CN2914480Y - Switch type power transducer - Google Patents

Abstract

The utility model relates to a switch-type power converter. The power converter comprises a transformer including a first primary winding and a second primary winding respectively coupled with a positive power rail and a negative power rail; a switch connected between the first and second primary windings for switching the transformer; a control circuit coupled with the switch and the second primary windings for producing a switch signal to switch the switch and adjust the output of the switch-type power converter; a supply capacitor coupled with the control circuit to supply power to the control circuit; and a diode coupled with the negative power rail and the supply capacitor. The second primary winding has a leakage inductor for storing energy when the switch is switched on and for supplying the energy to the supply capacitor through the diode when the switch is switched off. The configuration of the transformer and the switch can improve efficiency and reduce electromagnetic interference of the switch-type power converter.

Description

Switching power converter

Technical field:

The utility model relates to a kind of power converter, is meant a kind of switching power converter especially.

Background technology:

Press, power converter has extensively been applied to provide and has been adjusted voltage and electric current now, and the research focus of power converter is to be placed on how to allow the power converter can more efficient saving power supply at present.Switching power converter includes a control unit, a switch and a transformer usually, wherein control unit applies to the output voltage and/or the output current of sensing switching power converter, and produces the switching and output voltage and/or the output current of adjusting switching power converter of a controlling signal with control switch.

See also Fig. 1, it is the circuit diagram of known switching power converter.As shown in the figure, known switching power converter includes a transformer 10, and it includes a first side winding N _P, a secondary side winding N _SWith an auxiliary winding N _A, first side winding N _PAn end couple a positive supply rail V _INOne switch 11, it connects first side winding N _PThe other end, and be connected to a negative supply rail via a resistance 12, negative supply rail is an earth terminal; One control unit 25, it couples switch 11, is used for control switch 11 with switching transformer 10 and output voltage and/or the output current of adjusting switching power converter; Secondary side winding N _S, the one end connects a rectifier 13; One filter capacitor 14, its two ends are coupled in rectifier 13 and secondary side winding N respectively _SThe other end.When switch 11 conductings, energy will be stored to transformer 10, in case switch 11 by the time, transformer 10 stored energy will be via secondary side winding N _SBe released into the output of switching power converter, simultaneously the auxiliary winding N of transformer 10 _AProduce a reflected voltage V _AUX

$V_o+V_F=N_{\mathrm{NS}}\×\frac{\mathrm{d\φ}}{\mathrm{dt}}---\left(1\right)$

$V_{\mathrm{AUX}}=N_{\mathrm{NA}}\×\frac{\mathrm{d\φ}}{\mathrm{dt}}---\left(2\right)$

According to equation (1) and (2), reflected voltage V _AUXCan be expressed as:

$V_{\mathrm{AUX}}=\frac{N_{\mathrm{NA}}}{N_{\mathrm{NS}}}\×(V_o+V_F)---\left(3\right)$

Wherein, N _NAWith N _NSBe respectively auxiliary winding N _AWith secondary side winding N _SUmber of turn; V _OOutput voltage for switching power converter; V _FPressure drop for the forward bias voltage drop of rectifier 13; Φ is a magnetic flux, Φ=B * A _e(B is a magnetic density, and Ae is the axle center sectional area of transformer 10).

Control unit 25, it is provided with a feed end VDD and an earth terminal GND, to be used to receive power supply; One detecting voltage end VS, it is coupled between two resistance 15,16 of a bleeder circuit, and bleeder circuit is connected the auxiliary winding N of transformer 10 _AAnd between the negative supply rail, detecting voltage end VS produces a detecting voltage V _DET1, it can be expressed as:

$V_{\mathrm{DET}1}=\frac{R_{16}}{R_{15}+R_{16}}\×V_{\mathrm{AUX}}---\left(4\right)$

Wherein, R ₁₅With R ₁₆Be respectively the resistance value of resistance 15 and resistance 16.Reflected voltage V _AUXMore via 17 chargings of 18 pairs one of diodes supply electric capacity, with power supply to control unit 25.

