TWI635699B - Flyback power converter and synchronous rectification (sr) switch control circuit and power switch control circuit thereof - Google Patents

Flyback power converter and synchronous rectification (sr) switch control circuit and power switch control circuit thereof Download PDF

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Publication number
TWI635699B
TWI635699B TW106125968A TW106125968A TWI635699B TW I635699 B TWI635699 B TW I635699B TW 106125968 A TW106125968 A TW 106125968A TW 106125968 A TW106125968 A TW 106125968A TW I635699 B TWI635699 B TW I635699B
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Taiwan
Prior art keywords
signal
feedback
pulse
circuit
switch control
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TW106125968A
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Chinese (zh)
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TW201818643A (en
Inventor
楊大勇
林梓誠
曾兵
羅立狄
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立錡科技股份有限公司
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Priority to US201662421945P priority Critical
Priority to US62/421,945 priority
Priority to US201762486784P priority
Priority to US62/486,784 priority
Application filed by 立錡科技股份有限公司 filed Critical 立錡科技股份有限公司
Priority claimed from US15/809,595 external-priority patent/US10014786B2/en
Publication of TW201818643A publication Critical patent/TW201818643A/en
Application granted granted Critical
Publication of TWI635699B publication Critical patent/TWI635699B/en

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Abstract

The invention provides a flyback power supply circuit, an SR switch control circuit and a power switch control circuit. The flyback power supply circuit includes a transformer, a power switch, a power switch control circuit, a synchronous rectification (SR) switch, an SR switch control circuit, and a signal coupling circuit. The signal coupling circuit has a primary side electrically connected to the power switch control circuit and a secondary side electrically connected to the SR switch control circuit. In the different periods of non-overlapping, the primary side and the secondary side respectively receive different signals generated by the power switch control circuit and the SR switch control circuit, and the signal coupling circuit is sensed and converted in a non-contact manner. A corresponding signal is generated on the secondary side and the primary side.

Description

Flyback power supply circuit and its SR switch control circuit and power switch control circuit

The invention relates to a flyback power supply circuit and an SR switch control circuit thereof and a power switch control circuit, in particular to a signal coupling circuit coupled between the primary side and the secondary side of the transformer in a non-contact manner. In the different time periods that do not overlap each other, the same group of 埠 is used, and the signals of the primary side are respectively induced and converted, and then transmitted to the secondary side, and the signal of the secondary side is induced and converted, and then transmitted to the primary side. Power supply circuit and its SR switch control circuit and power switch control circuit.

1 shows a prior art flyback power supply circuit 100 in which an alternating voltage Vac is rectified via a rectifying circuit 101 to generate an input voltage Vin. The primary side winding W1 of the transformer 102 receives the input voltage Vin. The power-on control circuit 105 obtains the feedback voltage signal COMP related to the output voltage Vout by the optical coupling circuit 104 or from the auxiliary winding mode (not shown), and obtains the related power flow switch from the current sensing circuit 106. The current of the SW current senses the signal CS and generates a PWM signal. The PWM control circuit 105 then generates a power switch control signal Spwm according to the PWM signal to control the operation of the power switch SW.

Continuing to refer to FIG. 1, in order to improve the power conversion efficiency, the secondary side winding W2 of the flyback power supply circuit 100 is electrically connected to a synchronous rectification (SR) switching circuit 108, and the synchronous rectification control circuit 107 is based on the synchronous rectification switching circuit. The voltage across 108 is controlled by a synchronization signal SYNC such that the secondary winding W2 is turned on when the primary winding W1 is not conducting to convert the input voltage Vin into the output voltage Vout. If the secondary side winding W2 is still turned on when the primary side winding W1 is turned on, it may cause a short through condition. However, in some operating states, such as continuous conduction mode (CCM), the flyback power supply circuit 100 does not have the switch in the synchronous rectification switch circuit 108 yet when the primary side winding W1 is turned on. The possibility of conduction causes the secondary winding W2 to be turned on when the primary winding W1 is turned on, and the flyback power supply circuit 100 is short-circuited, causing circuit damage.

The PWM control circuit 105 generates a notification signal PLS, inputs it to the coupling circuit 103, and then generates a synchronization signal SYNC by the coupling circuit 103 to confirm that the SR switch circuit 108 is not conducting, and then turns on the power switch SW. In addition, the optical coupling circuit 104 and the coupling circuit 103 are two separate circuits for respectively transmitting the output voltage related information generated by the secondary side to the PWM controller 105 on the primary side, and the power switch control signal generated on the primary side. The Spwm related information is transmitted to the SR control circuit 107 on the secondary side. This arrangement makes the space for circuit miniaturization limited.

In view of the above, the present invention is directed to the above-mentioned prior art deficiencies, and provides a flyback power supply circuit, an SR switch control circuit thereof and a power switch control circuit. The flyback power supply circuit has a signal coupling circuit coupled to the primary side of the transformer. Between the secondary side and the secondary side, the signal of the primary side is transmitted to the secondary side and the signal of the secondary side is transmitted to the flyback power supply circuit of the primary side in the same period of time that does not overlap each other. And its SR switch control circuit and power switch control circuit.

In one aspect, the present invention provides a flyback power supply circuit comprising: a transformer having a primary winding to receive an input voltage; and a secondary winding to generate an output voltage; a power switch, And coupled to the primary side winding for controlling the on-time of the primary winding; a power switch control circuit is located on the primary side of the transformer for generating a power switch control signal according to a coupled feedback signal to control the a power switch and a synchronous rectification pulse signal; a synchronous rectification (SR) switch coupled to the secondary side winding for controlling an on-time of the secondary winding to correspond to the primary winding Conducting non-conducting; an SR switch control circuit, located on the secondary side of the transformer, coupled to the SR switch, for receiving a coupled synchronous rectification signal in a normal operation mode to control the SR switch, and according to The output voltage generates a feedback pulse signal; and a signal coupling circuit coupled to the SR switch control circuit and the power switch Between the circuit, the synchronous rectification pulse signal is inductively generated in a non-contact manner to generate the coupled synchronous rectification signal, and the feedback pulse signal is inductively generated to generate the coupled feedback signal; wherein The signal coupling circuit has a primary side 埠 and a secondary side 埠, the primary side 埠 is located on the primary side of the transformer, and the secondary side 埠 is located on the secondary side of the transformer, wherein the primary side 埠 does not overlap each other Receiving the synchronous rectification pulse signal and generating the coupling feedback signal respectively in different periods of time, and the secondary side generates the coupled synchronous rectification signal and receiving the feedback separately in different periods of the corresponding non-overlapping Pulse signal.

In one preferred embodiment, the signal coupling circuit includes a pulse transformer or a pulse optocoupler, and the input and output signals of the pulse transformer and the pulse optocoupler are signals in the form of pulses.

In a preferred embodiment, during a period of operation, the synchronous rectification pulse signal has a synchronous rectification pulse before the power switch is turned on; and the SR switch control circuit is coupled according to the synchronization rectification pulse. The synchronous rectification signal does not turn on the SR switch, so that the SR switch does not conduct until the power switch is turned on.

In a preferred embodiment, during an operation period, the SR switch control circuit flows through the SR according to a secondary winding current flowing through one of the secondary windings before the SR switch is turned on. One of the switches, the SR switch current, or the cross-voltage of the secondary winding or the SR switch, to confirm that the power switch is not conducting.

In a preferred embodiment, the feedback pulse signal includes at least one feedback pulse having one or a combination of the following: a feedback pulse level, a feedback pulse length, or a feedback pulse. a number for indicating the output voltage; and flowing through a power switch current of the power switch, corresponding to the feedback pulse level, the length of the feedback pulse, the number of feedback pulses, or a combination thereof

In a preferred embodiment, the synchronous rectification pulse signal has a synchronous rectification pulse, and the feedback pulse signal has a feedback pulse; wherein the synchronous rectification pulse and the feedback pulse have a pulse duration shorter than one. Micro-second.

In a preferred embodiment, the feedback pulse signal has a feedback pulse during a period of operation, and the feedback pulse is synchronized by a synchronization rectification pulse generated by the synchronous rectification pulse signal. Produced after the period.

In the foregoing embodiment, after the synchronous rectification pulse of the synchronous rectification pulse signal is generated, the next synchronization rectification pulse is not generated during a synchronization threshold, and the SR switch control circuit generates the feedback pulse, and then The feedback pulse is periodically generated during a feedback cycle until the power switch control circuit generates the synchronous rectification pulse.

In the foregoing embodiments, the synchronization preset period is related to the output voltage.

In a preferred embodiment, during the operation, the synchronous rectification pulse signal has a synchronous rectification pulse, and the synchronous rectification pulse is generated after one feedback pulse of the feedback pulse signal is generated. Generated after the preset period.

In the foregoing embodiment, after the feedback pulse of the feedback pulse signal is generated, the next feedback pulse is not generated during a feedback threshold, and the power switch control circuit generates the synchronization. The rectified pulse is pulsed, and then the synchronous rectification pulse is periodically generated in a synchronization cycle until the SR switch control circuit generates the feedback pulse.

In the foregoing embodiment, the feedback preset period is related to the output voltage.

In a preferred embodiment, the SR switch control circuit includes: an output voltage sampling circuit for sampling and amplifying the output voltage to generate an output voltage sampling signal; a feedback pulse signal generating circuit coupled to The output voltage sampling circuit and the secondary side 用以 are configured to generate the feedback pulse signal according to the output voltage sampling signal; an SR comparator coupled to the secondary side , for synchronizing according to the coupling The rectified signal and a synchronous reference signal generate a synchronous comparison signal; an SR timing circuit is coupled to the comparator for generating a synchronous preset period after timing a synchronization preset period according to the synchronous comparison signal And an SR switch control signal generating circuit coupled to the comparator and the SR switch for generating an SR switch control signal to control the SR switch according to the synchronous comparison signal.

