CN109713904B - Flyback power conversion circuit and conversion control circuit and control method thereof - Google Patents
Flyback power conversion circuit and conversion control circuit and control method thereof Download PDFInfo
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- CN109713904B CN109713904B CN201711017765.6A CN201711017765A CN109713904B CN 109713904 B CN109713904 B CN 109713904B CN 201711017765 A CN201711017765 A CN 201711017765A CN 109713904 B CN109713904 B CN 109713904B
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Abstract
A flyback power converter circuit, and a conversion control circuit and a control method thereof, the flyback power converter circuit includes: a transformer including a primary winding coupled to an input power source and a secondary winding coupled to an output node; a primary side switch coupled to the primary side winding for switching the input power source to make the secondary side winding generate an output power source at the output node; a clamping circuit, comprising: an auxiliary switch and an auxiliary capacitor connected in series with the auxiliary switch to form an auxiliary branch, and the auxiliary branch is connected in parallel with the primary winding; and a conversion control circuit for controlling the auxiliary switch to conduct an auxiliary conduction time according to an estimated conduction time of a parasitic diode of the auxiliary switch in a primary side non-conduction period of the primary side switch, wherein the auxiliary conduction time is substantially equal to and overlaps the estimated conduction time.
Description
Technical Field
The present invention relates to a flyback power converter, and more particularly, to a flyback power converter with active clamp. The invention also relates to a conversion control circuit used in the flyback mode and a control method thereof.
Background
Fig. 1 shows a prior art flyback power converter (flyback power converter 1) with active clamping (active clamping), wherein the flyback power converter 1 is used to convert an input Voltage into an output Voltage, and includes an auxiliary switch S2 and an auxiliary capacitor Cr, forming an active clamping branch, which is turned on when the primary switch S1 is turned off, so that the energy stored when the primary switch S1 is turned on and the leakage inductance Lr and the excitation inductance Lm of the primary winding are discharged through the branch and stored in the auxiliary capacitor Cr, and before the primary switch S1 is turned on, the parasitic capacitance Coss of the primary switch S1 is discharged through the energy stored in the auxiliary capacitor Cr, so that the primary switch S1 is turned on and is Zero Voltage Switching (ZVS), please refer to fig. 2A, in the prior art, the switching of the primary switch S1 and the auxiliary switch S2 are substantially opposite in phase.
The prior art shown in fig. 1 has a disadvantage in that the switching of the primary switch S1 and the auxiliary switch S2 are substantially opposite to each other, so the on-time of the auxiliary switch S2 may be too long, which causes a large circulating current (circulating current), further causing power loss.
Fig. 2B is a waveform diagram of another flyback power converter circuit with active clamping (active clamping) in the prior art, which is similar to the prior art shown in fig. 1, except that the auxiliary switch S2 has a conduction time that is not substantially opposite to that of the primary switch S1, and in this embodiment, the auxiliary switch S2 is turned on before the primary switch S1 is turned on, and the conduction time TONA is a fixed conduction time.
The prior art shown in fig. 2B has a disadvantage that, since the on-time TONA of the auxiliary switch S2 is a fixed on-time, under the application of high input voltage VI, the on-time TONA of the auxiliary switch S2 may not be enough to completely discharge the charges in the parasitic capacitance Coss of the primary switch S1, so that the primary switch S1 cannot achieve zero-voltage switching, further resulting in power loss. In addition, in the prior art, when the primary switch S1 is just switched to off, the parasitic diode D2 of the auxiliary switch S2 may be turned on, that is, during the period TOD2 in the figure, the auxiliary capacitor current ICr is turned on by the parasitic diode D2, and due to the reverse recovery charge effect of the parasitic diode D2 of the auxiliary switch S2, that is, the reverse recovery charge (Qrr) effect, the charge actually stored in the auxiliary capacitor Cr becomes small, which may not be enough to make the primary switch S1 be switched to zero voltage when it is turned on; on the other hand, if an auxiliary switch with a smaller Qrr is used, such as but not limited to a GaAs switch, the forward voltage of the parasitic diode is usually larger, and thus additional power loss is caused.
