CN218633697U

CN218633697U - Circuit for zero-voltage starting of flyback power supply

Info

Publication number: CN218633697U
Application number: CN202222625787.3U
Authority: CN
Inventors: 孙运; 方烈义
Original assignee: On Bright Electronics Shanghai Co Ltd
Current assignee: On Bright Electronics Shanghai Co Ltd
Priority date: 2022-09-30
Filing date: 2022-09-30
Publication date: 2023-03-14
Anticipated expiration: 2032-09-30
Also published as: TWM643297U

Abstract

The utility model provides a circuit that zero voltage opened is carried out to flyback power. The flyback power supply comprises a source side winding and a secondary side winding of a transformer, a first switch and a second switch, wherein the first switch is connected between one of two connecting terminals of the source side winding and a reference ground in series, the second switch is connected between one of two connecting terminals of the secondary side winding and the reference ground in series, the circuit comprises a zero-voltage-starting flyback PWM chip, the zero-voltage-starting flyback PWM chip comprises a first zero-voltage-starting pin, a second driving pin, a power supply pin, a voltage detection pin, an over-temperature protection pin, an output feedback pin, a reference ground pin and a current detection pin, the first zero-voltage-starting pin is connected to a control terminal of the first switch, and the second driving pin is connected to a control terminal of the second switch through a transmission device and a synchronous rectification control chip. The utility model discloses a circuit that is used for carrying out zero voltage to flyback power and opens can realize flyback power's zero voltage and open, improves flyback power's efficiency and reliability.

Description

Circuit for zero-voltage starting of flyback power supply

Technical Field

The utility model relates to a circuit field especially relates to a circuit that is used for carrying out Zero Voltage (ZVS) to flyback power and opens.

Background

With the continuous development of electronic technology, electronic products, such as power supplies, have smaller volumes, and this requires higher power density and smaller size of the electronic products, such as power supplies (e.g., flyback power supplies).

However, in a power supply such as a flyback power supply, in a high frequency mode, a loss of a switch (for example, a MOS (metal oxide semiconductor) switch) is large, so that a temperature rise of the switch is high, thereby causing poor efficiency of a flyback power supply system, which is a big obstacle that restricts miniaturization of the flyback power supply.

Therefore, a method capable of improving the efficiency of the flyback power supply is required.

SUMMERY OF THE UTILITY MODEL

According to the utility model discloses an exemplary embodiment provides a circuit for carrying out Zero Voltage (ZVS) to flyback power supply and opening, flyback power supply includes the source side winding of transformer, the secondary side winding of transformer, first switch and second switch, first switch series connection is in between one of two connecting terminal of source side winding and reference ground, the second switch series connection is in one of two connecting terminal of secondary side winding and between the reference ground, its characterized in that, the circuit includes: the flyback PWM chip is started at zero voltage, and the flyback PWM chip is started at zero voltage and comprises the following components: the circuit comprises a first zero voltage starting pin, a second driving pin, a power supply pin, a voltage detection pin, an over-temperature protection pin, an output feedback pin, a reference ground pin and a current detection pin, wherein the first zero voltage starting pin is connected to a control terminal of the first switch, and the second driving pin is connected to a control terminal of the second switch through a transmission device and a synchronous rectification control chip.

According to the utility model discloses a circuit that is used for carrying out zero voltage to flyback power and opens can realize flyback power's zero voltage and open to improve flyback power's efficiency and reliability, be favorable to realizing flyback power's miniaturization.

Drawings

The invention may be better understood from the following description of particular embodiments thereof taken in conjunction with the accompanying drawings, in which:

fig. 1 shows a schematic diagram of a zero-voltage-turn-on flyback PWM chip for a circuit for zero-voltage (ZVS) turn-on of a flyback power supply according to an exemplary embodiment of the present invention.

Fig. 2 shows a schematic circuit diagram of a flyback power supply and a circuit for zero-voltage turn-on of the flyback power supply according to an exemplary embodiment of the present invention.

Fig. 3 shows a timing diagram of signals for zero voltage turn on of the flyback power supply according to an exemplary embodiment of the present invention.

