CN102122890B - Control method for auxiliary switching tube of active clamp flyback converter - Google Patents

Control method for auxiliary switching tube of active clamp flyback converter Download PDF

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Publication number
CN102122890B
CN102122890B CN201010502461.0A CN201010502461A CN102122890B CN 102122890 B CN102122890 B CN 102122890B CN 201010502461 A CN201010502461 A CN 201010502461A CN 102122890 B CN102122890 B CN 102122890B
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CN
China
Prior art keywords
voltage
switching tube
auxiliary switch
resistance
clamp
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CN201010502461.0A
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Chinese (zh)
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CN102122890A (en
Inventor
刘硕
倪建军
张方华
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南京航空航天大学
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Publication of CN102122890A publication Critical patent/CN102122890A/en
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Abstract

The invention relates to a control method for an auxiliary switching tube of an active clamp flyback converter. In the flyback converter, severe energy loss and voltage spike of a main switching tube are caused due to leakage inductance of a transformer and leakage inductance of circuits. The conventional solution mainly comprises methods for solving the problems by using residual current device (RCD) clamp, liquid crystal display (LCD) clamp and active clamp, wherein an active clamp circuit can effectively recover leakage inductance energy and obviously improve the efficiency. The invention provides a novel control method on the basis of the conventional active clamp flyback converter topology. In the conventional control method, a primary side switching tube is in complementary conduction with an auxiliary switching tube in each period; and in the control method, the primary side switching tube is switched on in each period, the auxiliary switching tube is controlled by setting voltage of a clamp capacitor in the clamp circuit, and when the voltage of the clamp capacitor reaches the set value, the auxiliary switching tube is switched on. Compared with the prior art, the method has the advantages that: the switching loss of the auxiliary switching tube can be reduced; and more importantly, the efficiency of the circuit can be greatly improved under a light load, and the no-load loss is reduced.

