CN104022627A - Control circuit and power converter - Google Patents
Control circuit and power converter Download PDFInfo
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- CN104022627A CN104022627A CN201410287558.2A CN201410287558A CN104022627A CN 104022627 A CN104022627 A CN 104022627A CN 201410287558 A CN201410287558 A CN 201410287558A CN 104022627 A CN104022627 A CN 104022627A
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Abstract
The invention discloses a control circuit, which comprises a current sampling circuit, a voltage compensation circuit, a minimum conduction time limiting circuit and a comparison circuit. During the conduction period of a power switch pipe, when one of a current feedback signal and a slope voltage signal achieves a voltage compensation signal, the comparison circuit outputs an efficient comparison control signal to turn off the power switch pipe so that the stability of the output voltage of the power level circuit can be maintained. Therefore, when a power converter is in light load, and the control circuit is capable of controlling the generation of efficient comparison control signals to turn off the power switch pipe before blanking time, the ripple wave of output voltage is reduced. The invention further provides a power convert comprising the control circuit.
Description
Technical field
The power conversion technical field that the present invention relates to electric equipment, particularly relates to a kind of control circuit and supply convertor.
Background technology
Power conversion technology is a kind of energy (power) treatment technology, is made up of power stage (Power Stage) circuit of supply convertor power switch pipe and inductance (as inductance, electric capacity etc.).Power conversion technology can be divided into four kinds:
(1) AC-DC conversion, the direct voltage that is a certain numerical value by AC voltage conversion, is called direct transform, conventionally referred to as conversion (Conversion).Conventional rectification (Rectification) is the most basic, the simplest AC-DC conversion;
(2) DC-DC conversion, the direct voltage that is another numerical value by the DC voltage conversion of a certain numerical value;
(3) DC-AC conversion, is certain waveform by DC voltage conversion, and exchanging a little of a certain frequency and a certain voltage, is called inverse transformation, conventionally referred to as inversion (Inversion);
(4) AC-AC conversion, by a kind of waveform, frequency, the alternating current of voltage is transformed to another kind of waveform, frequency, the alternating current of voltage, realizes friendship-alternation and presses, frequency conversion (Cyclo-conversion).
But, no matter which kind of power conversion technology, in the time that load is underloading, the output voltage of power stage circuit there will be larger ripple.The supply convertor of the DC-DC converter technique of prior art is at full load, and supply convertor often works in continuous current mode (Continuous Conduction Mode is called for short CCM), and the ripple of output voltage is less; And in the time that the output loading of supply convertor changes to underloading from being fully loaded with, supply convertor often works in discontinuous current mode (Discontinuous Conduction Mode is called for short DCM), output voltage has larger ripple.Larger ripple can cause the Efficiency Decreasing of supply convertor, and can cause electromagnetic interference (Electron-Magnetic Interference is called for short EMI) characteristic to weaken.In order to reduce ripple, conventional control method is to set minimum ON time (minimum on time) at present, carrys out the ON time of power-limiting level circuit in the time of underloading, thus less output ripple.
As shown in Figure 1, provided the supply convertor 10 of the DC-DC converter technique as an example of booster circuit example, supply convertor 10 comprises power stage circuit 100 and control circuit 120.Wherein, power stage circuit 100 comprises: voltage input end 101, inductance L, voltage output end 102 and power switch pipe Q1, voltage input end 101 is for inputting an input voltage V
in, one end of described inductance L connects described voltage input end 101, and voltage output end 102 is for inputting an output voltage V
o, described voltage output end 102 connects the other end of described inductance L, and the drain electrode of described power switch pipe Q1 connects described inductance L, the source ground of described power switch pipe Q1, the grid of described power switch pipe Q1 receives a control signal BG.In addition, supply convertor 10 can also comprise input capacitance C
in, diode D, output capacitance C
out, load resistance R
ldeng element.