Fig. 4 shows a timing diagram of signals for zero voltage turn on of the flyback power supply according to another exemplary embodiment of the present invention.

Fig. 5 shows a timing diagram of signals for zero voltage turn on of the flyback power supply according to another exemplary embodiment of the present invention.

Fig. 6 shows a timing diagram of signals for zero voltage turn on of the flyback power supply according to another exemplary embodiment of the present invention.

Fig. 7 shows a schematic block diagram of a zero-voltage turn-on flyback PWM chip according to an exemplary embodiment of the present invention.

Fig. 8 shows a schematic block diagram of a synchronous rectification control chip according to an exemplary embodiment of the present invention.

Detailed Description

Features and exemplary embodiments of various aspects of the present invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The present invention is in no way limited to any specific configuration and algorithm set forth below, but covers any modification, replacement or improvement of elements, components and algorithms without departing from the spirit of the present invention. In the drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessarily obscuring the present invention.

According to the utility model discloses a flyback power supply that is used for carrying out Zero Voltage (ZVS) to flyback power supply and opens and to be applied to can include usually: the transformer comprises a source side winding of the transformer, a secondary side winding of the transformer, a first switch and a second switch. Two connection terminals of the source winding serve as voltage input terminals to receive input power, and the input power is coupled to the secondary winding through the source winding so as to be connected to a load through the two connection terminals of the secondary winding to supply power to the load. The first switch is connected in series between one of the two connection terminals of the source winding and a reference ground to turn on or off the coupling of power from the source winding to the secondary winding. A second switch is connected in series between one of the two connection terminals of the secondary winding and ground to turn on or off the coupling of power from the secondary winding to the source winding.

According to the utility model discloses a flyback PWM chip is opened including zero voltage to the circuit that is used for carrying out zero voltage to flyback power supply and opens.

Fig. 1 shows a schematic diagram of a zero-voltage-turn-on flyback PWM chip 100 for a circuit for zero-voltage-turn-on of a flyback power supply according to an exemplary embodiment of the present invention.

As shown in fig. 1, the zero voltage turn-on flyback PWM chip 100 includes: the driving circuit comprises a first zero voltage starting pin GATE, a second driving pin SRC, a power supply pin VDD, a voltage detection pin DEM, an over-temperature protection pin OTP, an output feedback pin FB, a ground reference pin GND and a current detection pin CS.

It should be understood that the pin of the zero voltage turn-on flyback PWM chip 100 is not limited to the above listed pins, but may also include any other pins. The setting position and the sequence of the pins of the zero-voltage turn-on flyback PWM chip 100 are not limited to the position and the sequence shown in fig. 1, and the positions and the sequences of the respective pins (for example, the positions and the sequences of the pins shown in fig. 2 below) may be set according to actual needs.

Fig. 2 shows a schematic circuit diagram of the flyback power supply 20 and the circuit 10 for zero voltage turn-on of the flyback power supply 20 according to an exemplary embodiment of the present invention.

As shown in fig. 2, the flyback power supply 20 includes a source side winding Pri of a transformer, a secondary side winding Sec of the transformer, a first switch Q1, and a second switch Q2.

The first switch Q1 is connected in series between one of the two connection terminals of the source winding Pri and the reference ground. The other of the two connection terminals of the source winding Pri receives an input voltage V _bulk Input voltage V _bulk Is to filter an external input power (e.g., an alternating input power (AC IN) shown IN fig. 2) through an electromagnetic interference (EMI) filter and pass through a rectifying circuit (e.g., by each of a diode D, a capacitor C IN fig. 2) _bulk A rectifier circuit) rectifies the filtered external input power to generate a voltage.

The second switch Q2 is connected in series between one of the two connection terminals of the secondary winding Sec, between which the energy storage capacitor Cout is connected, and the reference ground. Two connection terminals of the secondary winding Sec output an output voltage (e.g., DC Out in fig. 2).

As shown in fig. 2, the flyback power supply 20 further includes a third resistor R3 connected in series between the first switch Q and the ground reference, and other devices (e.g., devices shown generally as resistor R and capacitor C in fig. 2, TL 431, etc., which are not limited herein) for implementing power supply of the flyback power supply.

