CN103138556B - Pfc circuit, load driving circuits and signal control method - Google Patents
Pfc circuit, load driving circuits and signal control method Download PDFInfo
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/37—Converter circuits
- H05B45/3725—Switched mode power supply [SMPS]
- H05B45/385—Switched mode power supply [SMPS] using flyback topology
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
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Abstract
The invention discloses a kind of pfc circuit, load driving circuits and signal control method, the input of described pfc circuit receives chopping voltage, and described pfc circuit comprises: main switch and Ton control unit; The control signal of described Ton control unit, being less than or equal in maximum range, with the copped wave angle positive correlation of described chopping voltage; Described pfc circuit also comprises: detect compensating unit, for detecting the copped wave angle of chopping voltage, generates amplitude and the positively related compensating signal in copped wave angle; Control according to the comparison signal of described compensating signal to Ton control unit, make to be less than or equal in maximum range in described control signal, the control signal rising that equal copped wave angle is corresponding.The present invention can shorten the invalid adjustment process in dimming process.
Description
Technical Field
The invention relates to the field of circuits, in particular to a PFC circuit, a load driving circuit and a signal control method.
Background
In the field of lighting, there are many occasions where the brightness or color of a light source needs to be adjusted, which requires an adjustment function of the lighting system. At present, chopping dimming technology is commonly used, as shown in fig. 1, a dotted line part is an implementation structure of an existing chopping dimmer, after a power grid voltage Vac is acted by the chopping dimmer, a voltage on a light source load RL is a chopping voltage as shown in fig. 2, and a phase angle α corresponding to a trigger conduction time of a transistor TRIAC in the chopping dimmer is a chopping angle of the chopping voltage. The chopping dimmer internal resistor R11 is a variable resistor, and adjusting the resistance of the variable resistor R11 can change the size of the chopping angle α, specifically: the smaller the resistance value of the variable resistor R11 is, the shorter the triggering and conducting time of the transistor TRIAC is, and the smaller the chopping angle alpha is; the larger the resistance of the variable resistor R11, the longer the on-time of the trigger of the transistor TRIAC, and the larger the chopping angle α. When the variable resistor R11 is adjusted to the maximum resistance value, the corresponding chopping angle α is called the maximum chopping angle, and when the variable resistor R11 is adjusted to the minimum resistance value, the corresponding chopping angle α is called the minimum chopping angle.
However, when the light source load is a non-resistive light source and needs to be driven by a driving circuit, the dimming principle is different from the above principle. As shown in fig. 3, the adjustable light driving circuit when the light source load is an LED, the load driving circuit includes: the system comprises a first rectifier and a PFC circuit, wherein the chopped voltage is obtained by a grid voltage Vac after passing through a chopping dimmer and the first rectifier and is used as an input voltage Vin of the PFC circuit, the input current of the PFC circuit is Iin, and the output current Io of the PFC circuit is used for driving a load. The PFC circuit further includes: a current control unit, a ton control unit, and a drive control unit; wherein,
the current control unit samples the output current Io of the PFC circuit, compares a sampling signal with a reference signal, and outputs a control signal Vr after closed loop regulation, wherein the change of the control signal Vr is inversely related to the change of the output current Io, namely when the output current Io is reduced, the control signal Vr is increased, and otherwise, when the output current Io is increased, the control signal Vr is reduced. And, this control signal Vr has a maximum value Vrmax, i.e. when Vr is equal to Vrmax, Vr does not increase anymore when the output current Io continues to decrease.
the ton control unit compares the control signal Vr with a comparison signal Vp to determine the on time ton of the main switching transistor S1, and the drive control unit outputs the drive signal Vd according to the on time to control the main switching transistor S1. Specifically, as shown in fig. 4, the comparison signal Vp is a triangular wave or a sawtooth wave, the time when the comparison signal Vp starts to increase is the start time of the on-time Ton of the main switch tube S1, the time when the peak value of the comparison signal Vp is equal to the amplitude of the control signal Vr is the off-time of the on-time Ton of the main switch tube S1, that is, when Vr is equal to Vrmax, the on-time Ton of the main switch tube S1 is the maximum value Ton-max.
