TWI410034B - Flyback power supply system - Google Patents

Abstract

A flyback power supply system includes a rectifying and filtering circuit, a pulse width modulation (PWM) controller, a master converter circuit, a slave converter circuit, and a slave control circuit. The master converter circuit converts signals output from the rectifying and filtering circuit into first direct current (DC) power signals. The slave converter circuit converts the signals output from the rectifying and filtering circuit into second DC power signals when a load is heavy, and superposes the second DC power signals on the first DC power signals to commonly drive the load. The slave control circuit detects if the load is heavy, controls PWM signals to input to the slave converter circuit to make the slave converter circuit to convert if the load is heavy, and controls the PWM signals not to input to the slave converter circuit if the load is light. When the load is light, the slave converter circuit does not work, which reduces power loss.

Description

Flyback power supply system

The present invention relates to a power supply system, and more particularly to a flyback power supply system.

In a flyback power supply system, a transformer, a set of output rectifier circuits, and a feedback circuit are generally used to control the output voltage/current. Because of its combination of storage and isolation, this transformer is usually high in height, resulting in a large volume, which makes it difficult to meet the demand for thin and light electronic products. In addition, because the effective conduction period of the transformer is small, the power loss is large when there is no load or light load.

In view of this, it is necessary to provide a flyback power supply system that consumes less power when there is no load or light load.

A flyback power supply system includes a rectification and filtering circuit, a pulse width modulation controller, a feedback circuit, a main conversion circuit, a slave conversion circuit, and a slave conversion control circuit. The main conversion circuit is configured to convert the signal output by the rectifying and filtering circuit into a first DC power signal according to the control of the pulse width modulation controller to drive the load. The conversion circuit is configured to convert the signal output by the rectifying and filtering circuit into a second DC power signal and superimpose the signal to the first DC power signal according to the control of the pulse width modulation controller when the load is a heavy load. To drive the load together. The switching control circuit is connected between the pulse width modulation controller and the slave conversion circuit, and includes a first switch, the first switch includes a control electrode, a first electrode and a second electrode, wherein the first electrode is connected to the pulse width a modulation controller, the second electrode is connected to the slave conversion circuit, the slave conversion control circuit is configured to detect whether the load is a heavy load, and if the load is a heavy load, controlling the first switch to be turned on to control the pulse The pulse width modulation signal of the width modulation controller enters the slave conversion circuit, so that the slave conversion circuit converts the signal output by the rectifier filter circuit into the second DC power signal, and if the load is light or unloaded, Then, the first switch is turned off to control the pulse width modulation signal of the pulse width modulation controller not to enter the slave conversion circuit, so that the slave conversion circuit does not perform conversion.

Preferably, the main conversion circuit includes a first transformer and a second switch. The first transformer includes a primary winding and a secondary winding. The second switch is controlled by the pulse width modulation controller. The primary winding of the first transformer, the second switch and the first resistor are sequentially connected in series between the output end of the rectifying and filtering circuit and the ground.

Preferably, the main conversion circuit further includes a first diode and a first capacitor. The anode of the first diode is connected to the high voltage end of the secondary winding of the first transformer, and the cathode outputs the first DC power signal for rectification. One end of the first capacitor is connected to the cathode of the first diode, and the other end is grounded for filtering.

Preferably, the slave switching circuit includes a second transformer and a third switch. The second transformer includes a primary winding and a secondary winding. a third switch is connected to the slave switching control circuit, configured to receive and control the pulse width modulation signal when the slave pulse width modulation signal of the pulse width modulation controller is controlled by the slave switching control circuit . The primary winding of the second transformer, the third switch and the second resistor are sequentially connected in series between the output end of the rectifying and filtering circuit and the ground.

Preferably, the slave conversion circuit further includes a second diode and a second capacitor. The anode of the second diode is connected to the high voltage end of the secondary winding of the second transformer, and the cathode outputs the second DC power signal for rectification. One end of the second capacitor is connected to the cathode of the second diode, and the other end is grounded for filtering.

