One compares certainly, self-oscillation DC-DC circuitTechnical field
The present invention relates to electronic circuit field, particularly relate to a kind of from comparing, self-oscillation DC-DC circuit.
Background technology
DC/DC circuit is a kind of switching power circuit, and it utilizes the energy storage characteristic of electric capacity and inductance, by gate-controlled switch (asMOSFET etc.) carry out the action of HF switch, by inner at electric capacity (sense) for the electrical power storage of input, when the switches are opened, electricLoad can be released to again, provide energy for load.Power or the ability of voltage that DC/DC circuit is exported are relevant with dutycycle,Dutycycle is the ratio of switch conduction times and the cycle of whole switch.
As it is shown in figure 1, Fig. 1 is traditional buck DC-DC circuit, this kind of DC-DC circuit typically has the most several askingTopic:
(1) in traditional DC-DC circuit, generally use diode rectification, and the forward conduction voltage drop of diode be relatively big,Switching process occurs substantial amounts of loss.For improving the conversion efficiency of DC-DC, reduce the loss of DC-DC circuit, can basisSynchronous rectification, the power MOSFET using on state resistance extremely low replaces commutation diode.
Owing to the two switch metal-oxide-semiconductor generally uses same control signal, the phenomenon simultaneously turned on easily occurs, causes substantial amounts of meritRate is lost.
(2) in traditional DC-DC circuit, it usually needs use agitator to carry out output clock pulse signal and other is with frequency letterNumber, this adds the package area that chip takies undoubtedly, adds chip cost, will also result in certain power attenuation simultaneously.
(3) traditional DC-DC circuit structure is complicated, when circuit is integrated, can take bigger package area, increase chipCost of manufacture.
(4) in Power Management Design, transient response speed and conversion efficiency are all crucial technical specifications.The most this changeThe advantage of parallel operation is that efficiency is the highest, but response speed is slower, on the one hand, inductive current rise/fall slope is limited by input and outputVoltage, can not quickly change output electric current under transient state step, and on the other hand, the loop bandwidth of switch converters is generally below openedClosing 1/5th of frequency, limited by switching frequency, the loop response time is long.
(5) traditional DC-DC circuit power consumption is high, efficiency is low, and electromagnetic interference EMI is high, and the EMI that is also configured with having processes mouldBlock.
Summary of the invention
It is an object of the invention to overcome the deficiencies in the prior art, it is provided that one compares certainly, self-oscillation DC-DC circuit, self-oscillation,Without additional configuration agitator, certainly comparing, power consumption is little, efficiency is high, fast response time, electromagnetic interference EMI is low, without EMIProcessing module, circuit structure is simple, and package area is little, and chip cost is low.
It is an object of the invention to be achieved through the following technical solutions: a kind of from comparing, self-oscillation DC-DC circuit, it includesSwitch driver, switch metal-oxide-semiconductor M1, switch metal-oxide-semiconductor M2, energy storage inductor L1, storage capacitor C1, triangular wave generateCircuit, error amplifying circuit and hysteresis comparator circuit.
The source electrode of described switch metal-oxide-semiconductor M1 is connected with DC source Vin, the drain electrode of switch metal-oxide-semiconductor M1, switch MOSThe drain electrode of pipe M2 and the first input end of triangular wave generating circuit all one end with energy storage inductor L1 are connected, and switch metal-oxide-semiconductorThe grid of the grid of M1 and switch metal-oxide-semiconductor M2 is connected with the first outfan and second outfan of switch driver respectively, opensClose the source electrode of metal-oxide-semiconductor M2 with dock, the other end of energy storage inductor L1 respectively with positive pole, the triangular wave of storage capacitor C1Second input of generative circuit, the first input end of error amplifying circuit and load connect, the negative pole of storage capacitor C1 and groundDocking.
The outfan of described triangular wave generating circuit is connected with the first input end of hysteresis comparator circuit, and triangular wave generating circuit is usedTriangular signal V is generated in the voltage according to energy storage inductor L1 two endsFB_RC。
Second input of described error amplifying circuit and reference voltage VREFInput port connects, the output of error amplifying circuitEnd is connected with the second input of hysteresis comparator circuit；Error amplifying circuit is used for amplifying reference voltage VREFWith DC-DC circuitThe error of output voltage Vout, and signal of its output fluctuates along with the fluctuation of the output voltage Vout of DC-DC circuit.
The outfan of hysteresis comparator circuit is connected with the input of switch driver；Defeated by error amplifying circuit of hysteresis comparator circuitGo out signal and triangular signal VFB_RCCompare, to switch driver output switching signal.
Switch driver exports two-way non-overlapping clock control signal according to this switching signal by non-overlapping clock generating module, comesControl switch metal-oxide-semiconductor M1 and switch metal-oxide-semiconductor M2 respectively and carry out switch motion.
