阅读说明：本技术 应用于电源转换器的二次侧的次级控制器及其操作方法 (Secondary controller applied to secondary side of power converter and operation method thereof ) 是由 李弘庆 林崇伟 吴宗谦 吴柏毅 于 2019-10-09 设计创作，主要内容包括：本发明公开了一种应用于电源转换器的二次侧的次级控制器及其操作方法。所述次级控制器包含一控制信号产生电路。所述控制信号产生电路耦接于所述电源转换器的二次侧的输出端,用于检测所述二次侧的输出电压,并启用一脉冲信号至所述电源转换器的二次侧的一信号源,其中所述信号源根据所述脉冲信号启用一开启信号。所述开启信号通过所述电源转换器的二次侧辅助绕组耦合至所述电源转换器的一次侧辅助绕组使所述一次侧辅助绕组产生一电压,且所述电源转换器的一次侧的初级控制器根据所述电压使所述电源转换器的一次侧开启。因此,本发明所公开的电源转换器具有较低的成本且对所述输出电压的变化具有较快的动态响应。(The invention discloses a secondary controller applied to a secondary side of a power converter and an operation method thereof. The secondary controller includes a control signal generating circuit. The control signal generating circuit is coupled to an output end of the secondary side of the power converter, and is used for detecting an output voltage of the secondary side and enabling a pulse signal to a signal source of the secondary side of the power converter, wherein the signal source enables a starting signal according to the pulse signal. The turn-on signal is coupled to a primary side auxiliary winding of the power converter through a secondary side auxiliary winding of the power converter to enable the primary side auxiliary winding to generate a voltage, and a primary controller of a primary side of the power converter enables the primary side of the power converter to be turned on according to the voltage. Therefore, the power converter disclosed by the invention has lower cost and faster dynamic response to the change of the output voltage.)

1. A secondary controller for use on a secondary side of a power converter, comprising:

the control signal generating circuit is coupled with the output end of the secondary side of the power converter and used for detecting the output voltage of the secondary side and starting a pulse signal to a signal source of the secondary side of the power converter, wherein the signal source starts a starting signal according to the pulse signal;

the turn-on signal is coupled to a primary side auxiliary winding of the power converter through a secondary side auxiliary winding of the power converter to enable the primary side auxiliary winding to generate a voltage, and a primary controller of a primary side of the power converter enables the primary side of the power converter to be turned on according to the voltage.

2. The secondary controller of claim 1, wherein: the power converter is a flyback power converter.

3. The secondary controller of claim 1, wherein: the control signal generating circuit starts a short-circuit control signal to at least one short-circuit winding switch after the discharge time of the secondary side of the power converter so as to enable the at least one short-circuit winding switch to be switched on; when the output voltage is smaller than an output target voltage, the control signal generating circuit enables the pulse signal to the signal source and closes the short-circuit control signal.

4. The secondary controller of claim 3, wherein: the at least one short-circuit winding switch is coupled to the secondary side auxiliary winding.

5. The secondary controller of claim 3, wherein: the power converter is in a discontinuous conduction mode.

6. The secondary controller of claim 3, wherein: there is a predetermined time between the discharge time and the short circuit control signal.

7. The secondary controller of claim 1, wherein: when the discharge time of the secondary side of the power converter is greater than a minimum closing time and the output voltage is less than an output target voltage, the control signal generating circuit enables the pulse signal to the signal source.

8. The secondary controller of claim 7, wherein: the power converter is in a continuous conduction mode.

9. The secondary controller of claim 3 or 7, wherein: the primary controller turns off the primary side of the power converter when a detection voltage of the primary side of the power converter is greater than a detection target voltage during a primary side turn-on period of the power converter.