Preferably, the slave switching control circuit detects the voltages of the first resistor and the second resistor, and according to whether the detected voltages of the first resistor and the second resistor exceed the maximum allowable load, the first resistor and the second resistor A predetermined ratio of voltages to determine if the load is a heavy load.

Preferably, the slave switching control circuit detects the voltage of the feedback signal of the feedback circuit, and determines the load according to whether the detected feedback signal voltage exceeds a predetermined ratio of the voltage of the feedback signal at the maximum allowable load. Whether it is overloaded.

Preferably, the slave switching control circuit further includes a first comparator and a second comparator. The first comparator includes a positive input terminal, a negative input terminal and an output terminal. The negative input terminal receives the detection voltage via a third resistor and is grounded via a third capacitor, and the positive input terminal receives the first reference voltage via the fourth resistor and Connecting the output end of the first comparator via a third diode and a fifth resistor, the anode of the third diode is connected to the positive input end, and the cathode of the third diode is connected to the fifth resistor, the first The output of a comparator is coupled to the gate of the first switch. The second comparator includes a positive input terminal, a negative input terminal and an output terminal. The negative input terminal of the second comparator receives the second reference voltage, and the positive input terminal of the second comparator receives the detected voltage via the sixth resistor and The fourth comparator is grounded, and the output of the second comparator is coupled to the negative input of the first comparator.

Preferably, the slave switching control circuit further includes a fourth diode, a fifth diode, and a sixth diode. The anode of the fourth diode receives the detection voltage, and the cathode of the fourth diode is connected to the third resistor for preventing signal backflow. The anode of the fifth diode receives the detection voltage, and the cathode of the fourth diode is connected to the sixth resistor for preventing signal backflow. The anode of the sixth diode is connected to the output of the second comparator, and the cathode of the sixth diode is connected to the negative input of the first comparator for preventing signal backflow.

Preferably, the negative input terminal of the first comparator is connected to the first resistor via the third resistor to receive the detection voltage, and the positive input terminal of the second comparator is connected to the second resistor via the sixth resistor. To receive the detection voltage.

Preferably, the pulse width modulation controller is configured to determine a condition of the load according to a voltage of the first resistor, and adjust a duty ratio of the pulse width modulation signal according to a feedback signal of the feedback circuit and the load condition. .

Preferably, the pulse width modulation controller is further configured to determine a condition of the load according to a voltage of the second resistor.

Preferably, the pulse width modulation controller is configured to determine a condition of the load according to a voltage of the feedback signal of the feedback circuit, and adjust a duty ratio of the pulse width modulation signal according to a condition of the load.

Preferably, when the pulse width modulation controller determines that the load is a heavy load, the duty ratio of the pulse width modulation signal is increased, and when the load is determined to be light or no load, the pulse width is reduced. The duty cycle of the modulation signal.

Preferably, the pulse width modulation controller determines whether the load is a heavy load according to whether the detected voltage exceeds a predetermined ratio of the maximum allowable load voltage.

The above-mentioned flyback power supply system is controlled by the slave switching control circuit so that the slave converter circuit operates only when the load is heavy, to drive the load together with the main converter circuit, and provides sufficient driving power, while being lightly loaded or unloaded. When the slave switching circuit does not operate, only the main converter circuit drives the load, so that the power loss of the flyback power supply system is minimized and the efficiency is improved.

