CN202713146U - Peak current signal generation circuit and switching power supply circuit - Google Patents

Abstract

The utility model provides a peak current signal produces circuit and switching power supply circuit. The switching power supply circuit at least comprises a first power tube, and the peak current signal generating circuit comprises: a first current source; the peak capacitor is coupled with the first current source in parallel, and voltage signals at two ends of the peak capacitor are peak current signals; the first end and the second end of the low-pass filter circuit are respectively coupled to two ends of the peak capacitor, and the control end receives a pulse signal representing the switching period of the first power tube; the first switch, the first end couples to the third end of the low-pass filter circuit, the control end receives the reset signal; and a first voltage source, one end of which is coupled to the second end of the first switch, and the second end of which is coupled to the second end of the low-pass filter circuit. The peak current signal can be adjusted according to the load condition, so that the frequency of the switching power supply circuit is reduced along with the reduction of the load, and the generation of subharmonic oscillation is avoided.

Description

Peak-current signal produces circuit and switching power circuit

Technical field

The utility model relates to voltage conversion circuit, and more particularly, switching power circuit and peak-current signal thereof that the utility model relates in the voltage conversion circuit produce circuit.

Background technology

Switching power circuit reduces switching frequency usually when underloading, to obtain higher efficient.But switching frequency is crossed the low output ripple of switching power circuit that can cause and is become large, and can affect other performance of circuit.Especially in high-end step-down (High Side Buck) circuit, the reduction of switching frequency can make control circuit can not in time detect output voltage to cause the transient response of circuit to be affected.Therefore, in having the system of current loop control, usually adopt the method that when load reduces, reduces peak-current signal, so that the switching frequency of system can not reduce along with reducing of load too much.Wherein a kind of means commonly used are switch periods, the shutoff durations according to the power tube in the switching power circuit or open duration and adjust peak-current signal.But adopt these means to adjust peak-current signal and may produce subharmonic oscillation.

The utility model content

The purpose of this utility model is to solve the problems referred to above of prior art, the switching power circuit that provides a kind of peak-current signal to produce circuit and adopt this peak-current signal generation circuit.

According to embodiment of the present utility model, propose a kind of peak-current signal and produced circuit, described peak-current signal produces circuit and is used for switching power circuit, and described switching power circuit comprises the first power tube at least, and described peak-current signal produces circuit and comprises: the first current source; Peak value electric capacity, with the first current source coupled in parallel, the voltage signal at described peak value electric capacity two ends is peak-current signal; Low-pass filter circuit has first end, the second end, the 3rd end and control end, and described first end and the second end are coupled to respectively the two ends of peak value electric capacity, and described control end receives the pulse signal that characterizes the first power tube switch periods; The first switch has first end, the second end and control end, and described first end is coupled to the 3rd end of low-pass filter circuit, and described control end receives reset signal; And first voltage source, having first end and the second end, described first end is coupled to the second end of the first switch, and described the second end is coupled to the second end of low-pass filter circuit.

In one embodiment, described low-pass filter circuit comprises: second switch, have first end, the second end and control end, and described first end is coupled to the first end of low-pass filter circuit, described the second end is coupled to the 3rd end of low-pass filter circuit, described control end return pulse signal; And filter capacitor, having first end and the second end, described first end is coupled to the 3rd end of low-pass filter circuit, and described the second end is coupled to the second end of low-pass filter circuit.

According to embodiment of the present utility model, propose a kind of peak-current signal and produced circuit, the FREQUENCY CONTROL current source, have first end, the second end and control end, described first end is coupled to power supply, described control end receiving frequency signals, described FREQUENCY CONTROL current source provides electric current at the second end; And peak resistance, have first end and the second end, described first end is coupled to the second end of FREQUENCY CONTROL current source, described the second end ground connection, the electric current that described FREQUENCY CONTROL current source provides flows through peak resistance, and the voltage signal that produces at peak resistance is peak-current signal.

In one embodiment, the size of current and the frequency signal that provide of described FREQUENCY CONTROL current source is inversely proportional to.

According to embodiment of the present utility model, propose a kind of peak-current signal and produced circuit, electric capacity has first end and the second end, described first end ground connection, described the second end provides peak-current signal; Resistance is with Capacitance parallel connection; The 3rd switch has first end, the second end and control end, and described first end is coupled to the second end of electric capacity, and described control end receives square-wave signal; And and the 3rd current source, have first end and the second end, described first end ground connection, described the second end is coupled to the second end of the 3rd switch.

According to embodiment of the present utility model, a kind of switching power circuit has been proposed, described switching power circuit comprises that above-mentioned any peak-current signal produces circuit, also comprise: power model, the second power tube and the first power tube that comprise coupled in series, wherein the first power tube receives input voltage; Filter circuit comprises inductance and output capacitance, and wherein the two ends of output capacitance provide output voltage to load; The feedback comparator has first input end, the second input and output, and described first input end receives the feedback voltage that characterizes output voltage, and described the second input receives reference signal, described output output asserts signal; Peak comparator has first input end, the second input and output, wherein said first input end received current detection signal, and described the second input receives peak-current signal, described peak comparator output reset signal; And logical circuit, have first input end, the second input and output, described first input end is coupled to peak comparator and receives reset signal, and described the second input is coupled to the feedback comparator and receives asserts signal, and described output output switching signal is controlled the break-make of the first power tube.

