CN112688553B - 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, and 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 equalizing module outputs an adjusting 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 current sharing adjustment of the control signal according to the adjusting signal, and outputs a second driving signal to the second PFC branch; the current balancing method can effectively solve the problem of unbalanced current between parallel branches by arranging the period current balancing 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 Boost-PFC (Power Factor Correction, positive power factor) converters, there is a bias in the current of the two parallel branches, since the device parasitic parameters of the two branches cannot be exactly the same. Long-term operation in a non-current-sharing state can lead to a reduction in power factor and a reduction in the lifetime of the branch with a large current, thereby affecting the overall converter efficiency and lifetime.
There is thus a need for improvements and improvements in the art.
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 unbalanced current between parallel branches, thereby improving the reliability of the whole circuit.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the Boost-PFC control circuit comprises a PFC main circuit, a control module, a PWM module and a period current equalizing 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, the output end and the PWM module of the PFC main circuit, 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 and the first PFC branch of the PFC main circuit;
The control module is used for outputting control signals 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 adjustment according to the adjusting signal, and outputting a second driving signal to the second PFC branch; the phase of the first drive signal and the phase of the second drive signal differ by 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 calculation 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 calculation 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 outputting the total current effective value calculated according to the input current to the first subtracter, the second subtracter and the third subtracter respectively;
the first amplifier amplifies the first current effective value and outputs the amplified first current effective value to the second subtracter;
the first subtracter is used for outputting a second current effective value obtained by 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 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 then outputting a first difference signal to the regulating unit;
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 regulating unit.
In the Boost-PFC control circuit, the difference value calculation 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 used for outputting a first current effective value calculated according to the first branch current to the fourth subtracter and the fifth subtracter;
The fourth period effective value calculator is used for outputting the 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 subtracter is used for outputting a difference current effective value obtained by making a difference between the first current effective value and the second current effective value to the sixth subtracter;
the sixth subtracter is used for comparing the effective value of the difference current with a reference value and then outputting a difference signal to the regulating unit.
In the Boost-PFC control circuit, the regulating unit comprises a first PI controller, a second PI controller, a first post-displacement calculator and a second post-displacement calculator;
The first PI controller is used for outputting a first adjusting signal to the first post-displacement calculator after adjusting the first difference signal;
the first post-displacement calculator is used for converting the first regulating signal and outputting the converted first regulating signal to the PWM module;
The second PI controller is used for outputting a second adjusting signal to the second post-displacement calculator after adjusting the second difference signal;
The second post-displacement calculator is used for converting the second regulating signal and outputting the converted second regulating signal to the PWM module.
In the Boost-PFC control circuit, the regulating unit comprises a third PI controller and a third post-displacement calculator;
The third PI controller is used for outputting the adjusting signal to the third post-displacement calculator after adjusting the difference signal;
and the third post-displacement calculator is used for converting the regulating signal and outputting the converted regulating 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 and a first duty ratio signal obtained according to the sampled input voltage to the control unit;
the control unit is used for outputting control signals 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 ring controller, a multiplier, a current ring controller and an adder;
The voltage loop controller is used for outputting a difference voltage to the multiplier after the reference voltage and the sampled output voltage are subjected to difference;
The multiplier is used for multiplying the sampled input voltage, the difference voltage and the feedforward voltage and outputting 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 reference current and the sampled input current are subjected to difference;
The adder is used for adding the first duty cycle signal and the second duty cycle signal and 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 a difference signal according to the input current and the first branch current of the first PFC branch, and outputs an adjusting signal to the PWM module according to the difference signal;
The PWM module outputs a first driving signal to the first PFC branch after current sharing adjustment of the control signal according to the adjusting signal, and outputs a second driving signal to the second PFC branch; the phase of the first drive signal and the phase of the second drive signal differ by 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 control signals 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 adjustment according to the adjusting signal, and outputting a second driving signal to the second PFC branch; according to the invention, the problem of unbalanced current between parallel branches can be effectively solved by arranging the period current sharing module, so that the reliability of the whole circuit is improved.
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 circuit diagram of a second embodiment of the Boost-PFC control circuit according to the present invention;
Fig. 4 is a schematic circuit diagram of a PFC main 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 provided by 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 unbalanced current between parallel branches, thereby improving the reliability of the whole circuit.
In order to make the objects, technical solutions and effects of the present invention clearer and more specific, the present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Referring to fig. 1 and 2, a Boost-PFC (Power Factor Correction, power factor positive)) control circuit provided by the present invention includes a PFC main circuit 10, a control module 20, a PWM (Pulse Width Modulation: pulse width modulation) module 30 and a period current equalizing module 40, where the PFC main circuit 10 includes a first PFC branch 11 and a second PFC branch 12 connected in parallel; the control module 20 is respectively connected with the input end and the output end of the PFC main circuit 10 and the PWM module 30, the PWM module 30 is respectively connected with 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 with the input end of the PFC main circuit 10 and the first PFC branch 11.
