CN107733235B - Flyback active clamp circuit and control method thereof - Google Patents

Flyback active clamp circuit and control method thereof Download PDF

Info

Publication number
CN107733235B
CN107733235B CN201711019654.9A CN201711019654A CN107733235B CN 107733235 B CN107733235 B CN 107733235B CN 201711019654 A CN201711019654 A CN 201711019654A CN 107733235 B CN107733235 B CN 107733235B
Authority
CN
China
Prior art keywords
switching tube
voltage
main power
capacitor
primary winding
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201711019654.9A
Other languages
Chinese (zh)
Other versions
CN107733235A (en
Inventor
黄必亮
周逊伟
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Joulwatt Technology Co Ltd
Original Assignee
Joulwatt Technology Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Joulwatt Technology Co Ltd filed Critical Joulwatt Technology Co Ltd
Priority to CN201711019654.9A priority Critical patent/CN107733235B/en
Publication of CN107733235A publication Critical patent/CN107733235A/en
Application granted granted Critical
Publication of CN107733235B publication Critical patent/CN107733235B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • 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
    • H02M3/33569—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 several active switching elements
    • 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
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The invention discloses a flyback active clamp circuit and a control method thereof, wherein the flyback active clamp circuit comprises a flyback switching power supply, a first capacitor and a first switching tube, one end of the first capacitor is connected with a high potential end of an input power supply, the other end of the first capacitor is connected with a first end of the first switching tube, and a second end of the first switching tube is connected to a common end of a main power switching tube and a primary winding; and adjusting the turn-off time of the first switching tube according to the time when the main power switching tube is turned on and the first switching tube is turned off and the voltage at two ends of the magnetizing inductor. The invention can reduce the turn-on loss of the main power switch tube and is also beneficial to the reduction of the turn-on loss.

