CN109194098A - A kind of synchronous rectification sample circuit - Google Patents
A kind of synchronous rectification sample circuit Download PDFInfo
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- CN109194098A CN109194098A CN201811273293.5A CN201811273293A CN109194098A CN 109194098 A CN109194098 A CN 109194098A CN 201811273293 A CN201811273293 A CN 201811273293A CN 109194098 A CN109194098 A CN 109194098A
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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
-
- 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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- 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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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Rectifiers (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention discloses a kind of synchronous rectification sample circuits, applied to flyback converter, it is characterized by comprising an impedance variations circuits, one end of impedance variations circuit is used to connect the drain electrode of devices SR, the other end of impedance variations circuit is used to connect the sampling pin of synchronous rectification control chip, impedance variations circuit is in low resistive state when devices SR is opened, impedance variations circuit is in high-impedance state when devices SR shutdown, sample circuit of the invention reduces the voltage value of synchronous rectification IC sampling pin while not influencing the normal sample of synchronous rectification IC, so as to widen the applied voltage range of conventional synchronous rectification IC.
Description
Technical field
The present invention relates to a kind of circuits for improving sampling pressure resistance, are especially for use in a kind of raising core in synchronous rectification field
The circuit of piece sampling pressure resistance.
Background technique
Inverse excitation type converter is using very frequently in field of switch power, because its topology is simple, scheme is mature, cost
It is low, function admirable, so the occasion use within 100W is very suitable to, but with the small size of electronic equipment, Gao Gong
The densification development of rate, it is desirable that efficiency is higher and higher, and conventional its loss value of output rectifier diode rectification scheme is equal to output
For electric current multiplied by the forward voltage drop of diode, forward voltage drop size is related to semiconductor technology, therefore its forward voltage drop is generally all
In 0.4-0.6V or so, it is possible to calculate the loss value of output rectifier diode, it is assumed that it is a 5A output translator, it is defeated
Just in 2W-3W or so, this will cause very big heat for the loss of rectifier diode out, to need to increase cooling fin, therefore
Volume rises again, and uses synchronous rectification scheme, because forward voltage drop can be reduced to 0.1V hereinafter, therefore can mention significantly
High overall efficiency does not need additional radiator, so the scheme of synchronous rectification cooperation circuit of reversed excitation is increasingly by blueness
It looks at, but during using synchronous rectification scheme, has used metal-oxide-semiconductor, therefore just need driving circuit, general driving
Circuit has a two major classes, and one kind is self-powered, and one kind is that it drives, the scheme of self-powered have one it is apparent the disadvantage is that the meeting under light condition
Synchronous rectifier occurs and primary side main switch is common, therefore it is more severe to generate heat, light-load efficiency is excessively poor, therefore less real
With in the application especially in adapter often with underloading, so most schemes is using one in practical applications
Synchronous rectification control chip drives synchronous rectifier, because this method, which can be controlled accurately, turns on and off the moment, protects
Card devices and primary side switch pipe will not occur common, while realize synchronous rectification.
It is as shown in Figure 1 common counter exciting synchronous rectification schematic block circuit diagram, which includes input circuit, clamp circuit,
Transformer T1, primary-side-control IC circuit U 1, main power MOS pipe S1, secondary side devices SR, synchronous rectification IC circuit U 2,
Output circuit, wherein input circuit is made of input capacitance C1, and output circuit is made of output capacitance C6, main power MOS pipe S1
It include parasitic body diode Ds3 and parasitic capacitance comprising parasitic capacitance Cds1 and parasitic diode Ds1, devices SR
The cathode VIN- of the cathode connection input voltage of anode connection the input voltage anode VIN+, capacitor C1 of Cds3, capacitor C1, clamper
Circuit is used to absorb the peak voltage of transformer leakage inductance generation, its one end is connected to the drain electrode of main power tube S1, and the other end connects
It connects in input voltage anode, primary-side-control IC circuit U 1 connects the grid of main power MOS pipe S1, the source electrode of main power MOS pipe S1
Connection connects input anode VIN+ with reference to ground, the Same Name of Ends of transformer T1 primary side, and transformer T1 primary side different name end connects main function
Rate metal-oxide-semiconductor S1 drain electrode and clamp circuit one end, transformer T1 pair side different name end connect output head anode Vo+, and transformer secondary is same
The drain electrode of name end connection devices SR, while being connected to the sample port VD of synchronous rectification IC circuit U 2, synchronous rectification
The port GATE of the grid connection synchronous rectification IC circuit U 2 of metal-oxide-semiconductor SR, the port the VSS auxiliary connection side of synchronous rectification IC circuit U 2
With reference to ground, the positive Vout+ of the anode connection output end of capacitor C6, the cathode connection cathode of output end of capacitor C6 i.e. secondary
Side is with reference to ground.
