CN104868759A - Synchronous rectifier driving circuit with low cost - Google Patents
Synchronous rectifier driving circuit with low cost Download PDFInfo
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- CN104868759A CN104868759A CN201510258812.0A CN201510258812A CN104868759A CN 104868759 A CN104868759 A CN 104868759A CN 201510258812 A CN201510258812 A CN 201510258812A CN 104868759 A CN104868759 A CN 104868759A
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Abstract
The invention discloses a synchronous rectifier driving circuit with low cost. The synchronous rectifier driving circuit comprises a synchronous rectifier tube Q3, a synchronous afterflow tube Q1, a rectifier tube grid driving circuit and an afterflow tube grid driving circuit, wherein the rectifier tube grid driving circuit comprises a triode Q4, a diode D3, a resistor R2 and a voltage-stabilizer tube D4, the afterflow tube grid driving circuit comprises a triode Q2, a diode D1, a resistor R1 and a voltage-stabilizer tube D2, the drain electrode of the rectifier tube Q3 is connected with the synonym terminal of a secondary winding of a transformer, and the drain electrode of the afterflow tube Q1 is connected with the dotted terminal of the secondary winding of the transformer. The emitter electrodes of the triodes Q4 and Q2 are respectively connected with the grids of MOSFET tubes Q3 and Q1, the base electrodes of triodes Q4 and Q2 are respectively connected with the cathodes of the voltage-stabilizer tubes D4 and D2, and the collector electrodes of the triodes Q4 and Q2 are respectively connected with the cathodes of the diodes D3 and D1. The synchronous rectifier driving circuit is formed by discrete devices, realizes the functions of special synchronous rectifying driving chips, and works with input voltages of wider scope. The design cost of the circuit is lowered.
Description
Technical field
The present invention relates to field of switch power, particularly a kind of synchronous rectifier drive circuit of low cost.
Background technology
In order to reduce power consumption, the supply power voltage of various high-performance microprocessor is more and more lower, and therefore low-voltage, high-current DC/DC converter becomes important research direction day by day.Due to secondary output big current, rectifier loss becomes the principal element affecting efficiency.Traditional Schottky diode conducting resistance is large, can not meet the designing requirement of high efficiency converter; And adopt the MOSFET pipe of low on-resistance effectively to reduce the wastage, be circuit of synchronous rectification.Synchronous rectifier significantly can improve the conversion efficiency of converter, has been widely used in the design of low-voltage, high-current converter at present.Be different from conventional rectifier diode, synchronous rectifier needs to design special drive circuit, with the turn-on and turn-off of control MOSFET pipe.
The drive circuit of synchronous rectifier can be divided into self-driven and outer driving two kinds of modes.Self-driven mode utilizes the voltage of transformer secondary output winding or auxiliary winding to drive, and is illustrated in figure 1 transformer secondary output winding drive circuit.By the conducting of control MOSFET pipe Q1 and Q2, reduce the rectifier loss of output.Q2 is forward rectifying tube, and Q1 and diode D1 is in parallel, plays the effect of fly-wheel diode.During the conducting of primary switch pipe, transformer secondary output winding output voltage, forward rectifying tube Q2 conducting; When primary switch pipe turns off, the resetting voltage of transformer applies negative voltage at the grid source electrode of Q2 and causes Q2 to turn off, and makes Q1 conducting afterflow at the grid source electrode applying positive voltage of Q1.As seen from Figure 1, self-driven mode circuit is simple, and cost is low.But the admissible maximum voltage in MOSFET grid source limits the input voltage range of converter, for wide region input voltage must regulating circuit to protect grid.And self-driven mode also has following shortcoming: there is dead band, drive waveforms is poor, driving voltage sequential is uncontrollable.
Outer driving working method adopts special synchronous rectifier driving chip to build drive circuit, exports the drive singal with transformer-secondary voltage corresponding time sequence.Drive singal voltage magnitude is constant, and not with the change of transformer-secondary voltage amplitude, drive waveforms is good.Outer type of drive can make up the shortcoming of self-driven mode, provides high-quality outputting drive voltage, but the employing of special driving chip improves the design cost of circuit.In order to reduce costs, the scheme of discrete device can be adopted to carry out alternative special driving chip, the art of this patent launches research based on such background.
Summary of the invention
The object of the invention is the synchronous rectifier drive circuit designing a kind of low cost.
To achieve these goals, embodiments provide a kind of synchronous rectifier drive circuit of low cost, comprise a synchronous rectifier, a synchronous continued flow tube, rectifying tube gate driver circuit and continued flow tube gate driver circuit, wherein:
Described synchronous rectifier comprises MOSFET pipe Q3.
Described synchronous freewheeling pipe comprises MOSFET pipe Q1.
Described rectifying tube gate driver circuit comprises triode Q4, diode D3, resistance R2 and voltage-stabiliser tube D4.
Described continued flow tube gate driver circuit comprises triode Q2, diode D1, resistance R1 and voltage-stabiliser tube D2.