In one embodiment, described switching power circuit also comprises feedback circuit, receive output voltage, produce feedback voltage, described feedback circuit comprises feedback diode, feedback capacity, the first feedback resistance and the second feedback resistance, and wherein: the first feedback resistance and the second feedback resistance are coupled in series between the first end of the negative electrode of feedback diode and inductance; The anode of feedback diode is coupled to the second end of inductance; The first end of feedback capacity is coupled to the negative electrode of feedback diode, and the second end is coupled to the first end of inductance; Feedback circuit is at the feedback voltage of the tie point output reflection output voltage of the first feedback resistance and the second feedback resistance.

Switching power circuit, peak-current signal according to the above-mentioned each side of the utility model produce circuit, can realize adjusting peak-current signal according to loading condition, so that the frequency of switching power circuit reduces along with the reduction of load, avoid simultaneously producing the purpose of subharmonic oscillation.

Description of drawings

In order better to understand the utility model, will be described in detail the utility model according to the following drawings:

Fig. 1 shows the schematic diagram of existing high-end reduction voltage circuit;

Fig. 2 shows the peak-current signal Ipeak in Fig. 1 circuit, current detection signal Ics, the waveform schematic diagram of reset signal 106 and switching signal 108;

Fig. 3 shows the switching power circuit structural representation according to the utility model one embodiment;

Fig. 4 shows the waveform schematic diagram of peak-current signal Ipeak, the peak-current signal Ipeak ' in Fig. 3 circuit, current detection signal Ics, reset signal 106 and switching signal 108 in Fig. 1 circuit;

Fig. 5 shows the circuit structure that produces circuit 505 according to the peak-current signal of the utility model one embodiment;

Fig. 6 shows the circuit structure that produces circuit 605 according to the peak-current signal of the utility model one embodiment;

Fig. 7 shows the waveform of switching signal 108 and square-wave signal TD.

Embodiment

The below will describe specific embodiment of the utility model in detail, should be noted that the embodiments described herein only is used for illustrating, and be not limited to the utility model.In the following description, in order to provide thorough understanding of the present utility model, a large amount of specific detail have been set forth.Yet, it is evident that for those of ordinary skills: needn't adopt these specific detail to carry out the utility model.In other examples, for fear of obscuring the utility model, do not specifically describe known circuit, material or method.

In whole specification, " embodiment ", " embodiment ", " example " or mentioning of " example " are meaned: special characteristic, structure or characteristic in conjunction with this embodiment or example description are comprised among at least one embodiment of the utility model.Therefore, phrase " in one embodiment ", " in an embodiment ", " example " or " example " that occurs in each place of whole specification differs to establish a capital and refers to same embodiment or example.In addition, can with any suitable combination and/or sub-portfolio with specific feature, structure or property combination in one or more embodiment or example.In addition, it should be understood by one skilled in the art that at this accompanying drawing that provides all be for illustrative purposes, and accompanying drawing is drawn in proportion not necessarily.Should be appreciated that when claiming element " to be connected to " or during " being couple to " another element it can be directly to connect or be couple to another element or can have intermediary element.On the contrary, when claiming element " to be directly connected to " or during " being directly coupled to " another element, not having intermediary element.The identical identical element of Reference numeral indication.Term used herein " and/or " comprise any and all combinations of one or more relevant projects of listing.

Fig. 1 shows the schematic diagram of existing high-end reduction voltage circuit.This circuit comprises: power model, comprise the first power tube M1 and the second power tube D1 of coupled in series, and wherein the first power tube M1 receives input voltage VIN; Filter circuit comprises inductance L 1 and output capacitance C1, and wherein the first end of inductance L 1 is coupled to the tie point of the first power tube M1 and the second power tube D1, and the two ends of output capacitance C1 provide output voltage VO UT to load; Feedback circuit, comprise feedback diode D2, feedback capacity C2 and the first feedback resistance R1 and the second feedback resistance R2, wherein the first feedback resistance R1 and the second feedback resistance R2 are coupled in series between the first end of the negative electrode of feedback diode D2 and inductance L 1, the anode of feedback diode D2 is coupled to the second end of inductance L 1, the first end of feedback capacity C2 couples the negative electrode of feedback diode D2, the second end couples the first end of inductance L 1, and feedback circuit characterizes the feedback voltage V FB of output voltage VO UT in the tie point output of resistance R 1 and R2; Control circuit 100, has first input end 100-1, the second input 100-2, earth terminal 100-3 and output 100-4, wherein said first input end 100-1 receives the current detection signal Ics that characterizes the electric current that flows through the first power tube M1, the tie point that described the second input 100-2 is coupled to feedback resistance R1 and R2 receives feedback voltage V FB, described earth terminal 100-3 is coupled to the tie point of the first power tube M1 and the second power tube D1, based on current detection signal Ics and feedback voltage V FB, control circuit 100 is controlled the break-make of the first power tube M1 at output 100-4 output switching signal, with the energy of regulation output to load.