When the chopping angle alpha of the chopping voltage output by the chopping dimmer is zero, the current control unit works in a closed loop state, and the output current Io of the PFC circuit is basically constant; when the chopping angle alpha is increased from zero, the average value of the chopping voltage is reduced, so that the output current Io of the PFC circuit is reduced, the sampling signal of the output current Io received by the current control unit is reduced, the control signal Vr output by the current control unit is increased, the on-time Ton of the main switching tube S1 is prolonged through the Ton control unit, and the output current Io of the PFC circuit is maintained to be basically constant; when the chopping angle α is increased to α x and the control signal Vr output by the current control unit is increased to Vrmax, the current control unit is in the critical state of the closed-loop and open-loop, that is: when the chopping angle alpha is continuously increased from the current value alpha x, the average value of the chopping voltage is continuously reduced, the output current Io of the PFC circuit is reduced, Vr is not increased any more because Vr is equal to Vrmax, the on-time Ton of the main switching tube S1 is equal to the maximum value Ton-max and is not increased any more, the current control unit is in an open loop state, namely the reduction of the output current Io of the PFC circuit cannot change the control signal Vr output by the current control unit, and therefore the output current Io of the PFC circuit cannot be adjusted by changing the on-time of the main switching tube S1. It can be seen that since the state of the current control unit corresponding to Vrmax is the closed-loop open-loop critical state, Vr is closer to the critical state as larger.
When the current control unit is in the open-loop state, the on-time Ton of the main switching tube S1 is constant and equal to the maximum value Ton-max, that is, when the chopping angle α continues to increase from the critical value α x, the average value of the input voltage Vin of the PFC circuit decreases, and therefore, the output current Io of the PFC circuit decreases, so as to implement: in the range greater than the critical value α x, when the chopping angle α increases, the output current Io of the PFC circuit decreases, and when the chopping angle α decreases, the output current Io of the PFC circuit increases, thereby realizing dimming.
Therefore, the chopping dimmer can realize the dimming function only when the current control unit is in the open-loop state during the change of the chopping angle α. In the process that the chopping dimmer regulates the chopping angle alpha of the chopping voltage from zero to the critical value alpha x, the output current Io of the PFC circuit is kept unchanged, so that the dimming is meaningless, and the regulation process at the stage is an invalid regulation process for a user.
Therefore, how to shorten the ineffective adjustment process in the dimming process is a problem to be solved.
Disclosure of Invention
In view of the above, the present invention provides a PFC circuit, a load driving circuit and a signal control method, which can shorten an invalid dimming process in a dimming process.
Therefore, the embodiment of the invention adopts the following technical scheme:
the embodiment of the invention provides a PFC circuit, wherein the input end of the PFC circuit receives chopped wave voltage, and the PFC circuit comprises: a main switching tube and a Ton control unit; the control signal of the Ton control unit is positively correlated with the chopping angle of the chopping voltage within the range of being less than or equal to the maximum value;
the PFC circuit further includes:
the detection compensation unit is used for detecting a chopping angle of the chopping voltage and generating a compensation signal with positive correlation between the amplitude and the chopping angle; and controlling the comparison signal of the Ton control unit according to the compensation signal, so that the control signals corresponding to the equal chopping angles are increased within the range that the control signals are less than or equal to the maximum value.
Wherein, detect the compensation unit and include:
a detection subunit for detecting a chopping angle of the chopping voltage;
the generating subunit is used for generating a compensation signal with positive correlation between the amplitude and the chopping angle;
and the control subunit is used for controlling the comparison signal of the Ton control unit according to the compensation signal.
The control subunit is specifically configured to: the compensation signal is superimposed on the comparison signal of the Ton control unit.
The compensation signal is a current signal; the comparison signal is a sawtooth wave signal;
the Ton control unit includes: the constant current source is grounded through a first capacitor and a second switching tube respectively, and the ungrounded first end of the first capacitor is connected with the inverting input end of the first operational amplifier; the positive phase input end of the first operational amplifier is used for receiving a control signal;
the control subunit includes: two output ends of the generating subunit are respectively connected with two ends of the first capacitor.
The compensation signal is a voltage signal; the comparison signal is a sawtooth wave signal, and the compensation signal is a level signal;
the Ton control unit includes: the positive phase input end of the first operational amplifier is used for receiving a control signal;
the control subunit includes:
the first input end is used for receiving a comparison signal and is also connected with the inverting input end of the first operational amplifier through a first resistor; and the compensation signal output end of the generating subunit is connected with the inverting input end of the first operational amplifier through a second resistor.
The detection subunit includes:
the first input end is grounded through the third resistor and the fourth resistor in sequence, and the second input end is grounded; the connection point of the third resistor and the fourth resistor is connected with the base electrode of the first triode, the emitter electrode of the first triode is grounded, the collector electrode of the first triode is connected with the first output end of the detection subunit, and the second output end of the detection subunit is grounded;
the generating subunit includes:
the first input end of the generating subunit is connected with the first output end of the detecting subunit, and the second input end of the generating subunit is connected with the second output end of the detecting subunit;
the first input end of the generating subunit is connected with a power supply voltage through a fifth resistor and is grounded through a second capacitor; the first input end of the generating subunit is grounded through a first diode and a third capacitor in sequence; the cathode of the first diode is connected with the base electrode of the second triode, the emitter of the second triode is grounded through the sixth resistor, and the collector of the second triode is connected with the power supply voltage; and the emitter of the second triode is connected with the compensation signal output end of the generating subunit through the second diode and the seventh resistor in sequence.
