Five-switch multi-mode wide-voltage-range LLC resonant converter

Abstract

The invention discloses a five-switch multi-mode wide-voltage-range LLC resonant converter. The five-switch multi-mode wide-voltage-range LLC resonant converter is mainly composed of a five-switch inverter stage, a resonant cavity, a high-frequency transformer and a full-wave rectifier stage. A hybrid modulation mode is adopted in a control strategy, the duty ratio is adjusted through fixed-frequency pulse width modulation (PWM) so as to increase the voltage of a direct-current bus, and the voltage gain range of more than three times is achieved in cooperation with fixed-duty-ratio pulse frequency modulation (PFM). In addition, the topology can maintain excellent soft switching characteristics in a full working range, and high-efficiency operation under wide voltage output is ensured. Compared with a traditional wide-range resonant converter, only five weighted switch tubes, one transformer and two diodes are needed, the hardware cost is remarkably reduced, the power density is improved, and the wide-range resonant converter has remarkable engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of wide-gain resonant converters, and in particular, a five-switch multi-mode wide voltage range LLC resonant converter. Background Technology

[0002] The continuous increase in installed capacity of clean energy sources, represented by wind and solar power, has driven the transformation of the power system towards a coordinated approach involving power generation, grid, load, and storage. With the explosive growth of the new energy vehicle (NEV) industry and the widespread adoption of distributed energy storage technology, DC-DC converters face unprecedented voltage adaptation challenges. Existing charging infrastructure must accommodate the charging needs of both existing low-voltage vehicles and new high-voltage vehicles, requiring DC-DC converters to have an extremely wide output voltage range. Furthermore, the terminal voltage of battery energy storage systems fluctuates significantly throughout their charge-discharge cycle depending on the state of charge (SOC). Therefore, developing high-efficiency DC-DC converters with wide output voltage regulation capabilities has become a key technological requirement for building a modern energy internet and high-power charging network.

[0003] Isolated DC-DC converters utilize high-frequency transformers to achieve electrical isolation and voltage matching, which is a core component ensuring system safety and performance. Among them, LLC resonant converters, with their zero-voltage turn-on (ZVS) primary-side switches and zero-current turn-off (ZCS) secondary-side rectifiers, excel in achieving high efficiency and low electromagnetic interference (EMI), and are widely used in server power supplies and on-board chargers. However, in applications with a wide output voltage range, traditional LLC converters exhibit significant limitations: to meet the wide range of voltage gain requirements, the converter must operate over an extremely wide frequency range. When the operating frequency is far from the resonant frequency, on the one hand, it becomes difficult to optimize the flux swing and loss characteristics of the magnetic components (transformer and resonant inductor), and the size is difficult to reduce; on the other hand, to obtain sufficient voltage gain, the design often requires reducing the transformer's magnetizing inductance L. m This directly leads to a significant increase in the peak value of the primary-side excitation current and the reactive circulating current. Excessive circulating current not only increases the conduction losses of power devices but may also cause the primary-side switching transistors to lose their ZVS characteristics under high-voltage heavy loads, severely limiting the converter's efficiency and power density across the entire voltage range. Therefore, exploring a novel LLC resonant converter topology that can balance wide output range adjustment and high efficiency across the entire range has become a pressing technical challenge in the field of power electronics. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a five-switch, multi-mode, wide-voltage-range LLC resonant converter that widens the converter's voltage gain while ensuring high-efficiency operation. This invention widens the voltage gain through two control methods: increasing the input bus voltage via fixed-frequency pulse width modulation and increasing the voltage gain via fixed-duty-cycle pulse frequency modulation.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A five-switch multi-mode wide voltage range LLC resonant converter includes: an inverter unit, a resonant cavity, a transformer (T), and a full-wave rectifier circuit;

[0007] The inverter unit includes a first bridge arm, a second bridge arm, a fifth switching transistor, an input inductor, an input capacitor, and an intermediate capacitor. The first bridge arm is composed of a first switching transistor and a second switching transistor connected in series, and the second bridge arm is composed of a third switching transistor and a fourth switching transistor connected in series. The input capacitor is connected in parallel across the input power supply. One end of the first bridge arm is connected to the positive terminal of the input power supply, and the other end is connected to the negative terminal of the input power supply. One end of the input inductor is connected to the positive terminal of the input power supply, and the other end is connected to one end of the second bridge arm, and the other end of the second bridge arm is connected to the negative terminal of the input power supply.

