CN103246302B - A kind of output current sampling and constant output current control circuit and method - Google Patents
A kind of output current sampling and constant output current control circuit and method Download PDFInfo
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- CN103246302B CN103246302B CN201210023831.1A CN201210023831A CN103246302B CN 103246302 B CN103246302 B CN 103246302B CN 201210023831 A CN201210023831 A CN 201210023831A CN 103246302 B CN103246302 B CN 103246302B
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Abstract
The invention discloses the method for the sampling of a kind of output current and constant output current control, it is characterized in that, be jointly realize making steady current be in steady state all the time by output current sample circuit, constant-current control circuit and peak current control circuitry; Described output current sample circuit, when switching tube Q1 conducting, carries out voltage sample to detection resistance R1, obtains inductive current mean value, and delivers to constant-current control circuit control output current, makes it to be in steady state value all the time; Described constant-current control circuit is that the signal sent here by sample circuit and current reference Vr1 compare generation error signal, error signal is delivered to the turn-off time that Toff controller removes gauge tap pipe Q1 again, realize R1 setting as long as final after, output current is just constant.Employing the invention enables output current at input voltage and output voltage, and when even inductance L 1 changes, output current is in steady state value all the time.
Description
Technical field
The present invention relates to the sampling of a kind of output current based on Switching Power Supply BUCK topology and constant output current control circuit and method.
Background technology
As shown in Figure 1: a kind of traditional output constant current circuit based on Switching Power Supply BUCK topology, it mainly comprises detection resistance R1, comparer U3, current peak benchmark Vr2, the turn-off time arranges resistance R2, Toff controller, control & driving, switching tube Q1, inductance L 1, continue stream diode D1, input capacitance C3 and output capacitance C4.Wherein detect the source electrode of one end connecting valve pipe Q1 and the negative pole of comparer U3 of resistance R1, detect the other end ground connection of resistance R1, the positive pole of comparer U3 connects the positive pole of current peak benchmark Vr2, the minus earth of current peak benchmark Vr2, one input end of the output terminal connection control & driving of comparer U3, another input end of comparer U3 connects the output terminal of Toff controller, the other end of Toff controller connects one end that the turn-off time arranges resistance R2, and the turn-off time arranges the other end ground connection of resistance R2.The grid of the output terminal connecting valve pipe Q1 that control & drives, the drain electrode of switching tube Q1 connects the continue anode of stream diode D1 and one end of inductance L 1, the other end of inductance L 1 connects negative pole and the output negative pole of output capacitance, the negative electrode of stream diode D1 of continuing connects the minus earth of the positive pole of output capacitance C4, the positive pole of input capacitance C3, output cathode and DCBUS, input capacitance C3.
Wherein, Fig. 2 is the constant current schematic diagram of Fig. 1 constant-current circuit.IL is the electric current of main inductance L1 in BUCK topology, and its average current ILav equals output current.Wherein, ILav is inductance average current; ILpk is sense peak point current, and it controls by comparer U3 and current peak benchmark Vr2 and detection resistance R1, when ILpk after R1 setting is also just fixed; ILr is inductance ripple current, and it controls by the inductance value of output voltage Vo, inductance L 1 and turn-off time Toff, and when output voltage Vo is constant, after the sensibility reciprocal setting of inductance L 1, toff fixed by Toff controller simultaneously, and ripple current value ILr is constant.Like this when fixing output voltage, ILpk is constant, and ILr is constant, and ILav is just constant, thus output current is also just constant, and it doesn't matter with the change of input voltage.
This control mode is because circuit structure is simple, cost is low, so apply very wide in LED constant current driving power, but its shortcoming is also clearly equally, be exactly when output voltage changes, ILr will change, thus ILav will change, and output current just can not be constant.
Summary of the invention
For above-mentioned problems of the prior art, the object of the invention is: provide the sampling of a kind of output current and constant output current control circuit and method, make output current at input voltage and output voltage, when even inductance L 1 changes, output current is in steady state value all the time.
The technical solution adopted for the present invention to solve the technical problems is:
A kind of output current sampling and constant output current control circuit, it is characterized in that, by output current sample circuit, constant-current control circuit and peak current control circuitry realize jointly, its integrated circuit structure is: the source electrode detecting one end connecting valve pipe Q1 of resistance R1, one end of sampling switch S1 and the negative pole of comparer U3, detect the other end ground connection of resistance R1, the other end of sampling switch S1 connects one end of sampling resistor R2, the other end of sampling resistor R2 connects one end joint of sampling capacitance C1 and the negative pole of amplifier U1, the other end ground connection of sampling capacitance C1, the positive pole of amplifier U1 connects the positive pole of current reference Vr1, the minus earth of current reference Vr1, the output terminal of amplifier U1 connects integral restrictor S2, the other end of integral restrictor S2 connects one end of integrating capacitor C2 and the input end of Toff controller, the other end ground connection of integrating capacitor C2, the output terminal of Toff controller is connected to an input end of control & driving, another input end that control & drives connects the output terminal of comparer U3, the positive pole of comparer U3 connects the positive pole of current peak benchmark Vr2, the negative pole of current peak benchmark Vr2 connects ground, the output terminal that control & drives connects the grid of hysteretic controller U2 and switching tube Q1, the output terminal of hysteretic controller U2 connects the control end of sampling switch S1 and the control end of long-pending switch S 2, the drain electrode of switching tube Q1 connects the continue anode of stream diode D1 and one end of inductance L 1, the negative electrode of stream diode D1 of continuing connects the positive pole of input capacitance C3, the positive pole of output capacitance C4, DCBUS and output cathode, the other end of inductance L 1 connects negative pole and the output negative pole of output capacitance C4.