In the high-end reduction voltage circuit shown in Figure 1, control circuit 100 comprises: peak comparator 103, have first input end, the second input and output, wherein said first input end received current detection signal Ics, described the second input receives peak-current signal Ipeak, based on current detection signal Ics and peak-current signal Ipeak, described peak comparator 103 output reset signals 106; Peak current produces circuit 105, has input and output, and the output that wherein said input is coupled to peak comparator 103 receives reset signal 106, based on reset signal 106, and described output output peak-current signal Ipeak; Feedback comparator 104, have first input end, the second input and output, the tie point that described first input end is coupled to feedback resistance R1 and R2 receives feedback voltage V FB, described the second input receives reference signal VREF, based on described feedback voltage V FB and described reference signal VREF, described feedback comparator 104 is in output output asserts signal 107; Rest-set flip-flop 101, has set end S, reset terminal R and output Q, the output that wherein said set end S is coupled to feedback comparator 104 receives asserts signal 107, the output that described reset terminal R is coupled to peak comparator 103 receives reset signal 106, based on described asserts signal 107 and reset signal 106, described rest-set flip-flop 101 is in the break-make of output Q output switching signal 108 controls the first power tube M1.

Fig. 2 shows the peak-current signal Ipeak in Fig. 1 circuit, current detection signal Ics, the waveform of reset signal 106 and switching signal 108.The course of work of control circuit 100 is described below in conjunction with Fig. 1 and Fig. 2.When the first power tube M1 opened, inductive current (namely flowing through the electric current of the first power tube M1) increased, and current detection signal Ics increases thereupon.When the value of current detection signal Ics increases to peak-current signal Ipeak, peak comparator 103 upset, thus make reset signal 106 produce the pulses rest-set flip-flop 101 that resets.Rest-set flip-flop 101 output switching signals 108 turn-off the first power tube M1.The first power tube M1 closes and has no progeny, and the second power tube D1 is open-minded, and at this moment, output voltage VO UT begins to descend, and feedback voltage V FB has reflected the size of output voltage VO UT.When feedback voltage V FB was lower than reference signal VREF, 104 upsets of feedback comparator made asserts signal 107 produce pulse, thus set rest-set flip-flop 101.Rest-set flip-flop 101 output switching signals 108 are opened the first power tube M1.

In order to reduce the switching frequency of high-end reduction voltage circuit when the underloading, improve light-load efficiency, circuit shown in Figure 1 has adopted the control method of adjusting peak-current signal according to the shutoff duration of the first power tube M1.Will be appreciated by those skilled in the art that opening duration or switching signal 108 and also can being used for adjusting peak-current signal of the first power tube M1.In Fig. 1, shown in peak current produce circuit 105 and comprise: the first current source I1, the first switch M2, peak value electric capacity C3 and the first voltage source V 1.Wherein peak value electric capacity C3 both end voltage is peak-current signal Ipeak.The shutoff duration of peak-current signal Ipeak and the first power tube M1 is inversely proportional to.The shutoff duration of the first power tube M1 is longer, i.e. load is lighter, and the value of peak-current signal Ipeak is less.

The course of work that peak current produces circuit 105 is: the first switch M2 is by reset signal 106 controls, when reset signal 106 produces pulse reset rest-set flip-flop 101, the first switch M2 is closed, peak value electric capacity C3 is connected with the first voltage source V 1, so that the value of peak-current signal Ipeak equals the value of the first voltage source V 1.Because reset signal 106 is pulse signals, and pulse duration is narrower, so behind end-of-pulsing, the first switch M2 disconnects, the first current source I1 discharges to peak value electric capacity C3, thereby peak-current signal Ipeak is descended with certain slope.The waveform of peak-current signal Ipeak as shown in Figure 2.Can see that load is lighter, the shutoff duration of the first power tube M1 is longer, and peak value electric capacity C3 is longer by the time of the first current source I1 discharge, and peak-current signal Ipeak subtracts littlely.Those of ordinary skills should be understood that the first switch M2 must by reset signal 106 controls, can not controlled by other signal that has pulse to produce yet when the first power tube M1 turn-offs.

