CN115733352A - PFC converter, PFC converter system and method - Google Patents
PFC converter, PFC converter system and method Download PDFInfo
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- CN115733352A CN115733352A CN202111021688.8A CN202111021688A CN115733352A CN 115733352 A CN115733352 A CN 115733352A CN 202111021688 A CN202111021688 A CN 202111021688A CN 115733352 A CN115733352 A CN 115733352A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
The invention discloses a PFC converter, a PFC converter system and a method. The PFC converter unit is provided with a Buck circuit part based on a Buck power switch tube S1 and a Boost circuit part based on a Boost power switch tube S2. The Buck power switch tube S1 and the Boost power switch tube S2 bring great flexibility to the control of the converter, and can effectively reduce switching loss and conduction loss. In order to make the output power of the PFC converter larger, the converter is operated in a Current Continuous Mode (CCM) in both Buck and Boost phases. On the basis of the traditional Average Current Control (ACC), a novel control method based on instantaneous power conservation is provided at the Buck stage, the input current waveform of the PFC converter is effectively improved, the input current waveform is close to a sine wave and is in the same phase with the input voltage, and the power factor is larger than 99%.
Description
Technical Field
The present invention relates to the field of switching power supplies, and in particular, to PFC converters, PFC converter systems and methods.
Background
As is well known, with the great progress of power semiconductor technology, the use of various electrical devices of switching power supplies in industry, automobile manufacturing industry, information service and the like is becoming more and more common, so that many nonlinear loads appear in the power grid, the input current on the power grid side is distorted, serious harmonic components are generated, and the power grid cannot meet the requirement standard of the electrical devices, and the power grid becomes the most important power public hazard. In order to meet the IEC-61000-3-2 standard requirements, power converters connected to the power grid need to have a fast sinusoidal input current waveform. Active current shaping techniques are commonly used for converters in the power range of about 1-2KW to reduce the size of power converters that are constructed from conventional diode bridge rectifiers plus DC/DC switching converters. The Boost converter is the first choice for a single-phase PFC converter, but its output dc voltage must be greater than the input voltage peak. The Buck converter can also achieve the purpose of power factor correction, but dead zones exist at zero crossing, and the power factor is low.
Disclosure of Invention
The present invention is directed to solving the problems of the prior art and provides a novel PFC converter, a PFC converter system and a method thereof.
In order to achieve the purpose, the technical scheme of the invention is as follows: the PFC converter is provided with a Buck circuit part based on a Buck power switch tube S1 and a Boost circuit part based on a Boost power switch tube S2, and if one of the Buck circuit part and the Boost circuit part is in a working state, the other one is in a non-working state.
As a preferable aspect of the PFC converter, one of the Buck circuit part and the Boost circuit part to be in an operating state is determined according to a comparison result of an input voltage and an output voltage of the PFC converter.
The invention also provides a PFC converter system which comprises an alternating current input unit, a rectifying unit, a filtering unit, a controller unit, a load unit and a PFC converter, wherein the alternating current input unit, the rectifying unit, the filtering unit, the PFC converter and the load unit are sequentially connected, the controller unit samples the input voltage and the output voltage of the PFC converter and determines the one of the Buck circuit part and the Boost circuit part which is required to be in the working state according to the comparison result of the input voltage and the output voltage of the PFC converter and enables the Buck circuit part and the Boost circuit part to work.
As the preferable scheme of the PFC converter system, if the input voltage of the PFC converter is greater than the output voltage, the Buck circuit part is in a working state; and if the input voltage of the PFC converter is less than or equal to the output voltage, the Boost circuit part is in a working state.
As a preferable aspect of the PFC converter system, the PFC converter system further has a driving unit, and the controller unit controls the PFC converter through the driving unit.
The invention further provides a method for designing a PFC converter system, comprising,
modeling and analyzing a Buck circuit part and a Boost circuit part of the PFC converter;
analyzing the gain of the open loop of the system; and the number of the first and second groups,
and calculating to obtain the control strategy of the PFC converter system.
Compared with the prior art, the invention has the beneficial effects that: a novel average current control method based on instantaneous power conservation is provided in the Buck stage, so that the input current waveform of the converter has good sine property and is consistent with the input voltage phase.
Drawings
FIG. 1 is a circuit topology of an AC/DC PFC converter according to the present invention.
Fig. 2 is an equivalent circuit when the circuit is in the Boost stage.
Fig. 3 is an equivalent circuit when the circuit is in the Buck stage.