10. The secondary controller of claim 1, wherein: the signal source is a voltage source or a current source.

11. An operating method of a secondary controller applied to a secondary side of a power converter, the secondary controller comprising a control signal generating circuit, wherein the operating method comprises:

when the output voltage of the secondary side of the power converter is smaller than an output target voltage, the control signal generating circuit enables a pulse signal to a signal source of the secondary side of the power converter and closes a short-circuit control signal, wherein the signal source enables a starting signal according to the pulse signal, the starting signal is coupled to the primary side auxiliary winding of the power converter through the secondary side auxiliary winding of the power converter to enable the primary side auxiliary winding to generate a voltage, and the primary side controller of the primary side of the power converter enables the primary side of the power converter to be started according to the voltage;

the primary controller turns off the primary side of the power converter when a detection voltage of the primary side of the power converter is greater than a detection target voltage during the primary side turn-on period of the power converter; and

the control signal generating circuit enables a short-circuit control signal to at least one short-circuit winding switch after the discharge time of the secondary side of the power converter so as to enable the at least one short-circuit winding switch to be turned on.

12. The method of operation of claim 11, wherein: and after the at least one short-circuit winding switch is switched on, when the output voltage is smaller than the output target voltage again, the control signal generating circuit enables the pulse signal to the signal source again and switches off the short-circuit control signal again.

13. The secondary controller of claim 11, wherein: there is a predetermined time between the discharge time and the short circuit control signal.

14. An operating method of a secondary controller applied to a secondary side of a power converter, the secondary controller comprising a control signal generating circuit, wherein the operating method comprises:

when the discharge time of the secondary side of the power converter is greater than a minimum closing time and the output voltage of the secondary side of the power converter is less than an output target voltage, the control signal generating circuit enables a pulse signal to a signal source of the secondary side of the power converter, wherein the signal source enables a starting signal according to the pulse signal, the starting signal is coupled to the primary side auxiliary winding of the power converter through the secondary side auxiliary winding of the power converter to enable the primary side auxiliary winding to generate a voltage, and a primary controller of the primary side of the power converter enables the primary side of the power converter to be opened according to the voltage; and

the primary controller turns off the primary side of the power converter when a detection voltage of the primary side of the power converter is greater than a detection target voltage during a primary side turn-on period of the power converter.

15. The method of operation of claim 14, wherein: after the primary side of the power converter is turned off, when the discharge time is greater than the minimum turn-off time again and the output voltage is less than the output target voltage again, the control signal generation circuit enables the pulse signal to the signal source again.

Technical Field

The present invention relates to a secondary controller applied to a secondary side of a power converter and an operating method thereof, and more particularly, to a secondary controller and an operating method thereof, which can control turn-on of the power converter using a secondary side auxiliary winding and a turn-on signal when the power converter is in a Discontinuous Conduction Mode (DCM) and a quasi-resonant mode (quasi-resonant mode) or in a Continuous Conduction Mode (CCM).

Background

In the prior art, a designer of a power converter may control the power converter to be turned on and off by using a primary controller applied to a primary side of the power converter or by using a secondary controller applied to a secondary side of the power converter. The primary controller detects the change of the output voltage of the secondary side of the power converter by using an auxiliary winding of the primary side of the power converter so as to control the on and off of the power converter. The secondary controller directly detects the change of the output voltage of the secondary side of the power converter and transmits the change of the output voltage to the primary controller through a feedback path formed by the optical coupler and the secondary side synchronous rectification switch so as to control the on and off of the power converter. Because the primary controller detects the output voltage in an indirect manner (the auxiliary winding detects the output voltage), the primary controller cannot accurately control the power converter to turn on or off compared to the secondary controller. However, since the secondary controller controls the power converter to be turned on and off through the secondary side synchronous rectification switch, the power converter can only operate in a Discontinuous Conduction Mode (DCM). However, when the power converter controls the on and off of the power converter by using the secondary controller, since the power converter has to turn on the primary side of the power converter through the conduction of the secondary synchronous rectification switch and the auxiliary winding, the secondary synchronous rectification switch is a necessary component for the secondary side of the power converter, resulting in a limitation on the architecture of the power converter. Therefore, none of the solutions disclosed in the above prior art is a good choice for the designer of the power converter.