In a preferred embodiment, the power switch control circuit includes: a power switch control signal generating circuit coupled to the power switch for generating the power switch control signal according to a sample feedback signal; The feedback signal sampling and holding circuit is coupled between the power switch control signal generating circuit and the primary side, for generating the sample feedback signal according to the coupled feedback signal; and a feedback timing circuit, and the The power switch control signal generating circuit and the feedback signal sample and hold circuit are coupled to generate a sample signal and a clear signal according to the power switch control signal and the coupled feedback signal, wherein the feedback signal sample and hold circuit And converting the coupled feedback signal to the sampled feedback signal according to the sampled signal and the clear signal.

In the foregoing embodiment, the feedback signal sampling and holding circuit includes: a shielding circuit coupled to the power switch control signal generating circuit and the primary side 遮蔽 for shielding the signal according to one of the power switch control signals And preventing the feedback signal sampling and holding circuit from receiving the synchronous rectification pulse signal from the primary side in a masking period; and a sampling feedback signal generating circuit coupled to the The masking circuit and the power switch control signal generating circuit are configured to generate the sample feedback signal according to the coupled feedback signal, a clear signal, and a sample signal.

In another aspect, the present invention provides an SR switch control circuit for a flyback power supply circuit, the flyback power supply circuit including a transformer having a primary winding to receive an input voltage; and a secondary winding To generate an output voltage; a power switch coupled to the primary side winding for controlling the on-time of the primary winding; a power switch control circuit located on the primary side of the transformer for feedback based on a coupling a signal, a power switch control signal is generated to control the power switch, and a synchronous rectification pulse signal is generated; a synchronous rectification (SR) switch coupled to the secondary side winding for controlling the secondary winding The on-time is to be turned on when the primary winding is not conducting; the SR switch control circuit is located on the secondary side of the transformer and coupled to the SR switch for receiving a coupling synchronization in a normal operation mode. Rectifying the signal to control the SR switch, and generating a feedback pulse signal according to the output voltage; and a signal coupling circuit coupled Between the SR switch control circuit and the power switch control circuit, the synchronous rectification pulse signal is inductively generated in a non-contact manner to generate the coupled synchronous rectification signal, and the feedback pulse signal is in a non-contact manner. Inductively generating the coupled feedback signal; wherein the signal coupling circuit has a primary side turn and a secondary side turn, the primary side turn is located on a primary side of the transformer, and the secondary side turn is located on a secondary side of the transformer And the primary side is respectively received in the different time periods that do not overlap each other, respectively receiving the synchronous rectification pulse signal and generating the coupling feedback signal, and the secondary side is respectively generated in different periods of the corresponding non-overlapping The coupled synchronous rectification signal and the receiving the feedback pulse signal; the SR switch control circuit includes: an output voltage sampling circuit for sampling and amplifying the output voltage to generate an output voltage sampling signal; a feedback pulse signal generating circuit, The signal is coupled between the output voltage sampling circuit and the secondary side, for generating the feedback pulse signal according to the output voltage sampling signal; SR comparator, coupled to the secondary side port is coupled to the synchronous rectifier in accordance with a synchronizing signal and the reference signal, generating a synchronization signal comparison; SR a timer circuit, And the comparator is coupled to generate a synchronous preset period timing signal after timing a synchronization preset period according to the synchronous comparison signal; and an SR switch control signal generating circuit, and the comparator and the SR switch The coupling is configured to generate an SR switch control signal according to the synchronous comparison signal to control the SR switch.

In one preferred embodiment, the signal coupling circuit includes a pulse transformer or a pulse optocoupler, and the input and output signals of the pulse transformer and the pulse optocoupler are signals in the form of pulses.

In a preferred embodiment, during a period of operation, the synchronous rectification pulse signal has a synchronous rectification pulse before the power switch is turned on; and the SR switch control circuit is coupled according to the synchronization rectification pulse. The synchronous rectification signal does not turn on the SR switch, so that the SR switch does not conduct until the power switch is turned on.

In a preferred embodiment, during an operation period, the SR switch control circuit flows through the SR according to a secondary winding current flowing through one of the secondary windings before the SR switch is turned on. One of the switches, the SR switch current, or the cross-voltage of the secondary winding or the SR switch, to confirm that the power switch is not conducting.

In a preferred embodiment, the feedback pulse signal includes at least one feedback pulse having one or a combination of the following: a feedback pulse level, a feedback pulse length, or a feedback pulse. The number is used to indicate the output voltage; and a power switch current flowing through one of the power switches corresponds to the feedback pulse level, the feedback pulse time length, the number of feedback pulses, or a combination thereof.

In a preferred embodiment, the synchronous rectification pulse signal has a synchronous rectification pulse, and the feedback pulse signal has a feedback pulse; wherein the synchronous rectification pulse and the feedback pulse have a pulse duration shorter than one. Micro-second.

In a preferred embodiment, the feedback pulse signal has a feedback pulse during a period of operation, and the feedback pulse is synchronized by a synchronization rectification pulse generated by the synchronous rectification pulse signal. Produced after the period.

In the foregoing embodiment, after the synchronous rectification pulse of the synchronous rectification pulse signal is generated, the next synchronization rectification pulse is not generated during a synchronization threshold, and the SR switch control circuit generates the feedback pulse, and then The feedback pulse is periodically generated during a feedback cycle until the power switch control circuit generates the synchronous rectification pulse.

In the foregoing embodiments, the synchronization preset period is related to the output voltage.

In a preferred embodiment, during the operation, the synchronous rectification pulse signal has a synchronous rectification pulse, and the synchronous rectification pulse is generated after one feedback pulse of the feedback pulse signal is generated. Generated after the preset period.

In the foregoing embodiment, after the feedback pulse of the feedback pulse signal is generated, the next feedback pulse is not generated during a feedback threshold, and the power switch control circuit generates the synchronous rectification pulse, and then The synchronous rectification pulse is periodically generated in a synchronization cycle until the SR switch control circuit generates the feedback pulse.

In the foregoing embodiment, the feedback preset period is related to the output voltage.

In a preferred embodiment, the power switch control circuit includes: a power switch control signal generating circuit coupled to the power switch for generating the power switch control signal according to a sample feedback signal; The feedback signal sampling and holding circuit is coupled between the power switch control signal generating circuit and the primary side, for generating the sample feedback signal according to the coupled feedback signal; and a feedback timing circuit, and the The power switch control signal generating circuit and the feedback signal sample and hold circuit are coupled to generate a sample signal and a clear signal according to the power switch control signal and the coupled feedback signal, wherein the feedback signal sample and hold circuit And converting the coupled feedback signal to the sampled feedback signal according to the sampled signal and the clear signal.

In the foregoing embodiment, the feedback signal sampling and holding circuit includes: a shielding circuit coupled to the power switch control signal generating circuit and the primary side 遮蔽 for shielding the signal according to one of the power switch control signals And preventing the feedback signal sampling and holding circuit from receiving the synchronous rectification pulse signal from the primary side during an occlusion period; and a sampling feedback signal generating circuit coupled to the shielding circuit and the power switch control signal to generate The circuit generates a sample feedback signal according to the coupled feedback signal, a clear signal, and a sample signal.

In another aspect, the present invention provides a power switch control circuit for a flyback power supply circuit, the flyback power supply circuit including a transformer having a primary winding to receive an input voltage; and a secondary winding a power switch coupled to the primary side winding for controlling the on-time of the primary side winding; the power switch control circuit is located on a primary side of the transformer for feedback coupling according to a coupling a signal, a power switch control signal is generated to control the power switch, and a synchronous rectification pulse signal is generated; a synchronous rectification (SR) switch coupled to the secondary side winding for controlling the secondary winding The on-time is corresponding to the conduction when the primary winding is not conducting; an SR switch control circuit is located on the secondary side of the transformer and coupled to the SR switch for receiving a coupling synchronization in a normal operation mode Rectifying the signal to control the SR switch, and generating a feedback pulse signal according to the output voltage; and a signal coupling circuit, Connected between the SR switch control circuit and the power switch control circuit, the synchronous rectification pulse signal is inductively generated in a non-contact manner to generate the coupled synchronous rectification signal, and the feedback pulse signal is in a non-contact manner. Inductively generating the coupled feedback signal; wherein the signal coupling circuit has a primary side 一 and a secondary side 埠, the primary side 埠 is located on a primary side of the transformer, and the secondary side 埠 is located in the transformer twice a side, wherein the primary side is in different time periods that do not overlap each other, respectively receiving the synchronous rectified pulse signal and generating the coupled feedback signal, and the secondary side is in different periods of the corresponding non-overlapping, respectively Generating the coupled synchronous rectification signal and receiving the feedback pulse signal; the power switch control circuit includes: a power switch control signal generating electricity The circuit is coupled to the power switch for generating a power switch control signal according to a sampled feedback signal; a feedback signal sample and hold circuit coupled to the power switch control signal generating circuit and the primary side And generating a sampling feedback signal according to the coupled feedback signal; and a feedback timing circuit coupled to the power switch control signal generating circuit and the feedback signal sampling and holding circuit for using the power switch The control signal and the coupled feedback signal are generated to generate a sample signal and a clear signal, wherein the feedback signal sample and hold circuit converts the coupled feedback signal into the sampled feedback signal according to the sampled signal and the clear signal .

