JP2023163359A - Switching power supply device - Google Patents

Abstract

To provide a switching power supply device with a simple structure, which can easily reduce low frequency ripple components of output voltage.SOLUTION: A switching power supply device comprises: an error amplification circuit 18 configured to generate a first control signal Ver1 obtained by inverting and amplifying voltage obtained by subtracting reference voltage Vref from an output voltage signal Vo1; a ripple component signal injection circuit 36 configured to detect a ripple component Vrip of a frequency Fr corresponding to a commercial frequency Fac included in intermediate voltage Vc, and generate a second control signal Ver2 added with the first control signal Ver1 and a voltage signal obtained by inverting and amplifying the ripple component Vrip; and a drive pulse generation circuit 20 configured to pulse-width-modulate the second control signal Ver2 to generate a drive pulse Vg of a switching element 14a. The drive pulse generation circuit 20 changes each time ratio of a high level and a low level of the drive pulse Vg toward a direction in which an ON-time ratio of the switching element 14a becomes small when the second control signal Ver2 decreases.SELECTED DRAWING: Figure 1

Description

The present invention relates to a switching power supply device that rectifies and smoothes a commercial AC voltage to generate an intermediate voltage, and converts the intermediate voltage into a predetermined output voltage using a DC-DC converter.

Conventionally, as disclosed in Patent Document 1, for example, a power conversion circuit that converts an input voltage to a predetermined output voltage is provided, and the output voltage signal, which is a voltage signal obtained by detecting the output voltage, approaches a reference voltage. There is a switching power supply device in which the on/off of a switching element of a power conversion circuit is controlled. This type of switching power supply device can be expressed as a switching power supply device 10 shown in FIG. 8, assuming that the input power source is a commercial AC power source.

The switching power supply 10 includes a rectifying and smoothing circuit 12 that rectifies and smoothes a commercial AC voltage Vi (commercial frequency Fac) and outputs an intermediate voltage Vc, and a DC-DC converter 14 that converts the intermediate voltage Vc into a predetermined output voltage Vo. , and a switching control circuit 16 that performs feedback control on and off of the switching element 14a of the DC-DC converter 14 so that the output voltage signal Vo1, which is a voltage signal obtained by detecting the output voltage Vo, approaches the reference voltage Vref.

Although the inverter system of the DC-DC converter 14 is not particularly limited, in many cases, an input/output isolated type converter is selected in order to ensure safety against a commercial AC power supply (for example, to prevent an electric shock accident).

The switching control circuit 16 includes an error amplification circuit 18 that generates a first control signal Ver1, which is a voltage signal obtained by amplifying the difference between the output voltage signal Vo1 and the reference voltage Vref, and an error amplification circuit 18 that pulse-width modulates the first control signal Ver1. and a drive pulse generation circuit 20 that generates a drive pulse Vg for the switching element 14a.

The error amplifier circuit 18 is a so-called inverting amplifier circuit, and is configured to output a first control signal Ver1, which is obtained by inverting and amplifying the voltage obtained by subtracting the reference voltage Vref from the output voltage signal Vo1, through the insulating means 18a.

The drive pulse generation circuit 20 includes a comparator 22 and a triangular wave generator 24. The triangular wave generator 24 is a block that generates a reference triangular wave Vosc of a predetermined frequency, and the frequency of the reference triangular wave Vosc becomes the switching frequency of the switching element 14a.

The comparator 22 receives the reference triangular wave Vosc at its inverting input terminal, receives the first control signal Ver1 at its non-inverting input terminal, and outputs the drive pulse Vg from its output terminal. That is, during the period when the first control signal Ver1 is higher than the reference triangular wave Vosc, the driving pulse Vg is set to high level to turn on the switching element 14a, and during the period when the first control signal Ver1 is lower than the reference triangular wave Vosc, the driving pulse Vg is set to a low level to turn off the switching element 14a.

Therefore, when the first control signal Ver1 decreases, the drive pulse generation circuit 20 changes the duty ratio between the high level and the low level of the drive pulse Vg in a direction that reduces the duty ratio when the switching element 14a is turned on. When the first control signal Ver1 rises, an operation is performed to change the duty ratio between the high level and the low level of the drive pulse Vg in the direction of increasing the duty ratio when the switching element 14a is on.

Next, the feedback control operation of the switching power supply device 10 will be briefly described. For example, if the output voltage Vo, which has been maintained at the target value, increases slightly for some reason, the error amplifier circuit 18 detects that the output voltage signal Vo1 has become higher than the reference voltage Vref, and outputs the first control signal. Ver1 is lowered, and the drive pulse generation circuit 20 changes the high-level and low-level duty ratio of the drive pulse Vg in the direction of decreasing the on-time ratio of the switching element 14a, so the output voltage Vo decreases. Return to target value. On the other hand, if the output voltage Vo, which has been maintained at the target value, drops slightly for some reason, the error amplifier circuit 18 detects that the output voltage signal Vo1 has become lower than the reference voltage Vref, and performs the first control. By increasing the signal Ver1, the drive pulse generation circuit 20 changes the high-level and low-level duty ratio of the drive pulse Vg in the direction of increasing the on-time ratio of the switching element 14a, so the output voltage Vo increases. to return to the target value.

In this switching power supply device 10, the intermediate voltage Vc does not become a complete DC voltage, but becomes a voltage in which the pulsating current component Vrip of the frequency Fr corresponding to the commercial frequency Fac is superimposed on the DC component Vdc, so the output voltage Vo There is a problem in that an unnecessary low frequency ripple component Vor is generated which has an amplitude almost in the same phase as the pulsating flow component Vrip.

