CN112491258B - Clamping circuit of active clamping flyback converter and control method thereof - Google Patents

Clamping circuit of active clamping flyback converter and control method thereof Download PDF

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Publication number
CN112491258B
CN112491258B CN202011311811.5A CN202011311811A CN112491258B CN 112491258 B CN112491258 B CN 112491258B CN 202011311811 A CN202011311811 A CN 202011311811A CN 112491258 B CN112491258 B CN 112491258B
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clamping
switch tube
tube
clamp
voltage
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CN112491258A (en
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王海洲
袁源
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Mornsun Guangzhou Science and Technology Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/3353—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter

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  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a clamping circuit of an active clamping flyback converter and a control method thereof.A switching unit with good reverse recovery characteristic is connected in series in a clamping capacitor discharge loop, when a main switching tube is turned off, after a resonant current is reduced to zero, the resonant current can be turned off only by generating a little negative current switching unit, so that the energy stored on the clamping capacitor is prevented from being released accidentally during the turn-off period of the main switching tube, the problem of resonance period change caused by reverse recovery of the clamping switching tube is solved, the efficiency of the flyback converter is improved, and the EMI of the flyback converter is improved.

Description

Clamping circuit of active clamping flyback converter and control method thereof
Technical Field
The invention relates to the field of switch converters, in particular to a clamping circuit of an active clamping flyback converter and a control method thereof.
Background
The flyback converter is widely applied to medium and small power switching power supplies due to the advantages of low cost, simple topology and the like. In the actual working process, the energy of the primary side of the flyback converter cannot be completely transmitted to the secondary side due to the existence of the leakage inductance, and the resonance between the leakage inductance energy of the primary side and the MOS tube junction capacitor causes the drain electrode of the main switching tube to generate a high-frequency voltage peak. In order to reduce the voltage stress of the switch tube when the product is manufactured, it is a common practice to add an appropriate snubber circuit, and the common snubber circuit includes an RCD snubber circuit, an LCD snubber circuit, and an active clamp circuit. The active clamping circuit is additionally provided with an additional clamping switch tube and a larger clamping capacitor, so that leakage inductance energy can be stored in the clamping capacitor, and the energy is recycled to the input end of the converter. In addition, due to the electric inertia of the leakage inductance, the active clamping circuit extracts the charges on a termination capacitor at the drain end of the main switching tube through reverse exciting current after the recovery process of the leakage inductance energy is finished, so that the drain voltage of the main switching tube is reduced to zero, zero voltage switching-on (ZVS) of the main switching tube is realized, the switching-on loss of the main switching tube is reduced, and the power density of a product is further improved.
As shown in fig. 1, 100 is a circuit diagram of a typical active clamp flyback converter. In the figure, LK is leakage inductance, LM is excitation inductance, C _ CLAMP is clamping capacitor, S2 is clamping switch tube, S1 is main switch tube, COSSIs a main switch junction capacitor, RCS is an excitation inductance current sampling resistor, NP is the number of turns of a primary winding of the transformer, NS is the number of turns of a secondary winding of the transformer, DR is a rectifier diode and COUTIs the converter output capacitance, unit 120 is the controller of the converter (i.e. is the main control chip of the converter), and unit 130 is the isolated feedback circuit. The main control chip realizes double-loop peak current mode control by sampling the voltage drop of the converter output voltage and the current sampling resistor RS, and determines when the main switch tube S1 is switched on,When to turn off. In order to realize ZVS switching-on of the main switching tube S1, the time for conducting the clamping switching tube S2 needs to be reasonably controlled. In fact, it is difficult to pull the voltage at the switching node to ground potential by means of leakage inductance alone, and the inductance of the magnetizing inductor LM needs to be reduced appropriately so that there is also a negative current in the magnetizing inductor. After the clamping switch tube is closed, the excitation inductor and the leakage inductor still flow negative current, energy is extracted from the junction capacitor of the switch tube, and the voltage of the switch node is pulled to the ground potential.
