CN110798071A - Primary side conduction judgment method, control circuit and flyback circuit - Google Patents
Primary side conduction judgment method, control circuit and flyback circuit Download PDFInfo
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- CN110798071A CN110798071A CN201910991212.3A CN201910991212A CN110798071A CN 110798071 A CN110798071 A CN 110798071A CN 201910991212 A CN201910991212 A CN 201910991212A CN 110798071 A CN110798071 A CN 110798071A
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- 230000001360 synchronised effect Effects 0.000 claims abstract description 226
- 230000010354 integration Effects 0.000 claims abstract description 64
- 238000001514 detection method Methods 0.000 claims description 18
- 238000010586 diagram Methods 0.000 description 5
- 239000003990 capacitor Substances 0.000 description 2
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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
- 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
- H02M3/33576—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 having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33592—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 having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
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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
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
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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
- H02M1/0003—Details of control, feedback or regulation circuits
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- 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
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Abstract
The invention discloses a primary side conduction judgment method, a control circuit and a flyback circuit, wherein the drain-source voltage of a synchronous rectifier tube of the flyback circuit is detected, when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is larger than the average value of the drain-source voltage of the synchronous rectifier tube, volt-second integration is carried out on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube from zero, and when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is smaller than the average value of the drain-source voltage of the synchronous rectifier tube, the integration is ended to obtain a first integration; when the first integral is greater than a first integral threshold, the primary side conduction at the volt-second integral is characterized and the current in the transformer of the flyback circuit exceeds a first current threshold.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a primary side conduction judgment method, a control circuit and a flyback circuit.
Background
In the flyback circuit, a fly-wheel diode on the secondary side is replaced by a synchronous rectifier tube to improve the conversion efficiency of the system. However, the control circuit of the synchronous rectifier tube does not detect the primary side circuit, and cannot obtain the on and off information of the primary side main switching tube, and whether the primary side is on or not can be judged only through the drain-source voltage value on the secondary side synchronous rectifier tube, so that the on and off of the secondary side synchronous rectifier tube are controlled. Therefore, how to accurately control the on and off of the secondary synchronous rectifier without the on information of the primary main switching tube is an important problem in the flyback circuit with synchronous rectification.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a primary side on-state determining method, a primary side on-state determining control method, a primary side on-state control circuit, and a flyback circuit, so as to solve the problem that the on-state and the off-state of a secondary side synchronous rectifier cannot be precisely controlled in the prior art.
The invention provides a primary side conduction judging method, which comprises the steps of detecting the drain-source voltage of a synchronous rectifier tube of a flyback circuit, carrying out volt-second integration on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube from zero when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is larger than the average value of the drain-source voltage of the synchronous rectifier tube, and finishing the integration to obtain a first integration when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is smaller than the average value of the drain-source voltage of the synchronous rectifier tube;
when the first integral is greater than a first integral threshold, the primary side is conducted and the transformer current exceeds a first current threshold when the voltage-second integral is represented.
The invention also provides a synchronous rectification control method, which comprises the steps of detecting the drain-source voltage of a synchronous rectifier tube of a flyback circuit, carrying out volt-second integration on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube from zero when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is larger than the average value of the drain-source voltage of the synchronous rectifier tube, and finishing the integration to obtain a first integration when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is smaller than the average value of the drain-source voltage of the synchronous rectifier tube;
the first integral greater than the first integral threshold value is a necessary condition for the synchronous rectifier tube to be conducted.
Optionally, the drain-source voltage of the synchronous rectifier tube is sampled and filtered, so as to output an average value representing the drain-source voltage of the synchronous rectifier tube.
Optionally, the necessary conduction condition of the synchronous rectifier tube is that the drain-source voltage of the synchronous rectifier tube is smaller than a first voltage threshold or/and the absolute value of the change rate of the drain-source voltage of the synchronous rectifier tube with time is larger than a first slope threshold.
