JP2005261145A - Switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching power supply capable of widening the input voltage range, by suppressing unstable operation due to on-duty. <P>SOLUTION: The switching power supply is provided with a control means for amplifying the error between the output voltage from a power supply circuit and a reference voltage, comparing an error amplified signal with the amplitude of a triangular waveform obtained from a filter circuit 21 formed in the power supply circuit and outputting it to a rectifying switch S1, and fixing the on timing of a rectifying switch S1 with a clock signal, by delivering the error amplification signal thereto. An auxiliary switch S3 and a discharge resistor R<SB>D</SB>are connected in series so as to constitute a discharge circuit 31 which is connected in parallel with the resistor R<SB>SAW</SB>of a filter circuit 21. The auxiliary switch is turned on at the on timing of a commutation switch S2 to feed a discharge current to the discharge resistor R<SB>D</SB>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a switching power supply including control means for increasing the response speed of sudden load change.

Conventionally, as a representative example of a switching waveform control means, there is a current mode type PWM control as shown in FIG. 7 (see, for example, Patent Document 1). In this current mode PWM control, an error amplifier is connected to the output side of the power supply circuit to amplify an error between the detection voltage and the reference voltage, and the output of the error amplifier is input to one input of the comparator 12. The current detection circuit 27 is connected to the other input of the comparator 12 to control the choke current of the power supply circuit.
U.S. Pat. No. 4,943,902

  However, in this current mode PWM control, the choke current signal is used instead of the fixed frequency triangular wave, so that a large phase margin with the error amplification signal can be obtained, but the frequency band of the error amplification signal is greatly increased. I can't.

Due to the above problems, as shown in FIG. 8, the output of the error amplifier 11 that amplifies the error between the detected voltage and the reference voltage is connected to the two comparators 12 and 13, and one comparator is connected. 12 is directly connected to the other comparator 13 via dividing resistors R3 and R4, and includes a resistor R _SAW1 and capacitors C _SAW1 and C _SAW2 in parallel with the commutation switch S2 provided in the power supply circuit. The filter circuit 21 is connected, the output of the filter circuit 21 is connected to the other input of the two comparators 12 and 13, and the amplitude of the triangular waveform obtained from the filter circuit 21 is one of the first comparator 12. Has invented a switching power supply having a control means for controlling the input level so as to be within one input level of the second comparator 13 (see Patent Document 2).
Japanese Patent Application No. 2002-270327

  However, since this method has a variable oscillation frequency, it may be difficult to prevent switching noise generated from the power source. As an example, when the device side is a circuit sensitive to noise, the noise is attenuated by using a normal filter circuit. However, when the oscillation frequency varies as in the above embodiment, the noise is caused by deviation from the set frequency. There is a risk of malfunction without attenuation. In addition, there is a problem that multi-phase operation for increasing current is difficult. A load device that requires a high-speed response is also required to have a large current at the same time, and in order to respond to this, it is common to make it multi-phase, but if the oscillation frequency is variable, the signal of the phase shifted It is difficult to generate.

Therefore, in order to solve the above problem, as shown in FIG. 9, the error between the output voltage of the power supply circuit and the reference voltage is amplified, and this error amplified signal is compared with the triangular waveform obtained from the filter circuit 21. Thus, a switching power supply was invented that outputs a comparison signal to the rectifying switch S1 and fixes the ON timing of the rectifying switch S1 with a clock signal (see Patent Document 3).
Japanese Patent Application No. 2003-423925

  However, in such control, when the on-timing is fixed, the operation becomes unstable when the on-duty exceeds 50%, as shown in FIG. For this reason, when the input voltage range of the power supply was wide, the subject that unstable operation generate | occur | produced arose.

  The present invention has been made in view of the above problems, and provides a switching power supply capable of suppressing unstable operation due to on-duty and widening an input voltage range.