Compared with the prior art shown in fig. 1 and 2, the on-time TONA of the auxiliary switch S2 can be adjusted to ensure that the primary switch S1 can achieve zero-voltage switching, thereby reducing power loss and improving power conversion efficiency, and in addition, the auxiliary switch S2 of the present invention can be turned on within the estimated on-time of the parasitic diode D2, thereby effectively eliminating the Qrr effect or reducing the extra power loss caused by the forward voltage of the parasitic diode D2.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a flyback power conversion circuit, a conversion control circuit and a control method thereof, which can reduce power loss and improve power conversion efficiency; the Qrr effect can be effectively eliminated, or the extra power loss caused by the forward voltage of the parasitic diode can be reduced.
In order to achieve the above object, in one aspect, the present invention provides a flyback power converter circuit, including: a transformer including a primary winding coupled to an input power source and a secondary winding coupled to an output node; a primary side switch coupled to the primary side winding for switching the primary side winding to convert the input power, so that the secondary side winding generates an output power at the output node; a clamping circuit, comprising: an auxiliary switch including a parasitic diode; and an auxiliary capacitor connected in series with the auxiliary switch to form an auxiliary branch, and the auxiliary branch is connected in parallel with the primary winding; and a conversion control circuit for controlling the primary side switch and the auxiliary switch to convert the input power to generate the output power, wherein the auxiliary switch and the primary side switch are not complementarily switched; the conversion control circuit includes: a power switch control circuit for generating a primary side switch control signal to control the primary side switch; and an auxiliary switch control circuit for generating an auxiliary switch control signal to control the auxiliary switch to conduct a first auxiliary conduction time according to an estimated conduction time of the parasitic diode in a primary side non-conduction period of the primary side switch, wherein the first auxiliary conduction time is substantially equal to and overlaps the estimated conduction time.
In a preferred embodiment, the auxiliary switch control circuit further controls the auxiliary switch to be turned on for a second auxiliary on-time after the first auxiliary on-time in the primary-side off-time period.
In a preferred embodiment, the auxiliary switch control circuit determines the second auxiliary on-time according to at least one of: a current-related signal, the input voltage and the output voltage; wherein the current-related signal is related to at least one of: the output current, the on-current of the primary side switch, and the current of the primary side winding.
In a preferred embodiment, the first auxiliary conduction time and the second auxiliary conduction time are not overlapped, and the auxiliary switch is not conducted between the first auxiliary conduction time and the second auxiliary conduction time.
In a preferred embodiment, the auxiliary switch control circuit further adjusts the first auxiliary turn-on time such that the first auxiliary turn-on time is substantially the same as the second auxiliary turn-on time.
In a preferred embodiment, the auxiliary switch control circuit further controls the first auxiliary conduction time to start substantially simultaneously with the primary-side non-conduction period and the second auxiliary conduction time to end substantially simultaneously with the primary-side non-conduction period.
In a preferred embodiment, the auxiliary switch is controlled to be non-conductive when the auxiliary switch current is substantially 0.
In a preferred embodiment, the power switch control circuit controls a primary-side on-time of the primary-side switch in a feedback manner according to the output power.
From another perspective, the present invention also provides a conversion control circuit for controlling a flyback power converter circuit, the flyback power converter circuit comprising: a transformer including a primary winding coupled to an input power source and a secondary winding coupled to an output node; a primary side switch coupled to the primary side winding for switching the primary side winding to convert the input power, so that the secondary side winding generates an output power at the output node; and a clamping circuit, comprising: an auxiliary switch including a parasitic diode; and an auxiliary capacitor connected in series with the auxiliary switch to form an auxiliary branch, and the auxiliary branch is connected in parallel with the primary winding; the conversion control circuit is used for controlling the primary side switch and the auxiliary switch to convert the input power supply to generate the output power supply, wherein the auxiliary switch and the primary side switch are not complementarily switched; the conversion control circuit includes: a power switch control circuit for generating a primary side switch control signal to control the primary side switch; and an auxiliary switch control circuit for generating an auxiliary switch control signal to control the auxiliary switch to conduct a first auxiliary conduction time according to an estimated conduction time of the parasitic diode in a primary side non-conduction period of the primary side switch, wherein the first auxiliary conduction time is substantially equal to and overlaps the estimated conduction time.