The invention provides a synchronous rectification control circuit, which is used for detecting drain-source voltage of a synchronous rectifier tube of a flyback circuit, when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is larger than the average value of the drain-source voltage of the synchronous rectifier tube, the synchronous rectification control circuit performs volt-second integration on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube from zero, and when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is smaller than the average value of the drain-source voltage of the synchronous rectifier tube, the integration is ended to obtain a first integration;
the first integral greater than the first integral threshold value is a necessary condition for the synchronous rectifier tube to be conducted.
Optionally, the synchronous rectification control circuit samples the drain-source voltage of the synchronous rectifier tube, filters the drain-source voltage of the synchronous rectifier tube, and outputs an average value representing the drain-source voltage of the synchronous rectifier tube.
Optionally, an integration circuit is included, when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is larger than the average value of the drain-source voltage of the synchronous rectifier tube, the integrating circuit integrates the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube from zero in volt seconds, ending integration to obtain a first integration when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, comparing the first integral with a first integral threshold to obtain a first voltage, and when the first integral is greater than the first integral threshold, and if not, the first voltage is invalid, the integrating circuit latches the first voltage to obtain a first latching result, and the volt-second integration is cleared, wherein the first latching result is the output voltage of the integrating circuit.
Optionally, the synchronous rectifier further comprises a comparison circuit and a logic circuit, the comparison circuit compares the drain-source voltage of the synchronous rectifier with a first voltage threshold, the logic circuit receives the output voltages of the comparison circuit and the integration circuit, and when the output voltage of the integration circuit is valid and the drain-source voltage of the synchronous rectifier is smaller than the first voltage threshold, the output of the logic circuit changes from invalid to valid.
Optionally, the synchronous rectifier further includes a slope detection comparison circuit, where the slope detection comparison circuit compares an absolute value of a change rate of the drain-source voltage of the synchronous rectifier with time with a first slope threshold, and the absolute value of the change rate of the drain-source voltage of the synchronous rectifier with time is compared with the first slope threshold to obtain a second voltage; and the absolute value of the change rate of the drain-source voltage of the synchronous rectifier tube along with the time is larger than the first slope threshold, the second voltage is effective, the slope detection comparison circuit latches the second voltage to obtain a second latch result, and the second latch result is the output voltage of the slope detection comparison circuit.
The logic circuit receives the output voltage of the slope detection comparison circuit, and when the output voltage of the integration circuit is effective, the drain-source voltage of the synchronous rectifier tube is smaller than a first voltage threshold value, and the output voltage of the slope detection comparison circuit is effective, the output of the logic circuit is changed from invalid to effective.
Another technical solution of the present invention is to provide a flyback circuit.
Compared with the prior art, the circuit structure and the method have the following advantages that: and accurately controlling the turn-on of the secondary synchronous rectifier tube of the flyback circuit.
Drawings
FIG. 1 is a flyback circuit with a synchronous rectifier M21 connected to the positive side of the secondary output voltage;
FIG. 2 is a flyback circuit with a synchronous rectifier M21 connected to the negative terminal of the secondary output voltage;
FIG. 3 shows the drain-source current I of the synchronous rectifierDSA waveform diagram of a drain-source voltage SW of the synchronous rectifier tube and a waveform diagram of a driving signal GT of the synchronous rectifier tube;
fig. 4 is a circuit block diagram of the synchronous rectification control circuit 100.
Detailed Description
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 only these embodiments. The invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention.
In the following description of the preferred embodiments of the present invention, specific details are set forth in order to provide a thorough understanding of the present invention, and it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.
The invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are in simplified form and are not to precise scale, which is only used for convenience and clarity to assist in describing the embodiments of the present invention.
The invention provides a method for judging the primary side conduction of a flyback circuit, wherein the flyback circuit comprises a transformer TR11, a main switching tube M11 and a synchronous rectifying tube M21. Detecting the drain-source voltage of a synchronous rectifier tube M21 of a flyback circuit, performing volt-second integration on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube from zero when the instantaneous value of the drain-source voltage of the synchronous rectifier tube M21 is larger than the average value of the drain-source voltage of the synchronous rectifier tube M21, and finishing the integration to obtain a first integration when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is smaller than the average value of the drain-source voltage of the synchronous rectifier tube; when the first integral is greater than a first integral threshold, the primary side is conducted and the transformer current exceeds a first current threshold when the voltage-second integral is represented.