In a preferred embodiment, the feedback signal sampling and holding circuit includes: a shielding circuit coupled to the power switch control signal generating circuit and the primary side switch for controlling the signal according to the power switch a masking signal for preventing the feedback signal sampling and holding circuit from receiving the synchronous rectification pulse signal from the primary side during a masking period; and a sampling feedback signal generating circuit coupled to the shielding circuit and the power switch The control signal generating circuit generates the sample feedback signal according to the coupled feedback signal, a clear signal, and a sample signal.

In one preferred embodiment, the signal coupling circuit includes a pulse transformer or a pulse optocoupler, and the input and output signals of the pulse transformer and the pulse optocoupler are signals in the form of pulses.

In a preferred embodiment, during a period of operation, the synchronous rectification pulse signal has a synchronous rectification pulse before the power switch is turned on; and the SR switch control circuit is coupled according to the synchronization rectification pulse. The synchronous rectification signal does not turn on the SR switch, so that the SR switch does not conduct until the power switch is turned on.

In a preferred embodiment, during an operation period, the SR switch control circuit flows through the SR according to a secondary winding current flowing through one of the secondary windings before the SR switch is turned on. One of the switches, the SR switch current, or the cross-voltage of the secondary winding or the SR switch, to confirm that the power switch is not conducting.

In a preferred embodiment, the feedback pulse signal includes at least one feedback pulse having one or a combination of the following: a feedback pulse level, a feedback pulse length, or a feedback pulse. The number is used to indicate the output voltage; and a power switch current flowing through one of the power switches corresponds to the feedback pulse level, the feedback pulse time length, the number of feedback pulses, or a combination thereof.

In a preferred embodiment, the synchronous rectification pulse signal has a synchronous rectification pulse, and the feedback pulse signal has a feedback pulse; wherein the synchronous rectification pulse and the feedback pulse have a pulse duration shorter than one. Micro-second.

In a preferred embodiment, the feedback pulse signal has a feedback pulse during a period of operation, and the feedback pulse is synchronized by a synchronization rectification pulse generated by the synchronous rectification pulse signal. Produced after the period.

In the foregoing embodiment, after the synchronous rectification pulse of the synchronous rectification pulse signal is generated, the next synchronization rectification pulse is not generated during a synchronization threshold, and the SR switch control circuit generates the feedback pulse, and then The feedback pulse is periodically generated during a feedback cycle until the power switch control circuit generates the synchronous rectification pulse.

In the foregoing embodiments, the synchronization preset period is related to the output voltage.

In a preferred embodiment, during the operation, the synchronous rectification pulse signal has a synchronous rectification pulse, and the synchronous rectification pulse is generated after one feedback pulse of the feedback pulse signal is generated. Generated after the preset period.

In the foregoing embodiment, after the feedback pulse of the feedback pulse signal is generated, the next feedback pulse is not generated during a feedback threshold, and the power switch control circuit generates the synchronous rectification pulse, and then The synchronous rectification pulse is periodically generated in a synchronization cycle until the SR switch control circuit generates the feedback pulse.

In the foregoing embodiment, the feedback preset period is related to the output voltage.

In a preferred embodiment, the SR switch control circuit includes: an output voltage sampling circuit for sampling and amplifying the output voltage to generate an output voltage sampling signal; a feedback pulse signal generating circuit coupled to The output voltage sampling circuit and the secondary side 用以 are configured to generate the feedback pulse signal according to the output voltage sampling signal; an SR comparator coupled to the secondary side , for synchronizing according to the coupling The rectified signal and a synchronous reference signal generate a synchronous comparison signal; an SR timing circuit is coupled to the comparator for generating a synchronous preset period after timing a synchronization preset period according to the synchronous comparison signal And an SR switch control signal generating circuit coupled to the comparator and the SR switch for generating an SR switch control signal to control the SR switch according to the synchronous comparison signal.

The purpose, technical content, features and effects achieved by the present invention will be more readily understood by the detailed description of the embodiments.

100,200‧‧‧Return-type power supply circuit

101‧‧‧Rectifier circuit

102,202‧‧‧Transformers

103‧‧‧Coupling circuit

104‧‧‧Optical coupling circuit

105‧‧‧PWM control circuit

106‧‧‧ Current sensing circuit

107‧‧‧Synchronous rectification control circuit

108‧‧‧Synchronous rectifier switch circuit

204‧‧‧Signal coupling circuit

205‧‧‧Power switch control circuit

207‧‧‧SR switch control circuit

208‧‧‧SR switch

2051‧‧‧Power switch control signal generation circuit

2053‧‧‧Responsive signal sampling and holding circuit

2055‧‧‧Return timing circuit

2071‧‧‧Output voltage sampling circuit

2073‧‧‧Reward pulse signal generation circuit

2075‧‧‧SR comparator

2077‧‧‧SR timing circuit

2079‧‧‧SR switch control signal generation circuit

3051‧‧‧ comparator

3052‧‧‧Latch circuit

3053‧‧‧Sampling and holding circuit

3071‧‧‧voltage circuit

3072‧‧‧ comparator

3074‧‧‧pulse switch

3078‧‧‧Delay timer

3079‧‧‧Slope signal generation circuit

3173‧‧‧Pulse circuit

3174‧‧‧pulse switch

20531‧‧‧Shielding circuit

20533‧‧‧Sampling feedback signal generation circuit

BLKP‧‧‧shading signal

C1, C2‧‧‧ capacitor

CLR‧‧‧Clear signal

COMP‧‧‧sampled feedback signal

FB‧‧‧ feedback signal

GND‧‧‧ Ground potential

Iout‧‧‧Output current

Iw2, Isr‧‧‧ current

P1‧‧‧One side

P2‧‧‧ secondary side

PLS‧‧‧Notification signal

Pul1, Pul2, Pul3, Pul4‧‧‧ feedback pulse

PS1, PS2‧‧‧ pulse switch signal

REF‧‧‧ reference potential

Sfb‧‧‧ feedback pulse signal

SH‧‧‧Sampling signal

Spwm‧‧‧ power switch control signal

Sramp‧‧‧Slope Signal

SRPul‧‧‧Synchronous rectification pulse

SW‧‧‧Power switch

SWb‧‧ switch

Sync‧‧‧Synchronous rectification pulse signal

Sx‧‧‧Synchronous comparison signal

Tb‧‧‧shadow pulse length

Td‧‧‧Synchronized preset period

Tp‧‧‧Reward cycle

Ts‧‧‧Synchronous rectification pulse length

Tt‧‧‧Synchronization threshold period

Vac‧‧‧AC voltage

Vin‧‧‧Input voltage

Vfb‧‧‧ coupled feedback signal

Vfb_cmp‧‧‧review comparison signal

Vfb_ltch‧‧‧Latchback feedback signal

Vfb_sh‧‧‧Sampling and Keeping Signals

Vo, Vopto‧‧‧ voltage

Vout‧‧‧ output voltage

Vosp‧‧‧ output voltage sampling signal

Vsr‧‧‧cross pressure

Vsync‧‧‧coupled synchronous rectification signal

Vth1‧‧‧ synchronous reference signal

Vth3‧‧‧Review reference signal

VSR‧‧‧SR switch control signal

Vw2‧‧‧cross pressure

W1‧‧‧ primary winding

W2‧‧‧ secondary winding

Figure 1 shows a prior art flyback power supply circuit.

Figure 2 shows an embodiment of the flyback power supply circuit 200 of the present invention.

3 is a waveform diagram showing the synchronous rectification pulse signal Sync, the power switch control signal Spwm, the SR switch control signal VSR, and the feedback pulse signal Sfb according to the present invention.

4A-4D are diagrams showing waveforms in several embodiments of the synchronous rectified pulse signal Sync and the feedback pulse signal Sfb of the present invention.

FIG. 5 is a schematic diagram showing the waveforms of the synchronous rectification pulse signal Sync, the power switch control signal Spwm, and the feedback pulse signal Sfb according to an embodiment of the present invention.

Figure 6 shows an embodiment of the SR switch control circuit 207 of the present invention.

Figure 7 shows a more specific embodiment of the SR switch control circuit 207 of the present invention.

Figure 8 shows an embodiment of the power switch control circuit 205 of the present invention.

Fig. 9 shows an embodiment of the feedback signal sampling and holding circuit 2053 of the present invention.

Figure 10 shows a more specific embodiment of the power switch control circuit 205 of the present invention.

Figure 11 is a diagram showing the signal waveforms of the masking signal BLKP and the synchronous rectification pulse signal Sync in the embodiment of Figure 10.

Figure 12 shows a more specific embodiment of the power switch control circuit 205 of the present invention.

Figure 13 shows the synchronous rectification pulse signal Sync, power switch control signal Spwm, SR switch control signal VSR, feedback pulse signal Sfb, voltage Vopto, ramp signal Sramp, sample and hold signal Vfb_sh, sample signal SH, and clear according to the present invention. The waveform diagram of the signal CLR.

The drawings in the present invention are schematic, mainly intended to indicate the coupling relationship between the circuits, and the relationship between the signal waveforms, and the circuit, signal waveform and frequency are not drawn to scale.