Aforesaid resistance 12, it is used for as a current sensing device, and resistance 12 is connected between switch 11 and the negative supply rail, switches electric current I with one of conversion transformer 10 _PBe a current signal V _CSOne current sense end VI of control unit 25 connects resistance 12, to be used for detecting current signal V _CS, an output VG of control unit 25 produces one and switches signal V _PWMWith switching transformer 10.Though the switching power converter of commonly using can be adjusted output voltage and output current, it has several shortcomings.First shortcoming is that the leakage inductance of transformer 10 causes high power consumption; in addition owing to leakage inductance can storage power form the high voltage surging; destroy switch 11 so easily; so the switching power converter of commonly using is to be provided with a buffer circuit for protection switch 11; it includes buffering diode 19, a buffer capacitor 20 and a buffer resistance 21; be used to consume the stored energy of leakage inductance of transformer 10, avoid forming the high voltage surging with protection switch 11.

Second shortcoming is that switching power converter lacks adjustment under underload and non-loaded state.The switching power converter of commonly using is the auxiliary winding N by transformer 10 _APower supply is to control unit 25, so the operating current of control unit 25 is promptly represented auxiliary winding N _ALoad.If the output loading of switching power converter is lower than auxiliary winding N _ALoad the time, the stored energy of transformer 10 will only can be via diode 18 and auxiliary winding N _ABe released into supply electric capacity 17, so when switch 11 ends, rectifier 13 will still remain closed condition, so the output voltage V of switching power converter _OCan't be from auxiliary winding N _AFeedback to control unit 25, so under underload and non-loaded state, the detecting voltage V that detecting voltage end VS is produced _DET1Only relevant with the voltage of feed end VDD, so the switching power converter of commonly using lacks the property adjusted.

Another known techniques is by United States Patent (USP)s that the people proposed the 6th such as Mr.s Yang, 853, No. 563 " flyback power converter (Primary-side controlled flyback power converter) of primary side control ", one major defect of this known techniques is electromagnetic interference (Electric and MagneticInterference, EMI), the reason of its generation is that the drain of switch is connected directly to positive supply rail, so a parasitic capacitance of switch couples mutually with a stray inductance, thereby form a high-frequency resonance groove, so will produce higher electromagnetic interference.

Therefore, the utility model proposes a kind of switching power converter, it has the characteristic of high-effect and low electromagnetic interference.In addition, switching power converter of the present utility model can accurately be adjusted output voltage under underload and non-loaded state.

Novel content:

Main purpose of the present utility model, be to provide a kind of switching power converter, it comprises a transformer, transformer is provided with first first side winding and second first side winding, be provided with switch between first first side winding and second first side winding, so can promote the usefulness and reduction electromagnetic interference of switching power converter.

Another purpose of the present utility model, be to provide a kind of switching power converter, the leakage inductance of its transformer can allow the voltage of supply electric capacity be higher than the voltage that secondary side winding reflected of transformer, make the output voltage of switching power converter to feedback to control circuit, so can promote the load of switching power converter under underload and the non-loaded state property adjusted via second first side winding of transformer.

Another purpose of the present utility model, be to provide a kind of switching power converter, its transformer is provided with auxiliary winding and can charges to supply electric capacity, so provides second source to control circuit, but and then guarantees control circuit normal operation under vicious situation.

The utility model switching power converter, it includes a transformer, and transformer is provided with one first first side winding and one second first side winding, and two windings couple a positive supply rail and a negative supply rail respectively; One switch, it is connected between first first side winding and second first side winding, is used for switching transformer; One current sensing device, it couples the switch and second first side winding, is used for switching electric current according to one of transformer and produces a current signal; One control circuit, it couples second first side winding of switch and transformer, produces one with the foundation current signal and switches signal, switches signal and is used for diverter switch and the output of adjusting switching power converter; One supply electric capacity, its connect control circuit with power supply to control circuit; One diode, it couples negative supply rail and supplies electric capacity so that supply electric capacity is charged.Wherein, the second above-mentioned first side winding has a leakage inductance, and it stores a storage power when switch conduction, and when switch ends, discharges storage power to supplying electric capacity via diode.So, can promote the usefulness and reduction electromagnetic interference of switching power converter, and can promote the load of switching power converter under underload and non-loaded state and adjust property by the above-mentioned transformer and the set-up mode of switch.

