Background technology
At present, in Switching Power Supply, because the scope of AC-input voltage is conventionally at 85VAC~265VACBetween variation, and there is certain delay in control system, so that under different input voltages, maximum outputPower has very large deviation, is unfavorable for accurate control.
Taking inverse-excitation type switch power-supply as example, Fig. 1 shows the maximum output of existing inverse-excitation type gauge tap power supplyThe structure of power circuit, comprising: oscillator 11, logic controller 12, drive circuit 13, comparisonDevice 14, transformer T1, the first switching tube HN1, diode D1, capacitor C 1, resistance R 1 and resistanceR2;
The input of the output andlogic control device 12 of oscillator 11 connects, the output of logic controller 12End is connected with the input of drive circuit 13, the control of the output of drive circuit 13 and the first switching tube HN1System end connects, and the output of the first switching tube HN1 passes through resistance R 2 ground connection, the first switching tube HN1 and electricityThe link of resistance R2 is connected with the positive input of comparator 14, and the reverse input end of comparator 14 is with outsideReference cell 15 connects, and the control end of the output andlogic control device 12 of comparator 14 connects, and first opensThe input that closes pipe HN1 is connected with the Same Name of Ends of transformer T1 primary coil Np, transformer T1 primary coilThe input V that the different name end of Np is switching power circuitinBe connected T1 level of transformer with external ac power sourceThe different name end ground connection of coil Ns, the Same Name of Ends of transformer T1 secondary coil Ns and the anodic bonding of diode D1,The negative electrode of diode D1 is by capacitor C 1 ground connection, and resistance R 1 is in parallel with capacitor C 1, resistance R 1 and diodeThe output V that one end that D1 connects is switching power circuitoutPower output.
Oscillator 11 is controlled the first switching tube HN1 conducting by logic controller 12 and drive circuit 13,In the time of the first switching tube HN1 conducting, the linear rising of electric current on transformer T1 primary coil Np, elementaryThe inductance power storage that coil Np and magnetic core form, now power output maintains by capacitor C 1.
In the time that the voltage of resistance R 2 ends rises to reference voltage V ref, comparator 14 overturns, by logic controlDevice 12 processed and drive circuit 13 are controlled the first switching tube HN1 and are turn-offed. When closing, the first switching tube HN1 has no progeny,The linear decline of electric current on secondary coil Ns, by discharging energy after diode D1, capacitor C 1 rectifying and wave-filteringAmount, to output loading R1, ensures power demand.
The formula of power output is:Wherein Lp be transformer T1 primary coil withThe primary inductance value that magnetic core forms, Ip is the current peak on primary inductance, f is switching frequency, andIp=Vref/R2。
Because existing switching power circuit exists transmission delay and switching delay, therefore when the voltage in resistance R 2When value reaches Vref, the first switching tube HN1 also needs could turn-off after a period of time, and Ip is slightly larger thanDefault peak point current, and power output PoutBecome square proportional with Ip, therefore power output PoutBecomeChanging can be larger.
For the compensation of inverse-excitation type switch power-supply, the first adopts input voltage V at presentinSampling compensation, i.e. rootAccording to VinVariation adjust and flow into the electric current of resistance R 2 or adjust the magnitude of voltage of Vref, with eliminate postpone rightThe impact that Ip produces. But this method can increase the pin of control chip, also can lower efficiency simultaneously.
It two is that the size of utilizing feedback loop to control primary inductance peak point current compensates. But thisThe gain of method loop is smaller, still can cause design load and actual value to have certain deviation, and adoptThe time point of sample is not easy to control, and can produce equally deviation.
Summary of the invention
The object of the embodiment of the present invention is to provide a kind of Switching Power Supply power compensating circuit, is intended to solve existingThe problem that power compensating circuit pin is many, efficiency is low, compensation effect is poor.