The following describes in detail an exemplary embodiment of a circuit 10 for zero voltage turn-on of the flyback power supply 20 according to the present invention, and the connection between this circuit 10 and the flyback power supply 20.

A first zero voltage turn-on pin GATE of the zero voltage turn-on flyback PWM chip 100 of the circuit 10 is connected to a control terminal of the first switch Q1, and a second drive pin SRC is connected to a control terminal of the second switch Q2 via a transmission device 300 and a Synchronous Rectification (SR) control chip 200, as shown in fig. 2.

Here, as an example, the transmission device 300 may be at least one of: magnetic coupling, common mode inductors, transformers, and optocouplers. However, it should be understood that the above is merely an example of the transmission device 300, which may be any device capable of transmitting signals in real time.

In one embodiment, to power the zero-voltage-turn-on flyback PWM chip 100, the circuit 10 according to an exemplary embodiment of the present invention may further include: a chip supply winding Aux, a first diode D1 and a first capacitor C1.

The chip power supply winding Aux may be coupled to the source side winding Pri and the secondary side winding Sec of the flyback power supply 20. The first connection terminal of the chip power supply winding Aux may be connected to the first connection terminal of the first diode D1, the second connection terminal of the first diode D1 may be connected to the first connection terminal of the first capacitor C1, and the second connection terminal of the first capacitor C1 and the second connection terminal of the chip power supply winding Aux may be connected to the reference ground. The supply pin VDD of the zero-voltage-turn-on flyback PWM chip 100 may be connected to the first connection terminal of the capacitor C1 to receive the chip supply voltage Vaux.

In one embodiment, to input voltage V to flyback power supply 20 _bulk Output voltage DC Out and the resonance waveform between source winding Pri and the first switch Q1 parasitic capacitance are detected, according to the present invention, the circuit 10 of the exemplary embodiment may further include: a first resistor R1 and a second resistor R2. The first and second resistors R1 and R2 may be connected in series between the first connection terminal of the chip supply winding Aux and the reference ground. The voltage detection pin DEM of the zero voltage turn-on flyback PWM chip 100 may be connected to a connection node between the first resistor R1 and the second resistor R2.

In one embodiment, in order to perform over-temperature protection (OTP) on the zero-voltage-turn flyback PWM chip 100, the circuit 10 according to the exemplary embodiment of the present invention may further include: a thermistor NTC. The over-temperature protection pin OTP of the zero voltage turn-on flyback PWM chip 100 may be connected to a first connection terminal of the thermistor NTC, and a second connection terminal of the thermistor NTC may be connected to the reference ground. For example, the OTP pin draws a rated current through the external NTC resistor to ground, and the higher the temperature is, the smaller the resistance value of the thermistor NTC and thus the lower the voltage across the thermistor NTC. Thus, whether the zero voltage turn-on flyback PWM chip 100 is over-temperature can be detected.

In one embodiment, in order to obtain a feedback signal sampled by the output voltage of the flyback power supply 20, the circuit 10 according to an exemplary embodiment of the present invention may further include: and an optical coupler OC. The output feedback pin FB of the zero-voltage-turn-on flyback PWM chip 100 is connected to a first connection terminal of the optocoupler OC, and a second connection terminal of the optocoupler OC is connected to the ground reference. For example, the optical coupler OC may be connected to the TL 431 on the secondary side in fig. 2, and thus the output feedback pin may detect the output voltage according to the magnitude of the current received by the optical coupler OC from the TL 431.

In addition, the ground reference pin GND of the zero voltage turn-on flyback PWM chip 100 may be connected to the ground reference. It should be appreciated that the reference ground to which the associated pins and devices of the zero voltage turn-on flyback PWM chip 100 are connected is the same as the reference ground of the flyback power supply 20.

In addition, a current detection pin CS of the zero voltage turn-on flyback PWM chip 100 may be connected to a connection node between the first switch Q1 and the third resistor R3 to detect a source-side current of the flyback power supply 20.