Fig. 4 is a graph of open loop gain baud controlling current to inductor L.
FIG. 5 is a block diagram of a method for controlling an AC/DC PFC converter.
Fig. 6 is a flow chart of the main program of the system.
FIG. 7 is a flowchart of the timed interrupt service routine.
Fig. 8 is a schematic block diagram of system control.
FIG. 9 is a waveform diagram of input voltage and input current at nominal circuit parameters.
Fig. 10 is a graph of input voltage and output voltage waveforms.
Detailed Description
The invention is explained in more detail below by means of a specific embodiment in conjunction with the attached drawing. Here, the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. In addition, the technical features involved in the respective embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Referring to fig. 1, an AC/DC PFC (Power Factor Correction) converter is shown.
The AC/DC PFC converter is provided with a diode rectifier bridge, an input filter inductor Lf, a Buck power switch tube S1, an energy storage inductor L, a freewheeling diode D1, a Boost power switch tube S2, an output diode D2 and an output capacitor C0.
The first input end and the second input end of the diode rectifier bridge are respectively connected with the first end and the second end of the alternating current power supply. The first output end of the diode rectifier bridge is connected with the first end of the input filter inductor Lf. The second end of the input filter inductor Lf is respectively connected with the first end of the input filter capacitor Cf and the first end of the Buck power switch tube S1. And the second end of the Buck power switch tube S1 is respectively connected with the first end of the energy storage inductor L and the negative end of the fly-wheel diode D1. The second end of the energy storage inductor L is connected to the first end of the Boost power switch tube S2 and the positive end of the output diode D2, respectively. The negative terminal of the output diode D is connected to the first terminal of the output capacitor C0 and the first terminal of the load RL respectively. And a second output end of the diode rectifier bridge is respectively connected with a second end of the input filter capacitor Cf, a positive end of a fly-wheel diode D1, a second end of a Boost power switch tube S2, a second end of an output capacitor C0 and a second end of a load RL.
In the circuit, the Buck power switch tube S1 and the Boost power switch tube S2 bring great flexibility to the control of the converter, and can effectively reduce the switching loss and the conduction loss. The converter operates in a Current Continuous Mode (CCM) in both Buck and Boost stages, small signal modeling analysis is performed on the converter through a state space average method on the basis of traditional Average Current Control (ACC), transfer functions controlled to inductance L current in the Boost stage and the Buck stage are obtained respectively, and a novel average current control method based on instantaneous power conservation is provided in the Buck stage, so that the input current waveform of the converter has good sine property and is consistent with the input voltage phase.
The novel control method of the AC/DC PFC converter based on the instantaneous power conservation is carried out according to the following steps:
and S1, respectively carrying out small-signal modeling analysis on the Boost mode and the Buck mode of the power factor correction converter.
Referring to fig. 2, when the circuit is in the Boost stage equivalent circuit diagram, the current transfer function of the control to the energy storage inductor L can be obtained as follows:
referring to fig. 3, the equivalent circuit diagram of the circuit at the Buck stage at this time can obtain the transfer function of the current controlling the inductor L as follows:
and S2, analyzing the gain of the open loop of the system.
The formula (1-1) shows that the design of the system controller is irrelevant to the duty ratio in the Boost stage, and the formula (1-2) shows that the bode diagram of the system changes along with the change of the duty ratio in the Buck stage. Fig. 4 shows the current open loop gain bode plot for the control to inductor L, where Lf =400h, r1=0.1 Ω, L =600h, r2=0.1 Ω, and the Buck phase is the bode plot at the time of the peak of the input voltage. According to the bode diagram, the PFC converter is easy to design whether working in a Boost stage or a Buck stage.
And step three, calculating to obtain a novel control strategy of the AC/DC PFC converter.
And (3) the AC/DC power factor correction converter is equivalent to an ideal system without any loss, and the instantaneous input power of the system is equal to the output power by the equation:
V in (t)i Lf (t)＝V o i L (t) (1-3)
if the output power is constant, and V in (t) is the rectified input voltage, typically a constant sinusoidal signal, then iL f (t) is constant, and the output voltage is constant, so that the real-time given expression of the inductance current in the Buck stage can be obtained as follows:
the control method of the AC/DC PFC converter is shown in fig. 5.
In order to verify the feasibility of the average current control method based on instantaneous power conservation of the AC/DC power factor correction converter, a 1KW experimental platform is built, DSP2812 developed based on C language is used for digital control, a DSP program is written, and system software is designed to realize a control algorithm and output two paths of PWM wave signals.