The embodiment of the present invention is achieved in that a kind of Switching Power Supply power compensating circuit, described power back-offCircuit is connected with sampling output and the FEEDBACK CONTROL end of outside reference unit and switching power circuit, described inPower compensating circuit comprises:
Sampling logical block, the input of described sampling logical block and the sampling of described switching power circuit are defeatedGo out end and connect, for generating sampling control signal according to logic control signal;
Sample holding unit, the output of the control end of described sample holding unit and described sampling logical blockConnect, the input of described sample holding unit is connected with the FEEDBACK CONTROL end of described switching power circuit, usesIn taking described sampling control signal as clock, primary inductance peak point current in by described switching power circuit being generatedSampled voltage carry out sampling processing, output sampling processing signal;
Amplifier unit, the positive input of described amplifier unit is connected with described reference cell, described amplifier listThe reverse input end of unit is connected with the output of described sample holding unit, for by described sampling processing signalCarry out error amplification, output error amplifying signal with the reference signal that described reference cell generates;
Energy-storage units, the input of described energy-storage units is connected with the output of described amplifier unit, described storageThe output head grounding of energy unit, for carrying out charge or discharge according to described error amplification signal, to regulateState the voltage of error amplification signal;
Comparator, the positive input of described comparator is connected with the input of described energy-storage units, described ratioBe connected with the sampling output of described switching power circuit compared with the reverse input end of device, for described sampling is electricDescribed error amplification signal after pressing and regulating compares, and output compensating control signal, to compensate primary electricalSense peak point current and then compensation power, comparator described in the variable effect of described error amplification signal magnitude of voltageThe hop period of flip-flop transition and described logic control signal;
Clamper unit, the input of described clamper unit is connected with the positive input of described comparator, forDescribed error amplification signal is carried out to clamper.
Another object of the embodiment of the present invention is to provide a kind of power supply chip, the switch in described power supply chipThe sampling output of power compensating circuit and reference cell and switching power circuit and FEEDBACK CONTROL end connectConnect, described power compensating circuit comprises:
Sampling logical block, the input of described sampling logical block and the sampling of described switching power circuit are defeatedGo out end and connect, for generating sampling control signal according to logic control signal;
Sample holding unit, the output of the control end of described sample holding unit and described sampling logical blockConnect, the input of described sample holding unit is connected with the FEEDBACK CONTROL end of described switching power circuit, usesIn taking described sampling control signal as clock, primary inductance peak point current in by described switching power circuit being generatedSampled voltage carry out sampling processing, output sampling processing signal;
Amplifier unit, the positive input of described amplifier unit is connected with described reference cell, described amplifier listThe reverse input end of unit is connected with the output of described sample holding unit, for by described sampling processing signalCarry out error amplification, output error amplifying signal with the reference signal that described reference cell generates;
Energy-storage units, the input of described energy-storage units is connected with the output of described amplifier unit, described storageThe output head grounding of energy unit, for carrying out charge or discharge according to described error amplification signal, to regulateState the voltage of error amplification signal;
Comparator, the positive input of described comparator is connected with the input of described energy-storage units, described ratioBe connected with the sampling output of described switching power circuit compared with the reverse input end of device, for described sampling is electricDescribed error amplification signal after pressing and regulating compares, and output compensating control signal, to compensate primary electricalSense peak point current and then compensation power, comparator described in the variable effect of described error amplification signal magnitude of voltageThe hop period of flip-flop transition and described logic control signal;
Clamper unit, the input of described clamper unit is connected with the positive input of described comparator, forDescribed error amplification signal is carried out to clamper.
The embodiment of the present invention is by the peak point current on feedback loop control primary inductance Lp, and increase ringRoad gain, accurate optimization sampling time point, make design load and the actual value of primary inductance peak point current IpDeviation is very little, on the basis that does not additionally increase chip pin and reduction system effectiveness, has compensated power output.
Detailed description of the invention
In order to make object of the present invention, technical scheme and advantage clearer, below in conjunction with accompanying drawing and realityExecute example, the present invention is further elaborated. Only should be appreciated that specific embodiment described hereinOnly, in order to explain the present invention, be not intended to limit the present invention.