Control circuit 120 comprises blanking time circuit 121, voltage compensating circuit 122, comparison circuit 123 and logic control circuit 124.Blanking time circuit 121 is controlled current feedback signal I
lblanking time, described current feedback signal I
lthe flow through current i of described inductance L of sign
l, within the blanking time, blanking time circuit 121 is controlled described current feedback signal I
lfor disarmed state.
Voltage compensating circuit 122 is according to described output voltage V
ofeedback voltage V
fand reference voltage V
ref, formation voltage compensating signal V
comp, described voltage compensation signal V
compcharacterize described output voltage V
ofeedback voltage V
fwith reference voltage V
refdifference.
Comparison circuit 123, receives described voltage compensation signal V
compwith current feedback signal I
l, produce comparison control signal V
a.Logic control circuit 124, according to described comparison control signal V
aand clock signal clk, output is for controlling the control signal BG of described power switch pipe Q1.
100 li of described power stage circuits, in low duty cycle operation process, the conducting of power switch pipe Q1 is always by the internal clocking control of power stage circuit 100, irrelevant with control circuit 120, therefore there is minimum ON time, its by power stage circuit 100 performance constraints at higher switching frequency.And, due to the restriction of settling time, can not current sensor in the time that pulse is wide not.
But, in the prior art, minimum ON time be often subject to blanking time (blanking time) restriction of peak value sampling and be difficult to accomplish less, thereby cannot export less ripple.
Summary of the invention
The object of the invention is to, a kind of control circuit and supply convertor are provided, can in the time of underloading, obtain less minimum ON time, further reduce the ripple of output voltage.
For solving the problems of the technologies described above, the invention provides a kind of control circuit, remain stable for controlling the output voltage of a supply convertor, comprise, current sampling circuit, voltage compensating circuit, minimum ON time limiting circuit and comparison circuit, wherein,
Described current sampling circuit, in order to produce the current feedback signal of inductive current in a sign power stage circuit;
Described voltage compensating circuit, be connected with the output of described power stage circuit, in order to receive feedback voltage and a reference voltage of output voltage of described power stage circuit, produce a voltage compensation signal, described voltage compensation signal characterizes the difference of feedback voltage and the reference voltage of described output voltage;
Described minimum ON time limiting circuit, in order to produce the ramp voltage signal of a rate of rise and the inversely proportional relation of described voltage compensation signal in the ON time of power switch pipe;
Comparison circuit, receives described ramp voltage signal, voltage compensation signal and current feedback signal, produces comparison control signal in order to the power switch pipe in switch-off power level circuit;
In the ON time of described power switch pipe, in the time having one to arrive described voltage compensation signal in described current feedback signal and described ramp voltage signal, comparison circuit is exported effective comparison control signal, in order to turn-off described power switch pipe, make the output voltage of described power stage circuit remain stable.
Optionally,
In the time of the first load condition, current feedback signal is greater than ramp voltage signal within the blanking time, described comparison circuit export the first comparison signal as described comparison control signal to control the shutoff of described power switch pipe;
In the time of the second load condition, current feedback signal is less than ramp voltage signal within the blanking time, described comparison circuit export the second comparison signal as described comparison control signal to control the shutoff of described power switch pipe.
Optionally, described control circuit also comprises a blanking time circuit, and described blanking time circuit receives described current feedback signal, and in the described blanking time section after described power switch pipe conducting, controlling described current feedback signal is disarmed state.
Optionally, described control circuit also comprises a logic control circuit, and described logic control circuit is according to described comparison control signal and clock signal, and output is in order to control the control signal of described power switch pipe; Wherein,
Clock signal is for opening the power switch pipe of described power stage circuit;
Comparison control signal is for turn-offing the power switch pipe of described power stage circuit.