  In order to solve the above problems, a switching power supply according to the present invention includes a rectifier switch, a commutation switch, and a filter circuit in which a resistor and a capacitor are connected in parallel with the commutation switch. The input of the error amplifier is connected to amplify the error between the detection voltage and the reference voltage, and the output signal of the error amplifier is compared with the amplitude of the triangular waveform obtained from the filter circuit by the first comparator. A comparison signal is output, and the output of the error amplifier is divided by a dividing resistor, and the amplitude of the triangular waveform obtained from the filter circuit is compared with a second comparator to output a second comparison signal. The second comparison signal is combined with the clock signal, and the second comparison signal is output when the load suddenly changes, and the output signal to the rectifier switch is switched from the clock signal to the second comparison signal. Control means for controlling the amplitude of the triangular waveform to fall between the error amplification signal and the divided voltage signal, and controlling the rectifying switch ON timing to be fixed by the clock signal in a steady state. In the switching power supply provided, an auxiliary switch and a discharge resistor are connected in series to form a discharge circuit. This discharge circuit is connected in parallel with the resistor of the filter circuit, and the auxiliary switch is turned on when the commutation switch is turned on. The switch is turned on so that a discharge current flows through the discharge resistor.

  A rectifier switch, a commutation switch, and a filter circuit in which a resistor and a capacitor are connected are provided in parallel with the commutation switch, and an input of an error amplifier is connected to the output side of the power supply circuit to detect a reference voltage and a reference voltage. The error amplifier output signal is compared with the amplitude of the triangular waveform obtained from the filter circuit by a comparator, and a comparison signal is output to the rectifier switch. In a switching power supply provided with control means for controlling to be fixed by a signal, an auxiliary switch and a discharge resistor are connected in series to form a discharge circuit, and this discharge circuit is connected in parallel with the resistor of the filter circuit. The auxiliary switch is turned on when the commutation switch is turned on, and a discharge current is caused to flow through the discharge resistor. .

  The auxiliary switch is constituted by a diode, and an anode of the diode is connected to the discharge resistor.

  According to the present invention, the auxiliary switch is turned on at the turn-on timing of the commutation switch, and the discharge current is caused to flow through the discharge resistor, thereby suppressing the unstable operation due to the on-duty and widening the input voltage range. There is an effect that can be done.

  Embodiments according to the present invention will now be described with reference to the accompanying drawings. FIG. 1 shows an embodiment of a switching power supply according to the present invention. C is a capacitor, S is a switching element, R is a resistor, 11 is an error amplifier, 12 and 13 are comparators, 14 is an OR circuit, 16 is a flip-flop circuit, 17 is a driver, 21 is a filter circuit, and 31 is a discharge circuit is there.

Switching power supply according to this embodiment, the rectifier switches S1, commutation switch S2, output choke L1 and includes a smoothing capacitor C _OUT, are provided with a power supply circuit connected to the output choke L1 and smoothing capacitor C _OUT in series. A control circuit is connected to the output side of the power supply circuit. The output of this control circuit is connected to a rectifying switch S1 and a commutation switch S2.

Voltage detection resistors R ₁ and R ₂ are provided on the output side of the power supply circuit, and a connection portion of these resistors R ₁ and R ₂ is connected to the negative input of the error amplifier 11. An error with the voltage is amplified and an error amplified signal is output. The output of the error amplifier 11 is connected to the negative input of the first comparator 12, and the output of the error amplifier 11 is also connected to the positive input of the second comparator 13 via the dividing resistors R3 and R4. A partial pressure signal is output.

A filter circuit 21 configured by connecting a resistor R _SAW and a capacitor C _SAW in series is connected in parallel with the series circuit of the output choke L1 and the smoothing capacitor C _OUT . The output of the filter circuit 21 is connected to the positive input of the first comparator 12 and the negative input of the second comparator 13.