Normally, in a state where the first switch Q1 is turned on, the source side winding Pri of the flyback power supply 20 stores energy. During a demagnetization phase after the first switch Q1 is turned off, the energy stored in the source winding Pri is coupled and transferred to the secondary winding Sec, and the voltage VDS between the drain and the source of the first switch is kept at a high constant voltage. In the state where the first switch Q1 is turned off, after demagnetization is completed, in a resonance stage where resonance occurs between the source side winding Pri and the parasitic capacitance of the first switch Q1, the voltage VDS between the drain and the source of the first switch Q1 will oscillate.

According to the utility model discloses a zero voltage of circuit 10 opens flyback PWM chip 100's first zero voltage and opens pin GATE can control the switch-on and the disconnection of first switch Q1, and second drive pin SRC can be used for controlling the switch-on and the disconnection of second switch Q2.

The zero-voltage-turn-on flyback PWM chip 100 may detect the input voltage V of the flyback power supply 20 through the voltage detection pin DEM by coupling the chip power supply winding Aux and the source side winding Pri through the voltage detection pin DEM in a state where the first zero-voltage-turn-on pin GATE controls the first switch Q1 to be turned on _bulk 。

At a demagnetization stage after the first zero-voltage turn-on pin GATE of the zero-voltage turn-on flyback PWM chip 100 controls the first switch Q1 to be turned off, the voltage detection pin DEM may detect the output voltage DC Out of the flyback power supply 20 through the coupling of the chip power supply winding Aux and the secondary winding Sec.

At a resonance stage where resonance occurs between a source side winding Pri and a parasitic capacitance of a first switch Q1 after a demagnetization stage in a state where the first zero voltage turn-on pin GATE of the zero voltage turn-on flyback PWM chip 100 controls the first switch Q1 to be turned off, the voltage detection pin DEM may detect a resonance waveform through coupling of the chip power supply winding Aux and the source side winding Pri.

Therefore, the zero-voltage-start flyback PWM chip 100 may control the second driving pin SRC to output a corresponding signal to turn on the second switch Q2 in the resonance stage, so that the secondary winding Sec couples energy to the source winding Pri, thereby enhancing resonance between the source winding Pri and the first switch Q1; and according to the resonance waveform detected by the voltage detection pin DEM, the second switch Q2 is turned off, and the first switch Q1 is turned on at a proper resonance phase (for example, near the valley of the resonance waveform), so that the first switch Q1 is turned on at zero voltage. Therefore, the efficiency and the reliability of the flyback power supply are improved, and the flyback power supply is favorably miniaturized.

In addition, the zero-voltage-turn-on flyback PWM chip 100 may be controlled by the first zero-voltage-turn-on pin GATE and the second driving pin SRC to make the first switch Q1 and the second switch Q2 not be turned on at the same time, so as to avoid a problem of a machine explosion caused by, for example, simultaneous turn-on of MOS (metal oxide semiconductor) switches, and make the safety of the flyback power supply higher.

Referring to fig. 3, the GATE signal GATE output from the first zero voltage turn-on pin GATE of the zero voltage turn-on flyback PWM chip 100 is used to control the turn-on or turn-off of the first switch Q1, and in the example of fig. 3, the first switch Q1 may be a MOS switch that is turned on at a high level.

The control signal SRC output by the second driving pin SRC of the zero-voltage-turn-on flyback PWM chip 100 is used to control the second switch Q2 to be turned on or off, and in the example of fig. 3, the second switch Q2 may also be a MOS switch turned on at a high level.

The GATE control pin SR GATE of the synchronous rectification chip 200 on the secondary side of the flyback power supply 20 may generate a GATE control signal SR GATE (secondary side SR GATE in fig. 3) output to the GATE of the second switch Q2 according to the control signal SRC.

In other words, in the embodiment of fig. 3, the on or off of the second switch Q2 is directly and only controlled by the control signal SRC. That is, in the demagnetization stage and the resonance stage, the zero-voltage-turn-on flyback PWM chip 100 may control the on or off of the second switch Q2 through the control signal SRC.