Optionally, described minimum ON time limiting circuit comprises not gate, second switch pipe, the second electric capacity and current source, wherein:
Described not gate is in order to produce second control signal contrary with the control signal of described power switch pipe to second switch pipe, make in power switch pipe conduction period, second switch pipe turn-offs to start the work of minimum ON time limiting circuit, exports described ramp voltage signal; The input of described not gate receives the control signal of described power switch pipe;
The grid of described second switch pipe connects the output of described not gate, the source ground of described second switch pipe, and the drain electrode of described second switch pipe connects described comparison circuit;
One end of described the second electric capacity connects described comparison circuit, the other end ground connection of described the second electric capacity;
One end of described current source connects described comparison circuit, the other end ground connection of described current source, the current output value of described current source and the inversely proportional relation of described voltage compensation signal.
Optionally, described current sampling circuit is connected with the source electrode of described power switch pipe, in order to receive the inductor current signal of described power stage circuit, produces the current feedback signal of inductive current in the described power stage circuit of a sign.
Optionally, described voltage compensating circuit comprises trsanscondutance amplifier and the first electric capacity, wherein:
The inverting input of described trsanscondutance amplifier connects described feedback voltage, in-phase input end connects reference voltage, described trsanscondutance amplifier compares and enlarges described feedback voltage and reference voltage, the output termination of described trsanscondutance amplifier comprises the compensating circuit of the first electric capacity, to export the first voltage compensation signal at the output of described voltage compensating circuit;
One end of described the first electric capacity connects the output of described trsanscondutance amplifier, the other end ground connection of described the first electric capacity.
Optionally, described voltage compensating circuit comprises trsanscondutance amplifier, the first electric capacity and subtracter, wherein:
The inverting input of described trsanscondutance amplifier connects described feedback voltage, in-phase input end connects reference voltage, described trsanscondutance amplifier compares and enlarges described feedback voltage and reference voltage, the output termination of described trsanscondutance amplifier comprises the compensating circuit of the first electric capacity, to export the first voltage compensation signal at the output of described voltage compensating circuit;
One end of described the first electric capacity connects the output of described trsanscondutance amplifier, the other end ground connection of described the first electric capacity;
Described subtracter receives described voltage compensation signal and a triangular signal, described voltage compensation signal and a triangular signal is carried out after difference computing to output second voltage compensating signal.
Optionally, described control circuit also comprises voltage sampling circuit, and described voltage sampling circuit receives described output voltage, and exports described output voltage feedback signal.
According to another side of the present invention, a kind of supply convertor is also provided, comprise the control circuit described in as above any one, described supply convertor is peak-current mode control.
Compared with prior art, control circuit provided by the invention and supply convertor have the following advantages:
In control circuit provided by the invention and supply convertor, in the ON time of described power switch pipe, in the time having one to arrive described voltage compensation signal in described current feedback signal and described ramp voltage signal, described comparison circuit is exported effective comparison control signal, in order to turn-off described power switch pipe, make the output voltage of described power stage circuit remain stable.
Brief description of the drawings
Fig. 1 is the circuit diagram of supply convertor in prior art;
Fig. 2 is the circuit diagram of supply convertor in one embodiment of the invention;
Fig. 3 is the circuit diagram of voltage compensating circuit in another embodiment of the present invention;
Fig. 4 is the circuit diagram of voltage compensating circuit in further embodiment of this invention;
Fig. 5 is the oscillogram of supply convertor each signal in the time of the first load condition in one embodiment of the invention;
Fig. 6 is the oscillogram of supply convertor each signal in the time of the second load condition in one embodiment of the invention.
Embodiment
For clear, whole features of practical embodiments are not described.They in the following description, are not described in detail known function and structure, because can make the present invention chaotic due to unnecessary details.Will be understood that in the exploitation of any practical embodiments, must make a large amount of implementation details to realize developer's specific objective, for example, according to about system or about the restriction of business, change into another embodiment by an embodiment.In addition, will be understood that this development may be complicated and time-consuming, but be only routine work to those skilled in the art.
