A resonant converter and its control method

Abstract

This invention relates to a resonant converter and its control method, wherein the resonant converter includes a DC input source V. in (I) Primary-side two-phase symmetrical half-bridge inverter circuit (II) Series resonant branch (III) Transformer (IV) Secondary-side rectifier circuit (V) and filter output circuit (VI); Compared with a general two-phase half-bridge LLC resonant converter, the two-phase symmetrical half-bridge LLC resonant converter of this invention shares a series resonant branch, reducing the number of resonant components; In terms of control, based on the voltage gain boost / buck adjustment, a fixed-frequency phase-shift hybrid control method is disclosed and applied to the resonant converter. The control method can improve the gain adjustment capability of the resonant converter, and the switching frequency is equal to the series resonant frequency, narrowing the frequency adjustment range, which is beneficial for the optimized design of magnetic components such as transformers and improves the overall power density.

Description

Technical Field

[0001] This invention relates to the field of converter technology, and in particular to a resonant converter and its control method. Background Technology

[0002] Power electronic converters play an important role in power conversion. Among them, isolated DC-DC converters can achieve electrical isolation and convert one DC voltage into another, making them widely used in engineering applications.

[0003] In applications such as DC microgrids, data centers, server power supplies, energy storage systems, new energy power generation systems, on-board chargers, aerospace power supplies, special power supplies, and medical power supplies, the application requirements for DC-DC converters include wide input / output voltage regulation capabilities, high conversion efficiency, and high power density. The development of LLC resonant converters has brought new vitality to the development of DC converters. Due to their inherent soft-switching characteristics and relatively simple structure, LLC resonant converters have become the preferred topology for industrial power supply products.

[0004] Generally speaking, LLC resonant converters use frequency conversion control to regulate the output voltage, and their voltage gain is related to parameters such as switching frequency, resonant inductance, magnetizing inductance, and resonant capacitor. Simple frequency conversion control is difficult to achieve wide gain adjustment, and the large adjustment range of the switching frequency is not conducive to the design of magnetic devices such as transformers and inductors. It also generates a large circulating current, which reduces the conversion efficiency, making LLC resonant converters unsuitable for wide voltage applications.

[0005] To improve the gain regulation performance and narrow the frequency regulation range of LLC resonant converters, experts, scholars, and inventors both domestically and internationally have proposed various improvement methods. Among them, the patent application "A Wide Input Range LLC Resonant Converter with Shared Resonant Inductor" filed by Nanjing University of Aeronautics and Astronautics discloses a two-phase resonant converter with a shared resonant inductor, which uses a dynamic adjustment topology to broaden the converter's input voltage range. However, this scheme involves a multi-level frequency control process, and the control process of dynamically adjusting the topology through switching is complex, hindering control simplification. Furthermore, inventors Wang Haoyu and Li Zhiqing from ShanghaiTech University disclosed a two-phase resonant converter topology in their patent application "A Resonant Isolation Converter with Ultra-Wide Voltage Regulation Range." The primary-side switching transistor uses phase-shift control to regulate the output voltage, significantly narrowing the frequency regulation range. This topology connects two half-bridge resonant converters through two transformers, resulting in a complex circuit structure, numerous resonant components, and increased circuit design costs. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a resonant converter and its control method for wide voltage applications, enabling it to achieve wide gain adjustment while retaining the advantages of LLC resonant converters.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, a resonant converter is provided, characterized in that it includes a DC input source V connected in sequence. in (I) Primary two-phase symmetrical half-bridge inverter circuit (II) Series resonant branch (III) Transformer (IV) Secondary rectifier circuit (V) and filter output circuit (VI);

[0009] The primary-side two-phase symmetrical half-bridge inverter circuit (II) includes the primary-side first switch (S1), the primary-side second switch (S2), the primary-side third switch (S3), the primary-side fourth switch (S4), the primary-side first voltage divider capacitor (C1), and the primary-side second voltage divider capacitor (C2);

[0010] The series resonant branch (Ⅲ) includes the resonant capacitor (C). r ), resonant inductor (L) r ), first magnetizing inductor (L m1 ), second magnetizing inductor (L m2 );

[0011] The transformer (Ⅳ) includes the first transformer (T1) and the second transformer (T2);

[0012] The drain of the first primary-side switching transistor (S1) is connected to the DC input source V. in (Ⅰ) The positive terminal, the source of the first primary-side switch (S1) is connected to the drain of the second primary-side switch (S2) and the first magnetizing inductor (L) m1 One end of the primary side of the first transformer (T1) is connected to the same terminal on the primary side of the first transformer (T1), with the connection point being A; the drain of the third primary-side switch (S3) and one end of the first primary-side voltage divider capacitor (C1) are simultaneously connected to the drain of the first primary-side switch (S1) and the DC input source V. in (Ⅰ) The positive terminal; the source of the fourth primary-side switch (S4) and one end of the second primary-side voltage divider capacitor (C2) are simultaneously connected to the source of the second primary-side switch (S2) and the DC input source V. in (Ⅰ) The negative terminal; the source of the third primary-side switch (S3) is connected to the drain of the fourth primary-side switch (S4) and the second primary-side magnetizing inductor (L m2 One end of the primary side of the transformer (T1) is connected to the non-identical terminal of the primary side of the second primary side transformer (T2), with the connection point being B; the other end of the primary side first voltage divider capacitor (C1) is connected to the other end of the primary side second voltage divider capacitor (C2) and the resonant capacitor (C1). r One end of the connection is C;

[0013] Resonant capacitor (C) r The other end is connected to the resonant inductor (L). r One end of the resonant inductor (L) r The other end is connected to the first magnetizing inductor (L) m1 At the other end of the second magnetizing inductor (L) m2 The other end of the transformer (T1), the non-same-name terminal on the primary side of the first transformer (T1), and the same-name terminal on the primary side of the second transformer (T2) are connected at point N.