1 is a schematic diagram of a flyback power supply system 10 in accordance with an embodiment of the present invention. In the present embodiment, the flyback power supply system 10 is configured to convert the AC power signal Vin into a DC power signal Vo to drive the load. Among them, the AC power signal Vin is 220V AC mains. The flyback power supply system 10 includes a rectification filter circuit 100, a pulse width modulation controller 110, a feedback circuit 120, a main conversion circuit 130, a slave conversion circuit 140, and a slave conversion control circuit 150. The rectifying and filtering circuit 100 is configured to rectify and filter the AC power signal Vin into a DC power signal, which includes a full bridge rectifier circuit and a filter capacitor. In this embodiment, the DC power signal has an amplitude of 200 to 330 V, for example, 311 V. The feedback circuit 120 is configured to generate a feedback signal according to the DC power signal Vo outputted by the flyback power supply system 10, and send it back to the pulse width modulation controller 110. The pulse width modulation controller 110 is configured to generate a corresponding pulse width modulation signal according to the feedback signal and the load condition to control the main conversion circuit 130 and the slave conversion circuit 140. In the present embodiment, the load condition includes the load being a heavy load, the load being a light load, and the load being a no load. In the present embodiment, when the actual load exceeds a predetermined ratio of the maximum allowable load, the load condition is determined to be a heavy load, wherein the predetermined ratio may be set and adjusted according to actual conditions, for example, may be 30% or 40%.

The main conversion circuit 130 is configured to convert the DC power signal outputted by the rectification and filtering circuit 100 into a first DC power signal according to the control of the pulse width modulation controller 110 to drive the load.

The conversion circuit 140 is configured to convert the DC power signal outputted by the rectification and filtering circuit 100 into a second DC power signal according to the control of the pulse width modulation controller 110 when the load is a heavy load, and superimpose it on the first DC Power signals to drive the load together.

The slave switching control circuit 150 is connected between the pulse width modulation controller 110 and the slave switching circuit 140 for detecting whether the load is a heavy load. The slave switching control circuit 150 includes a first switch Q1 including a control electrode, a first electrode, and a second electrode. The first electrode of the first switch Q1 is connected to the pulse width modulation controller 110, and the second electrode is connected to the slave conversion circuit 140. If the load is a heavy load, the first switch Q1 is controlled to be turned on by the switching control circuit 150 to control the pulse width modulation signal of the pulse width modulation controller 110 to enter the slave conversion circuit 140, so that the slave rectifier circuit 140 outputs the rectifier filter circuit 100. The DC power signal is converted into a second DC power signal. If the load is light load or no load, the first switch Q1 is controlled to be turned off by the switching control circuit 150 to control the pulse width modulation signal of the pulse width modulation controller 110 not to enter the slave conversion circuit 140, so that the slave conversion circuit 140 does not Make the conversion.

As such, via the control from the switching control circuit 150, the slave switching circuit 140 operates only when the load is heavily loaded to drive the load together with the main converter circuit 130 to provide sufficient driving power. At the light load or no load, the slave switching circuit 140 does not operate, and only the main converter circuit 130 drives the load. Therefore, the power loss of the flyback power supply system 10 is minimized, and the efficiency is improved.

2 is a detailed circuit diagram of a flyback power supply system 10 according to an embodiment of the present invention. In the present embodiment, the main conversion circuit 130 includes a first transformer T1, a second switch Q2, and a first resistor R1. The first transformer T1 includes a primary winding and a secondary winding, wherein the high voltage end of the primary winding is connected to the rectifying filter circuit 100. The second switch Q2 includes a control electrode, a first electrode and a second electrode, wherein the control electrode of the second switch Q2 is connected to the pulse width modulation controller 110, the first electrode is connected to the low voltage end of the primary winding of the first transformer T1, and the second The electrode is grounded via the first resistor R1, that is, the primary winding of the first transformer T1, the second switch Q2, and the first resistor R1 are sequentially connected in series between the output end of the rectifying and filtering circuit 100 and the ground. The second switch Q2 is controlled by the pulse width modulation controller 110, that is, the pulse width modulation signal is turned on or off, so that the first transformer T1 converts the DC power signal outputted by the rectifier filter circuit 100 into the first square wave signal.

In the embodiment, the main conversion circuit 130 further includes a first diode D1 and a first capacitor C1. The first diode D1 is used for rectification, the anode thereof is connected to the high voltage end of the secondary winding of the first transformer T1, and the cathode outputs the first DC power signal. The first capacitor C1 is used for filtering, one end of which is connected to the cathode of the first diode D1, and the other end is grounded.