In the following passage, with way of example, the present invention is more specifically described with reference to accompanying drawing.According to the following describes and claims, advantages and features of the invention will be clearer.It should be noted that, accompanying drawing all adopts very the form of simplifying and all uses non-ratio accurately, only in order to convenient, the object of the aid illustration embodiment of the present invention lucidly.
Below illustrate detailed operation process of the present invention, please refer to Fig. 2, Fig. 2 is the circuit diagram of supply convertor in one embodiment of the invention.As shown in Figure 2, supply convertor 20 comprises power stage circuit 100 and control circuit 220.In the present embodiment, described power stage circuit 100 is the booster circuit of DC-DC converter technique, be that described power stage circuit 100 is for being converted into direct voltage by direct voltage, in other embodiments of the invention, described power stage circuit 100 can also be the change-over circuit of DC-AC conversion, AC-DC conversion, AC-AC conversion, this is what it will be appreciated by those skilled in the art that, and therefore not to repeat here.
Wherein, described power stage circuit 100 comprises: voltage input end 101, inductance L, voltage output end 102 and power switch pipe Q1.Wherein, described voltage input end 101 is for inputting an input voltage V
in, in the present embodiment, described input voltage V
infor direct current is come in and gone out.One end of described inductance L connects described voltage input end 101, and described voltage output end 102 is for exporting an output voltage V
o, described output voltage V
ocome in and go out for direct current, described voltage output end 102 connects the other end of described inductance L.The drain electrode of described power switch pipe Q1 connects described inductance L, the source ground of described power switch pipe Q1, and the grid of described power switch pipe Q1 receives a control signal BG.In addition, supply convertor 10 can also comprise input capacitance C
in, diode D, output capacitance C
out, load resistance R
ldeng element, this is what it will be appreciated by those skilled in the art that, and therefore not to repeat here.
Described control circuit 220 comprises current sampling circuit 226, voltage compensating circuit 222, minimum ON time limiting circuit 225 and comparison circuit 223.Wherein, described current sampling circuit 226 is in order to produce inductive current i in a sign power stage circuit 100
lcurrent feedback signal I
l.Described inductive current i
lfor the electric current of the described inductance L of flowing through, preferably, described blanking time circuit 221 connects the source electrode of described power switch pipe Q1, to obtain described current feedback signal I
l.In the present embodiment, I
l=K1 × i
l, K1 is the first coefficient.
As shown in Figure 2, preferably, described electric current adopts circuit 226 to connect the source electrode of described power switch pipe Q1, in order to receive the inductor current signal of described power stage circuit 100, produces one and characterizes inductive current i in described power stage circuit 100
lcurrent feedback signal I
l.Certainly, described current sampling circuit 226 is not limited to connect the source electrode of described power switch pipe Q1, as long as can make described current feedback signal I
lthe flow through current i of described inductance L of sign
l.Also within thought range of the present invention.
In the present embodiment, described control circuit 220 also comprises a blanking time circuit 221, and described blanking time circuit 221 receives described current feedback signal I
l, in the described blanking time section after described power switch pipe Q1 conducting, control described current feedback signal I
lfor disarmed state.
Described voltage compensating circuit 222 is connected with the output 102 of described power stage circuit 100, in order to receive the output voltage V of described power stage circuit 100
ofeedback voltage V
fwith a reference voltage V
ref, producing a voltage compensation signal, described voltage compensation signal characterizes described output voltage V
ofeedback voltage V
fwith reference voltage V
refdifference.
Optionally, described control circuit 220 also comprises voltage sampling circuit 227, and described voltage sampling circuit 227 receives described output voltage V
o, to survey described feedback voltage V
f, and export feedback voltage V
f.Described voltage sampling circuit 227 can comprise the first resistance R
1with the second resistance R
2, described the first resistance R
1one end connect described voltage output end 102, described the first resistance R
1the other end connect described the second resistance R
2one end, described the second resistance R
2other end ground connection, described the first resistance R
1the other end and described the second resistance R
2one end connect described voltage compensating circuit 222, to export described feedback voltage V to described voltage compensating circuit 222
f.Certainly, described voltage sampling circuit 227 is not limited to said structure, as long as can detect described feedback voltage V
f.