[0014] The secondary side terminal of the first transformer (T1) is connected to the secondary side terminal of the second transformer (T2); the secondary side terminals of the first transformer (T1) and the second transformer (T2) are both connected to the secondary rectifier circuit (V).

[0015] Preferably, the secondary-side rectifier circuit (V) includes a secondary-side first rectifier diode (D1), a secondary-side second rectifier diode (D2), a secondary-side fifth switch (S5), and a secondary-side sixth switch (S6);

[0016] The non-same-name terminal on the secondary side of the first transformer (T1) is connected to the anode of the first rectifier diode (D1) and the cathode of the second rectifier diode (D2) on the secondary side, and the connection point is X; the non-same-name terminal on the secondary side of the second transformer (T2) is connected to the source of the fifth switch (S5) and the drain of the sixth switch (S6) on the secondary side, and the connection point is Y.

[0017] The cathode of the first rectifier diode (D1) on the secondary side is connected to the drain of the fifth switch (S5) on the secondary side and then connected to the filter output circuit (VI); the anode of the second rectifier diode (D2) on the secondary side is connected to the source of the sixth switch (S6) on the secondary side and then connected to the filter output circuit (VI).

[0018] Preferably, the secondary-side rectifier circuit (V) includes a secondary-side first rectifier diode (D1), a secondary-side second rectifier diode (D2), a secondary-side fifth switch (S5), and a secondary-side sixth switch (S6);

[0019] The non-same-name terminal on the secondary side of the first transformer (T1) is connected to the anode of the first rectifier diode (D1) on the secondary side and the drain of the fifth switch (S5) on the secondary side, and the connection point is X; the non-same-name terminal on the secondary side of the second transformer (T2) is connected to the anode of the second rectifier diode (D2) on the secondary side and the drain of the sixth switch (S6) on the secondary side, and the connection point is Y.

[0020] The cathode of the first rectifier diode (D1) on the secondary side is connected to the cathode of the second rectifier diode (D2) on the secondary side, and then connected to the filter output circuit (VI); the source of the fifth switch (S5) on the secondary side is connected to the source of the sixth switch (S6) on the secondary side, and then connected to the filter output circuit (VI).

[0021] Preferably, the secondary-side rectifier circuit (V) includes a secondary-side first rectifier diode (D1), a secondary-side second rectifier diode (D2), a secondary-side fifth switch (S5), and a secondary-side sixth switch (S6);

[0022] The non-same-name terminal on the secondary side of the first transformer (T1) is connected to the cathode of the first rectifier diode (D1) on the secondary side and the source of the fifth switch (S5) on the secondary side, and the connection point is X; the non-same-name terminal on the secondary side of the second transformer (T2) is connected to the cathode of the second rectifier diode (D2) on the secondary side and the source of the sixth switch (S6) on the secondary side, and the connection point is Y.

[0023] The anode of the first rectifier diode (D1) on the secondary side is connected to the anode of the second rectifier diode (D2) on the secondary side, and then connected to the filter output circuit (VI); the drain of the fifth switch (S5) on the secondary side is connected to the drain of the sixth switch (S6) on the secondary side, and then connected to the filter output circuit (VI).

[0024] Preferably, the secondary-side rectifier circuit (V) includes a secondary-side first rectifier diode (D1), a secondary-side second rectifier diode (D2), a secondary-side third rectifier diode (D3), a secondary-side fourth rectifier diode (D4), a secondary-side fifth switch (S5), and a secondary-side sixth switch (S6);

[0025] The non-same-name terminal on the secondary side of the first transformer (T1) is connected to the anode of the first rectifier diode (D1), the drain of the fifth switch (S5), and the cathode of the second rectifier diode (D2), with connection point X; the non-same-name terminal on the secondary side of the second transformer (T2) is connected to the anode of the third rectifier diode (D3), the drain of the sixth switch (S6), and the cathode of the fourth rectifier diode (D4), with connection point Y; the source of the fifth switch (S5) is connected to the source of the sixth switch (S6); the cathode of the first rectifier diode (D1) is connected to the cathode of the third rectifier diode (D3) and then connected to the filter output circuit (VI); the anode of the third rectifier diode (D3) is connected to the anode of the fourth rectifier diode (D4) and then connected to the filter output circuit (VI).

[0026] Preferably, the filter output circuit (VI) includes output filter capacitors (C) connected in parallel. o ) and load (R o ).

[0027] Secondly, a control method for a resonant converter is provided, which is divided into a gain buck regulation stage and a gain boost regulation stage according to the gain regulation capability:

[0028] During the gain-down adjustment stage, the duty cycles of the drive pulses for the primary-side first switch (S1), second switch (S2), third switch (S3), and fourth switch (S4) are all 0.5 (ignoring dead time). Furthermore, the drive pulses for the primary-side first switch (S1) and second switch (S2) are complementary, as are the drive pulses for the primary-side third switch (S3) and fourth switch (S4). The switching frequency is equal to the series resonant frequency. Moreover, the primary-side fourth switch… The driving pulse of the primary-side switch (S4) controls the phase shift of the driving pulse of the primary-side first switch (S1), and the driving pulse of the primary-side third switch (S3) controls the phase shift of the driving pulse of the primary-side second switch (S2). The primary-side third switch (S3) and the primary-side fourth switch (S4) have the same phase shift angle relative to the primary-side second switch (S2) and the primary-side first switch (S1), respectively. The secondary-side fifth switch (S5) and the secondary-side sixth switch (S6) perform rectification.