Description of drawings:

Fig. 1 is the circuit diagram of known switching power converter;

Fig. 2 is the circuit diagram of the switching power converter of a preferred embodiment of the present utility model;

Fig. 3 is the equivalent circuit diagram of the switching power converter of Fig. 2;

Fig. 4 is the circuit diagram of the control circuit of a preferred embodiment of the present utility model;

Fig. 5 is the circuit diagram of the switching power converter of another preferred embodiment of the present utility model.

The figure number explanation:

10 transformers, 11 switches

12 resistance, 13 rectifiers

14 filter capacitors, 15 resistance

16 resistance, 17 supply electric capacity

18 polar bodys, 19 buffering diodes

20 buffer capacitors, 21 buffer resistances

25 control units, 30 transformers

35 switches, 37 current sensing resistors

39 transformers, 40 buffering diodes

41 buffer capacitors, 42 buffer resistances

45 buffer circuits, 50 bleeder circuits

52 resistance, 55 resistance

60 first diodes, 65 second diodes

70 supply electric capacity, 80 rectifiers

90 filter capacitors, 100 control circuits

110 sampling stick holding circuits, 120 error amplifiers

125 comparators, 150 oscillators

160 flip-flop GND earth terminals

I _PSwitch current L _I1Leakage inductance

L _I2Leakage inductance N _AAuxiliary winding

N _A2Auxiliary winding N _PFirst side winding

N _P1The first first side winding N _P2Second first side winding

N _SInferior side winding V _AUXReflected voltage

V _CSCurrent signal V _DET1Detecting voltage

V _DET2Detecting voltage V _FBAward voltage

V _INPositive supply rail V _NP2Voltage

V _OOutput voltage V _PWMSwitch signal

V _RReference voltage V _RSTThe replacement signal

V _SSample signal VDD feed end

VG output VI current sense end VS detecting voltage end

Embodiment:

For making the auditor further understanding and understanding more be arranged to architectural feature of the present utility model and the effect reached, sincerely help with preferred embodiment figure and cooperate detailed explanation, illustrate as the back:

Seeing also Fig. 2, is the circuit diagram of the switching power converter of a preferred embodiment of the present utility model.As shown in the figure, switching power converter of the present utility model includes a transformer 30, is used for storage power and shifts the secondary side of storage power to transformer 30 from a primary side of transformer 30.Wherein, the primary side of transformer 30 is provided with one first first side winding N _P1With one second first side winding N _P2The secondary side of transformer 30 then is provided with a secondary side winding N _SThe first first side winding N _P1With the second first side winding N _P2Couple the power rail of switching power converter, i.e. first side winding N _P1Couple the positive supply rail V of transformer 30 _IN, and the second first side winding N _P2Then couple the negative supply rail of transformer 30, that is be coupled to earth terminal.One switch 35, it is connected in the first first side winding N _P1With the second first side winding N _P2Between, be used for switching transformer 30, wherein switch 35 can be a power electric crystal or be a power metal oxide-semiconductor field effect electric crystal (Metal Oxide Semiconductor Field EffectTransistor, MOSFET).Because switch 35 is connected in the first first side winding N _P1With the second first side winding N _P2Between, therefore can eliminate the caused high-frequency resonance groove of dominant parasitic device, and then reduce electromagnetic interference.

One current sensing device, a for example graphic current sensing resistor 37, its two ends connect the switch 35 and the second first side winding N respectively _P2, with the switch current I of foundation transformer 30 _PProduce a current signal V _CSIn order to adjust an output voltage V of switching power converter _O, a control circuit 100 couples the second first side winding N of switch 35 and transformer 30 _P2, switch signal V to produce one _PWM, it is used for diverter switch 35 and the output voltage V of adjusting switching power converter _OOne supply electric capacity 70, it connects control circuit 100, to control circuit 100, is provided with one first diode 60 between the negative supply rail of supply electric capacity 70 and transformer 30 with power supply.