First, the pulsating flow component Vrip and frequency Fr will be explained. When the commercial AC power supply is single-phase, for example, as shown in FIG. In this case, as shown in FIG. 9(c), a pulsating current with a frequency Fr=2·Fac is applied to the intermediate voltage Vc, as shown in FIG. 9(c). Component Vrip is generated. Further, as shown in FIG. 9(b), when the rectifying and smoothing circuit 12 is composed of the above rectifying section 26 and the smoothing section 30 consisting of a chopper circuit for improving the power factor, the intermediate voltage Vc A pulsating flow component Vrip with frequency Fr=2・Fac is generated.

Further, when the commercial AC voltage is three-phase, for example, as shown in FIG. In this case, as shown in FIG. 10(b), a pulsating flow component Vrip with a frequency Fr=3·Fac is generated at the intermediate voltage Vc.

The pulsating flow component Vrip, which is the main cause of the low-frequency ripple component Vor, can be reduced by increasing the value of the capacitors in the smoothing sections 28 and 30, but since the frequency Fr is low, many large-capacity capacitors are required, and the device Problems include increasing size and cost.

Furthermore, even if the ripple component Vrip occurs, the low frequency ripple component Vor can in principle be reduced by increasing the gain in the low frequency band (band including the frequency Fr) of the feedback control system of the output voltage Vo. . However, if the gain in the frequency Fr band is increased, the gain margin and phase margin of the feed pack control system in the high frequency band cannot be secured, resulting in oscillation, so in reality, the gain in the frequency Fr band must be kept low. do not have. Therefore, as shown in FIG. 11, it is possible to generate a vibration component (a component that attempts to suppress the low frequency ripple component Vor) with a frequency Fr corresponding to the pulsating flow component Vrip in the waveform of the first control signal Ver1. First, a large low-frequency ripple component Vor is generated in the output voltage Vo.

Another possible method for reducing the low frequency ripple component Vor is to modify the switching power supply 10 like a switching power supply 10x shown in FIG. 12. A feature of the switching power supply device 10x is that the triangular wave generator 24 is changed to a unique triangular wave generator 24x, and the slope of the reference triangular wave Vosc is changed approximately in proportion to the intermediate voltage Vc. With this modification, feedforward control is performed to stabilize the output voltage Vo by changing the on-time ratio of the main switching element 14a according to changes in the intermediate voltage Vc, and it is possible to reduce the low frequency ripple component Vor. . This feedforward control technique is disclosed in Patent Document 2.

JP2014-128110A Japanese Patent Application Publication No. 2010-124524

As described above, in the conventional switching power supply device 10, it is difficult to reduce the low frequency ripple component Vor of the output voltage Vo.

Since the conventional switching power supply device 10x performs feedforward control using the slope of the reference triangular wave Vosc, it is possible in principle to reduce the low frequency ripple component Vor of the output voltage Vo. However, since the slope of the reference triangular wave Vosc greatly affects the gain characteristics of the feedback control system, the gain characteristics of the feedback control system will periodically fluctuate and become unstable due to the influence of the ripple component Vrip of the intermediate voltage Vc. The problem is that it becomes. Furthermore, as explained in Patent Document 2, feedforward control using the slope of the reference triangular wave Vosc requires special measures to avoid saturation of the transformer at low input voltages. Because there are issues such as a decrease in power supply efficiency depending on the content of There are circumstances that make me want to.

The present invention has been made in view of the above-mentioned background art, and an object of the present invention is to provide a switching power supply device with a simple configuration that can easily reduce the low frequency ripple component of the output voltage.

The present invention provides a rectifying and smoothing circuit that rectifies and smoothes a commercial AC voltage to output an intermediate voltage, a DC-DC converter that converts the intermediate voltage into a predetermined output voltage, and an output that is a voltage signal obtained by detecting the output voltage. and a switching control circuit that controls on/off of a switching element of the DC-DC converter so that the voltage signal approaches a reference voltage,
The switching control circuit includes an error amplifier circuit that generates a first control signal that is a voltage signal obtained by inverting and amplifying a voltage obtained by subtracting the reference voltage from the output voltage signal, and an error amplifier circuit that generates a first control signal that is a voltage signal obtained by subtracting the reference voltage from the output voltage signal; A second control signal in which a frequency pulsating component is detected and a voltage signal obtained by inverting and amplifying the pulsating component is added to the first control signal or a voltage signal obtained by non-inverting amplification of the first control signal. a pulsating flow component signal injection circuit that generates a pulsating flow component signal injection circuit, and a drive pulse generation circuit that pulse width modulates the second control signal to generate a drive pulse for the switching element,
The drive pulse generation circuit changes the duty ratio between the high level and the low level of the drive pulse in a direction that reduces the duty ratio of the switching element to be turned on when the second control signal decreases, and The switching power supply device changes the duty ratio between the high level and the low level of the drive pulse in the direction of increasing the duty ratio when the switching element is on, when the control signal increases.

The pulsating current component signal injection circuit includes an operational amplifier into which the first control signal is input to a non-inverting input terminal and outputs the second control signal from an output terminal, an inverting input terminal of the operational amplifier, and the rectifying and smoothing circuit. an input circuit consisting of a series circuit of a capacitor and a resistor connected between the output terminal of the operational amplifier, and a feedback circuit consisting of a parallel circuit of a capacitor and a resistor connected between the output terminal and the inverting input terminal of the operational amplifier. It can be composed of

The pulsating current component signal injection circuit includes a voltage divider circuit that divides the intermediate voltage with resistance to generate a step-down voltage, and a pulse width modulation section that generates a rectangular wave voltage with a duty set based on the step-down voltage. a smoothing circuit that smooths the rectangular wave voltage to generate a smoothed voltage proportional to the step-down voltage; the first control signal is input to a non-inverting input terminal; and the second control signal is output from an output terminal. an operational amplifier, an input circuit consisting of a series circuit of a capacitor and a resistor connected between the inverting input terminal of the operational amplifier and the output end of the smoothing circuit, and a connection between the output terminal and the inverting input terminal of the operational amplifier. It can be configured with a feedback circuit consisting of a parallel circuit of a capacitor and a resistor.