[0029] During the gain boost regulation stage, the phase shift angles of the primary-side third switch (S3) and the primary-side fourth switch (S4) relative to the primary-side second switch (S2) and the primary-side first switch (S1) are 180°, respectively. This means the drive pulses of the primary-side first switch (S1) and the third switch (S3) are the same, and their duty cycles are both 50% (ignoring dead time). The drive pulses of the primary-side second switch (S2) and the primary-side fourth switch (S4) are also the same, and their duty cycles are both 50% (ignoring dead time). The drive pulse of the secondary-side fifth switch (S5) is the same as that of the secondary-side sixth switch (S6). The drive pulses are complementary; the duty cycle of the drive pulse of the fifth switch (S5) on the secondary side is 50% (ignoring dead time), and it is phase-shifted relative to the first switch (S1) and the third switch (S3) on the primary side; the duty cycle of the drive pulse of the sixth switch (S6) on the secondary side is 50% (ignoring dead time), and it is phase-shifted relative to the second switch (S2) and the fourth switch (S4) on the primary side; the fifth switch (S5) and the sixth switch (S6) on the secondary side have the same phase-shift angle relative to the first switch (S1) and the second switch (S2) on the primary side, respectively.

[0030] Preferably, during the gain-down adjustment stage,

[0031] The fifth and sixth secondary-side switches (S5 and S6) use their own body diodes for rectification, or they can be used as synchronous rectifiers.

[0032] Preferably, during the gain reduction adjustment stage, the gain adjustment range of the resonant converter is [0, 1].

[0033] Preferably, during the gain boost adjustment stage, the gain of the resonant converter is greater than 1; within the preset gain adjustment range, the voltage gain increases with the increase of the phase shift angle.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] The described resonant converter topology consists of two symmetrical half-bridge LLC resonant converters sharing a series resonant branch. This significantly reduces the number of resonant components in the two-phase resonant converter, improving converter performance and reducing circuit design costs. In terms of control, it includes phase-shift control during both the gain-down and gain-up adjustment stages, significantly enhancing the resonant converter's gain regulation capability and enabling it to achieve ultra-wide voltage regulation. The resonant converter always operates at a fixed switching frequency, effectively narrowing the frequency adjustment range. The control method is simple and easy to implement, facilitating the design of magnetic components, reducing transformer size, and increasing system power density. Attached Figure Description

[0036] Figure 1 This is a resonant isolation converter with an ultra-wide voltage regulation range disclosed in the prior art;

[0037] Figure 2 This is a structural diagram of a resonant converter disclosed in this invention;

[0038] Figure 3 This is a steady-state waveform diagram of the resonant converter in the gain reduction adjustment stage in this embodiment;

[0039] Figure 4 This is the steady-state waveform of the resonant converter in the gain boost adjustment stage in this embodiment;

[0040] Figure 5 a- Figure 5 b is another structural diagram of the resonant converter described in this embodiment. Detailed Implementation

[0041] The technical solution of the present invention will now be described with reference to the accompanying drawings and embodiments to enable those skilled in the art to better understand the invention. However, the specific implementation of the technical solution of the present invention is not limited thereto.

[0042] To improve the gain adjustment capability of the resonant converter and narrow the frequency adjustment range Figure 1 This paper demonstrates a resonant isolation converter topology with an ultra-wide voltage regulation range disclosed in the prior art. This resonant converter is composed of a two-phase half-bridge LLC resonant converter, which includes two-phase resonant cavities and involves a large number of resonant components, thus increasing the design cost.

[0043] To address the aforementioned problems, this embodiment discloses a resonant converter topology, such as... Figure 2 As shown, it consists of two symmetrical half-bridge LLC resonant converters, with the two resonant cavities sharing a single series resonant branch, which significantly reduces the number of resonant components.

[0044] like Figure 2 As shown, the resonant converter includes a DC input source V. in (I) Primary two-phase symmetrical half-bridge inverter circuit (II) Series resonant branch (III) Two-phase transformer (IV) Secondary rectifier circuit (V) and filter output circuit (VI);

[0045] In a specific implementation of this embodiment, the preferred implementation structure is as follows:

[0046] The primary-side two-phase symmetrical half-bridge inverter circuit (II) includes the primary-side first switch (S1), the primary-side second switch (S2), the primary-side third switch (S3), the primary-side fourth switch (S4), the primary-side first voltage divider capacitor (C1), and the primary-side second voltage divider capacitor (C2);

[0047] The primary side series resonant branch (Ⅲ) includes the resonant capacitor (C). r ), resonant inductor (L) r ), first magnetizing inductor (L m1 ), second magnetizing inductor (L m2 )include;

[0048] The transformer (Ⅳ) includes a first transformer (T1) and a second transformer (T2), and a first magnetizing inductor (L). m1 ) and second excitation inductor (L m2 Let n and n' be the primary-side magnetizing inductances of the first transformer (T1) and the second transformer (T2), respectively; the turns ratio of the first transformer (T1) and the second transformer (T2) are the same, i.e., n = n1 = n2 = N. p :N s ;

[0049] Where n represents the turns ratio of the transformer; n1 is the turns ratio of the first transformer (T1), and n2 is the turns ratio of the second transformer (T2); N p N represents the number of turns in the primary winding of a transformer. s This indicates the number of turns in the secondary winding of the transformer; specifically, the turns ratio n of the transformer can be determined by the input voltage V. in and output voltage V o Sure, Where V in DC input source V in (Ⅰ) Voltage value, V o For load (R) o The output voltage value;

[0050] The secondary rectifier circuit (V) includes the first secondary rectifier diode (D1), the second secondary rectifier diode (D2), the fifth secondary switch (S5), and the sixth secondary switch (S6);

[0051] The secondary-side filter output circuit (VI) consists of the output filter capacitor (C). o ) and load (R o )composition;

[0052] In the specific implementation of this embodiment, the connection relationships of each part are as follows:

