CN102769386B - Switch converter and control circuit and control method thereof - Google Patents
Switch converter and control circuit and control method thereof Download PDFInfo
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- CN102769386B CN102769386B CN201210263990.9A CN201210263990A CN102769386B CN 102769386 B CN102769386 B CN 102769386B CN 201210263990 A CN201210263990 A CN 201210263990A CN 102769386 B CN102769386 B CN 102769386B
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Abstract
The invention discloses a switching converter, a control circuit and a control method thereof. The switching converter comprises a switching circuit with a main switching tube, and the control circuit comprises: the first comparison circuit receives a current detection signal representing the current flowing through the main switching tube, compares the current detection signal with a peak current signal and generates a conduction time control signal; a modulation signal generation circuit that generates a modulation signal whose slope varies with a value of the modulation signal; a second comparison circuit receiving the modulation signal and a feedback signal related to the output of the switching circuit, and generating an off-time control signal based on the modulation signal and the feedback signal; and the logic circuit is coupled to the first comparison circuit and the second comparison circuit to receive the on-time control signal and the off-time control signal and generate a control signal for controlling the on-off of the main switching tube based on the on-time control signal and the off-time control signal.
Description
Technical field
The present invention relates generally to a kind of electronic circuit, relates in particular to switch converters and control circuit thereof and control method.
Background technology
The power loss of switch converters mainly comes from conduction loss or the switching loss of switching tube.Heavily loaded in the situation that, output off current HIGH, so conduction loss is in the highest flight.Under underloading or ideal case, output current is low, and the switching loss of switching tube in the highest flight.If switch converters is still with primary frequency work when underloading, significant switching loss can reduce conversion efficiency.For this reason, can, by the mode of frequency reducing, reduce the switching loss of switch converters under light condition.
A kind of conventional solution is to adopt the turn-off time control mode that is easy to realize underloading frequency reducing.Fig. 1 is a kind of circuit diagram of switch converters 100 of existing employing turn-off time control.Switch converters 100 is operated in discontinuous current pattern, receives input voltage V
iN, for load 150 provides output voltage V
oor output current I
o.Switch converters 100 comprises switching circuit, feedback circuit 140 and control circuit.Wherein switching circuit adopts inverse-excitation converting topology, comprises input capacitor C
iN, transformer T, diode D, output capacitor C
oUTand switching tube M.Control circuit comprises capacitor C
m, current source I
m0, discharge switch pipe S, the first comparison circuit 110, the second comparison circuit 120 and trigger 130.Current source I
m0one end be coupled to supply power voltage V
cC, the other end is coupled to capacitor C
mwith one end of discharge switch pipe S, capacitor C
mother end ground connection with discharge switch pipe S.The output signal U of feedback circuit 140 receiving key circuit
o(output voltage V
o, output current I
oor both combinations), produce the feedback signal FB of reflected load state.The second comparison circuit 120 is by feedback signal FB and capacitor C
mthe voltage V at two ends
m0compare.The first comparison circuit 110 flows through representative current detection signal CS and the peak-current signal V of switching tube M electric current
peakcompare.
As shown in Figure 1, during switching tube M conducting, current detection signal CS increases gradually.When current detection signal CS reaches peak-current signal V
peaktime, the first comparison circuit 110 reset flip-flops 130, switching tube M turn-offs.As capacitor C
mthe voltage V at two ends
m0while being greater than feedback signal FB, the second comparison circuit 120 set flip-flops 130, switching tube M conducting again.The second comparison circuit 120 output pulse signal Pulse are to the control end of discharge switch pipe S simultaneously, and the default duration Tp of conducting discharge switch pipe S mono-, makes capacitor C
mthe voltage V at two ends
m0reduce to zero.After default duration Tp finishes, discharge switch pipe S disconnects, current source I
m0again be capacitor C
mcharging, capacitor C
mthe voltage V at two ends
m0linear growth.When load reduces, feedback signal FB increases, current source I
m0to capacitor C
mcharging interval elongated, the turn-off time of switching tube M is elongated, the operating frequency of switch converters 100 reduces.