The pulsating current component signal injection circuit includes a voltage dividing circuit that divides the intermediate voltage with resistance to generate a step-down voltage, an AD converter that converts the step-down voltage into a step-down voltage signal that is a digital signal, and a step-down voltage signal that converts the step-down voltage into a step-down voltage signal. a digital signal processing section that generates a proportional voltage signal that is a digital signal corresponding to the step-down voltage; a DA converter that converts the proportional voltage signal into a proportional voltage that is an analog voltage; an operational amplifier that receives one control signal and outputs the second control signal from its output terminal; and a series circuit of a capacitor and a resistor connected between the inverting input terminal of the operational amplifier and the output terminal of the DA converter. and a feedback circuit consisting of a parallel circuit of a capacitor and a resistor connected between the output terminal and the inverting input terminal of the operational amplifier.

The present invention also provides a rectifying and smoothing circuit that rectifies and smoothes a commercial AC voltage and outputs an intermediate voltage, a DC-DC converter that converts the intermediate voltage into a predetermined output voltage, and an output that is a voltage signal of the output voltage. and a switching control circuit that controls on/off of a switching element of the DC-DC converter so that the voltage signal approaches a reference voltage,
The switching control circuit includes an error amplifier circuit that generates a first control signal that is a voltage signal obtained by non-inverting amplification of a voltage obtained by subtracting the reference voltage from the output voltage signal, and a commercial frequency included in the intermediate voltage. a second control signal in which a voltage signal obtained by non-inverting amplification of the pulsating flow component is added to the first control signal or a voltage signal obtained by non-inverting amplification of the first control signal; comprising a pulsating flow component signal injection circuit that generates a control signal, and a drive pulse generation circuit that pulse width modulates the second control signal to generate a drive pulse for the switching element,
The drive pulse generation circuit changes the time ratio between the high level and the low level of the drive pulse in a direction that reduces the time ratio when the switching element is on, when the second control signal rises, and The switching power supply device changes the duty ratio between the high level and the low level of the drive pulse in the direction of increasing the duty ratio of the switching element on when the control signal of the switching element decreases.

By providing a pulsating current component signal injection circuit with a unique configuration, the switching power supply device of the present invention reduces the on-time ratio of the main switching element when the pulsating current component of the intermediate voltage oscillates in the upward direction. Feedforward control is performed to reduce the on-time ratio of the main switching element when the component oscillates in the decreasing direction, so feedback control can solve the problem of low-frequency ripple components occurring in the output voltage due to pulsating components of the intermediate voltage. This can be easily resolved without significantly affecting the system.

Furthermore, the pulsating flow component signal injection circuit injects the pulsating flow component signal into the feedback control system at a position immediately before performing pulse width control to generate the drive pulse (input end of the drive pulse generation circuit). Therefore, the operation of the main switching element can be changed extremely quickly in response to changes in the pulsating flow component, which is very effective.

FIG. 1 is a circuit diagram showing a first embodiment of a switching power supply device of the present invention. 2 is a diagram illustrating an example of the operation of the pulsating flow component signal injection circuit of FIG. 1 and a method of setting constants. FIG. 5 is a time chart showing operating waveforms of each part of the switching power supply device of the first embodiment. FIG. 3 is a circuit diagram showing a second embodiment of the switching power supply device of the present invention. 7 is a time chart showing operating waveforms of each part of the switching power supply device according to the second embodiment. FIG. 3 is a circuit diagram showing a third embodiment of the switching power supply device of the present invention. 7 is a time chart showing operating waveforms of each part of the switching power supply device according to the third embodiment. FIG. 1 is a circuit diagram showing an example of a conventional switching power supply device. They are circuit diagrams (a) and (b) showing an example of a general rectifying and smoothing circuit, and a time chart (c) showing a waveform of an intermediate voltage. They are a circuit diagram (a) showing an example of a general rectifying and smoothing circuit, and a time chart (b) showing a waveform of an intermediate voltage. 9 is a time chart showing operating waveforms of each part of the switching power supply device of FIG. 8; FIG. 2 is a circuit diagram showing another example of a conventional switching power supply device.

<First embodiment>
Hereinafter, a first embodiment of a switching power supply device of the present invention will be described based on FIGS. 1 to 3. Here, the same configuration as the conventional switching power supply device 10 is given the same reference numeral, and the description thereof will be omitted.

As shown in the circuit diagram of FIG. 1, the switching power supply device 34 of this embodiment has many points in common with the switching power supply device 10 as a whole, but the major difference is that the switching control circuit 16 includes a pulsating current component. The difference is that a signal injection circuit 36 is added.

The pulsating current signal injection circuit 36 has an operational amplifier 38, and an input circuit 40 consisting of a series circuit of a capacitor C1 and a resistor R1 is connected between the inverting input terminal of the operational amplifier 38 and the output terminal of the rectifying and smoothing circuit 12. A feedback circuit 42 consisting of a parallel circuit of a capacitor C2 and a resistor R2 is connected between the inverting input terminal and the output terminal of the operational amplifier 38. The non-inverting input terminal of the operational amplifier 38 is connected to the output terminal of the error amplifier circuit 18, and the output terminal of the operational amplifier 38 is connected to the non-inverting input terminal of the comparator 22 of the drive pulse generating circuit 20.