[0053] The drain of the first primary-side switch (S1) of the two-phase symmetrical half-bridge inverter circuit (II) is connected to the DC input source V. in (Ⅰ) The positive terminal, the source of the primary side first switch (S1) is connected to the drain of the primary side second switch (S2) and the first magnetizing inductor (L). m1 One end of the primary side switch (S3) is connected to point A; the drain of the primary side third switch (S3) and one end of the primary side first voltage divider capacitor (C1) are simultaneously connected to the drain of the primary side first switch (S1) and the DC input source V. in (Ⅰ) The positive terminal; the source of the fourth primary-side switch (S4) and one end of the second primary-side voltage divider capacitor (C2) are simultaneously connected to the source of the second primary-side switch (S2) and the DC input source V. in (Ⅰ) The negative terminal; the source of the third primary-side switch (S3) is connected to the drain of the fourth primary-side switch (S4) and the second primary-side magnetizing inductor (L). m2 One end of the primary side is connected to point B; the other end of the primary side first voltage divider capacitor (C1) is connected to the other end of the primary side second voltage divider capacitor (C2) and the resonant capacitor (C). r One end of the connection is C;

[0054] The resonant capacitance (C) of the primary side series resonant branch (Ⅲ) r The other end is connected to the resonant inductor (L). r One end of the resonant inductor (L) r The other end is connected to the first magnetizing inductor (L) m1 The other end of the second magnetizing inductor (L) m2 The other end of the connection is point N;

[0055] The primary side terminal of the first transformer (T1) is connected to the first magnetizing inductor (L). m1 One end of the primary side of the first transformer (T1) is connected to the non-identical terminal of the first magnetizing inductor (L). m1 The other end of the second transformer (T2) is connected to the primary side of the second magnetizing inductor (L). m2 The other end of the resonant inductor (L) rThe other end of the transformer (T1) and the non-same-name terminal on the primary side of the first transformer (T1) are connected at point N; the non-same-name terminal on the primary side of the second transformer (T2) is connected to the second magnetizing inductor (L). m2 One end of the transformer (T1); the non-same-name terminal on the secondary side of the first transformer (T1) is connected to the anode of the first rectifier diode (D1) and the cathode of the second rectifier diode (D2) on the secondary side, with connection point X; the non-same-name terminal on the secondary side of the second transformer (T2) is connected to the source of the fifth switch (S5) and the drain of the sixth switch (S6) on the secondary side, with connection point Y; the same-name terminal on the secondary side of the first transformer (T1) is connected to the same-name terminal on the secondary side of the second transformer (T2);

[0056] The anode of the first rectifier diode (D1) of the secondary side rectifier bridge arm (V) is connected to the cathode of the second rectifier diode (D2); the source of the fifth switch (S5) on the secondary side is connected to the drain of the sixth switch (S6) on the secondary side; the cathode of the first rectifier diode (D1) on the secondary side is connected to the drain of the fifth switch (S5) on the secondary side; and the anode of the second rectifier diode (D2) on the secondary side is connected to the source of the sixth switch (S6) on the secondary side.

[0057] The output capacitor (C) in the filter output circuit (VI) o One end of the transistor is connected to the drain of the fifth switching transistor (S5) on the secondary side and the output load (R). o One end of the capacitor; the output capacitor (C) o The other end is connected to the source of the sixth switch (S6) on the secondary side and the output load (R). o The other end of ).

[0058] In this embodiment, a control method for a resonant converter is disclosed. The resonant converter can achieve ultra-wide output voltage regulation, thereby improving the gain regulation capability of the resonant converter. The specific control method is as follows:

[0059] During the gain-down adjustment stage, the fifth and sixth secondary-side switches (S5 and S6) act as synchronous rectifiers to improve system efficiency. The two-phase symmetrical half-bridge inverter circuit (II) on the primary side uses phase-shift control to regulate the output voltage. Specifically, the duty cycles of the drive pulses for the first and second primary-side switches (S1 and S2) are each 0.5 (ignoring dead time), and their drive pulses are complementary, with the switching frequency equal to the series resonant frequency. The duty cycles of the drive pulses for the third and fourth primary-side switches (S3 and S4) are each 0.5 (ignoring dead time). (Slight dead time), and the drive pulses of the primary side third switch (S3) and the primary side fourth switch (S4) are complementary, and the switching frequency is equal to the series resonant frequency; the drive pulse of the primary side fourth switch (S4) performs phase shift control on the drive pulse of the primary side first switch (S1); the drive pulse of the primary side third switch (S3) performs phase shift control on the drive pulse of the primary side second switch (S2); the primary side third switch (S3) and the primary side fourth switch (S4) have the same phase shift angle relative to the primary side second switch (S2) and the primary side first switch (S1), respectively, and the gain reduction adjustment can be achieved by adjusting the phase shift angle. Specifically, in the gain-down adjustment stage, the phase-shift control used is primary-side phase-shift control, which directly shifts the phase of the primary-side switching transistor. The voltage gain and output voltage increase with the increase of the phase shift angle. When the phase shift angle is 0°, the resonant converter gain is at its minimum of 0; when the phase shift angle is 180°, the resonant converter gain is at its maximum of 1. Since the maximum gain of the resonant converter is 1, this phase-shift control mode is the gain-down adjustment stage. Therefore, when the output voltage is less than the rated output voltage of the resonant converter, if the output voltage needs to be adjusted, the gain-down adjustment stage is entered for adjustment. The normalized voltage gain of the resonant converter is described as follows:

[0060]