Further, the drain electrode of described rectifying tube Q3 connects the different name end of transformer secondary output winding; The drain electrode of described continued flow tube Q1 connects the Same Name of Ends of transformer secondary output winding.
Further, the source ground of described rectifying tube Q3; The source ground of described continued flow tube Q1.
Further, the emitter of described triode Q4 connects the grid of rectifying tube Q3; The base stage of described triode Q4 connects the negative electrode of voltage-stabiliser tube D4; The collector electrode of described triode Q4 connects the negative electrode of diode D3.
Further, the emitter of described triode Q2 connects the grid of continued flow tube Q1; The base stage of described triode Q2 connects the negative electrode of voltage-stabiliser tube D2; The collector electrode of described triode Q2 connects the negative electrode of diode D1.
Further, the anode of described diode D3 connects the grid of rectifying tube Q3; The anode of described diode D1 connects the grid of continued flow tube Q1.
Further, described rectifying tube Q3 adopts N-channel MOS FET pipe; Described continued flow tube Q1 adopts N-channel MOS FET pipe.
Further, described triode Q4 adopts NPN type triode; Described triode Q2 adopts NPN type triode.
Further, described voltage-stabiliser tube D2 adopts 5.1V voltage stabilizing didoe; Described voltage-stabiliser tube D4 adopts 5.1V voltage stabilizing didoe.
Embodiments provide a kind of synchronous rectifier drive circuit of low cost.Drive circuit is built by discrete device and is formed, and can work in the input voltage of wide region.Compared to the prior art, the scheme that the present invention is based on discrete device can realize the function of special synchronous rectification driving chip, reduces the design cost of circuit simultaneously.
Accompanying drawing explanation
In order to make the object, technical solutions and advantages of the present invention clearly, below in conjunction with accompanying drawing, the present invention is described in further detail, wherein:
Fig. 1 is the schematic diagram of transformer secondary output winding driving circuit;
Fig. 2 is the schematic diagram of synchronous rectifier drive circuit of the present invention.
Embodiment
Below in conjunction with accompanying drawing, method of the present invention is described in further detail.
The schematic diagram of the synchronous rectifier drive circuit that Fig. 2 provides for the embodiment of the present invention.As shown in the figure, embodiments provide a kind of synchronous rectifier drive circuit of low cost, comprise a synchronous rectifier, a synchronous continued flow tube, rectifying tube gate driver circuit and continued flow tube gate driver circuit, wherein:
Described synchronous rectifier comprises MOSFET pipe Q3.
Described synchronous freewheeling pipe comprises MOSFET pipe Q1.
Described rectifying tube gate driver circuit comprises triode Q4, diode D3, resistance R2 and voltage-stabiliser tube D4.
Described continued flow tube gate driver circuit comprises triode Q2, diode D1, resistance R1 and voltage-stabiliser tube D2.
Further, the drain electrode of described rectifying tube Q3 connects the different name end of transformer secondary output winding; The drain electrode of described continued flow tube Q1 connects the Same Name of Ends of transformer secondary output winding.
Further, the source ground of described rectifying tube Q3; The source ground of described continued flow tube Q1.
Further, the emitter of described triode Q4 connects the grid of rectifying tube Q3; The base stage of described triode Q4 connects the negative electrode of voltage-stabiliser tube D4; The collector electrode of described triode Q4 connects the negative electrode of diode D3.
Further, the emitter of described triode Q2 connects the grid of continued flow tube Q1; The base stage of described triode Q2 connects the negative electrode of voltage-stabiliser tube D2; The collector electrode of described triode Q2 connects the negative electrode of diode D1.
Further, the anode of described diode D3 connects the grid of rectifying tube Q3; The anode of described diode D1 connects the grid of continued flow tube Q1.
Further, described rectifying tube Q3 adopts N-channel MOS FET pipe; Described continued flow tube Q1 adopts N-channel MOS FET pipe.
Further, described triode Q4 adopts NPN type triode; Described triode Q2 adopts NPN type triode.
Further, described voltage-stabiliser tube D2 adopts 5.1V voltage stabilizing didoe; Described voltage-stabiliser tube D4 adopts 5.1V voltage stabilizing didoe.
Drive circuit in the embodiment of the present invention is built by discrete component, can adapt to the input voltage of wide region.During the conducting of primary switch pipe, transformer secondary output exports positive voltage, and base current flows through R2, triode Q4 conducting, drives rectifying tube Q3 to open, and primary input Energy Transfer is to secondary and be stored in magnetizing inductance.Gate drive voltage is limited in about 5V by diode D4, prevents grid voltage off-rating.When primary switch pipe turns off, transformer secondary output exports negative voltage, and rectifying tube Q3 closes, and primary energy is to secondary Transmission, and continued flow tube Q1 opens, and maintains the power output needed for load.Diode D1 and D3 shields.Rectifying tube and Q3 continued flow tube Q1 have very little gate inductance, and the conversion between opening and turning off is very fast.For more powerful MOSFET, the general PNP transistor that adopts carries out grid capacitance decoupling to improve switching speed to winding.