The method that output current sampling and constant output current control, adopts above-mentioned output current to sample and constant output current control circuit; Wherein, described output current sample circuit is by sampling resistor R2, sampling capacitance C1, sampling switch S1 and hysteretic controller U2, when switching tube Q1 conducting, voltage sample is carried out to the detection resistance R1 of reaction inductive current change, thus obtain inductive current mean value accurately, the i.e. size of output current, and deliver to constant-current control circuit go control output current, make it to be in steady state value all the time.
Described constant-current control circuit is that the signal of the reaction output current size sent here by output current sample circuit and current reference Vr1 compare, and produce error signal, by integral restrictor S2, error signal is delivered to integrating capacitor C2 again, signal afterwards on integrating capacitor C2 goes by delivering to Toff controller to the turn-off time of gauge tap pipe Q1, as long as after final realization detects resistance R1 setting, output current is just constant, and has nothing to do with the inductance value of inductance L 1 with input voltage, output voltage.
Error signal, by the control of hysteretic controller, only when switching tube Q1 conducting, is just delivered to integrating capacitor C2 by described integral restrictor S2, makes signal on integrating capacitor C2 can the value of accurate response output current more.
Described peak current control circuitry is made up of comparer U3, current peak benchmark Vr2 and detection resistance R1, that the signal of the current value size detected on resistance R1 in reaction inductance L 1 is delivered to comparer U3, compare with current peak benchmark Vr2 again, when equaling current peak benchmark Vr2, control & driver, by on-off switching tube Q1, makes output current equal the value set.
The invention has the beneficial effects as follows: adopt and the invention enables output current at input voltage and output voltage, when even inductance L 1 changes, output current is in steady state value all the time.
Accompanying drawing explanation
Fig. 1 is a kind of circuit of traditional output constant current based on Switching Power Supply BUCK topology;
Fig. 2 is the constant current schematic diagram of Fig. 1 constant-current circuit;
Fig. 3 is the circuit that the method for the sampling of a kind of output current and constant output current control is specifically implemented.
Embodiment
In conjunction with the accompanying drawings, the present invention is further detailed explanation.
As shown in Figure 1: the circuit being a kind of traditional output constant current based on Switching Power Supply BUCK topology, its principle is as Fig. 2, it can well when input voltage DCBUS changes constant output current, but when output voltage changes, it just can not constant output current.
For overcoming the above problems, the present invention proposes the sampling of a kind of output current and constant output current control circuit and method, and existing composition graphs 3 sets forth the specific embodiment of the present invention.
The present invention is by detecting resistance R1, sampling switch S1, the mean value size of sampling resistor R2 and sampling capacitance C2 to inductive current is sampled, this average current is output current size, deliver to amplifier U1 afterwards, then compare with current reference Vr1, and produce error signal, again this error signal is delivered to the same integral restrictor S2 controlled by hysteretic controller U2, deliver to integrating capacitor C2 again, wherein hysteretic controller U2 only when switching tube Q1 conducting, can open sampling switch S1.Again the error signal of the output current of reaction and the output current of setting on integrating capacitor C2 is delivered to Toff controller, the turn-off time of configuration switch pipe Q1.Thus reach and make output current equal current reference Vr1 all the time divided by detection resistance R1, so, the size of output current just has nothing to do with the inductance value of input voltage, output voltage and inductance L 1, thus achieves real constant output current.
Equally, technical scheme of the present invention can be understood from following two aspects:
One, adopt output current sample circuit, make the signal sampled can react the size of output current accurately.
Two, by output current is compared generation one error amount with current reference, this error amount delivers to Toff controller by integral restrictor, integrating capacitor again, thus the turn-off time of gauge tap pipe, finally make output current equal the value set; Wherein sampling switch and integral restrictor control by hysteretic controller, and only open sampling open pipe and integral restrictor when switching tube Q1 conducting.
