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CN-116317594-B - Resonant converter and control method

CN116317594BCN 116317594 BCN116317594 BCN 116317594BCN-116317594-B

Abstract

The invention discloses a resonant converter and a control method, wherein the resonant converter comprises a primary side inversion switching circuit (II), a primary side resonant cavity (III), a transformer (IV), a secondary side rectifying circuit (V) and a filtering output circuit (VI) which are sequentially connected, the primary side resonant cavity (III) comprises a resonant capacitor, a resonant inductor, an excitation inductor and two switching tubes which are connected in series in an inverse direction, and the secondary side rectifying circuit (V) comprises two power tubes and two switching tubes. In control, PWM control is adopted to regulate the output voltage when the resonant converter outputs low voltage, and phase shift control is adopted to regulate the output voltage when the resonant converter outputs high voltage. Compared with the prior art, the invention obviously reduces the frequency adjusting range, is beneficial to the optimal design of magnetic devices such as transformers, inductors and the like, and improves the power density and the efficiency of the resonant converter.

Inventors

  • LIU SONGLIN
  • LI YONGCHANG
  • WU HUI

Assignees

  • 广州金升阳科技有限公司

Dates

Publication Date
20260512
Application Date
20230222

Claims (9)

  1. 1. The resonant converter is characterized by comprising a primary side inversion switch circuit (II), a primary side resonant cavity (III), a transformer (IV), a secondary side rectifying circuit (V) and a filtering output circuit (VI) which are connected in sequence; The primary inverter switching circuit (II) comprises a primary first switching tube (S 1 ) and a primary second switching tube (S 2 ); The secondary rectifying circuit (V) comprises a first power tube, a second power tube, a secondary fifth switching tube (S 5 ) and a secondary sixth switching tube (S 6 ); The drain electrode of the primary side first switching tube (S 1 ) is used for being electrically connected with the positive end of the direct current input source V in (I), the source electrode of the primary side first switching tube (S 1 ) is connected with the drain electrode of the primary side second switching tube (S 2 ), and the source electrode of the primary side second switching tube (S 2 ) is used for being electrically connected with the negative end of the direct current input source V in (I); The first end of the first power tube is electrically connected with the second end of the second power tube and the same-name end of the secondary winding of the transformer (IV), the source electrode of the secondary fifth switching tube (S 5 ) is electrically connected with the drain electrode of the secondary sixth switching tube (S 6 ) and the different-name end of the secondary winding of the transformer (IV), the second end of the first power tube is electrically connected with the drain electrode of the secondary fifth switching tube (S 5 ), and the first end of the second power tube is electrically connected with the source electrode of the secondary sixth switching tube (S 6 ); When the resonant converter outputs low voltage, PWM control is adopted to adjust the output voltage, and the PWM control is used for adjusting the duty ratio of a primary side switching tube; When the resonant converter outputs high voltage, phase shift control is adopted to adjust the output voltage, a phase shift angle theta exists between a driving pulse of a secondary side fifth switching tube (S 5 ) and a driving pulse of a primary side second switching tube (S 2 ), the same phase shift angle theta exists between the driving pulse of the secondary side sixth switching tube (S 6 ) and the driving pulse of the primary side first switching tube (S 1 ), the value range of the phase shift angle theta is 0 degree less than or equal to 180 degrees, the phase shift control is used for adjusting the phase shift angle theta, wherein the output voltage and the phase shift angle are in positive correlation, the output voltage increases along with the increase of the phase shift angle, the duty ratio of the primary side first switching tube (S 1 ) and the duty ratio of the primary side second switching tube (S 2 ) are 0.5, namely D 1 =1-D 3 =D 2 =1-D 3 =D=0.5, and the duty ratio of the secondary side fifth switching tube (S 5 ) and the secondary side sixth switching tube (S 6 ) is also 0.5, namely D 5 =D 6 =D=0.5.
  2. 2. The resonant converter of claim 1, wherein the first power tube and the second power tube are diodes, the first ends of the first power tube and the second power tube are anodes, and the second ends of the first power tube and the second power tube are cathodes.
  3. 3. The resonant converter of claim 1, wherein the first power tube and the second power tube are MOS tubes, the first ends of the first power tube and the second power tube are drain electrodes, and the second ends are source electrodes.
