CN100557932C - The control circuit of power converter - Google Patents

Abstract

The invention relates to a kind of control circuit of power converter, feedback voltage of a transformer in order to the detecting power converter, control circuit includes a switch, one circuit for detecting and one switches circuit, switch couples transformer and is used for switching transformer, circuit for detecting couples transformer and is used to detect feedback voltage, produce one first signal with the foundation feedback voltage, commutation circuit produces a controlling signal according to first signal, with control switch and adjust the output of power converter, because power converter is when underload, the pulse bandwidth of feedback voltage can shorten, so circuit for detecting produces a bias voltage signal and helps the feedback voltage detecting, be inversely proportional to the discharge time of bias voltage signal and transformer, be that the bias voltage signal will strengthen when reducing discharge time, in addition, commutation circuit produces a blanking signal according to controlling signal, to guarantee the minimum pulse bandwidth of feedback voltage.

Description

The control circuit of power converter

Technical field:

The invention relates to a kind of power converter, particularly about a kind of control circuit of power converter.

Background technology:

Press, power converter extensively applies to provide the out-put supply of adjustment now.Based on considering of fail safe, the primary side of power converter and secondary side must be isolated, and are used to provide isolation and shift energy so power converter is provided with a transformer usually.See also Fig. 1, be the circuit diagram of the power converter commonly used.As shown in the figure, the power converter of commonly using is provided with a transformer 10, and it includes a first side winding N _P, a secondary side winding N _SWith an auxiliary winding N _AUX, first side winding N _PCouple an input voltage V respectively _INWith a switch 20.20 conduction periods of switch, the primary side of transformer 10 is storage power, in case switch 20 by the time, the energy that transformer 10 will discharge primary side to the secondary side of transformer 10 and and then the transfer energy to the output of power converter.Wherein, switch 20 be a power electric crystal or a power metal oxide-semiconductor field effect electric crystal (Metal Oxide Semiconductor Field Effect Transistor, MOSFET).

One current sensing resistor 21, it is series at switch 20 and earth terminal, is used for the switch current of sensing transformer 10 and produces a current signal V _S, carry out switching controls so that a controller 25 to be provided.Controller 25, it has a detecting voltage end DET, a current sense end VS and an output OUT, and detecting voltage end DET and current sense end VS couple transformer 10 and current sensing resistor 21 respectively, are used for producing a controlling signal V at output OUT _G, with control switch 20 conductings and the output that ends and adjust power converter.Controller 25 more includes a compensation end COM and an earth terminal GND, and compensation end COM couples a building-out capacitor 24, and earth terminal GND is coupled to earth terminal.The secondary side winding N of transformer 10 _SAn end be an end that couples a rectifier 15, the other end of rectifier 15 and secondary side winding N _SThe other end between be coupled with a filter capacitor 17.

When above-mentioned switch 20 ends, auxiliary winding N _AUXPromptly can produce a feedback voltage (flyback voltage) V _F, the output voltage V of itself and power converter ₀Corresponding, therefore, feedback voltage V _FCan be applied to feedback the output voltage V of power converter ₀" the Rect ifier-Converter Power Supply with Multi-ChannelFlyback Inverter " that No. the 4th, 302,803, the United States Patent (USP) that Randol ph D.W.Shelly is proposed has the technology of speeding to control of returning that discloses.Yet commonly using that the anti-control technology of speeding has can't the accurately measuring feedback voltage V _FShortcoming, particularly at power converter under light-load state.

T discharge time of the transformer 10 of power converter _DSCan be expressed as:

$T_{\mathrm{DS}}-\left(\frac{V_{\mathrm{IN}}}{V_O+V_D}\right)\×\frac{W_{\mathrm{NS}}}{W_{\mathrm{NP}}}\×T_{\mathrm{ON}}---\left(1\right)$

Wherein, V _INInput voltage for power converter; W _NPWith W _NSBe respectively the first side winding N of transformer 10 _PWith secondary side winding N _SUmber of turn; V _DPressure drop for the forward bias voltage drop of rectifier 15; T _ONBe controlling signal V _GAn ON time.