The embodiment of the present invention is by the peak point current on feedback loop control primary inductance Lp, and increase ringRoad gain, accurate optimization sampling time point, additionally do not increasing chip pin and reducing the base of system effectivenessOn plinth, compensate power output.
Fig. 2 illustrates the structure of the Switching Power Supply power compensating circuit that the embodiment of the present invention provides, for the ease of sayingBright, only show part related to the present invention.
Switching power circuit 1 comprises: oscillator 11, logic controller 12, drive circuit 13, transformerT1, the first switching tube HN1, diode D1, capacitor C 1, resistance R 1 and resistance R 2;
The input of the output andlogic control device 12 of oscillator 11 connects, the control of logic controller 12End is the FEEDBACK CONTROL end of switching power circuit, the output of logic controller 12 and drive circuit 13 defeatedEnter end and connect, the output of drive circuit 13 is connected with the control end of the first switching tube HN1, the first switchThe output of pipe HN1 is by resistance R 2 ground connection, and the link of the first switching tube HN1 and resistance R 2 is samplingOutput, the input of the first switching tube HN1 is connected with the Same Name of Ends of transformer T1 primary coil Np, becomesThe input V that the different name end of depressor T1 primary coil Np is switching power circuitinConnect with external ac power sourceConnect the different name end ground connection of transformer T1 secondary coil Ns, the Same Name of Ends and two of transformer T1 secondary coil NsThe anodic bonding of utmost point pipe D1, the negative electrode of diode D1 is by capacitor C 1 ground connection, and resistance R 1 and capacitor C 1 are alsoConnection, the output V that one end that resistance R 1 is connected with diode D1 is switching power circuitoutPower output.
The Switching Power Supply power compensating circuit 2 and the outside reference unit 15 that provide as one embodiment of the inventionAnd the sampling output of switching power circuit 1 is connected with FEEDBACK CONTROL end, can be integrated in various power supply coresIn sheet, this Switching Power Supply power compensating circuit 2 comprises:
Sampling logical block 21, the sampling of the input of this sampling logical block 21 and switching power circuit 1Output connects, for generating sampling control signal SAM_CLK according to logic control signal Ton;
Sample holding unit 22, the output of the control end of this sample holding unit 22 and sampling logical block 21End connects, and the input of sample holding unit 22 is connected with the FEEDBACK CONTROL end of switching power circuit 1, forTaking sampling control signal SAM_CLK as clock to by primary inductance peak point current Ip in switching power circuit 1The sampled voltage CS generating carries out sampling processing, output sampling processing signal CS_SAM;
Amplifier unit 23, the positive input of this amplifier unit 23 is connected with outside reference unit 15, amplifierThe reverse input end of unit 23 is connected with the output of sample holding unit 22, for by sampling processing signalThe reference signal V that CS_SAM and reference cell 15 generateREFCarry out error amplification, output error amplifying signalCS_COMP;
Energy-storage units 24, the input of this energy-storage units 24 is connected with the output of amplifier unit 23, energy storageThe output head grounding of unit 24, for carrying out charge or discharge according to error amplification signal CS_COMP, withThe voltage of regulating error amplifying signal CS_COMP;
As one embodiment of the present invention, energy-storage units 24 can be capacitor C 2, the two ends of capacitor C 2Be respectively input and the output of energy-storage units 24.
Certainly, then when integrated level is had relatively high expectations, energy-storage units 24 also can adopt metal-oxide-semiconductor to realize.
As one embodiment of the present invention, amplifier unit 23 and energy-storage units 24 can directly adopt oneIntegral amplifier (PID) or other have the unit of same function to realize, the positive input of this integral amplifierFor the positive input of amplifier unit 23, the reverse input end of integral amplifier is the reverse of amplifier unit 23Input, the output of integral amplifier is the output of energy-storage units 24.