This synchronous rectification control chip (i.e. U2) in circuit shown in Fig. 1 can generally include a sampling pin (can also
To be referred to as port, " pin " and " port " of the invention is same term), which is denoted as VD pin, the sampling
Pin needs to be connected to the drain electrode of devices SR, reference of usual synchronous rectification control chip VSS can be connected to synchronize it is whole
The source electrode of metal-oxide-semiconductor SR is flowed, therefore the voltage of VD pin to reference ground VSS are just devices SR drain-source voltage, MOS
It is to have between the hourglass source electrode of pipe SR existing for a parasitic diode Ds3, anode connects source electrode, cathode connection drain electrode.
It is illustrated in figure 2 the corresponding waveform correlation of the common counter exciting synchronous rectification circuit of Fig. 1, as the main power MOS pipe S1 of primary side
When shutdown, winding voltage is reversed, and devices SR parasitic body diode forward direction is open-minded, and drain-source voltage becomes at this time
For negative sense, synchronous rectification controls chip by detecting the negative voltage, opens devices after negative pressure reaches setting value
SR, turn-off criterion have different condition according to different working methods, after turning off devices SR, the main power MOS of primary side
Pipe S1 is open-minded, at this time vice-side winding voltage reversal, and drain-source voltage becomes positive pressure, and the size of positive pressure is VIN/Nps+Vo, usually
In the case of output be 19V adapter turn ratio Nps be 5 or so because the turn ratio will result in greatly the voltage stress of primary side metal-oxide-semiconductor again
It is excessively high, therefore in the global input voltage range application of 85-264VAC input, the voltage stress on synchronous rectifier can reach
264*1.414/5+19=93.6V while also need peak voltage caused by considering leakage inductance, so voltage stress is usually more than
There are many 100V or more, but the device that reach so value of high voltage in semiconductor device technology is fewer, can only generally reach
Arriving 50V or so, it is necessary to portion integrates a high-voltage MOS pipe in the chip, but after integrated high voltage metal-oxide-semiconductor, it on the one hand can be significantly
Increase chip area, causes chip cost high, the high-voltage MOS pipe built in still further aspect can generate a two parasitic poles
Pipe, this diode, which is equivalent to, to be connected in parallel between the drain electrode of devices and the substrate of chip, therefore in synchronous rectifier
Also an electric current can be generated when opening and flows through the parasitic diode of built-in metal-oxide-semiconductor, therefore substrate can be allowed to walk electric current, and substrate
It is unable to the leakage of electricity, therefore will cause the control disorder of synchronous rectification chip, therefore there are major hidden dangers.
Summary of the invention
Have in view of that, the technical problem to be solved in the present invention is to provide a kind of synchronous rectification sample circuit, reduction synchronizes whole
The pressure resistance born required for flow control chip.