Above-mentioned feedback voltage V _F, it sees through the detecting voltage end DET that a resistance 22 is sent to controller 25, so controller 25 can produce a detecting voltage V _DET, and detect feedback voltage V for the detecting voltage end DET of controller 25 _F, but because a parasitic capacitance 23 is coupled to resistance 22, and can cause a low-frequency filter characteristics, cause feedback voltage V _FCan be filtered.Foretell in addition, power converter can shorten controlling signal V under light-load state _GON time T _ON, also learn according to equation (1) and can shorten feedback voltage V _FT discharge time _DS, so can cause detecting voltage V _DETThe situation of wave distortion takes place shown in second figure, so controller 25 can detect the feedback voltage V of low-voltage _F

Therefore, the present invention is based on the control circuit that foregoing problems proposes a kind of power converter, with can improve the detecting feedback voltage accuracy can adjust the output of power converter really.

Summary of the invention:

Main purpose of the present invention, be to provide a kind of control circuit of power converter, it produces the bias voltage signal by circuit for detecting, in order to improve the accuracy of detecting feedback voltage and to prevent wave distortion, can under light-load state, accurately detect the purpose of the feedback voltage of transformer at power converter to reach control circuit.

Another object of the present invention, be to provide a kind of control circuit of power converter, it produces the blanking signal by commutation circuit according to controlling signal, minimum ON time when guaranteeing that controlling signal is switched on, so can guarantee the minimum pulse bandwidth of feedback voltage, to reach the purpose of easy detecting feedback voltage.

The control circuit of power converter of the present invention, it is used to detect the feedback voltage of a transformer of power converter, and the output of adjusting power converter.Control circuit includes a switch and a controller, and switch couples transformer and is used for switching transformer, shifts the secondary side of energy to transformer with the primary side from transformer.Controller includes a circuit for detecting, and switches a circuit and an adjustment circuit, circuit for detecting couples transformer, be used to detect the feedback voltage of transformer, produce one first signal and one second signal with the foundation feedback voltage, first signal is relevant with the output of power converter, and second signal is the discharge time of indication transformer.Commutation circuit is used for producing a controlling signal according to first signal, with the switching of control switch and the output of adjustment power converter.

The adjustment circuit, it produces one and adjusts signal according to the pulse bandwidth of second signal, and circuit for detecting produces a bias voltage signal according to adjusting signal, and is sent to a detecting voltage end of circuit for detecting, to help detecting feedback voltage and avoiding wave distortion.In addition, commutation circuit produces a blanking signal according to controlling signal, in case when controlling signal was switched on, the blanking signal can be guaranteed the minimum ON time of controlling signal, this minimum ON time can be guaranteed the minimum pulse bandwidth of feedback voltage, so can be convenient to detect feedback voltage.

Description of drawings:

Fig. 1 is the circuit diagram of the power converter commonly used;

Fig. 2 is the oscillogram of power converter under light-load state of commonly using;

Fig. 3 is the calcspar of the controller of a preferred embodiment of the present invention;

Fig. 4 is the circuit diagram of the commutation circuit of a preferred embodiment of the present invention;

Fig. 5 is the circuit diagram of the blanking circuit of a preferred embodiment of the present invention;

Fig. 6 is the circuit diagram of the circuit for detecting of a preferred embodiment of the present invention;

Fig. 7 is the circuit diagram of the waveform detection circuit of a preferred embodiment of the present invention;

Fig. 8 is the circuit diagram of the adjustment circuit of a preferred embodiment of the present invention;

Fig. 9 is the oscillogram of power converter under light-load state of a preferred embodiment of the present invention.