Peak current shown in Figure 1 produces circuit 105 will make system produce subharmonic oscillation when inductive current is disturbed.Specific as follows: as to suppose to have increased Δ Ipeak1 after peak-current signal Ipeak is disturbed.The increase of peak-current signal Ipeak will cause the rise time of inductive current to increase, and namely can cause so that output to the energy increase of load the increase of output voltage VO UT.Thereby control circuit 100 will need the shutoff duration Toff that prolongs the first power tube M1 to keep Systems balanth.That is to say that the increase of peak-current signal Ipeak will prolong the shutoff duration Toff of the first power tube M1.And the peak-current signal Ipeak that peak current generation circuit 105 produces and the shutoff duration Toff of the first power tube M1 are inversely proportional to.Shutoff duration Toff after the prolongation will cause reducing of peak-current signal Ipeak.Suppose peak-current signal Ipeak and reduced Δ Ipeak2 because turn-off the reason of duration Toff prolongation.The rise time minimizing that reduces and caused inductive current of peak-current signal Ipeak namely can cause reducing of output voltage VO UT so that output to the energy minimizing of load.Thereby control circuit 100 need to shorten the shutoff duration Toff of the first power tube M1 and keep Systems balanth.That is to say that the reducing of peak-current signal Ipeak caused the shortening of the shutoff duration Toff of the first power tube M1.Because the peak-current signal Ipeak that peak current generation circuit 105 produces and the shutoff duration Toff of the first power tube M1 are inversely proportional to, the shutoff duration Toff after the shortening will cause the increase of peak-current signal Ipeak.As previously mentioned, the peak-current signal Ipeak of increase can prolong again shutoff duration Toff.So move in circles, will produce subharmonic, affect systematic function.

In above-mentioned circulation, the increment Delta Ipeak1 of the peak-current signal 1peak of current switch periods has caused the reduction Δ Ipeak2 of the peak-current signal Ipeak of next switch periods.The gain of the variable quantity of peak-current signal Ipeak is in two cycles:

$\mathrm{Gain}=\left|\frac{\mathrm{\ΔIpeak}2}{\mathrm{\ΔIpeak}1}\right|=|\frac{\mathrm{\ΔIpeak}2}{\mathrm{\ΔToff}}\×\frac{\mathrm{\ΔToff}}{\mathrm{\ΔIoeak}1}|---\left(1\right)$

In circuit shown in Figure 1, peak-current signal variation delta Ipeak1 causes the increment Delta VOUT of output voltage VO UT, and the increment Delta Toff of the shutoff duration Toff that therefore causes is:

$\mathrm{\ΔToff}=\frac{\mathrm{\ΔVOUT}}{a}=\frac{\mathrm{\ΔIpeak}1\×(\mathrm{Reqc}+\mathrm{Resr})}{a}\≈\frac{\mathrm{\ΔIpeak}1\×\mathrm{Resr}}{a}---\left(2\right)$

Wherein Reqc is the equivalent resistance of capacitor C 1, and value is left in the basket than I, and Resr is the equivalent dead resistance of capacitor C 1, and a is the discharge slope of capacitor C 2, that is:

$a=\left|\frac{\mathrm{Vc}2}{t}\right|---\left(3\right)$

Wherein Vc2 is the voltage at capacitor C 2 two ends.Then the calculation equation of the gain G ain of the variable quantity of peak-current signal Ipeak is as follows in adjacent two cycles:

$\mathrm{Gain}=\frac{b\×\mathrm{Resr}}{a}---\left(4\right)$

Wherein b is the variation delta Ipeak2 of the peak-current signal Ipeak that causes of the variation delta Toff of the shutoff duration Toff of the first power tube M1, that is:

$b=\frac{\mathrm{\ΔIpeak}2}{\mathrm{\ΔToff}}=-\frac{I1}{C3}---\left(5\right)$

In equation (4), when | Gain|＞1, will cause the generation of subharmonic.And at existing shutoff duration according to the first power tube or open duration or switch periods is adjusted in the circuit of peak-current signal, Gain is greater than 1 usually.For fear of the generation of subharmonic, should make | Gain|＜1.Can be by increasing a, the value that perhaps reduces b or Resc reaches this purpose.In Fig. 1 circuit, peak-current signal Ipeak adjusts according to the shutoff duration of the first power tube.Those of ordinary skills should be understood that peak-current signal Ipeak also can adjust according to the switch periods of opening duration or switching power circuit of the first power tube.

Fig. 3 shows the switch power supply line structure according to the utility model one embodiment.In this switching power circuit, the gain G ain of the variation delta Ipeak of the peak-current signal Ipeak of adjacent periods is less than 1, thereby can avoid producing subharmonic.Described switching power circuit comprises: power model, comprise the first power tube M1 and the second power tube D1 of coupled in series, and wherein the first power tube M1 receives input voltage VIN; Filter circuit comprises inductance L 1 and output capacitance C1, and wherein the first end of inductance L 1 is coupled to the tie point of the first power tube M1 and the second power tube D1, and the two ends of output capacitance C1 provide output voltage VO UT to load; Control circuit 300, has first input end 300-1, the second input 300-2, earth terminal 300-3, with output 300-4, wherein said first input end 300-1 receives the current detection signal Ics that characterizes the electric current that flows through the first power tube M1, described the second input 300-2 receives the feedback voltage V FB that characterizes output voltage VO UT, described earth terminal 300-3 is coupled to the tie point of the first power tube M1 and the second power tube D1, based on current detection signal Ics and feedback voltage V FB, control circuit 300 output switching signals are controlled the first power tube M1, with the energy of regulation output to load.