Description

Flyback active clamp circuit and control method thereof
Technical Field
The invention relates to the technical field of power electronics, in particular to a flyback active clamp circuit and a control method thereof.
Background
Flyback switching power supplies are an isolated switching power supply that are widely used for alternating current-to-direct current (AC/DC) and direct current-to-direct current (DC/DC) conversion and provide insulating isolation between an input stage and an output stage. The flyback switching power supply comprises a main power switching tube, a transformer and a secondary rectifying tube, wherein the transformer comprises a primary winding and a secondary winding, the main power switching tube is connected with the primary winding, the secondary rectifying tube is connected with the secondary winding, a primary control circuit controls the switching state of the main power switching tube, and the secondary rectifying tube positioned on the secondary side is conducted with follow current after the main power switching tube is turned off.
The active clamping topological structure is characterized in that a capacitor is connected with the drain electrode of a main power switch tube of a flyback switching power supply, a switch tube is connected between the drain electrode of the main power switch tube and the capacitor, and the capacitor is connected with an input power supply. When the main power switch tube is turned on and then turned off, the drain electrode is turned off instantly, and instant peak and higher harmonic of the turn-off waveform are coupled to the power supply through a capacitor, so that the purpose of clamping the drain voltage of the main power switch tube is achieved, the turn-off loss of the main power switch tube is reduced, and the power loss of the switch power supply is reduced.
As shown in fig. 1, a flyback active clamp is illustrated in which the magnetizing current is near zero at the beginning of each switching cycle when the system is operating in BCM or DCM. In the prior art, the switching tube MA is generally controlled to be turned on and off in the manner shown in fig. 2, when the main power switching tube M0 is turned on, the switching tube MA is turned off, and when the main power switching tube M0 is turned off, the switching tube MA is turned on.
L M For magnetizing inductance in the primary winding, the prior art uses the control scheme of fig. 2 to control the turn-off of the switching tube MA,since there is no accurate control of the switching time of the switching tube MA before the main power switching tube M0 is turned on, L may be caused M And the upper negative current is too large to increase the conduction loss.
Disclosure of Invention
Therefore, the invention aims to provide a flyback active clamp circuit for reducing the turn-on loss of a main power switch tube by controlling the turn-off time of the switch tube, which solves the technical problem of large turn-on loss of the main power switch tube in the prior art.
In order to achieve the above purpose, the invention provides a flyback active clamp circuit, which comprises a main power switching tube, a transformer and a secondary rectifying tube, wherein the transformer comprises a primary winding and a secondary winding, the primary winding comprises a magnetizing inductor, the main power switching tube is connected with the primary winding, the secondary rectifying tube is connected with the secondary winding, the switching state of the main power switching tube is controlled by a primary control circuit, and the secondary rectifying tube is conducted for follow current after the main power switching tube is turned off;
the flyback active clamp circuit further comprises a first capacitor and a first switching tube, one end of the first capacitor is connected with a high-potential end of an input power supply, the other end of the first capacitor is connected with a first end of the first switching tube, and a second end of the first switching tube is connected to a common end of the main power switching tube and the primary winding;
and adjusting the turn-off time of the first switching tube according to the time when the main power switching tube is turned on and the first switching tube is turned off and the voltage at two ends of the magnetizing inductor.
Optionally, after the first switching tube is turned off, detecting the voltage or the voltage change rate of the common terminal of the main power switching tube and the primary winding, and when the voltage of the common terminal of the main power switching tube and the primary winding or the voltage change rate of the common terminal of the main power switching tube and the primary winding reaches a corresponding threshold value for a period of time, advancing or delaying the turn-off time of the next period of the first switching tube.
Optionally, the flyback active clamp circuit further includes a switching tube control circuit for controlling the first switching tube to be turned off, the switching tube control circuit includes a second capacitor, detects voltages at two ends of the magnetizing inductor, and obtains a current signal representing the voltages at two ends of the magnetizing inductor, the current signal charges the second capacitor during a period that the main power switching tube is turned on and the first switching tube is turned off, the current signal discharges the second capacitor during a period that the main power switching tube is turned off and the first switching tube is turned on, and when a voltage on the second capacitor drops to a corresponding reference signal in a discharging process, the first switching tube is controlled to be turned off.