Here, by turning on the flyback PWM chip 100 by a zero voltage in the resonance phase to control the second switch Q2 to be turned on, the power stored in the secondary storage capacitor Cout can be coupled from the secondary winding Sec to the source winding Pri, thereby increasing the resonance between the source winding Pri and the parasitic capacitance of the first switch Q1. After increasing the resonance, the zero-voltage-turn-on flyback PWM chip 100 may control the second switch Q2 to be turned off and turn on the first switch Q1 at an appropriate resonance phase (e.g., near a valley voltage of the voltage VDS) to achieve zero-voltage turn-on of the first switch Q1 (i.e., the flyback power supply 20).

It should be understood that the control signal SRC shown in fig. 3 is only an example, and the control signal SRC may also be in other forms of control signals, for example, in a pulse form, as shown in fig. 4.

Fig. 4 shows a timing diagram of signals for zero voltage turn on of the flyback power supply in accordance with another exemplary embodiment of the present invention.

The timing diagram of fig. 4 is similar to that of fig. 3, except that: the control signal SRC in fig. 4 is a pulse signal, and the GATE control pin SR GATE of the synchronous rectification chip 200 on the secondary side of the flyback power supply 20 generates the GATE control signal SR GATE to be output to the GATE of the second switch Q2 according to the pulse-type control signal SRC.

The timing diagram of fig. 5 is similar to that of fig. 3, except that: the control signal SRC in fig. 5 controls the on and off of the second switch Q2 only during the resonance phase. The GATE control pin SR GATE of the synchronous rectification chip 200 on the secondary side of the flyback power supply 20 generates a GATE control signal SR GATE output to the GATE of the second switch Q2 at a demagnetization stage, and generates a GATE control signal SR GATE output to the GATE of the second switch Q2 according to the control signal SRC at a resonance stage.

Here, the control signal SRC shown in fig. 5 is also only an example, and the control signal SRC may also be in other forms of control signals, for example, a pulse form, as shown in fig. 6.

The timing diagram of fig. 6 is similar to that of fig. 5, except that: the control signal SRC in fig. 6 is a pulse signal. The GATE control pin SR GATE of the synchronous rectification chip 200 on the secondary side of the flyback power supply 20 generates the GATE control signal SR GATE output to the GATE of the second switch Q2 at a demagnetization stage, and generates the GATE control signal SR GATE output to the GATE of the second switch Q2 according to the control signal SRC in the form of a pulse at a resonance stage.

Fig. 7 shows a schematic block diagram of a zero-voltage turn-on flyback PWM chip 100 according to an exemplary embodiment of the present invention.

As shown in fig. 7, the zero-voltage turn-on flyback PWM chip 100 according to an exemplary embodiment of the present invention may include: a main driving unit 110, an SRC control unit 120, an IC power supply unit 130, a voltage detection unit 140, an OTP protection unit 150, and a main controller 160.

The main driving unit 110 is connected to a first zero voltage turn-on pin GATE, the SRC control unit 120 is connected to a second driving pin SRC, the IC supply voltage 130 is connected to a supply pin VDD, the voltage detection unit 140 is connected to a voltage detection pin DEM, and the OTP protection unit 150 is connected to an over-temperature protection pin OTP.

The main controller 160 is connected to the main driving unit 110, the SRC control unit 120, the IC power supply unit 130, the voltage detection unit 140, the OTP protection unit 150, the output feedback pin FB, and the current detection pin CS to receive a chip supply voltage provided by the IC power supply unit 130 through the power supply pin VCC, a signal detected through the voltage detection pin DEM provided by the voltage detection unit 140, a signal detected through the over-temperature protection pin OTP provided by the OTP protection unit 150, a signal detected through the output feedback pin FB, and a signal detected through the current detection pin CS, and to provide control signals to the main driving unit 110 and the SRC control unit 120 according to the signals to control the on and off of the first switch Q1 and the second switch Q2 via the first zero voltage start pin GATE and the second driving pin SRC.

Fig. 8 shows a schematic block diagram of a synchronous rectification control chip 200 according to an exemplary embodiment of the present invention.

As shown in fig. 8, the synchronous rectification control chip 200 may include a voltage detection pin VD, a GATE control pin SR GATE, a power supply pin VCC, a signal reception pin RX, a ground reference pin GND, a voltage detection unit 210, an SR driving unit 220, a power supply unit 230, a reception unit 240, and an SR controller 250.

