Three terminal type power switch power supply circuit
Technical field
The present invention relates to semiconductor integrated circuit, more particularly, relate to a kind of three terminal type power switch power supply circuit.
Background technology
When selecting the components and parts of suitable power power-supply and corresponding framework, overriding concern be the cost of making.Typical inverse-excitation type switch power-supply is not integrated in the chip owing to switching power tube, at least need following pin: an earth potential pin VS (also will distinguish Power Groud and simulation ground sometimes), the pin FB of a low pressure transmission feedback signal, a switching power tube grid-control making pin GATE, the high pressure pin VDD (using adjuster (REGULATOR) that high pressure is become inner low-tension supply usually) of a required internal electric source when producing the chip operate as normal gathers enough 8 pin and also can increase the compensation pin that some connect peripheral cell to adapt to the encapsulation of 8 pin so be generally.Fig. 1 and Fig. 2 show the circuit diagram of the inverse-excitation type switch power-supply that adopts electric resistance partial pressure feedback and optical coupling feedback respectively.
Because pin of chip is few more, cost is also just low more naturally.And the power switch power supply can be integrated in the chip by the switching mode circuit with large amount of complex and has more competitiveness.
Therefore, need a kind of desirable three terminal type power switch power supply circuit.
Summary of the invention
The technical problem to be solved in the present invention is, the defective too much at the chip pin of prior art, that cost is too high provides a kind of desirable three terminal type power switch power supply circuit.
The technical solution adopted for the present invention to solve the technical problems is: construct a kind of three terminal type power switch power supply circuit, comprise transformer, be connected to the rectification circuit of the former limit of described transformer the first terminal, be connected to the output circuit of described transformer secondary and the feedback circuit of the feedback end of former limit the 3rd terminal that is connected to described transformer and output circuit, described three terminal type power switch power supply circuit also comprises the trifocal chip, the feedback signal control end of described trifocal chip is connected to the output of described feedback circuit, the chip high voltage end of described trifocal chip is connected to rectification circuit and the former limit of described transformer second terminal, and the earth terminal of described trifocal chip links to each other with former limit the 4th terminal of described transformer.
In three terminal type power switch power supply circuit of the present invention, described trifocal chip comprises: hysteresis comparator, the internal high pressure charging module, the JFET pipe, MOSFET power tube and power tube control unit, the input of wherein said hysteresis comparator connects feedback signal control end and reference voltage respectively, output connects the control end of internal high pressure charging module, the output of described internal high pressure charging module links to each other with the source electrode of JFET pipe, the drain electrode of described JFET pipe connects the chip high voltage end, grid connects the earth terminal of described trifocal chip, the input of described power tube control unit connects the feedback signal control end, output links to each other with the grid of described MOSFET power tube, and the drain electrode of described MOSFET power tube connects the chip high voltage end, source electrode connects the earth terminal of described trifocal chip.
In three terminal type power switch power supply circuit of the present invention, described power tube control unit comprises oscillator, rest-set flip-flop, PWM comparator and shunt regulon, described shunt regulon is sampled described feedback signal to obtain the error level by the feedback signal control end, described error level is used to cut the sawtooth waveforms that oscillator produces, and described sawtooth waveforms converts the grid control signal that is used to control described MOSFET power tube to through PWM comparator and rest-set flip-flop.
In three terminal type power switch power supply circuit of the present invention, described rectification circuit comprises rectifier bridge, the 3rd electric capacity, the 6th diode, the 3rd diode, wherein said rectifier bridge is connected between the earth terminal of the former limit the first terminal of transformer and described trifocal chip, the anode of the 3rd diode is connected to the negative electrode that the former limit of transformer the first terminal, negative electrode are connected to the 6th diode, the anode of described the 6th diode is connected to the chip high voltage end, and described the 3rd electric capacity is in parallel with described the 3rd diode.
In three terminal type power switch power supply circuit of the present invention, described the 6th diode is a Ultrafast recovery diode.
In three terminal type power switch power supply circuit of the present invention, described output circuit comprises second diode, voltage-stabiliser tube, the anode of wherein said second diode links to each other with secondary five terminal of described transformer, the negative electrode of described second diode and the negative electrode of described voltage-stabiliser tube, the anode of described voltage-stabiliser tube is connected to described feedback circuit.