[0061] When the phase shift angle of the two symmetrical half-bridge inverter circuits (II) on the primary side is 180°, the resonant converter enters the gain boost adjustment stage: the driving pulses of the first switch (S1) and the third switch (S3) on the primary side are the same, and their duty cycles are both 50% (ignoring dead time); the driving pulses of the second switch (S2) and the fourth switch (S4) on the primary side are the same, and their duty cycles are both 50% (ignoring dead time); the fifth switch of the secondary side rectifier circuit (V)... The drive pulse of the secondary-side switch (S5) is complementary to the drive pulse of the sixth secondary-side switch (S6); the duty cycle of the drive pulse of the fifth secondary-side switch (S5) is 50% (ignoring dead time), and it is phase-shifted relative to the first primary-side switch (S1) and the third primary-side switch (S3); the duty cycle of the drive pulse of the sixth secondary-side switch (S6) of the secondary-side half-bridge rectifier circuit (V) is 50% (ignoring dead time), and it is phase-shifted relative to the second primary-side switch (S2) The primary side switch (S4) and the secondary side switch (S5) and the secondary side switch (S6) are phase-shifted. The secondary side switch (S5) and the secondary side switch (S6) have the same phase shift angle relative to the primary side switch (S1) and the primary side switch (S2), respectively. Gain boost regulation is achieved by adjusting the phase shift angle of the secondary side switch (S5) and the secondary side switch (S6). Specifically, in the gain boost regulation stage, the phase shift control used is secondary side phase shift control, that is, the switch on the secondary side is phase-shifted relative to the switch on the primary side. At this time, the gain of the resonant converter is greater than 1. And within the preset gain adjustment range, the voltage gain and the output voltage increase with the increase of the phase shift angle. The resonant converter achieves gain boost regulation. The preset gain adjustment range is (1, 2.5]. Therefore, when the output voltage is greater than the rated output voltage of the resonant converter, if the output voltage needs to be adjusted, the gain boost regulation stage is entered for adjustment.

[0062] During the aforementioned gain buck and gain boost adjustment stages, the primary-side switches S1-S4 and secondary-side switches S5 and S6 of the converter operate at a constant frequency, and the switching frequency is equal to the series resonant frequency. The control method described in this embodiment effectively narrows the frequency adjustment range, which is beneficial for optimizing the design of magnetic components such as transformers and inductors, reducing the size of magnetic components, and increasing the power density of the resonant converter.

[0063] Figure 3 The steady-state waveform of the resonant converter in the preferred embodiment during the gain reduction adjustment stage; Figure 3 In the middle, V gs4 and V gs1 V represents the drive pulses of the fourth primary-side switch (S4) and the first primary-side switch (S1), respectively. gs4 and V gs1 There is a phase shift difference between them, with a phase shift angle of θ; V gs3 and Vgs2 V represents the drive pulses of the third primary-side switch (S3) and the second primary-side switch (S2), respectively. gs3 and V gs2 There is a phase shift difference between them, with a phase shift angle of θ; the duty cycle of the driving pulses of the first switch (S1) and the second switch (S2) on the primary side is 0.5 (ignoring dead time), and the driving pulses of the first switch (S1) and the second switch (S2) on the primary side are complementary, and the switching frequency is equal to the series resonant frequency of 100kHz; the duty cycle of the driving pulses of the third switch (S3) and the fourth switch (S4) on the primary side is 0.5 (ignoring dead time), and the driving pulses of the third switch (S3) and the fourth switch (S4) on the primary side are complementary, and the switching frequency is equal to the series resonant frequency of 100kHz;

[0064] exist Figure 3 In the middle, the output voltage V of the two symmetrical half-bridge inverter circuits (Ⅱ) on the primary side is... AC and V BC These are square wave voltages with amplitudes of ±200V. The fourth primary-side switch (S4) and the third primary-side switch (S3) have the same phase shift angle θ relative to the first primary-side switch (S1) and the second primary-side switch (S2), respectively, resulting in the output voltage V of the two symmetrical half-bridge inverter circuits (Ⅱ) on the primary side. AC With V BC There is a phase shift angle of (180° - θ). The output voltage is adjusted by adjusting the phase shift angle θ. At this time, the output voltage of the converter is 29V, which is significantly lower than the rated output voltage, thus realizing gain reduction regulation.

[0065] Specifically, when the phase shift angle θ is 0°, the output voltage of the resonant converter is 0, and the voltage gain is minimum; when the phase shift angle θ is 180°, the rated output voltage of the resonant converter is 48V, and the voltage gain is maximum, which is 1.

[0066] Figure 3 In the embodiment, i D1 i D2 The waveforms represent the current flowing through the first rectifier diode (D1) and the second rectifier diode (D2) on the secondary side, respectively. When the rectifier diodes are turned off, the current flowing through them drops to 0. The secondary-side rectifier diodes of the converter described in this invention achieve ZCS turn-off, which can reduce the reverse recovery loss of the rectifier diodes and improve the overall efficiency of the converter. The fifth and sixth switches on the secondary side (S5 and S6) utilize their body diodes to achieve diode rectification. To further improve the conversion efficiency, the fifth and sixth switches on the secondary side (S5 and S6) can employ synchronous rectification control to reduce rectification losses.