Optionally, the switch control circuit further includes an auxiliary winding, a first resistor and a comparison circuit, the auxiliary winding is coupled with the transformer, the first resistor is connected with the auxiliary winding to sample the voltage of the auxiliary winding, the voltage on the first resistor represents the voltage at two ends of the magnetizing inductor, the current on the first resistor is sampled to obtain a current signal representing the voltage at two ends of the magnetizing inductor, the current signal is input to the second capacitor, the voltage on the second capacitor is connected to the first input end of the comparison circuit, the reference signal is connected to the second input end of the comparison circuit, and the output end of the comparison circuit is connected with the control end of the first switch tube.
Optionally, after the first switch Guan Guan is turned off and before the main power switch tube is turned on, the voltage across the second capacitor is kept equal to the initial voltage.
Optionally, when the voltage or the voltage change rate of the common terminal of the main power switch tube and the primary winding is lower than a corresponding threshold value, the reference signal is increased to advance the turn-off time of the first switch tube; and when the voltage or the voltage change rate of the common terminal of the main power switching tube and the primary winding is higher than a corresponding threshold value, delaying the turn-off time of the first switching tube by reducing the reference signal.
Optionally, when the voltage or the voltage change rate of the common terminal of the main power switch tube and the primary winding is lower than a corresponding threshold value, the turn-off time of the first switch tube is advanced by reducing the second capacitor or increasing the discharge current of the second capacitor; when the voltage or the voltage change rate of the common terminal of the main power switching tube and the primary winding is higher than a corresponding threshold value, the turn-off time of the first switching tube is delayed by increasing the second capacitor or reducing the discharge current of the second capacitor.
The invention also provides a control method of the flyback active clamp circuit,
based on the flyback active clamp circuit, the flyback active clamp circuit comprises a main power switching tube, a transformer and a secondary rectifying tube, wherein the transformer comprises a primary winding and a secondary winding, the primary winding comprises a magnetizing inductor, the main power switching tube is connected with the primary winding, the secondary rectifying tube is connected with the secondary winding, the primary control circuit controls the switching state of the main power switching tube, and the secondary rectifying tube is conducted with follow current after the main power switching tube is turned off;
the flyback active clamp circuit further comprises a first capacitor and a first switching tube, one end of the first capacitor is connected with a high-potential end of an input power supply, the other end of the first capacitor is connected with a first end of the first switching tube, and a second end of the first switching tube is connected to a common end of the main power switching tube and the primary winding;
and adjusting the turn-off time of the first switching tube according to the time when the main power switching tube is turned on and the first switching tube is turned off and the voltage at two ends of the magnetizing inductor.
Optionally, after the first switching tube is turned off, detecting the voltage or the voltage change rate of the common terminal of the main power switching tube and the primary winding, and when the voltage of the common terminal of the main power switching tube and the primary winding or the voltage change rate of the common terminal of the main power switching tube and the primary winding reaches a corresponding threshold value for a period of time, advancing or delaying the turn-off time of the next period of the first switching tube.
Optionally, the flyback active clamp circuit further includes a switching tube control circuit for controlling the first switching tube to be turned off, the switching tube control circuit includes a second capacitor, detects voltages at two ends of the magnetizing inductor, and obtains a current signal representing the voltages at two ends of the magnetizing inductor, the current signal charges the second capacitor during a period that the main power switching tube is turned on and the first switching tube is turned off, the current signal discharges the second capacitor during a period that the main power switching tube is turned off and the first switching tube is turned on, and when a voltage on the second capacitor drops to a corresponding reference signal in a discharging process, the first switching tube is controlled to be turned off.
Optionally, after the first switch Guan Guan is turned off and before the main power switch tube is turned on, the voltage across the second capacitor is kept equal to the initial voltage.
Compared with the prior art, the technical scheme of the invention has the following advantages: the invention aims at discharging the common end (drain electrode of the main power switch tube) of the main power switch tube and the primary winding before the main power switch tube is conducted by controlling the turn-off time of the first switch tube, thereby controlling the magnetizing inductance to have slight negative current. The invention can reduce the turn-on loss of the main power switch tube and is also beneficial to the reduction of the turn-on loss.
Drawings
FIG. 1 is a schematic diagram of a prior art flyback active clamp circuit;