In actual application, inventor finds current source I
m0choose certain problem that exists.For example, we wish current source I on the one hand
m0the magnitude of current as far as possible little, to reduce to greatest extent the operating frequency of switch converters, the switching loss while effectively suppressing underloading when the underloading.Yet on the other hand, we wish again current source I
m0the magnitude of current want enough greatly, when guaranteeing that switch converters is operated in high frequency, feedback signal FB can reach the requirement (enough large, to be conventionally greater than 50mV) of signal resolution, to avoid being subject to the interference of system noise.
Summary of the invention
For one or more problems of the prior art, the object of this invention is to provide switch converters and control circuit thereof and control method, it can guarantee the requirement of signal resolution, can effectively suppress again the switching loss of switch converters.
In one aspect of the invention, a kind of control circuit for switch converters is proposed, this switch converters comprises the switching circuit with main switch, this control circuit comprises: the first comparison circuit, receive representative and flow through the current detection signal of main switch electric current, current detection signal is compared with peak-current signal, produce ON time control signal; Modulated signal producing circuit, produces modulation signal, and the slope of this modulation signal becomes along with the value of modulation signal; The second comparison circuit, receives modulation signal and exports relevant feedback signal to switching circuit, based on modulation signal and feedback signal, produces turn-off time control signal; And logical circuit, be coupled to the first and second comparison circuits to receive ON time control signal and turn-off time control signal, based on ON time control signal and turn-off time control signal, produce the control signal of controlling described main switch conducting and shutoff.
In another aspect of the present invention, a kind of switch converters is proposed, comprise foregoing control circuit.
Of the present invention aspect another, a kind of control method for switch converters is also proposed, this switch converters comprises the switching circuit with main switch, this control method comprises: the current detection signal that representative is flow through to main switch electric current is compared with peak-current signal, produces ON time control signal; Produce modulation signal, the slope of this modulation signal becomes along with the value of modulation signal; Modulation signal and one is exported to relevant feedback signal to switching circuit and compare, produce turn-off time control signal; Based on ON time control signal and turn-off time control signal, produce the control signal of controlling described main switch conducting and shutoff.
Accompanying drawing explanation
For a better understanding of the present invention, will describe the present invention according to the following drawings:
Fig. 1 is a kind of circuit diagram of switch converters 100 of existing employing turn-off time control;
Fig. 2 is the block diagram of switch converters 200 according to an embodiment of the invention;
Fig. 3 is the circuit diagram of switch converters 300 according to an embodiment of the invention;
Fig. 4 is the oscillogram of switch converters in Fig. 3 according to an embodiment of the invention;
Fig. 5 is modulation signal V according to an embodiment of the invention
mwith controlled current source I
mbetween be related to schematic diagram;
Fig. 6 is the circuit diagram of modulated signal producing circuit 302 in Fig. 3 according to an embodiment of the invention;
Fig. 7 is the oscillogram of the modulated signal producing circuit shown in Fig. 6 302 according to an embodiment of the invention;
Fig. 8 is the flow chart of switch converters control method 800 according to an embodiment of the invention.
Embodiment
To describe specific embodiments of the invention in detail below, it should be noted that the embodiments described herein, only for illustrating, is not limited to the present invention.In the following description, in order to provide thorough understanding of the present invention, a large amount of specific detail have been set forth.Yet, for those of ordinary skills, it is evident that: needn't adopt these specific detail to carry out the present invention.In other examples, for fear of obscuring the present invention, 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 at least one embodiment of the present invention.Therefore phrase " in one embodiment ", " in an embodiment ", " example " or " example ", occurring 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 by 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 the diagram providing at this is all for illustrative purposes, and diagram is not necessarily drawn in proportion.Should be appreciated that it can be directly connected or coupled to another element or can have intermediary element when claiming " element " " to be connected to " or " coupling " arrives another element.On the contrary, when claiming element " to be directly connected to " or during " being directly coupled to " another element, not having intermediary element.Identical Reference numeral is indicated identical element.Term "and/or" used herein comprises any and all combinations of one or more relevant projects of listing.