One buffer circuit 45, it is coupled to the first first side winding N _P1With positive supply rail V _INBetween, buffer circuit 45 includes buffering diode 40, a buffer capacitor 41 and a buffer resistance 42.One end of buffering diode 40 couples the first first side winding N _P1With switch 35, buffer capacitor 41 is coupled to the other end and the positive supply rail V of buffering diode 40 _INBetween, buffer resistance 42 is then in parallel with buffer capacitor 41.One bleeder circuit 50, it is coupled to the second first side winding N _P2And between the negative supply rail, bleeder circuit 50 includes resistance 52,55, and resistance 52 is coupled between control circuit 100 and the negative supply rail, and resistance 55 then is coupled to the resistance 52 and the second first side winding N _P2Between.One rectifier 80, the one end couples secondary side winding N _SAn end, and the two ends of a filter capacitor 90 are to be respectively coupled to secondary side winding N _SThe other end and the other end of rectifier 80.

Seeing also Fig. 3, is the equivalent circuit diagram of the switching power converter of Fig. 2.As shown in the figure, the first first side winding N _P1With the second first side winding N _P2Leakage inductance L is arranged respectively _I1, L _I2Because the geometrical structure factor of transformer, cause the storage power of the first side winding of transformer can not be transferred to other windings of transformer, leakage inductance L fully _I1, L _I2Represent that promptly storage power can't be transferred fully.When switch 35 conductings, switch current I _PIn inflow transformer 30, energy promptly is stored to transformer 30 and leakage inductance L _I1, L _I2In, and when switch 35 ended, transformer 30 stored storage power can be released into secondary side winding N _S, while leakage inductance L _I1, L _I2Stored storage power can be in the loop circulating transfer, if when the loop is blocked, then can produce an abrupt voltage wave, it can be expressed as:

$V=L\×\frac{\mathrm{di}}{\mathrm{dt}}---\left(5\right)$

For these reasons, buffer circuit 45 promptly applies to consume leakage inductance L _I1Storage power, to avoid producing a high voltage surging and protection switch 35.The power P that the buffer resistance 42 of buffer circuit 45 is consumed _RCan be expressed as:

$P_R=\frac{{V_{R42}}^2}{R_{42}}=\frac{1}{2}\×L_1\×{I_P}^2\×\mathrm{fsw}---\left(6\right)$

Wherein, R ₄₂Resistance value for buffer resistance 42; V _R42Both end voltage for buffer resistance 42; L ₁Be leakage inductance L _I1Inductance value; f _SWSwitching frequency for switch 35.

By above-mentioned equation (6) as can be known, the inductance value that reduces the leakage inductance of transformer 30 will promote the usefulness of switching power converter, yet in order to meet safety condition, the winding of transformer 30 always can produce a significant leakage inductance value, and the simple and easy method that therefore reduces the leakage inductance value promptly reduces the umber of turn of winding.The relation of inductance value and umber of turn is shown in following equation:

$L=\mathrm{\μ}\×\frac{0.4\mathrm{\π}\×\mathrm{Ae}}{\mathrm{li}}\×N^2---\left(7\right)$

Wherein, L is an inductance value; μ is the axle center magnetic capacity; Li is the length of magnetic path; N is a umber of turn; Ae is the axle center sectional area of transformer 30.