The voltage of synchronous rectification control chip sampling pin sampling of the present invention is the leakage of devices service time section
Source voltage, voltage is low-down at this time, only several hundred millivolts, and adopting of opening of chip interior control devices
Sample threshold value only has tens millivolts, therefore the accuracy in order to guarantee sampling, it is necessary to assure and sampling pin is the state of a low-resistance,
But very high voltage can be born after devices shutdown in the state of low-resistance at that time, so in order to improve sampling
Pin pressure resistance, it is necessary to sampling pin is divided, but cannot influence to sample again, so tradition simply in sampling pin and
Synchronous rectifier sources connected in parallel voltage-stabiliser tube be it is infeasible, voltage-stabiliser tube can be allowed to burn out, meanwhile, in sampling pin and synchronous rectifier
One resistance of series connection is also not all right between drain electrode, sampling can be allowed to cannot proceed normally.
Obstacle in view of the above technology, present inventor propose a kind of completely new technical concept: using an impedance
The circuit of variation is connected between sampling pin and devices drain electrode, allows it when devices are opened
In a low resistive state, it is in a high-impedance state when synchronous rectifier shutdown, to propose skill of the invention
Art scheme, it is specific as follows.
A kind of synchronous rectification sample circuit is applied to flyback converter, it is characterised in that: including an impedance variations circuit,
One end of impedance variations circuit is used to connect the drain electrode of devices SR, and the other end of impedance variations circuit is for connecting
Synchronous rectification controls the sampling pin of chip, impedance the turning on and off according to devices SR of impedance variations circuit
Different, impedance variations circuit is in low resistive state when devices SR is opened, in devices
Impedance variations circuit is in high-impedance state when SR is turned off.Its medium or low resistance refers to milliohm rank, and high resistant refers to mega-ohms
Not.
It is a metal-oxide-semiconductor S2 as a kind of specific embodiment of impedance variations circuit, metal-oxide-semiconductor S2 includes parasitic capacitance
The drain electrode of Cds2 and parasitic diode Ds2, metal-oxide-semiconductor S2 are for connecting the drain electrode of devices SR, the source electrode of metal-oxide-semiconductor S2
For connecting the sampling pin of synchronous rectification control chip, the grid of metal-oxide-semiconductor S2 is used to connect the positive Vout+ of output end.
As a kind of specific embodiment of impedance variations circuit, including metal-oxide-semiconductor S2, resistance R1 and zener diode
DZ, metal-oxide-semiconductor S2 include parasitic capacitance Cds2 and parasitic diode Ds2, and the drain electrode of metal-oxide-semiconductor S2 is for connecting devices
The drain electrode of SR, the source electrode of metal-oxide-semiconductor S2 are used to connect the sampling pin of synchronous rectification control chip, and the grid of metal-oxide-semiconductor S2 connects electricity
One end of R1 is hindered, the other end of resistance R1 is used to connect the positive Vout+ of output end, and the grid of metal-oxide-semiconductor S2 is also connected with pressure stabilizing two
The cathode of pole pipe DZ, the anode of zener diode DZ is for connecting secondary side reference.
It is a metal-oxide-semiconductor S2 as a kind of specific embodiment of impedance variations circuit, metal-oxide-semiconductor S2 includes parasitic capacitance
The drain electrode of Cds2 and parasitic diode Ds2, metal-oxide-semiconductor S2 are for connecting the drain electrode of devices SR, the source electrode of metal-oxide-semiconductor S2
For connecting the sampling pin of synchronous rectification control chip, the grid of metal-oxide-semiconductor S2 is used to connect synchronous rectification control chip
GATE pin.