In three terminal type power switch power supply circuit of the present invention, described feedback circuit comprises the 5th diode, optocoupler, the 4th resistance, the 3rd resistance, the 7th electric capacity, the anode of wherein said the 5th diode links to each other with the former limit of described transformer the 3rd terminal, negative electrode is connected to the reception collector electrode of described optocoupler, the receiving terminal emitter of described optocoupler is connected to the feedback signal control end of described trifocal chip, the transmitting terminal negative electrode of described optocoupler links to each other with ground, the transmitting terminal anode of described optocoupler is connected to the anode of described voltage-stabiliser tube through the 4th resistance, and the series circuit of described the 3rd resistance and the 7th electric capacity is connected between the earth terminal of the receiving terminal emitter of described optocoupler and described trifocal chip.
Implement three terminal type power switch power supply circuit of the present invention, have following beneficial effect: the feedback signal terminal that will embody feedback quantity is multiplexed with the chip internal power supply, the chip high voltage end is multiplexed with the high pressure pin of internal electric source when producing the chip operate as normal when powering on by the internal high pressure charging module that joins with the chip high voltage end, and close the high-voltage charging module after powering on finishing, keep internal electric source by the system feedback amount and be in normal level, add earth terminal, the present invention only needs simple Y type tripod encapsulation just can meet the demands, reduced cost, and need not join power tube outward, be user-friendly to.
Description of drawings
The invention will be further described below in conjunction with drawings and Examples, in the accompanying drawing:
Fig. 1 is the circuit theory diagrams of first embodiment of the inverse-excitation type switch power-supply of prior art;
Fig. 2 is the circuit theory diagrams of second embodiment of the inverse-excitation type switch power-supply of prior art;
Fig. 3 is the theory diagram of first embodiment of three terminal type power switch power supply circuit of the present invention;
Fig. 4 is the theory diagram of trifocal chip of the present invention;
Fig. 5 is the circuit theory diagrams of second embodiment of three terminal type power switch power supply circuit of the present invention.
Embodiment
As shown in Figure 3, three terminal type power switch power supply circuit of the present invention, comprise transformer T1, be connected to the rectification circuit 100 of the former limit of described transformer T1 1 end, be connected to the output circuit 400 of described transformer T1 secondary and the feedback circuit 200 of the feedback end JK of former limit 3 ends that are connected to described transformer T1 and output circuit 400, wherein, described three terminal type power switch power supply circuit also comprises trifocal chip 300, the feedback signal control end VC of described trifocal chip 300 is connected to the output of described feedback circuit 200, the chip high voltage end VD of described trifocal chip 300 is connected to rectification circuit 100 and the former limit of described transformer 2 ends, and the earth terminal VS of described trifocal chip 300 links to each other with former limit 4 ends of described transformer T1.
In each embodiment of the present invention, any functional circuit and module that described rectification circuit, output circuit and feedback circuit all can adopt those skilled in the art to know are implemented its function.In another preferred embodiment of the present invention, described feedback circuit can also be a resistance reaction type circuit.
Fig. 4 is the theory diagram of trifocal chip of the present invention.As shown in Figure 4, described trifocal chip 300 comprises: hysteresis comparator 301, internal high pressure charging module HVIS, the JFET pipe, MOSFET power tube and power tube control unit 302, the input of wherein said hysteresis comparator 301 connects feedback signal control end VC and reference voltage VREF respectively, output connects the control end of internal high pressure charging module HVIS, the output of described internal high pressure charging module HVIS links to each other with the source electrode of JFET pipe, the drain electrode of described JFET pipe meets chip high voltage end VD, grid connects the earth terminal VS of described trifocal chip 300, the input of described power tube control unit 302 connects feedback signal control end VC, output links to each other with the grid of described MOSFET power tube, and the drain electrode of described MOSFET power tube meets chip high voltage end VD, source electrode connects the earth terminal VS of described trifocal chip (300).
In the present embodiment, described power tube control unit 302 comprises oscillator OSC, rest-set flip-flop, PWM comparator and shunt regulon 303, described shunt regulon 303 is sampled described feedback signal to obtain error level VERRO by feedback signal control end VC, described error level VERRO is used to cut the sawtooth waveforms that oscillator OSC produces, and described sawtooth waveforms converts the grid control signal that is used to control described MOSFET power tube to through PWM comparator and rest-set flip-flop.
