CN112688553A - Boost-PFC control circuit and control method thereof - Google Patents
Boost-PFC control circuit and control method thereof Download PDFInfo
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Abstract
The invention discloses a Boost-PFC control circuit and a control method thereof, wherein the Boost-PFC control circuit comprises a PFC main circuit, a control module, a PWM module and a period current-sharing module, wherein the PFC main circuit comprises a first PFC branch and a second PFC branch; the control module outputs a control signal obtained by calculation according to the input voltage, the input current and the output voltage of the PFC main circuit to the PWM module; the period current-sharing module outputs a regulating signal to the PWM module according to the input current and the first branch current; the PWM module outputs a first driving signal to the first PFC branch after performing current-sharing regulation on the control signal according to the regulating signal, and outputs a second driving signal to the second PFC branch; the invention can effectively solve the problem of current imbalance between the parallel branches by arranging the periodic current-sharing module.
Description
Technical Field
The invention relates to the technical field of electronic equipment, in particular to a Boost-PFC control circuit and a control method thereof.
Background
In a Boost-PFC (Power Factor Correction) converter, since parasitic parameters of devices of two parallel branches cannot be completely the same, there is a deviation in current of the two branches. When the inverter is operated in a non-current-sharing state for a long time, the power factor is reduced, and the service life of the branch with large current is shortened, so that the efficiency and the service life of the whole inverter are influenced.
Thus, the prior art has yet to be improved and enhanced.
Disclosure of Invention
The invention aims to provide a Boost-PFC control circuit and a control method thereof, which can effectively solve the problem of current imbalance among parallel branches and further improve the reliability of the whole circuit.
In order to achieve the purpose, the invention adopts the following technical scheme:
a Boost-PFC control circuit comprises a PFC main circuit, a control module, a PWM module and a period current-sharing module, wherein the PFC main circuit comprises a first PFC branch and a second PFC branch which are connected in parallel; the control module is respectively connected with the input end and the output end of the PFC main circuit and the PWM module, the PWM module is respectively connected with the first PFC branch, the second PFC branch and the period current-sharing module, and the period current-sharing module is respectively connected with the input end of the PFC main circuit and the first PFC branch;
the control module is used for outputting a control signal obtained by calculation according to the input voltage, the input current and the output voltage of the PFC main circuit to the PWM module;
the period current equalizing module is used for calculating to obtain a difference signal according to the input current and the first branch current and outputting an adjusting signal to the PWM module according to the difference signal;
the PWM module is used for outputting a first driving signal to the first PFC branch after the control signal is subjected to current sharing regulation according to the regulation signal and outputting a second driving signal to the second PFC branch; the phase difference between the first driving signal and the second driving signal is a preset phase angle.
In the Boost-PFC control circuit, the period current equalizing module comprises a difference value calculating unit and an adjusting unit; the difference value calculating unit is respectively connected with the first PFC branch, the input end of the PFC main circuit and the adjusting unit, and the adjusting unit is connected with the PWM module;
the difference value calculating unit is used for calculating and outputting a first current effective value and a second current effective value according to the input current and the first branch current, and outputting a difference value signal to the adjusting unit according to the first current effective value and the second current effective value;
the adjusting unit is used for outputting an adjusting signal to the PWM module according to the difference signal.
In the Boost-PFC control circuit, the difference value calculating unit comprises a first period effective value calculator, a second period effective value calculator, a first subtracter, a first amplifier, a second subtracter and a third subtracter;
the first period effective value calculator is used for outputting a first current effective value calculated according to the first branch current to the first subtracter and the first amplifier;
the second period effective value calculator is used for respectively outputting the total current effective values calculated according to the input current to the first subtracter, the second subtracter and the third subtracter;
the first amplifier amplifies the first current effective value and outputs the amplified first current effective value to the second subtractor;
the first subtracter is used for outputting a second current effective value obtained through calculation according to the total current effective value and the first current effective value to the second amplifier;
the second amplifier is used for amplifying the second current effective value and outputting the amplified second current effective value to the second subtracter;
the second subtracter is used for comparing the amplified first current effective value with the total current effective value and outputting a first difference signal to the adjusting unit;
and the third subtracter is used for comparing the amplified second current effective value with the total current effective value and outputting a second difference signal to the adjusting unit.