Disclosure of Invention

An embodiment of the invention discloses a secondary controller applied to a secondary side of a power converter. The secondary controller includes a control signal generating circuit. The control signal generating circuit is coupled to an output end of the secondary side of the power converter and used for detecting output voltage of the secondary side and enabling a pulse signal to a signal source of the secondary side of the power converter, wherein the signal source enables a starting signal according to the pulse signal; the turn-on signal is coupled to a primary side auxiliary winding of the power converter through a secondary side auxiliary winding of the power converter to enable the primary side auxiliary winding to generate a voltage, and a primary controller of a primary side of the power converter enables the primary side of the power converter to be turned on according to the voltage.

Another embodiment of the present invention discloses an operating method of a secondary controller applied to a secondary side of a power converter, wherein the secondary controller includes a control signal generating circuit, and the operating method includes when an output voltage of a secondary side of the power converter is less than an output target voltage, the control signal generating circuit enables a pulse signal to a signal source on the secondary side of the power converter and closes a short-circuit control signal, wherein the signal source enables a turn-on signal according to the pulse signal, the turn-on signal is coupled to a primary side auxiliary winding of the power converter through a secondary side auxiliary winding of the power converter to enable the primary side auxiliary winding to generate a voltage, the primary side of the power converter is turned on by the primary controller of the primary side of the power converter according to the voltage; the primary controller turns off the primary side of the power converter when a detection voltage of the primary side of the power converter is greater than a detection target voltage during the primary side turn-on period of the power converter; and the control signal generating circuit starts a short-circuit control signal to the at least one short-circuit winding switch after the discharge time of the secondary side of the power converter so as to enable the at least one short-circuit winding switch to be switched on.

Another embodiment of the present invention discloses an operating method of a secondary controller applied to a secondary side of a power converter, wherein the secondary controller comprises a control signal generating circuit, and the operating method comprises when a discharge time of the secondary side of the power converter is greater than a minimum off-time and an output voltage of the secondary side of the power converter is less than an output target voltage, the control signal generating circuit enables a pulse signal to a signal source on the secondary side of the power converter, wherein the signal source enables a turn-on signal according to the pulse signal, the turn-on signal is coupled to a primary side auxiliary winding of the power converter through a secondary side auxiliary winding of the power converter to enable the primary side auxiliary winding to generate a voltage, the primary side of the power converter is turned on by the primary controller of the primary side of the power converter according to the voltage; and when the detection voltage of the primary side of the power converter is larger than a detection target voltage during the primary side opening period of the power converter, the primary controller closes the primary side of the power converter.

The invention discloses a secondary controller applied to a secondary side of a power converter and an operation method thereof. The secondary controller and the operation method are used for coupling a starting signal enabled by a signal source on the secondary side of the power converter to a primary side auxiliary winding of the power converter by using the secondary side auxiliary winding of the power converter so as to enable a primary controller on the primary side of the power converter to start the power converter according to the voltage change of the primary side auxiliary winding. Therefore, compared with the prior art, the secondary controller disclosed by the invention does not need to control the on/off of the power converter through a feedback path formed by an optical coupler and a secondary side synchronous rectification switch, so that the power converter disclosed by the invention has lower cost and has quicker dynamic response to the change of the output voltage. In addition, since the secondary controller can control the turn-on of the power converter through the secondary side auxiliary winding and the turn-on signal, the power converter can operate not only in a discontinuous conduction mode (or a quasi-resonant mode) but also in a continuous conduction mode.

Drawings

Fig. 1 is a schematic diagram of a secondary controller applied to a secondary side of a power converter according to a first embodiment of the present invention.

Fig. 2 is a schematic diagram illustrating the output voltage on the secondary side of the power converter, the secondary-side current, the turn-on signal, the short-circuit control signal, and the voltage on the secondary-side auxiliary winding when the power converter is in the discontinuous conduction mode.

Fig. 3 is a schematic diagram illustrating the output voltage on the secondary side of the power converter, the secondary-side current, the turn-on signal, the short-circuit control signal, and the voltage on the secondary-side auxiliary winding when the power converter is in the continuous conduction mode.

Fig. 4 is a flowchart of an operation method of a secondary controller applied to a secondary side of a power converter according to a second embodiment of the present invention.

Fig. 5 is a flowchart of an operation method of a secondary controller applied to a secondary side of a power converter according to a third embodiment of the present invention.