The detection subunit includes: the first input end is grounded through the third resistor and the fourth resistor in sequence, and the second input end is grounded; the connection point of the third resistor and the fourth resistor is connected with the base electrode of the first triode, the emitter electrode of the first triode is grounded, the collector electrode of the first triode is connected with the first output end of the detection subunit, and the second output end of the detection subunit is grounded;
the generating subunit includes:
the first input end of the generating subunit is connected with the first output end of the detecting subunit, and the second input end of the generating subunit is connected with the second output end of the detecting subunit;
the first input end of the generating subunit is connected with a power supply voltage through a fifth resistor and is grounded through a second capacitor; the first input end of the generating subunit is grounded through a first diode and a third capacitor in sequence; the cathode of the first diode is connected with the base electrode of the second triode, the emitter of the second triode is grounded through the sixth resistor, and the collector of the second triode is connected with the power supply voltage; the emitter of the second triode is used as a compensation signal output end of the generating subunit.
The embodiment of the invention also provides a signal control method, which is applied to a PFC circuit, wherein the input end of the PFC circuit receives chopped wave voltage; the PFC circuit includes: a main switching tube and a Ton control unit; the control signal of the Ton control unit is positively correlated with the chopping angle of the chopping voltage within the range of being less than or equal to the maximum value;
the method comprises the following steps:
detecting a chopping angle of a chopping voltage;
generating a compensation signal with positive correlation between the amplitude and the chopping angle;
and controlling the comparison signal of the Ton control unit according to the compensation signal, so that the control signals corresponding to the equal chopping angles are increased within the range that the control signals are less than or equal to the maximum value.
Controlling the comparison signal of the Ton control unit according to the compensation signal comprises:
the compensation signal is superimposed on the comparison signal of the Ton control unit.
The embodiment of the invention also provides a load driving circuit which comprises the PFC circuit.
The technical effect analysis of the technical scheme is as follows:
a detection compensation unit is added in the PFC circuit, and detects the chopping angle of the chopping voltage to generate a compensation signal with the amplitude value positively correlated with the chopping angle; controlling a comparison signal of a Ton control unit according to the compensation signal; therefore, the comparison signal in the Ton control unit is changed into a new comparison signal, so that the conduction time Ton of the main switching tube is temporarily reduced, and then the current control unit maintains the conduction time Ton and the output current of the PFC circuit unchanged through closed-loop adjustment, so that the control signals corresponding to the same chopping angle are increased, the control signal value is increased under the closed-loop state of the current control unit, and the invalid adjustment process in the dimming process is also shortened.
Drawings
FIG. 1 is a schematic diagram of an implementation of a chopper dimmer of the prior art;
FIG. 2 is a schematic diagram of a chopper voltage of the prior art;
FIG. 3 is a schematic diagram of a prior art light source load driving circuit;
FIG. 4 is a prior art signal relationship diagram;
fig. 5 is a schematic circuit diagram of a PFC circuit according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of an implementation structure of a detection compensation unit according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a first PFC circuit according to the present invention;
FIG. 8 is a signal relationship diagram according to an embodiment of the present invention;
fig. 9 is a schematic diagram of a second PFC circuit according to the present invention;
FIG. 10 is a signal relationship diagram according to an embodiment of the present invention;
FIG. 11 is a schematic diagram of a circuit implementation structure of a detecting subunit and a generating subunit according to an embodiment of the present invention;
fig. 12 is a flowchart illustrating a signal control method according to an embodiment of the invention.
Detailed Description
In the process of changing the chopping angle alpha, the chopping dimmer can realize the dimming function only when the current control unit is in an open-loop state. In the process that the chopping dimmer regulates the chopping angle alpha of the chopping voltage from zero to the critical value alpha x, the output current Io of the PFC circuit is kept unchanged, so that the dimming is meaningless, and the regulation process at the stage is an invalid regulation process for a user.
The inventors have found through extensive research that decreasing the critical value α x, i.e., decreasing the maximum chopping angle of the closed loop state, can shorten the time that the current control unit is in the closed loop state, thereby shortening the invalid adjustment process. However, since the current control unit operates in the closed loop state, directly raising the value of the control signal Vr temporarily raises the on-time Ton of the main switching tube S1, raises the output current Io of the PFC circuit, raises the output current sampling value of the current control unit, and lowers the control signal Vr output by the current control unit, and therefore, directly raising the control signal Vr cannot bring the chopping angle α x into the critical state at a small value.