In the Boost-PFC control circuit, the difference value calculating unit comprises a third period effective value calculator, a fourth subtracter, a fifth subtracter and a sixth subtracter;
the third period effective value calculator is configured to output a first current effective value calculated from the first branch current to the fourth subtractor and the fifth subtractor;
the fourth period effective value calculator is used for outputting a total current effective value calculated according to the input current to the fourth subtracter;
the fourth subtracter is used for outputting a second current effective value to the fifth subtracter according to the first current effective value and the total current effective value;
the fifth subtractor is configured to output a difference current effective value obtained by subtracting the first current effective value and the second current effective value to the sixth subtractor;
and the sixth subtracter is used for comparing the difference current effective value with a reference value and outputting a difference signal to the adjusting unit.
In the Boost-PFC control circuit, the adjusting unit comprises a first PI controller, a second PI controller, a first post-replacement calculator and a second post-replacement calculator;
the first PI controller is used for adjusting the first difference signal and outputting a first adjusting signal to the first post-displacement calculator;
the first post-displacement calculator is used for converting the first adjusting signal and outputting the converted first adjusting signal to the PWM module;
the second PI controller is used for adjusting the second difference signal and outputting a second adjusting signal to the second post-displacement calculator;
and the second post-displacement calculator is used for converting the second adjusting signal and outputting the converted second adjusting signal to the PWM module.
In the Boost-PFC control circuit, the adjusting unit comprises a third PI controller and a third post-displacement calculator;
the third PI controller is used for adjusting the difference signal and outputting the adjusting signal to the third post-displacement calculator;
and the third post-displacement calculator is used for converting the adjusting signal and outputting the converted adjusting signal to the PWM module.
In the Boost-PFC control circuit, the control module comprises a sampling unit, a control unit and a feedforward unit;
the sampling unit is used for sampling the input voltage, the input current and the output voltage of the PFC main circuit, respectively outputting the sampled input voltage to the control unit and the feedforward unit, and outputting the sampled output voltage and the sampled input current to the control unit;
the feedforward unit is used for outputting feedforward voltage obtained according to the sampled input voltage and a first duty ratio signal to the control unit;
the control unit is used for outputting a control signal obtained by calculation according to the sampled input voltage, the sampled output voltage, the sampled input current, the feedforward voltage and the first duty ratio signal to the PWM module.
In the Boost-PFC control circuit, the feedforward unit comprises a voltage feedforward loop controller and a duty ratio feedforward loop controller;
the voltage feedforward loop controller is used for outputting feedforward voltage to the control unit according to the sampled input voltage;
the duty ratio feedforward loop controller is used for outputting the first duty ratio signal to the control unit according to the sampled input voltage and the reference voltage.
In the Boost-PFC control circuit, the control unit comprises a voltage loop controller, a multiplier, a current loop controller and an adder;
the voltage ring controller is used for outputting a difference voltage to the multiplier after the difference is made between the reference voltage and the sampled output voltage;
the multiplier is used for multiplying the sampled input voltage, the difference voltage and the feedforward voltage and then outputting a reference current to the current loop controller;
the current loop controller is used for outputting a second duty ratio signal to the adder after the difference is made between the reference current and the sampled input current;
the adder is used for adding the first duty ratio signal and the second duty ratio signal and then outputting the control signal to the PWM module.
A control method based on the Boost-PFC control circuit comprises the following steps:
the control module outputs a control signal obtained by calculation according to the input voltage, the input current and the output voltage of the PFC main circuit to the PWM module;
the period current equalizing module calculates to obtain a difference signal according to the input current and a first branch current of a first PFC branch, and outputs an adjusting signal to the PWM module according to the difference signal;
the PWM module adjusts the control signal according to the adjusting signal, outputs a first driving signal to the first PFC branch and outputs a second driving signal to the second PFC branch; the phase difference between the first driving signal and the second driving signal is a preset phase angle.