The first side winding of transformer 30 of the present utility model is cut into the first first side winding N _P1With the second first side winding N _P2Be to reduce umber of turn, so can reduce by the first first side winding N _P1The leakage inductance value, to improve the usefulness of switching power converter.In addition, in case switch 35 by the time, leakage inductance L _I2Storage power will through first diode 60 be released into the supply electric capacity 70, so be stored in leakage inductance L _I2Storage power will be supplied to control circuit 100 as power supply, the voltage V that produced of supply electric capacity 70 _DDCan be expressed as:

$V_{\mathrm{DD}}=[\frac{N_{\mathrm{NP}2}}{N_{\mathrm{NS}}}\×(V_O+V_F)]+V_{\mathrm{LI}2}---\left(8\right)$

Wherein, N _NP2With N _NSBe respectively the second first side winding N of transformer 30 _P2With secondary side winding N _SUmber of turn; V _LI2Be leakage inductance L _I2The voltage that is produced, it is shown in following equation and try to achieve:

$\frac{1}{2}\×C_{70}\×{V_{\mathrm{LI}2}}^2=\frac{1}{2}\×L_{12}\×{I_P}^2---\left(9\right)$

$V_{\mathrm{LI}2}=\sqrt{\frac{L_{I2}}{C_{70}}}\×I_P---\left(10\right)$

Wherein, C ₇₀Capacitance for supply electric capacity 70; L _I2Be leakage inductance L _I2Inductance value.

Because leakage inductance L _I2The voltage V that is produced _LI2Allow the supply electric capacity 70 voltage V _DDThe secondary side winding N that is higher than transformer 30 _SThe voltage that is reflected, thus switch 35 by the time, rectifier 80 will be unlocked, so the output voltage V of switching power converter _OCan be via the second first side winding N _P2Provide to control circuit 100, so the appropriate use second first side winding N _P2Leakage inductance L _I2, can improve the load of switching power converter under underload and the non-loaded state property adjusted.

Seeing also Fig. 4, is the circuit diagram of the control circuit of a preferred embodiment of the present utility model.As shown in the figure, control circuit 100 of the present utility model includes a feed end VDD and an earth terminal GND, and the supply electric capacity 70 that is connected in parallel is to receive power supply.Feed end VDD more connects first diode 60, and earth terminal GND more connects the second first side winding N _P2One detecting voltage end VS, it couples the second first side winding N via bleeder circuit 50 _P2, to be used for the second first side winding N from transformer 30 _P2Detect side one detecting voltage V _DET2, detecting voltage V _DET2Can be expressed as:

$V_{\mathrm{DET}2}=\frac{R_{52}}{R_{52}+R_{55}}\×V_{\mathrm{NP}2}---\left(11\right)$

Wherein, R ₅₂With R ₅₅Be respectively the resistance value of resistance 52,55; V _NP2Be the second first side winding N _P2Voltage.

One current sense end VI, it couples current sensing resistor 37, is used for received current signal V _CSOne output VG, the output that it couples a flip-flop 160 is used for producing switching signal V _PWMTo see through switch 35 switching transformers 30.One oscillator 150, it produces one-period property pulse wave signal, is used for starting switching signal V _PWMOne comparator 125, it is used to close switching signal V _PWM, a negative input end of comparator 25 is to connect current sense end VI, in order to received current signal V _CS, a positive input terminal of comparator 125 then connects an output of an error amplifier 120, in order to receive a back coupling signal V _FB

In case current signal V _CSBe higher than back coupling signal V _FBThe time, switch signal V _PWMTo be cut off.Comparator 125, one output connect a replacement end of flip-flop 160, in order to produce a replacement signal V _RSTAnd be sent to the replacement end of flip-flop 160, with by switching signal.Error amplifier 120, it is used for producing back coupling signal V _FB, a positive input terminal of error amplifier 120 receives a reference voltage V _R, a negative input end of error amplifier 120 then connects an output of a sampling stick holding circuit 110, to receive a sample signal V _S, be used for producing back coupling signal V _FBSampling stick holding circuit 110, one input end couples detecting voltage end VS, in order to see through bleeder circuit 50 from this detecting voltage of transformer 30 detectings V _DET2, to produce sample signal V _S

The second first side winding N _P2Voltage V _NP2With secondary side winding N _SVoltage (V _O+ V _F) between the relation, can be expressed as:

$V_O+V_F=\frac{N_{\mathrm{NS}}}{N_{\mathrm{NP}2}}\×V_{\mathrm{NP}2}---\left(12\right)$

According to equation (11) and (12), output voltage V _OCan be expressed as:

$V_O=(\frac{R_{52}+R_{55}}{R_{52}}\×\frac{N_{\mathrm{NS}}}{N_{\mathrm{NP}2}}\×V_{\mathrm{DET}2})-V_F---\left(13\right)$

Can learn the output voltage V of switching power converter by equation (13) _OBe to be adjusted.