As shown in FIG. 2, in the pulsating current signal injection circuit 36, the first control signal Ver1 output from the error amplification circuit 18 is input to the non-inverting input terminal of the operational amplifier 38, which is one input terminal, and An intermediate voltage Vc (=DC component Vdc+pulsating current component Vrip) is input to one end on the input circuit 40 side, which is an input end, and a second control signal Ver2 is output from an output terminal of the operational amplifier 38, which is an output end. The second control signal Ver2 can be expressed as in the following equations [1] and [2].
Ver2=(1+Z2/Z1)・Ver1−(Z2/Z1)・Vc...[1]
Ver2≒(1+Z2/Z1)・Ver1−(Z2/Z1)・Vrip...[2]
Here, Z1 is a composite impedance of the capacitor C1 and resistor R1 of the input circuit 40, and Z2 is a composite impedance of the capacitor C2 and resistor R2 of the feedback circuit 42. Equation [2] is obtained by substituting Vc=Vdc+Vrip into Equation [1] and then eliminating Vdc coupled by capacitor C1 from the equation.

The values of R1, C1, R2, and C2 that determine the impedances Z1 and Z2 are adjusted individually according to the circumstances of the power supply device, but at the frequency Fr of the pulsating flow component Vrip [frequency corresponding to the commercial frequency], R1>>(ωC1) ^-1 and R2<<(ωC2) ^-1 , and it is preferable to set the setting so that almost no phase delay occurs, as shown in equation [3]. Furthermore, when adjusting so that R1>>R2 is satisfied, the setting shown in the following equation [4] is obtained.
Ver2≒(1+R2/R1)/Ver1-(R2/R1)/Vrip...[3]
Ver2≒ Ver1－(R2/R1)・Vrip...[4]
In the case of the switching power supply device 34, the pulsating current component Vrip of the intermediate voltage Vc is several tens of volts, and the first control signal Ver1 is several volts, so the size is set so that the pulsating current component Vrip can be injected into the first control signal Ver1. It is necessary to lower the blood pressure. Therefore, it is preferable that the pulsating flow signal injection circuit 36 be adjusted so as to satisfy the condition R1>>R2, and set as shown in equation [4].

In this way, the pulsating current signal injection circuit 36 detects the pulsating current component Vrip of the frequency Fr included in the intermediate voltage Vc, and converts the pulsating current into a voltage signal obtained by non-inverting amplification of the first control signal Ver1 with an amplification factor of 1. A second control signal Ver2 is generated by adding the voltage signal −(R2/R1)·Vrip obtained by inverting and amplifying the component Vrip, and outputs it to the subsequent drive pulse generation circuit 20.

Next, the operation of the switching power supply device 34 will be explained. First, the feedback control operation of the switching power supply device 34 will be briefly described assuming that the pulsating voltage Vrip is not generated at the intermediate voltage Vc. For example, if the output voltage Vo, which has been maintained at the target value, increases slightly for some reason, the error amplifier circuit 18 detects that the output voltage signal Vo1 has become higher than the reference voltage Vref, and outputs the first control signal. Ver1 is lowered, the first control signal Ver1 passes through the pulsating flow component injection circuit 36 and is input to the drive pulse generation circuit 20, and the drive pulse generation circuit 20 determines the time ratio between the high level and low level of the drive pulse Vg. is changed in the direction of decreasing the on-time ratio of the switching element 14a, so the output voltage Vo decreases and returns to the target value. On the other hand, if the output voltage Vo, which has been maintained at the target value, drops slightly for some reason, the error amplifier circuit 18 detects that the output voltage signal Vo1 has become lower than the reference voltage Vref, and performs the first control. The signal Ver1 is increased, and the first control signal Ver1 passes through the pulsating flow component injection circuit 38 and is input to the drive pulse generation circuit 20, and the drive pulse generation circuit 20 detects the high level and low level of the drive pulse Vg. Since the ratio is changed in the direction of increasing the on-time ratio of the switching element 14a, the output voltage Vo increases and returns to the target value. The above operation is basically the same as that of the conventional switching power supply device 10.

The actual operation of the switching power supply device 34, that is, the operation when a large pulsating current component Vrip (frequency Fr) is generated in the intermediate voltage Vc is expressed as shown in FIG. Since the error amplification circuit 18 has a low gain in the low frequency band including the frequency Fr, the vibration component (low frequency ripple component) of the frequency Fr corresponding to the pulsating flow component Vrip is added to the waveform of the first control signal Ver1. components that try to suppress Vor) are hardly generated.

The pulsating flow component signal injection circuit 36 receives the intermediate voltage Vc and the first control signal Ver1, and inverts and amplifies the pulsating flow component Vrip into a voltage signal -(R2/R1)·Vrip and the first control signal Ver1. The added second control signal Ver2 is generated. Therefore, the waveform of the second control signal Ver2 sometimes amplitudes in the downward direction when the pulsating flow component Vrip amplitudes in the upward direction, and it amplitudes in the downward direction when the pulsating flow component Vrip amplitudes in the upward direction. It becomes a waveform.

