A kind of synchronous rectification power supply circuit with absorption functionTechnical field
The utility model belongs to electronic circuit technology field, and in particular to a kind of synchronous rectification power supply with absorption functionCircuit.
Background technique
Power supply is the important component of various electronic equipments, it like human body heart, just for all electric class equipmentOften operation provides power.With the fast development of various electronic equipments, electric appliance, the quality power stable to high efficiency, performanceThere is great demand.Switching Power Supply is the time ratio that control switch pipe turns on and off using modern power electronics technology,A kind of power supply stabilized the output voltage is maintained, Switching Power Supply is generally made of pulse width modulation (PWM) control IC and MOSFET.It with the development of power electronics technology and innovates, so that switch power technology is also innovated constantly.Currently, Switching Power Supply is with smallType, light weight and efficient feature are widely used almost all of electronic equipment, are current electronics and information industry rapid developmentsA kind of indispensable power mode.
There are two types of modern Switching Power Supplies: one is direct-current switch power supplies；Another kind is alternating-current switch power supply.Dc switch electricityThe core in source is DC/DC converter.Therefore the classification of direct-current switch power supply is to rely on DC/DC converter to classify.That is,Classification and the classification of DC/DC converter of direct-current switch power supply be it is essentially identical, the classification of DC/DC converter is basicallyThe classification of direct-current switch power supply.Whether direct current DC/DC converter has electrical isolation that can be divided into two classes by between input and output:One kind is the referred to as isolated DC/DC converter for having isolation；Another kind of is that the non-isolated DC/DC that is known as not being isolated is convertedDevice.Isolated DC/DC converter can also classify by the number of active power device.The DC/DC converter of single tube has normal shockTwo kinds of formula (Forward) and inverse-excitation type (Flyback).Two-tube DC/DC converter has double tube positive exciting formula (DoubleTransistorForward Converter), double-transistor flyback formula (Double TransistrFlyback Converter), push-pull type (Push-Pull Converter) and four kinds of semibridge system (Half-Bridge Converter).Four pipe DC/DC converters are exactly full-bridge DC/DC converter (Full-Bridge Converter).
As shown in figs. 1 and 3, in existing inverse-excitation type switch power-supply (single switch flyback formula or double-transistor flyback formula), when PWM believesNumber control MOSFET shutdown when, just have a high frequency spikes voltage appear in its drain electrode on.This is because main transformerCaused by leakage inductance and MOSFET output capacitance resonance, MOSFET may be punctured in the upper excessively high voltage of drain electrode；High frequency spikes electricityPressure is coupled on secondary side rectification circuit by main transformer, can equally rectification circuit be caused to damage.One must just be increased thusAdjunct circuit clamps down on this high frequency spikes voltage.Conventional absorption circuit is by the energy absorption of high frequency spikes voltage and to pass through hairThe mode of heat consumes, and causes energy loss.Also, the power supply of the synchronous rectifying controller in existing inverse-excitation type switch power-supplyIt is realized using the auxiliary winding of main transformer.Auxiliary winding increases the coiling difficulty of main transformer, while can also make main transformer pressureThe leakage inductance of device increases, and in turn, high frequency spikes voltage also increases with it.
Utility model content
In order to solve the above problems existing in the present technology, the utility model aim is to provide a kind of with absorption functionSynchronous rectification power supply circuit.The utility model is by setting first diode, first capacitor and the second capacitor, so that this realityThe output capacitance resonance of the leakage inductance of main transformer and the MOSFET of pwm signal control is produced with novel synchronous rectification power supply circuitRaw high frequency spikes voltage recycling, and it is used for the power supply of synchronous rectifying controller, avoid energy loss.
The technology employed by the present utility model is
A kind of synchronous rectification power supply circuit with absorption function, including first diode, first capacitor, the second capacitor,Third capacitor and metal-oxide-semiconductor；
The energization pins of synchronous rectifying controller are connected by the different name end of the second capacitor and the vice-side winding of main transformer,The grid of the output pin of synchronous rectifying controller and metal-oxide-semiconductor connects, the grounding pin of synchronous rectifying controller respectively with metal-oxide-semiconductorSource electrode, the second capacitor the other end and main transformer vice-side winding different name end connection；One end of first capacitor is passed throughIt is connect after first diode with the different name end of the vice-side winding of main transformer；The combination of the cathode of first capacitor and first diodePoint is connect with the energization pins of the synchronous rectifying controller；The other end of first capacitor respectively with the drain electrode of metal-oxide-semiconductor andOne end of three capacitors connects；The other end of third capacitor is grounded.