Compared with the prior art, the invention provides a Boost-PFC control circuit and a control method thereof, wherein the Boost-PFC control circuit comprises a PFC main circuit, a control module, a PWM module and a period current-sharing module, and the PFC main circuit comprises a first PFC branch and a second PFC branch which are connected in parallel; the control module is used for outputting a control signal obtained by calculation according to the input voltage, the input current and the output voltage of the PFC main circuit to the PWM module; the period current equalizing module is used for calculating to obtain a difference signal according to the input current and the first branch current and outputting an adjusting signal to the PWM module according to the difference signal; the PWM module is used for outputting a first driving signal to the first PFC branch after the control signal is subjected to current sharing regulation according to the regulation signal and outputting a second driving signal to the second PFC branch; the invention can effectively solve the problem of current imbalance between the parallel branches by arranging the periodic current-sharing module, thereby improving the reliability of the whole circuit.
Drawings
Fig. 1 is a block diagram of a Boost-PFC control circuit according to the present invention;
fig. 2 is a schematic circuit diagram of a first embodiment of a Boost-PFC control circuit according to the present invention;
fig. 3 is a schematic diagram of a second embodiment of a Boost-PFC control circuit according to the present invention;
fig. 4 is a schematic circuit diagram of a main PFC circuit in the Boost-PFC control circuit according to the present invention;
fig. 5 is a flowchart of a control method of the Boost-PFC control circuit according to the present invention.
Detailed Description
The invention aims to provide a Boost-PFC control circuit and a control method thereof, which can effectively solve the problem of current imbalance among parallel branches and further improve the reliability of the whole circuit.
In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1 and fig. 2, a Boost-PFC (Power Factor Correction)) control circuit according to the present invention includes a main PFC circuit 10, a control module 20, a PWM (Pulse Width Modulation) module 30, and a period current equalizing module 40, where the main PFC circuit 10 includes a first PFC branch 11 and a second PFC branch 12 connected in parallel; the control module 20 is respectively connected to an input end and an output end of the main PFC circuit 10 and the PWM module 30, the PWM module 30 is respectively connected to the first PFC branch 11, the second PFC branch 12 and the period current equalizing module 40, and the period current equalizing module 40 is respectively connected to the input end of the main PFC circuit 10 and the first PFC branch 11.
The control module 20 is configured to output a control signal, which is calculated according to an input voltage (Vrect in this embodiment), an input current (Irect in this embodiment) and an output voltage (Vout in this embodiment) of the PFC main circuit 10, to the PWM module 30; the period current equalizing module 40 is configured to calculate a difference signal according to the input current and the first branch current (in this embodiment, Ig1), and output an adjustment signal to the PWM module 30 according to the difference signal; the PWM module 30 is configured to output a first driving signal to the first PFC branch 11 after performing current-sharing adjustment on the control signal according to the adjustment signal, and output a second driving signal to the second PFC branch 12; the phase difference of the first driving signal and the second driving signal is a preset phase angle; according to the invention, the periodic current equalizing module 40 is arranged to realize the current equalizing effect in a period, so that the problem of current imbalance among the parallel branches can be effectively solved, and the reliability of the whole circuit is further improved.
Further, the period current equalizing module 40 includes a difference value calculating unit 41 and an adjusting unit 42; the difference calculating unit 41 is respectively connected to the first PFC branch 11, the input end of the PFC main circuit 10, and the adjusting unit 42 is connected to the PWM module 30.
The difference calculating unit 41 is configured to calculate and output a first current effective value (I1 rms in this embodiment) and a second current effective value (I2 rms in this embodiment) according to the input current and the first branch current, and output a difference signal to the adjusting unit 42 according to the first current effective value and the second current effective value, where the adjusting unit 42 is configured to output an adjusting signal to the PWM module 30 according to the difference signal, and further the PWM module 30 controls the first PFC branch 11 and the second PFC branch 12 to work; therefore, after the period current-sharing module 40 is arranged to sample the input current and the first branch current, the period effective values in the two branches are calculated, the period branch current sharing is realized, the influence of single sampling on control can be reduced, the anti-interference capability on external disturbance such as electromagnetic noise is enhanced, and the reliability of the control circuit is improved; and low-voltage end sampling is adopted, so that the cost and hardware design difficulty can be reduced.
Further, with reference to fig. 1, in the first embodiment of the present invention, the difference calculating unit 41 includes a first period effective value calculator 411, a second period effective value calculator 412, a first subtractor 413, a first amplifier 414, a second amplifier 415, a second subtractor 416, and a third subtractor 417; the first period effective value calculator 411 is connected to the first PFC branch 11, the first subtractor 413 and the first amplifier 414, respectively, the first amplifier 414 is connected to the second subtractor 416, the second period effective value calculator 412 is connected to the input terminal of the PFC main circuit 10, the first subtractor 413 and the third subtractor 417, respectively, the first subtractor 413 is connected to the second amplifier 415, the second amplifier 415 is connected to the third subtractor 417, and both the second subtractor 416 and the third subtractor 417 are connected to the adjusting unit 42.