  The output of the first comparator 12 is connected to the input on the reset side of the flip-flop circuit 16 so as to output the first comparison signal. Further, the output of the second comparator 13 is connected to one input of the OR circuit 14 to output a second comparison signal. The clock signal is input to the other input of the OR circuit 14, and the output of the OR circuit 14 is connected to the set side of the flip-flop circuit 16, so that the clock signal is steady when the load is suddenly changed, and the second comparison is performed. Each signal is output. The output of the flip-flop circuit 16 is connected to the input of the driver 17, the output of the driver 17 is connected to the control terminals of the rectifier switch S1 and the commutation switch S2, and the amplitude of the triangular waveform obtained from the filter circuit 21 changes suddenly in load. In some cases, the control is performed so that the error amplification signal and the divided voltage signal fall within the range, and the ON timing of the rectifying switch S1 is controlled to be fixed by the clock signal in a steady state.

Further, in the present invention, the discharge circuit 31 is configured by connecting the auxiliary switch S3 and the discharge resistor _RD in series. The discharge circuit 31 is connected in parallel with the resistor R _SAW of the filter circuit 21, and the discharge resistor _RD is connected to the capacitor C _SAW of the filter circuit 21, and the auxiliary switch S 3 is turned on when the commutation switch S 2 is turned on. Thus, a discharge current is caused to flow through the discharge resistor _RD .

  The switching power supply configured as described above operates as follows. FIG. 2 shows an operation waveform diagram in this embodiment, the upper side shows a clock signal, and the lower side shows an error amplification output outputted from the error amplifier 11 and a triangular waveform outputted from the filter circuit 21, respectively. is there.

First, the operation when the rectifying switch S1 is turned on will be described. As shown in the upper diagram of FIG. 2, the rectifier switch S <b> 1 is turned on when the clock signal is input to the set side of the flip-flop circuit 16 via the OR circuit 14. Since the signal output from the flip-flop circuit 16 is inverted by the driver 17 and output to the commutation switch S2, the commutation switch S2 is turned off at the same time as the rectification switch S1 is turned on. The auxiliary switch S3 is also turned off at the timing when the commutation switch S2 is turned off. Therefore, the capacitor C _SAW constituting the filter circuit 21 is charged, and the output voltage from the filter circuit 21 increases as shown in the lower diagram of FIG.

  When the rectifier switch S1 is turned on, an output voltage is generated, and the error amplifier 11 connected to the output outputs an error amplification signal. This error amplified signal is compared with the triangular waveform generated by the filter circuit 21 connected in parallel with the commutation switch S2, and when the triangular waveform becomes larger than the error amplified signal, it is input to the reset side of the flip-flop circuit 16. As a result, the rectification switch S1 is turned off.

  Next, the operation when the rectifying switch S1 is turned off will be described. When the triangular waveform becomes larger than the error amplification signal, the rectification switch S1 is turned off by being input to the reset side of the flip-flop circuit 16. Since the signal output from the flip-flop circuit 16 is inverted by the driver 17 and output to the commutation switch S2, the commutation switch S2 is turned on simultaneously with the rectification switch S1 being turned off. The auxiliary switch S3 is also turned on at the timing when the commutation switch S2 is turned on. Thereby, the discharge current flows not only from the filter circuit 21 but also from the discharge circuit 31 connected in parallel thereto. Therefore, the output voltage from the filter circuit 21 drops as shown in the lower diagram of FIG.

  Thereafter, as shown in the upper diagram of FIG. 2, the rectifier switch S <b> 1 is turned on when the clock signal is input to the set side of the flip-flop circuit 16 via the OR circuit 14. The above operation is repeated. The unstable state when the on-duty is 50% or more is caused by the fact that the voltage level of the triangular wave at the on timing of the fixed clock cannot be lowered to a predetermined voltage. In this embodiment, the filter circuit 21 The triangular waveform generated by the sine wave has a larger downward slope than the conventional example, and the voltage level of the triangular wave at the fixed clock on-timing is lower under the same input / output conditions. The input voltage range can be widened.

FIG. 3 shows a switching power supply different from the above embodiment. As in the embodiment shown in FIG. 1, the switching power supply according to this embodiment includes the rectifying switch S1, the commutation switch S2, the output choke L1, and the smoothing capacitor _COUT , and the output choke L1. and it is provided with a power supply circuit connected in series and a smoothing capacitor C _OUT. A control circuit is connected to the output side of the power supply circuit. The output of this control circuit is connected to a rectifying switch S1 and a commutation switch S2.

