FIG. Turns off and transistor Q22 turns on.

  When the transistor Q21 is turned off and the transistor Q22 is turned on, the capacitor C21 is gradually discharged through the resistor R21. At this time, the charging voltage of the capacitor C21 changes as shown by a solid line in FIG.

  The charging voltage of the capacitor C21 is supplied to the non-inverting input terminal of the comparator 162. Therefore, the output of the comparator 162 changes so that the high level period is gradually shortened, the low level period is lengthened, and finally becomes the low level as shown in FIG.

  On the contrary, when shifting from light load to heavy load at time t12, that is, when the output of the comparator 172 changes from high level to low level as shown in FIG. 13 (A), as shown in FIG. 13 (B). Since the base of the transistor Q21 is changed from low level to high level and the base of the transistor Q22 is changed from high level to low level as shown in FIG. 13C, the transistor Q21 is turned on and the transistor Q22 is turned off.

  When the transistor Q21 is turned on and the transistor Q22 is turned off, a constant current is supplied from the current source 163 to the capacitor C21 and gradually charged. For this reason, the charging voltage of the capacitor C21 gradually increases as shown in FIG.

  Therefore, the output of the comparator 162 changes so that the low level period is gradually shortened, the high level period is lengthened, and finally becomes high level as shown in FIG.

  As described above, when shifting from a heavy load to a light load and from a light load to a heavy load, and from synchronous rectification to diode rectification and from diode rectification to synchronous rectification, the output of the comparator 162 suddenly changes from high to low level or low. The high level or low level period is gradually shortened, and the low level or high level period is gradually lengthened.

  The output of the comparator 162 is supplied to AND gates 118 and 119.

  The AND gates 118 and 119 output the AND logic of the control pulses syncA and syncB generated by the control pulse generation circuit 113 and the output of the comparator 162. That is, the AND gates 118 and 119 output the control pulses syncA and syncB generated by the control pulse generation circuit 113 while the output of the comparator 162 is at a high level.

  The output of the AND gate 118 is supplied to the AND gate 120, and the output of the AND gate 119 is supplied to the AND gate 121. The outputs of the soft start circuit 117 are supplied to the AND gates 120 and 121. The AND gate 120 outputs an AND logic between the output of the AND gate 118 and the output of the soft start circuit 117. The AND gate 121 outputs an AND logic between the output of the AND gate 119 and the soft start circuit 117.

  The soft start circuit 117 has substantially the same configuration as the soft start circuit 142 shown in FIG. 9, and the capacitance of the capacitor C11 is set larger than that of the soft start circuit 142.

  FIG. 14 shows an operation waveform diagram of the soft start circuit 117. 14A shows the output of the power switch 116, the solid line in FIG. 14B shows the charging voltage of the capacitor C11, the broken line shows a triangular wave signal, and FIG. 14C shows the output of the comparator 153.

  The soft start circuit 117 delays the rising of the charging voltage of the capacitor C11 by setting the capacitance of the capacitor C11 large. Therefore, the output of the comparator 153 is delayed by a predetermined time T10 after the power switch 116 is turned on. The output is set to the high level. At this time, as shown in FIG. 14C, the output of the comparator 153 gradually becomes longer during the high level, gradually becomes shorter during the low level, and is finally fixed at the high level.

  The AND gate 120 supplies the output of the AND gate 118 to the gate of the transistor Q1 when the output of the soft start circuit 117 is at a high level. The AND gate 121 supplies the output of the AND gate 119 to the gate of the transistor Q2 when the output of the soft start circuit 117 is at a high level.

  When the power is turned on, the outputs of the AND gates 120 and 121 are held at a low level and the transistors Q1 and Q2 are turned off until a predetermined time T10 elapses by the soft start circuit 117. Therefore, synchronous rectification is stopped by the transistors Q1 and Q2, and power is supplied by diode rectification by the diodes D11 and D12.