The method for judging the primary side conduction of the flyback circuit is suitable for connecting the synchronous rectifier tube to the output high-voltage end and the output low-voltage end. Referring to fig. 1 and fig. 2, a flyback circuit with a synchronous rectifier M21 is shown, wherein fig. 1 is the synchronous rectifier connected to the positive terminal of the secondary output voltage, and fig. 2 is the synchronous rectifier connected to the negative terminal of the secondary output voltage. It should be noted that, in fig. 1 and 2, the primary side ground, i.e., the source of M11 and the source of the synchronous rectifier M21, are labeledThe ground GND of (1) is a different reference ground and is not at the same potential. FIG. 3 shows the drain-source current I of the synchronous rectifierDSA drain-source voltage SW of the synchronous rectifier tube, a waveform diagram of a driving signal GT of the synchronous rectifier tube,
the invention also provides a synchronous rectification control method, which comprises the steps of detecting the drain-source voltage of a synchronous rectifier tube of a flyback circuit, carrying out volt-second integration on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube from zero when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is larger than the average value of the drain-source voltage of the synchronous rectifier tube, and finishing the integration to obtain a first integration when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is smaller than the average value of the drain-source voltage of the synchronous rectifier tube; the first integral greater than the first integral threshold value is a necessary condition for the synchronous rectifier tube to be conducted. Specifically, in one embodiment, referring to fig. 3, at time t0, the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier and the average value of the drain-source voltage of the synchronous rectifier is integrated from zero in volt-seconds, and at time t1, the integration is ended, and at this time, the first integration is greater than the first integration threshold, the comparison result is latched to obtain a first latch result, and the first latch result is valid, and after latching, the first integration can be cleared. The synchronous rectifier can only be switched on if the first latch result is valid and the other switching-on conditions of the synchronous rectifier are reached. The first latch result can be cleared when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is larger than the average value of the drain-source voltage of the synchronous rectifier tube next time, namely, cleared at the time t4, and the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube is integrated again, at the time t5, the instantaneous value of the drain-source voltage of the synchronous rectifier tube is smaller than the average value of the drain-source voltage of the synchronous rectifier tube, the integration is finished, at the time, the first integration is smaller than the first integration threshold value, and even if the conduction condition of the synchronous rectifier tube is met later, the synchronous rectifier tube cannot be conducted. In another embodiment, with continued reference to fig. 3, at time t1, the first integral is greater than the first integral threshold, the first integral is maintained, the first integral is not cleared, and the synchronous rectifier can be turned on when other turn-on conditions of the synchronous rectifier are reached; the first integration may be cleared when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is greater than the average value of the drain-source voltage of the synchronous rectifier tube next time, that is, cleared at time t4, and the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube is newly integrated.
It should be noted that, since the average value of the drain-source voltage of the synchronous rectifier is equal to the output voltage, in fig. 3, the average value of the drain-source voltage of the synchronous rectifier is replaced by the output voltage VO, where the shaded portions S1 and S2 are values of twice volt-second integrations, and each integration is a volt-second integration from zero.
In one embodiment, an average value representing the drain-source voltage of the synchronous rectifier is output by sampling the drain-source voltage of the synchronous rectifier and filtering the drain-source voltage of the synchronous rectifier. The drain-source voltage of the synchronous rectifier tube can be filtered by adopting a resistor capacitor RC.
In one embodiment, the necessary conduction condition of the synchronous rectifier is that the drain-source voltage of the synchronous rectifier is less than a first voltage threshold. Referring to fig. 3, at time t1, the first integral is greater than the first integral threshold, at time t2, the drain-source voltage of the synchronous rectifier is less than the first voltage threshold minus 300mV, and since there is a delay in turning on the synchronous rectifier, the driving signal GT of the synchronous rectifier goes from low to high at time t 3. In another embodiment, if the absolute value of the rate of change of the drain-source voltage of the synchronous rectifier with time is greater than the first slope threshold, the comparison result is latched to obtain a second latched result, and the second latch is valid. When the second latch result is valid and the drain-source voltage of the synchronous rectifier tube is less than the first voltage threshold, the second latch result is a necessary conduction condition of the synchronous rectifier tube.