Referring to Figure 2, an embodiment of a flyback power supply circuit 200 of the present invention is shown. As shown in FIG. 2, the AC voltage Vac is rectified by the rectifier circuit 101, and an input voltage Vin is generated. The rectifier circuit 101 is, for example, a bridge rectifier circuit. In the flyback power supply circuit 200, the primary side winding W1 of the transformer 202 receives the input voltage Vin. The power switch SW controls the on-time of the primary side winding W1, and an output voltage Vout is generated between the secondary side winding W2 and a ground potential GND. The flyback power supply circuit 200 includes a transformer 202, a power switch SW, a signal coupling circuit 204, a power switch control circuit 205, an SR switch control circuit 207, and a synchronous rectification (SR) switch 208. The power switch SW is coupled to the primary side winding W1 for controlling the conduction time of the primary side winding W1. The power switch control circuit 205 is located on the primary side of the transformer 202 for generating the power switch control signal Spwm according to the coupled feedback signal Vfb to control the power switch SW, and generating synchronization according to the coupled feedback signal Vfb. The rectified pulse signal Sync is related to the power switch control signal Spwm. For example, the synchronous rectification pulse signal Sync has a rectification pulse for before the power switch control signal Spwm turns on the power switch SW. The signal coupling circuit 204 converts and transmits the relevant information to the secondary side of the transformer 202 without turning on the SR switch 208.

A synchronous rectification (SR) switch 208 is coupled to the secondary winding W2 for controlling the conduction time of the secondary winding W2 to correspond to the non-conduction when the primary winding W1 is turned on. The SR switch control circuit 207 is located on the secondary side of the transformer 202 and is coupled to the SR switch 208 for receiving the coupled synchronous rectification signal Vsync in the normal operation mode to control the SR switch 208 and according to the output voltage Vout or the output current Iout. , generating a feedback pulse signal Sfb. For example, the SR switch control circuit 207 controls the SR switch 208 according to the coupled synchronous rectification signal Vsync associated with the synchronous rectification pulse signal Sync, and determines the timing at which the secondary side winding W2 is not turned on, and flows through the secondary side winding W2. The current Iw2, or the voltage across the secondary winding W2, Vw2, or the current Isr flowing through the parasitic diode of the SR switch 208, or the voltage across the voltage of the SR switch 208, determines the timing at which the SR switch 208 is turned on.

The signal coupling circuit 204 is coupled between the SR switch control circuit 207 and the power switch control circuit 205 for sensing the synchronous rectified signal Vsync in a non-contact manner by the synchronous rectified pulse signal Sync, and the feedback pulse signal Sfb Inductively generates a coupled feedback signal Vfb in a non-contact manner. The signal coupling circuit 204 has a primary side P1 and a secondary side P2. The primary side P1 is located on the primary side of the transformer 202, and the secondary side P2 is located on the secondary side of the transformer 202. The primary side 埠P1 receives the synchronous rectified pulse signal Sync and the coupled coupling feedback signal Vfb in different periods that do not overlap each other, and the secondary side 埠P2 respectively generates coupling in the corresponding different periods that do not overlap each other. The synchronous rectification signal Vsync is received and the feedback pulse signal Sfb is received. That is, the signal coupling circuit 204 has a primary side P1 electrically connected to the power switch control circuit 205 and a secondary side P2 electrically connected to the SR switch control circuit 207. More specifically, for example, in the first period, the primary side P1 receives the synchronous rectified pulse signal Sync generated by the power switch control circuit 205, and the signal coupling circuit 204 is in a non-contact manner. After the induction and conversion, the corresponding coupled synchronous rectification signal Vsync is generated on the secondary side 埠P2; in addition, in the second period that does not overlap with the first time period, the secondary side 埠P2 receives the feedback pulse signal Sfb, and the signal coupling The circuit 204 senses and converts in a non-contact manner to generate a corresponding coupled feedback signal Vfb.

It should be noted that the primary side of the transformer 202 is on the same side as the primary side winding W1 of the transformer 202, and the circuit on the primary side of the transformer 202 is electrically connected to the reference potential REF; the secondary side of the transformer 202 is represented on the secondary side of the transformer 202. The circuit W2 is electrically connected to the ground potential GND, and the transformer 202 and the signal coupling circuit 204 are coupled between the primary side and the secondary side.

In the present embodiment, the signal coupling circuit 204 includes only a single pulse transformer as shown. In other embodiments, the signal coupling circuit 204 may also include the same chirp, and at different times, on the primary side of the transformer 202. The secondary side has a function of bidirectionally coupling the transmission signal. For example, the signal coupling circuit 204 includes a pulse optical coupler. In a preferred embodiment, the input and output signals of the pulse transformer and the pulse optocoupler are signals having a pulse form. The feedback pulse signal Sfb and the coupled feedback signal Vfb, for example but not limited to respectively, have the same or different feedback pulses, and the feedback pulse has one of the following or a combination thereof: the feedback pulse level and the feedback pulse time length Or, the number of pulses is returned to indicate the output voltage Vout; and the power switch current flowing through the power switch SW corresponds to the feedback pulse level, the feedback pulse time length, the number of feedback pulses, or a combination thereof. That is to say, the feedback pulse signal Sfb and the coupled feedback signal Vfb have a pulse form signal, but are not limited to the form of a single pulse signal, but can be indicated by the level of the pulse signal, the length of time, and the number of pulses. The level of the output voltage.

In the present embodiment, the SR switch control circuit 207 is, for example but not limited to, according to the coupled synchronous rectification signal Vsync and the current Iw2 flowing through the secondary side winding W2, or the cross voltage Vw2 of the secondary side winding W2, or flowing through the SR. The current Isr of the parasitic diode in the switch 208, or the voltage across the Vsr of the SR switch 208, generates an SR switch control signal VSR to control the SR switch 208. And for example but not limited to coupled synchronous rectification signals The rising edge (or falling edge of the synchronous rectification pulse in Vsync, as shown in Fig. 13), does not turn on the SR switch 208, and according to the current Iw2 flowing through the secondary side winding W2, or the secondary side winding W2 The voltage across the voltage Vw2, or the current Isr flowing through the parasitic diode of the SR switch 208, or the voltage across the voltage of the SR switch 208, Vsr, to confirm that the power switch SW is not conducting, turns on the SR switch 208. That is, the SR switch control circuit 207 confirms that the power switch SW is not turned on before turning on the SR switch 208. The power switch control circuit 205 determines the power switch control signal Spwm based on the coupled feedback signal Vfb, for example, to determine whether the power switch SW is turned on and off, thereby turning on and off the primary side winding W1. Compared with the prior art, in the present invention, the signal coupling circuit 204 has a primary side 埠P1 and a secondary side 埠P2, the primary side 埠P1 is located on the primary side of the transformer 202, and the secondary side 埠P2 is located twice in the transformer 202. a side, wherein the primary side 埠P1 receives the synchronous rectification pulse signal Sync and the coupled coupling feedback signal Vfb in different periods that do not overlap each other, and the secondary side 埠P2 is in the corresponding different periods that do not overlap each other, respectively A coupled synchronous rectification signal Vsync is generated and a feedback feedback signal Sfb is received. Rather than using the different coupling circuit 103 and the optical coupling circuit 104 (and different turns), respectively, the primary side notification signal PLS is transmitted to the secondary side, and the secondary side output voltage related information is transmitted to the secondary side. Primary side PWM controller 105. That is to say, in the normal operation mode, the present invention can transmit the information of the primary side and the secondary side by using the same chirp in the signal coupling circuit 204. In this way, the space of the circuit can be effectively reduced, thereby reducing the manufacturing cost and the size of the circuit.

3 is a waveform diagram showing the synchronous rectification pulse signal Sync, the power switch control signal Spwm, the SR switch control signal VSR, and the feedback pulse signal Sfb according to the present invention. As shown, the power switch control circuit 205 generates a power switch control signal Spwm to control the power switch SW based on the coupled feedback signal Vfb associated with the output voltage Vout or the output current Iout, and generates a synchronous rectified pulse signal Sync. The synchronous rectification pulse signal Sync has a synchronous rectification pulse; in a preferred embodiment, the synchronous rectification pulse is converted by the signal coupling circuit 204 and transmitted to the SR switch circuit 207 to control the SR switch 208 to be non-conducting; and the SR switch The control circuit 207 does not turn on the SR switch 208 in accordance with the coupled synchronous rectification signal Vsync associated with the synchronous rectification pulse. In a preferred embodiment, the power switch control circuit 205 generates a synchronous rectification pulse of the synchronous rectification pulse signal Sync, after the SR switch 208 is not turned on, the level of the power switch control signal Spwm is changed to turn on the power switch SW to confirm that the conduction of the power switch SW is not at the SR switch 208. After the conduction. In a preferred embodiment, the synchronous rectification pulse signal Sync has a synchronous rectification pulse, and the feedback pulse signal Sfb has a feedback pulse; wherein the synchronous rectification pulse and the feedback pulse have a pulse length shorter than 1 micro. Micro-second.

The SR switch control circuit 207 synchronizes the rectified signal Vsync according to the received coupling in a normal operation mode, and is, for example but not limited to, according to the current Iw2 flowing through the secondary winding W2 or the crossover voltage Vw2 of the secondary winding W2. Or, the current Isr flowing through the parasitic diode in the SR switch 208, or the voltage across the voltage Vsr of the SR switch 208, generates the SR switch control signal VSR. In the normal operation mode, the SR switch control circuit 207 generates a feedback pulse signal Sfb according to the feedback signal FB related to the output voltage Vout or the output current Iout.