Described triangular wave generating circuit includes resistance R1 and filter capacitor C2, one end of described resistance R1 and energy storage inductor L1Input connect, the other end of resistance R1 is respectively with the first input end of the negative terminal of filter capacitor C2 and hysteresis comparator circuit evenConnecing, the positive pole of filter capacitor C2 is connected with the outfan of energy storage inductor L1.
Described hysteresis comparator circuit includes the first hysteresis comparator COMP1, the homophase of described first hysteresis comparator COMP1Input is connected with the first input end of hysteresis comparator circuit, the inverting input of the first hysteresis comparator COMP1 and sluggishness ratioSecond input of relatively circuit connects, and the outfan of the first hysteresis comparator COMP1 is connected with the outfan of hysteresis comparator circuit.
Described error amplifying circuit includes error amplifier EA1, the inverting input of described error amplifier EA1 and errorThe first input end of amplifying circuit connects, and the in-phase input end of error amplifier EA1 connects with the second input of error amplifying circuitConnecing, the outfan of error amplifier EA1 is connected with the outfan of error amplifying circuit.
The invention has the beneficial effects as follows:
1) present invention carry out self-oscillation process by triangular wave generating circuit and hysteresis comparator circuit, without additional configuration agitator,Power consumption is little, efficiency is high, fast response time.
2) present invention effectively reduces electromagnetic interference produced by switch metal-oxide-semiconductor and energy storage inductor, it is not necessary to the process of additional configuration EMIModule.
3) hysteresis comparator circuit in the present invention is by triangular signal VFB_RCDo with the error amplification signal of DC-DC output voltageRelatively, it is achieved that certainly compare, the signal of error amplifier output is as the change of DC-DC output voltage Vout and changes,So the switching signal that rest-set flip-flop exports continuously also can be the pulse combined according to certain dutycycle by low and high levelSignal, required gain is low, and response speed is faster, in hgher efficiency so that DC-DC output voltage Vout is more accurate.
4) in the present invention hysteresis comparator according to its thresholding broadband so that upper at hysteresis comparator of DC-DC output voltage VoutBetween threshold voltage and lower threshold voltage, it is generally slightly smaller than the intermediate value of its window voltage so that DC-DC output voltage VoutMore accurate.
5) output of the switch driver in present invention two-way non-overlapping clock control signal, controls to switch metal-oxide-semiconductor M1 respectivelyCarry out switch motion with switch metal-oxide-semiconductor M2, the phenomenon that simultaneously turning on occurs in switch metal-oxide-semiconductor can be prevented effectively from, it is to avoid causeSubstantial amounts of power attenuation.
6) circuit structure of the present invention is simple, and package area is little, and chip cost is low, good stability, and has certain portability.
Accompanying drawing explanation
Fig. 1 is traditional buck DC-DC circuit structure schematic diagram；
Fig. 2 is self-oscillation DC-DC circuit theory diagram of the present invention；
Fig. 3 is self-oscillation DC-DC circuit schematic diagram of the present invention.
Detailed description of the invention
Technical scheme is described in further detail below in conjunction with the accompanying drawings, but protection scope of the present invention is not limited to following instituteState.
As in figure 2 it is shown, a kind of from comparing, self-oscillation DC-DC circuit, it include switch driver, switch metal-oxide-semiconductor M1,Switch metal-oxide-semiconductor M2, energy storage inductor L1, storage capacitor C1, triangular wave generating circuit, error amplifying circuit and sluggishness compareCircuit.
In the present invention, switch metal-oxide-semiconductor M1 can be selected for PMOS, and switch metal-oxide-semiconductor M2 can be selected for NMOS tube.
The source electrode of described switch metal-oxide-semiconductor M1 is connected with DC source Vin, the drain electrode of switch metal-oxide-semiconductor M1, switch MOSThe drain electrode of pipe M2 and the first input end of triangular wave generating circuit all one end with energy storage inductor L1 are connected, and switch metal-oxide-semiconductorThe grid of the grid of M1 and switch metal-oxide-semiconductor M2 is connected with the first outfan and second outfan of switch driver respectively, opensClose the source electrode of metal-oxide-semiconductor M2 with dock, the other end of energy storage inductor L1 respectively with positive pole, the triangular wave of storage capacitor C1Second input of generative circuit, the first input end of error amplifying circuit and load connect, the negative pole of storage capacitor C1 and groundDocking.
The outfan of described triangular wave generating circuit is connected with the first input end of hysteresis comparator circuit, and triangular wave generating circuit is usedTriangular signal V is generated in the voltage according to energy storage inductor L1 two endsFB_RC。
Second input of described error amplifying circuit and reference voltage VREFInput port connects, the output of error amplifying circuitEnd is connected with the second input of hysteresis comparator circuit；Error amplifying circuit is used for amplifying reference voltage VREFWith DC-DC circuitThe error of output voltage Vout, and signal of its output fluctuates along with the fluctuation of the output voltage Vout of DC-DC circuit.