The DSP program mainly includes two parts, a main program design and a timer interrupt service subroutine design, fig. 6 is a flow chart of the main program of the system, and fig. 7 is a flow chart of the timer interrupt service subroutine. FIG. 8 is a schematic block diagram of a system control method, wherein nominal parameters of the AC/DC PFC converter circuit are designed as shown in Table 1.
TABLE 1 nominal parameters of the circuit
| Input filter inductor L f | 400uH |
| Input filter capacitor C f | 2uF |
| Inductor L | 600uH |
| Output capacitor C o | 2000uF |
| Switching frequencyRate of formation | 40kHz |
The main purpose of the invention is to adopt a novel control strategy based on instantaneous power conservation to ensure that the input current of the AC/DC PFC converter has good sine property, and meanwhile, the converter can output stable direct current voltage and has higher power factor, therefore, in order to verify the feasibility of the control strategy, the input current and the output voltage waveform of the converter need to be checked.
Referring to fig. 9, experimental waveforms of input voltage (Ui) and input current (Ii) of an AC/DC PFC converter are shown. The waveform of the converter when working in the pure Boost mode is shown in the left part of fig. 9, and the input voltage is 110V. The waveform of the converter working in the Buck-Boost mode is shown in the right part of the figure 9, and the input voltage is 220V. From the experimental waveforms, the converter input current waveform has good sinusoid in both cases and is in phase with the input voltage.
Judging whether the control strategy of the AC/DC PFC converter is correct needs to see not only the input current characteristic but also the output direct current characteristic. Fig. 10 shows an output voltage waveform of the cascaded Buck-Boost PFC converter during stable operation. The left part of fig. 10 is a waveform when the converter operates in a pure "Boost" mode, and the output voltage is stabilized at 175V. The right part of fig. 10 is a waveform when the converter operates in a Buck-Boost mode, and the output voltage is stabilized at 250V.
Therefore, the novel control method based on instantaneous power conservation for the AC/DC converter is easy to realize, and can effectively improve the input current waveform of the AC/DC converter, so that the power factor is more than 99%.
While the foregoing is directed to embodiments of the present invention, which are more particularly and specifically described herein, it is not intended to limit the scope of the invention. It should be noted that various changes and modifications can be made by those skilled in the art without departing from the spirit of the invention, and these changes and modifications are all within the scope of the invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (6)
- The PFC converter is characterized in that a PFC converter unit is provided with a Buck circuit part based on a Buck power switch tube S1 and a Boost circuit part based on a Boost power switch tube S2, and if one of the Buck circuit part and the Boost circuit part is in a working state, the other one of the Buck circuit part and the Boost circuit part is in a non-working state.
- 2. The PFC converter of claim 1, wherein the one of the Buck circuit portion and the Boost circuit portion to be in operation is determined based on a comparison of an input voltage and an output voltage of the PFC converter.
- The PFC converter system is characterized by comprising an alternating current input unit, a rectifying unit, a filtering unit, a controller unit, a load unit and the PFC converter as claimed in claim 1 or 2, wherein the alternating current input unit, the rectifying unit, the filtering unit, the PFC converter and the load unit are sequentially connected, and the controller unit samples the input voltage and the output voltage of the PFC converter and determines one of the Buck circuit part and the Boost circuit part to be in a working state according to the comparison result of the input voltage and the output voltage of the PFC converter and enables the Buck circuit part and the Boost circuit part to work.
- 4. The PFC converter system of claim 3, wherein the Buck circuit portion is in operation if an input voltage of the PFC converter is greater than the output voltage; and if the input voltage of the PFC converter is less than or equal to the output voltage, the Boost circuit part is in a working state.
- 5. The PFC converter system of claim 3, further comprising a driver unit, the controller unit controlling the PFC converter via the driver unit.
- A PFC converter system method, comprising,modeling and analyzing a Buck circuit part and a Boost circuit part of the PFC converter;analyzing the gain of the open loop of the system; and the number of the first and second groups,and calculating to obtain the control strategy of the PFC converter system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111021688.8A CN115733352A (en) | 2021-09-01 | 2021-09-01 | PFC converter, PFC converter system and method |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111021688.8A CN115733352A (en) | 2021-09-01 | 2021-09-01 | PFC converter, PFC converter system and method |
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| CN115733352A true CN115733352A (en) | 2023-03-03 |
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| CN202111021688.8A Pending CN115733352A (en) | 2021-09-01 | 2021-09-01 | PFC converter, PFC converter system and method |
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