[0067] Figure 4This is the steady-state waveform of the resonant converter in the gain boost adjustment stage in this embodiment; Figure 4 In the middle, V gs5 and V gs6 These represent the drive pulses for the fifth secondary switch (S5) and the sixth secondary switch (S6), respectively, with a switching frequency equal to the series resonant frequency of 100kHz; V gs1 V gs2 V gs3 V gs4 These represent the driving pulses of the primary-side first switch (S1), primary-side second switch (S2), primary-side third switch (S3), and primary-side fourth switch (S4), respectively, with the switching frequency equal to the series resonant frequency of 100kHz. When the phase shift angles of the primary-side fourth switch (S4) and primary-side third switch (S3) relative to the primary-side first switch (S1) and primary-side second switch (S2) are 180°, the driving pulses of the primary-side second switch (S2) and primary-side fourth switch (S4) are the same, and the driving pulses of the primary-side first switch (S1) and primary-side third switch (S3) are also the same. The fifth secondary switch (S5) is phase-shifted relative to the first primary switch (S1) and the third primary switch (S3) with a phase shift angle of θ; the sixth secondary switch (S6) is phase-shifted relative to the second primary switch (S2) and the fourth primary switch (S4) with a phase shift angle of θ. The fifth and sixth secondary switches (S5 and S6) have the same phase shift angle θ relative to the first primary switch (S1) and the second primary switch (S2), respectively. The output voltage is adjusted by adjusting the phase shift angle θ. At this time, the output voltage of the converter is 59V, which is significantly higher than the rated output voltage, thus achieving gain boost regulation.

[0068] Figure 4 In the circuit, when the phase shift angles of the fourth primary-side switch (S4) and the third primary-side switch (S3) relative to the first primary-side switch (S1) and the second primary-side switch (S2) are 180° respectively, the output voltage V of the two-phase symmetrical half-bridge inverter circuit (II) on the primary side is... AC With V BC There is a phase shift angle of 0° (180°-180°=0°). At this time, the voltage utilization rate of the resonant cavity to the two-phase symmetrical half-bridge inverter circuit on the primary side is the highest. Furthermore, the output voltage is adjusted by the phase shift angle of the fifth switch (S5) and the sixth switch (S6) on the secondary side, so that the resonant converter can achieve gain boost regulation. Figure 4 In the embodiment, i D1 i D2The waveforms represent the current flowing through the first secondary rectifier diode (D1) and the second secondary rectifier diode (D2), respectively. When the rectifier diodes are turned off, the current flowing through the diodes drops to 0. The secondary rectifier diodes of the converter described in this invention achieve ZCS turn-off, which can reduce the reverse recovery loss of the rectifier diodes and improve the overall efficiency of the converter.

[0069] In another embodiment, the secondary-side rectifier circuit (V) can also have other implementations, such as... Figure 5 As shown, Figure 5 In another embodiment of the resonant converter topology described in this example, the fifth secondary switch (S5) and the sixth secondary switch (S6) of the secondary rectifier circuit (V) can be electrically connected to the left bridge arm of the rectifier circuit (not shown in the figure); as Figure 5 As shown in (a), the secondary fifth switch (S5) and the secondary sixth switch (S6) of the secondary rectifier circuit (V) can also be electrically connected to the two lower or upper bridge arms of the rectifier circuit. Specifically, the secondary rectifier circuit (V) includes the secondary first rectifier diode (D1), the secondary second rectifier diode (D2), the secondary fifth switch (S5), and the secondary sixth switch (S6).

[0070] The non-same-name terminal on the secondary side of the first transformer (T1) is connected to the anode of the first rectifier diode (D1) on the secondary side and the drain of the fifth switch (S5) on the secondary side, and the connection point is X; the non-same-name terminal on the secondary side of the second transformer (T2) is connected to the anode of the second rectifier diode (D2) on the secondary side and the drain of the sixth switch (S6) on the secondary side, and the connection point is Y.

[0071] The cathode of the first rectifier diode (D1) on the secondary side is connected to the cathode of the second rectifier diode (D2) on the secondary side, and then connected to the filter output circuit (VI); the source of the fifth switch (S5) on the secondary side is connected to the source of the sixth switch (S6) on the secondary side, and then connected to the filter output circuit (VI).

[0072] Alternatively, the non-same-name terminal on the secondary side of the first transformer (T1) is connected to the cathode of the first rectifier diode (D1) on the secondary side and the source of the fifth switch (S5) on the secondary side, with the connection point being X; the non-same-name terminal on the secondary side of the second transformer (T2) is connected to the cathode of the second rectifier diode (D2) on the secondary side and the source of the sixth switch (S6) on the secondary side, with the connection point being Y;

[0073] The anode of the first rectifier diode (D1) on the secondary side is connected to the anode of the second rectifier diode (D2) on the secondary side, and then connected to the filter output circuit (VI); the drain of the fifth switch (S5) on the secondary side is connected to the drain of the sixth switch (S6) on the secondary side, and then connected to the filter output circuit (VI). Figure 5 (Not shown in the image).

[0074] like Figure 5 As shown in (b), the fifth switch (S5) and the sixth switch (S6) of the secondary rectifier circuit (V) can also be electrically connected back-to-back to the input terminal of the rectifier bridge. Specifically, the secondary rectifier circuit (V) includes the first rectifier diode (D1), the second rectifier diode (D2), the third rectifier diode (D3), the fourth rectifier diode (D4), the fifth switch (S5), and the sixth switch (S6).

[0075] The non-same-name terminal on the secondary side of the first transformer (T1) is connected to the anode of the first rectifier diode (D1), the drain of the fifth switch (S5), and the cathode of the second rectifier diode (D2), with connection point X; the non-same-name terminal on the secondary side of the second transformer (T2) is connected to the anode of the third rectifier diode (D3), the drain of the sixth switch (S6), and the cathode of the fourth rectifier diode (D4), with connection point Y; the source of the fifth switch (S5) is connected to the source of the sixth switch (S6); the cathode of the first rectifier diode (D1) is connected to the cathode of the third rectifier diode (D3) and then connected to the filter output circuit (VI); the anode of the third rectifier diode (D3) is connected to the anode of the fourth rectifier diode (D4) and then connected to the filter output circuit (VI).

[0076] Other topological implementations of the resonant converter are similar to this embodiment. Figure 2 The topology in the above has a similar effect, and its control method still adopts the control method described in this application, which can improve the gain adjustment capability of the resonant converter. The specific implementation method will not be repeated here, but can be referred to the above embodiments.