Description

A kind of control method of auxiliary switching tube of active clamp flyback converter
Technical field
The present invention relates to the controlling party converters owned by France of auxiliary switching tube of active clamp flyback converter.
Background technology
The traditional control method that flyback converter leakage inductance reclaims has three kinds below:
1:RCD clamp circuit
RCD clamp circuit structure is the simplest, and cost is minimum, be easy to realize, but the energy in leakage inductance all consumes in buffer resistance, has reduced the efficiency of converter, and it is applicable to and the cost strict occasion controlled less demanding to efficiency.
2:LCD clamp circuit
LCD clamp circuit can be realized the leakage inductance energy feedback of passive and nondestructive, but need outer coilloading, parameter tuning is more difficult, but larger LC resonance current has increased the conduction loss of power switch during high frequency, is generally applicable to the occasion of switching frequency not too high (as tens kHz)
3: active clamp circuit
Active clamp circuit has increased an electric capacity and auxiliary switch, and traditional active clamp control method, in one-period, main switch and and the complementary conducting of auxiliary switch, can realize leakage inductance energy feedback, realize the soft switch of main switch and auxiliary switch, can realize high frequency conversion.Although at full load, traditional active clamp flyback control circuit efficiency is very high, when underloading, efficiency is still not high.
Summary of the invention
The object of the invention is to the defect existing for above-mentioned prior art, develop and a kind ofly can overcome now defectively, efficiency is not high, inverse-excitation type direct current-stream power supply change-over device that particularly light-load efficiency is not high.
Inverse-excitation type direct current-stream power supply change-over device of realizing above-mentioned purpose is comprised of inverse-excitation type main circuit and active clamp circuit.Circuit of reversed excitation comprises an input port, one or more transformers, and former limit switching tube, secondary rectifier diode, filter capacitor and an output port form.When switching tube conducting, rectifier diode cut-off, the energy of power supply input is stored in transformer with the form of magnetic energy, and when switching tube ends, the Energy Transfer storing in transformer is to load.Active clamp circuit comprises an auxiliary switch, a parasitic diode and an Absorption Capacitance.Wherein parasitic diode is the inverse parallel body diode of auxiliary switch parasitism.Auxiliary switch and the Absorption Capacitance composition auxiliary circuit that is in series.Auxiliary branch is connected in parallel on transformer primary side winding two ends or the switching tube two ends, former limit in parallel of circuit of reversed excitation.Each cycle of former limit switching tube is open-minded, and auxiliary switch is just open-minded every several cycles.
In control circuit, the production method of the control signal of auxiliary switch S2 is for (take voltage threshold circuit 2 as example, as Fig. 2): when the voltage in clamp capacitor Cr runs up to a certain value, the voltage Vr obtaining by divider resistance R1 and R2 also can rise to a certain value, this value is by the reference voltage V ref comparison with artificial setting, when voltage Vr is less than reference voltage V ref, low level of comparator output is to reset terminal R, now Q ' keeps low level always, auxiliary switch S2 in off state, clamp capacitor Cr is in charged state, charging can continue one-period or several cycle.When clamp capacitor Cr is charged to a certain degree, voltage Vr can be greater than reference voltage V ref, a high level of now comparator output is to reset terminal R, now drive signal Vpulse in low level state, Q ' can export a high level, thereby can make auxiliary switch S2 open-minded, property list by SR latch can be found out, as long as set end S is low level state, Q ' can export a high level always, makes auxiliary switch S2 always open-minded.Because the clamp capacitor Cr velocity of discharge is very fast, comparator can be exported a low level very soon, so the service time of auxiliary switch S2 can be by driving signal Vpulse to set.After clamp capacitor Cr has discharged, can set and drive signal Vpulse high level, auxiliary switch S2 turn-offs immediately.Note, open-minded in the time of for fear of S1 and S2 two pipe, drive signal Vpulse high level just to arrange before arriving at the signal of opening of former limit switching tube S1.
The control method of active clamp anti exciting converter of the present invention, has following advantages, and leakage inductance energy has obtained recovery, and the Energy Transfer of leakage inductance, to output, is realized in the cycle of opening at auxiliary switch simultaneously, the soft switch of former limit switch; By controlling opening and turn-offing of auxiliary switch, can reduce the on-off times of auxiliary switch, reduced the switching loss of auxiliary switch, can greatly improve the efficiency of circuit under underloading, reduce no-load loss.
Accompanying drawing explanation
The anti exciting converter schematic diagram of the control method of the active clamp auxiliary switch that the first that Fig. 1 this patent proposes is new.In figure shown in dotted line frame is voltage threshold control circuit 1.
The anti exciting converter schematic diagram of the control method of the active clamp auxiliary switch that the second that Fig. 2 this patent proposes is new.In figure shown in dotted line frame is voltage threshold control circuit 2.
The active clamp auxiliary switch control method of Fig. 3 based on voltage threshold control circuit 2, the gate pulse of anti exciting converter main switch and auxiliary switch and work wave.
The anti exciting converter work schematic diagram of the new control method of the active clamp auxiliary switch based on voltage threshold control circuit 2 that Fig. 4 this patent proposes.Work schematic diagram when figure (a) opens for main switch S1; Figure (b) is that main open pipe S1 closes the schematic diagram of having no progeny to parasitic capacitance C1 charging; Figure (c) is that leakage inductance energy is to the schematic diagram of clamp capacitor Cr charging; When the voltage that figure (d) is got by resistance for clamp capacitor Cr reaches fiducial value, auxiliary switch S2 is open-minded, the schematic diagram of clamp capacitor Cr electric discharge
Embodiment
(1) in conjunction with Fig. 3, constantly, auxiliary switch S2 is turned off t0, and former limit switching tube S1 and auxiliary switch S2 are simultaneously in off state.T 1former limit switching tube S1 conducting constantly, primary current rises, transformer storage power, auxiliary switch S2 and output rectifier diode D cut-off.Magnetizing inductance Lm and leakage inductance Lr linear-charging.Clamp capacitor Cr constant in energy, both end voltage also remains unchanged.
(2) t 2constantly, the switching tube S1 conducting of former limit is turned off, and resonant inductance electric current is with resonance manner to parasitic capacitance C1 charging, and due to magnetizing inductance, Lm is larger, and former limit switching tube S1 drain-source both end voltage Vds approximately linear rises.
(3) t 3constantly, Vds rises to Vi+Vc, and now the energy in leakage inductance Lr stores in clamp capacitor Cr by the body diode of auxiliary switch S2.The voltage linear at clamp capacitor Cr two ends rises.
(4) t 4constantly, the energy in leakage inductance Lr is all absorbed by clamp capacitor Cr, and the voltage at Cr two ends rises to a stable value, is less than the voltage threshold of setting, remains unchanged.Primary current Ip drops to zero.The energy of magnetizing inductance Lm storage is released to outlet side, and Ilm is linear to decline, output rectifier diode D conducting.
(5) t 5constantly, if the energy that clamp capacitor Cr absorbs has reached threshold value, directly enter t 6constantly.If no, circuit repeats the action in last cycle.The leakage inductance energy being stored in clamp capacitor Cr due to upper one-period does not discharge, so clamp capacitor Cr energy again increases on the basis of upper one-period, the voltage at clamp capacitor Cr two ends also rises to a stationary value again.Through the time in several cycles, the voltage at clamp capacitor Cr two ends can present a stair-stepping growth.
(6) t 6constantly, the voltage at clamp capacitor Cr two ends has reached threshold voltage, and by divider resistance, by voltage Vr and Vref comparison, auxiliary switch S2 is opened, clamp capacitor Cr and leakage inductance Lr resonance, and clamp capacitor Cr discharges immediately.An energy part in Cr is discharged into output by transformer, and a part stores in leakage inductance.T 7primary current Ip discharges into maximum, oppositely increases subsequently.
(7) t 8constantly, auxiliary switch S2 is turned off, leakage inductance Lr and parasitic capacitance C1 resonance.Parasitic capacitance C1 electric discharge, Vds declines.
(8) t 9constantly, former limit switching tube S1 drain-source both end voltage Vds drops to zero.In order to prevent the common of S1 and S2, now S1 is still in off state.Until next cycle while arriving is open-minded by former limit switching tube S1, now to have realized no-voltage open-minded for S1.