It is of the invention that the specific working principle is as follows:
When primary-side-control IC, which controls main power MOS pipe S1, to be opened, transformer primary side inductance excitation stores energy, secondary
Side devices SR shutdown, when primary side main power MOS pipe S1 shutdown, main power MOS is given in primary side inductance afterflow
Pipe S1 parasitic capacitance Cds1 charging, transformer winding voltage reversal, secondary side devices SR parasitic capacitance Cds3 electric discharge,
Reverse charging after capacitor Cds3 discharges into 0V, body diode Ds3 reaches open threshold value after it is open-minded, after opening impedance variations electricity
Road reduces impedance, and VD pin detects devices SR drain-source voltage, detects that drain-source voltage reaches synchronous rectification IC
Negative sense threshold value after, synchronous rectification IC control driving GATE it is open-minded, the shutdown of synchronous rectification can not according to different operating modes
Equally, synchronous rectification IC control GATE is turned off after reaching turn-off criterion, after shutdown before the main power MOS pipe S1 of primary side is opened
The parasitic capacitance of primary side inductance and main power MOS pipe S1 occur resonance, when main power MOS pipe S1 is opened, transformer secondary around
Group voltage becomes lower just upper negative, and devices SR drain-source voltage becomes VIN/Nps+Vo, in synchronous rectifier shutdown
When, impedance variations circuit has been changed to high impedance, therefore the VD pin voltage of synchronous rectification IC is synchronous rectifier leakage at this time
Source voltage subtracts the partial pressure above impedance variations circuit, greatly reduces the VD pin voltage of synchronous rectification IC, improves same
The pressure voltage of step rectification IC sampling.
The beneficial effects of the present invention are:
1, the normal sample of synchronous rectification IC is not influenced；
2, the voltage value of synchronous rectification IC sampling pin is reduced.
3, the applied voltage range of the conventional synchronous rectification IC widened.
Detailed description of the invention
Fig. 1 is common counter exciting synchronous rectification schematic block circuit diagram；
Fig. 2 is the corresponding waveform correlation of the common counter exciting synchronous rectification circuit of Fig. 1；
Fig. 3 is the principle of the present invention block diagram；
Fig. 4 is the functional block diagram of first embodiment proposed by the present invention；
Fig. 5 is the corresponding waveform correlation of first embodiment of the invention；
Fig. 6 is the functional block diagram of second embodiment proposed by the present invention；
Fig. 7 is the corresponding waveform correlation of second embodiment of the invention；
Fig. 8 is the functional block diagram of 3rd embodiment proposed by the present invention；
Fig. 9 is the corresponding waveform correlation of third embodiment of the invention.
Specific embodiment
Fig. 3 is the principle of the present invention block diagram, is in the drain electrode of devices SR and synchronous whole with Fig. 1 difference
An impedance variations circuit is connected between the sampling pin of flow control chip, working principle has been analyzed above, and this will not be repeated here.
In order to enable those skilled in the art more fully understands the present invention, carried out below with reference to specific embodiment detailed
Explanation.
Embodiment one
Fig. 4 is first embodiment of the invention functional block diagram, and impedance variations circuit therein is a metal-oxide-semiconductor S2, metal-oxide-semiconductor S2 packet
The drain electrode of the drain electrode connection devices SR of Cds2 containing parasitic capacitance and parasitic diode Ds2, metal-oxide-semiconductor S2, metal-oxide-semiconductor S2
Source electrode connection synchronous rectification control chip sampling pin, metal-oxide-semiconductor S2 grid connection flyback converter output end anode
Vout+, other connection relationships are identical as Fig. 1 and Fig. 3, and this will not be repeated here.
Such as Fig. 5, some synchronous rectification Vital Voltage waveforms are given, when main power MOS pipe is just opened, S2 is still
In low resistive state, so VD pin voltage can increase, when VD pin voltage be increased to Vout-VGSth (S2's opens threshold value,
Generally 4V or so) after, according to the working principle of metal-oxide-semiconductor, metal-oxide-semiconductor enters cut-off region, turns off naturally, subsequently becomes a high resistant
State, VD pin voltage do not continue to increase, and the voltage of VD pin is effectively reduced at the drain-source both ends of S2 in extra voltage landing
Size, the drain-source voltage decline of devices after the shutdown of main power MOS pipe, when under devices drain voltage
After dropping to Vout-VGSth, S2 is open-minded, becomes low resistive state, devices drain voltage, which further decreases, eventually to be made
Body diode Ds3 conducting, drain-source voltage become negative pressure, and VD pin is got GATE after detecting threshold value of the negative pressure more than setting, controlled
Devices processed are open-minded, realize synchronous rectification.
