Secondary controller applied to secondary side of power converter and method of operation thereof

Abstract

A secondary controller applied to a secondary side of a power converter and an operating method thereof are disclosed. The secondary controller includes a control signal generating circuit. The control signal generating circuit is coupled to an output terminal of the secondary side of the power converter 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 an on signal according to the pulse signal. The 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 make the primary side auxiliary winding generate a voltage, and a primary controller of the primary side of the power converter enables the primary side of the power converter according to the voltage. Therefore, the power converter disclosed by the present application has lower cost and faster dynamic response to the change of the output voltage.

Description

Technical Field

[0001] This invention relates to a secondary controller and its operating method applied to the secondary side of a power converter, and more particularly to a secondary controller and its operating method that can control the power converter to turn on using a secondary auxiliary winding and an on signal when the power converter is in a discontinuous conduction mode (DCM), a quasi-resonant mode, or a continuous conduction mode (CCM). Background Technology

[0002] In existing technology, power converter designers can control the switching on and off of the power converter using a primary controller applied to the primary side of the power converter or a secondary controller applied to the secondary side of the power converter. The primary controller uses an auxiliary winding on the primary side of the power converter to detect changes in the output voltage on the secondary side to control the switching on and off of the power converter. The secondary controller directly detects changes in the output voltage on the secondary side of the power converter and transmits these changes to the primary controller via a feedback path consisting of an optocoupler and a secondary-side synchronous rectifier switch to control the switching on and off of the power converter. Because the primary controller detects changes in the output voltage indirectly (through the auxiliary winding), it is less accurate than the secondary controller in controlling the switching on and off of the power converter. However, because the secondary controller controls the switching on and off of the power converter through the secondary-side synchronous rectifier switch, the power converter can only operate in a discontinuous conduction mode (DCM). However, when the power converter is controlled to turn on and off using the secondary controller, the primary side of the power converter must be turned on via the conduction of the secondary-side synchronous rectifier switch and the auxiliary winding. Therefore, the secondary-side synchronous rectifier switch is a necessary component on the secondary side of the power converter, which limits the power converter's architecture. Thus, the solutions disclosed in the prior art are not a good choice for power converter designers. Summary of the Invention

[0003] One embodiment of the present invention discloses a secondary controller applied to the secondary side of a power converter. The secondary controller includes a control signal generation circuit. The control signal generation circuit is coupled to the output terminal of the secondary side of the power converter, and is used to detect the output voltage of the secondary side and activate a pulse signal to a signal source on the secondary side of the power converter, wherein the signal source activates an enable signal according to the pulse signal; the enable signal is coupled to the primary side auxiliary winding of the power converter through the secondary side auxiliary winding, causing the primary side auxiliary winding to generate a voltage, and the primary controller on the primary side of the power converter enables the primary side of the power converter according to the voltage.

[0004] Another embodiment of the present invention discloses an operation method for a secondary controller applied to the secondary side of a power converter, wherein the secondary controller includes a control signal generation circuit, and the operation method includes: when the output voltage of the secondary side of the power converter is less than a target output voltage, the control signal generation circuit enables a pulse signal to a signal source on the secondary side of the power converter and disables a short-circuit control signal, wherein the signal source enables an on signal according to the pulse signal, the on signal being coupled to a primary side auxiliary winding of the power converter via a secondary side auxiliary winding to generate a voltage in the primary side auxiliary winding, and a primary controller on the primary side of the power converter enables the primary side of the power converter to turn on according to the voltage; during the primary side turn-on period, when the detected voltage of the primary side of the power converter is greater than a target detection voltage, the primary controller disables the primary side of the power converter; and after a discharge time on the secondary side of the power converter, the control signal generation circuit enables a short-circuit control signal to at least one short-circuit winding switch to turn on the at least one short-circuit winding switch.