In the present embodiment, as shown in Figure 2, described voltage compensating circuit 222 comprises: trsanscondutance amplifier gm, the first capacitor C
1and subtracter 2221.The inverting input of described trsanscondutance amplifier gm connects described feedback voltage V
f, in-phase input end connects reference voltage V
ref, described trsanscondutance amplifier gm is by described feedback voltage V
fand reference voltage V
refcompare and enlarge, the output of described trsanscondutance amplifier gm is exported a compensate for poor value signal V
comp.The output termination of described trsanscondutance amplifier gm comprises the first capacitor C
1compensating circuit, with the output output second voltage compensating signal V at described voltage compensating circuit 222
comp-V
slope.Described the first capacitor C
1one end connect the output of described trsanscondutance amplifier gm, described the first capacitor C
1other end ground connection; Described subtracter receives described compensate for poor value signal V
compwith a triangular signal V
slope, by described compensate for poor value signal V
compwith a triangular signal V
slopecarry out after difference computing, export described second voltage compensating signal V
comp-V
slope.Described triangular signal V
slopefor in the ON time of described power switch pipe Q1, described voltage compensation signal can be declined, thereby can shorten the ON time of described power switch pipe Q1.In the present embodiment, described second voltage compensating signal V
comp-V
slopeas described voltage compensation signal.
Described voltage compensating circuit 222 is not limited to said structure, and as shown in Figure 3, in another embodiment of the present invention, described voltage compensating circuit 322 can also comprise: trsanscondutance amplifier gm and the first capacitor C
1.The inverting input of described trsanscondutance amplifier gm connects described feedback voltage V
f, in-phase input end connects reference voltage V
ref, described trsanscondutance amplifier gm is by described feedback voltage V
fand reference voltage V
refcompare and enlarge, the output of described trsanscondutance amplifier gm is exported a compensate for poor value signal V
comp.The output termination of described trsanscondutance amplifier gm comprises the first capacitor C
1compensating circuit, to export the first voltage compensation signal V at the output of described voltage compensating circuit 222
comp, described the first voltage compensation signal is described compensate for poor value signal V
comp.Described the first capacitor C
1one end connect the output of described trsanscondutance amplifier gm, described the first capacitor C
1other end ground connection.In another embodiment of the present invention, described the first voltage compensation signal is as described voltage compensation signal.
And for example, as shown in Figure 4, in another embodiment of the present invention, described voltage compensating circuit 422 can also comprise: error amplifier EA and the 3rd capacitor C
3, described the 3rd capacitor C
3be connected between the inverting input and output of described error amplifier EA, thus the compensating circuit of composition.The inverting input of described error amplifier EA connects described feedback voltage V
f, in-phase input end connects reference voltage V
ref, described error amplifier EA is by described feedback voltage V
fand reference voltage V
refcompare and enlarge, the output of described error amplifier EA is exported a compensate for poor value signal V
comp, described the first voltage compensation signal is described compensate for poor value signal V
comp, in another embodiment of the present invention, described the first voltage compensation signal is as described voltage compensation signal.Certainly, can also connect a subtracter at the output of described error amplifier EA, described subtracter receives described compensate for poor value signal V
compwith a triangular signal V
slope, by described compensate for poor value signal V
compwith a triangular signal V
slopecarry out after difference computing, export described second voltage compensating signal V
comp-V
slope.According to foregoing description of the present invention, this is what it will be appreciated by those skilled in the art that, does not repeat at this.