Figure 3 shows that high-end reduction voltage circuit structure.In this circuit, described feedback voltage V FB is produced by a feedback circuit, described feedback circuit comprises feedback diode D2, feedback capacity C2, the first feedback resistance R1 and the second feedback resistance R2, and wherein the first feedback resistance R1 and the second feedback resistance R2 are coupled in series between the first end of the negative electrode of feedback diode D2 and inductance L 1; The anode of feedback diode D2 is coupled to the second end of inductance L 1; The first end of feedback capacity C2 is coupled to the negative electrode of feedback diode, and the second end is coupled to the first end of inductance L 1; Feedback circuit is at the feedback voltage V FB of the tie point output reflection output voltage VO UT of the first feedback resistance R1 and the second feedback resistance R2.Those of ordinary skills should be understood that control circuit 300 can be used for the switching power circuit of other topological structure, such as BUCK circuit, BOOST circuit or BUCK-BOOST circuit etc.When control circuit 300 is used for common BUCK circuit, described earth terminal 300-3 ground connection.Described feedback circuit comprises resistor network, is coupled between output voltage VO UT and the ground, will generate feedback voltage V FB after the output voltage VO UT dividing potential drop.Therefore, the structure of feedback circuit is not limited to structure shown in Fig. 3 circuit.

In Fig. 3, control circuit 300 comprises: peak comparator 103, have first input end, the second input and output, wherein said first input end received current detection signal Ics, described the second input receives peak-current signal Ipeak ', based on current detection signal Ics and peak-current signal Ipeak ', described peak comparator 103 output reset signals 106; Peak current produces circuit 305, has input, earth terminal and output, wherein said input receives the pulse signal that characterizes the first power tube switch periods, described earth terminal is coupled to the tie point of the first power tube M1 and the second power tube D1, based on pulse signal, described output output peak-current signal Ipeak '; Feedback comparator 104, have first input end, the second input and output, described first input end receives feedback voltage V FB, described the second input receives reference signal VREF, based on described feedback voltage V FB and described reference signal VREF, described feedback comparator 104 is in output output asserts signal 107; Logical circuit 101, have first input end, the second input and output, the output that wherein said first input end is coupled to feedback comparator 104 receives asserts signal 107, the output that described the second input is coupled to peak comparator 103 receives reset signal 106, based on described asserts signal 107 and reset signal 106, described logical circuit 101 is in the break-make of output output switching signal 108 controls the first power tube M1.

In one embodiment, described pulse signal comprises reset signal 106.

In one embodiment, described logical circuit 101 comprises rest-set flip-flop.Described rest-set flip-flop has set end S, reset terminal R and output Q, the output that described set end S is coupled to feedback comparator 104 receives asserts signal 107, and the output that described reset terminal is coupled to peak comparator 103 receives reset signal 106, and described output Q provides switching signal 108.

In the embodiment shown in fig. 3, described the second power tube D1 is realized by diode.Those of ordinary skills should be understood that described the first power tube M1 and the second power tube D1 can comprise MOSFET (metal oxide semiconductor field effect tube), the semiconductor device such as triode.

Switching power circuit shown in Figure 3 has adopted the control method of adjusting peak-current signal according to the shutoff duration of the first power tube M1.In Fig. 3, shown in peak-current signal produce circuit 305 and comprise: the second current source I2; Peak value electric capacity C3, with the second current source I2 coupled in parallel, the voltage signal at described peak value electric capacity C3 two ends is peak-current signal Ipeak '; Low-pass filter circuit 306 has first end, the second end, the 3rd end and control end, and described first end and the second end are coupled to respectively the two ends of peak value electric capacity C3, and described control end receives reset signal 106; The first switch M2 has first end, the second end and control end, and described first end is coupled to the 3rd end of low-pass filter circuit 306, and described control end receives reset signal 106; And first voltage source V 1, having first end and the second end, described first end is coupled to the second end of the first switch M2, and described the second end is coupled to the second end of low-pass filter circuit 306.Peak-current signal Ipeak ' is inversely proportional to the shutoff duration of the first power tube M1.The shutoff duration of the first power tube M1 is longer, and the value of peak-current signal Ipeak ' is less.

In one embodiment, low-pass filter circuit 306 comprises: second switch M3, have first end, the second end and control end, described first end is coupled to the first end of low-pass filter circuit 306, described the second end is coupled to the 3rd end of low-pass filter circuit 306, and described control end receives reset signal 106; And filter capacitor C4, having first end and the second end, described first end is coupled to the 3rd end of low-pass filter circuit 306, and described the second end is coupled to the second end of low-pass filter circuit 306.