  Since the diode rectification is performed by the diodes D11 and D12 for a predetermined time T10 when the power is turned on, the power supply to the load is made redundant before the output voltage Vout output from the output terminal Tout sufficiently rises. Even if the output voltage rises, the diodes D11 and D12 are connected in the reverse direction, so that the current can be prevented from flowing backward in the transformer 42. Therefore, the diodes D1 and D2 connected between the load and the DC-DC conversion circuits 31-1 and 31-2 in FIG. 2 are not necessary. Therefore, the circuit configuration can be simplified and the manufacturing cost can be reduced.

  Further, after a predetermined time T10 has elapsed, the soft start circuit 117 and the AND gates 120 and 121 are gradually switched to synchronous rectification. For this reason, even if the on-voltages of the diodes D11 and D12 and the on-voltages of the transistors Q1 and Q2 are largely different, the diode rectification and the synchronous rectification are gradually switched. Since this can be done, the influence on the output voltage Vout can be reduced. Further, since the influence on the output voltage Vout is small, the choke coil L1 and the smoothing capacitor C0 can be reduced.

  Further, the pulse modulation circuit 115 according to the present embodiment smoothly switches the rectification method by gradually changing the pulse width of the output signal when switching from diode rectification to synchronous rectification or from synchronous rectification to diode rectification. However, the pulse frequency may be gradually changed.

  FIG. 15 shows a circuit configuration diagram of a first modification of the pulse modulation circuit 115. In the figure, the same components as those in FIG.

  The pulse modulation circuit 115 of this modification has a configuration in which a frequency modulation circuit 200 is provided instead of the comparator 162. The frequency modulation circuit 200 includes a comparator 201, a triangular wave generation circuit 202, and an AND gate 203.

  FIG. 16 shows an operation waveform diagram of the first modification of the pulse modulation circuit 115. 16A shows the output of the output current detection circuit 114, FIG. 16B shows the base voltage of the transistor Q21, FIG. 16C shows the base voltage of the transistor Q22, and the solid line shown in FIG. 16D shows the capacitor C21. FIG. 16F shows the output voltage of the comparator 141 of the control pulse generation circuit 113, and FIG. 16G shows the output of the AND gate 203.

  In the comparator 201, the charging voltage of the capacitor C21 is applied to the non-inverting input terminal, and the output triangular wave signal of the triangular wave generating circuit 202 is supplied to the inverting input terminal.

  When the light load changes to the heavy load, the output from the output current detection circuit 114 shown in FIG. 16A changes from the high level to the low level. When the output of the output current detection circuit 114 becomes low level, the base voltage of the transistor Q21 becomes high level as shown in FIG. 16B, and the transistor Q21 is turned on. When the output of the output current detection circuit 114 becomes low level, as shown in FIG. 16C, the base voltage of the transistor Q22 becomes low level, and the transistor Q22 is turned off.

  When the transistor Q21 is turned on, the capacitor C21 is charged by the current source 153, and the charging voltage of the capacitor C21 increases as shown by the solid line in FIG. The charging voltage of the capacitor C 21 is compared with the output triangular wave signal of the triangular wave generating circuit 202 by the comparator 201. Note that the frequency of the output triangular wave signal of the triangular wave generation circuit 202 is set to a frequency sufficiently lower than the frequency of the output triangular wave signal of the triangular wave generation circuit 112.

  As shown in FIG. 16E, the comparator 201 outputs a signal that becomes high level when the charging voltage of the capacitor C21 is larger than the output triangular wave signal of the triangular wave generation circuit 202, and becomes low level when it is small. The output of the comparator 201 is supplied to the AND gate 203. The AND gate 203 outputs an AND logic between the output of the comparator 201 and the output of the comparator 141 of the control pulse generation circuit 113 shown in FIG. The AND gate 203 outputs the output signal of the comparator 141 of the control pulse generation circuit 113 shown in FIG. 16 (F) while the comparator 201 is at a high level as shown in FIG. 16 (G). When shifting from a light load to a heavy load, the high level period of the comparator 201 gradually increases, and the number of output pulses of the comparator 141 of the control pulse generation circuit 113 output from the AND gate 203 increases. That is, the frequency rises, and finally the output of the AND gate 203 becomes the output itself of the comparator 141 of the control pulse generation circuit 113.