Voltage detection resistors R ₁ and R ₂ are provided on the output side of the power supply circuit, and a connection portion of these resistors R ₁ and R ₂ is connected to the negative input of the error amplifier 11. An error with the voltage is amplified and an error amplified signal is output. The output of the error amplifier 11 is connected to the negative input of the comparator 12.

A filter circuit 21 configured by connecting a resistor R _SAW and a capacitor C _SAW in series is connected in parallel with the series circuit of the output choke L1 and the smoothing capacitor C _OUT . The output of the filter circuit 21 is connected to the positive input of the comparator 12.

  The output of the comparator 12 is connected to the input on the reset side of the flip-flop circuit 16 so as to output the first comparison signal. Further, the clock signal is connected to the set side of the flip-flop circuit 16 so as to output the clock signal. The output of the flip-flop circuit 16 is connected to the input of the driver 17, the output of the driver 17 is connected to the control terminals of the rectifier switch S1 and the commutation switch S2, and the triangular waveform and error amplification signal obtained from the filter circuit 21 are connected. Are compared, and a comparison signal is output to control the rectifying switch S1 to be turned on with the clock signal.

Further, in this embodiment, the discharge circuit 31 is configured by connecting the auxiliary switch S3 and the discharge resistor _RD in series. The discharge circuit 31 is connected in parallel with the resistor R _SAW of the filter circuit 21, and the discharge resistor _RD is connected to the capacitor C _SAW of the filter circuit 21, and the auxiliary switch S 3 is turned on when the commutation switch S 2 is turned on. Thus, a discharge current is caused to flow through the discharge resistor _RD .

  The switching power supply configured as described above operates in substantially the same manner as the embodiment shown in FIG. However, this embodiment differs from the embodiment shown in FIG. 1 in that there is no second comparator 13 shown in the embodiment shown in FIG. 1, and therefore the second comparison signal and clock signal output from the second comparator 13 are omitted. The error amplified signal is compared with the triangular waveform obtained from the filter circuit 21 and the comparison signal is output to the rectifying switch S1, and the ON timing of the rectifying switch S1 is fixed by the clock signal. In the following embodiments, it is possible to have a configuration in which the ON timing of the rectifying switch S1 is fixed by a clock signal as in the above embodiments.

FIG. 4 shows a switching power supply in which the embodiment shown in FIG. This switching power supply has a common power supply Vin and two power supply circuits. Two power supply circuit, respectively, the rectifier switches S1, commutation switch S2, and an output choke L1 and smoothing capacitor _{C OUT,} are provided with a power supply circuit connected to the output choke L1 and smoothing capacitor _{C OUT} in series. The output sides of these power supply circuits are common, and a control circuit is connected via voltage detection resistors R ₁ and R ₂ .

Voltage detection resistors R ₁ and R ₂ are provided on the output side of the power supply circuit, and a connection portion of these resistors R ₁ and R ₂ is connected to the negative input of the error amplifier 11. An error with the voltage is amplified and an error amplified signal is output. The output of the error amplifier 11 is connected to the negative input of the comparator 12.

A filter circuit 21 configured by connecting a resistor R _SAW and a capacitor C _SAW in series is connected in parallel with the series circuit of the output choke L1 and the smoothing capacitor C _OUT . The output of the filter circuit 21 is connected to the positive input of the comparator 12.

  The output of the comparator 12 is connected to the input on the reset side of the flip-flop circuit 16 so as to output the first comparison signal. Further, the clock signal is connected to the set side of the flip-flop circuit 16 so as to output the clock signal. The output of the flip-flop circuit 16 is connected to the input of the driver 17, the output of the driver 17 is connected to the control terminals of the rectifier switch S1 and the commutation switch S2, and the triangular waveform and error amplification signal obtained from the filter circuit 21 are connected. Are compared, and a comparison signal is output to control the rectifying switch S1 to be turned on with the clock signal.

