JPH0570191U - Switching power supply - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a switching power supply that can improve power factor and reduce power loss of a switching element. [Structure] The booster circuit 2 turns on / off the switching element 21.
The DC output voltage Vo is obtained by turning it off. Target setting circuit 33
Follows the increase and decrease in the entire range of the rectified output voltage signal 31,
Either the first output signal 332 or the second output signal 321 is changed so that the DC output voltage Vo becomes higher than the rectified output voltage Vr. The error detection circuit 34 compares the first output signal 332 and the second output signal 321 to form an error detection signal 34 having a waveform similar to the rectified output voltage signal 31.
1 is output. The current detection circuit 35 detects the current flowing through the inductor 22. The differential amplifier circuit 36 causes the current detection signal 351 to follow the error detection signal 341.
1 is output. The pulse width control circuit 37 uses the differential signal 361.
The control signal 371 that minimizes is output.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a boosting type switching power supply that boosts a rectified output voltage to obtain a DC output voltage. More specifically, in this type of switching power supply, the power factor is improved and the power loss of the switching element is reduced. It is related to the technology.

[0002]

[Prior Art]

 As a conventional technique for improving the power factor in a step-up switching power supply, there is JP-A-3-78469.

This type of switching power supply has a drawback in that power factor improvement cannot be achieved when the rectified output V1 of the AC power supply after rectification becomes higher than the target DC output V2. Therefore, in Japanese Patent Application Laid-Open No. 3-78469, when the rectified output V1 becomes equal to or higher than a predetermined voltage Vo, a reference voltage serving as a command value of the DC output V2 in order to maintain the DC output V2 higher than the rectified output V1. A technique for changing Vs is disclosed.

[0004]

[Problems to be solved by the device]

 However, in the conventional step-up switching power supply, the DC output V2 must be higher than the rectified output V1 in order to achieve the power factor improvement. However, when the rectified output V1 is lower than the predetermined voltage Vo, Since the output V2 is set to be considerably higher than the rectified output V1 corresponding to the constant reference voltage Vs, the current flowing through the switching element of the booster circuit becomes large, and the power loss of the switching element increases accordingly, and the power consumption increases. There is a problem that the transmission efficiency is reduced.

Therefore, an object of the present invention is to solve the above-mentioned problems, to achieve a power factor improvement, and to provide a switching power supply capable of reducing the power loss of a switching element.

[0006]

[Means for Solving the Problems]

 In order to solve the above problems, the present invention is a switching power supply including a rectifier circuit, a booster circuit, and a control circuit, wherein the rectifier circuit is a circuit that rectifies an AC power supply to obtain a rectified output voltage, The booster circuit includes a switching element, an inductor, a diode, and a capacitor, the switching element is on / off driven at a frequency higher than the frequency of the AC power supply, and the inductor is the switching element. They are connected in series, both ends of the series connection circuit are connected to the output end of the rectifier circuit, the diode and the capacitor are connected in series, and both ends of the series connection circuit are connected in parallel to the switching element. A circuit connected to obtain a DC output voltage from both ends of the capacitor, wherein the control circuit includes a target setting circuit, an error detection circuit, and a current detection circuit. A circuit, a differential amplification circuit, and a pulse width control circuit, the target setting circuit includes a reference voltage signal generator that generates a reference voltage signal, the rectified output voltage signal, and the DC output. A voltage signal is input, a first output signal and a second output signal are output, the first output signal is obtained from the reference voltage signal, and the second output signal is the DC output voltage. The DC output voltage is higher than the rectified output voltage by tracking the increase or decrease of one of the first output signal and the second output signal in the full voltage range of the rectified output voltage, obtained from the signal. The error detection circuit receives the first output signal, the second output signal and the rectified output voltage signal, and outputs the first output signal and the second output signal to the error detection circuit. Compare the output signal with Current output voltage signal is a circuit that outputs an error detection signal having a similar waveform, the current detection circuit is a circuit that detects a current flowing in the inductor, and outputs a current detection signal, the differential amplifier circuit A circuit that receives the error detection signal and the current detection signal, compares the two signals, and outputs a differential signal that causes the current detection signal to follow the error detection signal, wherein the pulse width control circuit is It is a circuit which receives the differential signal and supplies a control signal for controlling the switching element so as to minimize the differential signal to the switching element.