The invention provides a synchronous rectification control circuit, which is used for detecting drain-source voltage of a synchronous rectifier tube of a flyback circuit, when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is larger than the average value of the drain-source voltage of the synchronous rectifier tube, the synchronous rectification control circuit performs volt-second integration on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube from zero, and when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is smaller than the average value of the drain-source voltage of the synchronous rectifier tube, the integration is ended to obtain a first integration; the first integral is larger than a first integral threshold value, which is a necessary condition for the conduction of the synchronous rectifier tube.
Referring to fig. 1 and fig. 2, the flyback circuit with the synchronous rectifier M21 is shown, the synchronous rectifier control circuit 100 is connected to the gate, the source and the drain of the synchronous rectifier M21, and the source of the synchronous rectifier M21 is the reference ground of the synchronous rectifier control circuit 100. In which fig. 1 shows the synchronous rectifier M21 connected to the positive terminal of the secondary output voltage, and fig. 2 shows the synchronous rectifier M21 connected to the negative terminal of the secondary output voltage. It should be noted that, in fig. 1 and fig. 2, the primary side ground, that is, the source of M11 and the reference ground of the synchronous rectification control circuit 100, are not at the same potential.
In one embodiment, the synchronous rectification control circuit outputs an average value representing the drain-source voltage of the synchronous rectifier tube by sampling the drain-source voltage of the synchronous rectifier tube and filtering the drain-source voltage of the synchronous rectifier tube. The drain-source voltage of the synchronous rectifier tube can be filtered by adopting a resistor capacitor RC.
Referring to fig. 4, a block diagram of an implementation of the synchronous rectification control circuit 100 includes an integrating circuit 110, when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is larger than the average value of the drain-source voltage of the synchronous rectifier tube, the integrating circuit integrates the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube from zero in volt seconds, ending integration to obtain a first integration when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is less than the average value of the drain-source voltage of the synchronous rectifier tube, comparing the first integral with a first integral threshold to obtain a first voltage, and when the first integral is greater than the first integral threshold, and if not, the first voltage is invalid, the integrating circuit latches the first voltage to obtain a first latching result, and the volt-second integration is cleared, wherein the first latching result is the output voltage of the integrating circuit. The first latch result can be cleared when the instantaneous value of the drain-source voltage of the synchronous rectifier tube at the next time is larger than the average value of the drain-source voltage of the synchronous rectifier tube.
As shown in fig. 4, the synchronous rectifier further includes a comparison circuit 120 and a logic circuit 140, the comparison circuit compares the drain-source voltage SW of the synchronous rectifier with a first voltage threshold, the logic circuit 140 receives the output voltages of the comparison circuit and the integration circuit 110, and when the output voltage of the integration circuit is valid and the drain-source voltage of the synchronous rectifier is smaller than the first voltage threshold, the output of the logic circuit changes from invalid to valid. The driving circuit 150 is used for receiving the output voltage of the logic circuit 140, when the output of the logic circuit is effective, the driving circuit 150 drives the synchronous rectifier tube to be connected, and when the output of the logic circuit is ineffective, the driving circuit 150 drives the synchronous rectifier tube to be disconnected.
In an embodiment, please refer to fig. 4, further comprising a slope detection comparing circuit 140, wherein the slope detection comparing circuit 140 compares an absolute value of a time-dependent change rate of the drain-source voltage of the synchronous rectifier with a first slope threshold, and the absolute value of the time-dependent change rate of the drain-source voltage of the synchronous rectifier is compared with the first slope threshold to obtain a second voltage; the absolute value of the change rate of the drain-source voltage of the synchronous rectifier tube along with the time is larger than a first slope threshold value, the second voltage is effective, the slope detection comparison circuit latches the second voltage to obtain a second latch result, and the second latch result is the output voltage of the slope detection comparison circuit;
the logic circuit 140 receives the output voltage of the slope detection comparator 130, and when the output voltage of the integrator circuit 110 is valid, the drain-source voltage of the synchronous rectifier is smaller than the first voltage threshold, and the output voltage of the slope detection comparator 130 is valid, the output of the logic circuit 140 changes from invalid to valid, and the driving circuit 150 drives the synchronous rectifier to conduct.