The voltage detection pin VD is connected to the voltage detection unit 210 to detect the drain voltage of the second switch Q2, the rising slope of the drain voltage, and the falling slope of the drain voltage.

The GATE control pin SR GATE is connected to the SR driving unit 220 to output the GATE control signal SR GATE to the GATE of the second switch Q2.

The power supply pin VCC is connected to the power supply unit 230 to receive power from the outside to supply power to the synchronous rectification control chip 200.

The signal receiving pin RX is connected to the receiving unit 240 to receive the control signal SRC output from the second driving pin SRC of the zero-voltage turn-on flyback PWM chip 100.

The ground reference pin GND is connected to ground reference.

The SR controller 250 is connected to the voltage detection unit 210, the SR driving unit 220, the power supply unit 230, and the reception unit 240 to receive corresponding signals therefrom and provide a control signal to the SR driving unit 220 to generate a GATE control signal SR GATE output to the GATE of the second switch Q2 via a GATE control pin SR GATE.

It should be understood that the above method of zero voltage turn-on and the structure of zero voltage turn-on flyback PWM chip and synchronous rectification control chip for flyback power supply are only examples, and other structures of zero voltage turn-on and zero voltage turn-on flyback PWM chip and synchronous rectification control chip for flyback power supply can be realized by applying the circuit according to the embodiment of the present invention in any other way according to actual needs.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. For example, the algorithms described in the specific embodiments may be modified without departing from the basic spirit of the invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. A circuit for zero voltage turn-on of a flyback power supply, the flyback power supply including a source side winding of a transformer, a secondary side winding of the transformer, a first switch and a second switch, the first switch being connected in series between one of two connection terminals of the source side winding and a reference ground, the second switch being connected in series between one of two connection terminals of the secondary side winding and the reference ground, the circuit comprising: the zero voltage turns on the flyback PWM chip,

the zero voltage turn-on flyback PWM chip includes: a first zero voltage turn-on pin, a second drive pin, a power supply pin, a voltage detection pin, an over-temperature protection pin, an output feedback pin, a reference ground pin and a current detection pin,

wherein the first zero voltage turn-on pin is connected to a control terminal of the first switch, and the second drive pin is connected to a control terminal of the second switch via a transmission device and a synchronous rectification control chip.

2. The circuit of claim 1, wherein the pass device is at least one of: magnetic coupling, common mode inductor, transformer, and optical coupling.

3. The circuit of claim 1, further comprising: a chip supply winding, a first diode and a first capacitor,

the chip power supply winding is coupled with the source winding and the secondary winding, a first connection terminal of the chip power supply winding is connected to a first connection terminal of the first diode, a second connection terminal of the first diode is connected to a first connection terminal of the first capacitor, a second connection terminal of the first capacitor and a second connection terminal of the chip power supply winding are connected to the reference ground,

wherein the power supply pin is connected to a first connection terminal of the capacitor.

4. The circuit of claim 3, further comprising: a first resistor and a second resistor, wherein the first resistor and the second resistor are connected in series,

the first resistor and the second resistor are connected in series between a first connection terminal of the chip supply winding and the reference ground,

wherein the voltage detection pin is connected to a connection node between the first resistor and the second resistor.

5. The circuit of claim 1, further comprising: a thermal resistor is arranged on the base plate,

wherein the over-temperature protection pin is connected to a first connection terminal of the thermistor, and a second connection terminal of the thermistor is connected to the reference ground.

6. The circuit of claim 1, further comprising: the optical coupler is arranged on the optical disk,

wherein the output feedback pin is connected to a first connection terminal of the optocoupler, and a second connection terminal of the optocoupler is connected to the reference ground.

7. The circuit of claim 1, wherein the ground reference pin is connected to the ground reference.

8. The circuit of claim 1, wherein the flyback power supply further comprises a third resistor,

the third resistor is connected in series between the first switch and the reference ground,

wherein the current detection pin is connected to a connection node between the first switch and the third resistor.