The figure number explanation:

10 transformers, 15 rectifiers

17 filter capacitors, 20 switches

21 current sensing resistors, 22 resistance

23 parasitic capacitances, 24 building-out capacitors

25 controllers, 30 commutation circuits

31 oscillating circuits, 32 first triggers

33 inverter 34 and locks

35 and not b gates, 36 first comparators

40 blanking circuits, 41 current sources

42 inverters, 43 inverters

45 and not b gates, 46 electric crystals

47 electric capacity, 50 circuit for detecting

55 adjust circuit 60 bias circuits

61 second electric crystals, 62 current sources

63 first resistance, 65 first electric crystals

67 error amplifiers, 80 voltages are to signal circuit

81 charge switchs, 82 discharge switches

83 discharging current sources 84 the 3rd sampling capacitor

85 second resistance, 86 amplifiers

87 the 3rd sampling switches 89 the 4th sampling capacitor

90 the 3rd electric crystals, 91 electric crystals

92 electric crystals, 93 electric crystals

95 or lock 100 waveform detection circuit

102 inverters, 105 inverters

140 pulse wave signal generating circuits, 150 second sampling switches

151 first sampling switches, 155 second comparators

156 or lock 157 inverters

158 and lock 159 second triggers

160 second sampling capacitors, 161 first sampling capacitors

CK clock pulse input COM compensates end

DET detecting voltage end GND earth terminal

I ₉₀First electric current I _BAdjust signal

IN input N _AUXAuxiliary winding

N _PFirst side winding N _SSecondary side winding

OUT output PLS pulse wave signal

S _DSThe second signal T _DSDischarge time

T _ONON time V _ASample signal

V _BThe bias voltage signal

Embodiment:

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

The control circuit of power converter of the present invention includes switch and controller, and controller produces a controlling signal, with the switch that coupled of control and then the transformer of switchover power converter.Seeing also Fig. 3, is the calcspar of the controller of a preferred embodiment of the present invention.As shown in the figure, controller of the present invention includes a switching circuit 30, a circuit for detecting 50 and is adjusted circuit 55.Circuit for detecting 50, it detects that side DET couples transformer 10 and the feedback voltage V of detecing side transformer 10 via voltage _F, with the foundation feedback voltage V _FProduce one first signal V _FBWith one second signal S _DSAnd be sent to the compensation end COM of controller respectively and adjust circuit 55.Because feedback voltage V _FOutput voltage V with power converter ₀Corresponding, so the first signal V _FBAlso with the output voltage V of power converter ₀Corresponding, and the second signal S _DST discharge time of indication transformer 10 then _DSCommutation circuit 30, it is according to the first signal V _FBAnd generation controlling signal V _G, and be sent to output OUT, to be used for control switch 20 and the output of adjusting power converter, in addition, commutation circuit 30 more couples current sense end VS, with received current signal V _SAnd generation controlling signal V _GAdjust circuit 55, it couples circuit for detecting 50 and the foundation second signal S _DSProduce one and adjust signal I _BAnd be sent to circuit for detecting 50.

Seeing also Fig. 4, is the circuit diagram of the commutation circuit of a preferred embodiment of the present invention.As shown in the figure, commutation circuit 30 of the present invention comprises an oscillating circuit 31, and in order to produce a periodic pulse wave signal PLS, it is sent to one first trigger 32 via an inverter 33, with conducting controlling signal V _GOne input of inverter 33 is connected an output of oscillating circuit 31 and a clock pulse input of first trigger 32 respectively with an output, the one output connection one of first trigger 32 and an input of lock 34, and the output of another input connection inverter 33 of lock 34, and an output of lock 34 produces controlling signal V _GAnd transfer to output OUT.And lock 34 sees through the pulse wave signal PLS of inverter 33 according to oscillating circuit 31, allows controlling signal V _GHas maximum ON time.

One first comparator 36 is in case it applies to current signal V _SBe higher than the first signal V _FBThe time, see through an and not b gate 35 replacements first trigger 32.One positive input terminal of first comparator 36 and a negative input end be received current signal V respectively _SWith the first signal V _FB, an output of first comparator 36 then couples an input of and not b gate 35, and another input of and not b gate 35 couples an output OUT of a blanking circuit (blanking circuit) 40, in order to receive a blanking signal V _BLK, an output of and not b gate 35 couples a replacement input of first trigger 32, and in order to first trigger 32 of resetting, an input IN of blanking circuit 40 couples and the output of lock 34, in order to receive controlling signal V _G