The slave conversion circuit 140 includes a second transformer T2, a third switch Q3, and a second resistor R2. The second transformer T2 includes a primary winding and a secondary winding, wherein the high voltage end of the primary winding of the second transformer T2 is connected to the rectifying filter circuit 100. The third switch Q3 is connected to the slave switching control circuit 150 for receiving the pulse width modulation signal when the pulse width modulation signal of the pulse width modulation controller 110 is controlled from the conversion control circuit 150 to enter the slave conversion circuit 140, and according to the reception The pulse width modulation signal is turned on or off, so that the second transformer T2 converts the DC power signal outputted by the rectifier filter circuit 100 into a second square wave signal. The third switch Q3 also includes a control electrode, a first electrode and a second electrode, wherein the control electrode of the third switch Q3 is connected to the second electrode of the first switch Q1 of the switching control circuit 150, and the first electrode is connected to the second transformer T2. At the low voltage end of the primary winding, the second electrode is grounded via a second resistor R2. That is, the primary winding of the second transformer T2, the third switch Q3 and the second resistor R2 are sequentially connected in series between the output end of the rectifying and filtering circuit 100 and the ground.

In the present embodiment, the slave conversion circuit 140 further includes a second diode D2 and a second capacitor C2. The second diode D2 is used for rectification, the anode is connected to the high voltage end of the secondary winding of the second transformer T2, and the cathode outputs the second DC power signal. The second capacitor C2 is used for filtering, one end of which is connected to the cathode of the second diode D2, and the other end is grounded.

In the present embodiment, the first switch Q1 is a PNP-type transistor, and its control is extremely base, the first electrode is an emitter, and the second electrode is a collector. The second switch Q2 and the third switch Q3 are both metal oxide semiconductor field effect transistors, and the control electrodes of the second switch Q2 and the third switch Q3 are both gates, the first electrodes are all drain electrodes, and the second electrodes are all Source.

In the present embodiment, the second electrode of the second switch Q2 and the second electrode of the third switch Q3 are connected from the switching control circuit 150 for detecting the voltages of the first resistor R1 and the second resistor R2 to detect whether the load is For heavy loads. In the present embodiment, when the actual load exceeds a predetermined ratio of the maximum allowable load, the load condition is determined to be a heavy load, wherein the predetermined ratio may be set and adjusted according to actual conditions, for example, may be 30% or 40%. Therefore, the voltage of the first resistor R1 and the second resistor R2 is detected from the conversion control circuit 150, and it is determined whether the actual voltage of the first resistor R1 and the second resistor R2 exceeds a predetermined ratio of the maximum allowable load voltage to determine whether the load is Overloaded. If the actual voltage exceeds a predetermined ratio of the maximum allowable load voltage, and the load is determined to be a heavy load, the first switch Q1 is controlled to be turned on by the switching control circuit 150, so that the pulse width modulation signal of the pulse width modulation controller 110 enters the third. The control pole of switch Q3. If the actual voltage does not exceed the predetermined ratio of the maximum allowable load voltage, and the load is judged to be light load or no load, the first switch Q1 is controlled to be turned off from the switching control circuit 150 to adjust the pulse width of the pulse width modulation controller 110. The variable signal does not enter the control pole of the third switch Q3.

In another embodiment of the present invention, the feedback control circuit 150 is connected to the feedback circuit 120 to detect the voltage of the feedback signal of the feedback circuit 120, and the feedback is based on whether the voltage of the actual feedback signal exceeds the maximum allowable load. A predetermined ratio of the voltage of the signal to determine if the load is a heavy load.

In the present embodiment, the slave switching control circuit 150 includes a first comparator 1501 and a second comparator 1502. The first comparator 1501 and the second comparator 1502 each include a positive input terminal, a negative input terminal, and an output terminal. The negative input terminal of the first comparator 1501 receives the detection voltage via the third resistor R3, that is, connects the first resistor R1 or the connection feedback circuit 120, and is grounded via the third capacitor C3. The positive input of the first comparator 1501 receives the first reference voltage Vcc1 via the fourth resistor R4, and connects the output of the first comparator 1501 via the third diode D3 and the fifth resistor R5. The anode of the third diode D3 is connected to the positive input terminal of the first comparator 1501, and the cathode is connected to the fifth resistor R5. The output of the first comparator 1501 is connected to the gate of the first switch Q1.