Fig. 2 is the block diagram of switch converters 200 according to an embodiment of the invention, comprises control circuit, switching circuit 205 and feedback circuit 206.Switching circuit 205 comprises main switch, and the conducting by main switch is converted to output signal OUT by input signal IN with turn-offing.Input signal IN and output signal OUT can be voltage, electric current or power signal.Switching circuit 205 can adopt any DC/DC conversion topological structure, for example synchronous or asynchronously boost, buck converter, and normal shock, anti exciting converter etc.Feedback circuit 206 is coupled to switching circuit 205, and the output signal OUT of sampling switch circuit produces the feedback signal FB relevant to output signal OUT.In one embodiment, feedback circuit 206 can comprise resitstance voltage divider and error amplifier etc.
Control circuit comprises the first comparison circuit 201, modulated signal producing circuit 202, the second comparison circuit 203 and logical circuit 204.The first comparison circuit 201 is coupled to switching circuit 205, receive representative and flow through the current detection signal CS of main switch electric current, and current detection signal CS is compared with peak-current signal, produce ON time control signal Ton, with the ON time of main switch in control switch circuit 205.
Modulated signal producing circuit 202 is for providing modulation signal V
m, this modulation signal V
mslope along with modulation signal V
mvalue and become.In one embodiment, modulation signal V
mvalue larger, modulation signal V
mthe rate of rise less, vice versa.The second comparison circuit 203 is coupled to modulated signal producing circuit 202 and feedback circuit 206, by modulation signal V
mfB compares with feedback signal, produces turn-off time control signal Toff, with the turn-off time of control switch circuit 205 main switches.Logical circuit 204 is coupled to the first comparison circuit 201 and the second comparison circuit 202, based on ON time control signal Ton and turn-off time control signal Toff, produces control signal Gate, to control conducting and the shutoff of main switch.
In one embodiment, modulated signal producing circuit 202 comprises capacitor C
m, discharge switch pipe K
m, controlled current source I
mwith the pulse-generating circuit 212 for generation of discharge pulse signal Pulse.Capacitor CM has first end and the second end, and wherein first end is used to provide modulation signal V
m, the second end ground connection.Discharge switch pipe K
mhave first end, the second end and control end, wherein first end is coupled to capacitor C
mfirst end, the second end ground connection, control end is coupled to pulse-generating circuit 212 to accept discharge pulse signal Pulse.Controlled current source I
mhave control end, feeder ear and output, wherein control end is coupled to capacitor C
mfirst end to receive modulation signal V
m, feeder ear is coupled to supply power voltage Vcc, and output is coupled to capacitor C
mfirst end, be capacitor C
mcharging current is provided.
Controlled current source I
mcontrol end be coupled to modulation signal V
m, controlled current source I
mthe magnitude of current along with modulation signal V
mvalue and change so capacitor C
mthe rate of rise of both end voltage, i.e. modulation signal V
mslope also with modulation signal V
mvalue and change.In one embodiment, as modulation signal V
mvalue while increasing, controlled current source I
mthe magnitude of current reduce, modulation signal V
mthe rate of rise reduce; As modulation signal V
mvalue while reducing, controlled current source I
mthe magnitude of current increase, modulation signal V
mthe rate of rise increase.
Fig. 3 is the circuit diagram of switch converters 300 according to an embodiment of the invention.Switch converters 300 comprises control circuit, switching circuit and feedback circuit.Switching circuit adopts inverse-excitation converting topology, receives input voltage V
iN, for load provides output voltage V
oUT.Switching circuit comprises transformer T, main switch M, secondary diode D and output capacitor C
oUT, it connects as shown in the figure.Transformer T comprises former limit winding Np, secondary winding Ns and auxiliary winding Na.In the embodiment shown in fig. 3, main switch M is MOSFET.In other embodiments, main switch M can adopt the transistor that other types are suitable.