Seeing also Fig. 5, is the circuit diagram of the blanking circuit of a preferred embodiment of the present invention.Blanking circuit 40 of the present invention is that a pulse wave produces circuit, and it includes an inverter 42, and an input of inverter 42 is the input IN that pulse wave produces circuit, and in order to receive an input signal, it is controlling signal V _GOne output of inverter 42 couples the gate of an electric crystal 46, so the input IN of pulse wave generation circuit then is coupled to the gate of electric crystal 46 via inverter 42, when pulse wave produces the input signal conducting that circuit received, to order about electric crystal 46 and close, the source electrode of electric crystal 46 is coupled to earth terminal in addition.One current source 41, it is coupled to the drain and a supply voltage V of electric crystal 46 _CCBetween.One electric capacity 47, it is coupled between current source 41 and the earth terminal.In case when electric crystal 46 was closed, current source 41 was promptly to electric capacity 47 chargings.

In addition, electric capacity 47 more sees through an inverter 43 and connects an and not b gate 45, one input coupling capacitance 47 of inverter 43, one output of inverter 43 then couples an input of and not b gate 45, another input of and not b gate 45 couples the input IN that pulse wave produces circuit, and in order to receive input signal, an output of and not b gate 45 is the output OUT that pulse wave produces circuit, in order to export a pulse wave signal, it is this blanking signal V _BLKThe capacitance of the electric current of current source 41 and electric capacity 47 is pulse bandwidths of decision pulse wave signal.As shown in the above description, blanking circuit 40 is at controlling signal V _GDuring conducting, and then produce blanking signal V _BLKIn case controlling signal V _GWhen being switched on, blanking signal V _BLKJust can guarantee controlling signal V _GHas a minimum ON time, controlling signal V _GMinimum ON time can guarantee feedback voltage V _FMinimum pulse bandwidth, can detect feedback voltage V easily _F

Seeing also Fig. 6, is the circuit diagram of the circuit for detecting of a preferred embodiment of the present invention.As shown in the figure, circuit for detecting 50 of the present invention includes an error amplifier 67, a waveform detection circuit 100 and a bias circuit 60.Bias circuit 60 produces a bias voltage signal V _BAnd transfer to the detecting voltage end DET that detects lateral circuit 50, in order to the detecting feedback voltage V _FAnd avoid detecting voltage V _DETWave distortion.Wherein, bias voltage signal V _BWith adjustment signal I _BProportional.Bias circuit 60 comprises one first electric crystal 65, one second electric crystal 61, a current source 62 and one first resistance 63.The source electrode of first electric crystal 65 couples the detecting voltage end DET of circuit for detecting 50, in order to produce bias voltage signal V _B, the drain of first electric crystal 65 is to couple supply voltage V _CC, the gate of first electric crystal 65 then couples first resistance 63.First resistance 63 receives adjusts signal I _B, be used to produce the gate of a bias voltage, so bias voltage signal V in first electric crystal 65 _BProportional with bias voltage, that is with adjust signal I _BProportional.For the gate that compensates first electric crystal 65 to the voltage between the source electrode, second electric crystal 61 is connected with first resistance 63.The source electrode that the gate of second electric crystal 61 and drain all couple first resistance, 63, the second electric crystals 61 then is coupled to earth terminal.Current source 62, it connects supply voltage V _CC, second electric crystal 61 gate and drain, give second electric crystal 61 to supply with bias voltage.

In order to detect feedback voltage V _F, waveform detection circuit 100 couples detecting voltage end DET, with sense feedback voltage V _FAnd according to feedback voltage V _FProduce a sample signal V _AWith the second signal S _DSError amplifier 67, one positive input terminal receive a reference voltage V _REF, a negative input end of error amplifier 67 then couples waveform detection circuit 100 and receives sample signal V _A, error amplifier 67 is according to sample signal V _AAnd export the first signal V at an output _FBError amplifier 67 is a transduction amplifier (trans-conduc tanceamplifier), wherein the output of error amplifier 67 more is coupled to the compensation end COM of controller, compensation end COM is to be coupled with building-out capacitor 24 to provide frequency compensation to error amplifier 67 to see through compensation end COM as shown in Figure 1.