From another perspective, the present invention also provides a control method for a flyback power converter circuit, wherein the flyback power converter circuit includes: a transformer including a primary winding coupled to an input power source and a secondary winding coupled to an output node; a primary side switch coupled to the primary side winding for switching the primary side winding to convert the input power, so that the secondary side winding generates an output power at the output node; and a clamping circuit, comprising: an auxiliary switch including a parasitic diode; and an auxiliary capacitor connected in series with the auxiliary switch to form an auxiliary branch, and the auxiliary branch is connected in parallel with the primary winding; the conversion control circuit is used for generating a primary side switch control signal and an auxiliary switch control signal which are respectively used for controlling the primary side switch and the auxiliary switch and converting the input power supply to generate the output power supply, wherein the auxiliary switch and the primary side switch are not complementarily switched; the control method comprises the following steps: and controlling the auxiliary switch to be conducted for a first auxiliary conducting time according to an estimated conducting time of the parasitic diode in a primary side non-conducting period of the primary side switch, wherein the first auxiliary conducting time is approximately equal to and overlaps the estimated conducting time.
In a preferred embodiment, the control method further comprises the following steps: and controlling the auxiliary switch to be conducted for a second auxiliary conducting time after the first auxiliary conducting time in the primary side non-conducting time period.
In a preferred embodiment, the second auxiliary on-time is determined according to at least one of the following: a current-related signal, the input voltage and the output voltage; wherein the current-related signal is related to at least one of: the output current, the on-current of the primary side switch, and the current of the primary side winding.
In a preferred embodiment, the control method further comprises the following steps: the first auxiliary conducting time and the second auxiliary conducting time are not overlapped, and the auxiliary switch is controlled to be not conducted between the first auxiliary conducting time and the second auxiliary conducting time.
In a preferred embodiment, the control method further comprises the following steps: the first auxiliary conduction time is adjusted to make the first auxiliary conduction time length and the second auxiliary conduction time length approximately the same.
In a preferred embodiment, the control method further comprises the following steps: the first auxiliary conduction time is controlled to start at substantially the same time as the primary-side non-conduction period, and the second auxiliary conduction time is controlled to end at substantially the same time as the primary-side non-conduction period.
In a preferred embodiment, the control method further comprises the following steps: when the current of the auxiliary switch is substantially 0, the auxiliary switch is controlled to be non-conductive.
In a preferred embodiment, the control method further comprises the following steps: and controlling the primary side conduction time of the primary side switch in a feedback mode according to the output power supply.
The purpose, technical content, features and effects of the invention will be more easily understood through the following detailed description of specific embodiments.
Drawings
FIG. 1 is a schematic diagram of a prior art flyback power converter circuit with active clamp;
FIGS. 2A and 2B are waveform diagrams illustrating a flyback power converter with active clamp according to the prior art;
FIG. 3 is a schematic diagram of a flyback power converter with active clamp according to an embodiment of the present invention;
fig. 4 shows a waveform diagram corresponding to the embodiment of fig. 3.
Description of the symbols in the drawings
1, 3 flyback power conversion circuit
10 Transformer
20 clamping circuit
30 switching control circuit
31 power switch control circuit
32 auxiliary switch control circuit
Coss parasitic capacitance
Cr auxiliary capacitor
D2 parasitic diode
IIN input current
Im excitation current
IOUT output current
IP primary side winding current
ISEN current-dependent signal
Lr leakage inductance
Lm exciting inductance
n winding ratio
OUT output node
S1 Primary side switch
S1C Primary side switch control Signal
S2 auxiliary switch
S2C auxiliary switch control signal
Td auxiliary dead time
TONA on time
TOD2 on time
Time of non-conduction of TOFF1
On time of TON2, TON2
VI input voltage
VO output voltage
W1 primary winding
W2 Secondary winding
Detailed Description
The drawings in the present disclosure are schematic and are intended to show the coupling relationship between circuits and the relationship between signal waveforms, and the circuits, signal waveforms and frequencies are not drawn to scale.
Referring to fig. 3, there is shown an embodiment of a flyback power converter circuit with active clamping (flyback power converter circuit 3) according to the present invention, in which the flyback power converter circuit 3 includes a transformer 10, a primary-side switch S1, a clamping circuit 20, and a conversion control circuit 30. The transformer 10 includes a primary winding W1 coupled to an input power source, and a secondary winding W2 coupled to an output node OUT, wherein the input power source includes an input voltage VI and an input current IIN. The primary switch S1 is coupled to the primary winding W1 for switching the primary winding W1 to convert the input power, so that the secondary winding W2 generates an output power at an output node OUT to supply the load 40, wherein the output power includes an output voltage VO and an output current IOUT.