[0007]

[Action]

 In the booster circuit, the switching element is driven on / off at a frequency higher than the frequency of the AC power supply, the inductor is connected in series with the switching element, and both ends of the series connection circuit are connected to the output end of the rectifier circuit. A capacitor and a capacitor are connected in series, and both ends of the series connection circuit are connected in parallel to the switching element, and a DC output voltage is obtained from both ends of the capacitor. Energy becomes a flyback voltage when the switching element is off, and the flyback voltage is superimposed on the rectified output voltage, and a DC output voltage higher than the rectified output voltage is obtained.

The target setting circuit includes a reference voltage signal generation unit that generates a reference voltage signal, receives the rectified output voltage signal and the DC output voltage signal, and outputs the first output signal and the second output signal. And a first output signal is obtained from the reference voltage signal, a second output signal is obtained from the DC output voltage signal, and either one of the first output signal and the second output signal is rectified. The DC output voltage is changed so as to be higher than the rectified output voltage by following the increase and decrease in the entire output voltage range, and the error detection circuit detects the first output signal, the second output signal, and the rectified output voltage. When a signal is input and the first output signal and the second output signal are compared and an error detection signal having a waveform similar to that of the rectified output voltage signal is output, the first output signal is changed when the first output signal is changed. The output signal of 2 changes following the first output signal. And the DC output voltage also changes at the same time. Also, when the second output signal is changed, the second output signal is controlled so as to match the first output signal, and the DC output voltage changes in the process of matching. This satisfies the requirement that the DC output voltage is higher than the rectified output voltage, which is the requirement for power factor improvement.

The current detection circuit detects the current flowing through the inductor and outputs a current detection signal, and the differential amplifier circuit receives the error detection signal and the current detection signal, compares both signals, and outputs the current detection signal. Output a differential signal that causes the error detection signal to follow, and the pulse width control circuit receives the differential signal and supplies the switching element with a control signal that controls the switching element to minimize the differential signal. Since the DC output voltage is adjusted to the target output voltage and the input current changes following the AC input voltage, it becomes equivalent to a resistive load when viewed from the AC power supply, and the power factor Can be improved.

As a result, when the rectified output voltage decreases, the DC output voltage also decreases, so that the current flowing through the switching element for boosting can be reduced, and the power loss of the switching element can be reduced. be able to.

[0011]

【Example】

 FIG. 1 is a block diagram showing the configuration of a switching power supply according to the present invention. In the figure, 1 is a rectifier circuit, 2 is a booster circuit, and 3 is a control circuit.

The rectifier circuit 1 rectifies the AC power supply 10 to obtain a rectified output voltage Vr. The booster circuit 2 includes a switching element 21, an inductor 22, a diode 23, and a capacitor 24. The switching element 21 is driven on / off at a frequency f2 higher than the frequency f1 of the AC power supply 10. The frequency f2 is set in the range of several kHz to several hundred kHz, and is set to 50 kHz in this embodiment. The inductor 22 is connected in series with the switching element 21, and both ends of the series connection circuit are connected to the output terminals 11 and 12 of the rectifying circuit 1. The diode 23 and the capacitor 24 are connected in series, and both ends of the series connection circuit are connected in parallel to the switching element 21, and the DC output voltage Vo is obtained from both ends of the capacitor 24.

The control circuit 3 includes a target setting circuit 33, an error detection circuit 34, a current detection circuit 35, a differential amplifier circuit 36, and a pulse width control circuit 37.