[0005] Another embodiment of the present invention discloses an operation method for a secondary controller applied to the secondary side of a power converter, wherein the secondary controller includes a control signal generation circuit, and the operation method includes: when the discharge time of the secondary side of the power converter is greater than a minimum shutdown time and the output voltage of the secondary side of the power converter is less than a target output voltage, the control signal generation circuit activates a pulse signal to a signal source on the secondary side of the power converter, wherein the signal source activates an enable signal according to the pulse signal, the enable signal is coupled to the primary side auxiliary winding of the power converter through the secondary side auxiliary winding of the power converter to generate a voltage in the primary side auxiliary winding, and the primary controller on the primary side of the power converter enables the primary side of the power converter according to the voltage; and during the primary side of the power converter being enabled, when the detected voltage of the primary side of the power converter is greater than a target detection voltage, the primary controller disables the primary side of the power converter.

[0006] This invention discloses a secondary controller and its operating method applied to the secondary side of a power converter. The secondary controller and operating method utilize the secondary auxiliary winding of the power converter to couple an enable signal from the secondary-side signal source to the primary auxiliary winding of the power converter, causing the primary controller on the primary side of the power converter to turn on the power converter according to the voltage change of the primary auxiliary winding. Therefore, compared to the prior art, because the secondary controller disclosed in this invention does not need to control the power converter's turn-on through a feedback path composed of an optocoupler and a secondary-side synchronous rectifier switch, the power converter disclosed in this invention has lower cost and faster dynamic response to changes in the output voltage. Furthermore, because the secondary controller can control the power converter's turn-on through the secondary auxiliary winding and the enable 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. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of a secondary controller applied to the secondary side of a power converter, as disclosed in the first embodiment of the present invention.

[0008] Figure 2 This is a schematic diagram illustrating the output voltage, secondary current, turn-on signal, short-circuit control signal, and voltage on the secondary auxiliary winding of the power converter when the power converter is in the discontinuous conduction mode.

[0009] Figure 3This is a schematic diagram illustrating the output voltage, secondary current, turn-on signal, short-circuit control signal, and voltage on the secondary auxiliary winding of the power converter when the power converter is in the continuous conduction mode.

[0010] Figure 4 This is a flowchart of an operation method for a secondary controller applied to the secondary side of a power converter, as disclosed in the second embodiment of the present invention.

[0011] Figure 5 This is a flowchart of an operation method for a secondary controller applied to the secondary side of a power converter, as disclosed in the third embodiment of the present invention.

[0012] The reference numerals in the attached figures are explained as follows:

[0013] 100 power converter

[0014] 102 Bridge rectifier

[0015] 104 Primary winding

[0016] 106 Secondary winding

[0017] 108 Secondary auxiliary winding

[0018] 110 signal source

[0019] 112 Primary auxiliary winding

[0020] 114 Primary Controller

[0021] 115 resistor

[0022] 116 Power Switch

[0023] 118, 120 short-circuit winding switch

[0024] 122 diode

[0025] 200 secondary controllers

[0026] 202 Control Signal Generation Circuit

[0027] GCS First Gate Control Signal

[0028] IP primary current

[0029] IS secondary current

[0030] PS pulse signal

[0031] PRI primary side

[0032] SEC secondary side

[0033] SWG short-circuit control signal

[0034] TS Enable Signal

[0035] T1-T7 Time

[0036] TON time interval

[0037] TDIS discharge time

[0038] TOFFMIN Minimum Closing Time

[0039] VAC (Alternating Current) voltage

[0040] VIN Input Voltage

[0041] VS Detection Voltage

[0042] VCC operating voltage

[0043] VOUT output voltage

[0044] VSAUX, VC voltage

[0045] VTAR output target voltage

[0046] Steps for 400-410 and 500-508 Detailed Implementation

[0047] Please refer to Figure 1 , Figure 1 This is a schematic diagram of a secondary controller 200 applied to the secondary side SEC of a power converter 100, as disclosed in the first embodiment of the present invention. The secondary controller 200 is located on the secondary side SEC of the power converter 100, and can be applied to a discontinuous conduction mode (DCM) and a quasi-resonant mode of the power converter 100, or to a continuous conduction mode (CCM) of the power converter 100. Figure 1 As shown, the secondary controller 200 includes at least a control signal generation circuit 202. Additionally, the power converter 100 is a flyback power converter, and the potential of the ground terminal on the primary side PRI of the power converter 100 and the potential of the ground terminal on the secondary side SEC of the power converter 100 may be the same or different. Furthermore, as... Figure 1As shown, 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.