  Similarly, when shifting from a heavy load to a light load, the high level period of the comparator 201 is gradually shortened, and the number of output pulses of the comparator 141 of the control pulse generation circuit 113 output from the AND gate 203 is gradually decreased. . That is, the frequency is lowered, and the output of the AND gate 203 is finally held at a low level.

  As described above, since the pulse can be gradually supplied to the gates of the transistors Q1 and Q2 when shifting from a light load to a heavy load and from a heavy load to a light load, a smooth transition is made from diode rectification to synchronous rectification and from synchronous rectification to diode rectification. Can be made.

  In this embodiment, the transition from the heavy load to the light load, that is, the transition from the synchronous rectification to the diode rectification is performed gradually. However, when the load is light, there is a risk that current flows backward from the load side. There is. For this reason, when shifting from a heavy load to a light load, that is, when switching from synchronous rectification to diode rectification, the transition may be made immediately.

  FIG. 17 shows a circuit configuration diagram of a second modification of the pulse modulation circuit 115. In the figure, the same components as those in FIG. 11 are denoted by the same reference numerals, and the description thereof is omitted. FIG. 18 shows an operation waveform diagram of the second modification of the pulse modulation circuit 115.

  The pulse modulation circuit 115 of the present modification is configured such that the resistor R21 that limits the discharge current of the capacitor C21 is omitted. As a result, when the transistor Q22 is turned on at time t11 in FIG. 18, the capacitor C21 is immediately discharged as shown in FIG. 18D, and the charging voltage of the capacitor C21 rapidly decreases. Thereby, as shown in FIG. 18E, the output of the comparator 164 is immediately fixed to the low level.

  When the output of the comparator 164 is fixed at a low level, the diode rectification is immediately started. By shifting to the diode rectification, the diodes D1 and D2 are connected in the reverse direction with respect to the load, so that the backflow of the current from the load side can be prevented.

  In this embodiment, the output current is detected by detecting the voltage across the output current detection resistor Rs. However, the output current is detected by detecting the counter electromotive force generated in the secondary coils L21 and L22. May be detected.

  FIG. 19 is a circuit diagram showing a modification of the embodiment of the present invention. In the figure, the same components as those in FIG.

  The DC-DC conversion circuit 300 of the present modification is configured such that the configuration of the control circuit 301 is different from that of the DC-DC control circuit 100 and the current detection resistor Rs is omitted.

  FIG. 20 shows a block diagram of the control circuit 301. In the figure, the same components as those in FIG. 6 are denoted by the same reference numerals, and the description thereof is omitted.

  The control circuit 301 of this modification is different from the control circuit 101 shown in FIG. 6 in the configuration of the output current detection circuit 311. The control circuit 301 is supplied with the voltage at the connection point between the secondary coil L21 and the secondary coil L22, and also supplied with the output of the AND gate 120.

  FIG. 21 is a circuit configuration diagram of the output current detection circuit 311.

  The output current detection circuit 311 includes a comparator 321, a reference voltage source 322, an AND gate 323, and a latch circuit 324.

  The voltage VT at the connection point between the secondary coil L21 and the secondary coil L22 is connected to the non-inverting input terminal of the comparator 321. The reference voltage Vref from the reference voltage source 322 is applied to the inverting input terminal of the comparator 321. The comparator 321 compares the voltage VT at the connection point between the secondary coil L21 and the secondary coil L22 with the reference voltage Vref generated by the reference voltage source 322, and connects the connection point between the secondary coil L21 and the secondary coil L22. Is lower than the reference voltage generated by the reference voltage source 322, the output is set to the low level, and the voltage at the connection point between the secondary coil L21 and the secondary coil L22 is the reference voltage generated by the reference voltage source 322. If it is larger than Vref, the output is set to high level.

  The output of the comparator 321 is supplied as an inhibit to the AND gate 323. The AND gate 323 gates the output of the AND gate 120 according to the inhibit pulse from the comparator 321. The output of the AND gate 120 is supplied to the latch circuit 324. The latch circuit 324 latches the output of the AND gate 323.