[0008] The source of the fifth switching transistor is connected to the drain of the third switching transistor, the drain of the fifth switching transistor is connected to one end of the intermediate capacitor, and the other end of the intermediate capacitor is connected to the negative terminal of the input power supply.

[0009] A node B is provided between the first and second switching transistors, and a node A is provided between the third and fourth switching transistors;

[0010] The resonant cavity includes a resonant inductor and a resonant capacitor connected in series, as well as the magnetizing inductance of the transformer; one end of the resonant capacitor is connected to the resonant inductor, and the other end is connected to node A; the primary winding of the transformer is connected in parallel with the magnetizing inductor, one end of which is connected to the other end of the resonant inductor, and the other end is connected to node B.

[0011] Furthermore, the full-wave rectifier circuit includes a first rectifier diode, a second rectifier diode, an output capacitor, and an output resistor; the anodes of the first rectifier diode and the second rectifier diode are respectively connected to the two ends of the secondary winding of the transformer; the cathodes of the first rectifier diode and the second rectifier diode are connected and then connected to one end of the output capacitor and the output resistor; the other end of the output capacitor and the output resistor is connected to the center tap of the secondary side of the transformer.

[0012] Furthermore, the converter is configured to switch between four operating modes according to the output voltage requirements, the four operating modes being: half-bridge constant duty cycle pulse frequency modulation mode, half-bridge constant frequency pulse width modulation mode, full-bridge constant frequency pulse width modulation mode, and full-bridge constant duty cycle pulse frequency modulation mode.

[0013] Furthermore, when operating in the half-bridge constant duty cycle pulse frequency modulation mode: the fourth switch remains constantly on, the first and second switches are complementaryly on with a duty cycle of 0.5, and the third and fifth switches remain off; at this time, the resonant converter is equivalent to a half-bridge LLC resonant converter, and the voltage gain is adjusted by changing the switching frequency.

[0014] Furthermore, when operating in the half-bridge fixed-frequency pulse width modulation mode: the second switch remains constantly on, and the first switch remains constantly off; the fourth switch operates at the resonant frequency f. r The third switch is turned on with a duty cycle of 0.5. The third switch and the fourth switch are 180 degrees out of phase. The switching period of the third switch and the fifth switch is 3 / 2 times the switching period of the fourth switch. With the duty cycle of the fourth switch as a reference, the duty cycle of the third switch is 0.5 + D1 (0 ≤ D1 ≤ 0.5) to charge the input inductor. The fifth switch and the third switch are complementary in conduction, and the duty cycle is 1 - D1. The voltage gain is adjusted by adjusting the duty cycle D1.

[0015] Furthermore, when operating in the full-bridge fixed-frequency pulse width modulation mode: the first and second switches are complementary in conduction with a duty cycle of 0.5; the switching state of the fourth switch is consistent with that of the first switch; the conduction time of the third switch is 180 degrees out of phase with that of the fourth switch, and the switching period of the third switch and the fifth switch is 3 / 2 times the switching period of the fourth switch. Taking the duty cycle of the fourth switch as a reference, the duty cycle of the third switch is 0.5 + D2 (0 ≤ D2 ≤ 0.5) to charge the input inductor; the fifth switch is complementary in conduction with that of the third switch, and its duty cycle is 1 - D2; the voltage gain is adjusted by adjusting the duty cycle D2.

[0016] Furthermore, when operating in the full-bridge constant duty cycle pulse frequency modulation mode: the third switch remains constantly on; the first and second switches are complementaryly on with a duty cycle of 0.5; the switching state of the fourth switch is consistent with that of the first switch; the fifth switch is complementaryly on with the fourth switch with a duty cycle of 0.5; at this time, the resonant converter is equivalent to a half-bridge LLC resonant converter with a gain of 3, and the voltage gain is adjusted by changing the switching frequency.