Wherein the first period effective value calculator 411 is configured to output a first current effective value calculated from the first branch current to the first subtractor 413 and the first amplifier 414; the second period effective value calculator 412 is configured to output a total current effective value (Irsm in this embodiment) calculated from the input current to the first subtractor 413, the second subtractor 416, and the third subtractor 417, respectively; the first amplifier 414 amplifies the first current effective value and outputs the amplified value to the second subtractor 416; the first subtractor 413 is configured to output a second current effective value calculated from the total current effective value and the first current effective value to the second amplifier 415; the second amplifier 415 is configured to amplify the second effective current value and output the amplified second effective current value to the second subtractor 416; the second subtractor 416 is configured to compare the amplified first current effective value with the total current effective value, and output a first difference signal (Ierror 1 in this embodiment) to the adjusting unit 42; the third subtractor 417 is configured to compare the amplified second current effective value with the total current effective value and output a second difference signal (Ierror 2 in this embodiment) to the adjusting unit 42, so that the subsequent adjusting unit 42 outputs an adjusting signal to the PWM module 30 according to the first difference signal and the second difference signal.
In the embodiment, the two period effective value calculators respectively and simultaneously sample the first branch current and the input current by selecting proper sampling time, and select proper periods to carry out effective value calculation processing on the first branch current and the input current so as to obtain an effective value of the first branch current, namely a first current effective value, and an effective value of the input current, namely a total current effective value within a period of time; then, the first subtractor 413 is used for subtracting the total current effective value from the first current effective value to obtain a second current effective value; the first current effective value and the second current effective value are amplified twice by the first amplifier 414 and the second amplifier 415, respectively, and then output to the second subtractor 416 and the third subtractor 417, respectively; the second subtractor 416 subtracts the effective value of the total current from the amplified effective value of the first current and outputs a first difference signal to the adjusting unit 42, and the third subtractor 417 subtracts the effective value of the total current from the amplified effective value of the second current and outputs a second difference signal to the second adjusting unit 42; in this embodiment, the effective value of the total circuit is used as a reference for comparison, so as to implement current sharing control of the two PFC branches.
Further, the adjusting unit 42 in this embodiment includes a first PI controller 421, a second PI controller 422, a first post-replacement calculator 423, and a second post-replacement calculator 424; wherein the PI controller is represented as a proportional-integral controller; the first PI controller 421 is connected to the second subtractor 416 and the first post-replacement calculator 423, respectively, the second PI controller 422 is connected to the third subtractor 417 and the second post-replacement calculator 424, respectively, the first post-replacement calculator 423 is further connected to the PWM module 30, and the second post-replacement calculator 424 is further connected to the PWM module 30.
The first PI controller 421 is configured to adjust the first difference signal and output a first adjustment signal to the first post-permutation calculator 423; the first post-displacement calculator 423 is configured to convert the first adjustment signal and output the converted first adjustment signal to the PWM module 30; the second PI controller 422 is configured to adjust the second difference signal and output a second adjustment signal to the second post scaler 424; the second post-displacement calculator 424 is configured to scale the second adjustment signal and output the scaled second adjustment signal to the PWM module 30; in the embodiment, two PI controllers are arranged to respectively adjust and set the first difference signal and the second difference signal and then output two paths of adjusting signals, so that current sharing control is respectively carried out on two PFC branches in a proper period; the two corresponding post-displacement calculators are used for respectively carrying out the same dimension conversion on the first adjusting signal and the second adjusting signal, so that the adjusting signals output by the two PI controllers are converted into the adjusting signals which can be directly acted on the PWM module 30.
Further, the control module 20 includes a sampling unit 21, a control unit 22 and a feed-forward unit 23, the sampling unit 21 is respectively connected to the input end and the output end of the main PFC circuit 10, the first PFC branch 11 and the control unit 22, and the control unit 22 is respectively connected to the feed-forward unit 23 and the PWM module 30.