  FIG. 22 shows an operation waveform diagram of the output current detection circuit 311. 22A shows the output of the AND gate 120, FIG. 22B shows the voltage VT at the connection point between the secondary coil L21 and the secondary coil L22, and FIG. 22C shows the output of the latch circuit 324.

  When a current flows into the secondary coil L21 from the load side at time t20, that is, when a reverse flow occurs, the voltage VT at the connection point between the secondary coil L21 and the secondary coil L22 is normal when the transistor Q21 is turned on. It is lower than the voltage V0.

  When the voltage VT at the connection point between the secondary coil L21 and the secondary coil L22 falls below the reference voltage Vref, the output of the comparator 321 becomes low level. When the output of the comparator 321 becomes low level and the output of the AND gate 120 becomes high level at time t21, the output of the AND gate 323 becomes high level. The latch circuit 324 latches the high level at time t21 and outputs it. To high level.

  The output of the latch circuit 324 is supplied to the pulse modulation circuit 115 as the output of the output current detection circuit 311 and used for the operation when switching between synchronous rectification and diode rectification as described above.

  In the above embodiment, the example in which the present invention is applied to the isolated DC-DC conversion circuit has been described. However, the present invention can be applied to other circuit types, for example, a step-down DC-DC conversion circuit.

  FIG. 23 shows a circuit configuration diagram of a DC-DC conversion circuit according to another embodiment of the present invention. In the figure, the same components as those in FIG.

  In the DC-DC conversion circuit 400 of this embodiment, a DC voltage is applied to the transistors Q101 and Q102 whose drain and source are connected in series. A diode D100 is connected in parallel to the drain-source of the transistor Q102. A connection point between the transistor Q101 and the transistor Q102 is connected to the output terminal Tout via the choke coil L0 and the output current detection resistor Rs. A smoothing capacitor C0 is connected between the output terminal Tout and the ground terminal Tgnd.

  The transistors Q101 and Q102 are controlled by the control circuit 401. The control circuit 401 detects the output current flowing out from the output terminal Tout by the output current detection resistor Rs, and also detects the output voltage at the output terminal Tout to control the transistors Q101 and Q102.

  FIG. 24 shows a block diagram of the control circuit 401. In the figure, the same components as those in FIG. 11 are denoted by the same reference numerals, and the description thereof is omitted.

  The control circuit 401 is different from the control circuit 101 in the configuration of the control pulse generation circuit 411.

  FIG. 25 shows a circuit configuration diagram of the control pulse generation circuit 411. In the figure, the same components as those in FIG. 8 are denoted by the same reference numerals, and the description thereof is omitted.

  The control pulse generation circuit 411 is configured by deleting the flip-flop 144 and the AND gates 145 and 146 from the control pulse generation circuit 113 shown in FIG. 8, and outputs the output of the AND gate 143 as a control pulse.

  The output control pulse output from the control pulse generation circuit 411 is inverted by the inverter 412 and supplied to the gate of the transistor Q101. The output control pulse output from the AND gate 143 is supplied to the AND gate 119. The AND gate 119 outputs an AND logic of the output generation pulse output from the control pulse generation circuit 411 and the modulation pulse from the pulse modulation circuit 115.

  The output of the AND gate 119 is supplied to the AND gate 121. The AND gate 121 outputs an AND logic of the output from the AND gate 119 and the output of the soft start circuit 117. The output of the AND gate 119 is supplied to the gate of the transistor Q102.

  According to this embodiment, at light load, the transistor Q102 is turned off and diode rectification by the diode D100 is performed. In heavy load, synchronous rectification is performed by switching the transistor Q102 in a phase opposite to that of the transistor Q101.

  A light load and a heavy load are identified based on the detection result of the output current detection circuit 114, and switching between diode rectification and synchronous rectification is performed. According to the present embodiment, when switching from synchronous rectification to diode rectification, the pulse modulation circuit 115 gradually increases the switching interval or number of times of the transistor Q102, is finally turned off, and is gradually switched to diode rectification. Further, when switching from diode rectification to synchronous rectification, the pulse modulation circuit 115 gradually reduces the switching interval or number of times from the OFF state of the transistor Q102, and is finally controlled by the control pulse generated by the control pulse generation circuit 311. By doing so, it is gradually switched from diode rectification to synchronous rectification.