Embodiment two
For the higher occasion of output voltage, metal-oxide-semiconductor grid voltage may not be able to be born, and Fig. 6 is that the present invention second is implemented
Example functional block diagram, impedance variations circuit therein include metal-oxide-semiconductor S2, resistance R1 and zener diode DZ, and metal-oxide-semiconductor S2 includes parasitism
The drain electrode of capacitor Cds2 and parasitic diode Ds2, metal-oxide-semiconductor S2 for connecting the drain electrode of devices SR, metal-oxide-semiconductor S2's
Source electrode is used to connect the sampling pin of synchronous rectification control chip, and the grid of metal-oxide-semiconductor S2 connects one end of resistance R1, resistance R1's
The other end is used to connect the positive Vout+ of flyback converter output end, and the grid of metal-oxide-semiconductor S2 is also connected with the yin of zener diode DZ
Pole, the anode of zener diode DZ is for connecting secondary side reference, other connection relationships to be identical as Fig. 1 and Fig. 3, do not go to live in the household of one's in-laws on getting married herein
It states.
Such as Fig. 7, some synchronous rectification Vital Voltage waveforms are given, when main power MOS pipe is just opened, S2 is still
In low resistive state, so VD pin voltage can increase, when VD pin voltage be increased to Vz-VGSth (S2's opens threshold value, one
As for 4V or so) after, according to the working principle of metal-oxide-semiconductor, metal-oxide-semiconductor enters cut-off region, and shutdown, subsequently becomes a high resistant shape naturally
State, VD pin voltage do not continue to increase, and for extra voltage landing at the drain-source both ends of S2, the voltage that VD pin is effectively reduced is big
It is small, the drain-source voltage decline of devices after the shutdown of main power MOS pipe, when devices drain voltage declines
To after Vz-VGSth, S2 is open-minded, becomes low resistive state, devices drain voltage, which further decreases, eventually makes body two
Pole pipe Ds3 conducting, drain-source voltage become negative pressure, and VD pin gets GATE after detecting threshold value of the negative pressure more than setting, and control is same
Step rectification metal-oxide-semiconductor is open-minded, realizes synchronous rectification, compares embodiment one, which can arrive VD pin voltage clamper
A controllable range, can be realized using the voltage-stabiliser tube Dz of different pressure resistances.
Embodiment three
Fig. 8 is first embodiment of the invention functional block diagram, and impedance variations circuit therein is a metal-oxide-semiconductor S2, metal-oxide-semiconductor S2 packet
The drain electrode of Cds2 containing parasitic capacitance and parasitic diode Ds2, metal-oxide-semiconductor S2 are for connecting the drain electrode of devices SR, MOS
The source electrode of pipe S2 is used to connect the sampling pin of synchronous rectification control chip, and the grid of metal-oxide-semiconductor S2 is for connecting synchronous rectification control
The GATE pin of coremaking piece, other connection relationships are identical as Fig. 1 and Fig. 3, and this will not be repeated here.
Such as Fig. 9, some synchronous rectification Vital Voltage waveforms are given, when main power MOS pipe is just opened, S2 is still
In low resistive state, so VD pin voltage can increase, (threshold of the VGSth of pipe is exhausted when VD pin voltage is increased to-VGSth
Value is negative value) after (S2's opens threshold value, generally -4V or so), according to the working principle of metal-oxide-semiconductor, metal-oxide-semiconductor enters cut-off region,
Naturally it turns off, subsequently becomes a high-impedance state, VD pin voltage does not continue to increase, drain-source of the extra voltage landing in S2
The voltage swing of VD pin is effectively reduced in both ends, the drain-source voltage decline of devices after the shutdown of main power MOS pipe,
After devices drain voltage drops to-VGSth, because GATE is not opened S2 is open-minded at this time, GATE is
Zero volt, therefore it is open-minded to exhaust pipe, becomes low resistive state, devices drain voltage, which further decreases, eventually makes body two
Pole pipe Ds3 conducting, drain-source voltage become negative pressure, and VD pin gets GATE after detecting threshold value of the negative pressure more than setting, and control is same
Step rectification metal-oxide-semiconductor is open-minded, realizes synchronous rectification.