Further, in this embodiment, the discharge circuit 31 is configured by connecting the auxiliary switch S3 and the discharge resistor _RD in series. The discharge circuit 31 is connected in parallel with the resistor R _SAW of the filter circuit 21, and the discharge resistor _RD is connected to the capacitor C _SAW of the filter circuit 21, and the auxiliary switch S 3 is turned on when the commutation switch S 2 is turned on. Thus, a discharge current is caused to flow through the discharge resistor _RD .

  The switching power supply configured as described above operates as follows. First, as in the case of the single case, the rectifier switch S1 is turned on and the commutation switch S2 is turned off when the clock signal is input to the set side of the flip-flop circuit 16 via the OR circuit 14. Further, the auxiliary switch S3 is also turned off at the timing when the commutation switch S2 is turned off. As a result, the output voltage from the filter circuit 21 increases. When the rectifier switch S1 is turned on, an output voltage is generated, and the error amplifier 11 connected to the output outputs an error amplification signal. This error amplified signal is compared with the triangular waveform generated by the filter circuit 21 connected in parallel with the commutation switch S2, and when the triangular waveform becomes larger than the error amplified signal, it is input to the reset side of the flip-flop circuit 16. As a result, the rectification switch S1 is turned off.

  Next, the operation when the rectifying switch S1 is turned off will be described. When the triangular waveform becomes larger than the error amplification signal, it is input to the reset side of the flip-flop circuit 16 so that the rectification switch S1 is turned off and the commutation switch S2 is turned on. The auxiliary switch S3 is also turned on at the timing when the commutation switch S2 is turned on. Thereby, the discharge current flows not only from the filter circuit 21 but also from the discharge circuit 31 connected in parallel thereto. As a result, the output voltage from the filter circuit 21 drops. Thereafter, the clock signal is input to the set side of the flip-flop circuit 16 via the OR circuit 14, whereby the rectifying switch S1 is turned on. The above operation is repeated.

  As described above, the multi-phase operation works similarly to the single case. In this embodiment, two power supply circuits are provided to achieve multi-phase. However, even if three or more power supply circuits are provided to achieve multi-phase, the same effect is obtained. Further, any of the embodiments described in the present specification can be multiphased.

5 and 6 show switching power supplies in the case where the auxiliary switch S3 provided in the embodiment shown in FIGS. 1 and 3 is configured by a diode D3. The anode of this switching power supply diode D3 is connected to a discharge resistor _RD to form a discharge circuit 31. This discharge circuit 31 is connected in parallel with the resistor R _SAW of the filter circuit 21, and the discharge resistor _RD is connected to the filter circuit 21. The capacitor C _SAW is connected.

  The switching power supply configured as described above operates as follows. Since the embodiment shown in FIG. 5 and the embodiment shown in FIG. 6 operate in substantially the same manner, the embodiment shown in FIG. 5 will be described.

First, the operation when the rectifying switch S1 is turned on will be described. As shown in the upper diagram of FIG. 2, when the clock signal is input to the set side of the flip-flop circuit 16 via the OR circuit 14, the rectification switch S1 is turned on and the commutation switch S2 is turned off. At this time, since the direction of the current flowing through the filter circuit 21 is opposite to the direction of the diode D3, no current flows through the diode D3, the capacitor C _SAW constituting the filter circuit 21 is charged, and the output from the filter circuit 21 The voltage rises.

  When the rectifier switch S1 is turned on, an output voltage is generated, and the error amplifier 11 connected to the output outputs an error amplification signal. This error amplified signal is compared with the triangular waveform generated by the filter circuit 21 connected in parallel with the commutation switch S2, and when the triangular waveform becomes larger than the error amplified signal, it is input to the reset side of the flip-flop circuit 16. As a result, the rectification switch S1 is turned off.