  For this reason, it is possible to reduce fluctuations in the output voltage Vout due to the difference in on-voltage between the transistor Q102 and the diode D100, which occurs when switching between synchronous rectification and diode rectification.

  The soft start circuit 117 can prevent backflow from the load side by gradually switching to synchronous rectification after diode rectification for a certain time T10 at the time of start-up.

  In the above-described embodiment, the example in which the output current is provided to the power supply circuit that detects the resistance has been described. However, the present invention is not limited to this, and it is essential that the output current can be detected. The detection method is not limited.

  In addition, this invention is not limited to the said Example, It cannot be overemphasized that a various modified example can be considered in the range which does not deviate from the summary of this invention.

It is a block block diagram of an information processing system. It is a block block diagram of the DC-DC conversion part 21-1. It is a block block diagram of the DC-DC conversion circuit 31-1. It is an output voltage waveform figure of the conventional power supply device. It is a circuit block diagram of the DC-DC conversion circuit of one Example of this invention. 2 is a block configuration diagram of a control circuit 101. FIG. 2 is a circuit configuration diagram of an output voltage detection circuit 111. FIG. 3 is a circuit configuration diagram of a control pulse generation circuit 113. FIG. 3 is a circuit configuration diagram of a soft start circuit 142. FIG. 6 is an operation waveform diagram of the soft start switch circuit 142. FIG. 2 is a circuit configuration diagram of a pulse modulation circuit 115. FIG. 3 is a circuit configuration diagram of an output current detection circuit 114. FIG. 6 is an operation waveform diagram of a pulse modulation circuit 115. FIG. 7 is an operation waveform diagram of the soft start circuit 117. FIG. FIG. 10 is a circuit configuration diagram of a first modification of the pulse modulation circuit 115. 6 is an operation waveform diagram of a first modification of the pulse modulation circuit 115. FIG. FIG. 10 is a circuit configuration diagram of a second modification of the pulse modulation circuit 115. FIG. 10 is an operation waveform diagram of a second modification of the pulse modulation circuit 115. It is a circuit block diagram of the modification of one Example of this invention. 2 is a block configuration diagram of a control circuit 301. FIG. 3 is a circuit configuration diagram of an output current detection circuit 311. FIG. 6 is an operation waveform diagram of the output current detection circuit 311. FIG. It is a circuit block diagram of the DC-DC conversion circuit of the other Example of this invention. 2 is a block configuration diagram of a control circuit 401. FIG. 3 is a circuit configuration diagram of a control pulse generation circuit 411. FIG.

Explanation of symbols

41, 161, 412 Inverter 42 Transformer 100, 300, 400 DC-DC conversion circuit 101, 301, 401 Control circuit 111 Output voltage detection circuit 112, 151, 201 Triangular wave generation circuit 113, 411 Control pulse generation circuit 114, 311 Output current Detection circuit 115 Pulse modulation circuit 116 Power switch 117, 142 Soft start circuit 118-121, 143, 203, 323 AND gate 131 Error amplifier 132, 154, 173 Reference voltage source 141, 153, 162, 172, 321 Comparator 144 Flip-flop 145, 146 NAND gate 152 Delay circuit 163 Current source 171 Error amplifier 200 Frequency modulation circuit 324 Latch circuit L1 Primary coil L21, L22 Secondary coil Q1, Q2 Transistors D11, D12 L0 Choke coil C0 Smoothing capacitor Rs Output current detection resistor

Claims (14)