The negative input terminal of the second comparator 1502 receives the second reference voltage, and the positive input terminal receives the detected voltage via the sixth resistor R6, that is, connects the second resistor R2 and the feedback circuit 120, and is grounded via the fourth capacitor C4. The output of the second comparator 1502 is coupled to the negative input of the first comparator 1501.

In this embodiment, since the voltages on the first resistor R1 and the second resistor R2 are pulse signals, the third resistor R3 and the third capacitor C3 are used to convert the voltage in the form of a pulse on the first resistor R1 into a stable average voltage. In comparison with the first reference voltage Vcc1, the sixth resistor R6 and the fourth capacitor C4 are used to convert the voltage in the form of a pulse on the second resistor R2 into a stable average voltage to be compared with the second reference voltage Vcc2.

In this embodiment, the pulse width modulation controller 110 detects the voltage of the first resistor R1, determines whether the actual voltage of the first resistor R1 exceeds a predetermined ratio of the maximum allowable load, and determines the load condition, and according to the load condition. And the feedback signal of the feedback circuit 120 adjusts the duty ratio of the pulse width modulation signal accordingly. If the pulse width modulation controller 110 determines that the load is a heavy load, the duty ratio of the pulse width modulation signal is increased, thereby extending the conduction time of the second switch Q2 and the third switch Q3, so that the main conversion circuit 130 and the slave conversion Circuit 140 provides sufficient DC power signal Vo to the load. If it is determined that the load is light load or no load, the pulse width modulation controller 110 adjusts the duty ratio of the pulse width modulation signal, thereby shortening the conduction time of the second switch Q2, so that the main conversion circuit 130 provides an appropriate amount of DC power. Signal Vo to load.

In another embodiment of the present invention, the pulse width modulation controller 110 detects the voltage of the feedback signal of the feedback circuit 120, and according to whether the voltage of the actual feedback signal exceeds the voltage of the feedback signal when the maximum allowable load is exceeded. Predetermine the ratio to determine if the load is overloaded.

In the present embodiment, assuming that the average voltage on the first resistor R1 is 5 V at the maximum allowable load, and determining that the predetermined ratio from light load to heavy load is 40%, setting the first reference voltage Vcc1 to 2 V is The predetermined ratio of the load to the light load is slightly smaller, about 35%, and the second reference voltage is set to 0.8V.

When the load is light load, the slave switching circuit 140 does not operate, and thus the voltage on the second resistor R2 is 0, that is, the voltage at the positive input terminal of the second comparator 1502 is 0, which is smaller than the voltage at the negative input terminal of the second comparator 1502. The second comparator 1502 outputs a low level signal. Because it is light load at this time, the average voltage of the voltage on the first resistor R1 after being converted by the third resistor R3 and the third capacitor C4 is smaller than the product of the average voltage at the heavy load and the predetermined ratio, that is, less than 2V, the first comparator 1501 The negative input terminal voltage is less than the positive input terminal voltage, and the first comparator 1501 outputs a high level signal. Therefore, the first switch Q1 is turned off. At this time, the pulse width modulation signal cannot enter the control electrode of the third switch Q3, and the slave switching circuit 140 does not operate.

When the load is changed from light load to heavy load, the second comparator 1502 still outputs a low level signal because the slave switching circuit 140 is not operating. The duty ratio of the pulse width modulation signal becomes larger, so that the voltage of the first resistor R1 becomes larger, and the average voltage of the voltage of the first resistor R1 after being converted by the third resistor R3 and the third capacitor C3 is greater than that of the heavy load. The product of the average voltage and the predetermined ratio, that is, greater than 2V, the voltage of the negative input terminal of the first comparator 1501 is greater than the voltage of the positive input terminal, and the first comparator 1501 outputs a low level signal. The first switch Q1 is turned on. At this time, the pulse width modulation signal enters the gate of the third switch Q3 and starts to operate from the conversion circuit 140. At this time, the third diode D3 is turned on for clamping, and the 2V voltage of the first reference voltage Vcc1 is equally divided on the fourth resistor R4 and the fifth resistor R5, thereby pulling down the output end of the first comparator 1501. That is, the voltage level of the gate of the first switch Q1 keeps the first switch Q1 in an on state, ensuring continuous operation from the converter circuit 140.