Wherein the reference numerals are as follows:

100 power converter

102 bridge rectifier

104 primary side winding

106 secondary side winding

108 secondary side auxiliary winding

110 signal source

112 primary side auxiliary winding

114 primary controller

115 resistance

116 power switch

118. 120 short-circuit winding switch

122 diode

200 secondary controller

202 control signal generating circuit

GCS first gate control signal

IP primary side current

IS secondary side current

PS pulse signal

PRI Primary side

SEC Secondary side

SWG short circuit control signal

TS enable signal

Time T1-T7

TON time interval

TDIS discharge time

Minimum off time of TOFFMIN

VAC alternating voltage

VIN input voltage

VS detection voltage

VCC operating voltage

VOUT output voltage

VSAUX, VC voltage

VTAR outputs a target voltage

400-410, 500-508 steps

Detailed Description

Referring to fig. 1, fig. 1 is a schematic diagram of a secondary controller 200 applied to a secondary side SEC of a power converter 100 according to a first embodiment of the present invention, wherein the secondary controller 200 is located on the secondary side SEC of the power converter 100, and the secondary controller 200 can be applied to a Discontinuous Conduction Mode (DCM) and a quasi-resonant mode (quasi-resonant mode) of the power converter 100, or applied to a Continuous Conduction Mode (CCM) of the power converter 100. As shown in fig. 1, the secondary controller 200 at least comprises a control signal generating circuit 202. In addition, the power converter 100 is a flyback power converter (flyback converter), and the potential of the ground terminal of the primary side PRI of the power converter 100 and the potential of the ground terminal of the secondary side SEC of the power converter 100 may be the same or different. In addition, as shown in fig. 1, the input voltage VIN of the primary-side PRI of the power converter 100 is generated by rectifying an ac voltage VAC through a bridge rectifier 102, and the energy of the primary-side PRI of the power converter 100 can be transferred to the secondary-side SEC of the power converter 100 through the primary-side winding 104 and the secondary-side winding 106 of the power converter 100.

Referring to fig. 2, fig. 2 IS a schematic diagram illustrating the output voltage VOUT of the secondary side SEC of the power converter 100, the secondary side current IS, the turn-on signal TS, the short-circuit control signal SWG, and the voltage VSAUX across the secondary-side auxiliary winding 108 when the power converter 100 IS in the discontinuous conduction mode. Referring to fig. 1 and 2, before a time T1, the short-circuit control signal SWG is enabled by the control signal generating circuit 202 and the output voltage VOUT is greater than an output target voltage VTAR, wherein the output voltage VOUT is detected by the control signal generating circuit 202. At time T1, since the output voltage VOUT is less than the output target voltage VTAR, the control signal generating circuit 202 can enable a pulse signal PS to a signal source 110 and turn off the short-circuit control signal SWG, wherein the signal source 110 can enable the turn-on signal TS according to the pulse signal PS, and the signal source 110 can be a voltage source or a current source. During the enabled period of the turn-on signal TS (between time T1 and time T2), the voltage VSAUX at the secondary-side auxiliary winding 108 of the power converter 100 varies with the turn-on signal TS, and the voltage VSAUX may be coupled to the primary-side auxiliary winding 112 of the power converter 100 to enable the primary-side auxiliary winding 112 to generate a voltage VC, wherein the primary controller 114 of the primary-side PRI of the power converter 100 may enable a first gate control signal GCS to the power switch 116 of the primary-side PRI of the power converter 100 according to the voltage VC to turn on the power switch 116, resulting in the primary-side PRI of the power converter 100 being turned on (at time T2). In an embodiment of the invention, when the voltage VC is greater than a reference voltage, the primary controller 114 may accordingly generate the first gate control signal GCS to the power switch 116, which causes the primary side PRI of the power converter 100 to turn on. In another embodiment of the present invention, when the slope of the voltage VC is greater than a reference value, the primary controller 114 may accordingly generate the first gate control signal GCS to the power switch 116, which causes the primary side PRI of the power converter 100 to turn on.