The target setting circuit 33 includes a reference voltage signal generation unit 330 that generates a reference voltage signal 331, the rectified output voltage signal 31 and the DC output voltage signal 32 are input, and the first output signal 332. , And a second output signal 321. The first output signal 3 32 is derived from the reference voltage signal 331. The second output signal 321 is derived from the DC output voltage signal 32. Either one of the first output signal 332 and the second output signal 321 follows the increase / decrease in the entire voltage range of the rectified output voltage Vr so that the DC output voltage Vo becomes higher than the rectified output voltage Vr. Changes to. FIG. 2 is a characteristic diagram showing an example of the first output signal 332. The first output signal 332 follows the rectified output signal 31 and is set so that the DC output voltage Vo is greater than the rectified output voltage Vr. The same applies to the second output signal 321.

The error detection circuit 34 receives the first output signal 332, the second output signal 321, and the rectified output voltage signal 31, and compares the first output signal 332 with the second output signal 321. An error detection signal 341 having a waveform similar to that of the rectified output voltage signal 31 is output. Specifically, the error amplification circuit 342 compares the first output signal 332 and the second output signal 321 and outputs the error signal 343, and the multiplication circuit 344 outputs the error signal 343 and the rectified output voltage signal 31. Is multiplied to obtain an error detection signal 341. The error amplification circuit 342 and the multiplication circuit 344 can be configured by a differential amplification circuit using an operational amplifier, a multiplication circuit, or the like.

The current detection circuit 35 detects a current flowing through the inductor 22 and outputs a current detection signal 351.

The differential amplifier circuit 36 receives the error detection signal 341 and the current detection signal 351, and compares the two signals to output a differential signal 361 that causes the current detection signal 351 to follow the error detection signal 341.

The pulse width control circuit 37 receives the differential signal 361 and supplies the control signal 371 for controlling the switching element 21 so as to minimize the differential signal 361 to the switching element 21.

As described above, in the booster circuit 2, the switching element 21 is driven on / off at the frequency f2 higher than the frequency f1 of the AC power supply 10, and the inductor 22 is connected in series with the switching element 21. Both ends of the series connection circuit are connected to the output terminals 11 and 12 of the rectifier circuit 1, a diode 23 and a capacitor 24 are connected in series, and both ends of the series connection circuit are connected in parallel to the switching element 21 and a capacitor 24 Since the DC output voltage Vo is obtained from both ends of the switching element 21, the energy stored in the inductor 22 when the switching element 21 is turned on becomes the flyback voltage Vf when the switching element 21 is turned off, and the energy is stored in the rectified output voltage Vr. The back voltage Vf is superimposed to obtain a DC output voltage Vo higher than the rectified output voltage Vr.

The target setting circuit 33 includes a reference voltage signal generating section 330 for generating a reference voltage signal 331, the rectified output voltage signal 31 and the DC output voltage signal 32 are input thereto, and the first output signal 332. , The second output signal 321 is output, the first output signal 332 is obtained from the reference voltage signal 331, the second output signal 321 is obtained from the DC output voltage signal 32, and the first output signal 332. One of the second output signal 321 and the second output signal 321 follows the increase and decrease of the rectified output voltage Vr in the entire voltage range, and the DC output voltage Vo is changed so as to be higher than the rectified output voltage Vr. The first output signal 332, the second output signal 321, and the rectified output voltage signal 31 are input to 34, and the rectified output voltage signal 31 is compared by comparing the first output signal 332 and the second output signal 321. When Since the error detection signal 341 having a similar waveform is output, when the reference voltage signal 331 is changed, the second output signal 321 changes following the first output signal 332, and the DC output voltage Vo also changes at the same time. To do. Further, when the DC output voltage signal 32 is changed, the second output signal 321 is controlled to match the first output signal 332, and the DC output voltage Vo changes in the process of matching. This satisfies the requirement that the DC output voltage Vo is higher than the rectified output voltage Vr, which is the requirement for power factor improvement.