When the load is a heavy load, the positive input terminal voltage of the second comparator 1502 is greater than the negative input terminal voltage, and a high level signal is output. The voltage of the negative input terminal of the first comparator 1501 is greater than the voltage of the positive input terminal, and the low level signal is output, and the first switch Q1 remains turned on, and continues to operate from the conversion circuit 140.

When the load is changed from a heavy load to a light load, the duty ratio of the pulse width modulation signal becomes small, and the voltages of the first resistor R1 and the second resistor R2 become smaller. The average voltage after the voltage of the second resistor R2 is converted by the sixth resistor R6 and the fourth capacitor C4 is smaller than the voltage of the negative input terminal of the second comparator 1502 and the voltage of the first resistor R1 is converted by the third resistor R3 and the third capacitor C3. When the average voltage is less than the positive input voltage of the first comparator 1501, the second comparator 1502 outputs a low level signal, and the first comparator 1501 outputs a high level signal. Thus, the first switch Q1 is turned off, and the operation is stopped from the conversion circuit 140.

FIG. 3 is a specific circuit diagram of a flyback power supply system 20 according to another embodiment of the present invention. In the present embodiment, the flyback power supply system 20 differs from the flyback power supply system 10 of FIG. 2 in that the slave switching control circuit 150A of the flyback power supply system 20 further includes a fourth diode D4, The fifth diode D5 and the sixth diode D6, the rest are identical, and therefore will not be described here. The anode of the fourth diode D4 receives the detection voltage, for example, the first resistor R1 is connected, and the cathode is connected to the third resistor R3. The anode of the fifth diode D5 receives the detection voltage, for example, the second resistor R2 is connected, and the cathode is connected to the sixth resistor R6. The sixth diode D6 is connected to the output of the second comparator 1502, and the cathode is connected to the negative input of the first comparator. The fourth diode D4, the fifth diode D5, and the sixth diode D6 are both used to prevent signal reflow.

FIG. 4 is a specific circuit diagram of a flyback power supply system 30 according to another embodiment of the present invention. In the present embodiment, the flyback power supply system 30 differs from the flyback power supply systems 10, 20 of FIGS. 2 and 3 in that the pulse width modulation controller 110 of the flyback power supply system 30 is also connected to the third. The second electrode of the switch Q3 has the same parts and is not described here. The pulse width modulation controller 110 is further configured to determine the condition of the load according to the voltage of the second resistor R2.

The flyback power supply system 10, 20, 30 of the present invention, via control from the switching control circuits 150, 150A, causes the slave switching circuit 140 to operate only when the load is heavily loaded to drive the load together with the main conversion circuit 130, providing Sufficient drive power, while at light load or no load, the slave conversion circuit 140 does not operate, only the main converter circuit 130 drives the load, and thus the power loss of the flyback power supply system 10, 20, 30 is minimized, effectiveness.

In addition, the flyback power supply system 10, 20, 30 uses two transformers T1, T2, which replaces a conventional one, thereby greatly reducing the height of the flyback power supply system 10, 20, 30, making the electronic product thin and light. Chemical.

In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art of the present invention should be included in the following claims.