In addition, referring to fig. 1 and 2 again, at a time T3, when the detection voltage VS of the primary-side PRI of the power converter 100 is greater than a detection target voltage, the primary controller 114 may turn off the first gate control signal GCS to turn off the primary-side PRI of the power converter 100, resulting in the primary-side PRI of the power converter 100 turning off, where the detection voltage VS is determined by the primary-side current IP flowing through the primary-side PRI of the power converter 100 and a resistor 115.

As shown in fig. 2, after a time period TON (i.e., the on period of the power switch 116), the control signal generating circuit 202 determines a discharging time TDIS of the secondary side SEC of the power converter 100 according to the voltage VSAUX, wherein the discharging time TDIS IS between a time T4 and a time T5, and at this time, the secondary side SEC of the power converter 100 starts to discharge because the primary side PRI of the power converter 100 IS turned off (as shown in fig. 2, the secondary side current IS decreases from a maximum value at a time T4). In addition, the operation principle that the control signal generating circuit 202 determines the discharge time TDIS of the secondary side SEC of the power converter 100 according to the voltage VSAUX is well known to those skilled in the art, and will not be described herein. In addition, the control signal generating circuit 202 may enable the short-circuit control signal SWG to the short-circuit winding (short winding) switches 118 and 120 after a discharge time TDIS (a time T6) of the secondary side SEC of the power converter 100 to enable the short-circuit winding switches 118 and 120 to be turned on according to the short-circuit control signal SWG, wherein the short-circuit winding switches 118 and 120 are coupled between two terminals of the secondary side auxiliary winding 108 of the power converter 100, the discharge time TDIS and the short-circuit control signal SWG have a predetermined time therebetween (i.e., a time interval between a time T5 and a time T6), and the predetermined time may be changed according to requirements of a designer of the power converter 100. At this time, since the short-circuit winding switches 118 and 120 are turned on, both ends of the secondary side auxiliary winding 108 are short-circuited. In addition, if the shorting winding switches 118 and 120 are not present, the voltage VSAUX resonates (as shown by the dashed line after time T6) due to the resonant effect of the primary winding 104 and the secondary auxiliary winding 108 of the power converter 100, so that the primary controller 114 may turn on the primary PRI of the power converter 100 due to the resonance of the secondary auxiliary winding 108, that is, the resonance on the voltage VSAUX may turn on the primary PRI of the power converter 100 and the secondary SEC of the power converter 100 at the same time. Therefore, as shown in fig. 2, after the short-circuit winding switches 118 and 120 are turned on, the voltage VSAUX will not resonate to ensure that the primary controller 114 will not turn on the primary PRI of the power converter 100. In addition, the invention is not limited to the power converter 100 including the short-circuit winding switches 118 and 120, that is, the power converter 100 may include at least one short-circuit winding switch.

In addition, in another embodiment of the present invention, the power converter 100 replaces the diode 122 of the secondary side SEC of the power converter 100 with a synchronous rectification switch, wherein the synchronous rectification switch is installed at the ground terminal of the secondary side SEC of the power converter 100. At this time, the control signal generating circuit 202 may control the synchronous rectification switch to be turned on and off according to the voltage VSAUX. As shown in fig. 2, the control signal generating circuit 202 may generate a second gate control signal to the synchronous rectification switch according to the voltage VSAUX between time T4 and time T5, wherein the synchronous rectification switch may be turned on according to the second gate control signal, resulting in turning on the secondary side SEC of the power converter 100. The enable period of the second gate control signal is related to the discharge time TDIS of the secondary side SEC of the power converter 100.

As shown in fig. 2, at a time T7, because the output voltage VOUT is again less than the output target voltage VTAR, the control signal generating circuit 202 can enable the pulse signal PS to the signal source 110 again. In addition, after the time T7, the operation principle of the power converter 100, the primary controller 114 and the secondary controller 200 can refer to the operation principle of the power converter 100, the primary controller 114 and the secondary controller 200 between the time T1 and the time T6, and therefore, the description thereof is omitted. In addition, during the on-time of the primary side PRI of the power converter 100, the primary side auxiliary winding 112 may also receive the energy of the primary side PRI of the power converter 100 through the coupling primary side winding 104 to generate the operating voltage VCC of the primary controller 114.