Seeing also Fig. 5, is the circuit diagram of the switching power converter of another preferred embodiment of the present utility model.As shown in the figure, transformer 39 of the present utility model more comprises an auxiliary winding N _A2, the auxiliary winding N of transformer 39 _A2Be to connect the second first side winding N _P2, and auxiliary winding N _A2More connect supply electric capacity 70 via one second diode 65.The earth terminal GND of control circuit 100 then connects the second first side winding N _P2With auxiliary winding N _A2, and feed end VDD connects supply electric capacity 70, first diode 60 and second diode 65.Since when switch 35 ends, the second first side winding N _P2With power supply to control circuit 100, so the voltage V that produced of supply electric capacity 70 _DDIt is output voltage V with switching power converter _ORelevant, if switching power converter produces output voltage V under the situation of overcurrent and/or short circuit _O, the second first side winding N _P2Voltage V _NP2Will be too low and be unable to supply enough power supplys to control circuit 100.Therefore the utility model is to set up auxiliary winding N _A2, when switch 35 conductings, auxiliary winding N _A2Will be to 70 chargings of supply electric capacity, so auxiliary winding N _A2Can provide a second source with power supply to control circuit 100, it is to guarantee that control circuit 100 can normal operation under malfunction.

In sum, transformer set-up mode of the present utility model can reduce the inductance value of leakage inductance, the stored storage power of leakage inductance can be used for power supply to control circuit in addition, so can reach preferable usefulness and can promote the load of switching power converter under underload and the no-load condition property adjusted.In addition, because switch is arranged between the two cutting windings of transformer, so can reduce electromagnetic interference.

The above, it only is the utility model one preferred embodiment, be not to be used for limiting the scope that the utility model is implemented, so all equalizations of doing according to the described shape of the utility model claim, structure, feature and spirit change and modify, and all should be included in the claim of the present utility model.

Claims (14)

1, a kind of switching power converter is characterized in that, it includes:

One transformer, shift the secondary side of energy from a primary side of this transformer to this transformer, this transformer is provided with one first first side winding and one second first side winding, and this first first side winding and this second first side winding couple a positive supply rail and a negative supply rail respectively;

One switch is connected between this first first side winding and this second first side winding, is used to switch this transformer;

One control circuit couples this switch and this second first side winding, produces one and switches signal, is used to switch this switch and the output of adjusting this switching power converter;

One supply electric capacity connects this control circuit, and power supply is to this control circuit;

One diode couples this negative supply rail and this supply electric capacity to this supply electric capacity charging.

2, switching power converter as claimed in claim 1, it is characterized in that, more include a current sensing device, it is connected between this switch and this second first side winding, this electric current induction device switches electric current according to one of this transformer and produces a current signal, and this control circuit receives this current signal and produces this switching signal.

3, switching power converter as claimed in claim 1, it is characterized in that this second first side winding has a leakage inductance, this leakage inductance stores a storage power when this switch conduction, when this switch ended, this leakage inductance discharged this storage power and supplies electric capacity to this.

4, switching power converter as claimed in claim 1 is characterized in that, this control circuit more includes:

One feed end connects this supply electric capacity and this diode;

One earth terminal connects this supply electric capacity and receives power supply, and this earth terminal connects this second first side winding;

One detecting voltage end couples this second first side winding, detects a voltage;

One current sense end couples this switch, receives a current signal;

One output produces this switching signal according to this voltage and this current signal, switches this switch and switches this transformer.

5, switching power converter as claimed in claim 4 is characterized in that, this control circuit more includes:

One sampling stick holding circuit couples this detecting voltage end, detects this voltage, produces a sample signal;

One error amplifier couples this sampling stick holding circuit, receives this sample signal and a reference voltage, produces a back coupling signal;

One comparator couples this error amplifier and this current sense end, receives this back coupling signal and this current signal, produces a replacement signal;

One oscillator produces one-period property pulse wave signal;

One flip-flop couples this oscillator, this comparator and this output, produces this switching signal, and this periodic pulses signal and this replacement signal start respectively and end this switching signal.