As shown in Figure 3, feedback circuit comprises resistor voltage divider circuit 307, sampling hold circuit 308 and error amplifier EA.Resistor voltage divider circuit 307 comprises resistor R1 and R2, is coupled to the two ends of the auxiliary winding Na of transformer T, and the voltage at auxiliary winding Na two ends is carried out to dividing potential drop, obtains a voltage sampling signal Vs
0.Sampling hold circuit 308 is coupled to the output of resistor voltage divider circuit 308 with receiver voltage sampled signal Vs
0, and represent switching circuit output voltage V in its output generation one
oUTvoltage detection signal Vs.Error amplifier EA has the in-phase input end of receiver voltage detection signal Vs and receives the inverting input of reference voltage Vref, and error amplifier EA produces and exports relevant feedback signal FB to switching circuit at its output.In other embodiments, feedback circuit is coupled to the output of switching circuit, the output voltage V of sampling switch circuit
oUT, and produce one with switching circuit output voltage V
oUTrelevant feedback signal FB.In an embodiment, feedback circuit comprises photoelectric coupled device and Three-end voltage stabilizer therein.
Control circuit comprises the first comparison circuit 301, modulated signal producing circuit 302, the second comparison circuits 303 and logical circuit 304.The first comparison circuit 301 comprises comparator C OM1.Comparator C OM1 has in-phase input end, inverting input and output, in-phase input end received current detection signal CS wherein, and inverting input is coupled to peak-current signal V
peak, output provides ON time control signal Ton, with the ON time of main switch M in control switch circuit.Any one method in many known sampling switch tube current methods, for example current transformer or sampling resistor, all can be used for detecting the electric current that flows through main switch M.
Modulated signal producing circuit 302 comprises capacitor C
m, discharge switch pipe K
m, controlled current source I
mwith pulse-generating circuit 312.Pulse-generating circuit 312 is for generation of discharge pulse signal Pulse, with controlled discharge switching tube K
mconducting and shutoff.Within each work period of discharge pulse signal Pulse, when discharge pulse signal Pulse is low level, discharge switch pipe K
min off state, controlled current source I
mto capacitor C
mcharging, capacitor C
mthe voltage at two ends (is modulation signal V
m) non-linear growth of starting from scratch; When discharge pulse signal Pulse is high level, discharge switch pipe K
mconducting, capacitor C
mthe voltage at two ends is down to zero.
The second comparison circuit 303 comprises comparator C OM2.Comparator C OM2 has in-phase input end, inverting input and output, and wherein in-phase input end is coupled to modulated signal producing circuit 302 to receive modulation signal V
m, inverting input is coupled to feedback circuit with receiving feedback signals FB, and output provides turn-off time control signal Toff, with the turn-off time of main switch M in control switch circuit.
Logical circuit 304 comprises trigger FF, and wherein the reset terminal R of trigger FF is coupled to the output of the first comparison circuit 301, receives ON time control signal Ton.The set end S of trigger FF is coupled to the output of the second comparison circuit 303, receives turn-off time control signal Toff.Based on ON time control signal Ton and turn-off time control signal Toff, trigger FF produces control signal Gate at its output Q.Control signal Gate is used to control conducting and the disconnection of main switch M.It will be appreciated by those of ordinary skill in the art that control signal Gate can control the break-make of main switch M conventionally after overdrive circuit is strengthened driving force again.
In one embodiment, control circuit is integrated circuit or discrete electronic devices and components.In another embodiment, the main switch M in control circuit and switching circuit 306 and the error amplifier EA in feedback circuit are integrated in same control IC.
Fig. 4 is the oscillogram of switch converters 300 in Fig. 3 according to an embodiment of the invention.As shown in Figure 4, within each work period, when main switch M conducting, the electric current I p that flows through main switch M starts to increase, and current detection signal CS also increases.When current detection signal CS reaches peak-current signal V
peaktime, the first comparison circuit 301 produces the ON time control signal Ton of high level, and the low level control signal Gate of triggering for generating is to turn-off main switch M.As modulation signal V
mvalue be greater than feedback signal FB, the second comparison circuit 303 produces the turn-off time control signal Toff of high level, the control signal Gate of triggering for generating high level is by main switch M again conducting.Then switching circuit enters next switch periods, and operation as mentioned above.