[0048] Please refer to Figure 2 , Figure 2 This is a schematic diagram illustrating the output voltage VOUT, secondary current IS, turn-on signal TS, short-circuit control signal SWG, and voltage VSAUX on the secondary auxiliary winding 108 of the power converter 100 when the power converter 100 is in the discontinuous conduction mode. Please refer to the following... Figure 1 , 2 Before time T1, the short-circuit control signal SWG is enabled by the control signal generation circuit 202 and the output voltage VOUT is greater than a target output voltage VTAR, where the output voltage VOUT is detected by the control signal generation circuit 202. At time T1, because the output voltage VOUT is less than the target output voltage VTAR, the control signal generation circuit 202 can enable a pulse signal PS to a signal source 110 and disable the short-circuit control signal SWG. The signal source 110 can enable an 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 activation period of the enable signal TS (between time T1 and time T2), the voltage VSAUX on the secondary auxiliary winding 108 of the power converter 100 changes with the enable signal TS, and the voltage VSAUX can be coupled to the primary auxiliary winding 112 of the power converter 100 to generate a voltage VC in the primary auxiliary winding 112. The primary controller 114 of the primary PRI of the power converter 100 can then activate a first gate control signal GCS to the power switch 116 of the primary PRI of the power converter 100 based on the voltage VC, thereby turning on the power switch 116 and causing the primary PRI of the power converter 100 to turn on (at time T2). In one embodiment of the invention, when the voltage VC is greater than a reference voltage, the primary controller 114 can generate the first gate control signal GCS to the power switch 116, causing the primary PRI of the power converter 100 to turn on. In another embodiment of the invention, when the slope of voltage VC is greater than a reference value, primary controller 114 may generate a first gate control signal GCS to power switch 116, causing the primary side PRI of power converter 100 to turn on.

[0049] Additionally, please refer to Figure 1 , 2At 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 can turn off the first gate control signal GCS to turn off the primary side PRI of the power converter 100, causing the primary side PRI of the power converter 100 to be turned off, wherein 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.

[0050] like Figure 2 As shown, after a time interval TON (that is, during the on-time of power switch 116), the control signal generation circuit 202 can determine the discharge time TDIS of the secondary side SEC of power converter 100 according to the voltage VSAUX, wherein the discharge time TDIS is between a time interval T4 and a time interval T5, and at this time, because the primary side PRI of power converter 100 is off, the secondary side SEC of power converter 100 begins to discharge (e.g. Figure 2 As shown, the secondary current IS decreases from a maximum value at time T4. Furthermore, the operating principle of the control signal generation circuit 202, which determines the discharge time TDIS of the secondary side SEC of the power converter 100 based on the voltage VSAUX, is well known to those skilled in the art and will not be elaborated here. Additionally, the control signal generation circuit 202 can activate a short-circuit control signal SWG to the short-circuit winding switches 118 and 120 after the discharge time TDIS (time T6) of the secondary side SEC of the power converter 100, causing the short-circuit winding switches 118 and 120 to open according to the short-circuit control signal SWG. The short-circuit winding switches 118 and 120 are coupled between the two ends of the secondary side auxiliary winding 108 of the power converter 100. There is a predetermined time between the discharge time TDIS and the short-circuit control signal SWG (i.e., the time interval between time T5 and time T6), and this predetermined time can be changed according to the needs of the designer of the power converter 100. At this time, because the short-circuit winding switches 118 and 120 are open, the two ends of the secondary auxiliary winding 108 will be short-circuited. Furthermore, if the short-circuit winding switches 118 and 120 are not present, the voltage VSAUX will resonate due to the resonance of the primary winding 104 and the secondary auxiliary winding 108 of the power converter 100 (as shown by the dashed line after time T6). This could cause the primary controller 114 to turn on the primary side PRI of the power converter 100 due to the resonance of the secondary auxiliary winding 108. In other words, the resonance on the voltage VSAUX could cause the primary side PRI and the secondary side SEC of the power converter 100 to turn on simultaneously. Therefore, as... Figure 2As shown, after the short-circuit winding switches 118 and 120 are turned on, the voltage VSAUX will not resonate, ensuring that the primary controller 114 will not turn on the primary side PRI of the power converter 100. Furthermore, the present 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.