Further, the synchronous rectification power supply circuit further includes zener diode；The anode of the zener diode withThe different name end of the vice-side winding of main transformer connects, and the cathode of zener diode and the energization pins of synchronous rectifying controller connectIt connects.
Further, the synchronous rectification power supply circuit further includes first be connected between first capacitor and third capacitorResistance.
Further, the synchronous rectification power supply circuit further includes the energization pins connection of one end and synchronous rectifying controllerSecond resistance；The other end of second resistance is connect with the binding site of the cathode of first capacitor and first diode.
Further, the synchronous rectification power supply circuit further includes the second diode；The anode of second diode withFirst capacitor is connected with the binding site of the cathode of first diode, and the cathode of the second diode and one end of second resistance connect；The other end of second resistance and the energization pins of synchronous rectifying controller connect.
Further, the synchronous rectification power supply circuit further includes 3rd resistor；One end of the 3rd resistor and thirdCapacitor is connected with the binding site of first resistor, the other end ground connection of 3rd resistor.
Further, the model TEA1995T of the synchronous rectifying controller.
The utility model has the following beneficial effects:
The utility model is by setting first diode, first capacitor and the second capacitor, so that the utility model is sameWalk the high frequency point that commutation supply voltage circuit generates the output capacitance resonance of the leakage inductance of main transformer and the MOSFET of pwm signal controlThe recycling of peak voltage, and it is used for the power supply of synchronous rectifying controller, avoid energy loss；Secondly, synchronizing for the utility model is wholeStream power supply circuit does not need to be powered synchronous rectifying controller using increase auxiliary winding, greatly reduces main transformerLeakage inductance oscillation, while reducing the fixed loss of Switching Power Supply, and reduce stand-by power consumption, improve efficiency.
Detailed description of the invention
Fig. 1 is a kind of circuit diagram of the synchronous rectification power supply circuit of existing inverse-excitation type switch power-supply；
Fig. 2 is a kind of circuit diagram of synchronous rectification power supply circuit with absorption function of the utility model；
Fig. 3 be main transformer in a kind of synchronous rectification power supply circuit of inverse-excitation type switch power-supply shown in FIG. 1 secondary side aroundThe waveform diagram of the A point of group；
Fig. 4 is the vice-side winding of main transformer in a kind of synchronous rectification power supply circuit with absorption function shown in Fig. 2A point waveform diagram.
Specific embodiment
With reference to the accompanying drawing and specific embodiment does further explaination to the utility model.
Embodiment 1:
As shown in Fig. 2, the present embodiment provides a kind of synchronous rectification power supply circuit with absorption function, including the one or two polePipe D1, first capacitor C1, the second capacitor C2, third capacitor C3 and metal-oxide-semiconductor Q2；
The energization pins of synchronous rectifying controller pass through the different name end of the vice-side winding of the second capacitor C2 and main transformer T1Connection, the output pin of synchronous rectifying controller are connect with the grid of metal-oxide-semiconductor Q2, the grounding pin difference of synchronous rectifying controllerIt is connect with the different name end of the vice-side winding of the source electrode of metal-oxide-semiconductor Q2, the other end of the second capacitor C2 and main transformer T1；First electricityThe one end for holding C1 is connect after first diode D1 with the different name end of the vice-side winding of main transformer T1；First capacitor C1 andThe binding site of the cathode of one diode D1 is connect with the energization pins of the synchronous rectifying controller；The other end of first capacitor C1It is connect respectively with one end of the drain electrode of metal-oxide-semiconductor Q2 and third capacitor C3；The other end of third capacitor C3 is grounded.
Working principle:
(t is connected in metal-oxide-semiconductor Q1on) when, electric current flows through main transformer T1 and starts energy storage, while the vice-side winding of main transformer T1Different name end A point be negative voltage, the voltage first capacitor C1 that third capacitor C3 is powered on charges to the second capacitor C2, charging current Ic=C* (dV/dt)；When steady operation, input voltage and output voltage are constant, can change by adjusting the size of first capacitor C1Become charging current with power consumption needed for meeting different synchronous rectifying controllers, in the present embodiment, the synchronous rectifying controllerModel TEA1995T.