The drive pulse generation circuit 20 generates a signal when the second control signal Ver2 is amplitude in the downward direction (when the pulsating flow component Vrip is amplitude in the upward direction), and when the drive pulse Vg is at high level and low level. The ratio is changed in a direction that reduces the on-time ratio of the switching element 14a. Therefore, the output voltage Vo is no longer able to rise in the same phase as the pulsating flow component Vrip, and is maintained at a substantially constant value. On the other hand, when the second control signal Ver2 is amplitude in the upward direction (when the pulsating flow component Vrip is amplitude in the downward direction), the time ratio of the high level and low level of the drive pulse Vg is switched. The on-time ratio of the element 14a is changed in the direction of increasing it. Therefore, the output voltage Vo is no longer able to decrease in the same phase as the pulsating flow component Vrip, and is maintained at a substantially constant value. Therefore, low frequency ripple component Vor hardly occurs.

Note that in order to achieve Vor≒0, it is necessary to set the voltage signal corresponding to the pulsating flow component Vrip to an appropriate value - (R2/R1) and the magnitude of Vrip, but the resistors R1 and R2 can be easily optimized by adjusting the value of .

As described above, by providing the pulsating current component signal injection circuit 36 with a unique configuration, the switching power supply device 34 can detect when the main switching element 14a is turned on when the pulsating current component Vrip of the intermediate voltage Vc oscillates in the upward direction. Feedforward control is performed to lower the on-time ratio of the main switching element 14a when the pulsating current component Vrip oscillates in the decreasing direction, so the output voltage Vo is lowered by the influence of the pulsating current component Vrip of the intermediate voltage Vc. The problem of the low frequency ripple component Vor can be easily solved without significantly affecting the feedback control system.

The pulsating flow component signal injection circuit 36 also injects the pulsating flow component signal -(R2/R1)·Vrip into a position (driving Since it is injected at the input terminal of the pulse generation circuit 20), the operation of the main switching element can be changed extremely quickly in response to changes in the pulsating voltage Vrip, which is very effective.

<Second embodiment>
Next, a second embodiment of the switching power supply device of the present invention will be described based on FIGS. 4 and 5. Here, the same configuration as the switching power supply device 34 described above is given the same reference numeral and the explanation thereof will be omitted.

As shown in the circuit diagram of FIG. 4, the switching power supply device 44 of this embodiment has many points in common with the switching power supply device 34 as a whole, but the difference is that the switching control circuit 16 includes the above-mentioned pulsating current. The difference is that a new pulsating current voltage injection circuit 46 is provided in place of the component signal injection circuit 36.

The pulsating voltage injection circuit 46 includes a voltage dividing circuit 48, a pulse width modulation section 50, and a smoothing circuit 52. The pulse width modulation section 50 is a block that performs digital signal processing, and is provided in a digital processor that operates at low voltage.

The voltage dividing circuit 48 resistively divides the intermediate voltage Vc, which is a high voltage of several hundred volts, to generate a low voltage (stepped down voltage Vc1) that can be handled by the pulse width modulation section 50 in the digital processor. The pulse modulator 50 generates a rectangular wave voltage Vp (peak value V1) with a duty D set based on the step-down voltage Vc1. Then, the smoothing circuit 52 smoothes the rectangular wave voltage Vp to generate a smoothed voltage Vc2 proportional to the step-down voltage Vc1. Therefore, the smoothed voltage Vc2 can be expressed as in equation [5].
Vc2=D・V1=k2・Vc1=k2・(k1・Vc)=k1・k2(Vdc+Vrip) ・・・・・・［5］
Here, k2 is a proportional coefficient of D·V1 to Vc1, and k1 is a voltage dividing ratio of the voltage dividing circuit 40.

In addition, the pulsating current voltage injection circuit 46 includes an amplifier circuit composed of an operational amplifier 38, an input circuit 40, and a feedback circuit 42 similar to those described above. However, one end of the input circuit 40 is connected to the output end of the smoothing circuit 52 instead of the output end of the rectifying and smoothing circuit 12.

In the case of the pulsating voltage injection circuit 46, the smoothed voltage Vc2 (=k1・k2・Vc) is input to one end of the input circuit 40, so Vc in equation [1] is replaced with k1・k2・Vc, and the equation [ 2] to [4] Vrip will be replaced with k1, k2, and Vrip. However, since k1, k2, and Vrip are sufficiently low voltages here, it is preferable to adjust the values of R1 and R2 so that R1>>R2 is not satisfied, and set them according to formula [3].

In this way, the pulsating current signal injection circuit 46 detects the pulsating current component Vrip of frequency Fr included in the intermediate voltage Vc, and converts the first control signal Ver1 into a voltage signal (1+R2/R1)/Ver1 that is non-inverting amplified. A second control signal Ver2 is generated by adding the voltage signal −(R2/R1)·k1·k2·Vrip obtained by inverting and amplifying the pulsating flow component Vrip, and outputs it to the subsequent drive pulse generation circuit 20.

Next, the operation of the switching power supply device 44 will be explained. The feedback control operation of the switching power supply device 44 (operation when it is assumed that the pulsating current voltage Vrip is not generated in the intermediate voltage Vc) is the same as that of the switching power supply device 34, so a description thereof will be omitted.

The actual operation of the switching power supply device 34, that is, the operation when a large pulsating current component Vrip (frequency Fr) is generated in the intermediate voltage Vc is expressed as shown in FIG. Since the error amplification circuit 18 has a low gain in the low frequency band including the frequency Fr, the vibration component (low frequency ripple component) of the frequency Fr corresponding to the pulsating flow component Vrip is added to the waveform of the first control signal Ver1. components that try to suppress Vor) are hardly generated.

The pulsating current component signal injection circuit 46 receives the intermediate voltage Vc and the first control signal Ver1, and outputs a pulsating current voltage signal −(R2/R1)·k·Vrip obtained by inverting and amplifying the pulsating current component Vrip and the first control signal. A second control signal Ver2 is generated by adding the voltage signal (1+R2/R1) Ver1 obtained by non-inverting amplification of the signal Ver1. Therefore, the waveform of the second control signal Ver2 sometimes amplitudes in the downward direction when the pulsating flow component Vrip amplitudes in the upward direction, and it amplitudes in the downward direction when the pulsating flow component Vrip amplitudes in the upward direction. It becomes a waveform.