The above is only the preferred embodiments of the disclosure to know according to above content according to the ordinary skill of this field
Knowledge and customary means, under the premise of not departing from the thought of the above-mentioned increase impedance variations circuit of the present invention, circuit of the invention is also
Other embodiments；Therefore the present invention can also make the modification, replacement or change of other diversified forms, all fall within the present invention
Within rights protection scope.
Claims (4)
1. a kind of synchronous rectification sample circuit is applied to flyback converter, it is characterised in that: including an impedance variations circuit, resistance
One end of anti-varying circuit is used to connect the drain electrode of devices SR, and the other end of impedance variations circuit is same for connecting
The sampling pin of step rectification control chip, impedance having turned on and off according to devices SR of impedance variations circuit
Institute is different, and impedance variations circuit is in low resistive state when devices SR is opened, in devices SR
Impedance variations circuit is in high-impedance state when shutdown.
2. synchronous rectification sample circuit according to claim 1, it is characterised in that: impedance variations circuit is a metal-oxide-semiconductor S2,
Metal-oxide-semiconductor S2 includes parasitic capacitance Cds2 and parasitic diode Ds2, and the drain electrode of metal-oxide-semiconductor S2 is for connecting devices SR's
Drain electrode, the source electrode of metal-oxide-semiconductor S2 are used to connect the sampling pin of synchronous rectification control chip, and the grid of metal-oxide-semiconductor S2 is defeated for connecting
The positive Vout+ of outlet.
3. synchronous rectification sample circuit according to claim 1, it is characterised in that: impedance variations circuit include metal-oxide-semiconductor S2,
Resistance R1 and zener diode DZ, metal-oxide-semiconductor S2 include parasitic capacitance Cds2 and parasitic diode Ds2, and the drain electrode of metal-oxide-semiconductor S2 is used for
The drain electrode of devices SR is connected, the source electrode of metal-oxide-semiconductor S2 is used to connect the sampling pin of synchronous rectification control chip, MOS
One end of the grid connection resistance R1 of pipe S2, the other end of resistance R1 are used to connect the positive Vout+ of output end, metal-oxide-semiconductor S2's
Grid is also connected with the cathode of zener diode DZ, and the anode of zener diode DZ is for connecting secondary side reference.
4. synchronous rectification sample circuit according to claim 1, it is characterised in that: impedance variations circuit is a metal-oxide-semiconductor S2,
Metal-oxide-semiconductor S2 includes parasitic capacitance Cds2 and parasitic diode Ds2, and the drain electrode of metal-oxide-semiconductor S2 is for connecting devices SR's
Drain electrode, the source electrode of metal-oxide-semiconductor S2 are used to connect the sampling pin of synchronous rectification control chip, and the grid of metal-oxide-semiconductor S2 is same for connecting
The GATE pin of step rectification control chip.
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| CN201811273293.5A CN109194098A (en) | 2018-10-30 | 2018-10-30 | A kind of synchronous rectification sample circuit |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111262444A (en) * | 2020-02-20 | 2020-06-09 | 连云港杰瑞电子有限公司 | Synchronous rectification control system and control method for secondary side resonance active clamping flyback |
| CN112787512A (en) * | 2019-11-04 | 2021-05-11 | 海信视像科技股份有限公司 | Display device and control circuit |
| EP4047804A1 (en) * | 2021-02-10 | 2022-08-24 | Huawei Digital Power Technologies Co., Ltd. | Converter and power adapter |
| CN116780862A (en) * | 2023-08-21 | 2023-09-19 | 南京杰芯源科技有限公司 | Power supply chopper circuit suitable for synchronous rectification of secondary side of flyback converter |
| CN116887478A (en) * | 2023-08-01 | 2023-10-13 | 广州威博智能科技股份有限公司 | Synchronous rectification automobile LED lamp driving circuit |
| US11900855B2 (en) | 2019-11-04 | 2024-02-13 | Hisense Visual Technology Co., Ltd. | Display apparatus |
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