Claims (3)

1. the control method of an auxiliary switching tube of active clamp flyback converter S2, it is characterized in that: former limit each cycle of switching tube S1 is open-minded, auxiliary switch S2 controls by the first voltage threshold control circuit (1) or second voltage thresholding control circuit (2), when former limit switching tube S1 turn-offs, leakage inductance energy absorbs to clamp capacitor Cr by the diode D2 in active clamp circuit, by setting reference voltage V ref, when the voltage Vr obtaining by electric resistance partial pressure on capacitor C r surpasses reference voltage V ref, open auxiliary switch S2.
2. the control method of a kind of auxiliary switching tube of active clamp flyback converter S2 according to claim 1, its the first voltage threshold control circuit (1) is characterised in that, one end of resistance R 1 is connected with the drain electrode of auxiliary switch S2, the other end of resistance R 1 is connected with resistance R 2, by resistance R 1 and R2 dividing potential drop, obtain voltage Vr, voltage Vr is connected with the in-phase end of comparator, reference voltage V ref is connected with the end of oppisite phase of comparator, the output of comparator is directly connected with the grid of auxiliary switch S2 or is connected with the grid of auxiliary switch S2 after amplifying circuit amplifies.
3. the control method of a kind of auxiliary switching tube of active clamp flyback converter S2 according to claim 1, its second voltage thresholding control circuit (2) is characterised in that, one end of resistance R 1 is connected with the drain electrode of auxiliary switch S2, the other end of resistance R 1 is connected with resistance R 2, by resistance R 1 and R2 dividing potential drop, obtain voltage Vr, voltage Vr is connected with the in-phase end of comparator, reference voltage V ref is connected with the end of oppisite phase of comparator, the output of comparator is connected with the R end of SR latch, the S end of SR latch drives signal Vpulse to be connected with one, drive signal Vpulse high level to arrange before arriving at the signal of opening of former limit switching tube S1, the output Q ' of SR latch is directly connected with the grid of auxiliary switch S2 or is connected with the grid of auxiliary switch S2 after amplifying circuit amplifies, the characteristic of the SR latch using in control circuit is as following table:
S R Q Q’ 1 0 1 0 0 1 0 1 1 1 0 0 0 0 Previous?Q Previous?Q’
This SR latch consists of XOR gate inclusive NAND door.
CN201010502461.0A 2010-10-11 2010-10-11 Control method for auxiliary switching tube of active clamp flyback converter CN102122890B (en)