A voltage conversion circuit that converts an input voltage and outputs a first conversion voltage and a second conversion voltage;
A first switching element provided with a rectifying element in parallel, to which the first conversion voltage is applied and which performs switching according to a given first control signal;
A second switching element provided with a rectifying element in parallel, to which the second conversion voltage is applied, and for switching according to a second control signal applied;
A detection circuit for detecting an output current controlled by the first switching element and the second switching element;
A first operating state in which the output of the first control signal and the second control signal is stopped when the output current is smaller than a predetermined threshold; and the output current is larger than a predetermined threshold. When the control is performed by the second operation state in which the first control signal and the second control signal are alternately output, and the transition from the first operation state to the second operation state is performed. And a control circuit for gradually increasing an ON time during which the first switching element and the second switching element are turned on per unit time of the first control signal and the second control signal. Power supply. The control circuit gradually increases the pulse widths of the first control signal and the second control signal, thereby the first control signal and the second control signal per unit time. 2. The power supply device according to claim 1, wherein an ON time during which the switching element and the second switching element are turned on is gradually increased. The control circuit includes a triangular wave generating circuit that generates a triangular wave;
A time constant circuit that generates an integrated waveform of the signal in response to power-on,
A comparison circuit that outputs a comparison result according to the magnitude relationship between the triangular wave generated by the triangular wave generation circuit and the integrated waveform output from the time constant circuit;
The ON time for turning on the first switching element and the second switching element per unit time of the first control signal and the second control signal is gradually increased according to the output of the comparison circuit. The power supply device according to claim 2. The control circuit gradually increases the frequencies of the first control signal and the second control signal to thereby increase the first control signal per unit time of the first control signal and the second control signal. 2. The power supply device according to claim 1, wherein an on-time for turning on the switching element and the second switching element is gradually increased. The control circuit includes a triangular wave generating circuit that generates a triangular wave;
A time constant circuit that generates an integrated waveform of the signal in response to power-on,
A comparison circuit that outputs a comparison result according to the magnitude relationship between the triangular wave generated by the triangular wave generation circuit and the integrated waveform output from the time constant circuit;
A pulse generation circuit that outputs a pulse waveform of a constant frequency;
A logical product circuit that outputs a logical product of the comparison result of the comparison circuit and the pulse waveform of the pulse generation circuit;
The ON time for turning on the first switching element and the second switching element per unit time of the first control signal and the second control signal is gradually increased according to the output of the comparison circuit. The power supply device according to claim 4. A voltage conversion circuit that converts an input voltage and outputs a first conversion voltage and a second conversion voltage;
A first switching element provided with a rectifying element in parallel, to which the first conversion voltage is applied and which performs switching according to a given first control signal;
A second switching element provided with a rectifying element in parallel, to which the second conversion voltage is applied, and for switching according to a second control signal applied;
A detection circuit for detecting an output current controlled by the first switching element and the second switching element;
A first operating state in which the output of the first control signal and the second control signal is stopped when the output current is smaller than a predetermined threshold; and the output current is larger than a predetermined threshold. When the control is performed by the second operation state in which the first control signal and the second control signal are alternately output, and the transition from the second operation state to the first operation state is performed. And a control circuit for gradually decreasing an on-time for turning on the first switching element and the second switching element per unit time of the first control signal and the second control signal. Power supply. A voltage conversion circuit that converts an input voltage and outputs a first conversion voltage and a second conversion voltage, and a rectifying element are provided in parallel, and the first conversion voltage is applied and applied. A first switching element that performs switching in accordance with a control signal of 1 and a rectifying element are provided in parallel, and the second conversion voltage is applied and switching is performed in accordance with a given second control signal. A control circuit for a power supply device comprising: a second switching element; and a detection circuit that detects an output current controlled by the first switching element and the second switching element,
A first operating state in which the output of the first control signal and the second control signal is stopped when the output current is smaller than a predetermined threshold; and the output current is larger than a predetermined threshold. When the control is performed by the second operation state in which the first control signal and the second control signal are alternately output, and the transition from the first operation state to the second operation state is performed. A control circuit characterized by gradually increasing an on-time for turning on the first switching element and the second switching element per unit time of the first control signal and the second control signal. By gradually increasing the pulse widths of the first control signal and the second control signal, the first switching element and the first control element per unit time of the first control signal and the second control signal 8. The control circuit according to claim 7, wherein an ON time during which the second switching element is turned on is gradually increased. A triangular wave generating circuit for generating a triangular wave;