10, 20, 30‧‧‧Return-type power supply system

100‧‧‧Rectifier filter circuit

110‧‧‧ pulse width modulation controller

120‧‧‧Return circuit

130‧‧‧Main conversion circuit

140‧‧‧From conversion circuit

T1, T2‧‧‧ first and second transformers

Q2, Q3‧‧‧ second and third switches

R1, R2‧‧‧ first and second resistors

D1, D2‧‧‧ first and second diodes

C1, C2‧‧‧ first and second capacitors

150, 150A‧‧‧ slave conversion control circuit

Q1‧‧‧First switch

1501‧‧‧First comparator

1502‧‧‧Second comparator

R3, R4, R5, R6‧‧‧ third to sixth resistors

C3, C4‧‧‧ third and fourth capacitors

D3, D4, D5, D6‧‧‧ third to sixth diodes

Vcc1, Vcc2‧‧‧ first and second reference voltages

Vin‧‧‧AC power signal

Vo‧‧‧DC power signal

1 is a schematic diagram of a flyback power supply system according to an embodiment of the present invention;

2 is a specific circuit diagram of a flyback power supply system according to an embodiment of the present invention;

3 is a specific circuit diagram of a flyback power supply system according to another embodiment of the present invention; and

4 is a specific circuit diagram of a flyback power supply system according to still another embodiment of the present invention.

10‧‧‧Return-type power supply system

100‧‧‧Rectifier filter circuit

110‧‧‧ pulse width modulation controller

120‧‧‧Return circuit

130‧‧‧Main conversion circuit

140‧‧‧From conversion circuit

T1, T2‧‧‧ first and second transformers

Q2, Q3‧‧‧ second and third switches

R1, R2‧‧‧ first and second resistors

D1, D2‧‧‧ first and second diodes

C1, C2‧‧‧ first and second capacitors

150‧‧‧From conversion control circuit

Q1‧‧‧First switch

1501‧‧‧First comparator

1502‧‧‧Second comparator

R3, R4, R5, R6‧‧‧ third to sixth resistors

C3, C4‧‧‧ third and fourth capacitors

Vcc1, Vcc2‧‧‧ first and second reference voltages

Vin‧‧‧AC power signal

Vo‧‧‧DC power signal

Claims (15)