[0051] In another embodiment of the invention, the power converter 100 uses a synchronous rectifier switch instead of the diode 122 on the secondary side SEC of the power converter 100, wherein the synchronous rectifier switch is mounted at the ground terminal of the secondary side SEC of the power converter 100. In this case, the control signal generation circuit 202 can control the synchronous rectifier switch to turn on and off according to the voltage VSAUX. Figure 2 As shown, the control signal generation circuit 202 can generate a second gate control signal to the synchronous rectifier switch based on the voltage VSAUX between time T4 and time T5. The synchronous rectifier switch can be turned on according to the second gate control signal, causing the secondary side SEC of the power converter 100 to turn on. Furthermore, the activation period of the second gate control signal is related to the discharge time TDIS of the secondary side SEC of the power converter 100.

[0052] like Figure 2 As shown, at time T7, because the output voltage VOUT is again less than the target output voltage VTAR, the control signal generation circuit 202 can reactivate the pulse signal PS to the signal source 110. Furthermore, after time T7, the operating principles of the power converter 100, primary controller 114, and secondary controller 200 can refer to the operating principles of the power converter 100, primary controller 114, and secondary controller 200 between time T1 and time T6, so they will not be repeated here. Additionally, during the primary-side PRI activation period of the power converter 100, the primary-side auxiliary winding 112 can also receive energy from the primary-side PRI of the power converter 100 through coupling with the primary-side winding 104 to generate the operating voltage VCC of the primary controller 114.

[0053] Therefore, as Figure 1As shown, the secondary controller 200 can precisely control the power converter 100 to turn on via the secondary-side SEC through the secondary-side auxiliary winding 108 and the turn-on signal TS. In other words, the secondary controller 200 does not need to use the feedback path consisting of an optocoupler and a secondary-side synchronous rectifier switch as disclosed in the prior art to control the power converter 100 to turn on via the secondary-side SEC. Furthermore, because the secondary controller 200 can control the power converter 100 to turn on via the secondary-side SEC 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.

[0054] Please refer to Figure 3 , Figure 3 This is a schematic diagram illustrating the output voltage VOUT, secondary current IS, turn-on signal TS, short-circuit control signal SWG, and voltage VSAUX on the secondary auxiliary winding 108 of the power converter 100 when the power converter 100 is in the continuous conduction mode. Please refer to the following... Figure 1 , 3 Before time T1, the short-circuit control signal SWG is enabled by the control signal generation circuit 202 and the output voltage VOUT is greater than a target output voltage VTAR. At time T1, because the output voltage VOUT is less than the target output voltage VTAR, the control signal generation circuit 202 can send a pulse signal PS to the signal source 110, whereby the signal source 110 can enable the on signal TS according to the pulse signal PS. Additionally, at time T1, because the output voltage VOUT is less than the target output voltage VTAR, the control signal generation circuit 202 can also disable the short-circuit control signal SWG. During the activation period of the enable signal TS (between time T1 and time T2), the voltage VSAUX on the secondary auxiliary winding 108 of the power converter 100 will change with the enable signal TS, and the voltage VSAUX can be coupled to the primary auxiliary winding 112 of the power converter 100 to generate a voltage VC in the primary auxiliary winding 112. The primary controller 114 of the primary PRI of the power converter 100 can enable the first gate control signal GCS to the power switch 116 of the primary PRI of the power converter 100 according to the voltage VC to turn on the power switch 116, causing the primary PRI of the power converter 100 to turn on (at time T2).