Described minimum ON time limiting circuit 225 in order to produce the ramp voltage signal V of a rate of rise and the inversely proportional relation of described voltage compensation signal in the ON time of power switch pipe Q1
ramp.As shown in Figure 2, in the present embodiment, described minimum ON time limiting circuit 225 comprises not gate 2251, second switch pipe Q
2, the second capacitor C
2, current source 2252.Described not gate 2251 is in order to produce second control signal contrary with the control signal GB of described power switch pipe Q1 to second switch pipe Q
2, make in power switch pipe Q1 conduction period second switch pipe Q
2turn-off and work to start minimum ON time limiting circuit 225, export described ramp voltage signal V
ramp; The input of described not gate 2251 receives the control signal GB of described power switch pipe Q1; The grid Q of described second switch pipe
2connect the output of described not gate 2251, the source electrode Q of described second switch pipe
2ground connection, described second switch pipe Q
2drain electrode connect described comparison circuit 223; Described the second capacitor C
2one end connect described comparison circuit 223, described the second capacitor C
2other end ground connection; One end of described current source 2252 connects described comparison circuit 223, the other end ground connection of described current source 2252, the current output value I of described current source 2252
1with the inversely proportional relation of described the first voltage compensation signal.
In the time of described the first power switch pipe Q1 conducting, described second switch pipe Q
2not conducting, described current source 2252 is to described the second capacitor C
2charging, makes described ramp voltage signal V
ramprise; In the time of described the first not conducting of power switch pipe Q1, described second switch pipe Q
2conducting, described current source 2252 and described the second capacitor C
2short circuit, described ramp voltage signal V
rampremain unchanged.
Preferably, within described the first power switch pipe Q1 conduction period, described output voltage V
ofeedback voltage V
fwith reference voltage V
refdifference V
compoutput current I with described current source 2252
1be inversely proportional to, I
1=K2/V
comp, K2 is the second coefficient.The output current I of described current source 2252
1be not limited to above-mentioned open, as long as described output current I
1in the time of described the first power switch pipe Q1 conducting, described ramp voltage signal V
ramprise, and make in the time of underloading described ramp voltage signal V
rampfirst arrive described voltage compensation signal.
Described comparison circuit 223 receives described ramp voltage signal V
ramp, voltage compensation signal and the current feedback signal I that processed through described blanking time circuit 221
l, produce comparison control signal Va in order to the power switch pipe Q1 in switch-off power level circuit 100.In the ON time of described power switch pipe Q1, as described current feedback signal I
lwith described ramp voltage signal V
rampwhile having one to arrive described voltage compensation signal in both, described comparison circuit 223 is exported effective comparison control signal Va, in order to turn-off described power switch pipe Q1, makes the output voltage V of described power stage circuit 100
oremain stable.
Preferably, described control circuit 220 also comprises a logic control circuit 224, and described logic control circuit 224 is according to described comparison control signal Va and clock signal clk, and output is in order to control the control signal BG of described power switch pipe Q1; Wherein, described clock signal clk is for opening the power switch pipe Q1 of described power stage circuit 100; Described comparison control signal Va is for turn-offing the power switch pipe Q1 of described power stage circuit 100.As shown in Figure 2, described logic control circuit 224 can be rest-set flip-flop etc.
In the present embodiment, described control circuit 220 is in when work, and described comparison circuit 123 is for by described ramp voltage signal V
rampwith the current feedback signal I processing through described blanking time circuit 221
lrespectively with described second voltage compensating signal V
comp-V
slopecompare:
As described in ramp voltage signal V
rampwith the current feedback signal I processing through described blanking time circuit 221
lall do not reach described second voltage compensating signal V
comp-V
slope, described comparison control signal Va controls described logic control circuit 224 and produces invalid described control signal BG;
As described in ramp voltage signal V
rampreach described second voltage compensating signal V
comp-V
slope, or the current feedback signal I processing through described blanking time circuit 221
lreach described second voltage compensating signal V
comp-V
slope, described comparison control signal Va controls described logic control circuit 224 and produces effective described control signal BG, and described power switch pipe turn-offs Q1.