As previously mentioned, modulation signal V
mslope along with modulation signal V
mvalue and become.As shown in Figure 4, when load is heavier, feedback signal FB is little, modulation signal V
mvalue also less, modulation signal V
mthe rate of rise corresponding larger, modulation signal V
mcan rapidly increase to feedback signal FB within a short period of time, meet the requirement of switch converters to signal resolution.Along with load lightens, feedback signal FB increases, modulation signal V
mvalue increase thereupon, modulation signal V
mthe rate of rise diminish, slowed down modulation signal V
mreach the speed of feedback signal FB, so controlled current source I
mfor capacitor C
mthe time of charging becomes longer, and switching frequency is greatly reduced, thereby has met the requirement of switch converters to efficiency.
Fig. 5 is modulation signal V according to an embodiment of the invention
mwith controlled current source I
mbe related to schematic diagram.According to modulation signal V
mvalue adjust controlled current source I
mthe magnitude of current, and according to controlled current source I
mthe magnitude of current control modulation signal V
mslope.Controlled current source I
mthe magnitude of current larger, modulation signal V
mslope less, vice versa.Controlled current source I
mthe magnitude of current and modulation signal V
mpass be: a). as modulation signal V
mbe less than or equal to first threshold V
m1time, controlled current source I
mthe magnitude of current be fixed on maximum I
mAX; B). as modulation signal V
min first threshold V
m1with Second Threshold V
m2between time, controlled current source I
mthe magnitude of current with modulating function f (V
m) change; C). as modulation signal V
mbe greater than Second Threshold V
m2, controlled current source I
mthe magnitude of current be fixed on minimum value I
mIN.As shown in Figure 4, controlled current source I
mthe magnitude of current and modulation signal V
mfunctional relation be:
Modulating function f (V wherein
m) should meet following three conditions:
a).f(V
M1)＝I
MAX；
b).f(V
M2)＝I
MIN；
C) .f (V
m) along with V
mincrease and reduce.
In one embodiment, modulating function f (V
m) can be:
Although provided specific modulated signal producing circuit 302 in Fig. 3, in other embodiments, can also adopt other circuit structures to produce the modulation signal V of non-linear growth
m, for example numeral mode.
Fig. 6 is the circuit diagram of modulated signal producing circuit 302 in Fig. 3 according to an embodiment of the invention.Modulated signal producing circuit 302 comprises capacitor C
m, discharge switch pipe K
m, controlled current source I
mand pulse signal generating circuit 312.In one embodiment, modulated signal producing circuit 302 also comprises double limiting circuit 313 and buffer circuit 314.
Buffer circuit 314 is for to modulation signal V
misolate and drive.In one embodiment, buffer circuit 314 comprises buffer.In a further embodiment, buffer comprises operational amplifier, and the in-phase input end of this operational amplifier is as the input of buffer, and the inverting input of this operational amplifier is together with output electric coupling, as the output of buffer.In another embodiment, buffer circuit 314 comprises buffer and the resistor of connecting with buffer.
As shown in Figure 6, double limiting circuit 313 and buffer circuit 314 have respectively input and output, and wherein the input of buffer circuit 314 is coupled to capacitor C
mfirst end to receive modulation signal V
m, the output of buffer circuit 314 is coupled to the input of double limiting circuit 313, and the output of double limiting circuit 313 is coupled to controlled current source I
mcontrol end so that current controling signal to be provided.In one embodiment, as modulation signal V
mvalue while being less than first threshold, double limiting circuit 313 is fixed on minimum value by current controling signal; As modulation signal V
mvalue while being greater than Second Threshold, double limiting circuit 313 is fixed on maximum by current controling signal.
In embodiment as shown in Figure 6, controlled current source has the first control end V
+with the second control end V
-, the first control end V
+pass through voltage source V
1be coupled to ground.Double limiting circuit 313 comprises resistor R0, diode D2 and D3 and direct voltage source V
2and V
3.One end of resistor R0 is coupled to the output of buffer circuit 313, and the other end is coupled to controlled current source I
mthe second control end V
-, the negative electrode of diode D2 and the anode of diode D3.The anode of diode D2 is through direct voltage source V
2be coupled to ground, the negative electrode of diode D3 is through direct voltage source V
3be coupled to ground.