The sampling unit 21 is configured to sample an input voltage, an input current, and an output voltage of the PFC main circuit 10, output the sampled input voltage to the control unit 22 and the feedforward unit 23, and output the sampled output voltage and input current to the control unit 22; the feedforward unit 23 is configured to output a feedforward voltage obtained according to the sampled input voltage and a first duty ratio signal to the control unit 22; the control unit 22 is configured to output a control signal calculated according to the sampled input voltage, the sampled output voltage, the sampled input current, the feedforward voltage, and the first duty ratio signal to the PWM module 30.
In this embodiment, after sampling the input voltage, the input current, and the output current, the sampling unit 21 performs filtering processing on the input voltage, the input current, and the output voltage, and performs per-unit processing on the input voltage, the input current, and the output voltage, so as to unify dimensions, prevent data overflow during calculation of the post-stage control unit 22, and facilitate calculation; meanwhile, by arranging the feedforward unit 23, the dynamic response speed of the whole circuit can be improved, the cross-over distortion of the Boost-PFC circuit is reduced, and the power factor is improved.
Further, the feedforward unit 23 includes a voltage feedforward loop controller 231 and a duty ratio feedforward loop controller 232, the voltage feedforward loop controller 231 is connected with the sampling unit 21 and the control unit 22, respectively, and the duty ratio feedforward loop is connected with the sampling unit 21 and the control unit 22, respectively.
The voltage feedforward loop controller 231 is configured to output a feedforward voltage to the control unit 22 according to the sampled input voltage; the duty cycle feedforward loop controller 232 is configured to output a first duty cycle signal to the control unit 22 according to the sampled input voltage and the reference voltage; in this embodiment, the working range of the input voltage can be widened by introducing the voltage feedforward loop controller 231, so as to ensure the input power to be constant; the duty ratio feedforward loop controller 232 can effectively improve the dynamic response capability of the whole circuit to the input voltage and improve the reliability of the whole circuit.
Further, the control unit 22 includes a voltage loop controller 221, a multiplier 222, a current loop controller 223 and a first adder 224, the voltage loop controller 221 is connected to the multiplier 222 and the sampling unit 21, the multiplier 222 is connected to the voltage feedforward loop controller 231 and the current loop controller 223, the current loop controller 223 is further connected to the first adder 224, and the first adder 224 is further connected to the duty ratio feedforward loop and the PWM module 30.
The voltage loop controller 221 is configured to output a difference voltage to the multiplier 222 after subtracting the reference voltage from the sampled output voltage; the multiplier 222 is configured to multiply the sampled input voltage, the difference voltage, and the feedforward voltage and output a reference current to the current loop controller 223; the current loop controller 223 is configured to output a second duty ratio signal to the first adder 224 after subtracting the reference current from the sampled input current; the first adder 224 is configured to add the first duty ratio signal and the second duty ratio signal and output a control signal to the PWM module 30; in this embodiment, the duty cycle feedforward loop controller 232 directly feeds back the duty cycle signal of the front-end input voltage to the first adder 224, and compensates the output of the current loop controller 223 with the input voltage, so as to reduce the error of the input current; moreover, by providing the duty cycle feedforward loop controller 232, when the input voltage of the PFC main circuit 10 changes, the duty cycle output can be rapidly adjusted directly by the duty cycle feedforward loop controller 232 without waiting for the output result of the current loop controller 223, thereby improving the dynamic response capability of the whole circuit to the input voltage.
Further, the PWM module 30 includes a converter 31, a driving unit 32, a second adder 33, and a seventh subtractor 34; the converter 31 is connected to the first adder 224 and the driving unit 32, the driving unit 32 is connected to the first PFC branch 11 through the second adder 33, the driving unit 32 is connected to the second PFC branch 12 through the seventh subtractor 34, the second adder 33 is further connected to the first post-replacement calculator 423, and the seventh subtractor 34 is further connected to the second post-replacement calculator 424.