The invention further provides a flyback circuit, which comprises the synchronous rectification control circuit.
Although the embodiments have been described and illustrated separately, it will be apparent to those skilled in the art that some common techniques may be substituted and integrated between the embodiments, and reference may be made to one of the embodiments not explicitly described, or to another embodiment described.
The above-described embodiments do not limit the scope of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the above-described embodiments should be included in the protection scope of the technical solution.
Claims (10)
1. A primary side conduction judging method comprises the steps of detecting drain-source voltage of a synchronous rectifier tube of a flyback circuit, performing volt-second integration on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube from zero when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is larger than the average value of the drain-source voltage of the synchronous rectifier tube, and finishing integration to obtain first integration when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is smaller than the average value of the drain-source voltage of the synchronous rectifier tube;
when the first integral is greater than a first integral threshold, the primary side is conducted and the transformer current exceeds a first current threshold when the voltage-second integral is represented.
2. A synchronous rectification control method comprises the steps of detecting drain-source voltage of a synchronous rectifier tube of a flyback circuit, performing volt-second integration on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube from zero when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is larger than the average value of the drain-source voltage of the synchronous rectifier tube, and finishing integration to obtain first integration when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is smaller than the average value of the drain-source voltage of the synchronous rectifier tube;
the first integral greater than the first integral threshold value is a necessary condition for the synchronous rectifier tube to be conducted.
3. The synchronous rectification control method of claim 2, wherein: the drain-source voltage of the synchronous rectifier tube is sampled and filtered, and the average value representing the drain-source voltage of the synchronous rectifier tube is output.
4. The synchronous rectification control method of claim 3, wherein: the necessary conduction condition of the synchronous rectifier tube is that the drain-source voltage of the synchronous rectifier tube is smaller than a first voltage threshold value or/and the absolute value of the change rate of the drain-source voltage of the synchronous rectifier tube along with time is larger than a first slope threshold value.
5. A synchronous rectification control circuit detects drain-source voltage of a synchronous rectifier tube of a flyback circuit, when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is larger than the average value of the drain-source voltage of the synchronous rectifier tube, the synchronous rectification control circuit performs volt-second integration on the difference between the instantaneous value of the drain-source voltage of the synchronous rectifier tube and the average value of the drain-source voltage of the synchronous rectifier tube from zero, and when the instantaneous value of the drain-source voltage of the synchronous rectifier tube is smaller than the average value of the drain-source voltage of the synchronous rectifier tube, the integration is finished to obtain first integration;
the first integral greater than the first integral threshold value is a necessary condition for the synchronous rectifier tube to be conducted.
6. The synchronous rectification control circuit of claim 5, wherein: the synchronous rectification control circuit samples the drain-source voltage of the synchronous rectification tube, filters the drain-source voltage of the synchronous rectification tube and outputs an average value representing the drain-source voltage of the synchronous rectification tube.
7. The synchronous rectification control circuit of claim 6, wherein: the synchronous rectification method comprises an integrating circuit, when the instantaneous value of the drain-source voltage of a synchronous rectification tube is larger than the average value of the drain-source voltage of the synchronous rectification tube, the integrating circuit performs volt-second integration on the difference between the instantaneous value of the drain-source voltage of the synchronous rectification tube and the average value of the drain-source voltage of the synchronous rectification tube from zero, when the instantaneous value of the drain-source voltage of the synchronous rectification tube is smaller than the average value of the drain-source voltage of the synchronous rectification tube, the integration is finished to obtain first integration, the first integration and a first integration threshold value are compared to obtain first voltage, when the first integration is larger than the first integration threshold value, the first voltage is effective, otherwise, the first voltage is invalid, the integrating circuit latches the first voltage to obtain a first latching result and clears the volt-second integration, and the first latching result is the output voltage of the integrating circuit.