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US9252676B2 (en) * 2013-02-18 2016-02-02 System General Corp. Adaptive active clamp of flyback power converter with high efficiency for heavy load and light load
US10038387B2 (en) 2013-04-15 2018-07-31 Semiconductor Components Industries, Llc Control circuit for active clamp flyback power converter with predicted timing control
TWI560537B (en) * 2013-10-04 2016-12-01 Leadtrend Tech Corp Controller for adjusting an output voltage of a power converter
CN104300795B (en) * 2014-10-11 2017-08-11 广州金升阳科技有限公司 A kind of anti exciting converter and its control method
CN106533175A (en) * 2015-09-11 2017-03-22 亚荣源科技(深圳)有限公司 Retracing type power converter
CN205407592U (en) * 2016-01-29 2016-07-27 深圳嘉润茂电子有限公司 No -voltage quasi -resonance boost circuit
CN106100352B (en) * 2016-08-05 2019-02-05 广州金升阳科技有限公司 Flyback control circuit and control method
CN107017780B (en) * 2017-05-31 2019-05-10 青岛大学 A kind of the isolated form DC-DC boost converter and its control method of band pull-up active clamp branch
CN107017779B (en) * 2017-05-31 2019-05-10 青岛大学 A kind of isolated form DC-DC boost converter control method of band drop-down active clamp branch
CN107294388B (en) * 2017-06-30 2020-02-14 广州金升阳科技有限公司 Flyback switching power supply
CN107395018A (en) * 2017-06-30 2017-11-24 广州金升阳科技有限公司 A kind of positive exciting switching voltage regulator
CN107276414B (en) * 2017-06-30 2020-02-14 广州金升阳科技有限公司 Active clamping flyback switching power supply circuit
CN107196515A (en) * 2017-06-30 2017-09-22 广州金升阳科技有限公司 A kind of active clamp positive activation type switching power circuit
US10644607B2 (en) * 2017-08-03 2020-05-05 Futurewei Technologies, Inc. Auxiliary power supply apparatus and method for isolated power converters
CN109245569B (en) * 2018-09-18 2020-04-24 西安矽力杰半导体技术有限公司 Flyback converter and control circuit thereof
CN109546849A (en) * 2019-01-10 2019-03-29 北京新雷能科技股份有限公司 Flyback converter active clamp circuit
CN110112917A (en) * 2019-04-15 2019-08-09 西安矽力杰半导体技术有限公司 Control circuit and the active clamping circuir for applying it
CN110677045B (en) * 2019-09-20 2020-09-15 广州金升阳科技有限公司 Control method of active clamp flyback converter

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Inventor after: Liu Shuo

Inventor after: Zhang Fanghua

Inventor after: Xiao Xu

Inventor after: Hu Zhijun

Inventor after: Zhu Dan

Inventor before: Liu Shuo

Inventor before: Ni Jianjun

Inventor before: Zhang Fanghua

COR Change of bibliographic data

Free format text: CORRECT: INVENTOR; FROM: LIU SHUO NI JIANJUN ZHANG FANGHUA TO: LIU SHUO ZHANG FANGHUA XIAO XU HU ZHIJUN ZHU DAN

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