For example, during an operation period, the feedback pulse signal Sfb includes a feedback pulse generated after a synchronization preset period Td is generated after the synchronous rectification pulse of the synchronous rectification pulse signal Sync is generated. During an operation, for example, but not limited to, the power switch control signal Spwm level rises from the low level to the high level twice. For example, referring to FIG. 3, taking the high-level conduction and the low-level non-conduction as an example, according to the rising edge of the synchronous rectification pulse signal Sync, the SR switch 208 is not turned on, and according to the feedback related to the output voltage Vout or the output current Iout. The signal FB is either according to: a current Iw2 flowing through the secondary winding W2, or a voltage Vw2 of the secondary winding W2, or a current Isr flowing through the parasitic diode of the SR switch 208, or the SR switch 208 The SR switch control signal VSR is generated across the voltage Vsr, and the SR switch 208 is turned on. The current condition of the secondary side winding W2 can be determined, for example, according to the voltage across the SR switch 208 or based on the voltage of the SR switch 208 at the left end node of the figure. For example, before the power switch control signal Spwm rises, the SR switch control signal VSR is changed from the high level to the low level, and the SR switch 208 is not turned on; and according to the current Iw2 flowing through the secondary winding W2, or twice The voltage across the side winding W2, Vw2, or the current Isr flowing through the parasitic diode in the SR switch 208, or the voltage across the SR switch 208, Vsr, and the SR switch The control signal VSR is changed from a low level to a high level, and the SR switch 208 is turned on. With this mechanism, the conduction time point and the non-conduction time point of the SR switch 208 can be appropriately controlled, and the synchronous rectification pulse signal Sync and the feedback pulse signal Sfb are respectively transmitted to the secondary side at different time periods by using the same 埠. On the primary side, when the power switch SW and the SR switch 208 are turned on and off, the short-circuit penetration can be effectively avoided.

4A-4D are diagrams showing waveforms in several embodiments of the synchronous rectified pulse signal Sync and the feedback pulse signal Sfb of the present invention. As shown in FIG. 4A, the synchronous rectification pulse signal Sync and the feedback pulse signal Sfb have, for example but not limited to, a single pulse (SR pulse and feedback pulse, respectively). As shown in FIG. 4B, the synchronous rectification pulse signal Sync and the feedback pulse signal Sfb have, for example but not limited to, a single pulse (SR pulse and feedback pulse respectively), and the level thereof can be adjusted; wherein, the feedback pulse signal Sfb The level of the feedback pulse is, for example, used to indicate the level of the output voltage Vout. As shown in FIG. 4C, the synchronous rectification pulse signal Sync and the feedback pulse signal Sfb have, for example but not limited to, a single pulse (SR pulse and feedback pulse respectively), and the pulse duration can be adjusted; wherein the pulse signal is feedback The length of the feedback pulse of Sfb is, for example, used to indicate the level of the output voltage Vout. As shown in FIG. 4D, the synchronous rectification pulse signal Sync and the feedback pulse signal Sfb have, for example but not limited to, complex pulses (complex SR pulses and complex feedback pulses, respectively), and the number of pulses can be changed; wherein, the feedback pulse The number of feedback pulses of the signal Sfb is, for example, used to indicate the level of the output voltage Vout.

FIG. 5 is a schematic diagram showing the waveforms of the synchronous rectification pulse signal Sync, the power switch control signal Spwm, and the feedback pulse signal Sfb according to an embodiment of the present invention. As shown in the figure, during an operation period, the feedback pulse signal Sfb has a feedback pulse Pul1, and the feedback pulse Pul1 is generated after the synchronization preset period Td is generated after the synchronous rectification pulse SRPul of the synchronous rectification pulse signal Sync is generated. When the synchronous rectification pulse SRPul of the synchronous rectification pulse signal Sync is generated, the next synchronous rectification pulse SRPul is not generated during the synchronization threshold period Tt, and the SR switch control circuit 207 generates the feedback pulse Pul2, and then cycles with a feedback period Tp. The feedback pulse Pul3 and the feedback pulse Pul4 are generated until the power switch control circuit 205 generates a synchronization. The rectification pulse SRPul. In this way, when the output is lightly loaded, the SR switch control circuit 207 can continue to generate a feedback pulse to indicate the output voltage Vout.

Figure 6 shows an embodiment of the SR switch control circuit 207 of the present invention. As shown, the SR switch control circuit 207 includes an output voltage sampling circuit 2071, a feedback pulse signal generating circuit 2073, an SR comparator 2075, an SR timing circuit 2077, and an SR switch control signal generating circuit 2079. The output voltage sampling circuit 2071 is configured to sample the amplified output voltage Vout to generate an output voltage sampling signal Vosp. The feedback pulse signal generating circuit 2073 is coupled between the output voltage sampling circuit 2071 and the secondary side 埠P2 for generating the feedback pulse signal Sfb according to the output voltage sampling signal Vosp. The SR comparator 2075 is coupled to the secondary side P2 for generating a synchronous comparison signal Sx according to the coupled synchronous rectified signal Vsync and the synchronous reference signal Vth1. The SR timing circuit 2077 is coupled to the comparator 2075 for generating a synchronization preset period timing signal after timing the synchronization preset period according to the synchronous comparison signal Sx. The SR switch control signal generating circuit 2079 is coupled to the SR comparator 2075 and the SR switch 208 for generating the SR switch control signal VSR according to the synchronous comparison signal Sx to control the SR switch 208.

Figure 7 shows a more specific embodiment of the SR switch control circuit 207 of the present invention. The SR switch control circuit 207 includes an output voltage sampling circuit 2071, a feedback pulse signal generating circuit 2073, an SR comparator 2075, an SR timing circuit 2077, and an SR switch control signal generating circuit 2079. The output voltage sampling circuit 2071 is configured to sample the amplified output voltage Vout to generate an output voltage sampling signal Vosp. As shown, in the output voltage sampling circuit 2071, the voltage dividing circuit 3071 receives the voltage Vo associated with the output voltage Vout, and generates a divided voltage associated with the output voltage Vout, thereby generating an output voltage sampling signal Vosp. In the present embodiment, the output voltage sampling circuit 2071 includes a comparator 3072 for comparing the voltage Vopto and the ramp signal Sramp related to the output voltage Vout to generate an output voltage sampling signal Vosp. For example, when the ramp signal Sramp exceeds the voltage Vopto, a comparison signal having a high level is generated. The feedback pulse signal generating circuit 2073 is coupled between the output voltage sampling circuit 2071 and the secondary side 埠P2 for generating the feedback pulse signal Sfb according to the output voltage sampling signal Vosp. The feedback pulse signal generating circuit 2073 includes a pulse circuit 3073, which generates a pulse switching signal PS1 according to the comparison signal having a high level. The feedback pulse signal generating circuit 2073 includes a pulse switch 3074 that operates according to the pulse switching signal PS1 to generate a feedback pulse signal Sfb on the secondary side 埠P2.

Continuing to refer to FIG. 7, the SR comparator 2075 is coupled to the secondary side P2 for generating a synchronous comparison signal Sx according to the coupled synchronous rectified signal Vsync and the synchronous reference signal Vth1. The SR timing circuit 2077 is coupled to the SR comparator 2075 for receiving the synchronous comparison signal Sx, and generates a synchronization preset period timing signal after the timing synchronization preset period. The synchronization preset period timing signal is used, for example, to cause the feedback pulse of the feedback pulse signal Sfb to be generated after the synchronization preset period Td is generated after the synchronous rectification pulse of the synchronous rectification pulse signal Sync is generated. In the present embodiment, the SR timing circuit 2077 includes, for example but not limited to, a delay timer 3078 and a ramp signal generating circuit 3079. The delay effect of the timing signal during the synchronization preset period, that is, the synchronization preset period Td, is related to the output voltage Vout. The ramp signal generating circuit 3079 is configured to generate the ramp signal Sramp to input the comparator 3072. The SR switch control signal generating circuit 2079 is coupled to the SR comparator 2075 and the SR switch 208 for generating an SR switch control signal VSR according to the synchronous comparison signal Sx to control the SR switch 208.

Figure 8 shows an embodiment of the power switch control circuit 205 of the present invention. As shown, the power switch control circuit 205 includes a power switch control signal generating circuit 2051, a feedback signal sample and hold circuit 2053, a feedback timing circuit 2055, and an SR pulse signal generating circuit 2057. The power switch control signal generating circuit 2051 is coupled to the power switch SW for generating the power switch control signal Spwm according to the sample feedback signal COMP. The feedback signal sampling and holding circuit 2053 is coupled between the power switch control signal generating circuit 2051 and the primary side switch P1 for generating the sample feedback signal COMP according to the coupled feedback signal Vfb. The feedback timing circuit 2055 is coupled to the power switch control signal generating circuit 2051 and the feedback signal sampling and holding circuit 2053 for generating the sampling signal SH and the clear signal CLR according to the power switch control signal Spwm and the coupled feedback signal Vfb. The feedback signal sampling and holding circuit 2053 converts the coupled feedback signal Vfb into the sample feedback signal COMP according to the sampling signal SH and the clear signal CLR.

Fig. 9 shows an embodiment of the feedback signal sampling and holding circuit 2053 of the present invention. As shown, the feedback signal sampling and holding circuit 2053 includes a masking circuit 20531 and a sample feedback signal generating circuit 20533. The masking circuit 20531 is coupled to the power switch control signal generating circuit 2051 and the primary side switch P1 for shielding the signal BLKP according to one of the power switch control signals Spwm to prevent the feedback signal sample and hold circuit during the masking period. The 2053 receives the synchronous rectification pulse signal Sync from the primary side P1. The sampling feedback signal generating circuit 20533 is coupled between the shielding circuit 20531 and the power switch control signal generating circuit 2051 for generating the sample feedback signal COMP according to the coupled feedback signal Vfb, the clear signal CLR, and the sampling signal SH.