[0055] Additionally, please refer to Figure 1 , 3At a time T3, when the detected voltage VS of the primary side PRI of the power converter 100 is greater than the detected target voltage, the primary controller 114 can turn off the first gate control signal GCS to turn off the primary side PRI of the power converter 100, causing the primary side PRI of the power converter 100 to be turned off. Figure 3 As shown, after a time interval TON (i.e., the on-time of power switch 116), control signal generation circuit 202 can enable on-signal TS at time T4 according to a minimum off-time TOFFMIN. Since power converter 100 is in the continuous conduction mode, the secondary current IS will not drop to zero at time T4, and the minimum off-time TOFFMIN is related to the maximum operating frequency of power converter 100. Additionally, as... Figure 3 As shown, before the enable signal TS is activated at time T4, the output voltage VOUT of the control signal generation circuit 202 is lower than the target output voltage VTAR starting at time T5. Additionally, as... Figure 3 As shown, after time T4, the operating principles of the power converter 100, primary controller 114 and secondary controller 200 can be referred to the operating principles of the power converter 100, primary controller 114 and secondary controller 200 between time T1 and time T4, so they will not be repeated here.

[0056] Please refer to Figure 1 , 2 4, Figure 4 This is a flowchart of an operation method for a secondary controller applied to the secondary side of a power converter, as disclosed in the second embodiment of the present invention. Figure 4 The operation method is to use Figure 1 The power converter 100, primary controller 114, and secondary controller 200, and Figure 2 The output voltage VOUT, secondary current IS, turn-on signal TS, short-circuit control signal SWG, and voltage VSAUX are explained in detail below:

[0057] Step 400: Begin;

[0058] Step 402: Control signal generation circuit 202 enables short-circuit control signal SWG;

[0059] Step 404: Is the output voltage VOUT of the power converter 100 less than the target output voltage VTAR? If yes, proceed to step 406; if no, proceed to step 402 again.

[0060] Step 406: Control signal generation circuit 202 enables pulse signal PS to signal source 110 and disables short-circuit control signal SWG;

[0061] Step 408: Is the detection voltage VS of the primary side PRI of the power converter 100 greater than the detection target voltage? If yes, proceed to step 410; if no, proceed to step 408 again.

[0062] Step 410: After the discharge time TDIS of the secondary side SEC of the power converter 100, the control signal generation circuit 202 enables the short-circuit control signal SWG to the short-circuit winding switches 118 and 120 to open the short-circuit winding switches 118 and 120, and jumps back to step 402.

[0063] In step 402, please refer to Figure 1 , 2 Before time T1, the short-circuit control signal SWG is enabled by the control signal generation circuit 202 and the output voltage VOUT is greater than the output target voltage VTAR. In step 406, at time T1, because the output voltage VOUT is less than the output target voltage VTAR, the control signal generation circuit 202 can enable the pulse signal PS to the signal source 110 and disable the short-circuit control signal SWG, wherein the signal source 110 can enable the on signal TS according to the pulse signal PS. Figure 2 As shown, during the activation period of the turn-on signal TS (between time T1 and time T2), the voltage VSAUX on the secondary auxiliary winding 108 of the power converter 100 will change with the turn-on signal TS, and the voltage VSAUX can be coupled to the primary auxiliary winding 112 of the power converter 100 to generate a voltage VC in the primary auxiliary winding 112. The primary controller 114 of the primary PRI of the power converter 100 can enable a first gate control signal GCS to the power switch 116 of the primary PRI of the power converter 100 according to the voltage VC to turn on the power switch 116, causing the primary PRI of the power converter 100 to turn on (at time T2).

[0064] In step 408, please refer to... Figure 1 , 2 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 can turn off the first gate control signal GCS to turn off the primary side PRI of the power converter 100, causing the primary side PRI of the power converter 100 to be turned off.

[0065] like Figure 2As shown, after the time interval TON (that is, during the on-time of power switch 116), the control signal generation circuit 202 can determine the discharge time TDIS of the secondary side SEC of power converter 100 according to the voltage VSAUX, where the discharge time TDIS is between time T4 and time T5, and at this time, because the primary side PRI of power converter 100 is off, the secondary side SEC of power converter 100 begins to discharge (e.g. Figure 2 As shown, the secondary side current IS decreases from a maximum value at time T4. In step 410, the control signal generation circuit 202 can activate the short-circuit control signal SWG to the short-circuit winding switches 118 and 120 after the discharge time TDIS (time T6) of the secondary side SEC of the power converter 100, so that the short-circuit winding switches 118 and 120 open according to the short-circuit control signal SWG, wherein there is a predetermined time between the discharge time TDIS and the short-circuit control signal SWG (that is, the time interval between time T5 and time T6), and the predetermined time can be changed according to the needs of the designer of the power converter 100. At this time, because the short-circuit winding switches 118 and 120 are open, the two ends of the secondary side auxiliary winding 108 will be short-circuited. Therefore, as Figure 2 As shown, 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 side PRI of the power converter 100.