[0017] Preferably, the present invention also provides a voltage modulation method for an LLC resonant converter, based on the aforementioned five-switch multi-mode wide voltage range LLC resonant converter, comprising:

[0018] Half-bridge constant duty cycle pulse frequency modulation mode. In this mode, the fourth switch is kept on, the first and second switches are turned on complementaryly with a duty cycle of 0.5, and the third and fifth switches are kept off. The voltage gain is adjusted by adjusting the switching frequency.

[0019] In the half-bridge fixed-frequency pulse width modulation mode, the second switch remains constantly on, and the first switch remains constantly off; the fourth switch operates at the resonant frequency f. r The third and fourth switches are turned on with a duty cycle of 0.5. The third and fourth switches are 180 degrees out of phase. The switching period of the third and fifth switches is 3 / 2 times that of the fourth switch. Taking the duty cycle of the fourth switch as a reference, the duty cycle of the third switch is 0.5 + D1 (0 ≤ D1 ≤ 0.5) to charge the input inductor. The fifth switch is complementary to the third switch and has a duty cycle of 1 - D1. The voltage gain is adjusted by adjusting the duty cycle D1.

[0020] In the full-bridge fixed-frequency pulse width modulation mode, the first and second switches are complementary in conduction with a duty cycle of 0.5; the switching state of the fourth switch is consistent with that of the first switch; the conduction times of the third and fourth switches are 180 degrees out of phase; the switching period of the third and fifth switches is 3 / 2 times the switching period of the fourth switch; with the duty cycle of the fourth switch as a reference, the duty cycle of the third switch is 0.5 + D2 (0 ≤ D2 ≤ 0.5) to charge the input inductor; the fifth switch is complementary in conduction with the third switch, and its duty cycle is 1 - D2; the voltage gain is adjusted by adjusting the duty cycle D2.

[0021] In the full-bridge constant duty cycle pulse frequency modulation mode, the third switch remains constantly on; the first and second switches conduct complementaryly with a duty cycle of 0.5; the switching state of the fourth switch is the same as that of the first switch; and the fifth switch conducts complementaryly with the fourth switch with a duty cycle of 0.5. The voltage gain is adjusted by regulating the switching frequency.

[0022] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0023] 1. This invention employs a topology based on the fusion of Boost and LLC converters, combining a hybrid control strategy of constant-frequency pulse width modulation (PWM) and constant-duty-cycle pulse frequency modulation (PFM), and designs four operating modes. It achieves a voltage gain range of more than 3 times, breaking through the bottleneck of traditional LLC converters in wide-range applications. Simultaneously, this structure allows for a larger transformer magnetizing inductance value, effectively suppressing reactive circulating current in the resonant tank circuit, reducing the turn-off loss of the switching transistors, and ensuring high-efficiency operation over a wide output voltage range.

[0024] 2. The entire topology consists of only five active switching transistors (Q1-Q5), one magnetic component (transformer), and two diodes. Compared with traditional wide-range cascaded solutions, it significantly reduces the number of components, simplifies the circuit structure, lowers hardware costs, and greatly improves the power density of the converter.

[0025] 3. Through specific timing control and resonant cavity design, zero-voltage turn-on (ZVS) of the switching transistor can be achieved in all four modes; even under high voltage heavy load or voltage regulation, it can maintain excellent soft-switching characteristics, significantly reduce switching conduction losses, improve system efficiency and reduce electromagnetic interference.

[0026] 4. In the half-bridge constant duty cycle pulse frequency modulation mode and the full-bridge constant duty cycle pulse frequency modulation mode, only the frequency needs to be adjusted. In the half-bridge constant frequency pulse width modulation mode and the full-bridge constant frequency pulse width modulation mode, only the duty cycle needs to be adjusted. In each mode, only a single control variable needs to be adjusted, which makes the control simple and easy to implement in engineering.