With continued reference to fig. 3, the clamping circuit 20 includes an auxiliary switch S2 and an auxiliary capacitor Cr connected in series with the auxiliary switch S2 to form an auxiliary branch, which is connected in parallel with the primary winding W1. The conversion control circuit 30 includes a power switch control circuit 31 and an auxiliary switch control circuit 32, wherein the power switch control circuit 31 is configured to generate a primary side switch control signal S1C according to a primary side feedback or a secondary side feedback manner, and the auxiliary switch control circuit 32 is configured to generate an auxiliary switch control signal S2C for controlling the primary side switch S1 and the auxiliary switch S2, respectively, to convert an input power to generate an output power.
Referring to fig. 3, the auxiliary switch S2 has a parasitic diode D2, wherein the auxiliary switch control circuit 32 controls the auxiliary switch S2 to turn on for a first auxiliary on-time TON2 according to the estimated on-time of the parasitic diode D2 during the primary off-time TOFF1 of the primary switch S1, wherein the first auxiliary on-time TON2 is substantially equal to and overlaps the estimated on-time of the parasitic diode D2, so as to effectively eliminate the Qrr effect of the parasitic diode D2 or reduce the extra power loss caused by the forward voltage of the parasitic diode D2.
It should be noted that: although it is desired that the first auxiliary turn-on time TON2 is exactly equal to and overlaps the estimated turn-on time of the parasitic diode D2, the actual first auxiliary turn-on time TON2 may not exactly equal to and overlap the estimated turn-on time of the parasitic diode D2 due to the inherent error of the circuit components, the matching between the components, or the delay in signal propagation, and thus has an acceptable error, i.e., "substantially", as mentioned above.
Referring to fig. 3, in an embodiment, the auxiliary switch control circuit 32 controls the auxiliary switch S2 to conduct another time during another time period (a second auxiliary conducting time TON 2') when the primary switch S1 is not conducting, so that the energy stored when the leakage inductance Lr and/or the magnetizing inductance Lm of the primary winding W1 is conducting on the primary switch S1 can be discharged through the auxiliary branch and stored in the auxiliary capacitor Cr, and the parasitic capacitance Coss of the primary switch S1 can be discharged by the energy stored in the auxiliary capacitor Cr before the primary switch S1 is conducting, in an embodiment, the conduction of the auxiliary switch S2 can make the primary switch S1 conducting as zero-voltage switching.
In one embodiment, the auxiliary switch control circuit 32 adjusts the on-time TON 2' of the auxiliary switch S2 according to at least one of: a current-dependent signal ISEN, an input voltage VI and an output voltage VO; in an embodiment, according to the adjustment of the above parameters, when the primary-side switch S1 is turned on, the voltage difference (e.g., VDS1 in the figure) between the current input terminal LX and the current output terminal (coupled to the primary-side ground point in the embodiment) is substantially 0, thereby achieving zero-voltage switching; wherein the current-related signal ISEN is related to at least one of: the output current IOUT, the on-current IDS1 of the primary-side switch, and the current IP of the primary-side winding W1; in one embodiment, the current-related signal ISEN can be obtained by sensing the VDS1 of the primary-side switch S1, the on-current IDS1 of the primary-side switch S1, or the voltage across the current-sensing resistor.
Referring to fig. 4, a waveform diagram corresponding to the embodiment of fig. 3 is shown, in which in one embodiment, the first auxiliary on-time TON2 starts immediately after the on-time of the primary switch S1 is over, i.e., the first auxiliary on-time TON2 starts substantially simultaneously with the primary off-time TOFF 1. In one embodiment, the auxiliary switch control circuit 32 controls the auxiliary switch S2 to turn on the second auxiliary on-time TON2 'just before the primary switch S1 turns on, i.e., the second auxiliary on-time TON 2' ends substantially at the same time as the primary off-time. In this embodiment, in the primary-side off-period TOFF1, the first auxiliary on-time TON2 precedes the second auxiliary on-time TON 2'. In addition, in one implementation, a dead time (dead time) Td may be provided between the turning on of the primary-side switch S1 and the first turning on or the second turning on of the auxiliary switch S2 to ensure that the primary-side switch S1 and the auxiliary switch S2 are not turned on simultaneously to cause a short-circuit current.