[0066] In addition, such as Figure 2 As shown, at time T7, because the output voltage VOUT is again less than the output target voltage VTAR, the control signal generation circuit 202 can re-enable the pulse signal PS to the signal source 110 and then shut it down. Furthermore, after time T7, the operating principles of the power converter 100, primary controller 114, and secondary controller 200 can be referred to the operating principles of the power converter 100, primary controller 114, and secondary controller 200 between time T1 and time T6, so they will not be repeated here.

[0067] Please refer to Figure 1 , 3 5, Figure 5 This is a flowchart of an operation method for a secondary controller applied to the secondary side of a power converter, as disclosed in the third embodiment of the present invention. Figure 5 The operation method is to use Figure 1 The power converter 100, primary controller 114, and secondary controller 200, and Figure 3 The output voltage VOUT, secondary current IS, turn-on signal TS, short-circuit control signal SWG, and voltage VSAUX are explained in detail below:

[0068] Step 500: Begin;

[0069] Step 502: Is the output voltage VOUT of the power converter 100 less than the target output voltage VTAR? If yes, proceed to step 504; if no, proceed to step 502 again.

[0070] Step 504: Control signal generation circuit 202 activates pulse signal PS to signal source 110;

[0071] Step 506: Is the detection voltage VS of the primary side PRI of the power converter 100 greater than the detection target voltage? If yes, proceed to step 508; if no, proceed to step 506 again.

[0072] Step 508: Is the discharge time TDIS of the secondary side SEC of the power converter 100 greater than the minimum shutdown time TOFFMIN? If yes, proceed to step 502; if no, proceed to step 508 again.

[0073] Please refer to Figure 1 , 3 Before time T1, the short-circuit control signal SWG is enabled by the control signal generation circuit 202 and the output voltage VOUT is greater than the output target voltage VTAR. In step 504, at time T1, because the output voltage VOUT is less than the output target voltage VTAR, the control signal generation circuit 202 can enable the pulse signal PS to the signal source 110, whereby the signal source 110 can enable the on signal TS according to the pulse signal PS. Additionally, at time T1, because the output voltage VOUT is less than the output target voltage VTAR, the control signal generation circuit 202 can also disable the short-circuit control signal SWG. During the activation period of the enable signal TS (between time T1 and time T2), the voltage VSAUX on the secondary auxiliary winding 108 of the power converter 100 will change with the enable signal TS, and the voltage VSAUX can be coupled to the primary auxiliary winding 112 of the power converter 100 to generate a voltage VC in the primary auxiliary winding 112. The primary controller 114 of the primary PRI of the power converter 100 can enable the first gate control signal GCS to the power switch 116 of the primary PRI of the power converter 100 according to the voltage VC to turn on the power switch 116, causing the primary PRI of the power converter 100 to turn on (at time T2).

[0074] In step 506, please refer to... Figure 1 , 3 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 can turn off the first gate control signal GCS to turn off the primary side PRI of the power converter 100, causing the primary side PRI of the power converter 100 to be turned off.

[0075] In step 508, as Figure 3 As shown, after the time interval TON (that is, during the on-time of power switch 116), the control signal generation circuit 202 can enable the on-time signal TS at time T4 according to the minimum off-time TOFFMIN. Since the power converter 100 is in the continuous conduction mode, the secondary current IS will not drop to zero at time T4, and the minimum off-time TOFFMIN is related to the maximum operating frequency of the power converter 100. Additionally, as... Figure 3 As shown, before the enable signal TS is activated at time T4, the output voltage VOUT of the control signal generation circuit 202 is less than the target output voltage VTAR starting at time T5. Additionally, as... Figure 3 As shown, after time T4, the operating principles of the power converter 100, primary controller 114 and secondary controller 200 can be referred to the operating principles of the power converter 100, primary controller 114 and secondary controller 200 between time T1 and time T4, so they will not be repeated here.