The drive pulse generation circuit 20 generates a signal when the second control signal Ver2 is amplitude in the downward direction (when the pulsating flow component Vrip is amplitude in the upward direction), and when the drive pulse Vg is at high level and low level. The ratio is changed in a direction that reduces the on-time ratio of the switching element 14a. Therefore, the output voltage Vo is no longer able to rise in the same phase as the pulsating flow component Vrip, and is maintained at a substantially constant value. On the other hand, when the second control signal Ver2 is amplitude in the upward direction (when the pulsating flow component Vrip is amplitude in the downward direction), the time ratio of the high level and low level of the drive pulse Vg is switched. The on-time ratio of the element 14a is changed in the direction of increasing it. Therefore, the output voltage Vo is no longer able to decrease in the same phase as the pulsating flow component Vrip, and is maintained at a substantially constant value. Therefore, low frequency ripple component Vor hardly occurs.

In order to realize Vor≒0, it is necessary to set the voltage signal -(R2/R1)・k1・k2・Vrip corresponding to the pulsating flow component Vrip to an appropriate size, but the resistance R1 , R2 and the coefficients k1, k2 can be easily optimized.

As explained above, according to the switching power supply device 44, the same effects as the switching power supply device 34 of the first embodiment can be obtained. Furthermore, since the pulsating flow component signal injection circuit 46 is provided with a pulse width modulation section 50 and a smoothing circuit 52, and these work together to generate the analog smoothed voltage Vc2, another excellent effect can be obtained.

The pulse width modulation unit 50 is a block provided in the digital processor to perform digital signal processing, but by combining it with the smoothing circuit 52, it is possible to generate the smoothed voltage Vc2 with high resolution without using an expensive high-speed digital processor. The intermediate voltage Vc can be detected with high accuracy.

Furthermore, the operation of the pulse width modulation section 50 can be freely set by rewriting the program, so for example, in normal times, the operation mode may be set to "operate to inject a pulsating flow component signal". It can be used to switch to another operating mode when a specific situation arises. Therefore, by providing this pulsating current component signal injection circuit 46, it is possible to perform feedforward control for a different purpose when a specific situation occurs, or to control a protective operation that lowers the output voltage Vo when an abnormality occurs. This makes it possible to perform advanced control with high intelligence.

<Third embodiment>
Next, a third embodiment of the switching power supply device of the present invention will be described based on FIGS. 6 and 7. Here, the same configuration as the switching power supply device 34 described above is given the same reference numeral and the explanation thereof will be omitted.

As shown in the circuit diagram of FIG. 6, the switching power supply device 54 of this embodiment replaces the error amplification circuit 18, pulsating current component signal injection circuit 36, and drive pulse generation circuit 20 of the switching power supply device 34 with a new error amplification circuit. 56, a pulsating flow component signal injection circuit 58, and a drive pulse generation circuit 60, respectively.

The error amplification circuit 56 generates a first control signal Ver1, which is a voltage signal obtained by non-inverting and amplifying a voltage obtained by subtracting the reference voltage Vref from the output voltage signal Vo1. In other words, the difference from the error amplification circuit 18 described above is that the differential voltage (Vo1-Vref) is not invertedly amplified but non-invertedly amplified.

The pulsating flow component signal injection circuit 58 detects the pulsating flow component Vrip of frequency Fr included in the intermediate voltage Vc, and outputs a voltage signal +A·Vrip obtained by non-inverting amplification of the pulsating flow component Vrip and a first control signal Ver1 (first control signal Ver1). A second control signal Ver2 is generated by adding the control signal Ver1 (which may be a voltage signal obtained by non-inverting amplification). That is, the difference from the pulsating flow component signal injection circuit 36 described above is that the pulsating flow component Vrip is not invertedly amplified but non-invertedly amplified.

The drive pulse generation circuit 60 is a circuit that generates a drive pulse Vg for the switching element 14a by pulse width modulating the second control signal Ver2, and when the second control signal Ver2 decreases, the drive pulse Vg becomes high. The duty ratio between the high level and the low level is changed in the direction of decreasing the duty ratio when the switching element 14a is on, and when the second control signal Ver2 rises, the duty ratio between the high level and the low level of the drive pulse Vg is changed to The on-time ratio of the switching element 14a is changed in the direction of increasing it. The difference from the drive pulse generating circuit 20 described above is that when the second control signal Ver2 decreases/increases, the on-time ratio of the switching element 14a is not increased/decreased but decreased/increased.

Next, the operation of the switching power supply device 54 will be explained. First, the feedback control operation of the switching power supply device 54 will be briefly described assuming that the pulsating voltage Vrip is not generated at the intermediate voltage Vc. For example, if the output voltage Vo, which has been maintained at the target value, increases slightly for some reason, the error amplifier circuit 56 detects that the output voltage signal Vo1 has become higher than the reference voltage Vref, and outputs the first control signal. Ver1 is increased, the first control signal Ver1 passes through the pulsating flow component injection circuit 58 and is input to the drive pulse generation circuit 60, and the drive pulse generation circuit 60 calculates the time ratio between the high level and the low level of the drive pulse Vg. is changed in the direction of decreasing the on-time ratio of the switching element 14a, so the output voltage Vo decreases and returns to the target value. On the other hand, if the output voltage Vo, which has been maintained at the target value, drops slightly for some reason, the error amplifier circuit 56 detects that the output voltage signal Vo1 has become lower than the reference voltage Vref, and performs the first control. The signal Ver1 is lowered, and the first control signal Ver1 passes through the pulsating flow component injection circuit 58 and is input to the drive pulse generation circuit 60, and the drive pulse generation circuit 60 detects the high level and low level of the drive pulse Vg. Since the ratio is changed in the direction of increasing the on-time ratio of the switching element 14a, the output voltage Vo increases and returns to the target value.