The control module 20 is configured to output a control signal calculated according to an input voltage (Vrect in the embodiment), an input current (Irect in the embodiment), and an output voltage (Vout in the embodiment) of the PFC main circuit 10 to the PWM module 30; the period equalizing module 40 is configured to calculate a difference signal according to the input current and the first branch current (Ig 1 in this embodiment), 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 and output a second driving signal to the second PFC branch 12 after current sharing adjustment of the control signal according to the adjustment signal; the phase difference of the first driving signal and the second driving signal is preset phase angle; the current equalizing module 40 is arranged to realize the current equalizing effect in the period, so that the problem of unbalanced current between parallel branches can be effectively solved, and the reliability of the whole circuit is further improved.
Further, the period equalizing module 40 includes a difference calculating unit 41 and an adjusting unit 42; the difference calculation unit 41 is connected to the input of the first PFC branch 11, the PFC main circuit 10, and the regulator unit 42, respectively, and the regulator 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 the PWM module 30 further controls the operations of the first PFC branch 11 and the second PFC branch 12; the period effective values in the two branches are calculated after the input current and the first branch current are sampled through the period current sharing module 40, so that 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 a control circuit is improved; and the low-voltage end sampling is adopted, so that the cost and the hardware design difficulty can be reduced.
Further, referring 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, 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, the first subtractor 413 is connected to the second amplifier 415, the second amplifier 415 is connected to the third subtractor 417, and the second subtractor 416 and the third subtractor 417 are both connected to the adjusting unit 42.
Wherein the first period effective value calculator 411 is configured to output a first current effective value calculated according to 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 the 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 first current effective value to the second subtractor 416; the first subtractor 413 is configured to output a second current effective value calculated according to 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 current effective value and output the amplified second current effective 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 adjustment unit 42, so that the subsequent adjustment unit 42 outputs an adjustment signal to the PWM module 30 according to the first difference signal and the second difference signal.
In the embodiment, through selecting proper sampling time by the two period effective value calculators, the first branch current and the input current are sampled respectively and simultaneously, and proper periods are selected to carry out effective value calculation processing on the first branch current and the input current, so that 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, in a period of time are obtained; then, the first subtracter 413 performs difference between the total current effective value and 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 performs a difference between the total current effective value and the amplified first current effective value to output a first difference signal to the adjusting unit 42, and the third subtractor 417 performs a difference between the total current effective value and the amplified second current effective value to output a second difference signal to the second adjusting unit 42; in the embodiment, the current sharing control of the two PFC branches is realized by taking the effective value of the total circuit as a reference for comparison.
Further, the adjusting unit 42 in the present embodiment includes a first PI controller 421, a second PI controller 422, a first post-permutation calculator 423, and a second post-permutation calculator 424; wherein the PI controller is denoted as a proportional-integral controller; the first PI controller 421 is connected to the second subtractor 416 and the first post-displacer 423, respectively, the second PI controller 422 is connected to the third subtractor 417 and the second post-displacer 424, respectively, the first post-displacer 423 is further connected to the PWM module 30, and the second post-displacer 424 is further connected to the PWM module 30.
The first PI controller 421 is configured to adjust the first difference signal and then output a first adjustment signal to the first post-permutation calculator 423; the first post-permutation 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-replacing calculator 424 is configured to convert the second adjustment signal and output the converted 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 post-displacement calculators are respectively used for carrying out the same-dimension conversion on the first regulating signal and the second regulating signal, so that the regulating signals output by the two PI controllers are converted into the regulating signals which can directly act on the PWM module 30.
Further, the control module 20 includes a sampling unit 21, a control unit 22 and a feedforward unit 23, the sampling unit 21 is respectively connected to the input end, the output end, the first PFC branch 11 and the control unit 22 of the PFC main circuit 10, and the control unit 22 is respectively connected to the feedforward 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 the sampled input current to the control unit 22; the feedforward unit 23 is configured to output a feedforward voltage obtained from 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 from the sampled input voltage, the sampled output voltage, the sampled input current, the feedforward voltage, and the first duty cycle signal to the PWM module 30.
In this embodiment, after the sampling unit 21 samples the input voltage, the input current and the output current, it 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 later 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 crossover distortion of the Boost-PFC circuit can be reduced, and the power factor can be improved.
Further, the feedforward unit 23 includes a voltage feedforward loop controller 231 and a duty cycle 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 cycle feedforward loop is connected with the sampling unit 21 and the control unit 22, respectively.