In one embodiment, low-pass filter circuit 306 also comprises inverter 307, have input and output, the output that described input is coupled to peak comparator receives reset signal 106, described output is coupled to the control end of second switch M3, and the reset signal after anti-phase is offered second switch M3.

Fig. 4 shows the waveform of peak-current signal Ipeak, the peak-current signal Ipeak ' in Fig. 3 circuit, current detection signal Ics, reset signal 106 and switching signal 108 in Fig. 1 circuit.The course of work that peak current produces circuit 305 is as follows: the first switch M2 is by reset signal 106 controls, when reset signal 106 resets rest-set flip-flop 101, the first switch M2 is closed, filter capacitor C4 and the first voltage source V 1 are connected in parallel, so that the magnitude of voltage at filter capacitor C4 two ends equals the value of the first voltage source V 1.Because reset signal 106 is pulse signals, and pulse duration is narrower, so behind end-of-pulsing, the first switch M2 disconnects.Therefore the control signal of second switch M3 is anti-phase reset signal 106, and when the first switch M2 disconnects, second switch M3 closure makes electric charge on the filter capacitor C4 and the electric charge phase average on the peak value electric capacity C3.The second current source I2 discharges to peak value electric capacity C3 and filter capacitor C4 simultaneously, thereby peak-current signal Ipeak ' is descended with certain slope.The waveform of peak-current signal Ipeak ' as shown in Figure 4.Compare with the peak-current signal Ipeak shown in Fig. 2, the slope of peak-current signal Ipeak ' is less.That is to say, than the circuit of Fig. 1, in the circuit of Fig. 3, the value of b, namely the variation delta Ipeak ' of the peak-current signal Ipeak ' that causes of the variation delta Toff of the shutoff duration Toff of the first power tube M1 is much smaller.For:

$b=\frac{{\mathrm{\ΔIpeak}}^{\′}}{\mathrm{\ΔToff}}=-\frac{I2}{C3+C4}---\left(6\right)$

In equation (3), can regulate by the value of regulating the second current source I2, capacitor C 3 or capacitor C 4 the variation delta Ipeak ' of the peak-current signal Ipeak ' that the variation delta Toff of the shutoff duration Toff of the first power tube M1 causes, thereby make Gain＜1.

By above as can be known, avoid the key of system's generation subharmonic to be to make the gain of the peak-current signal variable quantity between adjacent periods less than 1.

Those of ordinary skills should be understood that the first switch M2 and second switch M3 must by reset signal 106 controls, can not controlled by other signal that has pulse to produce yet when the first power tube M1 turn-offs.Simultaneously, the utility model is applicable to produce according to the switch periods of opening duration Ton or the first power tube M1 of the first power tube M1 the circuit of peak-current signal too.

Peak current produces circuit 305 and can be understood as the frequency control voltage source, be that peak current produces circuit 305 based on the shutoff duration of the first power tube M1, open duration or switch periods etc. and follow the frequency signal of the frequency dependence of switching power circuit to produce peak-current signal.

Peak-current signal produces circuit and also can be realized by the FREQUENCY CONTROL current source circuit.Fig. 5 shows the circuit structure that produces circuit 505 according to the peak-current signal of the utility model one embodiment.Peak-current signal produces circuit 505 and comprises: FREQUENCY CONTROL current source Ifc, have first end, the second end and control end, described first end is coupled to power supply, described control end receives the frequency signal TF of the shutoff duration Toff that characterizes switching power circuit, based on described frequency signal TF, described FREQUENCY CONTROL current source Ifc provides electric current at the second end; And peak resistance R3, have first end and the second end, described first end is coupled to the second end of FREQUENCY CONTROL current source Ifc, described the second end ground connection, the electric current that described FREQUENCY CONTROL current source Ifc provides flows through peak resistance R3, and the voltage signal that produces at peak resistance R3 is peak-current signal Ipeak.Size of current and frequency signal TF that FREQUENCY CONTROL current source Ifc provides are inversely proportional to; Frequency signal TF is larger, and the electric current that FREQUENCY CONTROL current source Ifc provides is less, and then peak-current signal Ipeak is also just less, and the relation of frequency signal TF and peak-current signal Ipeak is as follows:

$\mathrm{Ipeak}=\mathrm{Ifc}\&times;R3=\frac{\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="HDA00002010689900011.png"\; state="\{\{state\}\}">K</figure-callout>}1\&times;R3}{\mathrm{TF}}---\left(7\right)$

In following formula, K1 is the coefficient of ratio of the electric current of frequency signal TF and FREQUENCY CONTROL current source Ifc.In this embodiment, can regulate peak-current signal Ipeak and the relation that represents the frequency signal TF that turn-offs duration Toff by size or the coefficient of ratio K1 of control peak resistance R3.The value that namely can regulate b by size or the coefficient of ratio K1 of control peak resistance R3, i.e. the variation delta Ipeak of the peak-current signal Ipeak that causes of the variation delta Toff of the shutoff duration Toff of the first power tube M1, thus make Gain＜1.