Seeing also Fig. 7, is the circuit diagram of the waveform detection circuit of a preferred embodiment of the present invention.As shown in the figure, waveform detection circuit 100 of the present invention includes one first sampling switch 151, and the one end couples the detecting voltage end DET of circuit for detecting 50, in order to the sampling feedback voltage V _FOne first sampling capacitor 161, it is coupled between the other end and earth terminal of first sampling switch 151, the signal of being taken a sample with nip first sampling switch 151.One second sampling switch 150, it is coupled between first sampling capacitor 161 and one second sampling capacitor 160, with the signal of 161 nips of periodic sampling first sampling capacitor, and the signal of this first sampling capacitor of take a sample is sent to second sampling capacitor 160.Wherein, second sampling switch 150 is controlled by the periodic pulse wave signal PLS of oscillating circuit 31, and first sampling switch 151 then is controlled by controlling signal V _G

Controlling signal V _GBe to be sent to a pulse wave to produce circuit 140 through an inverter 102.One input of inverter 102 receives controlling signal V _GOne output of inverter 102 then couples the input IN that pulse wave produces circuit 140, the output OUT that pulse wave produces circuit 140 produces a pulse wave signal with via an inverter 105 controls first sampling switch 151, that is first sampling switch 151 is at controlling signal V _GWhen ending, the sampling feedback voltage V _FTo first sampling capacitor 161, so can be according to feedback voltage V _FProduce sample signal V at second sampling capacitor 160 _A

One second trigger 159, one clock pulse input couples the output of inverter 102, is used for via inverter 102 according to controlling signal V _G, to produce the second signal S at an output _DS, controlling signal V _GBe used for when ending the conducting second signal S _DSOne second comparator 155, one positive input terminal couple the detecting voltage end DET of circuit for detecting 50, and a negative input end of second comparator 155 then receives a critical voltage V _TH, second comparator 155 is used for according to critical voltage V _THCompare feedback voltage V _FAnd producing a replacement signal, the replacement signal is used for via one or lock 156 and one and lock 158 second trigger 159 of resetting, so in case feedback voltage V _FSubcritical voltage V _THThe time, the second signal S of second trigger, 159 outputs _DSTo be cut off.One output of the second above-mentioned comparator 155 is to be coupled to or an input of lock 156, or another input of lock 156 then receives controlling signal V _GOr an output of lock 156 is to couple and an input of lock 158, and another input of lock 158 couples an output of an inverter 157, one input of inverter 157 receives pulse wave signal PLS, so can extremely reach lock 158 by transmission pulse signal PLS, an output that reaches lock 158 connects a replacement input of second trigger 159, in order to second trigger 159 of resetting.

Seeing also Fig. 8, is the circuit diagram of the adjustment circuit of a preferred embodiment of the present invention.As shown in the figure, adjustment circuit 55 of the present invention includes a charge switch 81, and one first end couples supply voltage V _CCOne the 3rd sampling capacitor 84, it is coupled between one second end and earth terminal of charge switch 81, in order to 84 chargings reach a set point to the 3rd sampling capacitor, for example supplies voltage V _CCCharge switch 81 is controlled by controlling signal V _GSo the 3rd sampling capacitor 84 is at controlling signal V _GConduction period is preestablished.One discharge switch 82, one first end couples the 3rd sampling capacitor 84, the discharge switch 82 controlled second signal S that are formed on _DS, to be used to allowing the 3rd sampling capacitor 84 at the second signal S _DSDischarge during conducting.Because one second end of discharge switch 82 is to be connected in series with a discharging current source 83, so the 3rd sampling capacitor 84 is by 83 discharges of discharging current source, one the 3rd sampling switch 87, it is coupled between the 3rd sampling capacitor 84 and one the 4th sampling capacitor 89, the 3rd sampling switch 87 periodically from the 3rd sampling capacitor 84 sample signal, and is sent to the 4th sampling capacitor 89 with the signal of take a sample the 3rd sampling capacitor according to pulse wave signal PLS.