Wherein, 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; the input voltage working range can be widened by introducing the voltage feedforward loop controller 231 in the embodiment, so that the input power is ensured 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 differentiating the reference voltage and the sampled output voltage; the multiplier 222 multiplies the sampled input voltage, the difference voltage and the feedforward voltage to 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 and the sampled input current; the first adder 224 is configured to add the first duty cycle signal and the second duty cycle signal and output a control signal to the PWM module 30; in this embodiment, the duty ratio feedforward loop controller 232 directly feeds back the duty ratio signal of the front end input voltage to the first adder 224, and compensates the input voltage for the output of the current loop controller 223, so that the input current error can be reduced; moreover, by providing the duty ratio feedforward loop controller 232, when the input voltage of the PFC main circuit 10 is changed, the duty ratio output can be quickly adjusted directly by the duty ratio 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, respectively, 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-permutation calculator 423, and the seventh subtractor 34 is further connected to the second post-permutation 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 driving and output the first driving signal to the second adder 33, compare the control signal with the carrier wave and output the second driving signal to the seventh subtractor 34; then, the first post-permutation calculator 423 outputs the converted first adjustment signal to the second adder 33, and 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-replacing 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 period current sharing module 40, the current sharing effect in the period can be effectively achieved; the phase difference of the two paths of driving signals is preset phase angle, the frequency of the carrier wave is 20KHz, the staggered conduction frequency of the corresponding output two paths of driving signals is 40KHz, and the two paths of driving signals are out of phase 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 adjustment 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 this embodiment) obtained by subtracting the first current effective value and the second current effective value to the sixth subtractor 403; the sixth subtractor 403 is configured to compare the effective value of the difference current with a reference value and output a difference signal to the adjusting unit 42; compared to the first embodiment, the difference calculating unit 41 in this embodiment obtains the effective value of the difference current by differencing the effective value of the first current and the effective value of the second current, and then compares the effective value of the difference current with the reference value to output the difference signal to the adjusting unit 42, instead of referencing the effective value of the total input current, 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 the present embodiment includes a third PI controller 425 and a third post-permutation 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.
Wherein, 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-permutation 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 dimension conversion is performed on the adjustment signal, so that the adjustment signal can directly act on the first driving signal and the second driving signal, so as 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 rectifying 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 rectifying 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 a 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 a first boost inductor L1 and the positive electrode of a first rectifying diode D1, the other end of the first boost inductor L1 is connected with the power input end, and the negative electrode of a second rectifying diode D2 is connected with one end of an energy storage capacitor C1, a load and the sampling module 20; the grid electrode of the second power switch tube Q2 is connected with the second driving 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 positive electrode of the second rectifying diode D2, the other end of the second boost inductor L2 is connected with the power input end, and the negative electrode of the second rectifying 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 drive the first power switch Q1 and the second power switch Q2 to turn on or off respectively, so as to control repeated charging and discharging of the first boost inductor L1 and the second boost inductor L2, and realize voltage boost.
The invention also correspondingly provides a control method of the Boost-PFC control circuit, referring to FIG. 5, the control method comprises the following steps:
s100, the control module outputs control signals 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, a period current sharing module calculates a difference signal according to the input current and the first branch current of the first PFC branch, and outputs an adjusting signal to the PWM module according to the difference signal;
S300, the PWM module outputs a first driving signal to the first PFC branch and outputs a second driving signal to the second PFC branch after current sharing adjustment of the control signal is carried out according to the adjusting signal.
In summary, the Boost-PFC control circuit and the control method thereof provided by the invention, 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 control signals 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 adjustment according to the adjusting signal, and outputting a second driving signal to the second PFC branch; according to the invention, the problem of unbalanced current between parallel branches can be effectively solved by arranging the period current sharing module, so that the reliability of the whole circuit is improved.
It will be understood that equivalents and modifications will occur to those skilled in the art in light of the present invention and their spirit, and all such modifications and substitutions are intended to be included within the scope of the present invention as defined in the following claims.