Therefore, embodiments of the present invention provide a PFC circuit, a load driving circuit, and a signal control method, which can increase control signals corresponding to equal chopping angles in a closed-loop process, that is, in a range where the control signals are smaller than or equal to a maximum value, so as to reduce a critical value α x and achieve the purpose of shortening an invalid adjustment process in a dimming process.
The following describes in detail the implementation of the PFC circuit, the load driving circuit, and the current control method according to the embodiments of the present invention with reference to the drawings.
Fig. 5 is a schematic diagram of a PFC circuit according to an embodiment of the present invention, where:
the input end of the PFC circuit receives a chopped wave voltage, namely the input voltage Vin; the PFC circuit includes: a main switching tube S1 (not shown in fig. 5) and Ton control unit 510; the Ton control unit 510 outputs a control signal Vr which is positively correlated with the chopping angle of the chopping voltage within a range less than or equal to a maximum value; (wherein, the positive correlation means that the larger the chopping angle alpha is, the larger the control signal Vr is, the smaller the chopping angle alpha is, the smaller the control signal Vr is.)
The PFC circuit further includes:
a detection compensation unit 520, configured to detect a chopping angle of the chopping voltage and generate a compensation signal with an amplitude positively correlated to the chopping angle; and controlling the comparison signal of the Ton control unit according to the compensation signal, so that the control signals corresponding to the equal chopping angles are increased within the range that the control signals are less than or equal to the maximum value. That is, the control signal output by the current control circuit is made to rise with the chopping angle unchanged.
Furthermore, a new comparison signal will be obtained by the control of the detection compensation unit 520 on the comparison signal, and the Ton control unit will compare the new comparison signal with the control signal according to the new comparison signal to determine the on-time Ton of the main switch tube S1.
Here, the positive correlation means that: the larger the chopping angle, the larger the amplitude of the compensation signal, and the smaller the chopping angle, the smaller the amplitude of the compensation signal.
Preferably, as shown in fig. 5, the PFC circuit and the first rectifier may constitute a load driving circuit, and the first rectifier is configured to rectify the chopped voltage output by the chopping dimmer, so as to obtain the input voltage Vin of the PFC circuit.
As shown in fig. 5, two input terminals of the detection compensation unit 520 may be connected to two output terminals of the first rectifier, and perform detection of the chopping angle on the chopped voltage output by the first rectifier;
or, a second rectifier may be additionally provided, and the second rectifier rectifies the chopped wave voltage output by the chopping dimmer; and two input terminals of the detection compensation unit 520 are connected to two output terminals of the second rectifier, so as to detect the chopping angle of the chopped voltage output by the second rectifier.
In the embodiment of the present invention, the chopping voltage output by the chopping dimmer may be a leading-edge chopping voltage, a trailing-edge chopping voltage, or a leading-trailing-edge chopping voltage, and the like, which is not limited herein.
As shown in fig. 6, the detection compensation unit 520 may be implemented by the following structure:
a detection subunit 610 for detecting a chopping angle of the chopping voltage;
a generating subunit 620, configured to generate a compensation signal with an amplitude value positively correlated to the chopping angle;
a control subunit 630, configured to control the comparison signal of the Ton control unit according to the compensation signal.
Preferably, the control subunit 630 may be specifically configured to: the compensation signal is superimposed on the comparison signal of the Ton control unit.
Taking the load driving circuit shown in fig. 3 as an example, the PFC circuit and the load driving circuit according to the embodiment of the present invention will be described in more detail.
In a specific embodiment, the compensation signal may be a current signal; the comparison signal may be a sawtooth signal; at this time, as shown in fig. 7:
the Ton control unit includes: the output end of the constant current source Id is grounded through a first capacitor C1 and a second switch tube S2 respectively, the ungrounded end of a first capacitor C1 serves as a comparison signal output end and outputs a comparison signal Vp, and the ungrounded end of a first capacitor C1 is connected with the inverting input end of a first operational amplifier A1; the non-inverting input terminal of the first operational amplifier a1 is used for receiving the control signal Vr, i.e. is connected to the output terminal of the current control unit;
when the control subunit is not included, the operating principle of the Ton control unit is as follows: when the second switch tube S2 is turned on, the voltage across the first capacitor C1 is zero, that is, the comparison signal Vp is zero, when the second switch tube S2 is turned off, the constant current source Id charges the first capacitor C1, the voltage across the first capacitor C1 increases from zero, that is, the comparison signal Vp increases from zero, and when the comparison signal Vp increases to be equal to the control signal Vr, the second switch tube S2 is turned on, so that the comparison signal Vp output by the ungrounded end of the first capacitor C1 is a sawtooth wave.