  4. 4. A resonant converter according to any of claims 1-3, characterized in that the primary side resonant cavity (III) comprises a resonant capacitor (C r ), a primary side third switching tube (S 3 ), a primary side fourth switching tube (S 4 ), a resonant inductance (L r ), an excitation inductance (L m ); One end of a resonance capacitor (C r ) is connected with a source electrode of a primary side first switching tube (S 1 ) and a drain electrode of a primary side second switching tube (S 2 ), the other end of the resonance capacitor (C r ) is electrically connected with a drain electrode of a primary side third switching tube (S 3 ) and one end of a resonance inductor (L r ), the other end of the resonance inductor (L r ) is electrically connected with one end of an excitation inductor (L m ) and a homonymous end of a primary side winding of a transformer (IV), the other end of the excitation inductor (L m ) is electrically connected with a non-homonymous end of the primary side winding of the transformer (IV) and a drain electrode of the primary side fourth switching tube (S 4 ) and a source electrode of the primary side second switching tube (S 2 ), and the source electrode of the primary side third switching tube (S 3 ) is electrically connected with a source electrode of the primary side fourth switching tube (S 4 ).
  5. 5. The resonant converter according to claim 4, wherein the filter output circuit (VI) comprises an output filter capacitor (C o ) and a load (R o ), one end of the output filter capacitor (C o ) is electrically connected to the drain of the secondary side fifth switching tube (S 5 ), the other end of the output filter capacitor (C o ) is electrically connected to the source of the secondary side sixth switching tube (S 6 ), and both ends of the load (R o ) are respectively connected to one end and the other end of the output filter capacitor (C o ).
  6. 6. A control method applied to the resonant converter according to any one of claims 1 to 5, characterized in that the control method comprises: When the resonant converter outputs low voltage, PWM control is adopted to adjust the output voltage, and the PWM control is used for adjusting the duty ratio of a primary side switching tube of the transformer; When the resonant converter outputs high voltage, phase shift control is adopted to adjust output voltage, a phase shift angle theta exists between a driving pulse of a fifth switching tube (S 5 ) on the secondary side and a driving pulse of a second switching tube (S 2 ) on the primary side, the same phase shift angle theta exists between the driving pulse of the sixth switching tube (S 6 ) on the secondary side and the driving pulse of the first switching tube (S 1 ) on the primary side, the value range of the phase shift angle theta is more than or equal to 0 DEG and less than or equal to 180 DEG, the phase shift control is used for adjusting the phase shift angle theta, the output voltage and the phase shift angle are in positive correlation, and the output voltage is increased along with the increase of the phase shift angle.
  7. 7. The control method according to claim 6, wherein when the PWM control is adopted to adjust the output voltage, the driving pulse of the primary first switching tube (S 1 ) is complementary to the driving pulse of the primary third switching tube (S 3 ), the driving pulse of the primary second switching tube (S 2 ) is complementary to the driving pulse of the primary fourth switching tube (S 4 ), the driving pulse of the primary second switching tube (S 2 ) is 180 ° different from the driving pulse of the primary first switching tube (S 1 ), the driving pulse of the primary fourth switching tube (S 4 ) is 180 ° different from the driving pulse of the primary third switching tube (S 3 ), the duty ratio of the driving pulse of the primary first switching tube (S 1 ) is D 1 , the duty ratio of the driving pulse of the primary second switching tube (S 2 ) is D 2 , the duty ratio of the driving pulse of the primary third switching tube (S 3 ) is D 3 , and the duty ratio of the driving pulse of the primary fourth switching tube (S 4 ) is D3742, and D370 is equal to or less than 0. 1 =1-D 3 =D 2 =1-D 3 .
  8. 8. The control method according to claim 6, wherein when the output voltage is regulated by the phase shift control, the duty ratio of the primary side first switching tube (S 1 ) and the primary side second switching tube (S 2 ) is 0.5, that is, D 1 =1-D 3 =D 2 =1-D 3 =d=0.5, and the duty ratio of the secondary side fifth switching tube (S 5 ) and the secondary side sixth switching tube (S 6 ) is also 0.5, that is, D 5 =D 6 =d=0.5.
  9. 9. The control method according to claim 7, wherein the secondary side fifth switching tube (S 5 ) and the secondary side sixth switching tube (S 6 ) are in an off state when the output voltage is regulated using PWM control, and rectifying is performed by body diodes of the secondary side fifth switching tube (S 5 ) and the secondary side sixth switching tube (S 6 ).