Claims (5)
1. an output current sampling and constant output current control circuit, it is characterized in that, by output current sample circuit, constant-current control circuit and peak current control circuitry realize jointly, its integrated circuit structure is: the source electrode detecting one end connecting valve pipe Q1 of resistance R1, one end of sampling switch S1 and the negative pole of comparer U3, detect the other end ground connection of resistance R1, the other end of sampling switch S1 connects one end of sampling resistor R2, the other end of sampling resistor R2 connects one end joint of sampling capacitance C1 and the negative pole of amplifier U1, the other end ground connection of sampling capacitance C1, the positive pole of amplifier U1 connects the positive pole of current reference Vr1, the minus earth of current reference Vr1, the output terminal of amplifier U1 connects integral restrictor S2, the other end of integral restrictor S2 connects one end of integrating capacitor C2 and the input end of Toff controller, the other end ground connection of integrating capacitor C2, the output terminal of Toff controller is connected to an input end of control & driving, another input end that control & drives connects the output terminal of comparer U3, the positive pole of comparer U3 connects the positive pole of current peak benchmark Vr2, the negative pole of current peak benchmark Vr2 connects ground, the output terminal that control & drives connects the input end of hysteretic controller U2 and the grid of switching tube Q1, the output terminal of hysteretic controller U2 connects the control end of sampling switch S1 and the control end of integral restrictor S2, the drain electrode of switching tube Q1 connects the continue anode of stream diode D1 and one end of inductance L 1, the negative electrode of stream diode D1 of continuing connects the positive pole of input capacitance C3, the positive pole of output capacitance C4, DCBUS and output cathode, the other end of inductance L 1 connects negative pole and the output negative pole of output capacitance C4, the minus earth of input capacitance C3.
2. a method for output current sampling and constant output current control, is characterized in that, adopts a kind of output current sampling as claimed in claim 1 and constant output current control circuit;
Described output current sample circuit is by sampling resistor R2, sampling capacitance C1, sampling switch S1 and hysteretic controller U2, when switching tube Q1 conducting, voltage sample is carried out to the detection resistance R1 of reaction inductive current change, thus obtain inductive current mean value accurately, the i.e. size of output current, and deliver to constant-current control circuit go control output current, make it to be in steady state value all the time.
3. the method for a kind of output current sampling as claimed in claim 2 and constant output current control, it is characterized in that, described constant-current control circuit is that the signal of the reaction output current size sent here by output current sample circuit and current reference Vr1 compare, and produce error signal, by integral restrictor S2, error signal is delivered to integrating capacitor C2 again, signal afterwards on integrating capacitor C2 goes by delivering to Toff controller to the turn-off time of gauge tap pipe Q1, as long as after final realization testing circuit R1 sets, output current is just constant, and and input voltage, output voltage has nothing to do with the inductance value of inductance L 1.
4. the method for a kind of output current sampling as claimed in claim 2 and constant output current control, it is characterized in that, described integral restrictor S2 is by the control of hysteretic controller U2, only when switching tube Q1 conducting, just error signal is delivered to integrating capacitor C2, make signal on integrating capacitor C2 can the value of accurate response output current more.
5. the method for a kind of output current sampling as claimed in claim 2 and constant output current control, it is characterized in that, described peak current control circuitry is made up of comparer U3, current peak benchmark Vr2 and detection resistance R1, that the signal of the current value size detected on resistance R1 in reaction inductance L 1 is delivered to comparer U3, compare with current peak benchmark Vr2 again, when equaling current peak benchmark Vr2, control & drives on-off switching tube Q1, makes output current equal the value set.
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| CN201210023831.1A CN103246302B (en) | 2012-02-03 | 2012-02-03 | A kind of output current sampling and constant output current control circuit and method |
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| CN201210023831.1A CN103246302B (en) | 2012-02-03 | 2012-02-03 | A kind of output current sampling and constant output current control circuit and method |
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| CN103246302B true CN103246302B (en) | 2015-12-16 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108809092A (en) * | 2017-04-28 | 2018-11-13 | 张义 | A kind of control circuit and method increasing driving capability and constant output current |
| CN107086784B (en) * | 2017-06-20 | 2023-09-29 | 上海灿瑞微电子有限公司 | BUCK circuit topology |
| CN109921625B (en) * | 2019-03-25 | 2023-09-08 | 西南交通大学 | PFC converter pulse frequency modulation mean current control method and device |
| CN110473508B (en) * | 2019-08-16 | 2021-11-12 | 深圳南云微电子有限公司 | Buzzer driving method and driving circuit for realizing wide voltage input |
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| CN101925236A (en) * | 2010-08-20 | 2010-12-22 | 杭州电子科技大学 | Isolated high-power factor flyback type primary-side constant-current control device of LED driver |
| CN201805600U (en) * | 2010-09-30 | 2011-04-20 | 杭州电子科技大学 | Primary-side constant-current control device of LED driver |
| CN102076138A (en) * | 2009-11-25 | 2011-05-25 | 北京交通大学 | Electric supply input LED (Light Emitting Diode) constant current driver |
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- 2012-02-03 CN CN201210023831.1A patent/CN103246302B/en not_active Expired - Fee Related
Patent Citations (6)
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| CN101056058A (en) * | 2007-05-08 | 2007-10-17 | 魏其萃 | Constant shut-off time control scheme controlled by the high-precision average output current |
| CN101511141A (en) * | 2009-03-16 | 2009-08-19 | 无锡矽瑞微电子有限公司 | Control technique for switch power supply, inductance and current |
| CN102076138A (en) * | 2009-11-25 | 2011-05-25 | 北京交通大学 | Electric supply input LED (Light Emitting Diode) constant current driver |
| CN101795077A (en) * | 2010-04-12 | 2010-08-04 | Bcd半导体制造有限公司 | A kind of device of control change device output current voltage response |
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