One voltage is to signal circuit 80, and it includes an amplifier 86, one second resistance 85, one the 3rd electric crystal 90 and a current mirror, produces in order to the signal according to the 4th sampling capacitor 89 and adjusts signal I _BCurrent mirror includes one the 4th electric crystal 91 and one the 5th electric crystal 92.Amplifier 86, one positive input terminal couple the 4th sampling capacitor 89.Second resistance 85, its two ends couple a negative input end and the earth terminal of amplifier 86 respectively, one output of amplifier 86 is the gates that couple the 3rd electric crystal 90, in order to according to the signal of the 4th sampling capacitor 89 and the resistance value of second resistance 85, produces one first electric current I ₉₀, first electric current I ₉₀Result from the drain of the 3rd electric crystal 90, the source electrode of the 3rd electric crystal 90 is coupled to a negative input end of amplifier 86.

Current mirror, it is in order to foundation first electric current I ₉₀Produce and adjust signal I _BSo, adjust signal I _BCan say so according to controlling signal V _GPulse bandwidth produce.In addition, in order to save power supply, one the 6th electric crystal 93 connects current mirrors, in order at controlling signal V _GEnd during conducting and adjust signal I _BThe source electrode of electric crystal 91,92,93 all couples supply voltage V _CC, the gate of electric crystal 91,92 is coupled in the drain of electric crystal 90,91,93, and the drain of the 5th electric crystal 92 is to produce to adjust signal I _BThe gate of the 6th electric crystal 93 couples one or an output of lock 95, or a first input end of lock 95 and one second input receive controlling signal V respectively _GWith the second signal S _DSSo as can be known, adjust signal I _BAlso with the second signal S _DSRelevant, that is the second signal S _DSAdjusting signal IB when reduce the discharge time of represented transformer 10 then increases, in addition as can be known by the explanation of above-mentioned Fig. 6, and bias voltage signal V _BBe and adjustment signal I _BIn direct ratio, and adjust signal I _BWith the second signal S _DSBe inverse proportion, so bias voltage signal V _BAlso inversely proportional with the discharge time of transformer 10, that is to say bias voltage signal V when reduce the discharge time of transformer 10 _BThen increase.

Seeing also Fig. 9, is the detecting voltage V that power converter of the present invention is produced down in light-load state _DETOscillogram.As shown in the figure, bias voltage signal V _BBe to be added on detecting voltage end DET, detecting voltage V _DETCan be expressed as:

$V_{\mathrm{DET}}=V_F\×(1-e^{\frac{-t}{R\×C}})+V_B---\left(2\right)$

According to equation (2), t can be expressed as:

$t=R\×C\×\ln \left(\frac{V_F}{V_F-V_{\mathrm{DET}}+V_B}\right)---\left(3\right)$

Wherein, R is the resistance value of resistance 22; C is the capacitance of parasitic capacitance 23; T is detecting voltage V _DETCharge to and equal feedback voltage V _FCycle time.The present invention is by increasing bias voltage signal V _B, and reduce detecting voltage V _DETRise time, so controller can detect feedback voltage V easily _F

In sum, the control circuit of power converter of the present invention, it is used to detect the feedback voltage of the transformer of power converter, and the output of adjusting power converter.Control circuit of the present invention includes switch and controller, and controller includes commutation circuit and circuit for detecting, and switch is to be coupled to transformer and to be used for switching transformer; Circuit for detecting is to couple transformer, produces first signal with the feedback voltage of detecting transformer according to feedback voltage; Commutation circuit then couples circuit for detecting, and to produce controlling signal according to first signal, controlling signal is used for control switch and switching transformer, to adjust the output of power converter.In addition, circuit for detecting more produces the bias voltage signal, to help the detecting feedback voltage, so can improve the accuracy of detecting feedback voltage and the output that can adjust power converter really.

The above, it only is a preferred embodiment of the present invention, be not to be used for limiting scope of the invention process,, all should be included in the claim of the present invention so all equalizations of doing according to the described shape of the present patent application claim, structure, feature and spirit change and modify.