Comparator 25, the positive input of this comparator 25 is connected with the input of energy-storage units 24, relativelyThe reverse input end of device 25 is connected with the sampling output of switching power circuit 1, for by sampled voltage CSCompare with the error amplification signal CS_COMP after regulating, output compensating control signal, at the beginning of compensatingLevel inductance peak point current Ip and then compensation power;
Clamper unit 26, the input of this clamper unit 26 is connected with the positive input of comparator 25, usesIn error amplification signal CS_COMP is carried out to clamper.
In embodiments of the present invention, to the sampled voltage CS sampling processing being generated by primary inductance peak point current IpFor sampling processing signal CS_SAM, and by sampling processing signal CS_SAM and default reference signal VREFCompare this reference signal VREFThe power calculation that can obtain by expectation by outside reference unit 15Generate, by sampling processing signal CS_SAM and reference signal VREFError amplify result regulating error and putThe magnitude of voltage of large-signal CS_COMP, and due to the variation meeting shadow of error amplification signal CS_COMP magnitude of voltageRing the flip-flop transition of comparator 25, and then affect the hop period of logic control signal Ton, and then regulate passThe bound-time of break signal NG, to control the ON time of the first switching tube HN1, at the beginning of final realization regulatesLevel inductance peak point current Ip, realizes the compensation to power.
The embodiment of the present invention is by the peak point current on feedback loop control primary inductance Lp, and increase ringRoad gain, accurate optimization sampling time point, make design load and the actual value of primary inductance peak point current IpDeviation is very little, on the basis that does not additionally increase chip pin and reduction system effectiveness, has compensated power output.
Further the embodiment of the present invention is made an explanation below in conjunction with Fig. 3 and Fig. 4.
In Fig. 3, in first switch periods, first logic control signal Ton uprises, the first switching tube HN1Open, primary inductance electric current I p is linear to rise, and sampled voltage CS is linear rising also. Because clamped circuit 26Clamping action, there is an Initial Voltage Value CS_COMP1 in the positive input of comparator 25. When sampling electricityWhen the magnitude of voltage of pressure CS reaches Initial Voltage Value CS_COMP1, logic control signal Ton signal is dragged down,But owing to there being the Td time between logic control signal Ton and the cut-off signals NG of the first switching tube HN1Postpone, so sampled voltage CS can continue rising, until cut-off signals NG is dragged down. Sample holding unitThe magnitude of voltage in 22 these moment of sampling, and sampling processing is signal CS_SAM1.
Voltage difference between CS_SAM1 and CS_COMP1 is formulated as:
Wherein R2 is the resistance of resistance R 2, VinFor the magnitude of voltage of input voltage, Lp is the elementary line of transformer T1The primary inductance value that circle and magnetic core form, when Td is the delay of logic control signal Ton and cut-off signals NGBetween.
As input voltage VinWhen variation, Δ V can change, and the variation of Δ V has directly reflected primary inductance peakThe deviation of value electric current I p and setting value. Change in order to eliminate input voltage the impact producing, by first switchThe sampling processing signal CS_SAM1 in cycle and default reference voltage VREFCompare. When sampling processing letterNumber CS_SAM1 is greater than reference voltage VREFTime, amplifier unit 23 discharges to capacitor C 2, the value of CS_COMPWill diminish, as shown in Figure 3 the signal waveform of CS_COMP2.
In second switch periods, in the time that sampled voltage CS rises to the value of CS_COMP1, logic controlSignal Ton is dragged down, and through the delay of Td, cut-off signals NG is dragged down, and record signal is nowCS_SAM2, and by CS_SAM2 and reference voltage VREFRelatively.
If the value of CS_SAM2 is greater than the value of VREF, continues to repeat second the 3rd switch periods and openThe action in pass cycle, until sampling processing signal equates with reference voltage, negative anti-by several switch periodsFeedback regulates, when the first switching tube HN1 turn-offs, and sampled voltage CS and internal reference voltage VREFValue reach oneCause, and owing to having added the amplifier unit 23 of a high-gain in loop, make sampled voltage CS with defaultMagnitude of voltage is consistent, and therefore means that primary inductance electric current I p has compensated to design load.