Although the active clamp flyback can realize ZVS of the main switching tube, when the converter operates in the discontinuous mode, the driving signals of the clamp switching tube and the main switching tube are non-complementary, that is, the clamp switching tube is turned on only for a short time before the main switching tube is turned on, and the timing diagram is shown in fig. 2. Fig. 2 is a timing waveform under an ideal condition, and under a non-complementary flyback active clamp in a discontinuous mode, clamp switching tubes are turned on at different resonance positions, and due to different magnitudes and directions of excitation currents, the degree of achieving ZVS of a main switching tube is different. If the clamping switch tube is conducted at the trough of the main switch tube Vds, the conducting voltage of the clamping switch tube is very high, and the loss is also very large; in order to reduce the switching loss of the clamping switch tube and reduce EMI noise interference on the premise of ensuring the ZVS of the main switch tube as far as possible, the quasi-resonance is adopted to control the conduction of the clamping switch tube, the moment that the voltage of the main switch tube is Vin is indirectly detected by detecting the voltage of the auxiliary winding, and the conduction of the clamping switch tube is realized when the voltage of the Vds of the main switch tube is equal to or close to a wave peak after a fixed time delay, so that the optimal effects of efficiency and EMI are achieved.
Under normal conditions, after the main switch tube is turned off, the transformer transmits energy to the secondary side, the leakage current ILk charges the output junction capacitor Coss1 of the main switch tube, and the output junction capacitor Coss2 of the clamping switch tube discharges, as shown in the stage T1-T2 in FIG. 2; after the output junction capacitor Coss2 of the clamp switching tube is discharged, the body diode is conducted, the leakage inductance resonates with the clamp capacitor, and Vds almost remains unchanged because the excitation winding is clamped by the secondary side at the moment, as shown in the stage T2-T3 in FIG. 2; after Ilk resonates to zero, the diode of the clamping switch body is cut off, and Vds is formed by Vin + Vc (clamp capacitor voltage drop) falls to Vin + NVo, and at this time, the leakage inductance resonates with both the main switching tube output junction capacitor Coss1 and the clamp switching tube output junction capacitor Coss2, as shown in the stage from T3 to T4 in fig. 2; after the excitation current linearly drops to zero, the excitation inductor is separated from the secondary side clamp, and resonates with the leakage inductor together with the output junction capacitor Coss1 of the main switching tube and the output junction capacitor Coss2 of the clamp switching tube (ignoring the parasitic capacitance of the transformer), and the resonant period of the main switching tube Vds is at the moment
Figure BDA0002790062140000021
Then, in the active clamping operation mode, the clamping switch tube is turned on by QR, as shown in the stage from T4 to T5 in fig. 2; the excitation inductor is clamped by the secondary side again, Vds is immediately raised to Vin + Vc, Ilk is reversely excited until the maximum value is reached when the clamping switch tube is turned off, and then ILk resonance is reduced and main switch tube junction capacitance Coss1 is discharged to prepare for a main switch tube ZVS, as shown in the stage from T5 to T7 in fig. 2; when Ilk is reduced to be equal to the exciting current, the secondary side is cut off, the secondary side and the exciting current are kept equal and are continuously reduced, in order to ensure that the main switching tube realizes ZVS, the main switching tube is turned on again before the secondary side and the main switching tube are reversed, and a complete period is finished at the stage from T7 to T9 shown in FIG. 2.
The actual test waveform is shown in fig. 3, where Vds1 is the voltage across the drain and the source of the main switch tube, and Ilk is the resonant current waveform. It can be seen from the actual measurement test waveform that, after the driving of the main switching tube is turned off, the leakage inductance and the clamping capacitor start to resonate through the body diode of the clamping switching tube, because the reverse recovery characteristic of the body diode is poor, after the resonant current passes through zero, the resonant capacitor discharges negative current due to the reverse recovery of the body diode, and the charge of the capacitor at the end of the main switching tube is extracted, so that the voltage of the main switching tube Vds1 is reduced, after the reverse recovery of the diode of the clamping switching tube is finished, the negative current immediately reaches zero, at the moment, the Vds voltage of the main switching tube starts to rise again, if the excitation current passes through zero in the rising process, the resonance period is changed, and finally, as a result, the clamping switching tube cannot realize QR (quasi-resonance) conduction, the temperature rise of the clamping switching tube is increased, and the efficiency of the whole converter is low.
Disclosure of Invention
In view of the defects of the prior art, an object of the present invention is to provide a clamp circuit of an active clamp flyback converter and a control method thereof, which solve the problem of resonance period change caused by reverse recovery of a clamp switch tube.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
the utility model provides an active clamp flyback converter's clamp circuit, includes clamp capacitance and clamp switch tube, its characterized in that: the reverse recovery circuit also comprises a switch unit which is connected in series in the discharge loop of the clamping capacitor and has good reverse recovery characteristic, when the main switching tube is turned off, after the resonant current is reduced to zero, the resonant current can be turned off only by generating a little negative current, so that the energy stored on the clamping capacitor is prevented from being released accidentally during the turn-off period of the main switching tube.
As a specific embodiment of the clamping circuit of the active-clamping flyback converter, the switching unit is a low-voltage switching tube, the low-voltage switching tube is connected in series between the clamping capacitor and the clamping switching tube in the forward direction, the source of the low-voltage switching tube is connected to the drain of the clamping switching tube, and the drain of the low-voltage switching tube is connected to the clamping capacitor.