With reference to figure 5, described power stage circuit 100 is in the time of the first load condition, at a time cycle (moment t
1-moment t
2) start time, i.e. moment t
1, in described blanking time Blanking time, described blanking time circuit 221 is controlled described current feedback signal I
lblanking.Described the first power switch pipe Q1 conducting, at the ON time t of described the first power switch pipe Q1
on_1 'in, described ramp voltage signal V
rampwith current feedback signal I
lall rise, described current feedback signal I
lclimbing speed be greater than described ramp voltage signal V
rampclimbing speed, after described blanking time interval B lanking time finishes, described blanking time circuit 221 is not to described current feedback signal I
lblanking.At moment t
4, described current feedback signal I
lfirst arrive described second voltage compensating signal V
comp-V
slope, described comparison circuit 223 export the first comparison signal as described comparison control signal Va to control the shutoff of described power switch pipe Q1.Described the first power switch pipe Q1 closes and has no progeny, and described power switch pipe G2 conducting, at the ON time t of described second switch pipe G2
on_2 'in, described ramp voltage signal V
rampkeep low-voltage constant.
With reference to figure 6, described power stage circuit 100 is (light condition, the load under the second load condition is less than the load under the first load condition) in the time of the second load condition, is time cycle (moment t at one
1-moment t
2) start time, i.e. moment t
1, in described blanking time Blanking time, described blanking time circuit 221 is controlled described current feedback signal I
lblanking.Described the first power switch pipe Q1 conducting, at the ON time t of described the first power switch pipe Q1
on_1in, described ramp voltage signal V
rampwith current feedback signal I
lall rise, described ramp voltage signal V
rampclimbing speed be greater than described current feedback signal I
lclimbing speed, after described blanking time interval B lanking time finishes, at moment t
3, described ramp voltage signal V
rampfirst arrive described second voltage compensating signal V
comp-V
slopedescribed comparison circuit 223 export the second comparison signal as described comparison control signal Va to control the shutoff of described power switch pipe Q1, thereby can make the minimum ON time of described the first power switch pipe Q1 not be subject to the restriction of described blanking time, can further reduce the ripple of output voltage.Described the first power switch pipe Q1 closes and has no progeny, and described power switch pipe G2 conducting, at the ON time t of described second switch pipe G2
on_2in, described ramp voltage signal V
rampkeep low-voltage constant.
In the present embodiment, can be by regulating the value of described the first COEFFICIENT K 1 and the second COEFFICIENT K 2, to make described ramp voltage signal V
rampwith current feedback signal I
lvariation meet the demands.
Obviously, those skilled in the art can carry out various changes and modification and not depart from the spirit and scope of the present invention the present invention.Like this, if these amendments of the present invention and within modification belongs to the scope of the claims in the present invention and equivalent technologies thereof, the present invention is also intended to comprise these changes and modification interior.
Claims (10)
1. a control circuit, remains stable for controlling the output voltage of a supply convertor, it is characterized in that, comprise, and current sampling circuit, voltage compensating circuit, minimum ON time limiting circuit and comparison circuit, wherein,
Described current sampling circuit, in order to produce the current feedback signal of inductive current in a sign power stage circuit;
Described voltage compensating circuit, be connected with the output of described power stage circuit, in order to receive feedback voltage and a reference voltage of output voltage of described power stage circuit, produce a voltage compensation signal, described voltage compensation signal characterizes the difference of feedback voltage and the reference voltage of described output voltage;
Described minimum ON time limiting circuit, in order to produce the ramp voltage signal of a rate of rise and the inversely proportional relation of described voltage compensation signal in the ON time of power switch pipe;
Comparison circuit, receives described ramp voltage signal, voltage compensation signal and current feedback signal, produces comparison control signal in order to the power switch pipe in switch-off power level circuit;
In the ON time of described power switch pipe, in the time having one to arrive described voltage compensation signal in described current feedback signal and described ramp voltage signal, described comparison circuit is exported effective comparison control signal, in order to turn-off described power switch pipe, make the output voltage of described power stage circuit remain stable.