Wherein, resistor R0, diode D2 and direct voltage source V
2form lower limit amplitude limiter, work as V
m< V
2, diode D2 conducting, controlled current source I
mthe second control end V
-voltage be V
2; Resistor R0, diode D3 and direct voltage source V
3form upper limit amplitude limiter, work as V
m> V
3, diode D3 conducting, controlled current source I
mthe second control end V
-voltage be V
3.Upper and lower limit amplitude limiter is combined, formed double limiting circuit 313 as shown in Figure 6.In addition, in the embodiment shown in fig. 6, due to direct voltage source V
1be coupled in controlled current source I
mthe first control end V
+and between ground, controlled current source I
mthe minimum value of current controling signal is V
1-V
3, maximum is V
1-V
2.
Discharge pulse produces circuit 312 for generation of discharge pulse signal Pulse.In one embodiment, discharge pulse signal Pulse with the ON time tonp of main switch M, ON time tons and the interrupting time tdcm of secondary diode D are relevant.When main switch M conducting or secondary diode D conducting, discharge pulse signal Pulse keeps high level, discharge switch pipe K
mconducting; When main switch M and secondary diode D are all during not conducting, discharge pulse signal Pulse keeps low level, discharge switch pipe K
mturn-off.
In the embodiment shown in fig. 6, discharge pulse generation circuit 312 comprises testing circuit 310 and or door 325.Testing circuit 310 is for detection of secondary ON time tons, to produce the pulse signal Tons of reflection secondary ON time.Testing circuit 310 comprises trigger 320, the first not gate 321, the second not gate 322, the first and second rising edge testing circuits 323 and 324 and comparator C OM3.Trigger 320 has set end S, reset terminal R and output Q.The first not gate 321 has input and output, and its input is coupled to control signal Gate, and output is coupled to the input of the first rising edge testing circuit 323.The set end S of the output contact hair device 320 of the first rising edge testing circuit 323.Comparator C OM3 has in-phase input end, inverting input and output, and wherein in-phase input end is coupled to reference signal V
rEFX(for example 100mV), inverting input is coupled to the voltage sampling signal V shown in Fig. 3
s0, output is coupled to the input of the second not gate 322.The output of the second not gate 322 is coupled to the input of the second rising edge testing circuit 324.The output of the second rising edge testing circuit 325 is coupled to the reset terminal of trigger 320.Trigger 320, at its output, produces the pulse signal Tons of reflection secondary ON time at the output of testing circuit 310.
Or door 325 has first input end, the second input and output, wherein first input end is coupled to the output (being the output of trigger 320) of testing circuit 310, the second input is coupled to control signal Gate, and output is coupled to discharge switch pipe K
mcontrol end so that discharge pulse signal Pulse to be provided.
In one embodiment, for example, when switching circuit is boosting inverter topology, discharge pulse signal Pulse is that the zero-time is relevant with inductive current rise time, inductive current fall time and inductive current.Within the time period that inductive current rises or inductive current declines, discharge pulse signal Pulse keeps high level, discharge switch pipe K
mconducting; In inductive current is time period of zero, discharge pulse signal Pulse keeps low level, discharge switch pipe K
mturn-off.
Fig. 7 is the oscillogram of the modulated signal producing circuit shown in Fig. 6 302 according to an embodiment of the invention.When the trailing edge arriving of control signal Gate, when secondary diode D starts conducting, pulse signal Tons saltus step is high level; As voltage sampling signal V
s0trailing edge arrive, i.e. when secondary diode D conducting finishes, pulse signal Tons saltus step is low level.At pulse signal Tons, be between high period and control signal Gate is between high period, discharge pulse signal Pulse keeps high level, otherwise discharge pulse signal Pulse is low level.
In one embodiment, discharge pulse produces circuit 312 can comprise other circuit structure that can produce discharge pulse signal Pulse as shown in Figure 7, for example, discharge pulse generation circuit 312 can comprise the timer Count1 of timing main switch M ON time tonp, the timer Count2 of timing secondary diode ON time tons and the timer Count3 of timing interrupting time tdcm.When timer Count1 or Count2 timing, discharge pulse produces circuit 312 output high level; When timer Count3 clocks, discharge pulse produces circuit 312 output low levels.