As shown in fig. 7, the control subunit 630 includes: two output terminals of the generating subunit 620 are respectively connected to two terminals of the first capacitor C1. Therefore, the compensation signal generated by the generating sub-unit 620 is converted into a sawtooth wave signal in the Ton control unit, and is in phase with the comparison signal, specifically: by connecting the two output terminals of the generating subunit 620 to the two ends of the first capacitor C1 in parallel, the voltage generated by the compensation signal output by the generating subunit 620 at the two ends of the first capacitor C1 and the generation principle of the comparison signal Vp are the same, that is, both are controlled by the second switching tube S2, so that the voltage signal generated by the compensation signal on the first capacitor C1 and the comparison signal Vp are in the same phase, the voltage on the first capacitor C1 is the superposition of the two, and the slope of the superposed voltage Vp' is greater than the slope of the comparison signal Vp, refer to fig. 8.
In the circuit configuration shown in fig. 7, as shown in fig. 8, the compensation signal I α (not shown) is converted into a voltage signal at the first capacitor C1 of the Ton control unit as a sawtooth wave signal V α, the dotted line is a comparison signal Vp, the sawtooth wave signal V α generated by the compensation signal I α is superimposed with the comparison signal Vp to obtain a new comparison signal Vp '═ Vp + V α, the waveform is shown by the solid line in the figure, and the new comparison signal Vp' is input to the inverting input terminal of the first operational amplifier instead of the original comparison signal Vp.
The new comparison signal Vp 'is compared with the current control signal Vr to obtain an on-time Ton', which is smaller than the on-time Ton corresponding to the comparison signal Vp, and at this time, because the current Ton 'is decreased, the output current Io of the PFC circuit (i.e., the load driving circuit) is decreased, the sampling signal obtained by sampling the output current Io by the current control unit is decreased, the control signal Vr output by the current control unit is increased, so that the on-time Ton' of the main switching tube S1 is increased, the on-time of the main switching tube is maintained, and the output current Io of the PFC circuit (i.e., the load driving circuit) is maintained.
Therefore, when the chopping angle α is unchanged, and the comparison signal changes from Vp to a new comparison signal Vp', and then is input to the Ton control unit, the dynamic adjustment of the current control unit finally keeps the on-time Ton of the main switching tube S1 unchanged, and the output current Io of the PFC circuit unchanged, so that the control signal Vr is increased. As the chopping angle α increases, the control signal Vr also increases, and when Vr increases to Vr-max (corresponding to a chopping angle α x), the current control unit is about to enter the open-loop state. That is, in the range where the control signal Vr is smaller than or equal to the maximum value Vr-max, the control signal Vr corresponding to the same chopping angle α is increased, so that the control signal Vr is closer to the critical state of the closed loop and the open loop under the condition that the chopping angle is not changed, the critical value α x is reduced, and the invalid adjustment process in the dimming process is shortened.
In another embodiment, the compensation signal V α may be a voltage signal; the comparison signal Vp may be a sawtooth signal, and the compensation signal va may be a level signal; at this time, as shown in fig. 9:
the Ton control unit includes: the non-inverting input terminal of the first operational amplifier A1 is used for receiving a control signal;
the control subunit 630 includes:
the first input end is used for receiving the comparison signal Vp, and is also connected with the inverting input end of the first operational amplifier A1 through a first resistor R1; the compensation signal output terminal of the generation subunit 620 is connected to the inverting input terminal of the first operational amplifier a1 through a second resistor R2.
The comparison signal Vp may be obtained by a comparison signal generation subunit as shown in fig. 7, specifically, the comparison signal generation subunit includes: the output end of the constant current source Id is grounded through the first capacitor C1 and the second switch tube S2, respectively, and the ungrounded end of the first capacitor C1 serves as the comparison signal output end of the comparison signal generation subunit to output the comparison signal Vp.
In fig. 9, the compensation signal V α in the form of a voltage signal and the comparison signal Vp are superimposed by the first resistor R1 and the second resistor R2 to obtain a new superimposed comparison signal Vp', which is input to the inverting input terminal of the first operational amplifier in the Ton control unit. The dc offset voltage of the new comparison signal Vp' is higher than the dc offset voltage of the original comparison signal Vp, as shown in fig. 10.
In fig. 10, the compensation signal V α is a level signal, the dotted line is a comparison signal Vp, and after the compensation signal V α and the comparison signal Vp are superimposed, a new comparison signal Vp' is Vp + V α.