Figure 10 shows a more specific embodiment of the power switch control circuit 205 of the present invention. As shown, the power switch control circuit 205 includes a power switch control signal generating circuit 2051, a feedback signal sample and hold circuit 2053, and a feedback timing circuit 2055. The power switch control signal generating circuit 2051 is coupled to the power switch SW for generating the power switch control signal Spwm according to the sample feedback signal COMP. The pulse signal generating circuit 2057 is coupled to the power switch control signal generating circuit 2051, and generates a synchronous rectified pulse signal according to the power switch control signal Spwm (in the present embodiment, the pulse signal generating circuit 2057 receives the related signal of the power switch control signal Spwm). Sync. The feedback signal sampling and holding circuit 2053 is coupled between the power switch control signal generating circuit 2051 and the primary side switch P1 for generating the sample feedback signal COMP according to the coupled feedback signal Vfb. The feedback timing circuit 2055 is coupled to the power switch control signal generating circuit 2051 and the feedback signal sampling and holding circuit 2053 for coupling with the coupled feedback signal Vfb according to the power switch control signal Spwm (in this embodiment, for example, receiving is related to coupling) The feedback signal Vfb is generated to generate the sampling signal SH and the clear signal CLR. The feedback signal sampling and holding circuit 2053 converts the coupled feedback signal Vfb into the sample feedback signal COMP according to the sampling signal SH and the clear signal CLR. And according to the masking signal BLKP, during the masking period, the feedback signal sampling and holding circuit 2053 is prevented from receiving the synchronous rectification pulse signal Sync from the primary side P1.

Figure 11 is a diagram showing the signal waveforms of the masking signal BLKP and the synchronous rectification pulse signal Sync in the embodiment of Figure 10. As shown in the figure, and referring to FIG. 10, the masking signal BLKP has a masking pulse time length Tb, and the synchronous rectifying pulse signal Sync has a synchronous rectifying pulse time length Ts; wherein the masking pulse time length Tb is greater than the synchronous rectifying pulse time length Ts, and The masking pulse time length Tb covers the synchronous rectification pulse time length Ts; this causes the masking signal BLKP to generate the masking pulse and the switch SWb to be turned on during the synchronous rectification pulse in the synchronous rectification pulse signal Sync, and the feedback signal sampling and holding circuit The inverting input of the comparator (used as the masking circuit 20531) in 2053 is electrically connected to the reference potential REF, so that the inverting input of the comparator (used as the masking circuit 20531) does not receive the synchronous rectified pulse signal. Synchronous rectification pulse in Sync.

Figure 12 shows a more specific embodiment of the power switch control circuit 205 of the present invention. As shown, the power switch control circuit 205 includes a power switch control signal generating circuit 2051, a feedback signal sample and hold circuit 2053, and a feedback timing circuit 2055. The power switch control signal generating circuit 2051 is coupled to the power switch SW for generating the power switch control signal Spwm according to the sample feedback signal COMP. The pulse circuit 3173 is coupled to the power switch control signal generating circuit 2051, and generates a pulse switching signal PS2 according to the power switch control signal Spwm. The pulse switch 3174 is coupled to the pulse circuit 3173, and operates according to the pulse switching signal PS2 to generate the synchronous rectification pulse signal Sync on the primary side P1. The feedback signal sampling and holding circuit 2053 is coupled between the power switch control signal generating circuit 2051 and the primary side switch P1 for generating the sample feedback signal COMP according to the coupled feedback signal Vfb. The feedback timing circuit 2055 is coupled to the power switch control signal generating circuit 2051 and the feedback signal sampling and holding circuit 2053 for controlling the signal Spwm according to the power switch (in the present embodiment, for example, receiving a pulse related to the power switch control signal Spwm) The switching signal PS2) and the coupled feedback signal Vfb (in this embodiment, for example, receiving the feedback comparison signal Vfb_cmp related to the coupled feedback signal Vfb) to generate the sampling signal SH and the clear signal CLR, wherein the feedback signal is sampled and held. The circuit 2053 converts the coupled feedback signal Vfb into a sample feedback signal COMP according to the sampling signal SH and the clear signal CLR.

Referring to FIG. 12, the feedback signal sampling and holding circuit 2053 includes, for example, a comparator 3051, a latch circuit 3052, and a sample and hold circuit 3053. The comparator 3051 compares the coupled feedback signal Vfb with the feedback reference signal Vth3 to generate a feedback comparison signal Vfb_cmp. The latch circuit 3052 generates a latch feedback signal Vfb_ltch according to the feedback comparison signal Vfb_cmp. As shown, the sample hold circuit 3053 generates a sample feedback signal COMP based on the latch feedback signal Vfb_ltch, the sample signal SH, and the clear signal CLR. The switch SW1 is controlled by the latch feedback circuit Vfb_ltch generated by the latch circuit 3052 and coupled to the coupled feedback signal Vfb. The switch SW2 and the switch SW3 are respectively controlled by the sampling signal SH and the clear signal CLR. The capacitor C1 and the capacitor C2 are charged and discharged to generate a sample and hold signal Vfb_sh, thereby generating a sample feedback signal COMP. The feedback timing circuit 2055 is coupled to the power switch control signal generating circuit 2051 and the feedback signal sampling and holding circuit 2053 for controlling the signal Spwm according to the power switch (in this embodiment, for example, receiving a signal related to the power switch control signal Spwm) The pulse switching signal PS2) and the coupled feedback signal Vfb (in this embodiment, for example, receiving a signal feedback comparison signal Vfb_cmp related to the coupled feedback signal Vfb) to generate the sampling signal SH and the clear signal CLR.

Figure 13 shows the synchronous rectification pulse signal Sync, power switch control signal Spwm, SR switch control signal VSR, feedback pulse signal Sfb, voltage Vopto, ramp signal Sramp, sample and hold signal Vfb_sh, sample signal SH, and clear according to the present invention. The waveform diagram of the signal CLR. As shown, the power switch control circuit 205 generates a power switch control signal Spwm to control the power switch SW based on the coupled feedback signal Vfb associated with the output voltage Vout or the output current Iout, and generates a synchronous rectified pulse signal Sync. The synchronous rectification pulse signal Sync has a synchronous rectification pulse; in a preferred embodiment, the synchronous rectification pulse is converted by the signal coupling circuit 204 and transmitted to the SR switch circuit 207 to control the SR switch 208 to be non-conducting; and the SR switch The control circuit 207 does not turn on the SR switch 208 in accordance with the coupled synchronous rectification signal Vsync associated with the synchronous rectification pulse. In a preferred embodiment, the power switch control circuit 205 generates a synchronous rectification pulse of the synchronous rectification pulse signal Sync to change the level of the power switch control signal Spwm after the SR switch 208 is not turned on to turn on the power switch SW. To confirm the power switch SW The conduction is after the SR switch 208 is not turned on. In a preferred embodiment, the synchronous rectification pulse signal Sync has a synchronous rectification pulse, and the feedback pulse signal Sfb has a feedback pulse; wherein the synchronous rectification pulse and the feedback pulse have a pulse length shorter than 1 micro. Micro-second.

It should be noted that, in this embodiment, during the operation period, the feedback pulse signal Sfb includes a feedback pulse, which is generated after the synchronization preset period Td is generated after the synchronous rectification pulse of the synchronous rectification pulse signal Sync is generated. . The voltage preset time period Td is determined by the voltage Vopto and the ramp signal Sramp plus the pulse length time of the clear signal CLR, so that the synchronization preset period Td is related to the output voltage Vout.

The present invention has been described with reference to the preferred embodiments thereof, and the present invention is not intended to limit the scope of the present invention. In the same spirit of the invention, various equivalent changes can be conceived by those skilled in the art. For example, in the embodiments, the two circuits or components that are directly connected may be interposed with other circuits or components that do not affect the main function. Therefore, "coupling" should be considered as including direct and indirect connections. For another example, the resistor or the voltage dividing circuit is not limited to the resistor element, and may be replaced by other circuits such as a transistor circuit. For another example, the positive and negative terminals of the error amplifier circuit and the comparator circuit can be interchanged, and only need to modify the meaning of the relevant circuit or the level of the signal; and, for example, the signal outside the control circuit (such as but not limited to the feedback signal) When processing or calculation is performed inside the take-in control circuit, voltage-current conversion, current-voltage conversion, proportional conversion, etc. may be performed. Therefore, the term "processing or calculation according to a signal" is not limited to the signal according to the present invention. It is also included, if necessary, after the signal is converted as described above, and processed or calculated according to the converted signal. For another example, variations in all of the embodiments may be employed interchangeably, such as the pulse switch 3074 in the embodiment of FIG. 7, and may also be applied to the embodiment of FIG. 10, and the like. All such modifications may be made in accordance with the teachings of the present invention, and the scope of the present invention should be construed to cover the above and other equivalents.