In another embodiment, pulse-generating circuit 312 can comprise monostable flipflop, and monostable flipflop is coupled in output and the discharge switch pipe K of the second comparison circuit 303 shown in Fig. 3
mcontrol end between.When turn-off time control signal Toff is while being high, monostable flipflop output high level pulse conducting discharge switch pipe K
mone default duration Tp, makes capacitor C
mthe voltage at two ends reduces to zero.After default duration Tp finishes, discharge switch pipe K
mturn-off current source I
magain be capacitor C
mcharging.
Fig. 8 is that this switch converters comprises the switching circuit with main switch according to an embodiment of the invention for the flow chart of the control method 800 of switch converters, and this control method 800 comprises step 801～804.
Step 801: the current detection signal that representative is flow through to main switch electric current is compared with peak-current signal, produces ON time control signal, to control the ON time of main switch.
Step 802: produce modulation signal, the slope of this modulation signal becomes with the value of modulation signal.In one embodiment, the slope of modulation signal reduces with the increase of modulation signal value.
Step 803: modulation signal and is exported to relevant feedback signal to switching circuit and compare, produce turn-off time control signal, to control the turn-off time of main switch.
Step 804: based on ON time control signal and turn-off time control signal, produce the control signal of controlling main switch conducting and shutoff.
In one embodiment, when the value of modulation signal is less than first threshold, the slope of modulation signal is fixed on ceiling value; When the value of modulation signal is between first threshold and Second Threshold, the slope of modulation signal reduces with the increase of modulation signal value; When the value of modulation signal is greater than Second Threshold, the slope of modulation signal is fixed on minimum limit value.
Only the present invention will be described in an exemplary fashion for some above-mentioned specific embodiments, and these embodiment are not completely detailed, the scope being not intended to limit the present invention.It is all possible for disclosed embodiment, changing and revise, the selectivity embodiment that other are feasible and can being understood by those skilled in the art the equivalent variations of element in embodiment.Other variations of disclosed embodiment of this invention and modification do not exceed spirit of the present invention and protection range.
Claims (10)
1. for a control circuit for switch converters, this switch converters comprises the switching circuit with main switch, and this control circuit comprises:
The first comparison circuit, receives the current detection signal that main switch electric current is flow through in representative, and current detection signal is compared with peak-current signal, produces ON time control signal;
Modulated signal producing circuit, produces modulation signal, and the slope of this modulation signal becomes along with the value of modulation signal;
The second comparison circuit, receives modulation signal and exports relevant feedback signal to switching circuit, based on modulation signal and feedback signal, produces turn-off time control signal; And
Logical circuit, is coupled to the first and second comparison circuits to receive ON time control signal and turn-off time control signal, based on ON time control signal and turn-off time control signal, produces the control signal of controlling described main switch conducting and shutoff.
2. control circuit as claimed in claim 1, wherein modulated signal producing circuit comprises:
Pulse-generating circuit, for generation of discharge pulse signal;
Capacitor, has first end and the second end, and wherein first end is used to provide modulation signal, the second end ground connection;
Discharge switch pipe, has first end, the second end and control end, and wherein first end is coupled to the first end of capacitor, the second end ground connection, and control end is coupled to pulse-generating circuit to receive discharge pulse signal; And
Controlled current source, has control end and feeder ear and output, and wherein feeder ear is coupled to supply power voltage, and control end and output are all coupled to the first end of capacitor, and wherein the electric current of controlled current source reduces with the increase of modulation signal value.
3. control circuit as claimed in claim 2, wherein modulated signal producing circuit further comprises double limiting circuit, this double limiting circuit has input and output, the first end that wherein input is coupled to capacitor is to receive modulation signal, output is coupled to the control end of controlled current source so that current controling signal to be provided, wherein, when the value of modulation signal is less than first threshold, double limiting circuit is fixed on minimum value by current controling signal; When the value of modulation signal is greater than Second Threshold, double limiting circuit is fixed on maximum by current controling signal.