The first operational amplifier compares the new comparison signal Vp 'with the current control signal Vr to obtain a conduction time Ton' of the main switching tube, which is smaller than the conduction time Ton corresponding to the original comparison signal Vp, at this time, because the conduction time Ton 'of the current main switching tube is smaller, the output current Io of the PFC circuit is smaller, the sampling signal obtained by sampling the output current Io by the current control unit is smaller, the output control signal Vr is increased to increase the conduction time Ton', so that the output current Io of the PFC circuit is maintained unchanged.
Therefore, under the condition that the chopping angle alpha is not changed, after the comparison signal is changed from Vp to Vp', the dynamic adjustment of the current control unit finally enables the conduction time Ton of the main switching tube to be unchanged, the output current Io of the PFC circuit to be unchanged, and the control signal Vr to be increased. With the increase of the chopping angle alpha, the control signal Vr also increases, and when Vr increases to Vr-max, the current control unit is about to enter an open-loop state. That is, in the range where the control signal Vr is smaller than or equal to the maximum value Vr-max, the control signal Vr corresponding to the same chopping angle α is increased, so that the control signal Vr is closer to the critical state of the closed loop and the open loop under the condition that the chopping angle is not changed, the critical value α x is reduced, and the invalid adjustment process in the dimming process is shortened.
The compensation signal in the embodiment of the present invention may be obtained by the circuit structure shown in fig. 11, that is, the detection subunit 610 and the generation subunit 620 in the detection compensation unit 520 may be obtained by the circuit structure shown in fig. 11. Referring to fig. 11:
the detection subunit 610 includes:
the first input terminal of the detection subunit 610 is grounded through the third resistor R3 and the fourth resistor R4 in sequence, and the second input terminal of the detection subunit is grounded (the "ground" referred to herein is the negative output terminal of the rectifier bridge in the PFC circuit); the connection point of the third resistor R3 and the fourth resistor R4 is connected with the base electrode of the first triode Q1, the emitter electrode of the first triode Q1 is grounded, the collector electrode of the first triode Q1 is connected with the first output end of the detection subunit, and the second output end of the detection subunit is grounded;
the generation subunit 620 includes:
a first input terminal of the generating subunit 620 is connected to a first output terminal of the detecting subunit 610, and a second input terminal of the generating subunit 620 is connected to a second output terminal of the detecting subunit 610;
the first input terminal of the generating subunit 620 is connected to the power supply voltage Vcc through a fifth resistor R5, and is also grounded through a second capacitor C2; the first input terminal of the generating subunit 620 is grounded through the first diode D1 and the third capacitor C3 in sequence; the cathode of the first diode D1 is connected with the base of the second triode Q2, the emitter of the second triode Q2 is grounded through a sixth resistor R6, and the collector of the second triode Q2 is connected with the power supply voltage Vcc;
at this time, two ends of a sixth resistor R6 in the generating subunit are used as two output ends of the generating subunit, and the output compensation signal is a voltage signal;
alternatively, as shown in fig. 11, the emitter of the second transistor Q2 may be connected to one end of a series-connected branch, which is the second diode D2 and the seventh resistor R7, in this case, the other end of the series-connected branch and the ground end of the sixth resistor R6 may also be used as two output ends of the generating subunit, and the output compensation signal is a current signal.
In the circuit shown in fig. 11, the third resistor R3 and the fourth resistor R4 are voltage dividing resistors, the input rectified chopped voltage is sampled, the first transistor Q1 detects a low level signal in the chopped voltage, and a sawtooth voltage, i.e., a voltage across the second capacitor C2, is output, the peak value of the sawtooth voltage increases with the increase of the chopping angle, the peak value of the sawtooth voltage is held by the first diode D1 and the third capacitor C3, a level signal is obtained on the third capacitor C3, the value of the level signal increases with the increase of the chopping angle, and the voltage signal across the sixth resistor R6 also increases with the increase of the chopping angle through the follower circuit of the second transistor Q2. The value of the current signal output through the second diode D2 and the seventh resistor R7 also increases as the chopping angle increases.
The PFC circuit according to the above-described embodiment of the present invention may be directly used as a load driving circuit, or may be combined with a circuit such as a first rectifier to form a load driving circuit.
Corresponding to the PFC circuit and the load driving circuit, the embodiment of the present invention provides a signal control method, which may be applied to a PFC circuit, an input terminal of which receives a chopped voltage; the PFC circuit includes: a main switching tube and a ton control unit; the control signal of the Ton control unit is positively correlated with the chopping angle of the chopping voltage within the range of being less than or equal to the maximum value; (wherein, the positive correlation means that the larger the chopping angle is, the larger the control signal Vr is, and the smaller the chopping angle is, the smaller the control signal Vr is.)