The general expression of converter conversion efficiency is:
Wherein P
ofor power output, P
lossfor not comprising the circuit loss of rectifier loss, P
recfor rectifier loss.
For traditional Schottky diode rectifier system, rectifier loss is P
sT, then conversion efficiency is:
For circuit of synchronous rectification, rectifier loss is for being P
sR, then conversion efficiency is:
This can obtain synchronous rectification efficiency eta
sTwith Schottky rectification efficiency eta
sTbetween relational expression:
The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, obviously, those skilled in the art can carry out various change and modification to the present invention and not depart from the spirit and scope of the present invention.Like this, if these amendments of the present invention and modification belong within the scope of the claims in the present invention and equivalent technologies thereof, then the present invention is also intended to comprise these change and modification.
Claims (8)
1. a synchronous rectifier drive circuit for low cost, is characterized in that: comprise a synchronous rectifier, a synchronous continued flow tube, rectifying tube gate driver circuit and continued flow tube gate driver circuit; Described synchronous rectifier comprises MOSFET pipe Q3; Described synchronous freewheeling pipe comprises MOSFET pipe Q1; Described rectifying tube gate driver circuit comprises triode Q4, diode D3, resistance R2 and voltage-stabiliser tube D4; Described continued flow tube gate driver circuit comprises triode Q2, diode D1, resistance R1 and voltage-stabiliser tube D2.
2. drive circuit according to claim 1, is characterized in that: the drain electrode of described rectifying tube Q3 connects the different name end of transformer secondary output winding; The drain electrode of described continued flow tube Q1 connects the Same Name of Ends of transformer secondary output winding; The source ground of described rectifying tube Q3; The source ground of described continued flow tube Q1.
3. drive circuit according to claim 1, is characterized in that: the emitter of described triode Q4 connects the grid of rectifying tube Q3; The base stage of described triode Q4 connects the negative electrode of voltage-stabiliser tube D4; The collector electrode of described triode Q4 connects the negative electrode of diode D3.
4. drive circuit according to claim 1, is characterized in that: the emitter of described triode Q2 connects the grid of continued flow tube Q1; The base stage of described triode Q2 connects the negative electrode of voltage-stabiliser tube D2; The collector electrode of described triode Q2 connects the negative electrode of diode D1.
5. drive circuit according to claim 1, is characterized in that: the anode of described diode D3 connects the grid of rectifying tube Q3; The anode of described diode D1 connects the grid of continued flow tube Q1.
6. the drive circuit according to the arbitrary claim of claim 1 to 2, is characterized in that: described rectifying tube Q3 adopts N-channel MOS FET pipe; Described continued flow tube Q1 adopts N-channel MOS FET pipe.
7. the drive circuit according to the arbitrary claim of claims 1 to 3, is characterized in that: described triode Q4 adopts NPN type triode; Described triode Q2 adopts NPN type triode.
8. the drive circuit according to the arbitrary claim of Claims 1-4, is characterized in that: described voltage-stabiliser tube D2 adopts 5.1V voltage stabilizing didoe; Described voltage-stabiliser tube D4 adopts 5.1V voltage stabilizing didoe.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510258812.0A CN104868759A (en) | 2015-05-20 | 2015-05-20 | Synchronous rectifier driving circuit with low cost |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510258812.0A CN104868759A (en) | 2015-05-20 | 2015-05-20 | Synchronous rectifier driving circuit with low cost |
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| CN104868759A true CN104868759A (en) | 2015-08-26 |
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| CN201510258812.0A Pending CN104868759A (en) | 2015-05-20 | 2015-05-20 | Synchronous rectifier driving circuit with low cost |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1675821A (en) * | 2002-08-12 | 2005-09-28 | 奥地利西门子股份有限公司 | Dc-to-dc converter |
| CN201608647U (en) * | 2010-02-11 | 2010-10-13 | 北京星原丰泰电子技术有限公司 | Synchronous MOSFET grid voltage clamp driving circuit for forward converter |
| CN102217181A (en) * | 2008-11-14 | 2011-10-12 | 伟创力国际美国公司 | Driver for a synchronous rectifier and power converter employing the same |
-
2015
- 2015-05-20 CN CN201510258812.0A patent/CN104868759A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1675821A (en) * | 2002-08-12 | 2005-09-28 | 奥地利西门子股份有限公司 | Dc-to-dc converter |
| CN102217181A (en) * | 2008-11-14 | 2011-10-12 | 伟创力国际美国公司 | Driver for a synchronous rectifier and power converter employing the same |
| CN201608647U (en) * | 2010-02-11 | 2010-10-13 | 北京星原丰泰电子技术有限公司 | Synchronous MOSFET grid voltage clamp driving circuit for forward converter |
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Application publication date: 20150826 |