Metal-oxide-semiconductor Q1 ends (toff) when, the primary side winding of main transformer T1 generates reflected voltage and is coupled to main transformer T1'sVice-side winding, Fig. 3 are the A point of the vice-side winding of main transformer T1 in existing synchronous rectification power supply circuit in a switch periods(Tfs) waveform.Fig. 4 is the A point of the vice-side winding of main transformer T1 in the synchronous rectification power supply circuit of the utility model oneThe waveform of a switch periods (Tfs).In Fig. 3 and Fig. 4, Vzd is the leakage inductance of main transformer T1 and the output capacitance of metal-oxide-semiconductor Q1High frequency spikes voltage caused by resonance, Vo are output voltage, when V- is that metal-oxide-semiconductor Q1 is connected, negative voltage that A point senses.MOSBefore pipe Q1 cut-off, the voltage Vb=Va+V of B point in Fig. 2C2, Va is the voltage of A point, and Vc2 is the voltage at the second both ends capacitor C2, becauseThis high frequency spikes voltage needs to first pass through first diode D1 and charges to first capacitor C1, and energy is stored in the first electricityHold in C1；It feeds back to when metal-oxide-semiconductor Q1 is connected again in the second capacitor C2, is used for synchronous rectifying controller.
Embodiment 2:
As shown in Fig. 2, the present embodiment provides a kind of synchronous rectification power supply circuit with absorption function, including the one or two polePipe D1, first capacitor C1, the second capacitor C2, third capacitor C3 and metal-oxide-semiconductor Q2；
The energization pins of synchronous rectifying controller pass through the different name end of the vice-side winding of the second capacitor C2 and main transformer T1Connection, the output pin of synchronous rectifying controller are connect with the grid of metal-oxide-semiconductor Q2, the grounding pin difference of synchronous rectifying controllerIt is connect with the different name end of the vice-side winding of the source electrode of metal-oxide-semiconductor Q2, the other end of the second capacitor C2 and main transformer T1；First electricityThe one end for holding C1 is connect after first diode D1 with the different name end of the vice-side winding of main transformer T1；First capacitor C1 andThe binding site of the cathode of one diode D1 is connect with the energization pins of the synchronous rectifying controller；The other end of first capacitor C1It is connect respectively with one end of the drain electrode of metal-oxide-semiconductor Q2 and third capacitor C3；The other end of third capacitor C3 is grounded.
Preferably, as shown in Fig. 2, in the present embodiment, the synchronous rectification power supply circuit further includes zener diode ZD1；The anode of the zener diode ZD1 is connect with the different name end of the vice-side winding of main transformer T1, the cathode of zener diode ZD1It is connect with the energization pins of synchronous rectifying controller.Zener diode ZD1 is for flowing through when preventing Switching Power Supply transient changingThe electric current of metal-oxide-semiconductor Q1 is too big, and oscillation aggravation causes the overtension of the second capacitor C2 to cause to damage synchronous rectifying controller.
Preferably, as shown in Fig. 2, in the present embodiment, the synchronous rectification power supply circuit further includes being connected to first capacitorFirst resistor R2 between C1 and third capacitor C3.
Further, as shown in Fig. 2, in the present embodiment, the synchronous rectification power supply circuit further include one end with it is synchronous wholeThe second resistance R1 of the energization pins connection of stream controller；The other end and first capacitor C1 and first diode of second resistance R1The binding site of the cathode of D1 connects.First resistor R2 and second resistance R1 play the role of damping buffering.
Preferably, as shown in Fig. 2, in the present embodiment, the synchronous rectification power supply circuit further includes the second diode D2；InstituteThe anode for stating the second diode D2 is connect with the binding site of the cathode of first capacitor C1 and first diode D1, the second diode D2Cathode connect with one end of second resistance R1；The other end of second resistance R1 and the energization pins of synchronous rectifying controller connectIt connects.
Further, as shown in Fig. 2, in the present embodiment, the synchronous rectification power supply circuit further includes 3rd resistor Ro；InstituteThe one end for stating 3rd resistor Ro is connect with the binding site of third capacitor C3 and first resistor R2, another termination of 3rd resistor RoGround.
The utility model is not limited to above-mentioned optional embodiment, anyone can obtain under the enlightenment of the utility modelOther various forms of products out.Above-mentioned specific embodiment should not be understood the limitation of the pairs of protection scope of the utility model,The protection scope of the utility model should be subject to be defined in claims, and specification can be used for explaining that right is wantedSeek book.