Therefore, as shown in fig. 1, the secondary controller 200 can precisely control the power converter 100 to be turned on by the secondary-side SEC of the power converter 100 through the secondary-side auxiliary winding 108 and the turn-on signal TS, that is, the secondary controller 200 does not need to control the power converter 100 to be turned on by the secondary-side SEC of the power converter 100 through the feedback path formed by the optical coupler and the secondary-side synchronous rectification switch disclosed in the prior art. In addition, since the secondary controller 200 can control the turn-on of the power converter 100 by the secondary-side SEC of the power converter 100 through the secondary-side auxiliary winding 108 and the turn-on signal TS, the power converter can operate not only in the discontinuous conduction mode (or the quasi-resonant mode) but also in the continuous conduction mode.

Referring to fig. 3, fig. 3 IS a schematic diagram illustrating the output voltage VOUT, the secondary-side current IS, the turn-on signal TS, the short-circuit control signal SWG, and the voltage VSAUX at the secondary-side auxiliary winding 108 of the power converter 100 when the power converter 100 IS in the continuous conduction mode. Referring to fig. 1 and 3, before a time T1, the short-circuit control signal SWG is enabled by the control signal generating circuit 202 and the output voltage VOUT is greater than an output target voltage VTAR. At a time T1, because the output voltage VOUT is less than the output target voltage VTAR, the control signal generating circuit 202 may enable the pulse signal PS to the signal source 110, wherein the signal source 110 may enable the turn-on signal TS according to the pulse signal PS. In addition, at time T1, since the output voltage VOUT is less than the output target voltage VTAR, the control signal generating circuit 202 may turn off the short-circuit control signal SWG. During the enabling period of the turn-on signal TS (between time T1 and time T2), the voltage VSAUX at the secondary-side auxiliary winding 108 of the power converter 100 varies with the turn-on signal TS, and the voltage VSAUX may be coupled to the primary-side auxiliary winding 112 of the power converter 100 to enable the primary-side auxiliary winding 112 to generate the voltage VC, wherein the primary controller 114 of the primary-side PRI of the power converter 100 may enable the first gate control signal GCS to the power switch 116 of the primary-side PRI of the power converter 100 according to the voltage VC to turn on the power switch 116, resulting in the primary-side PRI of the power converter 100 being turned on (at time T2).

In addition, referring to fig. 1 and 3 again, at a time T3, when the detection voltage VS of the primary side PRI of the power converter 100 is greater than the detection target voltage, the primary controller 114 may turn off the first gate control signal GCS to turn off the primary side PRI of the power converter 100, resulting in turning off the primary side PRI of the power converter 100. As shown in fig. 3, after a time interval TON (i.e., the on period of the power switch 116), the control signal generating circuit 202 may enable the on signal TS at a time T4 according to a minimum off time TOFFMIN, wherein the secondary-side current IS does not drop to zero at a time T4 because the power converter 100 IS in the continuous conduction mode, and the minimum off time TOFFMIN IS related to the maximum operating frequency of the power converter 100. In addition, as shown in fig. 3, before the control signal generation circuit 202 enables the turn-on signal TS at time T4, the output voltage VOUT starts to be smaller than the output target voltage VTAR at time T5. In addition, as shown in fig. 3, after the time T4, the operation principle of the power converter 100, the primary controller 114 and the secondary controller 200 may refer to the operation principle of the power converter 100, the primary controller 114 and the secondary controller 200 between the time T1 and the time T4, and therefore, the description thereof is omitted here.

Referring to fig. 1, 2 and 4, fig. 4 is a flowchart illustrating an operation method of a secondary controller applied to a secondary side of a power converter according to a second embodiment of the present invention. The operation method of fig. 4 IS described by using the power converter 100, the primary controller 114, and the secondary controller 200 of fig. 1, and the output voltage VOUT, the secondary-side current IS, the turn-on signal TS, the short-circuit control signal SWG, and the voltage VSAUX of fig. 2, and the detailed steps are as follows:

step 400: starting;

step 402: the control signal generation circuit 202 enables the short-circuit control signal SWG;

step 404: whether the output voltage VOUT of the power converter 100 is less than the output target voltage VTAR; if so, go to step 406; if not, go to step 402 again;