As shown in fig. 12, the method includes:
step 1201: detecting a chopping angle of a chopping voltage;
step 1202: generating a compensation signal with positive correlation between the amplitude and the chopping angle;
step 1203: and controlling the comparison signal of the Ton control unit according to the compensation signal, so that the control signals corresponding to the equal chopping angles are increased within the range that the control signals are less than or equal to the maximum value.
Preferably, the controlling the comparison signal of the Ton control unit according to the compensation signal may include: the compensation signal is superimposed on the comparison signal of the Ton control unit.
Furthermore, in step 1203, a new comparison signal is obtained through the control; then, the Ton control unit will compare the new comparison signal with the control signal according to the new comparison signal, and determine the on-time Ton of the main switch tube S1.
Based on the above embodiment, the chopping angle of the chopping voltage is detected, and the compensation signal with positive correlation between the amplitude and the chopping angle is generated; and controlling the comparison signal of the Ton control unit according to the compensation signal. Therefore, a comparison signal in the Ton control unit is changed into a new comparison signal, the Ton control unit compares the new comparison signal with the control signal to determine the conduction time Ton of the main switching tube, the conduction time Ton of the main switching tube is temporarily reduced due to the rising of the comparison signal, and then the current control unit maintains the conduction time Ton and the output current of the PFC circuit unchanged through closed-loop adjustment, so that the control signal corresponding to the same chopping angle is raised, the effect of raising the value of the control signal in the closed-loop state of the current control unit is realized, the critical value alpha x is reduced, and the aim of shortening the invalid adjustment process in the dimming process is fulfilled. .
Those skilled in the art will appreciate that the processes of implementing the methods of the above embodiments may be implemented by hardware associated with program instructions, and the program may be stored in a readable storage medium, and when executed, the program performs the corresponding steps of the above methods. The storage medium may be as follows: ROM/RAM, magnetic disk, optical disk, etc.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A PFC circuit, an input of the PFC circuit receiving a chopped voltage, the PFC circuit comprising: a main switching tube and a Ton control unit; the control signal of the Ton control unit is positively correlated with the chopping angle of the chopping voltage within the range of being less than or equal to the maximum value;
the PFC circuit further includes:
the detection compensation unit is used for detecting a chopping angle of the chopping voltage and generating a compensation signal with positive correlation between the amplitude and the chopping angle; and controlling the comparison signal of the Ton control unit according to the compensation signal, so that the control signals corresponding to the equal chopping angles are increased within the range that the control signals are less than or equal to the maximum value.
2. The circuit of claim 1, wherein the detection compensation unit comprises:
a detection subunit for detecting a chopping angle of the chopping voltage;
the generating subunit is used for generating a compensation signal with positive correlation between the amplitude and the chopping angle;
and the control subunit is used for controlling the comparison signal of the Ton control unit according to the compensation signal.
3. The circuit according to claim 2, wherein the control subunit is specifically configured to: the compensation signal is superimposed on the comparison signal of the Ton control unit.
4. The circuit of claim 3, wherein the compensation signal is a current signal; the comparison signal is a sawtooth wave signal;
the Ton control unit includes: the constant current source is grounded through a first capacitor and a second switching tube respectively, and the ungrounded first end of the first capacitor is connected with the inverting input end of the first operational amplifier; the positive phase input end of the first operational amplifier is used for receiving a control signal;
the control subunit includes: two output ends of the generating subunit are respectively connected with two ends of the first capacitor.
5. The circuit of claim 3, wherein the compensation signal is a voltage signal; the comparison signal is a sawtooth wave signal;
the Ton control unit includes: the positive phase input end of the first operational amplifier is used for receiving a control signal;
the control subunit includes:
the first input end is used for receiving a comparison signal and is also connected with the inverting input end of the first operational amplifier through a first resistor; and the compensation signal output end of the generating subunit is connected with the inverting input end of the first operational amplifier through a second resistor.
6. The circuit of claim 4, wherein the detection subunit comprises:
the first input end is grounded through the third resistor and the fourth resistor in sequence, and the second input end is grounded; the connection point of the third resistor and the fourth resistor is connected with the base electrode of the first triode, the emitting electrode of the first triode is grounded, the collecting electrode is connected with the first output end of the detection subunit, and the second output end of the detection subunit is grounded;
the generating subunit includes:
the first input end of the generating subunit is connected with the first output end of the detecting subunit, and the second input end of the generating subunit is connected with the second output end of the detecting subunit;
the first input end of the generating subunit is connected with a power supply voltage through a fifth resistor and is grounded through a second capacitor; the first input end of the generating subunit is grounded through a first diode and a third capacitor in sequence; the cathode of the first diode is connected with the base electrode of the second triode, the emitting electrode of the second triode is grounded through the sixth resistor, and the collector electrode of the second triode is connected with the power supply voltage; and an emitter of the second triode is connected with a compensation signal output end of the generating subunit through the second diode and the seventh resistor in sequence.