[0077] In particular, when it is necessary to improve the overall efficiency of the resonant converter, the diodes in the secondary rectifier circuit (V) of the resonant converter can be replaced with active switching transistors to achieve synchronous rectification and reduce the loss of the rectifier circuit.

[0078] Through the above embodiments, the resonant converter of the present invention shares a resonant series branch with two symmetrical half-bridge LLC resonant converters, effectively reducing resonant components and facilitating circuit design optimization. This embodiment discloses a control method applied to the resonant converter; in the gain-down adjustment stage, the switching frequency of the resonant converter is equal to the series resonant frequency, and the output voltage is adjusted by controlling the phase shift angle of the primary-side switch to achieve down-voltage adjustment; in the gain-up adjustment stage, the switching frequency of the resonant converter is equal to the series resonant frequency, and the output voltage is adjusted by controlling the phase shift angle of the secondary-side switch to achieve up-voltage adjustment; the control method significantly improves the gain adjustment capability of the resonant converter and is applicable to wide-voltage applications; during gain adjustment, the resonant converter continuously operates at the series resonant frequency point, and the switching frequency is equal to the series resonant frequency, significantly narrowing the switching frequency range, which can optimize the design of magnetic components, reduce the transformer size, and improve the overall power density and efficiency.

[0079] The embodiments described above are merely illustrative examples of the technical solutions and content of the present invention. It should be noted that the above embodiments should not be considered as limitations on the present invention. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, but these will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims, and should also be considered within the protection scope of the present invention.

Claims

1. A resonant converter, characterized in that, Including the DC input source V connected in sequence in (I) Primary two-phase symmetrical half-bridge inverter circuit (II) Series resonant branch (III) Transformer (IV) Secondary rectifier circuit (V) and filter output circuit (VI); The primary-side two-phase symmetrical half-bridge inverter circuit (II) includes the primary-side first switch (S1), the primary-side second switch (S2), the primary-side third switch (S3), the primary-side fourth switch (S4), the primary-side first voltage divider capacitor (C1), and the primary-side second voltage divider capacitor (C2); The series resonant branch (Ⅲ) includes the resonant capacitor (C). r ), resonant inductor (L) r ), first magnetizing inductor (L m1 ), second magnetizing inductor (L m2 ); The transformer (Ⅳ) includes the first transformer (T1) and the second transformer (T2); The drain of the first primary-side switching transistor (S1) is connected to the DC input source V. in (Ⅰ) The positive terminal, the source of the first primary-side switch (S1) is connected to the drain of the second primary-side switch (S2) and the first magnetizing inductor (L) m1 One end of the primary side of the first transformer (T1) is connected to the same terminal on the primary side of the first transformer (T1), with the connection point being A; the drain of the third primary-side switch (S3) and one end of the first primary-side voltage divider capacitor (C1) are simultaneously connected to the drain of the first primary-side switch (S1) and the DC input source V. in (Ⅰ) The positive terminal; the source of the fourth primary-side switch (S4) and one end of the second primary-side voltage divider capacitor (C2) are simultaneously connected to the source of the second primary-side switch (S2) and the DC input source V. in (Ⅰ) The negative terminal; the source of the third primary-side switch (S3) is connected to the drain of the fourth primary-side switch (S4) and the second primary-side magnetizing inductor (L m2 One end of the primary side of the transformer (T1) is connected to the non-identical terminal of the primary side of the second primary side transformer (T2), with the connection point being B; the other end of the primary side first voltage divider capacitor (C1) is connected to the other end of the primary side second voltage divider capacitor (C2) and the resonant capacitor (C1). r One end of the connection is C; Resonant capacitor (C) r The other end is connected to the resonant inductor (L). r One end of the resonant inductor (L) r The other end is connected to the first magnetizing inductor (L) m1 At the other end of the second magnetizing inductor (L) m2 The other end of the transformer (T1), the non-same-name terminal on the primary side of the first transformer (T1), and the same-name terminal on the primary side of the second transformer (T2) are connected at point N. The secondary side terminal of the first transformer (T1) is connected to the secondary side terminal of the second transformer (T2); the secondary side terminals of the first transformer (T1) and the second transformer (T2) are both connected to the secondary rectifier circuit (V).

2. The resonant converter according to claim 1, characterized in that, The secondary-side rectifier circuit (V) includes a secondary-side first rectifier diode (D1), a secondary-side second rectifier diode (D2), a secondary-side fifth switch (S5), and a secondary-side sixth switch (S6); The non-same-name terminal on the secondary side of the first transformer (T1) is connected to the anode of the first rectifier diode (D1) and the cathode of the second rectifier diode (D2) on the secondary side, and the connection point is X; the non-same-name terminal on the secondary side of the second transformer (T2) is connected to the source of the fifth switch (S5) and the drain of the sixth switch (S6) on the secondary side, and the connection point is Y. The cathode of the first rectifier diode (D1) on the secondary side is connected to the drain of the fifth switch (S5) on the secondary side and then connected to the filter output circuit (VI); the anode of the second rectifier diode (D2) on the secondary side is connected to the source of the sixth switch (S6) on the secondary side and then connected to the filter output circuit (VI).

3. The resonant converter according to claim 1, characterized in that, The secondary-side rectifier circuit (V) includes a secondary-side first rectifier diode (D1), a secondary-side second rectifier diode (D2), a secondary-side fifth switch (S5), and a secondary-side sixth switch (S6); The non-same-name terminal on the secondary side of the first transformer (T1) is connected to the anode of the first rectifier diode (D1) on the secondary side and the drain of the fifth switch (S5) on the secondary side, and the connection point is X; the non-same-name terminal on the secondary side of the second transformer (T2) is connected to the anode of the second rectifier diode (D2) on the secondary side and the drain of the sixth switch (S6) on the secondary side, and the connection point is Y. The cathode of the first rectifier diode (D1) on the secondary side is connected to the cathode of the second rectifier diode (D2) on the secondary side, and then connected to the filter output circuit (VI); the source of the fifth switch (S5) on the secondary side is connected to the source of the sixth switch (S6) on the secondary side, and then connected to the filter output circuit (VI).