Description

Resonant converter and control method Technical Field The invention relates to the technical field of converters, in particular to a resonant converter and a control method thereof. Background In recent years, resonant converters have attracted attention from a large number of students, researchers, and engineering technicians due to their soft switching, high efficiency, high power density, and other properties, and have been increasingly used in engineering applications such as data centers, aerospace power supplies, server power supplies, and vehicle power supplies. The resonant converter comprises a series LC resonant converter, a parallel LC resonant converter, a series-parallel LCC resonant converter, a series-parallel LLC resonant converter, a series-parallel LCLC resonant converter and other structures, and the resonant converters with different structures have different performances and have certain differences in application occasions. While a typical dc converter regulates the output voltage using Pulse Width Modulation (PWM) control, a resonant dc-dc converter regulates the output voltage using Pulse Frequency Modulation (PFM) control. In wide voltage applications, the frequency adjustment range of a resonant converter controlled by a general PFM is wide, the gain adjustment capability is limited, the optimal design of a magnetic device is not facilitated, and the power density of the converter is reduced. Particularly, when the switching frequency is far smaller than the series resonant frequency, a larger circulating current exists on the primary side of the resonant converter, so that the conversion efficiency of the converter is seriously reduced, and the resonant converter easily enters a capacitive region, so that the soft switching performance of the converter is invalid, and the power supply system is unstable in operation. In order to overcome the defect of PFM control, the voltage regulation capability of the resonant converter is improved, the frequency regulation range is reduced, and various improvement schemes are researched by students and technicians in the field. Researchers Li Ju and Ruan Xinbo at university of aviation aerospace in south Beijing issue paper on hybrid control strategy of full bridge LLC resonant converter in 2013, and propose a frequency conversion-phase shift hybrid control strategy which can reduce the frequency adjustment range. However, in the phase-shifting control mode, the soft switching performance of the primary side switching tube is limited, and in order to ensure the efficiency performance of the converter, the gain adjustment capability of the resonant converter under the control of the hybrid control strategy is limited. In addition, the inventors of the university of aviation aerospace in south Beijing, wu Gongfei, sun Wenjin, ge Gongjuan, xing Yan and the like apply for 2016 for China patent on a resonant converter and a control method thereof, and the invention discloses a resonant converter of a secondary side active Boost rectifying circuit, which adjusts output voltage by adopting fixed frequency phase shift control or frequency-phase shift mixed control. However, the secondary side of the resonant converter disclosed in this invention requires two auxiliary active switching tubes, which increases circuit design costs and control complexity. Disclosure of Invention The invention aims to overcome the defects of the prior art, and provides a resonant converter and a control method thereof, which effectively reduce the frequency adjustment range of the resonant converter under PFM control, are beneficial to optimizing the design of a transformer, and improve the voltage adjustment capability of the resonant converter, so that the resonant converter is suitable for wide-voltage application occasions and improves the conversion efficiency and the power density of a resonant power supply system. The aim of the invention is realized by the following technical scheme: In a first aspect, a resonant converter is provided, the resonant converter includes a primary side inversion switch circuit (II), a primary side resonant cavity (III), a transformer (IV), a secondary side rectifying circuit (V) and a filtering output circuit (VI) connected in sequence; The primary inverter switching circuit (II) comprises a primary first switching tube (S 1) and a primary second switching tube (S 2); The secondary rectifying circuit (V) comprises a first power tube, a second power tube, a secondary fifth switching tube (S 5) and a secondary sixth switching tube (S 6); The drain electrode of the primary side first switching tube (S 1) is used for being electrically connected with the positive end of the direct current input source V in (I), the source electrode of the primary side first switching tube (S 1) is connected with the drain electrode of the primary side second switching tube (S 2), and the source electrode of the primary side second switching tube (S 2) is u