FIG. 2 is a schematic diagram of a control waveform of a prior art flyback active clamp;
FIG. 3 is a schematic diagram of a flyback active clamp circuit according to the present invention;
fig. 4 is a waveform schematic diagram of the flyback active clamp of the present invention.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments only. The invention is intended to cover any alternatives, modifications, equivalents, and variations that fall within the spirit and scope of the invention.
In the following description of preferred embodiments of the invention, specific details are set forth in order to provide a thorough understanding of the invention, and the invention will be fully understood to those skilled in the art without such details.
The invention is more particularly described by way of example in the following paragraphs with reference to the drawings. It should be noted that the drawings are in a simplified form and are not to scale precisely, but rather are merely intended to facilitate and clearly illustrate the embodiments of the present invention.
As shown in FIG. 3, the flyback active clamp circuit of the invention comprises a main power switch tube M0, a transformer and a secondary rectifying tube D1, wherein the transformer comprises a primary winding L1 and a secondary winding L2, and the primary winding L1 comprises a magnetizing inductance L M The main power switch tube M0 is connected with the primary winding L1, the secondary rectifying tube D1 is connected with the secondary winding L2, the primary control circuit controls the switch state of the main power switch tube M0, and the secondary rectifying tube D1 is conducted for follow current after the main power switch tube M0 is turned off;
the flyback active clamp circuit also comprises a first capacitor C1 and a first switching tube M A One end of the first capacitor C1 is connected with the high potential end of the input power supply, and the other end is connected with the first switch tube M A Is connected with the first end of the first switch tube M A The second end of the primary winding L1 is connected to the common end of the primary winding L1 and the primary power switch tube M0;
according to the main power switch tube M0, a first switch tube M is conducted A Time of turn-off and the magnetizing inductance L M Voltage at two ends, adjust the first switch tube M A Is controlled to be turned off. The method is realized mainly by volt-second balance, and specifically comprises the following steps: when the main power switch tube M0 is turned on, the first switch tube M A When turned off, magnetizing inductance L M The voltage at Vin-V SW When the main power switch tube M0 is turned off, the first switch tube M A When turned on, L M The voltage at V A By L M Volt-second balance of upper voltage to determine M A Is not exceeded.
From the circuit implementation, the switching tube control circuit is implemented, as shown in fig. 3, and comprises a second capacitor C2 for detecting the magnetizing inductance L M The voltage at two ends and the characterization magnetizing inductance L is obtained M The current signal of the voltage at two ends is conducted in the main power switch tube M0 and the first switch tube M A During the turn-off period, the current signal charges the second capacitor C2, and the main power switch tube M0 is turned off and the first switch tube M A During the on period, the current signal pairAnd the second capacitor C2 is discharged, and when the voltage on the second capacitor C2 is reduced to the corresponding reference signal Vref in the discharging process, the first switching tube M0 is controlled to be turned off.
For magnetizing inductance L M There are various implementations of the detection of the voltages at the two ends, the embodiment uses an auxiliary winding, and the switch control circuit further includes an auxiliary winding L N A first resistor R1 and a comparison circuit U1, the auxiliary winding L N Coupled to the transformer, the first resistor R1 is connected to the auxiliary winding L2 to sample the auxiliary winding L N The voltage across the first resistor R1 being indicative of the magnetizing inductance L M The voltage at two ends samples the current of the first resistor R1, and in particular, the current source i1 is regulated by the sampled current, and the current source i1 is regulated by the sampled current, for example, by the proportion K, so as to obtain the characterization magnetizing inductance L M The current signal of the voltage of both ends, the current signal is input to the second capacitor C2, the voltage on the second capacitor C2 is connected to the first input end of the comparison circuit U1, the reference signal Vref is connected to the second input end of the comparison circuit U1, and the output end of the comparison circuit U1 and the first switch tube M A Is connected with the control end of the control circuit. The principle of the circuit mainly utilizes the form of charging and discharging a capacitor, and the first switch tube M is conducted according to the main power switch tube M0 A Time of turn-off, the magnetizing inductance L M Voltage at two ends, adjust the first switch tube M A Is turned off to release the first switching tube M A The energy of the drain to reduce the turn-on loss. After the first switch Guan Guan is turned off, before the main power switch tube is turned on, the voltage across the second capacitor is kept equal to the initial voltage, which is a set value and can be set according to practical applications, for example, in the intermittent conduction mode, the magnetizing inductance L M The initial voltage can be set to be slightly smaller than the reference signal, so that no negative current is generated on the magnetizing inductor before the main power switch tube is turned on, and the conduction loss is reduced; in the continuous conduction mode, before the main power switch tube is turned on,controlling magnetizing inductance L M With a slight negative current thereon, with which V is opposite SW Discharging can reduce the turn-on loss of M0, so the initial voltage can be set to be slightly larger than the reference signal, thereby realizing L M With a slight negative current.