4. The resonant converter according to claim 1, characterized in that, The secondary-side rectifier circuit (V) includes a secondary-side first rectifier diode (D1), a secondary-side second rectifier diode (D2), a secondary-side fifth switch (S5), and a secondary-side sixth switch (S6); The non-same-name terminal on the secondary side of the first transformer (T1) is connected to the cathode of the first rectifier diode (D1) on the secondary side and the source of the fifth switch (S5) on the secondary side, and the connection point is X; the non-same-name terminal on the secondary side of the second transformer (T2) is connected to the cathode of the second rectifier diode (D2) on the secondary side and the source of the sixth switch (S6) on the secondary side, and the connection point is Y. The anode of the first rectifier diode (D1) on the secondary side is connected to the anode of the second rectifier diode (D2) on the secondary side, and then connected to the filter output circuit (VI); the drain of the fifth switch (S5) on the secondary side is connected to the drain of the sixth switch (S6) on the secondary side, and then connected to the filter output circuit (VI).

5. The resonant converter according to claim 1, characterized in that, The secondary-side rectifier circuit (V) includes a secondary-side first rectifier diode (D1), a secondary-side second rectifier diode (D2), a secondary-side third rectifier diode (D3), a secondary-side fourth rectifier diode (D4), a secondary-side fifth switch (S5), and a secondary-side sixth switch (S6); The non-same-name terminal on the secondary side of the first transformer (T1) is connected to the anode of the first rectifier diode (D1) on the secondary side, the drain of the fifth switch (S5) on the secondary side, and the cathode of the second rectifier diode (D2) on the secondary side, with the connection point being X; The non-same-name terminal on the secondary side of the second transformer (T2) is connected to the anode of the third rectifier diode (D3), the drain of the sixth switch (S6), and the cathode of the fourth rectifier diode (D4) on the secondary side, with the connection point being Y; the source of the fifth switch (S5) on the secondary side is connected to the source of the sixth switch (S6); the cathode of the first rectifier diode (D1) on the secondary side is connected to the cathode of the third rectifier diode (D3) on the secondary side, and then connected to the filter output circuit (VI); the anode of the third rectifier diode (D3) on the secondary side is connected to the anode of the fourth rectifier diode (D4) on the secondary side, and then connected to the filter output circuit (VI).

6. The resonant converter according to any one of claims 1-5, characterized in that, The filter output circuit (VI) includes output filter capacitors (C) connected in parallel. o ) and load (R o ).

7. A control method applied to the resonant converter according to any one of claims 1-6, characterized in that, Based on gain adjustment capability, it can be divided into gain buck adjustment stage and gain boost adjustment stage: During the gain-down adjustment stage, the duty cycles of the drive pulses for the primary-side first switch (S1), second switch (S2), third switch (S3), and fourth switch (S4) are all 0.5 (ignoring dead time). Furthermore, the drive pulses for the primary-side first switch (S1) and second switch (S2) are complementary, as are the drive pulses for the primary-side third switch (S3) and fourth switch (S4). The switching frequency is equal to the series resonant frequency. Moreover, the primary-side fourth switch… The driving pulse of the primary-side switch (S4) controls the phase shift of the driving pulse of the primary-side first switch (S1), and the driving pulse of the primary-side third switch (S3) controls the phase shift of the driving pulse of the primary-side second switch (S2). The primary-side third switch (S3) and the primary-side fourth switch (S4) have the same phase shift angle relative to the primary-side second switch (S2) and the primary-side first switch (S1), respectively. The secondary-side fifth switch (S5) and the secondary-side sixth switch (S6) perform rectification. During the gain boost regulation stage, the phase shift angles of the primary-side third switch (S3) and the primary-side fourth switch (S4) relative to the primary-side second switch (S2) and the primary-side first switch (S1) are 180°, respectively. This means the drive pulses of the primary-side first switch (S1) and the third switch (S3) are the same, and their duty cycles are both 50% (ignoring dead time). The drive pulses of the primary-side second switch (S2) and the primary-side fourth switch (S4) are also the same, and their duty cycles are both 50% (ignoring dead time). The drive pulse of the secondary-side fifth switch (S5) is the same as that of the secondary-side sixth switch (S6). The drive pulses are complementary; the duty cycle of the drive pulse of the fifth switch (S5) on the secondary side is 50% (ignoring dead time), and it is phase-shifted relative to the first switch (S1) and the third switch (S3) on the primary side; the duty cycle of the drive pulse of the sixth switch (S6) on the secondary side is 50% (ignoring dead time), and it is phase-shifted relative to the second switch (S2) and the fourth switch (S4) on the primary side; the fifth switch (S5) and the sixth switch (S6) on the secondary side have the same phase-shift angle relative to the first switch (S1) and the second switch (S2) on the primary side, respectively.

8. The control method according to claim 7, characterized in that, During the gain-down adjustment phase The fifth and sixth secondary-side switches (S5 and S6) use their own body diodes for rectification, or they can be used as synchronous rectifiers.

9. The control method according to claim 7, characterized in that, During the gain reduction adjustment stage, the gain adjustment range of the resonant converter is [0, 1].

10. The control method according to claim 7, characterized in that, During the gain boost adjustment stage, the gain of the resonant converter is greater than 1; within the preset gain adjustment range, the voltage gain increases with the increase of the phase shift angle.

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