In this embodiment, the converter 31 is configured to step down the control signal and output the control signal to the driving unit 32, compare the control signal with the carrier wave respectively by the driving, and output a first driving signal to the second adder 33, compare the control signal with the carrier wave and output a second driving signal to the seventh subtractor 34; then, the first post-displacement calculator 423 outputs the converted first adjustment signal to the second adder 33, at this time, the first adjustment signal acts on the first driving signal, and the acted first driving signal is output to the first PFC branch 11; similarly, the second adjustment signal converted by the second post-displacement calculator 424 is output to the seventh subtractor 34, at this time, the second adjustment signal acts on the second driving signal, and the acted second driving signal is output to the second PFC branch 12, so that after the first driving signal and the second driving signal are respectively adjusted by the first adjustment signal and the second adjustment signal output by the periodic current-equalizing module 40, the current-equalizing effect in a period can be effectively achieved; the phase difference of the two driving signals is a preset phase angle, the frequency of the carrier wave is 20KHz, the staggered conduction frequency of the corresponding output two driving signals is 40KHz, and the two driving signals are staggered by 180 degrees.
Further, referring to fig. 3, in the second embodiment of the present invention, the difference calculating unit 41 includes a third period effective value calculator 418, a fourth period effective value calculator 419, a fourth subtractor 401, a fifth subtractor 402, and a sixth subtractor 403; the third period effective value calculator 418 is connected to the fourth subtractor 401 and the fifth subtractor 402, respectively, the fourth period effective value calculator 419 is connected to the fourth subtractor 401, the fourth subtractor 401 is connected to the fifth subtractor 402, the fifth subtractor 402 is connected to the sixth subtractor 403, and the sixth subtractor 403 is connected to the adjusting unit 42.
Wherein the third period effective value calculator 418 is configured to output the first current effective value calculated according to the first branch current to the fourth subtractor 401 and the fifth subtractor 402; the fourth period effective value calculator 419 is configured to output the total current effective value calculated from the input current to the fourth subtractor 401; the fourth subtractor 401 is configured to output the second current effective value to the fifth subtractor 402 according to the first current effective value and the total current effective value; the fifth subtractor 402 is configured to output a difference current effective value (Ierror in the present embodiment) obtained by subtracting the first current effective value from the second current effective value to the sixth subtractor 403; the sixth subtractor 403 is configured to compare the difference current effective value with the reference value and output a difference signal to the adjusting unit 42; compared with the first embodiment, the difference calculating unit 41 in this embodiment obtains the difference current effective value by subtracting the first current effective value and the second current effective value, and then compares the difference current effective value with the reference value to output the difference signal to the adjusting unit 42, instead of outputting the total input current effective value as the reference, the corresponding difference calculating unit 41 only outputs one difference signal to the adjusting unit 42, so as to achieve the subsequent current sharing effect.
Further, the adjusting unit 42 in this embodiment includes a third PI controller 425 and a third post-replacement calculator 426; the third PI controller 425 is connected to the sixth subtractor 403 and the third post-permutation calculator 426, respectively, and the third post-permutation calculator 426 is connected to the second adder 33 and the seventh subtractor 34, respectively.
The third PI controller 425 is configured to adjust the difference signal and output an adjustment signal to the third post-scaler 426; the third post-displacement calculator 426 is configured to convert the adjustment signal and output the converted adjustment signal to the PWM module 30; compared with the first embodiment, in the present embodiment, only one PI controller is provided to adjust the difference signal, and then the adjustment signal is subjected to dimension conversion, so that the adjustment signal can directly act on the first driving signal and the second driving signal to achieve the current sharing effect in the period.
Further, referring to fig. 4, the first PFC branch 11 includes a first power switch Q1, a first boost inductor L1, a first rectifier diode D1, and a resistor R1, and the second PFC branch 12 includes a second power switch, a second boost inductor L2, and a second rectifier diode D2; the grid electrode of the first power switch tube Q1 is connected with the first driving unit 3243, the source electrode of the first power switch tube Q1 is connected with one end of the resistor R1 and the sampling module 20, the other end of the resistor R1 is grounded, the drain electrode of the first power switch tube Q1 is connected with one end of the first boosting inductor L1 and the anode of the first rectifier diode D1, the other end of the first boosting inductor L1 is connected with the power supply input end, and the cathode of the second rectifier diode D2 is connected with one end of the energy storage capacitor C1, the load and the sampling module 20; the grid electrode of the second power switch tube Q2 is connected with the second drive unit 3244, the source electrode of the first power switch tube Q1 is grounded, the drain electrode of the second power switch tube Q2 is connected with one end of the second boost inductor L2 and the anode of the second rectifier diode D2, the other end of the second boost inductor L2 is connected with the power supply input end, and the cathode of the second rectifier diode D2 is connected with one end of the energy storage capacitor C1, the load and the sampling module 20; in this embodiment, two driving signals respectively drive the first power switch Q1 and the second power switch Q2 to be turned on or off, so as to control the repeated charging and discharging of the first boost inductor L1 and the second boost inductor L2, thereby realizing the voltage boosting.