The actual operation of the switching power supply device 34, that is, the operation when a large pulsating current component Vrip (frequency Fr) is generated in the intermediate voltage Vc is expressed as shown in FIG. Since the error amplification circuit 56 has a low gain in the low frequency band including the frequency Fr, the waveform of the first control signal Ver1 contains a vibration component (low frequency ripple component) at the frequency Fr corresponding to the pulsating flow component Vrip. components that try to suppress Vor) are hardly generated.

The pulsating current component signal injection circuit 58 receives the intermediate voltage Vc and the first control signal Ver1, and injects the pulsating current voltage signal +A·Vrip obtained by non-inverting amplification of the pulsating current component Vrip and the first control signal Ver1 (first control signal Ver1). A second control signal Ver2 is generated by adding the control signal Ver1 (a voltage signal obtained by non-inverting amplification of the control signal Ver1). Therefore, the waveform of the second control signal Ver2 sometimes amplitudes in the upward direction when the pulsating flow component Vrip amplitudes in the upward direction, and it amplitudes in the downward direction when the pulsating flow component Vrip amplitudes in the downward direction. It becomes a waveform.

When the second control signal Ver2 is amplitude in the rising direction (when the pulsating flow component Vrip is amplitude in the rising direction), the drive pulse generation circuit 60 generates a signal when the drive pulse Vg is at high level and low level. The ratio is changed in a direction that reduces the on-time ratio of the switching element 14a. Therefore, the output voltage Vo is no longer able to rise in the same phase as the pulsating flow component Vrip, and is maintained at a substantially constant value. On the other hand, when the second control signal Ver2 is oscillating in the decreasing direction (when the pulsating flow component Vrip is oscillating in the decreasing direction), the time ratio of the high level and low level of the drive pulse Vg is switched. The on-time ratio of the element 14a is changed in the direction of increasing it. Therefore, the output voltage Vo is no longer able to decrease in the same phase as the pulsating flow component Vrip, and is maintained at a substantially constant value. Therefore, low frequency ripple component Vor hardly occurs.

Note that in order to achieve Vor≒0, it is necessary to set the voltage signal +A Vrip corresponding to the pulsating flow component Vrip to an appropriate size, but this can be easily done by adjusting the value of the amplification factor A. Can be optimized.

As explained above, the switching power supply device 54 can also provide the same effects as the switching power supply device 34 of the first embodiment. Furthermore, if the voltage divider circuit 48, pulse width modulator 50, and smoothing circuit 52 described above are used in the part that detects the intermediate voltage Vc (=Vdc+Vrip) inside the pulsating flow component signal injection circuit 58, the second embodiment can be realized. It is possible to obtain the same effects as the switching power supply device 44 of the above embodiment.

Note that the switching power supply device of the present invention is not limited to the above embodiment. For example, the switching power supply device 10 shown in FIG. 1 has a configuration in which the intermediate voltage Vc, which is a high voltage, is directly input to the input circuit 40, but a voltage divider circuit divides the intermediate voltage Vc with resistance to generate a step-down voltage. The configuration may be changed to a configuration in which a step-down voltage is input to the input circuit 40 by providing a step-down voltage. In the former case, a relatively expensive high-voltage capacitor must be used as the capacitor C1, but with the latter configuration, a relatively inexpensive low-voltage capacitor can be used.

In order to enable highly intelligent control, the switching power supply device 44 shown in FIG. The configuration is such that the output voltage Vc2 of the DA converter is input to the input circuit 40, but this part is changed to a voltage dividing circuit 48, an AD converter, a digital signal processing section, and a DA converter, and the output voltage Vc2 of the DA converter is input to the input circuit 40. You may change the configuration to input the In this case, the AD converter performs a process of converting the step-down voltage Vc1 generated by the voltage dividing circuit 48 into a step-down voltage signal that is a digital signal, and the digital signal processing section responds to the step-down voltage Vc1 based on the step-down voltage signal. The DA converter performs processing to generate a proportional voltage signal which is a digital signal, and the DA converter performs processing to convert the proportional voltage signal into a proportional voltage Vc2 which is an analog voltage.

Note that when generating the voltage Vc2 with the DA converter, it is a problem to improve the resolution of the voltage Vc2. However, by applying the dithering technology described in Patent No. 6368696 by the applicant, the resolution of the voltage Vc2 can be easily improved, and the intermediate It becomes possible to detect voltage Vc with high precision.

In addition, the above-mentioned pulsating current component signal injection circuits 36 and 46 show a configuration (specific example) suitable for use as a pulsating current component signal injection circuit of the switching power supply device according to claim 1, Any configuration other than the pulsating flow component signal injection circuits 36 and 46 may be used as long as the intended operation of the present invention can be achieved. Further, the above-described pulsating current component signal injection circuit 58 is an example of the pulsating current component signal injection circuit of the switching power supply device according to claim 5, and although a preferred specific example is not shown, it can be realized by appropriately combining known circuits. , can be freely configured.