Fig. 5 is the circuit theory diagrams of second embodiment of three terminal type power switch power supply circuit of the present invention. trifocal chip wherein can be with reference to shown in Figure 4. as shown in Figure 5; AC1; AC2 indirect communication civil power; after the rectifier bridge rectification; filter big ripple by capacitor C 1 and obtain direct current signal L1. under initial condition; trifocal chip 300 is not worked; the MOSFET power tube turn-offs; the voltage of chip high voltage end VD can rise to the D. C. value that equates with L1 place voltage; this time; JFET pipe and high-voltage charging module HVIS can constitute one and be similar to constant current I1 and (be subjected to the voltage influence on the chip high voltage end VD little; voltage on the chip high voltage end VD is big more; the JFET pipe is severe more with regard to pinch off) circuit of charging structure; the voltage of feedback signal control end VC is that slope rises with I1/C7; rising along with the voltage of feedback signal control end VC; benchmark is also progressively set up. after the voltage of feedback signal control end VC is higher than the VREF reference voltage of hysteresis comparator 301; turn-off high-voltage charging module HVIS; trifocal chip 300 beginning operate as normal; shunt regulator module 303 can obtain an error level VERRO according to the voltage of sampled feedback signal control end VC; be in the sawtooth waveforms of the oscillator OSC module generation of operate as normal this moment in order to cutting; and through producing the square wave (the low more then duty ratio of voltage at this feedback signal control end VC place can be big more) of the certain duty ratio relevant behind PWM comparator and the rest-set flip-flop with the feedback signal of feedback signal control end VC; the switch motion of this rectangular wave drive MOSFET power tube; when the MOSFET power tube turn-offs; can see; the former limit winding current of transformer T1 is wanted to reduce; so between chip high voltage end VD and L1, produce an induced electromotive force; this moment, the voltage of chip high voltage end VD can be up to 700V; 3 transient voltage inhibitory action of diode D3 and capacitor C among the figure. for reducing loss; diode D6 can be Ultrafast recovery diode. diode D3; capacitor C 3 and diode D6; the peak voltage that produces by high-frequency electrical depressor leakage inductance when the former limit winding of transformer T1 forms a loop with 300 shutoffs of absorption trifocal chip; play the drain electrode protective effect. along with the voltage on the chip high voltage end VD raises; the voltage that 5 ends of transformer T1 secondary winding are also pressed 5 ends of turn ratio rising transformer T1 secondary winding raises; and by diode D2; after the rectification of capacitor C 2 big capacitor C 2 is carried out energy supplement; secondary 3 ends are also guaranteed optocoupler U1 operate as normal for height simultaneously; if D4 is a voltage-stabiliser tube. the junction voltage of pressure drop on the negligible resistance R4 and diode D2; exporting near the .R4 of the puncture voltage that will be stabilized in voltage-stabiliser tube D4 so is the current-limiting resistance of the transmitting terminal place light-emitting diode of optocoupler U1; also determining simultaneously the gain of radio circuit. optocoupler U1 scalable is to the charging current size of feedback signal control end VC. diode D5; capacitor C 5 strobes; resistance R 3 compensates loop to some extent for the ESR. of capacitor C 7 can introduce a zero point herein; the charging current of feedback will cause the slight change of the voltage of feedback signal control end VC; separating these feedback quantities of reflection in the square wave of new duty ratio by the shunt regulator module in the chip 303. the energy value that replenishes and duty ratio and major-minor limit umber of turn are than relevant. and the voltage as if feedback signal control end VC is lower; it is big that duty ratio then becomes; MOSFET power tube ON time is elongated; because voltage=0 on the chip high voltage end VD; the former limit of transformer T1 winding both end voltage is constant always to be VL1; its electric current can rise energy storage 1/2Li by (VL1/ master limit inductance) this slope
2Can become big, be discharged into the energy that capacitor C 2 replenishes and also just become many when the MOSFET power tube closes to have no progeny like this, VOUT can slightly rise, the light-emitting diode of the transmitting terminal of optocoupler U1 can be brighter, the electric current of the charging of receiving terminal induction also can become bigger, thereby the voltage at feedback signal control end VC place is pulled back, form the feedback stability loop.
Implement three terminal type power switch power supply circuit of the present invention, with the feedback signal terminal vc multiplexing that embodies feedback quantity is the chip internal power supply, chip high voltage end VD is multiplexed with the high pressure pin of internal electric source when producing the chip operate as normal when powering on by the internal high pressure charging module HVIS that joins with chip high voltage end VD, and close high-voltage charging module HVIS after powering on finishing, keep internal electric source by the system feedback amount and be in normal level, add earth terminal VS, only need simple Y type tripod encapsulation just can meet the demands, reduced cost, and need not join power tube outward, be user-friendly to.
Though the present invention describes by specific embodiment, it will be appreciated by those skilled in the art that, without departing from the present invention, can also carry out various conversion and be equal to alternative the present invention.Therefore, the present invention is not limited to disclosed specific embodiment, and should comprise the whole execution modes that fall in the claim scope of the present invention.