8. The synchronous rectification control circuit of claim 7, wherein: the synchronous rectifier tube voltage detection circuit comprises a comparison circuit and a logic circuit, wherein the comparison circuit compares drain-source voltage of the synchronous rectifier tube with a first voltage threshold, the logic circuit receives output voltages of the comparison circuit and the integration circuit, and when the output voltage of the integration circuit is effective and the drain-source voltage of the synchronous rectifier tube is smaller than the first voltage threshold, the output of the logic circuit is changed from invalid to effective.
9. The synchronous rectification control circuit of claim 8, wherein: the slope detection comparison circuit compares the absolute value of the change rate of the drain-source voltage of the synchronous rectifier tube along with time with a first slope threshold value to obtain a second voltage; the absolute value of the change rate of the drain-source voltage of the synchronous rectifier tube along with the time is larger than a first slope threshold value, the second voltage is effective, the slope detection comparison circuit latches the second voltage to obtain a second latch result, and the second latch result is the output voltage of the slope detection comparison circuit;
the logic circuit receives the output voltage of the slope detection comparison circuit, and when the output voltage of the integration circuit is effective, the drain-source voltage of the synchronous rectifier tube is smaller than a first voltage threshold value, and the output voltage of the slope detection comparison circuit is effective, the output of the logic circuit is changed from invalid to effective.
10. A flyback circuit, characterized by: the synchronous rectification control circuit of any one of claims 5 to 9 is included, or the synchronous rectification control method of any one of claims 2 to 4 is adopted.
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| CN201910991212.3A CN110798071A (en) | 2019-10-18 | 2019-10-18 | Primary side conduction judgment method, control circuit and flyback circuit |
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| CN201910991212.3A CN110798071A (en) | 2019-10-18 | 2019-10-18 | Primary side conduction judgment method, control circuit and flyback circuit |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111431412A (en) * | 2020-03-16 | 2020-07-17 | 华源智信半导体(深圳)有限公司 | Control method and circuit for preventing bilateral common of switch converter and converter |
| CN112511009A (en) * | 2020-11-26 | 2021-03-16 | 杰华特微电子（杭州）有限公司 | Synchronous rectification control circuit, control method and flyback switching power supply |
| CN113141101A (en) * | 2021-04-08 | 2021-07-20 | 深圳市必易微电子股份有限公司 | Synchronous rectification control circuit, control method and isolated switching power supply |
| CN114301304A (en) * | 2022-01-05 | 2022-04-08 | 浙江大学 | Control method and control circuit of synchronous rectifier tube and switching power supply circuit |
-
2019
- 2019-10-18 CN CN201910991212.3A patent/CN110798071A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111431412A (en) * | 2020-03-16 | 2020-07-17 | 华源智信半导体(深圳)有限公司 | Control method and circuit for preventing bilateral common of switch converter and converter |
| CN111431412B (en) * | 2020-03-16 | 2021-05-11 | 华源智信半导体(深圳)有限公司 | Control method and circuit for preventing bilateral common of switch converter and converter |
| CN112511009A (en) * | 2020-11-26 | 2021-03-16 | 杰华特微电子（杭州）有限公司 | Synchronous rectification control circuit, control method and flyback switching power supply |
| CN112511009B (en) * | 2020-11-26 | 2021-11-09 | 杰华特微电子股份有限公司 | Synchronous rectification control circuit, control method and flyback switching power supply |
| CN113141101A (en) * | 2021-04-08 | 2021-07-20 | 深圳市必易微电子股份有限公司 | Synchronous rectification control circuit, control method and isolated switching power supply |
| CN114301304A (en) * | 2022-01-05 | 2022-04-08 | 浙江大学 | Control method and control circuit of synchronous rectifier tube and switching power supply circuit |
| CN114301304B (en) * | 2022-01-05 | 2023-09-12 | 浙江大学 | Control method and control circuit of synchronous rectifying tube and switching power supply circuit |
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