[0076] In summary, the secondary controller and its operating method disclosed in this invention, applied to the secondary side of a power converter, utilizes the secondary-side auxiliary winding to couple the enable signal from the signal source to the primary-side auxiliary winding, causing the primary controller to turn on the power converter based on voltage changes in the primary-side auxiliary winding. Therefore, compared to the prior art, because the secondary controller disclosed in this invention does not require a feedback path consisting of an optocoupler and a secondary-side synchronous rectifier switch to control the power converter's activation, the power converter disclosed in this invention has lower cost and faster dynamic response to output voltage changes. Furthermore, because the secondary controller can control the power converter's activation via the secondary-side auxiliary winding and the enable 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.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A secondary controller applied to the secondary side of a power converter, characterized in that... Include: A control signal generation circuit, coupled to the output terminal of the secondary side of the power converter, is used to detect the output voltage of the secondary side and enable a pulse signal to a signal source on the secondary side of the power converter, wherein the signal source enables an on signal according to the pulse signal, and the control signal generation 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 to turn on the at least one short-circuit winding switch, wherein when the output voltage is less than an output target voltage, the control signal generation circuit enables the pulse signal to the signal source and turns off the short-circuit control signal; The turn-on signal is coupled to the primary auxiliary winding of the power converter via the secondary auxiliary winding of the power converter, causing the primary auxiliary winding to generate a voltage, and the primary controller of the primary side of the power converter turns on the primary side of the power converter according to the voltage.

2. The secondary controller as described in claim 1, characterized in that: The power converter is a flyback power converter.

3. The secondary controller as described in claim 1, characterized in that: The at least one short-circuit winding switch is coupled to the secondary auxiliary winding.

4. The secondary controller as described in claim 1, characterized in that: The power converter is in a discontinuous conduction mode.

5. The secondary controller as described in claim 1, characterized in that: There is a predetermined time between the discharge time and the short-circuit control signal.

6. The secondary controller as described in claim 1, characterized in that: When the discharge time of the secondary side of the power converter is greater than a minimum shutdown time and the output voltage is less than a target output voltage, the control signal generation circuit enables the pulse signal to the signal source.

7. The secondary controller as described in claim 6, characterized in that: The power converter is in a continuous conduction mode.

8. The secondary controller as described in claim 1 or 6, characterized in that: During the primary-side turn-on period of the power converter, when the detected voltage on the primary side of the power converter is greater than a detected target voltage, the primary controller turns off the primary side of the power converter.

9. A method of operating a secondary controller applied to the secondary side of a power converter, the secondary controller comprising a control signal generation circuit, wherein the method of operating is characterized by comprising: When the output voltage on the secondary side of the power converter is less than a target output voltage, the control signal generation circuit activates a pulse signal to a signal source on the secondary side of the power converter and deactivates a short-circuit control signal. The signal source activates an enable signal according to the pulse signal. The enable signal is coupled to the primary side auxiliary winding of the power converter through the secondary side auxiliary winding to generate a voltage in the primary side auxiliary winding. The primary controller on the primary side of the power converter enables the primary side of the power converter to turn on according to the voltage. During the primary-side turn-on period of the power converter, when the detected voltage on the primary side of the power converter is greater than a detected target voltage, the primary controller turns off the primary side of the power converter; and The control signal generation circuit activates a short-circuit control signal to at least one short-circuit winding switch after the discharge time on the secondary side of the power converter, so that the at least one short-circuit winding switch is turned on.

10. The operating method as described in claim 9, characterized in that: After at least one short-circuit winding switch is turned on, when the output voltage is again less than the output target voltage, the control signal generation circuit re-activates the pulse signal to the signal source and turns off the short-circuit control signal again.

11. The operating method as described in claim 9, characterized in that: There is a predetermined time between the discharge time and the short-circuit control signal.

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