step 406: the control signal generating circuit 202 enables the pulse signal PS to the signal source 110 and turns off the short circuit control signal SWG;

step 408: whether the detection voltage VS of the primary side PRI of the power converter 100 is greater than the detection target voltage; if so, go to step 410; if not, go to step 408 again;

step 410: the control signal generating circuit 202 enables the short-circuit control signal SWG to the short-circuit winding switches 118 and 120 after the discharge time TDIS of the secondary side SEC of the power converter 100 to turn on the short-circuit winding switches 118 and 120, and then the step 402 is skipped.

In step 402, referring to fig. 1 and 2, before time T1, the short-circuit control signal SWG is enabled by the control signal generating circuit 202 and the output voltage VOUT is greater than the output target voltage VTAR. At time T1, in step 406, because the output voltage VOUT is less than the output target voltage VTAR, the control signal generating circuit 202 can enable the pulse signal PS to the signal source 110 and turn off the short-circuit control signal SWG, wherein the signal source 110 can enable the turn-on signal TS according to the pulse signal PS. As shown in fig. 2, during the enabled period of the turn-on signal TS (between time T1 and time T2), the voltage VSAUX at the secondary-side auxiliary winding 108 of the power converter 100 varies with the turn-on signal TS, and the voltage VSAUX may be coupled to the primary-side auxiliary winding 112 of the power converter 100 to enable the primary-side auxiliary winding 112 to generate the voltage VC, wherein the primary controller 114 of the primary-side PRI of the power converter 100 may enable a first gate control signal GCS to the power switch 116 of the primary-side PRI of the power converter 100 according to the voltage VC to turn on the power switch 116, resulting in the primary-side PRI of the power converter 100 being turned on (at time T2).

In step 408, referring to fig. 1 and 2 again, at time T3, when the detection voltage VS of the primary side PRI of the power converter 100 is greater than the detection target voltage, the primary controller 114 may turn off the first gate control signal GCS to turn off the primary side PRI of the power converter 100, resulting in turning off the primary side PRI of the power converter 100.

As shown in fig. 2, after the time interval TON (i.e., the on period of the power switch 116), the control signal generating circuit 202 determines the discharge time TDIS of the secondary side SEC of the power converter 100 according to the voltage VSAUX, wherein the discharge time TDIS IS between the time T4 and the time T5, and at this time, the secondary side SEC of the power converter 100 starts to discharge because the primary side PRI of the power converter 100 IS turned off (as shown in fig. 2, the secondary side current IS decreases from a maximum value at the time T4). In step 410, the control signal generating circuit 202 may enable the short-circuit control signal SWG to the short-circuit winding switches 118 and 120 after a discharge time TDIS (time T6) of the secondary side SEC of the power converter 100 to turn on the short-circuit winding switches 118 and 120 according to the short-circuit control signal SWG, wherein the discharge time TDIS and the short-circuit control signal SWG have the predetermined time therebetween (i.e., a time interval between time T5 and time T6), and the predetermined time may be changed according to the needs of the designer of the power converter 100. At this time, since the short-circuit winding switches 118 and 120 are turned on, both ends of the secondary side auxiliary winding 108 are short-circuited. Therefore, as shown in fig. 2, after the short-circuit winding switches 118 and 120 are turned on, the voltage VSAUX will not resonate to ensure that the primary controller 114 will not turn on the primary PRI of the power converter 100.

In addition, as shown in fig. 2, at time T7, because the output voltage VOUT is again less than the output target voltage VTAR, the control signal generating circuit 202 may enable the pulse signal PS to the signal source 110 again and turn off. In addition, after the time T7, the operation principle of the power converter 100, the primary controller 114 and the secondary controller 200 can refer to the operation principle of the power converter 100, the primary controller 114 and the secondary controller 200 between the time T1 and the time T6, and therefore, the description thereof is omitted.