Referring to fig. 4, in an embodiment, the first auxiliary on-time TON2 and the second auxiliary on-time TON2 'do not overlap, and the auxiliary switch S2 is turned off between the first auxiliary on-time TON2 and the second auxiliary on-time TON 2', so as to reduce the circulating current. Of course, in other embodiments, the first auxiliary on-time TON2 and the second auxiliary on-time TON 2' may also overlap, especially when, for example, but not limited to, the frequency is high, or the primary-side off-time period TOFF1 is short; it is consistent with the spirit of the present invention as long as the first auxiliary on-time TON2 is determined according to the estimated on-time of the parasitic diode D2. In addition, due to the conservation of charge, the estimated on-time duration of the parasitic diode D2 is substantially equal to the second auxiliary on-time TON2 ', and therefore, in an embodiment of the present invention, the auxiliary switch control circuit 32 adjusts the first auxiliary on-time TON2 such that the length of the first auxiliary on-time TON2 is substantially equal to the length of the second auxiliary on-time TON 2', so that the first auxiliary on-time TON2 is substantially equal to and overlaps the estimated on-time duration of the parasitic diode D2, thereby effectively eliminating the Qrr effect of the parasitic diode D2 or reducing the extra power loss caused by the forward voltage of the parasitic diode D2. In addition, in one embodiment, when the current of the auxiliary switch S2 is substantially 0, the auxiliary switch control circuit 32 controls the auxiliary switch S2 to be non-conductive, thereby ensuring that the circulating current is reduced.
Referring still to fig. 4, from another perspective, in a preferred embodiment, after the primary-side switch S1 is turned off, the auxiliary switch control circuit 32 controls the auxiliary switch S2 to turn off after the first auxiliary on-time TON2 and the first auxiliary on-time TON2, then, before the primary switch S1 turns on, the auxiliary switch S2 is controlled to turn on for a second time (corresponding to a second auxiliary on-time TON 2'), and the first auxiliary on-time TON2 is adjusted such that the length of the first auxiliary on-time TON2 is substantially the same as the length of the second auxiliary on-time TON 2', it should be noted that, during the TON2 period, the auxiliary capacitor current ICr is turned on by the auxiliary switch S2, instead of the parasitic diode D2, the Qrr effect of the parasitic diode D2 can be effectively eliminated, or the extra power loss caused by the forward voltage of the parasitic diode D2 can be reduced.
The present invention has been described with respect to the preferred embodiments, but the above description is only for the purpose of making the content of the present invention easy to understand for those skilled in the art, and is not intended to limit the scope of the present invention. The various embodiments described are not limited to single use, but may be used in combination; for example, the combination of "conducting twice in a primary non-conducting period" and "the first and second auxiliary conducting time" and "controlling the auxiliary switch to be non-conducting when the auxiliary switch current is substantially 0" can be used. Also, various equivalent modifications and various combinations may occur to those skilled in the art, within the same spirit of the invention. For example, the first auxiliary on-time TON2 is adjusted such that the length of the first auxiliary on-time TON2 is substantially the same as the length of the second auxiliary on-time TON2 ', wherein the length of the second auxiliary on-time TON2 ' is not limited to the determination manner in the foregoing embodiments of the present application, and in other embodiments, the second auxiliary on-time may be a fixed on-time as in the prior art, as long as the length of the first auxiliary on-time TON2 is substantially the same as the length of the second auxiliary on-time TON2 ', which is in accordance with the spirit of the present invention. For example, the phrase "performing a process or an operation or generating an output result based on a signal" in the present invention is not limited to the signal itself, and includes, if necessary, performing a voltage-to-current conversion, a current-to-voltage conversion, and/or a ratio conversion on the signal, and then performing a process or an operation based on the converted signal to generate an output result. It is understood that equivalent variations and combinations, not necessarily all illustrated, will occur to those of skill in the art, which combinations are not necessarily intended to be limiting. Accordingly, the scope of the present invention should be determined to encompass all such equivalent variations as described above.