In fig. 3, the output end of the comparison circuit U1 is connected with the first switch tube M A For convenience of illustration, the control terminal connection of (a) is not necessarily a direct connection, and a control or logic conversion circuit or the like is provided therebetween.
Further, to prevent at the first switching tube M A The energy loss caused by the excessive negative current after the turn-off is determined by the voltage drop rate of the common terminal of the main power switch tube and the primary winding, if M A When the negative current is too large after the switch-off, the voltage of the public terminal drops faster, and the judgment can be carried out by at least two means. First, according to the voltage change rate of the voltage Vsw of the common terminalWhen the voltage or the voltage change rate is lower than the corresponding threshold value, the absolute value of the voltage change rate is larger because the voltage change rate is a negative value, but the voltage or the voltage change rate is still treated by negative number at the moment, and when the voltage or the voltage change rate is lower than the corresponding threshold value, the turn-off time of the next period of the first switching tube is advanced. And secondly, presetting a time period, and if the voltage Vsw of the common terminal is lower than a corresponding threshold value in the time period, advancing the turn-off time of the next period of the first switching tube. The two approaches may differ from one implementation to another, but are both essentially detecting the rate of change of the voltage. Thereby realizing the magnetizing inductance L before the main power switch tube M0 is switched on M With a negative current, which is not too great, just for supplying the voltage V SW Discharging, the turn-on loss of the main power switch tube M0 is reduced, and the turn-on loss is not increased. Embodied in the circuit of fig. 3, i.e. when the voltage V SW Is>Reaching a certain threshold or V SW When the time of falling to a certain threshold value is shortened, the value of the reference signal Vref is increased when the value of the negative current is too large, so that the turn-off time of the next period of the first switching tube is advanced, and the negative current is reduced. The above description has been given by way of example only of a case below a respective threshold above which the turn-off instant of the next cycle of the first switching tube can be delayed. When the voltage or the voltage change rate of the common end of the main power switching tube and the primary winding is lower than a corresponding threshold value, the reference signal is increased to advance the turn-off time of the first switching tube; and when the voltage or the voltage change rate of the common terminal of the main power switching tube and the primary winding is higher than a corresponding threshold value, delaying the turn-off time of the first switching tube by reducing the reference signal. Besides the mode of adjusting the reference signal, the method can also be realized by adjusting a second capacitor or discharging current of the second capacitor, namely when the voltage or the voltage change rate of the common terminal of the main power switch tube and the primary winding is lower than a corresponding threshold value, the switching-off time of the first switch tube is advanced by reducing the second capacitor or increasing the discharging current of the second capacitor (realized by adjusting the proportionality coefficient of a sampling current control current source i 1); when the voltage or the voltage change rate of the common terminal of the main power switching tube and the primary winding is higher than a corresponding threshold value, the turn-off time of the first switching tube is delayed by increasing the second capacitor or reducing the discharge current of the second capacitor.
As shown in fig. 4, the operational waveforms of the flyback active clamp of the present invention are illustrated. The volt-second balance is shown in fig. 4 as s1=s2, S1, S2 are the areas of the respective regions, the current iL in fig. 4 M To pass through L M Since the current at time t1 is equal to the current at time t3 due to the balance of volt-seconds, t3 is the off time of the first switching tube. The waveforms of the voltage and current values in the figure are both schematic, and in practice, the current iL M Not necessarily linearly changing, magnetizing inductance L M Voltage VL on M And not at constant pressure, the illustrations are for convenience of illustration only and are not to be construed as limiting the inventionAnd (5) preparing.
Although the embodiments have been described and illustrated separately above, and with respect to a partially common technique, it will be apparent to those skilled in the art that alternate and integration may be made between embodiments, with reference to one embodiment not explicitly described, and reference may be made to another embodiment described.
The above-described embodiments do not limit the scope of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the above embodiments should be included in the scope of the present invention.