A time constant circuit that generates an integrated waveform of the signal in response to power-on,
A comparison circuit that outputs a comparison result according to the magnitude relationship between the triangular wave generated by the triangular wave generation circuit and the integrated waveform output from the time constant circuit;
The ON time for turning on the first switching element and the second switching element per unit time of the first control signal and the second control signal is gradually increased according to the output of the comparison circuit. The control circuit according to claim 8. By gradually increasing the frequency of the first control signal and the second control signal, the first switching element and the second control unit per unit time of the first control signal and the second control signal 8. The control circuit according to claim 7, wherein an on-time for turning on the two switching elements is gradually increased. A triangular wave generating circuit for generating a triangular wave;
A time constant circuit that generates an integrated waveform of the signal in response to power-on,
A comparison circuit that outputs a comparison result according to the magnitude relationship between the triangular wave generated by the triangular wave generation circuit and the integrated waveform output from the time constant circuit;
A pulse generation circuit that outputs a pulse waveform of a constant frequency;
A logical product circuit that outputs a logical product of the comparison result of the comparison circuit and the pulse waveform of the pulse generation circuit;
The ON time for turning on the first switching element and the second switching element per unit time of the first control signal and the second control signal is gradually increased according to the output of the comparison circuit. The power supply device according to claim 10. A voltage conversion circuit that converts an input voltage and outputs a first conversion voltage and a second conversion voltage, and a rectifying element are provided in parallel, and the first conversion voltage is applied and applied. A first switching element that performs switching in accordance with a control signal of 1 and a rectifying element are provided in parallel, and the second conversion voltage is applied and switching is performed in accordance with a given second control signal. A second switching element;
A control circuit for a power supply device comprising a detection circuit for detecting an output current controlled by the first switching element and the second switching element,
A first operating state in which the output of the first control signal and the second control signal is stopped when the output current is smaller than a predetermined threshold; and the output current is larger than a predetermined threshold. When the control is performed by the second operation state in which the first control signal and the second control signal are alternately output, and the transition from the second operation state to the first operation state is performed. A control circuit characterized by gradually decreasing an on-time for turning on the first switching element and the second switching element per unit time of the first control signal and the second control signal. A voltage conversion circuit that converts an input voltage and outputs a first conversion voltage and a second conversion voltage, and a rectifying element are provided in parallel, and the first conversion voltage is applied and applied. A first switching element that performs switching in accordance with a control signal of 1 and a rectifying element are provided in parallel, and the second conversion voltage is applied and switching is performed in accordance with a given second control signal. A control method for a power supply device comprising a second switching element,
Detecting an output current controlled by the first switching element and the second switching element;
Transition to a first operating state in which the output of the first control signal and the second control signal is stopped when the output current is smaller than a predetermined threshold;
Transition to a second operating state in which the first control signal and the second control signal are alternately output when the output current is greater than a predetermined threshold;
When transitioning from the first operating state to the second operating state, the first switching element and the second switching per unit time of the first control signal and the second control signal And a step of gradually increasing an on time during which the element is turned on. A voltage conversion circuit that converts an input voltage and outputs a first conversion voltage and a second conversion voltage, and a rectifying element are provided in parallel, and the first conversion voltage is applied and applied. A first switching element that performs switching in accordance with a control signal of 1 and a rectifying element are provided in parallel, and the second conversion voltage is applied and switching is performed in accordance with a given second control signal. A control method for a power supply device comprising a second switching element,
Detecting an output current controlled by the first switching element and the second switching element;
Transition to a first operating state in which the output of the first control signal and the second control signal is stopped when the output current is smaller than a predetermined threshold;
Transition to a second operating state in which the first control signal and the second control signal are alternately output when the output current is greater than a predetermined threshold;
When the transition from the second operation state to the first operation state is performed, the first switching element and the second switching per unit time of the first control signal and the second control signal And a step of gradually decreasing an on-time during which the element is turned on.

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