6, a kind of switching power converter is characterized in that, it includes:

One transformer, shift the secondary side of energy from a primary side of this transformer to this transformer, this transformer is provided with one first first side winding, one second first side winding and an auxiliary winding, this first first side winding and this second first side winding couple a positive supply rail and a negative supply rail respectively, and this auxiliary winding couples this second first side winding;

One switch is connected between this first first side winding and this second first side winding, is used to switch this transformer;

One control circuit couples this switch and this second first side winding, produces one and switches signal, is used to switch this switch and the output of adjusting this switching power converter;

One supply electric capacity connects this control circuit, and power supply is to this control circuit;

One first diode couples this negative supply rail and this supply electric capacity to this supply electric capacity charging;

One second diode couples this auxiliary winding and this supply electric capacity to this supply electric capacity charging.

7, switching power converter as claimed in claim 6, it is characterized in that, more include a current sensing device, it is connected between this switch and this second first side winding, this electric current induction device switches electric current according to one of this transformer and produces a current signal, and this control circuit receives this current signal and produces this switching signal.

8, switching power converter as claimed in claim 6, it is characterized in that this second first side winding has a leakage inductance, this leakage inductance stores a storage power when this switch conduction, when this switch ended, this leakage inductance discharged this storage power and supplies electric capacity to this.

9, switching power converter as claimed in claim 6 is characterized in that, this control circuit more includes:

One feed end connects this supply electric capacity, this first diode and this second diode;

One earth terminal connects this supply electric capacity and receives power supply, and this earth terminal connect this second first side winding with should auxiliary winding;

One detecting voltage end couples this second first side winding, detects a voltage;

One current sense end couples this switch, receives a current signal;

One output produces this switching signal according to this voltage and this current signal, switches this switch and switches this transformer.

10, switching power converter as claimed in claim 9 is characterized in that, this control circuit more includes:

One sampling stick holding circuit couples this detecting voltage end, detects this voltage, produces a sample signal;

One error amplifier couples this sampling stick holding circuit, receives this sample signal and a reference voltage, produces a back coupling signal;

One comparator couples this error amplifier and this current sense end, receives this back coupling signal and this current signal, produces a replacement signal;

One oscillator produces one-period property pulse wave signal;

One flip-flop couples this oscillator, this comparator and this output, produces this switching signal, and this periodic pulses signal and this replacement signal start respectively and end this switching signal.

11, a kind of switching power converter is characterized in that, it includes:

One transformer is provided with one first first side winding and one second first side winding, and this first first side winding and this second first side winding couple a power rail of this switching power converter;

One switch is connected between this first first side winding and this second first side winding, is used to switch this transformer;

One control circuit couples this switch and this transformer, produces one and switches signal, is used to switch this switch and the output of adjusting this switching power converter;

One supply electric capacity connects this control circuit;

One diode couples this transformer and this supply electric capacity to this supply electric capacity charging.

12, switching power converter as claimed in claim 11, it is characterized in that more include a current sensing device, it is connected this switch, this electric current induction device switches electric current according to one of this transformer and produces a current signal, and this control circuit receives this current signal and produces this switching signal.

13, switching power converter as claimed in claim 11, it is characterized in that this transformer has at least one leakage inductance, this leakage inductance stores a storage power when this switch conduction, when this switch ended, this leakage inductance discharged this storage power and supplies electric capacity to this.

14, switching power converter as claimed in claim 11 is characterized in that, this control circuit more includes:

One feed end connects this supply electric capacity and this diode;

One earth terminal connects this supply electric capacity and this transformer;

One detecting voltage end couples this transformer, detects a voltage;

One current sense end couples this switch, receives a current signal;

One output produces this switching signal according to this voltage and this current signal, switches this switch and switches this transformer.