Claims (7)
1. The 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, the output end and the PWM module of the PFC main circuit, 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 and the first PFC branch of the PFC main circuit;
the control module is used for outputting control signals 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 adjustment according to the adjusting 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 preset phase angle, the frequency of a carrier wave is 20KHz, the staggered conduction frequency of the first driving signal and the second driving signal is 40KHz, and the driving signals of the first driving signal and the second driving signal are 180 degrees out of phase;
the control module further comprises a control unit and a feedforward unit;
The feedforward unit is used for outputting feedforward voltage and a first duty ratio signal obtained according to the sampled input voltage to the control unit;
The control unit is used for outputting control signals 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;
the feedforward unit comprises a voltage feedforward loop controller and a duty cycle 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;
The control unit comprises a current loop controller and an adder;
The duty ratio feedforward controller directly feeds back a duty ratio signal of front-end input voltage to the adder, and compensates the input voltage for the output of the current loop controller;
the control module further comprises a sampling 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 sampling unit performs filtering processing on the input voltage, the input current and the output voltage after sampling the input voltage, the input current and the output current, and performs per unit processing on the input voltage, the input current and the output voltage;
The control unit also comprises a voltage ring controller and a multiplier;
The voltage loop controller is used for outputting a difference voltage to the multiplier after the reference voltage and the sampled output voltage are subjected to difference;
The multiplier is used for multiplying the sampled input voltage, the difference voltage and the feedforward voltage and outputting 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 reference current and the sampled input current are subjected to difference;
The adder is used for adding the first duty cycle signal and the second duty cycle signal and then outputting the control signal to the PWM module;
the adder includes a first adder; the voltage feedforward loop controller is respectively connected with the sampling unit and the multiplier, and the duty ratio feedforward loop controller is respectively connected with the sampling unit and the first adder;
The PWM module comprises a second adder, a converter, a seventh subtracter and a driving unit, wherein the converter is respectively connected with the first adder and the driving unit, the driving unit is connected with the first PFC branch through the second adder, the driving unit is connected with the second PFC branch through the seventh subtracter, the second adder is also connected with a first post-displacement calculator, and the seventh subtracter is also connected with a second post-displacement calculator; the converter is used for performing step-down processing on the control signal and outputting the control signal to the driving unit; the driving unit is used for outputting a first driving signal to the second adder according to the control signal, and the second adder outputs the first driving signal to the first PFC branch according to a first adjusting signal output by the first post-displacement calculator; the driving unit is further used for outputting a second driving signal to a seventh subtracter according to the control signal, and the seventh subtracter outputs the second driving signal to a second PFC branch according to a second adjusting signal output by a second post converter; the phase of the first drive signal and the phase of the second drive signal differ by a preset phase angle.
2. The Boost-PFC control circuit of claim 1, wherein the period-equalizing module comprises a difference calculation unit and an adjustment unit; the difference value calculation 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 calculation 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 includes 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 outputting the total current effective value calculated according to the input current to the first subtracter, the second subtracter and the third subtracter respectively; the first amplifier amplifies the first current effective value and outputs the amplified first current effective value to the second subtracter;
The first subtracter 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 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 then outputting a first difference signal to the regulating unit;
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 regulating unit.
4. The Boost-PFC control circuit of claim 2, wherein the difference calculation unit includes 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 subtracter is used for outputting a difference current effective value obtained by making a difference between the first current effective value and the second current effective value to the sixth subtracter;
the sixth subtracter is used for comparing the effective value of the difference current with a reference value and then outputting a difference signal to the regulating unit.
5. The Boost-PFC control circuit of claim 3 wherein the conditioning unit comprises a first PI controller, a second PI controller, a first post-displacer, and a second post-displacer;
The first PI controller is used for outputting a first adjusting signal to the first post-displacement calculator after adjusting the first difference signal;
the first post-displacement calculator is used for converting the first regulating signal and outputting the converted first regulating signal to the PWM module;
The second PI controller is used for outputting a second adjusting signal to the second post-displacement calculator after adjusting the second difference signal;
The second post-displacement calculator is used for converting the second regulating signal and outputting the converted second regulating signal to the PWM module.
6. The Boost-PFC control circuit of claim 4, wherein the conditioning unit comprises a third PI controller and a third post-permutation calculator;
The third PI controller is used for outputting the adjusting signal to the third post-displacement calculator after adjusting the difference signal;
and the third post-displacement calculator is used for converting the regulating signal and outputting the converted regulating signal to the PWM module.
7. A control method based on the Boost-PFC control circuit according to any one of claims 1 to 6, characterized by comprising the steps of:
The control module outputs control signals 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 the first branch current of the first PFC branch, and outputs an adjusting signal to the PWM module according to the difference signal;
the PWM module outputs a first driving signal to the first PFC branch after current sharing adjustment of the control signal according to the adjusting signal, 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 preset phase angle, the frequency of a carrier wave is 20KHz, the staggered conduction frequency of the first driving signal and the second driving signal is 40KHz, and the driving signals of the first driving signal and the second driving signal are 180 degrees out of phase;
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 sampling unit performs filtering processing on the input voltage, the input current and the output voltage after sampling the input voltage, the input current and the output current, and performs per unit processing on the input voltage, the input current and the output voltage.
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| CN101217255B (en) * | 2008-01-16 | 2010-12-22 | 艾默生网络能源有限公司 | A PFC circuit with current sharing control module and the corresponding current sharing control method |
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| JP2011239539A (en) * | 2010-05-07 | 2011-11-24 | Minebea Co Ltd | Switching power supply device and control method for the same |
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| CN104539219A (en) * | 2014-12-04 | 2015-04-22 | 苏州汇川技术有限公司 | Current sharing control method and system |
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