The outfan of hysteresis comparator circuit is connected with the input of switch driver；Defeated by error amplifying circuit of hysteresis comparator circuitGo out signal and triangular signal VFB_RCCompare, to switch driver output switching signal.
Switch driver exports two-way non-overlapping clock control signal according to this switching signal by non-overlapping clock generating module, comesControl switch metal-oxide-semiconductor M1 and switch metal-oxide-semiconductor M2 respectively and carry out switch motion.
The clock control signal that switch metal-oxide-semiconductor M1 and switch metal-oxide-semiconductor M2 inputs according to respective grid respectively, according to accordinglyFrequency DC source Vin is done voltage transformation, then by energy storage inductor L1 and storage capacitor C1 to the direct current after voltage transformationElectricity carries out voltage regulation filtering, finally output expectation voltage.
As it is shown on figure 3, described triangular wave generating circuit includes resistance R1 and filter capacitor C2, one end of described resistance R1Be connected with the input of energy storage inductor L1, the other end of resistance R1 respectively with negative terminal and the hysteresis comparator circuit of filter capacitor C2First input end connect, the positive pole of filter capacitor C2 is connected with the outfan of energy storage inductor L1, the output of energy storage inductor L1End is connected with load resistance R2.
Described hysteresis comparator circuit includes the first hysteresis comparator COMP1, the homophase of described first hysteresis comparator COMP1Input is connected with the first input end of hysteresis comparator circuit, the inverting input of the first hysteresis comparator COMP1 and sluggishness ratioSecond input of relatively circuit connects, and the outfan of the first hysteresis comparator COMP1 is connected with the outfan of hysteresis comparator circuit.
Described error amplifying circuit includes error amplifier EA1, the inverting input of described error amplifier EA1 and errorThe first input end of amplifying circuit connects, and the in-phase input end of error amplifier EA1 connects with the second input of error amplifying circuitConnecing, the outfan of error amplifier EA1 is connected with the outfan of error amplifying circuit.
Owing to the internal resistance of PMOS is the least, for resistance R1, its internal resistance is negligible, triangular wave generating circuitOutput voltage VFB_RCRate of rise slopeupComputing formula be:
In formula, the output voltage of Vin-DC source；
VOUTThe voltage of-DC-DC circuit output.
The output voltage V of triangular wave generating circuitFB_RCDescending slope slopedownComputing formula be:
In formula, VGND-earth terminal voltage, generally 0V.
From the rate of rise and the computing formula of descending slope, triangular signal VFB_RCThe rate of rise and descending slope withThe output voltage Vout of DC-DC circuit is relevant, and triangular wave generating circuit is according to the output voltage Vout of DC-DC circuit selfDetermine triangular signal VFB_RCSlope, comparison circuit is further according to this triangular signal VFB_RCSlope adjust its output openOFF signal square wave, so that DC-DC exports desired value.
The output voltage V of error amplifier EA1EAThe reference voltage V inputted with itREFWith DC-DC circuit output voltage VoutBetween relation, shown in formula calculated as below:
VEA=VREF+Av(VREF-VOUT)
In formula, the amplification of Av error amplifier.
By the output voltage V of error amplifierEAComputing formula understand, the output voltage of error amplifier and DC-DC output electricityVout is relevant for pressure, its output voltage VEAIt is as the change of DC-DC output voltage Vout and changes.
In the present invention, triangular wave generating circuit is that the output voltage Vout according to DC-DC circuit self determines triangular signalVFB_RCSlope；The voltage V of error amplifier outputEAAlso it is as the change of DC-DC output voltage Vout and changes；Hysteresis comparator circuit is by the triangular signal V relevant for output voltage Vout with selfFB_RCRelevant with self output voltage VoutVoltage VEACompare, and the characteristic being had due to hysteresis comparator itself, export relevant with self output voltage VoutAccording to the switching signal of certain dutycycle combination, the value of the high and low thresholds voltage of hysteresis comparator determines DC-DC circuit outputThe size of voltage Vout, and the thresholding pressure reduction of hysteresis comparator determines the precision of DC-DC circuit output voltage Vout, doorPressure limiting difference is the least, and the precision of output voltage Vout is the highest.
Switch driver controls switch metal-oxide-semiconductor M1 and the break-make of switch metal-oxide-semiconductor M2 according to this switching signal so that thisThe output of bright DC-DC circuit meets desired DC voltage Vout the most accurately so that DC-DC circuit output voltage VoutBetween Upper threshold voltage and the lower threshold voltage of hysteresis comparator.