Preferably, in the same switching period, the low-voltage switching tube is turned on before the clamping switching tube, and the low-voltage switching tube is turned off after the clamping switching tube.
As a specific implementation manner of the clamp circuit of the active clamp flyback converter, the switch unit includes a first diode and a second diode, the first diode is connected in series between the clamp capacitor and the clamp switch tube in the forward direction, and is used for forming an inverse parallel branch between the clamp capacitor and the main switch tube, that is, an anode of the first diode is connected to the clamp capacitor, and a cathode of the first diode is connected to a drain of the clamp switch tube; the second diode is reversely connected in parallel at two ends of a series branch consisting of the first diode and the clamping switch tube, namely, the cathode of the second diode is connected with the anode of the first diode, and the anode of the second diode is connected with the source electrode of the clamping switch tube.
Preferably, the clamping switch tube is switched on at a voltage resonance trough at two ends of a drain source of the clamping switch tube.
A clamping control method of an active clamping flyback converter is characterized in that when a main switching tube is turned off, after a resonant current is reduced to zero, a switching unit can be turned off when the resonant current only generates a small amount of negative current which does not affect a resonant period, so that the phenomenon that the resonant period is changed due to the fact that energy stored on a clamping capacitor is accidentally released during the turn-off period of the main switching tube is avoided.
The switch unit is a low-voltage switch tube which is connected in series between the clamping capacitor and the clamping switch tube in the forward direction, and in the same switch period, the low-voltage switch tube is firstly switched on than the clamping switch tube and then switched off.
Compared with the prior art, the clamp circuit of the active clamp flyback converter and the control method thereof have the beneficial effects that: by connecting the switch unit with good reverse recovery characteristic in the clamp capacitor discharge loop in series, the energy stored on the clamp capacitor is prevented from being released accidentally during the turn-off of the main switch tube, the problem of resonance period change caused by reverse recovery of the clamp switch tube is solved, the efficiency of the flyback converter is improved, and the EMI of the flyback converter is improved.
Drawings
FIG. 1 is a schematic block diagram of a typical prior art ACF circuit;
fig. 2 is an ideal operating waveform diagram of a typical conventional back-porch non-complementary mode active clamp flyback converter;
fig. 3 is a waveform diagram of an actual operation test of a typical conventional back-porch non-complementary mode active clamp flyback converter;
fig. 4 is a schematic diagram of a first embodiment of a clamping circuit of the active-clamp flyback converter of the present invention;
fig. 5 is a waveform diagram of a test of the first embodiment of the clamp circuit of the active clamp flyback converter in actual operation according to the present invention;
fig. 6 is a schematic diagram of a second embodiment of a clamping circuit of the active-clamped flyback converter of the present invention;
fig. 7 shows test waveforms of the clamp circuit of the second embodiment of the active-clamp flyback converter in actual operation.
Detailed Description
First embodiment
In this embodiment, as shown in fig. 4. The active clamping flyback converter comprises a main switching tube 401, a clamping switching tube 402, a low-voltage switching tube 403, a clamping capacitor 404 and a transformer 405, wherein the drain electrode of the main switching tube 401 is connected with the source electrode of the clamping switching tube 402 and the synonym end of the primary winding of the transformer 405, the source electrode of the main switching tube 401 is grounded, the drain electrode of the clamping switching tube 402 is connected with the source electrode of the low-voltage switching tube 403, the drain electrode of the low-voltage switching tube 403 is connected with one end of the clamping capacitor 404, the other end of the clamping capacitor 404 is connected with the synonym end of the primary winding of the transformer 405, and LK is leakage inductance and Lm is excitation inductance.
In this embodiment, when the main switching tube 401 is turned off and the resonant current is reduced to zero, the problem of the change of the resonant period of the main switching tube 401 caused by the reverse recovery of the clamp switching tube 402 is solved by using the advantage of the low-voltage switching tube 403 that the body diode reverse recovery characteristic is good.
The working principle of the embodiment is as follows: when the main switching tube 401 is switched on, the main switching tube 401 positively excites the excitation inductor Lm of the transformer 405, and the excitation current linearly rises;
when the main switch tube 401 is turned off, the energy stored in the leakage inductor LK starts to resonate with the clamp capacitor 404 and charges the output junction capacitor CQ1 of the main switch tube 401, and discharges the output junction capacitors CQ2 and CQ3 of the clamp switch tube 402 and the low-voltage switch tube 403, when the voltage of the junction capacitor CQ1 of the main switch tube 401 reaches Vin + nV0, the resonant current charges the clamp capacitor 404 through the body diodes DQ2 and DQ3 of the clamp switch tube 402 and the low-voltage switch tube 403, and the transformer 405 starts to transfer energy to the secondary side, the resonant current gradually decreases, after the resonant current decreases to zero, because the reverse recovery characteristic of the low-voltage switch tube 403 is good, the low-voltage switch tube 403 is turned off when the resonant current generates only a little negative current, so that the energy stored in the clamp capacitor 404 cannot be released, at this time, because the negative current is very small, the amplitude of the drain-source voltage Vds expressed in the main switch tube 401 is not obvious, the resonance period cannot be affected.