Claims (20)
1. A flyback power converter circuit, comprising:
a transformer including a primary winding coupled to an input power source and a secondary winding coupled to an output node;
a primary side switch coupled to the primary side winding for switching the primary side winding to convert the input power, so that the secondary side winding generates an output power at the output node;
a clamping circuit, comprising:
an auxiliary switch including a parasitic diode; and
an auxiliary capacitor connected in series with the auxiliary switch to form an auxiliary branch, and the auxiliary branch is connected in parallel with the primary winding; and
a conversion control circuit for controlling the primary side switch and the auxiliary switch to convert the input power to generate the output power, wherein the auxiliary switch and the primary side switch are not complementarily switched; the conversion control circuit includes:
a power switch control circuit for generating a primary side switch control signal to control the primary side switch; and
an auxiliary switch control circuit for generating an auxiliary switch control signal to control the auxiliary switch to conduct a first auxiliary conduction time according to an estimated conduction time of the parasitic diode in a primary side non-conduction period of the primary side switch, wherein the first auxiliary conduction time is equal to and overlaps the estimated conduction time, and the auxiliary switch is further controlled to conduct a second auxiliary conduction time after the first auxiliary conduction time in the primary side non-conduction period, wherein the first auxiliary conduction time and the second auxiliary conduction time are not overlapped and are not adjacent.
2. The flyback power converter circuit of claim 1, wherein the auxiliary switch control circuit determines the second auxiliary on-time based on at least one of: a current-related signal, an input voltage of the input power supply and an output voltage of the output power supply; wherein the current-related signal is related to at least one of: an output current of the output power source, the conduction current of the primary side switch, and the current of the primary side winding.
3. The flyback power converter circuit of claim 1, wherein the auxiliary switch control circuit further adjusts the first auxiliary on-time such that the first auxiliary on-time is the same as the second auxiliary on-time.
4. The flyback power converter circuit of claim 1, wherein the auxiliary switch control circuit further controls the first auxiliary on-time to start simultaneously with the primary-side off-time period and the second auxiliary on-time to end simultaneously with the primary-side off-time period.
5. The flyback power converter circuit of claim 1, wherein the auxiliary switch is controlled to be non-conductive when the auxiliary switch current is 0.
6. The flyback power converter circuit of claim 1, wherein the power switch control circuit feedback-controls a primary on-time of the primary switch according to the output power.
7. A conversion control circuit is used for controlling a flyback power conversion circuit, and the flyback power conversion circuit comprises: a transformer including a primary winding coupled to an input power source and a secondary winding coupled to an output node; a primary side switch coupled to the primary side winding for switching the primary side winding to convert the input power, so that the secondary side winding generates an output power at the output node; and a clamping circuit, comprising: an auxiliary switch including a parasitic diode; and an auxiliary capacitor connected in series with the auxiliary switch to form an auxiliary branch, and the auxiliary branch is connected in parallel with the primary winding; the conversion control circuit is used for controlling the primary side switch and the auxiliary switch to convert the input power supply to generate the output power supply, wherein the auxiliary switch and the primary side switch are not complementarily switched; the conversion control circuit includes:
a power switch control circuit for generating a primary side switch control signal to control the primary side switch; and
an auxiliary switch control circuit for generating an auxiliary switch control signal to control the auxiliary switch to conduct a first auxiliary conduction time according to an estimated conduction time of the parasitic diode in a primary side non-conduction period of the primary side switch, wherein the first auxiliary conduction time is equal to and overlaps the estimated conduction time, and the auxiliary switch is further controlled to conduct a second auxiliary conduction time after the first auxiliary conduction time in the primary side non-conduction period, wherein the first auxiliary conduction time and the second auxiliary conduction time are not overlapped and are not adjacent.
8. The conversion control circuit of claim 7, wherein the auxiliary switch control circuit determines the second auxiliary on-time based on at least one of: a current-related signal, an input voltage of the input power supply and an output voltage of the output power supply; wherein the current-related signal is related to at least one of: an output current of the output power source, the conduction current of the primary side switch, and the current of the primary side winding.
9. The conversion control circuit of claim 7, wherein the first auxiliary conduction time and the second auxiliary conduction time do not overlap, and the auxiliary switch is non-conductive between the first auxiliary conduction time and the second auxiliary conduction time.
10. The conversion control circuit of claim 7, wherein the auxiliary switch control circuit further adjusts the first auxiliary turn-on time such that the first auxiliary turn-on time is the same as the second auxiliary turn-on time.
11. The conversion control circuit of claim 7, wherein the auxiliary switch control circuit further controls the first auxiliary conduction time and the primary-side non-conduction time period to start at the same time, and the second auxiliary conduction time and the primary-side non-conduction time period to end at the same time.
12. A conversion control circuit as claimed in claim 7, wherein the auxiliary switch is controlled to be non-conductive when the auxiliary switch current is 0.
13. The conversion control circuit of claim 7, wherein the power switch control circuit feedback-controls a primary-side on-time of the primary-side switch according to the output power.