The current detection circuit 35 detects the current flowing through the inductor 22 and outputs a current detection signal 351. The differential amplifier circuit 36 compares the error detection signal 341 and the current detection signal 351 and The pulse width control circuit 37 outputs a differential signal 361 that causes the detection signal 351 to follow the error detection signal 341, and the pulse width control circuit 37 controls the switching element 21 to control the switching element 21 so as to minimize the differential signal 361. Since it is supplied, the DC output voltage Vo is adjusted to a voltage corresponding to the first output signal 332, and the input current changes following the AC input voltage. It becomes equivalent to the resistance load and can improve the power factor.

As a result, when the rectified output voltage Vr drops, the DC output voltage Vo also drops, so that the current flowing through the switching element 21 for boosting can be reduced, and the power of the switching element 21 can be reduced. Loss can be reduced.

Although the DC output voltage Vo fluctuates, since a DC-DC converter is generally connected in the subsequent stage, the DC-DC converter absorbs the fluctuation of the DC output voltage Vo and finally stabilizes. DC output can be obtained.

The target setting circuit 33 can be configured to change the DC output voltage signal 32 according to the rectified output voltage signal 31. FIG. 3 is a circuit diagram showing a specific example of the target setting circuit in that case. In the figure, the same reference numerals as those in FIG. 1 denote the same components. Hereinafter, description will be given with reference to FIGS. 1 and 3. Reference numeral 330 is a reference voltage signal generator, and 334 is a DC output voltage adjuster. The rectified output voltage Vr is applied between the terminals 335 and 336, and the DC output voltage Vo is applied between the terminals 337 and 336.

The reference voltage signal generator 330 generates a reference voltage Vk that serves as a reference for increasing / decreasing the DC output voltage Vo and outputs it as a first output signal 332. The reference voltage Vk is obtained from the battery B1. The positive electrode of the battery B1 is connected to the terminal 338. The reference voltage Vk may be obtained by forming a DC constant voltage circuit and dividing the DC constant voltage with a resistance voltage dividing circuit.

The DC output voltage adjustment unit 334 changes the voltage division ratio of the resistor that divides the DC output voltage V o according to the rectified output voltage signal 31, and outputs the divided voltage as the second output signal 321. This embodiment has a diode D1, a capacitor C1, resistors R1 to R6, an operational amplifier IC1 and a battery B2. The diode D1 and the capacitor C1 are connected in series, and both ends of which are connected in series are connected to the terminal 335 and the terminal 336. The resistors R1 and R2 are connected in series, and both ends of which are connected in series are connected to the capacitor C1. The connection point between the resistors R1 and R2 is connected to the negative input terminal of the operational amplifier IC1 and supplies a divided voltage Vin obtained by dividing the rectified output voltage Vr to the operational amplifier IC1. The battery B2 is connected to the positive input terminal of the operational amplifier IC1 and supplies the reference voltage Vk to the operational amplifier IC1. The resistor R3 is connected between the output terminal and the negative input terminal of the operational amplifier IC1. The resistor R4 has one end connected to the output end of the operational amplifier IC1 and the other end connected to the connection point between the resistors R5 and R6. The resistors R5 and R6 are connected in series, and both ends of which are connected in series are connected to the terminals 337 and 336. The connection point between the resistors R5 and R6 is connected to the terminal 339, and the divided voltage VR6 obtained by dividing the DC output voltage Vo is supplied as the second output signal 321. The operational amplifier IC1 constitutes an inverting amplifier circuit, and as shown in FIG. 4, the output voltage Vout decreases as the divided voltage Vin increases. Therefore, the terminal voltage VR5 of the resistor R5 rises due to the increase in the current flowing through the resistor R4 when the rectified output voltage Vr rises, that is, the output voltage Vout decreases. Further, the terminal voltage VR5 of the resistor R5 decreases due to the decrease in the current flowing through the resistor R4 when the rectified output voltage Vr decreases, that is, when the output voltage Vout increases. Therefore, if the DC output voltage Vo is constant, the piezoelectric voltage VR6 of the resistor R6 decreases as the terminal voltage VR5 increases, and increases as the terminal voltage VR5 decreases.