The present invention also provides a control method for a Boost-PFC control circuit, referring to fig. 5, the control method includes the following steps:
s100, the control module outputs a control signal obtained by calculation according to the input voltage, the input current and the output voltage of the PFC main circuit to the PWM module;
s200, calculating by a period current equalizing module according to the input current and a first branch current of a first PFC branch to obtain a difference signal, and outputting an adjusting signal to the PWM module according to the difference signal;
s300, the PWM module adjusts the current sharing of the control signal according to the adjusting signal, outputs a first driving signal to the first PFC branch, and outputs a second driving signal to the second PFC branch.
In summary, the present invention provides a Boost-PFC control circuit and a control method thereof, wherein the Boost-PFC control circuit includes a PFC main circuit, a control module, a PWM module and a period current equalizing module, and the PFC main circuit includes a first PFC branch and a second PFC branch connected in parallel; the control module is used for outputting a control signal obtained by calculation according to the input voltage, the input current and the output voltage of the PFC main circuit to the PWM module; the period current equalizing module is used for calculating to obtain a difference signal according to the input current and the first branch current and outputting an adjusting signal to the PWM module according to the difference signal; the PWM module is used for outputting a first driving signal to the first PFC branch after the control signal is subjected to current sharing regulation according to the regulation signal and outputting a second driving signal to the second PFC branch; the invention can effectively solve the problem of current imbalance between the parallel branches by arranging the periodic current-sharing module, thereby improving the reliability of the whole circuit.
It should be understood that equivalents and modifications of the technical solution and inventive concept thereof may occur to those skilled in the art, and all such modifications and alterations should fall within the scope of the appended claims.
Claims (10)
1. A Boost-PFC control circuit is characterized by comprising a PFC main circuit, a control module, a PWM module and a period current-sharing module, wherein the PFC main circuit comprises a first PFC branch and a second PFC branch which are connected in parallel; the control module is respectively connected with the input end and the output end of the PFC main circuit and the PWM module, the PWM module is respectively connected with the first PFC branch, the second PFC branch and the period current-sharing module, and the period current-sharing module is respectively connected with the input end of the PFC main circuit and the first PFC branch;
the control module is used for outputting a control signal obtained according to the input voltage, the input current and the output voltage of the PFC main circuit to the PWM module;
the period current equalizing module is used for obtaining a difference signal according to the input current and the first branch current and outputting an adjusting signal to the PWM module according to the difference signal;
the PWM module is used for outputting a first driving signal to the first PFC branch after the control signal is subjected to current sharing regulation according to the regulation signal, and outputting a second driving signal to the second PFC branch.
2. The Boost-PFC control circuit of claim 1, wherein the period current equalizing module comprises a difference calculating unit and an adjusting unit; the difference value calculating unit is respectively connected with the first PFC branch, the input end of the PFC main circuit and the adjusting unit, and the adjusting unit is connected with the PWM module;
the difference value calculating unit is used for outputting a first current effective value and a second current effective value according to the input current and the first branch current, and outputting a difference value signal to the adjusting unit according to the first current effective value and the second current effective value;
the adjusting unit is used for outputting an adjusting signal to the PWM module according to the difference signal.
3. The Boost-PFC control circuit of claim 2, wherein the difference calculation unit comprises a first period effective value calculator, a second period effective value calculator, a first subtractor, a first amplifier, a second subtractor, and a third subtractor;
the first period effective value calculator is used for outputting a first current effective value calculated according to the first branch current to the first subtracter and the first amplifier;
the second period effective value calculator is used for respectively outputting the total current effective values calculated according to the input current to the first subtracter, the second subtracter and the third subtracter;
the first amplifier amplifies the first current effective value and outputs the amplified first current effective value to the second subtractor;
the first subtractor is used for outputting a second current effective value obtained according to the total current effective value and the first current effective value to the second amplifier;
the second amplifier is used for amplifying the second current effective value and outputting the amplified second current effective value to the second subtracter;
the second subtracter is used for comparing the amplified first current effective value with the total current effective value and outputting a first difference signal to the adjusting unit;
and the third subtracter is used for comparing the amplified second current effective value with the total current effective value and outputting a second difference signal to the adjusting unit.