After the current of the excitation inductor Lm crosses zero, the excitation inductor Lm and the leakage inductor LK start to resonate with the output junction capacitors of the main switch tube 401 and the clamping switch tube 402. When the resonance voltage of the clamping switch tube 402 resonates to a wave trough, the clamping switch tube 402 and the low-voltage switch tube 403 are switched on, so that the wave trough of the clamping switch tube 402 and the wave trough of the low-voltage switch tube 403 are switched on, and the switching loss is reduced, wherein the low-voltage switch tube 403 is switched on earlier than the clamping switch tube 402, and the low-voltage switch tube 403 is prevented from being damaged due to high voltage. The clamp capacitor 404 discharges through the clamp switch tube 402 and the low-voltage switch tube 403, and extracts energy on the output junction capacitor CQ1 of the main switch tube 401 to prepare for ZVS switching on in the next period. The waveform during actual test is shown in fig. 5, where Ilk is the resonant current, and Vds is the drain-source voltage of the main switch tube.
Second embodiment
In this embodiment, as shown in fig. 6. The active clamping flyback converter comprises a main switch tube 501, a clamping switch tube 502, a first diode 503, a second diode 504, a clamping capacitor 505 and a transformer 506, wherein the drain electrode of the main switch tube 501 is connected with the source electrode of the clamping switch tube 502 and the synonym end of the primary winding of the transformer 506, the source electrode of the main switch tube 501 is grounded, the drain electrode of the clamping switch tube 502 is connected with the cathode of the first diode 503, the anode of the first diode 503 is connected with one end of the clamping capacitor 505, and the other end of the clamping capacitor 505 is connected with the synonym end of the primary winding of the transformer 506; the second diode 504 is connected in reverse parallel to two ends of a series branch formed by the first diode 503 and the clamping switch tube 502, that is, the cathode of the second diode 504 is connected to the anode of the first diode 503, and the anode of the second diode 504 is connected to the source of the clamping switch tube 502, where LK is leakage inductance and Lm is excitation inductance.
In this embodiment, by using the advantage of good reverse recovery characteristics of the first diode 503 and the second diode 503, when the main switching tube 501 is turned off, and after the resonant current is reduced to zero, the problem of the change of the resonant period of the main switching tube 501 caused by the reverse recovery of the clamp switching tube 502 is solved.
The working principle of the embodiment is as follows: when the main switching tube 501 is switched on, the main switching tube 501 positively excites the excitation inductor Lm of the transformer 506, and the excitation current linearly rises;
when the main switch tube 501 is turned off, the energy stored in the drain inductor LK starts to resonate with the clamp capacitor 502, and charges the output junction capacitor CQ1 of the main switch tube 501, and discharges the output junction capacitor CQ2 of the clamp switch tube 502, when the voltage of the junction capacitor CQ1 of the main switch tube 501 reaches Vin + nV0, the transformer 506 starts to transfer energy to the secondary side, at this time, the resonant current charges the clamp capacitor 505 through the second diode 504, the resonant current gradually decreases, after the resonant current decreases to zero, because the reverse recovery characteristic of the second diode 504 is good, the second diode 504 is turned off, and the energy stored in the clamp capacitor 505 cannot be released, at this time, because the negative current is very small, the resonant amplitude of the drain-source voltage Vds of the main switch tube 501 is not obvious, and the resonant period cannot be influenced.
After the current of the excitation inductor Lm crosses zero, the excitation inductor Lm and the leakage inductor LK start to resonate with the output junction capacitors of the main switch tube 501 and the clamping switch tube 502. When the resonance voltage of the clamp switch tube 502 resonates to a wave trough, the clamp switch tube 502 is switched on, the wave trough of the clamp switch tube 502 is switched on, the switching loss is reduced, at the moment, the clamp switch tube 502 is switched on, the first diode 503 is switched on in the forward direction, the second diode 504 is switched off in the reverse bias direction, the clamp capacitor 505 discharges through the clamp switch tube 502, the energy on the junction capacitor CQ1 output by the main switch tube 501 is extracted, and preparation is made for the next-period ZVS switching-on. The waveform during actual test is shown in fig. 7, where Ilk is the resonant current and Vds is the drain-source voltage of the main switch tube.
The above embodiments are only for the understanding of the inventive concept of the present application and are not intended to limit the present invention, and any modification, equivalent replacement, improvement, etc. made by those skilled in the art without departing from the principle of the present invention should be included in the protection scope of the present invention. All technical characteristics in the invention can be interactively combined on the premise of not conflicting with each other.