2. control circuit as claimed in claim 1, is characterized in that,
In the time of the first load condition, described current feedback signal is greater than ramp voltage signal within the blanking time, described comparison circuit export the first comparison signal as described comparison control signal to control the shutoff of described power switch pipe;
In the time of the second load condition, described current feedback signal is less than ramp voltage signal within the blanking time, described comparison circuit export the second comparison signal as described comparison control signal to control the shutoff of described power switch pipe.
3. control circuit according to claim 2, it is characterized in that, described control circuit also comprises a blanking time circuit, described blanking time circuit receives described current feedback signal, in described blanking time section after described power switch pipe conducting, controlling described current feedback signal is disarmed state.
4. control circuit as claimed in claim 1, is characterized in that, described control circuit also comprises a logic control circuit, and described logic control circuit is according to described comparison control signal and clock signal, and output is in order to control the control signal of described power switch pipe; Wherein,
Described clock signal is for opening the power switch pipe of described power stage circuit;
Described comparison control signal is for turn-offing the power switch pipe of described power stage circuit.
5. control circuit as claimed in claim 1, is characterized in that, described minimum ON time limiting circuit comprises not gate, second switch pipe, the second electric capacity and current source, wherein:
Described not gate is in order to produce second control signal contrary with the control signal of described power switch pipe to second switch pipe, make in power switch pipe conduction period, second switch pipe turn-offs to start the work of minimum ON time limiting circuit, exports described ramp voltage signal; The input of described not gate receives the control signal of described power switch pipe;
The grid of described second switch pipe connects the output of described not gate, the source ground of described second switch pipe, and the drain electrode of described second switch pipe connects described comparison circuit;
One end of described the second electric capacity connects described comparison circuit, the other end ground connection of described the second electric capacity;
One end of described current source connects described comparison circuit, the other end ground connection of described current source, the current output value of described current source and the inversely proportional relation of described voltage compensation signal.
6. control circuit as claimed in claim 1, it is characterized in that, described current sampling circuit is connected with the source electrode of described power switch pipe, in order to receive the inductor current signal of described power stage circuit, produces the current feedback signal of inductive current in the described power stage circuit of a sign.
7. control circuit as claimed in claim 1, is characterized in that, described voltage compensating circuit comprises trsanscondutance amplifier and the first electric capacity, wherein:
The inverting input of described trsanscondutance amplifier connects described feedback voltage, in-phase input end connects reference voltage, described trsanscondutance amplifier compares and enlarges described feedback voltage and reference voltage, the output termination of described trsanscondutance amplifier comprises the compensating circuit of the first electric capacity, to export the first voltage compensation signal at the output of described voltage compensating circuit;
One end of described the first electric capacity connects the output of described trsanscondutance amplifier, the other end ground connection of described the first electric capacity.
8. control circuit as claimed in claim 1, is characterized in that, described voltage compensating circuit comprises trsanscondutance amplifier, the first electric capacity and subtracter, wherein:
The inverting input of described trsanscondutance amplifier connects described feedback voltage, in-phase input end connects reference voltage, described trsanscondutance amplifier compares and enlarges described feedback voltage and reference voltage, the output termination of described trsanscondutance amplifier comprises the compensating circuit of the first electric capacity, to export the first voltage compensation signal at the output of described voltage compensating circuit;
One end of described the first electric capacity connects the output of described trsanscondutance amplifier, the other end ground connection of described the first electric capacity;
Described subtracter receives described voltage compensation signal and a triangular signal, described voltage compensation signal and a triangular signal is carried out after difference computing to output second voltage compensating signal.
9. control circuit as claimed in claim 1, is characterized in that, described control circuit also comprises voltage sampling circuit, and described voltage sampling circuit receives described output voltage, and exports described output voltage feedback signal.
10. a supply convertor, is characterized in that, comprises the control circuit as described in any one in claim 1-9, and described supply convertor is peak-current mode control.
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