14. A control method for a flyback power converter circuit, the flyback power converter circuit comprising: a transformer including a primary winding coupled to an input power source and a secondary winding coupled to an output node; a primary side switch coupled to the primary side winding for switching the primary side winding to convert the input power, so that the secondary side winding generates an output power at the output node; and a clamping circuit, comprising: an auxiliary switch including a parasitic diode; and an auxiliary capacitor connected in series with the auxiliary switch to form an auxiliary branch, and the auxiliary branch is connected in parallel with the primary winding; the control method comprises the following steps:
controlling the primary side switch and the auxiliary switch to convert the input power to generate the output power, wherein the auxiliary switch and the primary side switch are not complementarily switched; and
and controlling the auxiliary switch to be conducted for a first auxiliary conduction time according to an estimated conduction time of the parasitic diode in a primary side non-conduction time period of the primary side switch, wherein the first auxiliary conduction time is equal to and overlaps the estimated conduction time, and controlling the auxiliary switch to be conducted for a second auxiliary conduction time after the first auxiliary conduction time in the primary side non-conduction time period, wherein the first auxiliary conduction time and the second auxiliary conduction time are not overlapped and are not adjacent.
15. The control method of claim 14, wherein the second auxiliary on-time is determined according to at least one of: a current-related signal, an input voltage of the input power supply and an output voltage of the output power supply; wherein the current-related signal is related to at least one of: an output current of the output power source, the conduction current of the primary side switch, and the current of the primary side winding.
16. The control method according to claim 14, further comprising the steps of: the first auxiliary conducting time and the second auxiliary conducting time are not overlapped, and the auxiliary switch is controlled to be not conducted between the first auxiliary conducting time and the second auxiliary conducting time.
17. The control method according to claim 14, further comprising the steps of: and adjusting the first auxiliary conduction time to ensure that the length of the first auxiliary conduction time is the same as that of the second auxiliary conduction time.
18. The control method according to claim 14, further comprising the steps of: and controlling the first auxiliary conduction time and the primary side non-conduction time period to start at the same time, and controlling the second auxiliary conduction time and the primary side non-conduction time period to end at the same time.
19. The control method according to claim 14, further comprising the steps of: when the auxiliary switch current is 0, the auxiliary switch is controlled to be non-conductive.
20. The control method according to claim 14, further comprising the steps of: and controlling the primary side conduction time of the primary side switch in a feedback mode according to the output power supply.
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| US11088624B2 (en) * | 2019-07-30 | 2021-08-10 | Power Forest Technology Corporation | Voltage conversion apparatus for implementing zero-voltage switching based on recovering leakage inductance energy |
| TWI729807B (en) * | 2019-11-11 | 2021-06-01 | 立錡科技股份有限公司 | Flyback power converter and active clamp snubber and overcharging protection circuit thereof |
| US11336185B2 (en) | 2020-05-11 | 2022-05-17 | Alpha And Omega Semiconductor International Lp | Flyback converter, control circuit thereof, and associated control method |
| TWI741596B (en) * | 2020-05-11 | 2021-10-01 | 加拿大商萬國半導體國際有限合夥公司 | Flyback converter, control circuit thereof, and associated control method |
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| US9276483B2 (en) * | 2013-06-27 | 2016-03-01 | System General Corporation | Control circuit for active-clamp flyback power converter with programmable switching period |
| CN107181410A (en) * | 2016-03-12 | 2017-09-19 | 快捷韩国半导体有限公司 | Active clamp flyback converter |
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2017
- 2017-10-26 CN CN201711017765.6A patent/CN109713904B/en active Active
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| US5570278A (en) * | 1994-02-25 | 1996-10-29 | Astec International, Ltd. | Clamped continuous flyback power converter |
| TW201014140A (en) * | 2008-09-17 | 2010-04-01 | Delta Electronics Inc | Forward-flyback converter with active-clamp circuit |
| CN102307017A (en) * | 2011-09-16 | 2012-01-04 | 浙江大学 | Control method applied to active-clamp flyback miniature photovoltaic grid-connected inverter device |
| US9276483B2 (en) * | 2013-06-27 | 2016-03-01 | System General Corporation | Control circuit for active-clamp flyback power converter with programmable switching period |
| CN107181410A (en) * | 2016-03-12 | 2017-09-19 | 快捷韩国半导体有限公司 | Active clamp flyback converter |
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| CN109713904A (en) | 2019-05-03 |
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