[0027] 5. To adapt to an ultra-wide output voltage range, this invention designs four different operating modes and employs a hybrid control strategy to achieve smooth transitions between modes. During mode switching, the converter effectively avoids transient voltage and current surges and oscillations, ensuring the continuity of the output voltage and the stability of system operation, significantly improving the converter's dynamic response performance. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the converter structure of the present invention.

[0029] Figure 2 This is a schematic diagram of the half-bridge constant duty cycle pulse frequency modulation mode converter of the present invention.

[0030] Figure 3 This is a schematic diagram of the half-bridge fixed-frequency pulse width modulation mode converter of the present invention.

[0031] Figure 4 This is a schematic diagram of the full-bridge fixed-frequency pulse width modulation mode converter of the present invention.

[0032] Figure 5This is a schematic diagram of the full-bridge constant duty cycle pulse frequency modulation mode converter of the present invention.

[0033] Figure 6 This is the voltage gain curve of the present invention.

[0034] Figure 7 This is the steady-state simulation waveform of the circuit when the output voltage is 70V.

[0035] Figure 8 This is the steady-state simulation waveform of the circuit when the output voltage is 126V.

[0036] Figure 9 This is the steady-state simulation waveform of the circuit when the output voltage is 221V.

[0037] Figure 10 This is the steady-state simulation waveform of the circuit when the output voltage is 400V. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0039] Example 1

[0040] like Figure 1 As shown, this embodiment provides a five-switch multi-mode wide voltage range LLC resonant converter, which mainly includes an inverter unit, a resonant cavity, a transformer, and a full-wave rectifier circuit.

[0041] The inverter unit mainly consists of two bridge arms Q1, Q2, Q3, and Q4, an additional switching transistor Q5, and an input inductor L. a Input capacitor C in and intermediate capacitor C a The first bridge arm consists of a first switch Q1 and a second switch Q2 connected in series, and the second bridge arm consists of a third switch Q3 and a fourth switch Q4 connected in series. One end of the first bridge arm is connected to the input capacitor C. in Connected in parallel to the input power supply V in The positive terminal is connected to the input power supply V. in The negative terminal, one end of the second bridge arm is connected to the input inductor L. a One end is connected to the input power supply V. in The negative terminal, input inductor L a Connected between the two bridge arms and at the same end of both arms, the source of switch Q5 is connected to the drain of switch Q3, and the drain is connected to the intermediate capacitor C. a Connected, with intermediate capacitor C a The other end is connected to the input power supply V inThe negative terminals are connected; a node B is provided between the two main switching transistors Q1 and Q2 in one bridge arm, and a node A is provided between the two main switching transistors Q3 and Q4 in the other bridge arm.

[0042] The resonant cavity includes a resonant inductor L connected in series. r and resonant capacitor C r And the magnetizing inductance L of transformer T m Resonant capacitor C r One end is connected to the resonant inductor L r The transformer is connected in series, with the other end connected to node A, and the primary side of the transformer and the magnetizing inductance L m After being connected in parallel, one end is connected in series with the other end of the resonant inductor, and the other end is connected to node B;

[0043] The full-wave rectifier circuit includes two rectifier diodes D. rec1 and D rec2 and output capacitor C o and output resistance R o D rec1 and D rec2 The anodes are connected to the outermost two ends of the secondary side of the transformer, D rec1 and D rec2 Cathode and output capacitor C o and output resistance R o One end is connected together, and the output capacitor C o and output resistance R o The other end is connected to the end led out from the center tap of the transformer.

[0044] Intermediate capacitor C a Voltage V at both ends Ca The expression is:

[0045] ;

[0046] Input inductance L a The current ripple above for:

[0047] ;

[0048] In the formula, Indicates the switching cycle.