Claims (5)

1. The utility model provides an active clamp flyback converter's clamp circuit, includes clamp capacitance and clamp switch tube, its characterized in that: the switch unit is a low-voltage switch tube, the low-voltage switch tube is connected in series between the clamping capacitor and the clamping switch tube in the forward direction, the source electrode of the low-voltage switch tube is connected with the drain electrode of the clamping switch tube, and the drain electrode of the low-voltage switch tube is connected with the clamping capacitor; when the main switching tube is turned off, after the resonant current is reduced to zero, the resonant current can be turned off by only generating a little negative current switching unit, so that the energy stored on the clamping capacitor is prevented from being released accidentally during the turn-off of the main switching tube.
2. The clamp circuit of an active-clamp flyback converter of claim 1, wherein: in the same switching period, the low-voltage switch tube is switched on before the clamping switch tube, and the low-voltage switch tube is switched off after the clamping switch tube.
3. The clamp circuit of an active-clamp flyback converter according to claim 1 or 2, characterized in that: the clamping switch tube is switched on at the voltage resonance wave trough at the two ends of the drain source of the clamping switch tube.
4. A clamping control method of an active clamping flyback converter is characterized in that when a main switching tube is turned off, after a resonant current is reduced to zero, a switching unit can be turned off when the resonant current only generates a small amount of negative current which does not affect a resonant period, so that the phenomenon that the resonant period is changed due to the fact that energy stored on a clamping capacitor is accidentally released in the period of turning off the main switching tube is avoided, wherein the switching unit is a low-voltage switching tube which is connected between the clamping capacitor and the clamping switching tube in series in the positive direction.
5. The clamp control method of the active-clamp flyback converter according to claim 4, characterized in that: in the same switching period, the low-voltage switch tube is switched on before the clamping switch tube, and the low-voltage switch tube is switched off after the clamping switch tube.
CN202011311811.5A 2020-11-20 2020-11-20 Clamping circuit of active clamping flyback converter and control method thereof Active CN112491258B (en)

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CN108872835B (en) * 2018-07-02 2024-02-13 广州金升阳科技有限公司 Detection circuit
CN113410994B (en) * 2021-06-24 2023-03-14 广州金升阳科技有限公司 Active clamp flyback converter and control method thereof

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US6069803A (en) * 1999-02-12 2000-05-30 Astec International Limited Offset resonance zero volt switching flyback converter
CN100550587C (en) * 2007-08-14 2009-10-14 伊博电源（杭州）有限公司 The synchronous rectification of the variable turn ratio or diode rectification converter
TWI358188B (en) * 2008-09-17 2012-02-11 Delta Electronics Inc Forward-flyback converter with active-clamp circui
CN103795260B (en) * 2014-01-21 2016-01-20 广州金升阳科技有限公司 A kind of incomplementarity flyback active clamp converter
CN107222108A (en) * 2017-06-09 2017-09-29 金陵科技学院 A kind of active-clamp DC converter and its control method
IT201900006000A1 (en) * 2019-04-17 2020-10-17 St Microelectronics Srl A PROCEDURE FOR OPERATING A FLYBACK CONVERTER WITH AN ACTIVE CLAMP, CORRESPONDING CONTROL CIRCUIT AND FLYBACK CONVERTER
CN111030462B (en) * 2019-08-26 2021-06-04 广州金升阳科技有限公司 Active clamp flyback converter and control method

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