Claims (9)

1. The flyback active clamp circuit comprises a main power switching tube, a transformer and a secondary rectifying tube, wherein the transformer comprises a primary winding and a secondary winding, the primary winding comprises a magnetizing inductor, the main power switching tube is connected with the primary winding, the secondary rectifying tube is connected with the secondary winding, the primary control circuit controls the switching state of the main power switching tube, and the secondary rectifying tube is conducted to conduct follow current after the main power switching tube is turned off;
the flyback active clamp circuit further comprises a first capacitor and a first switching tube, one end of the first capacitor is connected with a high-potential end of an input power supply, the other end of the first capacitor is connected with a first end of the first switching tube, and a second end of the first switching tube is connected to a common end of the main power switching tube and the primary winding;
according to the time when the main power switching tube is turned on and the first switching tube is turned off and the voltage at two ends of the magnetizing inductor, the turn-off time of the first switching tube is regulated,
after the first switching tube is turned off, detecting the voltage or the voltage change rate of the common end of the main power switching tube and the primary winding, and when the voltage of the common end of the main power switching tube and the primary winding reaches a corresponding threshold value or the voltage change rate of the common end of the main power switching tube and the primary winding reaches a corresponding threshold value for a period of time, advancing or delaying the turn-off time of the next period of the first switching tube.
2. The flyback active clamp of claim 1, further comprising a switching tube control circuit for controlling the first switching tube to turn off, the switching tube control circuit including a second capacitor for detecting a voltage across the magnetizing inductance and obtaining a current signal indicative of the voltage across the magnetizing inductance, the current signal charging the second capacitor during a period when the main power switching tube is on and the first switching tube is off, the current signal discharging the second capacitor during a period when the main power switching tube is off and the first switching tube is on, and controlling the first switching tube to turn off when a voltage across the second capacitor falls to a corresponding reference signal during a discharging period.
3. The flyback active clamp of claim 2, wherein the switching tube control circuit further comprises an auxiliary winding, a first resistor and a comparison circuit, the auxiliary winding is coupled with the transformer, the first resistor is connected with the auxiliary winding to sample the voltage of the auxiliary winding, the voltage on the first resistor characterizes the voltage across the magnetizing inductor, the current on the first resistor is sampled to obtain a current signal characterizing the voltage across the magnetizing inductor, the current signal is input to the second capacitor, the voltage on the second capacitor is connected to a first input terminal of the comparison circuit, the reference signal is connected to a second input terminal of the comparison circuit, and an output terminal of the comparison circuit is connected to a control terminal of the first switching tube.
4. The flyback active clamp of claim 3, wherein the voltage across the second capacitor is maintained equal to the initial voltage after the first switch Guan Guan is turned off and before the main power switch is turned on.
5. The flyback active clamp of claim 2, wherein the reference signal is increased to advance the turn-off time of the first switching tube when the voltage or the voltage change rate of the common terminal of the main power switching tube and the primary winding is lower than a corresponding threshold; and when the voltage or the voltage change rate of the common terminal of the main power switching tube and the primary winding is higher than a corresponding threshold value, delaying the turn-off time of the first switching tube by reducing the reference signal.
6. The flyback active clamp of claim 2, wherein when the voltage or the voltage change rate of the common terminal of the main power switching tube and the primary winding is lower than a corresponding threshold value, the turn-off time of the first switching tube is advanced by decreasing the second capacitance or increasing the discharge current to the second capacitance; when the voltage or the voltage change rate of the common terminal of the main power switching tube and the primary winding is higher than a corresponding threshold value, the turn-off time of the first switching tube is delayed by increasing the second capacitor or reducing the discharge current of the second capacitor.
7. The control method of the flyback active clamp circuit is characterized in that based on the flyback active clamp circuit, the flyback active clamp circuit comprises a main power switching tube, a transformer and a secondary rectifying tube, the transformer comprises a primary winding and a secondary winding, the primary winding comprises a magnetizing inductor, the main power switching tube is connected with the primary winding, the secondary rectifying tube is connected with the secondary winding, the primary control circuit controls the switching state of the main power switching tube, and the secondary rectifying tube is conducted for follow current after the main power switching tube is turned off;
the flyback active clamp circuit further comprises a first capacitor and a first switching tube, one end of the first capacitor is connected with a high-potential end of an input power supply, the other end of the first capacitor is connected with a first end of the first switching tube, and a second end of the first switching tube is connected to a common end of the main power switching tube and the primary winding;
according to the time when the main power switching tube is turned on and the first switching tube is turned off and the voltage at two ends of the magnetizing inductor, the turn-off time of the first switching tube is regulated;
after the first switching tube is turned off, detecting the voltage or the voltage change rate of the common end of the main power switching tube and the primary winding, and when the voltage of the common end of the main power switching tube and the primary winding reaches a corresponding threshold value or the voltage change rate of the common end of the main power switching tube and the primary winding reaches a corresponding threshold value for a period of time, advancing or delaying the turn-off time of the next period of the first switching tube.
8. The method of claim 7, further comprising a switching tube control circuit for controlling the first switching tube to turn off, the switching tube control circuit including a second capacitor, detecting a voltage across the magnetizing inductance and obtaining a current signal indicative of the voltage across the magnetizing inductance, the current signal charging the second capacitor during a period when the main power switching tube is on and the first switching tube is off, the current signal discharging the second capacitor during a period when the main power switching tube is off and the first switching tube is on, and controlling the first switching tube to turn off when a voltage across the second capacitor falls to a corresponding reference signal during the discharging.
9. The method of claim 8, wherein the voltage across the second capacitor is maintained equal to the initial voltage after the first switch Guan Guan is turned off and before the main power switch is turned on.
CN201711019654.9A 2017-10-27 2017-10-27 Flyback active clamp circuit and control method thereof Active CN107733235B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201711019654.9A CN107733235B (en) 2017-10-27 2017-10-27 Flyback active clamp circuit and control method thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201711019654.9A CN107733235B (en) 2017-10-27 2017-10-27 Flyback active clamp circuit and control method thereof