Claims (7)

1. the control circuit of a power converter is characterized in that, includes:

One switch is coupled to a transformer of this power converter, to switch this transformer;

One circuit for detecting couples this transformer, detects a feedback voltage of this transformer, produces one first signal and one second signal according to this feedback voltage;

One switches circuit, couples this circuit for detecting, produces a controlling signal according to this first signal, to control the output that this switch switches this transformer and adjusts this power converter;

One adjusts circuit, produces one according to this second signal and adjusts signal, and be sent to this circuit for detecting;

Wherein, this circuit for detecting produces a bias voltage signal, to detect this feedback voltage.

2. control circuit as claimed in claim 1 is characterized in that, this commutation circuit more includes:

One blanking circuit produces a blanking signal according to this controlling signal, and this blanking signal is guaranteed the minimum ON time of this controlling signal when conducting.

3. control circuit as claimed in claim 1 is characterized in that, this circuit for detecting includes:

One bias circuit couples this adjustment circuit, produces this bias voltage signal and is sent to a detecting voltage end of this circuit for detecting according to this adjustment signal, and this detecting voltage end couples this transformer and detects this feedback voltage, and it is proportional that this bias voltage signal and this are adjusted signal;

One waveform detection circuit couples this detecting voltage end, detects this feedback voltage, to produce a sample signal and this second signal according to this feedback voltage;

One error amplifier receives a reference voltage and this sample signal, to produce this first signal according to this sample signal.

4. control circuit as claimed in claim 3 is characterized in that, this bias circuit includes:

One first electric crystal couples this detecting voltage end of this circuit for detecting, produces this bias voltage signal;

One first resistance couples this adjustment circuit and receives this adjustment signal and couple this first electric crystal, produces a bias voltage and controls this first electric crystal;

Wherein, this first electric crystal produces this bias voltage signal according to this bias voltage, and this bias voltage signal and this bias voltage are proportional.

5. control circuit as claimed in claim 3 is characterized in that, this waveform detection circuit includes:

One first sampling switch couples this detecting voltage end of this circuit for detecting, this feedback voltage of taking a sample;

One first sampling capacitor couples this first sampling switch, the signal that this first sampling switch of nip is taken a sample;

One second sampling capacitor;

One second sampling switch, be coupled between this first sampling capacitor and this second sampling capacitor, signal with this first sampling capacitor of periodic sampling, and the signal of this first sampling capacitor of take a sample is sent to this second sampling capacitor and produces a sample signal, this second sampling capacitor promptly produces this sample signal according to this feedback voltage;

One second trigger produces this second signal according to this controlling signal, this then conducting of second signal when this controlling signal is ended;

One second comparator couples this detecting voltage end of this circuit for detecting and receives a threshold voltage, and relatively this threshold voltage and this feedback voltage produce a replacement signal and be sent to this second trigger, to end this second signal.

6. control circuit as claimed in claim 1 is characterized in that, this adjustment circuit includes:

One charge switch couples a supply voltage, and the switching of this charge switch is controlled by this controlling signal;

One the 3rd sampling capacitor couples this charge switch, and this charge switch allows the 3rd sampling capacitor charge to a set point when this controlling signal conducting;

One discharging current source;

One discharge switch is coupled between this discharging current source and the 3rd sampling capacitor, and the switching of this discharge switch is controlled by this second signal, and this discharge switch allows the 3rd sampling capacitor via this discharging current source discharge when this second signal conducting;

One the 4th sampling capacitor;

One the 3rd sampling switch is coupled between the 3rd sampling capacitor and the 4th sampling capacitor, the signal of the 3rd sampling capacitor of periodically taking a sample, and the signal of take a sample the 3rd sampling capacitor is sent to the 4th sampling capacitor;

One voltage couples the 4th sampling capacitor to signal circuit, produces this adjustment signal according to the signal of the 4th sampling capacitor.

7. control circuit as claimed in claim 6 is characterized in that, this voltage includes signal circuit:

One amplifier, the one positive input terminal couples the 4th sampling capacitor;

One second resistance couples a negative input end and an earth terminal of this amplifier;

One the 3rd electric crystal couples an output and this negative input end of this amplifier, produces one first electric current according to the signal of the 4th sampling capacitor and the resistance value of this second resistance;

One current mirror couples the 3rd electric crystal, produces this adjustment signal according to this first electric current.

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