Since the error detection circuit 34 connected in the subsequent stage operates so as to match the divided voltage VR6 at the terminal 339 with the reference voltage Vk at the terminal 338, the change in the divided voltage VR6 is practical. The first output signal 332 changes, and the DC output voltage Vo is finally adjusted to the target direct current output voltage. That is, when the rectified output voltage Vr increases, the divided voltage V R6 decreases, and in the process of making the divided voltage VR6 equal to the reference voltage Vk, the DC output voltage Vo increases and the rectified output voltage Vr decreases, The divided voltage VR6 increases, and the DC output voltage Vo decreases in the process of making the divided piezoelectric voltage VR6 equal to the reference voltage Vk. As a result, the DC output voltage Vo is adjusted to be higher than the rectified output voltage Vr, and the same effect as that of the embodiment of FIG. 1 can be obtained.

The target setting circuit 33 can also be configured to change the reference voltage signal 331 by the rectified output voltage signal 31. FIG. 5 is a circuit diagram showing a specific example of the target output voltage setting circuit. In the figure, the same reference numerals as those in FIGS. 1 and 3 denote the same components. Hereinafter, description will be given with reference to FIGS. 1, 3 and 5.

The reference voltage signal generator 330 changes the reference voltage Vk according to the rectified output voltage signal 31 and outputs the first output signal 332. In this embodiment, it has a diode D1, a capacitor C1, a resistor R1 and a resistor R2, a resistor R7, a battery B3, a resistor R5 and a resistor R6. The diode D1, the resistor R1 and the resistor R2 are connected in series, and both ends of the series connection circuit are connected to the terminals 335 and 336. The capacitor C1 is connected in parallel to the series connection circuit of the resistor R1 and the resistor R2. The resistor R2 generates a divided voltage Vin obtained by dividing the rectified output voltage Vr. The resistor R7 and the battery B3 are connected in series, and both ends of the series connection are connected to the resistor R2. One end of the resistor R7 is connected to the terminal 338, and the terminal 338 is supplied with the reference voltage Vk. The reference voltage Vk becomes a voltage as shown in FIG. 6 due to the relationship between the divided voltage Vin and the voltage Vref of the battery B3. That is, when the divided voltage Vin is higher than the voltage Vref, current flows from the resistor R1 to the battery B3 and becomes higher than the voltage Vref. When the divided voltage Vin is lower than the voltage Vref, the resistance is changed from the battery B3. A current flows into R 2 and becomes lower than the voltage Vref.

The DC output voltage adjustment unit 334 has resistors R5 and R6, and divides the DC output voltage V o by resistance. The connection point of the resistors R5 and R6 is connected to the terminal 339, and the divided voltage VR6 is output to the terminal 339 as the second output signal 321.

Since the error detection circuit 34 connected in the subsequent stage operates so that the first output signal 332 and the second output signal 321 coincide with each other, the second output signal 321 outputs the first output signal 321. It changes following the signal 332, and finally the DC output voltage Vo is adjusted to the target DC output voltage. As a result, it is possible to obtain the same effect as that of the embodiment shown in FIG.

Even if the target output voltage setting circuit 33 is configured to change the first output signal 322 or the second output signal 321 stepwise as shown by the dotted line in FIG. It is possible to obtain the same effect as that of the embodiment.

[0033]

[Effect of the device]

 As described above, according to the present invention, the following effects can be obtained. (A) In the step-up circuit, the switching element is driven on / off at a frequency higher than the frequency of the AC power supply, the inductor is connected in series with the switching element, and both ends of the series connection circuit are connected to the output end of the rectifier circuit. The diode and capacitor are connected in series, and both ends of the series connection circuit are connected in parallel with the switching element, and the DC output voltage is obtained from both ends of the capacitor. Can be provided. (B) The target output voltage setting circuit includes a reference voltage signal generation unit that generates a reference voltage signal, and the rectified output voltage signal and the DC output voltage signal are input to the first output signal and the second output. And a first output signal is obtained from the reference voltage signal, a second output signal is obtained from the DC output voltage signal, and one of the first output signal and the second output signal is output. , The rectified output voltage is changed so that the DC output voltage becomes higher than the rectified output voltage in accordance with the increase / decrease in the entire voltage range, and the error detection circuit detects the first output signal, the second output signal and the rectified output signal. The output voltage signal is input, the first output signal and the second output signal are compared, and an error detection signal having a waveform similar to the rectified output voltage signal is output, and the current detection circuit detects the current flowing in the inductor. Detects and outputs current detection signal for differential amplification The error detection signal and the current detection signal are input to the path, the two signals are compared and a differential signal that causes the current detection signal to follow the error detection signal is output, and the pulse width control circuit receives the differential signal. The control signal for controlling the switching element is provided to the switching element so as to minimize the differential signal, so that it is possible to achieve the power factor improvement and reduce the power loss of the switching element. Power supply can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a switching power supply according to the present invention.