A flyback power supply system, comprising a rectification filter circuit, a pulse width modulation controller and a feedback circuit, wherein the flyback voltage supply system further comprises:
a main conversion circuit, configured to convert the signal output by the rectifying and filtering circuit into a first DC power signal according to the control of the pulse width modulation controller to drive the load;
The conversion circuit is configured to convert the signal output by the rectifying and filtering circuit into a second DC power signal and superimpose the signal to the first DC power source according to the control of the pulse width modulation controller when the load is a heavy load. a signal to jointly drive the load; and a slave switching control circuit coupled between the pulse width modulation controller and the slave conversion circuit, the slave switching control circuit including a first switch, the first switch including a control pole, An electrode and a second electrode, the first electrode is connected to the pulse width modulation controller, the second electrode is connected to the slave conversion circuit, and the slave conversion control circuit is configured to detect whether the load is a heavy load, if the load is Reloading, controlling the first switch to be turned on, to control the pulse width modulation signal of the pulse width modulation controller to enter the slave conversion circuit, so that the slave conversion circuit converts the signal output by the rectifier filter circuit into the first a DC power signal, and if the load is light or no load, controlling the first switch to be turned off to control the pulse width modulation signal of the pulse width modulation controller The conversion from the circuit, so that the conversion is not performed from the conversion circuit. The flyback power supply system of claim 1, wherein the main conversion circuit comprises:
a first transformer comprising a primary winding and a secondary winding; and a second switch controlled by the pulse width modulation controller;
The primary winding of the first transformer, the second switch and the first resistor are sequentially connected in series between the output end of the rectifying and filtering circuit and the ground. The improvement of the flyback power supply system of claim 2, wherein the main conversion circuit further comprises:
a first diode, an anode connected to a high voltage end of the secondary winding of the first transformer, a cathode outputting the first DC power signal for rectification, and a first capacitor connected to the cathode of the first diode The other end is grounded for filtering. The improvement of the flyback power supply system of claim 2, wherein the slave conversion circuit comprises:
a second transformer comprising a primary winding and a secondary winding; and a third switch connected to the slave switching control circuit for controlling the pulse width modulation signal of the pulse width modulation controller to enter the slave conversion when the slave switching control circuit controls Receiving and controlling the pulse width modulation signal when the circuit is in use;
The primary winding of the second transformer, the third switch and the second resistor are sequentially connected in series between the output end of the rectifying and filtering circuit and the ground. The improvement of the flyback power supply system of claim 4, wherein the slave conversion circuit further comprises:
a second diode, an anode connected to a high voltage end of the second winding of the second transformer, a cathode outputting the second DC power signal for rectification; and a second capacitor connected to the cathode of the second diode at one end, and One end is grounded for filtering. The improvement of the flyback power supply system of claim 4, wherein the slave control circuit detects the voltage of the first resistor and the second resistor, according to the detected first resistor and the Whether the voltage of the two resistors exceeds a predetermined ratio of the voltage of the first resistor to the second resistor at the maximum allowable load determines whether the load is a heavy load. The improvement of the flyback power supply system according to claim 4, wherein the slave control circuit detects the voltage of the feedback signal of the feedback circuit, according to whether the voltage of the detected feedback signal is A predetermined ratio of the voltage of the feedback signal when the maximum allowable load is exceeded to determine whether the load is a heavy load. The improvement of the flyback power supply system according to claim 6 or 7, wherein the slave switching control circuit further comprises:
The first comparator includes a positive input terminal, a negative input terminal and an output terminal. The negative input terminal receives the detection voltage via a third resistor and is grounded via a third capacitor, and the positive input terminal receives the first reference voltage via the fourth resistor And connecting, by the third diode and the fifth resistor, the output end of the first comparator, the anode of the third diode is connected to the positive input end, and the cathode of the third diode is connected to the fifth resistor, An output end of the first comparator is connected to the control electrode of the first switch; and a second comparator includes a positive input terminal, a negative input terminal and an output terminal, and the negative input terminal of the second comparator receives the second reference voltage, The positive input terminal of the second comparator receives the detection voltage via a sixth resistor and is grounded via a fourth capacitor, and the output of the second comparator is coupled to the negative input terminal of the first comparator. The improvement of the flyback power supply system of claim 8 is that the slave switching control circuit further comprises:
a fourth diode, the anode of the fourth diode receives the detection voltage, and the cathode of the fourth diode is connected to the third resistor for preventing signal reflow;
a fifth diode, the anode of the fifth diode receives the detection voltage, the cathode of the fourth diode is connected to the sixth resistor for preventing signal reflow; and the sixth diode, the sixth The anode of the diode is connected to the output of the second comparator, and the cathode of the sixth diode is connected to the negative input of the first comparator for preventing signal backflow. The improvement of the flyback power supply system of claim 8 is that the negative input end of the first comparator is connected to the first resistor via the third resistor to receive the detection voltage. The positive input terminal of the second comparator is connected to the second resistor via the sixth resistor to receive the detection voltage. The flyback power supply system of claim 4, wherein the pulse width modulation controller is configured to determine a condition of the load according to a voltage of the first resistor, and according to the feedback circuit The duty signal and the load condition adjust the duty ratio of the pulse width modulation signal accordingly. The flyback power supply system of claim 11, wherein the pulse width modulation controller is further configured to determine a condition of the load according to a voltage of the second resistor. The flyback power supply system of claim 4 is characterized in that the pulse width modulation controller is configured to determine the condition of the load according to the voltage of the feedback signal of the feedback circuit, and according to the load The condition of the pulse width modulation signal is adjusted accordingly. The improvement of the flyback power supply system according to claim 11 or 12 or 13 is that when the pulse width modulation controller determines that the load is a heavy load, the pulse width modulation signal is increased. The duty ratio, and when it is determined that the load is light or no load, the duty ratio of the pulse width modulation signal is reduced. The flyback power supply system of claim 11 or 12 or 13 is characterized in that the pulse width modulation controller determines the predetermined ratio based on whether the detected voltage exceeds a predetermined allowable load voltage. Whether the load is overloaded.