4. control circuit as claimed in claim 3, wherein controlled current source has the first control end and the second control end, and the first control end is coupled to ground by the first voltage source, and double limiting circuit comprises:
Resistor, has first end and the second end, and wherein first end is coupled to the first end of capacitor, and the second end is coupled to the second control end of controlled current source;
The first diode, has anode and negative electrode, and its Anodic is coupled to the second end of resistor;
The second DC source, is coupled between the negative electrode and ground of the first diode;
The second diode, has anode and negative electrode, and wherein negative electrode is coupled to the second end of resistor; And
The 3rd DC source, is coupled between the anode and ground of the second diode.
5. control circuit as claimed in claim 3, wherein modulated signal producing circuit further comprises the buffer circuit being coupled between capacitor first end and double limiting circuit input end.
6. control circuit as claimed in claim 1, wherein:
When the value of modulation signal is less than first threshold, the slope of modulation signal is fixed on ceiling value;
When the value of modulation signal is between first threshold and Second Threshold, the slope of modulation signal reduces with the increase of modulation signal value;
When the value of modulation signal is greater than Second Threshold, the slope of modulation signal is fixed on minimum limit value.
7. a switch converters, comprises the control circuit as described in any one in claim 1 to 6.
8. for a control method for switch converters, this switch converters comprises the switching circuit with main switch, and this control method comprises:
The current detection signal that representative is flow through to main switch electric current is compared with peak-current signal, produces ON time control signal;
Produce modulation signal, the slope of this modulation signal becomes along with the value of modulation signal;
Modulation signal and one is exported to relevant feedback signal to switching circuit and compare, produce turn-off time control signal;
Based on ON time control signal and turn-off time control signal, produce the control signal of controlling described main switch conducting and shutoff.
9. control method as claimed in claim 8, wherein the slope of modulation signal reduces with the increase of modulation signal value.
10. control method as claimed in claim 9, wherein:
When the value of modulation signal is less than first threshold, the slope of modulation signal is fixed on ceiling value;
When the value of modulation signal is between first threshold and Second Threshold, the slope of modulation signal reduces with the increase of modulation signal value;
When the value of modulation signal is greater than Second Threshold, the slope of modulation signal is fixed on minimum limit value.
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| CN107834516B (en) * | 2015-10-30 | 2019-04-02 | 杰华特微电子（杭州）有限公司 | A kind of overvoltage crowbar for Switching Power Supply |
| CN108923650B (en) * | 2018-06-27 | 2021-05-18 | 成都芯源系统有限公司 | Multiphase converter and control circuit and control method thereof |
| CN111239465B (en) * | 2020-01-16 | 2023-05-23 | 昂宝电子（上海）有限公司 | Line voltage detection circuit, system and method |
| CN111130319A (en) * | 2020-02-13 | 2020-05-08 | 杭州必易微电子有限公司 | Voltage conversion circuit, primary side control circuit and primary side switch control method |
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| CN102005911A (en) * | 2009-09-01 | 2011-04-06 | 安凯(广州)微电子技术有限公司 | Piecewise linear slope compensation method and circuit |
| CN102594097A (en) * | 2012-03-13 | 2012-07-18 | 成都芯源系统有限公司 | Switching power supply and control circuit and control method thereof |
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| DE10225406B4 (en) * | 2002-06-07 | 2005-07-14 | Infineon Technologies Ag | Method for driving a switch in a switching converter and drive circuit for controlling a switch |
| KR101471133B1 (en) * | 2008-01-31 | 2014-12-09 | 페어차일드코리아반도체 주식회사 | resonant converter |
| JP5642349B2 (en) * | 2009-02-05 | 2014-12-17 | フリースケール セミコンダクター インコーポレイテッド | Pulse width modulation circuit, pulse width modulation method and regulator |
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| CN102005911A (en) * | 2009-09-01 | 2011-04-06 | 安凯(广州)微电子技术有限公司 | Piecewise linear slope compensation method and circuit |
| CN102594097A (en) * | 2012-03-13 | 2012-07-18 | 成都芯源系统有限公司 | Switching power supply and control circuit and control method thereof |
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