7. The circuit of claim 5, wherein the detection subunit comprises: the first input end is grounded through the third resistor and the fourth resistor in sequence, and the second input end is grounded; the connection point of the third resistor and the fourth resistor is connected with the base electrode of the first triode, the emitting electrode of the first triode is grounded, the collecting electrode is connected with the first output end of the detection subunit, and the second output end of the detection subunit is grounded;
the generating subunit includes:
the first input end of the generating subunit is connected with the first output end of the detecting subunit, and the second input end of the generating subunit is connected with the second output end of the detecting subunit;
the first input end of the generating subunit is connected with a power supply voltage through a fifth resistor and is grounded through a second capacitor; the first input end of the generating subunit is grounded through a first diode and a third capacitor in sequence; the cathode of the first diode is connected with the base electrode of the second triode, the emitting electrode of the second triode is grounded through the sixth resistor, and the collector electrode of the second triode is connected with the power supply voltage; and the emitter of the second triode is used as a compensation signal output end of the generating subunit.
8. A signal control method is characterized in that the method is applied to a PFC circuit, and an input end of the PFC circuit receives chopped wave voltage; the PFC circuit includes: a main switching tube and a Ton control unit; the control signal of the Ton control unit is positively correlated with the chopping angle of the chopping voltage within the range of being less than or equal to the maximum value;
the method comprises the following steps:
detecting a chopping angle of a chopping voltage;
generating a compensation signal with positive correlation between the amplitude and the chopping angle;
and controlling the comparison signal of the Ton control unit according to the compensation signal, so that the control signals corresponding to the equal chopping angles are increased within the range that the control signals are less than or equal to the maximum value.
9. The method of claim 8, wherein controlling the comparison signal of the Ton control unit according to the compensation signal comprises:
the compensation signal is superimposed on the comparison signal of the Ton control unit.
10. A load driving circuit comprising the PFC circuit according to any one of claims 1 to 7.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
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| CN201110376593.8A CN103138556B (en) | 2011-11-23 | 2011-11-23 | Pfc circuit, load driving circuits and signal control method |
| PCT/CN2012/078153 WO2013075504A1 (en) | 2011-11-23 | 2012-07-04 | Pfc circuit, load drive circuit and signal control method |
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| CN201110376593.8A CN103138556B (en) | 2011-11-23 | 2011-11-23 | Pfc circuit, load driving circuits and signal control method |
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| CN103138556B true CN103138556B (en) | 2015-08-19 |
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| CN104219855B (en) * | 2014-09-28 | 2017-03-29 | 广东工业大学 | Based on APFC without stroboscopic LED constant current drive control circuit |
| CN104797041A (en) * | 2015-03-30 | 2015-07-22 | 成都颉隆科技有限公司 | Bootstrap trigger type smart grid frequency conversion energy-saving control system |
| CN104780670A (en) * | 2015-03-30 | 2015-07-15 | 成都颉隆科技有限公司 | Variable-frequency and energy-saving control system for smart power grid |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1106175A (en) * | 1993-09-07 | 1995-08-02 | 株式会社东芝 | Power conversion system |
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| CN101686587B (en) * | 2008-09-25 | 2015-01-28 | 皇家飞利浦电子股份有限公司 | Drive for providing variable power for LED array |
| TWI405502B (en) * | 2009-08-13 | 2013-08-11 | Novatek Microelectronics Corp | Dimmer circuit of light emitted diode and isolated voltage generator and dimmer method thereof |
| US8242766B2 (en) * | 2010-04-20 | 2012-08-14 | Power Integrations, Inc. | Dimming control for a switching power supply |
| TW201141303A (en) * | 2010-05-07 | 2011-11-16 | Light Engine Ltd | Triac dimmable power supply unit for LED |
| CN201995174U (en) * | 2011-01-28 | 2011-09-28 | 英飞特电子（杭州）有限公司 | Back-porch small-phase-angle light dimming circuit |
| CN102143638B (en) * | 2011-04-08 | 2013-07-24 | 矽力杰半导体技术(杭州)有限公司 | Silicon-controlled light-dimming circuit, light-dimming method and LED (light-emitting diode) driver applying the same |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1106175A (en) * | 1993-09-07 | 1995-08-02 | 株式会社东芝 | Power conversion system |
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