Publications (2)

Publication Number Publication Date
CN107733235A CN107733235A (en) 2018-02-23
CN107733235B true CN107733235B (en) 2023-08-29

Family

ID=61202650

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201711019654.9A Active CN107733235B (en) 2017-10-27 2017-10-27 Flyback active clamp circuit and control method thereof

Country Status (1)

Country Link
CN (1) CN107733235B (en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108809107B (en) * 2018-07-13 2019-08-23 深圳南云微电子有限公司 A kind of method and circuit of the self adaptive control of active clamp flyback converter
CN108988652A (en) * 2018-09-10 2018-12-11 杰华特微电子（张家港）有限公司 Flyback active clamp circuit and its control method
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
CN109546863A (en) * 2018-12-11 2019-03-29 杰华特微电子（杭州）有限公司 A kind of flyback active clamp circuit and its control method
CN112615531A (en) * 2020-12-14 2021-04-06 矽力杰半导体技术(杭州)有限公司 Control circuit and switching converter using same
CN112803780B (en) 2021-02-10 2022-05-10 华为数字能源技术有限公司 Converter and power adapter

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102208873A (en) * 2010-06-11 2011-10-05 崇贸科技股份有限公司 Active clamp circuit of quasi-resonant fly-back power converter
CN106899219A (en) * 2015-12-18 2017-06-27 虹冠电子工业股份有限公司 For the power converter and its mode of operation of Switching Power Supply
CN207868996U (en) * 2017-10-27 2018-09-14 杰华特微电子（杭州）有限公司 Flyback active clamp circuit

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9391528B2 (en) * 2012-12-27 2016-07-12 Fairchild (Taiwan) Corporation Active clamp circuits for flyback power converters
KR102116705B1 (en) * 2013-10-16 2020-06-05 온세미컨덕터코리아 주식회사 Converter and driving method thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102208873A (en) * 2010-06-11 2011-10-05 崇贸科技股份有限公司 Active clamp circuit of quasi-resonant fly-back power converter
CN106899219A (en) * 2015-12-18 2017-06-27 虹冠电子工业股份有限公司 For the power converter and its mode of operation of Switching Power Supply
CN207868996U (en) * 2017-10-27 2018-09-14 杰华特微电子（杭州）有限公司 Flyback active clamp circuit

Also Published As

Publication number Publication date
CN107733235A (en) 2018-02-23

Similar Documents

Publication Publication Date Title
CN107749716B (en) Flyback active clamp circuit and control method thereof
CN107733235B (en) Flyback active clamp circuit and control method thereof
TWI628905B (en) Control method and control device for flyback converter circuit
US10461653B1 (en) Active-clamp flyback circuit and control method thereof
CN111464036B (en) Switch state control method, control circuit and flyback converter
US8829865B2 (en) Power factor correction efficiency improvement circuit, a converter employing the circuit and a method of manufacturing a converter
TW201334377A (en) Isolated flyback converter with efficient light load operation
TW201517489A (en) Isolated switching converters, and switching controllers and controlling methods thereof
CN103812317A (en) Clamping absorption circuit and impedance adjusting method thereof
TW201838303A (en) Control device and control method thereof
CN115211018A (en) Auto-tuned synchronous rectifier controller
CN103049028B (en) Constant current source for high voltage magnetic switch resetting
CN106300925B (en) Drive control circuit, method and its system of AC-DC circuits
CN113098280B (en) Dead time self-adaption method for active clamp flyback converter input
CN114189156A (en) Flyback switching circuit and control method thereof
CN109450256B (en) Quasi-resonance power supply controller
CN208489798U (en) The synchronous rectifying controller of adaptive adjustment driving voltage and the circuit for using it
CN110168890B (en) Control circuit with two-point regulator for regulating clock-driven converter
KR101892059B1 (en) Constant on-time(cot) control in isolated converter
KR101901576B1 (en) Constant on-time(cot) control in isolated converter
Bianco et al. A novel noncomplementary active clamp flyback control technique
CN210297569U (en) Wide-range input-output AC-DC converter
TW202222022A (en) Active clamp flyback converter
CN206041785U (en) AC drive and control circuit of DC circuit and system thereof
CN111193411A (en) Synchronous rectifier tube control circuit, flyback voltage conversion circuit and control method

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
CB02 Change of applicant information
CB02 Change of applicant information

Address after: Room 901-23, 9 / F, west 4 building, Xigang development center, 298 Zhenhua Road, Sandun Town, Xihu District, Hangzhou City, Zhejiang Province, 310030

Applicant after: Jiehuate Microelectronics Co.,Ltd.

Address before: Room 424, building 1, 1500 Wenyi West Road, Cangqian street, Yuhang District, Hangzhou City, Zhejiang Province

Applicant before: JOULWATT TECHNOLOGY Inc.,Ltd.

GR01 Patent grant
GR01 Patent grant