FIG. 2 is a characteristic diagram showing an example of a first output signal.

FIG. 3 is a circuit diagram showing a specific example of a target setting circuit configured to change a DC output voltage signal.

FIG. 4 is a characteristic diagram of an inverting amplifier circuit.

FIG. 5 is a circuit diagram showing a specific example of a target setting circuit configured to change a reference voltage signal.

FIG. 6 is an input / output characteristic diagram of a reference voltage generator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rectifier circuit 11, 12 output terminal 2 booster circuit 21 switching element 22 inductor 23 diode 24 capacitor 3 control circuit 31 rectified output voltage signal 32 DC output voltage signal 33 target setting circuit 331 reference voltage signal 332 first output signal 321 second Output signal 34 Error detection circuit 341 Error detection signal 35 Current detection circuit 351 Current detection signal 36 Differential amplification circuit 361 Differential signal 37 Pulse width control circuit 371 Control signal Vr Rectified output voltage Vo DC output voltage

Claims (4)

[Scope of utility model registration request] 1. A switching power supply having a rectifier circuit, a booster circuit, and a control circuit, wherein the rectifier circuit is a circuit that rectifies an AC power supply to obtain a rectified output voltage, and the booster circuit is a switching circuit. Element, inductor,
A diode and a capacitor, wherein the switching element is turned on / off at a frequency higher than the frequency of the AC power supply.
It is driven off, the inductor is connected in series with the switching element, both ends of the series connection circuit are connected to the output end of the rectifier circuit, the diode and the capacitor are connected in series, and the series connection circuit Is a circuit in which both ends of are connected in parallel to the switching element and obtains a DC output voltage from both ends of the capacitor, and the control circuit includes a target setting circuit, an error detection circuit, a current detection circuit, and a differential amplifier circuit. A pulse width control circuit, the target setting circuit includes a reference voltage signal generation unit for generating a reference voltage signal, the rectified output voltage signal and the DC output voltage signal are input, Output signal of the second
And the first output signal is obtained from the reference voltage signal, the second output signal is obtained from the DC output voltage signal, and the first output signal and the second output signal One of the output signals is a circuit that changes the DC output voltage so as to be higher than the rectified output voltage by following the increase and decrease in the entire voltage range of the rectified output voltage, and the error detection circuit, The first output signal, the second output signal, and the rectified output voltage signal are input, and the first output signal and the second output signal are compared to obtain a waveform similar to the rectified output voltage signal. Is a circuit that outputs an error detection signal, the current detection circuit is a circuit that outputs a current detection signal by detecting a current flowing in the inductor, the differential amplifier circuit, the error detection signal and the current Detection signal A pulse width control circuit that receives the differential signal, compares the two signals, and outputs a differential signal that causes the current detection signal to follow the error detection signal. A switching power supply that is a circuit that supplies a control signal for controlling the switching element so as to minimize the signal to the switching element. 2. The switching power supply according to claim 1, wherein the target setting circuit is a circuit that changes the second output signal. 3. The switching power supply according to claim 1, wherein the target setting circuit is a circuit that changes the first output signal. 4. The switching power supply according to claim 1, 2 or 3, wherein the target setting circuit is a circuit that changes the first output signal or the second output signal in a stepwise manner.