Fig. 6 shows the circuit structure that produces circuit 605 according to the peak-current signal of the utility model one embodiment.Described peak-current signal produces circuit 605 and comprises: capacitor C 5, have first end and the second end, and described first end ground connection, described the second end provides peak-current signal Ipeak; Resistance R 4 is connected in parallel with capacitor C 5; The 3rd switch M4 has first end, the second end and control end, and described first end is coupled to the second end of capacitor C 5, and described control end receives square-wave signal TD; And the 3rd current source I3, have first end and the second end, described first end ground connection, described the second end is coupled to the second end of the 3rd switch M4.

Fig. 7 shows the waveform of switching signal 108 and square-wave signal TD.In one embodiment, when switching signal 108 is high level, control the first power tube M1 conducting; When switching signal 108 is low level, controls the first power tube M1 and turn-off.Square-wave signal and switching signal 108 are synchronous.When the first power tube M1 conducting, square-wave signal TD redirect is high level, and keeps default duration ton.Duration ton can adjust according to the practical situations of circuit.

When peak-current signal generation circuit 605 is applied in the switching power circuit shown in Figure 3, the course of work that peak-current signal produces circuit 605 is as follows: when the first power tube M1 opens, the 3rd switch M4 is closed, and the 3rd current source I3 provides electric current to resistance R 4, gives capacitor C 5 chargings; The 3rd switching tube M4 disconnects after duration reaches default duration ton opening, and capacitor C 5 is powered to resistance R.This shows that peak-current signal Ipeak value is determined by following formula:

$\mathrm{Ipeak}=I3\&times;R4\&times;\frac{\mathrm{ton}}{T}---\left(8\right)$

Wherein T is the switch periods of switching power circuit.After the value of the value of the 3rd current source I3 and resistance R 4 was determined, peak-current signal was relevant with the switch periods T of switching power circuit.In this embodiment, can regulate by the duration ton that adjusts the 3rd current source I3, resistance R 4 or square-wave signal TD the relation between the switch periods T of peak-current signal Ipeak and circuit, thus the gain G ain of peak-current signal variation delta Ipeak between the control adjacent periods.For example can make Gain＜1 by reducing the value of the 3rd current source I3 or resistance R 4, eliminate subharmonic.

Those of ordinary skills will be appreciated that, peak-current signal produces circuit 305, peak-current signal produces circuit 505 and peak-current signal generation circuit 605 can be used for the BUCK circuit, the switching power circuit of the topological structures such as BOOST circuit or BUCK-BOOST circuit.

Although described the utility model with reference to several exemplary embodiments, should be appreciated that used term is explanation and exemplary and nonrestrictive term.Because the utility model is implementation and do not break away from spirit or the essence of utility model in a variety of forms, so be to be understood that, above-described embodiment is not limited to any aforesaid details, and should be in the spirit and scope that the claim of enclosing limits explain widely, therefore fall into whole variations in claim or its equivalent scope and remodeling and all should be the claim of enclosing and contain.

Claims (10)

1. a peak-current signal produces circuit, it is characterized in that, described peak-current signal produces circuit and is used for switching power circuit, and described switching power circuit comprises the first power tube at least, and described peak-current signal produces circuit and comprises:

The first current source;

Peak value electric capacity, with the first current source coupled in parallel, the voltage signal at described peak value electric capacity two ends is peak-current signal;

Low-pass filter circuit has first end, the second end, the 3rd end and control end, and described first end and the second end are coupled to respectively the two ends of peak value electric capacity, and described control end receives the pulse signal that characterizes the first power tube switch periods;

The first switch has first end, the second end and control end, and described first end is coupled to the 3rd end of low-pass filter circuit, and described control end receives reset signal; And

The first voltage source has first end and the second end, and described first end is coupled to the second end of the first switch, and described the second end is coupled to the second end of low-pass filter circuit.

2. peak-current signal as claimed in claim 1 produces circuit, it is characterized in that described low-pass filter circuit comprises:

Second switch has first end, the second end and control end, and described first end is coupled to the first end of low-pass filter circuit, and described the second end is coupled to the 3rd end of low-pass filter circuit, described control end return pulse signal; And

Filter capacitor has first end and the second end, and described first end is coupled to the 3rd end of low-pass filter circuit, and described the second end is coupled to the second end of low-pass filter circuit.

3. a switching power circuit comprises that each described peak-current signal produces circuit in claim 1 or 2, it is characterized in that described switching power circuit also comprises:

Power model comprises the second power tube and described first power tube of coupled in series, and wherein the first power tube receives input voltage;

Filter circuit comprises inductance and output capacitance, and wherein the two ends of output capacitance provide output voltage to load;

The feedback comparator has first input end, the second input and output, and described first input end receives the feedback voltage that characterizes output voltage, and described the second input receives reference signal, and described feedback comparator is exported asserts signal at output;

Peak comparator has first input end, the second input and output, wherein said first input end received current detection signal, and described the second input receives peak-current signal, described peak comparator output reset signal; And

Logical circuit, have first input end, the second input and output, described first input end is coupled to peak comparator and receives reset signal, described the second input is coupled to the feedback comparator and receives asserts signal, and described logical circuit is controlled the break-make of the first power tube at the output output switching signal.