10, 34, 44, 54 Switching power supply device 12 Rectification smoothing circuit 14 DC-DC converter 14a Switching element 16 Switching control circuit 18, 54 Error amplification circuit 20, 60 Drive pulse generation circuit 36, 46, 58 Pulsating current component signal injection circuit 38 Operational amplifier 40 Input circuit (capacitor C1, resistor R1)
42 Feedback circuit (capacitor C2, resistor R2)
48 Voltage dividing circuit 50 Pulse width modulation section 52 Smoothing circuit
D Duty of square wave voltage
Vc intermediate voltage
Vc1 Step-down voltage
Vc2 smoothed voltage
Vdc DC component of intermediate voltage
Ver1 First control signal
Ver2 Second control signal
Vg drive pulse
Vi Commercial AC voltage
Vo output voltage
Vo1 output voltage signal
Vp square wave voltage
Vref Reference voltage
Vrip Ripple component of intermediate voltage

Claims (5)

A rectifying and smoothing circuit that rectifies and smoothes a commercial AC voltage to output an intermediate voltage, a DC-DC converter that converts the intermediate voltage into a predetermined output voltage, and an output voltage signal that is a voltage signal that detects the output voltage is a reference. a switching control circuit that controls on/off of the switching element of the DC-DC converter so that the voltage approaches the voltage;
The switching control circuit includes:
an error amplifier circuit that generates a first control signal that is a voltage signal obtained by inverting and amplifying a voltage obtained by subtracting the reference voltage from the output voltage signal;
Detecting a pulsating flow component with a frequency corresponding to a commercial frequency included in the intermediate voltage, and inverting and amplifying the pulsating flow component into the first control signal or a voltage signal obtained by non-inverting amplification of the first control signal. a pulsating flow component signal injection circuit that generates a second control signal to which the voltage signal is added;
a drive pulse generation circuit that generates a drive pulse for the switching element by pulse width modulating the second control signal,
The drive pulse generation circuit changes the duty ratio between the high level and the low level of the drive pulse in a direction that reduces the duty ratio of the switching element to be turned on when the second control signal decreases, and A switching power supply device characterized in that, when a control signal of the switching device increases, a duty ratio between a high level and a low level of the drive pulse is changed in a direction that increases a duty ratio of the switching element to be turned on. The pulsating current component signal injection circuit includes an operational amplifier into which the first control signal is input to a non-inverting input terminal and outputs the second control signal from an output terminal, an inverting input terminal of the operational amplifier, and the rectifying and smoothing circuit. an input circuit consisting of a series circuit of a capacitor and a resistor connected between the output terminal of the operational amplifier, and a feedback circuit consisting of a parallel circuit of a capacitor and a resistor connected between the output terminal and the inverting input terminal of the operational amplifier. The switching power supply device according to claim 1, comprising: The pulsating current component signal injection circuit includes a voltage divider circuit that divides the intermediate voltage with resistance to generate a step-down voltage, and a pulse width modulation section that generates a rectangular wave voltage with a duty set based on the step-down voltage. a smoothing circuit that smooths the rectangular wave voltage to generate a smoothed voltage proportional to the step-down voltage; the first control signal is input to a non-inverting input terminal; and the second control signal is output from an output terminal. an operational amplifier, an input circuit consisting of a series circuit of a capacitor and a resistor connected between the inverting input terminal of the operational amplifier and the output end of the smoothing circuit, and a connection between the output terminal and the inverting input terminal of the operational amplifier. 2. The switching power supply device according to claim 1, further comprising a feedback circuit comprising a parallel circuit of a capacitor and a resistor. The pulsating current component signal injection circuit includes a voltage dividing circuit that divides the intermediate voltage with resistance to generate a step-down voltage, an AD converter that converts the step-down voltage into a step-down voltage signal that is a digital signal, and a step-down voltage signal that converts the step-down voltage into a step-down voltage signal. a digital signal processing section that generates a proportional voltage signal that is a digital signal corresponding to the step-down voltage; a DA converter that converts the proportional voltage signal into a proportional voltage that is an analog voltage; an operational amplifier that receives one control signal and outputs the second control signal from its output terminal; and a series circuit of a capacitor and a resistor connected between the inverting input terminal of the operational amplifier and the output terminal of the DA converter. 2. The switching power supply device according to claim 1, comprising: an input circuit comprising an input circuit; and a feedback circuit comprising a parallel circuit of a capacitor and a resistor connected between an output terminal and an inverting input terminal of the operational amplifier. a rectifying and smoothing circuit that rectifies and smoothes a commercial AC voltage and outputs an intermediate voltage; a DC-DC converter that converts the intermediate voltage into a predetermined output voltage; and an output voltage signal that is a voltage signal of the output voltage is converted to a reference voltage. a switching control circuit that controls on/off of a switching element of the DC-DC converter so as to approach the DC-DC converter;
The switching control circuit includes:
an error amplifier circuit that generates a first control signal that is a voltage signal obtained by non-inverting amplification of a voltage obtained by subtracting the reference voltage from the output voltage signal;
A pulsating flow component with a frequency corresponding to a commercial frequency included in the intermediate voltage is detected, and the pulsating flow component is non-invertingly amplified to the first control signal or a voltage signal obtained by non-inverting amplification of the first control signal. a pulsating flow component signal injection circuit that generates a second control signal to which the voltage signal added is added;
a drive pulse generation circuit that generates a drive pulse for the switching element by pulse width modulating the second control signal,
The drive pulse generation circuit changes the time ratio between the high level and the low level of the drive pulse in a direction that reduces the time ratio when the switching element is on, when the second control signal rises, and A switching power supply device characterized in that, when a control signal of the switching element decreases, a duty ratio between a high level and a low level of the drive pulse is changed in a direction that increases a duty ratio in which the switching element is turned on.

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