Referring to fig. 1, 3 and 5, fig. 5 is a flowchart illustrating an operation method of a secondary controller applied to a secondary side of a power converter according to a third embodiment of the present invention. The operation method of fig. 5 IS described by using the power converter 100, the primary controller 114, and the secondary controller 200 of fig. 1, and the output voltage VOUT, the secondary-side current IS, the turn-on signal TS, the short-circuit control signal SWG, and the voltage VSAUX of fig. 3, and the detailed steps are as follows:

step 500: starting;

step 502: whether the output voltage VOUT of the power converter 100 is less than the output target voltage VTAR; if so, go to step 504; if not, go to step 502 again;

step 504: the control signal generating circuit 202 enables the pulse signal PS to the signal source 110;

step 506: whether the detection voltage VS of the primary side PRI of the power converter 100 is greater than the detection target voltage; if yes, go to step 508; if not, go to step 506 again;

step 508: whether the discharge time TDIS of the secondary side SEC of the power converter 100 is greater than the minimum off time TOFFMIN; if yes, go to step 502; if not, step 508 is performed again.

Referring to fig. 1 and 3, before a time T1, the short-circuit control signal SWG is enabled by the control signal generating circuit 202 and the output voltage VOUT is greater than the output target voltage VTAR. At time T1, in step 504, because the output voltage VOUT is less than the output target voltage VTAR, the control signal generating circuit 202 may enable the pulse signal PS to the signal source 110, wherein the signal source 110 may enable the turn-on signal TS according to the pulse signal PS. In addition, at time T1, since the output voltage VOUT is less than the output target voltage VTAR, the control signal generating circuit 202 may turn off the short-circuit control signal SWG. During the enabling period of the turn-on signal TS (between time T1 and time T2), the voltage VSAUX at the secondary-side auxiliary winding 108 of the power converter 100 varies with the turn-on signal TS, and the voltage VSAUX may be coupled to the primary-side auxiliary winding 112 of the power converter 100 to enable the primary-side auxiliary winding 112 to generate the voltage VC, wherein the primary controller 114 of the primary-side PRI of the power converter 100 may enable the first gate control signal GCS to the power switch 116 of the primary-side PRI of the power converter 100 according to the voltage VC to turn on the power switch 116, resulting in the primary-side PRI of the power converter 100 being turned on (at time T2).

In step 506, referring to fig. 1 and 3 again, at time T3, when the detection voltage VS of the primary side PRI of the power converter 100 is greater than the detection target voltage, the primary controller 114 may turn off the first gate control signal GCS to turn off the primary side PRI of the power converter 100, resulting in turning off the primary side PRI of the power converter 100.

In step 508, as shown in fig. 3, after the time interval TON (i.e., the on period of the power switch 116), the control signal generation circuit 202 may enable the turn-on signal TS at time T4 according to the minimum off-time TOFFMIN, wherein the secondary-side current IS does not drop to zero at time T4 because the power converter 100 IS in the continuous conduction mode, and the minimum off-time TOFFMIN IS related to the maximum operating frequency of the power converter 100. In addition, as shown in fig. 3, before the control signal generation circuit 202 enables the turn-on signal TS at time T4, the output voltage VOUT starts to be smaller than the output target voltage VTAR at time T5. In addition, as shown in fig. 3, after the time T4, the operation principle of the power converter 100, the primary controller 114 and the secondary controller 200 may refer to the operation principle of the power converter 100, the primary controller 114 and the secondary controller 200 between the time T1 and the time T4, and therefore, the description thereof is omitted here.

In summary, the secondary controller applied to the secondary side of the power converter and the operating method thereof disclosed by the present invention couple the turn-on signal enabled by the signal source to the primary side auxiliary winding by using the secondary side auxiliary winding so that the primary controller turns on the power converter according to the voltage variation of the primary side auxiliary winding. Therefore, compared with the prior art, the secondary controller disclosed by the invention does not need to control the on/off of the power converter through a feedback path formed by an optical coupler and a secondary side synchronous rectification switch, so that the power converter disclosed by the invention has lower cost and has quicker dynamic response to the change of the output voltage. In addition, since the secondary controller can control the turn-on of the power converter through the secondary side auxiliary winding and the turn-on signal, the power converter can operate not only in the discontinuous conduction mode (or the quasi-resonant mode) but also in the continuous conduction mode.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.