4. switching power circuit as claimed in claim 3, it is characterized in that, described switching power circuit also comprises feedback circuit, receive output voltage, produce feedback voltage based on output voltage, described feedback circuit comprises feedback diode, feedback capacity, the first feedback resistance and the second feedback resistance, wherein:

The first feedback resistance and the second feedback resistance are coupled in series between the first end of the negative electrode of feedback diode and inductance;

The anode of feedback diode is coupled to the second end of inductance;

The first end of feedback capacity is coupled to the negative electrode of feedback diode, and the second end is coupled to the first end of inductance;

Feedback circuit is at the feedback voltage of the tie point output reflection output voltage of the first feedback resistance and the second feedback resistance.

5. a peak-current signal produces circuit, it is characterized in that, described peak-current signal produces circuit and is used for switching power circuit, and described peak-current signal produces circuit and comprises:

The FREQUENCY CONTROL current source has first end, the second end and control end, and described first end is coupled to power supply, described control end receiving frequency signals, and described FREQUENCY CONTROL current source provides electric current at the second end;

And peak resistance, have first end and the second end, described first end is coupled to the second end of FREQUENCY CONTROL current source, described the second end ground connection, the electric current that described FREQUENCY CONTROL current source provides flows through peak resistance, and the voltage signal that produces at peak resistance is peak-current signal.

6. peak-current signal as claimed in claim 5 produces circuit, it is characterized in that size of current and frequency signal that described FREQUENCY CONTROL current source provides are inversely proportional to.

7. a switching power circuit comprises the peak-current signal generation circuit described in claim 5 or 6, it is characterized in that described switching power circuit also comprises:

Power model comprises the first power tube and second power tube of coupled in series, and wherein the first power tube receives input voltage;

Filter circuit comprises inductance and output capacitance, and wherein the two ends of output capacitance provide output voltage to load;

The feedback comparator has first input end, the second input and output, and described first input end receives the feedback voltage that characterizes output voltage, and described the second input receives reference signal, and described feedback comparator is exported asserts signal at output;

Peak comparator has first input end, the second input and output, wherein said first input end received current detection signal, and described the second input receives peak-current signal, described peak comparator output reset signal; And

Logical circuit, have first input end, the second input and output, described first input end is coupled to peak comparator and receives reset signal, described the second input is coupled to the feedback comparator and receives asserts signal, and described logical circuit is controlled the break-make of the first power tube at the output output switching signal.

8. a peak-current signal produces circuit, it is characterized in that, described peak-current signal produces circuit and comprises:

Electric capacity has first end and the second end, described first end ground connection, and described the second end provides peak-current signal;

Resistance is with Capacitance parallel connection;

The 3rd switch has first end, the second end and control end, and described first end is coupled to the second end of electric capacity, and described control end receives square-wave signal; And

And the 3rd current source, have first end and the second end, described first end ground connection, described the second end is coupled to the second end of the 3rd switch.

9. a switching power circuit comprises the peak-current signal generation circuit described in the claim 8, it is characterized in that described switching power circuit also comprises:

Power model comprises the first power tube and second power tube of coupled in series, and wherein the first power tube receives input voltage;

Filter circuit comprises inductance and output capacitance, and wherein the two ends of output capacitance provide output voltage to load;

The feedback comparator has first input end, the second input and output, and described first input end receives the feedback voltage that characterizes output voltage, and described the second input receives reference signal, and described feedback comparator is exported asserts signal at output;

Peak comparator has first input end, the second input and output, wherein said first input end received current detection signal, and described the second input receives peak-current signal, described peak comparator output reset signal; And

Logical circuit, have first input end, the second input and output, described first input end is coupled to peak comparator and receives reset signal, described the second input is coupled to the feedback comparator and receives asserts signal, and described logical circuit is controlled the break-make of the first power tube at the output output switching signal;

Wherein, described square-wave signal is relevant with the switch periods of the first power tube.

10. switching power circuit as claimed in claim 9, it is characterized in that, described switching power circuit also comprises feedback circuit, receive output voltage, produce feedback voltage based on output voltage, described feedback circuit comprises feedback diode, feedback capacity, the first feedback resistance and the second feedback resistance, wherein:

The first feedback resistance and the second feedback resistance are coupled in series between the first end of the negative electrode of feedback diode and inductance;

The anode of feedback diode is coupled to the second end of inductance;

The first end of feedback capacity is coupled to the negative electrode of feedback diode, and the second end is coupled to the first end of inductance;

Feedback circuit is at the feedback voltage of the tie point output reflection output voltage of the first feedback resistance and the second feedback resistance.

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