If the magnitude of voltage of the sampling processing signal CS_SAM1 of first switch periods is less than reference voltage VREF,By amplifier unit 23, capacitor C 2 is charged, increase the value of CS_COMP1, to extend the first switching tubeThe ON time of HN1, regulates sampled voltage CS to increase, and in second switch periods, continues relatively samplingProcessing signals CS_SAM1 and reference voltage VREFIf the magnitude of voltage of CS_SAM is still less than VREF, soContinue to adjust sampled voltage CS and increase, until several all after date CS_SAM1 and VREFEquate, make sampled voltageCS and default magnitude of voltage are consistent, and to primary inductance electric current I, p compensates to design load, and it is stable that system reaches.
In Fig. 4, Ton_D is the trailing edge inhibit signal of logic control signal Ton, and be t1 time delay,The time that the sampling control signal SAM_CLK that sample holding unit 21 is exported maintains high level is t2, sampling controlThe moment that signal SAM_CLK processed is corresponding with the trailing edge of cut-off signals NG is consistent, therefore can ensure eachIt is upper that sampling is accurate to turn-off time point, and ensure that the time of t1 is less than trailing edge and the pass of logic control signal TonTd time delay of the trailing edge of break signal NG.
Owing to producing sampling control signal according to the trailing edge of the trailing edge of signal TON_D and cut-off signals NGSAM_CLK, and control to produce and postpone to be the technology that the art is comparatively ripe, no longer superfluous hereinState.
Another object of the embodiment of the present invention is to provide a kind of power supply chip, the switch in described power supply chipThe sampling output of power compensating circuit and reference cell and switching power circuit and FEEDBACK CONTROL end connectConnect, described power compensating circuit comprises:
Sampling logical block, the sampling input of logical block and the sampling output of switching power circuit are connected,For generating sampling control signal according to logic control signal;
Sample holding unit, the control end of sample holding unit is connected with the output of sampling logical block, adoptsThe input of sample holding unit is connected with the FEEDBACK CONTROL end of switching power circuit, for sampling control signalFor clock carries out sampling processing to the sampled voltage being generated by primary inductance peak point current in switching power circuit,Output sampling processing signal;
Amplifier unit, the positive input of amplifier unit is connected with reference cell, the reverse input of amplifier unitEnd is connected with the output of sample holding unit, for by the benchmark of sampling processing signal and reference cell generationSignal carries out error amplification, output error amplifying signal;
Energy-storage units, the input of energy-storage units is connected with the output of amplifier unit, the output of energy-storage unitsEnd ground connection, for carrying out charge or discharge according to error amplification signal, with the voltage of regulating error amplifying signal;
As one embodiment of the invention, this energy-storage units is capacitor C 2, and the two ends of capacitor C 2 are respectively energy storageThe input of unit and output.
Amplifier unit and energy-storage units can directly adopt an integral amplifier (PID) or other to have on an equal basisThe unit of function is realized, and the positive input of this integral amplifier is the positive input of amplifier unit, integrationThe reverse input end of amplifier is the reverse input end of amplifier unit, and the output of integral amplifier is energy storage listThe output of unit.
Comparator, the positive input of comparator is connected with the input of energy-storage units, comparator oppositely defeatedEnter end and be connected with the sampling output of switching power circuit, amplify for the error by sampled voltage and after regulatingSignal compares, and output compensating control signal, to compensate primary inductance peak point current and then compensation power;
Clamper unit, the input of clamper unit is connected with the positive input of comparator, for error is putLarge-signal is carried out clamper.
The embodiment of the present invention is by the peak point current on feedback loop control primary inductance Lp, and increase ringRoad gain, accurate optimization sampling time point, make design load and the actual value of primary inductance peak point current IpDeviation is very little, on the basis that does not additionally increase chip pin and reduction system effectiveness, has compensated power output.
The foregoing is only preferred embodiment of the present invention, in order to limit the present invention, not all at thisAny amendment of doing within bright spirit and principle, be equal to and replace and improvement etc., all should be included in the present inventionProtection domain within.