Claims (43)

  1. A flyback power supply circuit includes: a transformer having a primary winding to receive an input voltage; and a secondary winding to generate an output voltage and an output current; a power switch coupled to the primary side a winding for controlling the on-time of the primary winding; a power switch control circuit is located on the primary side of the transformer for generating a power switch control signal to control the power switch according to a coupled feedback signal, and generating a a synchronous rectification pulse signal; a synchronous rectification (SR) switch coupled to the secondary side winding for controlling an on-time of the secondary winding to be turned on when the primary winding is not conducting; The SR switch control circuit is disposed on the secondary side of the transformer and coupled to the SR switch for receiving a coupled synchronous rectification signal in a normal operation mode to control the SR switch, and according to the output voltage or the output a current generating a feedback pulse signal; and a signal coupling circuit coupled to the SR switch control circuit and the power switch control circuit Between the synchronous rectification pulse signal, the coupled synchronous rectification signal is induced in a non-contact manner, and the feedback pulse signal is induced in a non-contact manner to generate the coupled feedback signal; wherein the signal is coupled The circuit has a primary side 埠 and a secondary side 埠, the primary side 埠 is located on the primary side of the transformer, and the secondary side 埠 is located on the secondary side of the transformer, wherein the primary side 埠 is different from each other Receiving the synchronous rectification pulse signal and generating the coupling feedback signal respectively, and the secondary side respectively generates the coupled synchronous rectification signal and receiving the feedback pulse in different time periods corresponding to different periods that do not overlap each other Signal.
  2. The flyback power supply circuit of claim 1, wherein the signal coupling circuit comprises a pulse transformer or a pulse optical coupler, and the input and output signals of the pulse transformer and the pulse optical coupler are pulsed. Formal signal.
  3. The flyback power supply circuit of claim 1, wherein the synchronous rectification pulse signal has a synchronous rectification pulse before the power switch is turned on during an operation period; and the SR switch control circuit is related to The coupled synchronous rectification signal of the synchronous rectification pulse does not turn on the SR switch, so that the SR switch does not conduct before the power switch is turned on.
  4. The flyback power supply circuit of claim 1, wherein the SR switch control circuit is in accordance with a flow through the secondary winding before being turned on by the SR switch control circuit during an operation period. The side winding current, the SR switch current flowing through one of the SR switches, or the crossover voltage of the secondary winding or the SR switch to confirm that the power switch is not conducting.
  5. The flyback power supply circuit of claim 1, wherein the feedback pulse signal comprises at least one feedback pulse, which has one or a combination of the following: a feedback pulse level, a feedback pulse a length of time, or a number of feedback pulses, for indicating the output voltage; and flowing through a power switch current of the power switch, corresponding to the feedback pulse level, the length of the feedback pulse, the feedback pulse Number, or a combination thereof.
  6. The flyback power supply circuit of claim 1, wherein the synchronous rectification pulse signal has a synchronous rectification pulse, and the feedback pulse signal has a feedback pulse; wherein the synchronous rectification pulse and the feedback pulse The pulse duration is shorter than 1 microsecond.
  7. The flyback power supply circuit of claim 1, wherein the feedback pulse signal has a feedback pulse, and the feedback pulse is a synchronous rectification pulse of the synchronous rectification pulse signal. Generated after a synchronization preset period has elapsed.
  8. The flyback power supply circuit of claim 7 is started after the synchronous rectification pulse of the synchronous rectification pulse signal is generated, and the next one is not generated during a synchronization threshold period. The synchronous rectification pulse, the SR switch control circuit generates the feedback pulse, and then periodically generates the feedback pulse in a feedback cycle until the power switch control circuit generates the synchronous rectification pulse.
  9. The flyback power supply circuit of claim 7, wherein the synchronization preset period is related to the output voltage.
  10. The flyback power supply circuit of claim 1, wherein the synchronous rectification pulse signal has a synchronous rectification pulse generated by one of the feedback pulse signals during an operation period. The pulse is generated after a predetermined period of feedback.
  11. The flyback power supply circuit of claim 10, when the feedback pulse of the feedback pulse signal is generated, does not generate the next feedback pulse during a feedback threshold, the power switch The control circuit generates the synchronous rectification pulse and then periodically generates the synchronous rectification pulse in a synchronization cycle until the SR switch control circuit generates the feedback pulse.
  12. The flyback power supply circuit of claim 10, wherein the feedback preset period is related to the output voltage.
  13. The flyback power supply circuit of claim 1, wherein the SR switch control circuit comprises: an output voltage sampling circuit for sampling and amplifying the output voltage to generate an output voltage sampling signal; a pulse signal generating circuit coupled between the output voltage sampling circuit and the secondary side , for generating the feedback pulse signal according to the output voltage sampling signal; an SR comparator coupled to the secondary side Connected to generate a synchronous comparison signal according to the coupled synchronous rectification signal and a synchronous reference signal; an SR timing circuit coupled to the SR comparator for timing a synchronization preset period according to the synchronous comparison signal Thereafter, generating a synchronization preset period timing signal; An SR switch control signal generating circuit is coupled to the SR comparator and the SR switch for generating an SR switch control signal to control the SR switch according to the synchronous comparison signal.
  14. The flyback power supply circuit of claim 1, wherein the power switch control circuit comprises: a power switch control signal generating circuit coupled to the power switch for detecting a signal according to a sample Generating the power switch control signal; a feedback signal hold circuit coupled between the power switch control signal generating circuit and the primary side switch for generating the sample feedback signal according to the coupled feedback signal; a feedback timing circuit coupled to the power switch control signal generating circuit and the feedback signal sample and hold circuit for generating a sample signal and a clear signal according to the power switch control signal and the coupled feedback signal The feedback signal sampling and holding circuit converts the coupled feedback signal into the sample feedback signal according to the sampling signal and the clear signal.
  15. The flyback power supply circuit of claim 14, wherein the feedback signal sampling and holding circuit comprises: a shielding circuit coupled to the power switch control signal generating circuit and the primary side s Correlating with one of the power switch control signals to prevent the feedback signal sampling and holding circuit from receiving the synchronous rectification pulse signal from the primary side during an occlusion period; and a sample feedback signal generation circuit coupled The sampling feedback signal is generated between the shielding circuit and the power switch control signal generating circuit according to the coupled feedback signal, the clear signal, and the sampling signal.
  16. An SR switch control circuit for a flyback power supply circuit, the flyback power supply circuit comprising a transformer having a primary winding for receiving an input voltage; and a secondary winding for generating an output voltage and an output current a power switch coupled to the primary side winding for controlling an on-time of the primary side winding; a power switch control circuit located at a primary side of the transformer For generating a power switch control signal according to a coupled feedback signal to control the power switch, and generating a synchronous rectification pulse signal; a synchronous rectification (SR) switch coupled to the secondary side winding, The on-time of the secondary winding is controlled to be turned on when the primary winding is not conducting; the SR switch control circuit is located on the secondary side of the transformer and coupled to the SR switch for normal operation. In the mode, a coupled synchronous rectification signal is received to control the SR switch, and a feedback pulse signal is generated according to the output voltage or the output current; and a signal coupling circuit coupled to the SR switch control circuit and the power Between the switch control circuits, the synchronous rectification pulse signal is inductively generated in a non-contact manner to generate the coupled synchronous rectification signal, and the feedback pulse signal is induced to generate the coupled feedback signal in a non-contact manner; The signal coupling circuit has a primary side turn and a secondary side turn, the primary side turn is located on the primary side of the transformer, and the secondary side clamp a secondary side of the transformer, wherein the primary side is in different periods of time that do not overlap each other, respectively receiving the synchronous rectified pulse signal and generating the coupled feedback signal, and the secondary side is different from each other During the period of time, the coupled synchronous rectification signal is generated and the feedback pulse signal is received; the SR switch control circuit includes: an output voltage sampling circuit for sampling and amplifying the output voltage to generate an output voltage sampling signal; The feedback pulse signal generating circuit is coupled between the output voltage sampling circuit and the secondary side , for generating the feedback pulse signal according to the output voltage sampling signal; an SR comparator, and the secondary side The 埠 is coupled to generate a synchronous comparison signal according to the coupled synchronous rectification signal and a synchronous reference signal; an SR timing circuit coupled to the SR comparator for timing a synchronization pre-control according to the synchronous comparison signal After the period is set, a synchronization preset period timing signal is generated; and an SR switch control signal generating circuit is coupled to the SR comparator and the SR switch for According to the synchronous signal comparison, generating a switch control signal SR, the SR to control the switch.
  17. The SR switch control circuit of the flyback power supply circuit of claim 16, wherein the signal coupling circuit comprises a pulse transformer or a pulse optical coupler, and the input and output of the pulse transformer and the pulse optical coupler The signals are all signals with a pulse form.
  18. The SR switch control circuit of the flyback power supply circuit of claim 16 is characterized in that, during an operation period, the synchronous rectification pulse signal has a synchronous rectification pulse before the power switch is turned on; and the SR switch The control circuit does not turn on the SR switch according to the coupled synchronous rectification signal associated with the synchronous rectification pulse, so that the SR switch does not conduct until the power switch is turned on.
  19. The SR switch control circuit of the flyback power supply circuit of claim 16, wherein in an operation period, the SR switch control circuit flows through the secondary side before being turned on before the SR switch is turned on. One of the secondary winding currents of the winding, the SR switching current flowing through one of the SR switches, or the crossover voltage of the secondary winding or the SR switch to confirm that the power switch is not conducting.
  20. The SR switch control circuit of the flyback power supply circuit of claim 16, wherein the feedback pulse signal comprises at least one feedback pulse, which has one or a combination of the following: a feedback pulse level a feedback pulse length, or a number of feedback pulses, for indicating the output voltage; and flowing through a power switch current of the power switch, corresponding to the feedback pulse level, the length of the feedback pulse The number of feedback pulses, or a combination thereof