4. The Boost-PFC control circuit of claim 2, wherein the difference calculation unit comprises a third period effective value calculator, a fourth subtractor, a fifth subtractor, and a sixth subtractor;
the third period effective value calculator is used for outputting a first current effective value flowing out according to the first branch circuit to the fourth subtracter and the fifth subtracter;
the fourth period effective value calculator is used for outputting a total current effective value obtained according to the input current to the fourth subtracter;
the fourth subtracter is used for outputting a second current effective value to the fifth subtracter according to the first current effective value and the total current effective value;
the fifth subtractor is configured to output a difference current effective value obtained by subtracting the first current effective value and the second current effective value to the sixth subtractor;
and the sixth subtracter is used for comparing the difference current effective value with a reference value and outputting a difference signal to the adjusting unit.
5. The Boost-PFC control circuit of claim 3, wherein the regulation unit comprises a first PI controller, a second PI controller, a first post-permutation calculator, and a second post-permutation calculator;
the first PI controller is used for adjusting the first difference signal and outputting a first adjusting signal to the first post-displacement calculator;
the first post-displacement calculator is used for converting the first adjusting signal and outputting the converted first adjusting signal to the PWM module;
the second PI controller is used for adjusting the second difference signal and outputting a second adjusting signal to the second post-displacement calculator;
and the second post-displacement calculator is used for converting the second adjusting signal and outputting the converted second adjusting signal to the PWM module.
6. The Boost-PFC control circuit of claim 4, wherein the regulation unit comprises a third PI controller and a third post-displacement calculator;
the third PI controller is used for adjusting the difference signal and outputting the adjusting signal to the third post-displacement calculator;
and the third post-displacement calculator is used for converting the adjusting signal and outputting the converted adjusting signal to the PWM module.
7. The Boost-PFC control circuit of claim 4, wherein the control module comprises a sampling unit, a control unit, and a feed-forward unit;
the sampling unit is used for sampling the input voltage, the input current and the output voltage of the PFC main circuit, respectively outputting the sampled input voltage to the control unit and the feedforward unit, and outputting the sampled output voltage and the sampled input current to the control unit;
the feedforward unit is used for outputting feedforward voltage obtained according to the sampled input voltage and a first duty ratio signal to the control unit;
the control unit is used for outputting a control signal obtained according to the sampled input voltage, the sampled output voltage, the sampled input current, the feedforward voltage and the first duty ratio signal to the PWM module.
8. The Boost-PFC control circuit of claim 7, wherein the feed-forward unit comprises a voltage feed-forward loop controller and a duty cycle feed-forward loop controller;
the voltage feedforward loop controller is used for outputting feedforward voltage to the control unit according to the sampled input voltage;
the duty ratio feedforward loop controller is used for outputting the first duty ratio signal to the control unit according to the sampled input voltage and the reference voltage.
9. The Boost-PFC control circuit of claim 8, wherein the control unit comprises a voltage loop controller, a multiplier, a current loop controller, and an adder;
the voltage ring controller is used for outputting a difference voltage to the multiplier after the difference is made between the reference voltage and the sampled output voltage;
the multiplier is used for multiplying the sampled input voltage, the difference voltage and the feedforward voltage and then outputting a reference current to the current loop controller;
the current loop controller is used for outputting a second duty ratio signal to the adder after the difference is made between the reference current and the sampled input current;
the adder is used for adding the first duty ratio signal and the second duty ratio signal and then outputting the control signal to the PWM module.
10. A control method based on the Boost-PFC control circuit of any one of claims 1 to 9, comprising the steps of:
the control module outputs a control signal obtained according to the input voltage, the input current and the output voltage of the PFC main circuit to the PWM module;
the period current equalizing module obtains a difference signal according to the input current and a first branch current of a first PFC branch, and outputs an adjusting signal to the PWM module according to the difference signal;
the PWM module adjusts the control signal according to the adjustment signal, outputs a first driving signal to the first PFC branch and outputs a second driving signal to the second PFC branch.
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