  Next, the operation when the rectifying switch S1 is turned off will be described. When the triangular waveform becomes larger than the error amplification signal, the rectification switch S1 is turned off by being input to the reset side of the flip-flop circuit 16. Further, since the signal output from the flip-flop circuit 16 is inverted by the driver 17 and output to the commutation switch S2, the commutation switch S2 is turned on simultaneously with the rectification switch S1 being turned off. When the commutation switch S2 is turned on, a current flows in the filter circuit 21 on the opposite side to the case where the rectification switch S1 is turned on, that is, in the forward direction of the diode D3. A discharge current flows from the discharge circuit 31 at the timing when the switch S2 is turned on. As a result, the output voltage from the filter circuit 21 drops.

  As described above, even when the auxiliary switch is configured by the diode D3, the operation is the same as when the auxiliary switch is configured by the semiconductor switch S3. Therefore, also in this embodiment, unstable operation due to on-duty can be suppressed and the input voltage range can be widened.

  According to the switching power supply of the present invention, the auxiliary switch is turned on at the turn-on timing of the commutation switch, and the discharge current is caused to flow through the discharge resistor. The range can be widened.

It is a circuit diagram of one example concerning the present invention. FIG. 2 is an operation waveform diagram of the embodiment shown in FIG. 1. FIG. 2 is a circuit diagram of another embodiment different from FIG. 1. 3 is a circuit diagram of an embodiment when the embodiment shown in FIG. 3 is multiphased. It is the circuit diagram of another Example similarly. It is the circuit diagram of another Example similarly. It is a circuit diagram of a conventional example. FIG. 8 is a circuit diagram of a conventional example different from FIG. 7. Similarly, it is a circuit diagram of another conventional example. FIG. 10 is an operation waveform diagram of the conventional example shown in FIG. 9.

Explanation of symbols

S1 rectifier switch S2 commutation switch S3, D3 auxiliary switch L1 output choke C _OUT smoothing capacitor R _SAW , R ₁ , R ₂ , R ₃ , R ₄ resistor C _SAW capacitor R _D discharge resistor 11 error amplifier 12 first comparator 13 Second comparator 14 OR circuit 15 Buffer amplifier 16 Flip-flop circuit 17 Driver 21 Filter circuit 31 Discharge circuit

Claims (3)

A rectifier switch, a commutation switch, and a filter circuit in which a resistor and a capacitor are connected are provided in parallel with the commutation switch, and an input of an error amplifier is connected to the output side of the power supply circuit to detect a reference voltage and a reference voltage. The error amplifier output signal is compared with the triangular waveform amplitude obtained from the filter circuit by the first comparator, and the first comparison signal is output. Dividing with the dividing resistor, the amplitude of the triangular waveform obtained from the filter circuit is compared with the second comparator to output the second comparison signal, and the second comparison signal and the clock signal are combined. When the load suddenly changes, the second comparison signal is output, the output signal to the rectifier switch is switched from the clock signal to the second comparison signal, and the amplitude of the triangular waveform is changed from the error amplification signal and the divided signal. In a switching power supply provided with a control means for controlling so that the rectifying switch is turned on by the clock signal in a steady state, the auxiliary switch and the discharge resistor are connected in series. Connected to form a discharge circuit, this discharge circuit is connected in parallel with the resistance of the filter circuit, and the auxiliary switch is turned on when the commutation switch is turned on, and the discharge current flows through the discharge resistor A switching power supply characterized by that. A rectifier switch, a commutation switch, and a filter circuit in which a resistor and a capacitor are connected are provided in parallel with the commutation switch, and an input of an error amplifier is connected to the output side of the power supply circuit to detect a reference voltage and a reference voltage. The error amplifier output signal is compared with the amplitude of the triangular waveform obtained from the filter circuit by a comparator, and a comparison signal is output to the rectifier switch. In a switching power supply provided with control means for controlling to be fixed by a signal, an auxiliary switch and a discharge resistor are connected in series to form a discharge circuit, and this discharge circuit is connected in parallel with the resistor of the filter circuit. The auxiliary switch is turned on when the commutation switch is turned on, and a discharge current is caused to flow through the discharge resistor. Switching power supply. 3. The switching power supply according to claim 1, wherein the auxiliary switch is constituted by a diode, and an anode of the diode is connected to the discharge resistor.

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