  21. The SR switch control circuit of the flyback power supply circuit of claim 16, wherein the synchronous rectification pulse signal has a synchronous rectification pulse, and the feedback pulse signal has a feedback pulse; wherein the synchronous rectification Both pulse and feedback pulses have a pulse length that is less than one micro-second.
  22. The SR switch control circuit of the flyback power supply circuit of claim 16 is characterized in that, during an operation period, the feedback pulse signal has a feedback pulse, and the feedback is The pulse is generated after a synchronous preset period is generated after one of the synchronous rectified pulse signals is generated.
  23. The SR switch control circuit of the flyback power supply circuit of claim 22, when the synchronous rectification pulse of the synchronous rectification pulse signal is generated, does not generate the next synchronous rectification pulse during a synchronization threshold period. The SR switch control circuit generates the feedback pulse and then periodically generates the feedback pulse in a feedback cycle until the power switch control circuit generates the synchronous rectification pulse.
  24. The SR switch control circuit of the flyback power supply circuit of claim 22, wherein the synchronization preset period is related to the output voltage.
  25. The SR switch control circuit of the flyback power supply circuit of claim 16 is characterized in that, during an operation period, the synchronous rectification pulse signal has a synchronous rectification pulse, and the synchronous rectification pulse is generated from the feedback pulse. One of the signals is generated after the feedback pulse is generated after a feedback period.
  26. The SR switch control circuit of the flyback power supply circuit of claim 25, when the feedback pulse of the feedback pulse signal is generated, does not generate the next feedback during a feedback threshold period. The pulse, the power switch control circuit generates the synchronous rectification pulse, and then periodically generates the synchronous rectification pulse in a synchronization cycle until the SR switch control circuit generates the feedback pulse.
  27. The SR switch control circuit of the flyback power supply circuit of claim 25, wherein the feedback preset period is related to the output voltage.
  28. The SR switch control circuit of the flyback power supply circuit of claim 16, wherein the power switch control circuit comprises: a power switch control signal generating circuit coupled to the power switch for sampling according to a power switch Retrieving a signal to generate the power switch control signal; a feedback signal holding circuit coupled between the power switch control signal generating circuit and the primary side, for generating the sample feedback signal according to the coupled feedback signal; and a feedback timing circuit, and The power switch control signal generating circuit and the feedback signal sample and hold circuit are coupled to generate a sample signal and a clear signal according to the power switch control signal and the coupled feedback signal, wherein the feedback signal is sampled and held. The circuit converts the coupled feedback signal to the sampled feedback signal according to the sampled signal and the clear signal.
  29. The SR switch control circuit of the flyback power supply circuit of claim 28, wherein the feedback signal sampling and holding circuit comprises: a shielding circuit, and the power switch control signal generating circuit and the primary side coupling Connected to block the signal according to one of the power switch control signals to prevent the feedback signal sample and hold circuit from receiving the synchronous rectification pulse signal from the primary side during an occlusion period; and a sample feedback signal The generating circuit is coupled between the shielding circuit and the power switch control signal generating circuit for generating the sample feedback signal according to the coupled feedback signal, the clear signal, and the sampling signal.
  30. A power switch control circuit for a flyback power supply circuit, the flyback power supply circuit comprising a transformer having a primary winding for receiving an input voltage; and a secondary winding for generating an output voltage and an output current a power switch coupled to the primary side winding for controlling an on-time of the primary winding; the power switch control circuit is located on a primary side of the transformer for generating a power switch according to a coupled feedback signal Controlling the signal to control the power switch and generating a synchronous rectification pulse signal; a synchronous rectification (SR) switch coupled to the secondary side winding for controlling the on-time of the secondary winding to correspond Turning on when the primary side winding is not conducting; an SR switch control circuit, located on the secondary side of the transformer, coupled to the SR switch, for receiving a coupled synchronous rectification signal in a normal operation mode to control the a SR switch, and generating a feedback pulse signal according to the output voltage or the output current; and a signal coupling circuit coupled Between the SR switch control circuit and the power switch control circuit, the synchronous rectification pulse signal is inductively generated in a non-contact manner to generate the coupled synchronous rectification signal, and the feedback pulse signal is in a non-contact manner. Inductively generating the coupled feedback signal; wherein the signal coupling circuit has a primary side turn and a secondary side turn, the primary side turn is located on a primary side of the transformer, and the secondary side turn is located on a secondary side of the transformer And the primary side is respectively received in the different time periods that do not overlap each other, respectively receiving the synchronous rectified pulse signal and generating the coupled feedback signal, and the secondary side is in a period of time corresponding to different periods that do not overlap each other, respectively Generating the coupled synchronous rectification signal and receiving the feedback pulse signal; the power switch control circuit includes: a power switch control signal generating circuit coupled to the power switch for generating the power switch according to a sample feedback signal a control signal; a feedback signal sampling and holding circuit coupled between the power switch control signal generating circuit and the primary side Coupling the feedback signal to generate the sample feedback signal; and a feedback timing circuit coupled to the power switch control signal generating circuit and the feedback signal sampling and holding circuit for controlling the signal and the coupling according to the power switch The signal is sent to generate a sample signal and a clear signal, wherein the feedback signal sample and hold circuit converts the coupled feedback signal into the sample feedback signal according to the sample signal and the clear signal.
  31. The power switch control circuit of the flyback power supply circuit of claim 30, wherein the feedback signal sampling and holding circuit comprises: a shielding circuit coupled to the power switch control signal generating circuit and the primary side And for shielding the signal according to one of the power switch control signals to prevent the feedback signal sampling and holding circuit from receiving the synchronous rectification pulse signal from the primary side during an occlusion period; and generating a sampled feedback signal The circuit is coupled between the shielding circuit and the power switch control signal generating circuit for generating the sample feedback signal according to the coupled feedback signal, the clear signal, and the sample signal.
  32. The power switch control circuit of the flyback power supply circuit of claim 30, wherein the signal coupling circuit comprises a pulse transformer or a pulse optical coupler, and the input and output signals of the pulse transformer and the pulse optical coupler They are all signals with a pulse form.
  33. The power switch control circuit of the flyback power supply circuit of claim 30, in an operation period, before the power switch is turned on, the synchronous rectification pulse signal has a synchronous rectification pulse, and the SR switch control circuit According to the coupled synchronous rectification signal related to the synchronous rectification pulse, the SR switch is not turned on, so that the SR switch is not turned on before the power switch is turned on.
  34. The power switch control circuit of the flyback power supply circuit of claim 30, wherein the SR switch control circuit flows through the secondary winding before being turned on during an operation period. One of the secondary side winding currents, one of the SR switch currents flowing through the SR switch, or the crossover voltage of the secondary side winding or the SR switch to confirm that the power switch is not conducting.
  35. The power switch control circuit of the flyback power supply circuit of claim 30, wherein the feedback pulse signal comprises at least one feedback pulse, which has one or a combination of the following: a feedback pulse level, a feedback pulse length, or a number of feedback pulses, for indicating the output voltage; and flowing through a power switch current of the power switch, corresponding to the feedback pulse level, the length of the feedback pulse, The number of feedback pulses, or a combination thereof.
  36. The power switch control circuit of the flyback power supply circuit of claim 30, wherein the synchronous rectification pulse signal has a synchronous rectification pulse, and the feedback pulse signal has a feedback pulse; wherein the synchronous rectification pulse The pulse duration with the feedback pulse is shorter than 1 microsecond.
  37. The power switch control circuit of the flyback power supply circuit of claim 30, wherein the feedback pulse signal has a feedback pulse during an operation period, and the feedback The pulse is generated after a synchronous preset period is generated after one of the synchronous rectified pulse signals is generated.
  38. The power switch control circuit of the flyback power supply circuit of claim 37, when the synchronous rectification pulse of the synchronous rectification pulse signal is generated, does not generate the next synchronous rectification pulse during a synchronization threshold period, The SR switch control circuit generates the feedback pulse and then periodically generates the feedback pulse in a feedback cycle until the power switch control circuit generates the synchronous rectification pulse.
  39. The power switch control circuit of the flyback power supply circuit of claim 37, wherein the synchronization preset period is related to the output voltage.
  40. The power switch control circuit of the flyback power supply circuit of claim 30, wherein the synchronous rectification pulse signal has a synchronous rectification pulse, and the synchronous rectification pulse is generated by the feedback pulse signal during an operation period. One of the feedback pulses is generated after a feedback period.
  41. The power switch control circuit of the flyback power supply circuit of claim 40, when the feedback pulse of the feedback pulse signal is generated, does not generate the next feedback pulse during a feedback threshold period. The power switch control circuit generates the synchronous rectification pulse, and then periodically generates the synchronous rectification pulse in a synchronization cycle until the SR switch control circuit generates the feedback pulse.
  42. The power switch control circuit of the flyback power supply circuit of claim 40, wherein the feedback preset period is related to the output voltage.
  43. The power switch control circuit of the flyback power supply circuit of claim 30, wherein the SR switch control circuit comprises: an output voltage sampling circuit for sampling and amplifying the output voltage to generate an output voltage sampling signal ; a feedback pulse generating circuit is coupled between the output voltage sampling circuit and the secondary side, for generating the feedback pulse signal according to the output voltage sampling signal; an SR comparator, and the second The side 埠 is coupled to generate a synchronous comparison signal according to the coupled synchronous rectification signal and a synchronous reference signal; an SR timing circuit coupled to the SR comparator for timing synchronization according to the synchronous comparison signal After the preset period, a synchronous preset period timing signal is generated; and an SR switch control signal generating circuit is coupled to the SR comparator and the SR switch for generating an SR switch control signal according to the synchronous comparison signal. To control the SR switch.
TW106125968A 2016-11-14 2017-08-01 Flyback power converter and synchronous rectification (sr) switch control circuit and power switch control circuit thereof TWI635699B (en)

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