[0049] like Figure 2As shown, the converter operates in half-bridge constant duty cycle pulse frequency modulation mode. In this mode, switch Q4 is always on, while switches Q1 and Q2 are complementary, conducting with a duty cycle of 0.5. Switches Q3 and Q5 are off, and the boost circuit is not operating. In this mode, the LLC resonant converter is equivalent to a half-bridge LLC resonant converter. According to the definition of voltage gain in a half-bridge LLC resonant converter... Using the Fundamental Harmonic Approximation (FHA) method, the voltage gain expression M1 for this operating mode is derived as follows:

[0050] ;

[0051] In the formula, , , , , k represents the magnetizing inductance L m With resonant inductor L r The ratio of f; n Expressed as switching frequency f s With resonant frequency f r The ratio of Z; o Q represents the equivalent line resistance at the input terminal; n This represents the quality factor of the converter.

[0052] The conditions for switches Q1 and Q2 to achieve ZVS are as follows:

[0053] ;

[0054] In the formula, C oss The output capacitance of the switching transistor is represented by t. d This is represented as dead time.

[0055] In this operating mode, the voltage gain is changed by adjusting the switching frequency.

[0056] like Figure 3 As shown, the operating mode is a half-bridge fixed-frequency pulse width modulation mode, with switch Q2 always on, switch Q1 always off, and switch Q4 operating at the resonant frequency f. r Furthermore, the switching transistors Q3 and Q4 are turned on with a duty cycle of 0.5. The turn-on times of Q3 and Q4 are 180 degrees out of phase. The switching periods of Q3 and Q5 are 3 / 2 times that of Q4. Using the duty cycle of Q4 as a reference, the duty cycle of Q3 is 0.5 + D1. The input inductor L... aDuring charging and energy storage, switching transistors Q5 and Q3 are complementary in conduction. The duty cycle of switching transistor Q5 is 1-D1, which enables the input power supply V to conduct. in Along with the input inductor, the intermediate capacitor C a Charging is initiated. In this operating mode, the voltage gain expression M2 of the converter is:

[0057] ;

[0058] Among them, switch Q5 is for synchronous rectification, and the conditions for switches Q3 and Q4 to achieve ZVS are as follows:

[0059] ;

[0060] The voltage U between node A and node B is achieved by adjusting the duty cycle D1. ab The absolute value of the voltage gain is increasing relative to that of the half-bridge LLC resonant converter, thereby increasing the voltage gain.

[0061] like Figure 4 As shown, the operating mode is full-bridge fixed-frequency pulse width modulation mode. Switches Q1 and Q2 are complementary in conduction with a duty cycle of 0.5. The turn-on and turn-off of switch Q4 are consistent with those of switch Q1. The turn-on times of switch Q3 and switch Q4 are 180 degrees out of phase. The switching period of switch Q3 and switch Q5 is 3 / 2 times the switching period of switch Q4. Taking the duty cycle of switch Q4 as a reference, the duty cycle of switch Q3 is 0.5 + D2. The input inductor L... a For charging and energy storage, switching transistors Q5 and Q3 are complementary in conduction, with a duty cycle of 1-D2, so that the input power supply V... in and input inductance L a At the same time, in the intermediate capacitor C a Charging is performed by adjusting the duty cycle D2 to achieve the voltage U between node A and node B. ab The voltage value of the full-bridge LLC resonant converter is constantly increasing during the positive half-cycle, thereby increasing the voltage gain.

[0062] In this operating mode, the expression for the converter's voltage gain M3 is:

[0063] ;

[0064] Among them, switch Q5 is for synchronous rectification, and the conditions for switches Q1, Q2, Q3, and Q4 to achieve ZVS are as follows:

[0065] ;

[0066] like Figure 5 As shown, the operating mode is a full-bridge constant duty cycle pulse frequency modulation mode, with switch Q3 constantly conducting, and switches Q1 and Q2 conducting complementaryly with a duty cycle of 0.5. In the half-bridge constant frequency pulse width modulation mode, the on and off states of switch Q4 are consistent with those of switch Q1, and switch Q5 conducts complementaryly with switch Q4 with a duty cycle of 0.5. In this mode, the LLC resonant converter is equivalent to a half-bridge LLC resonant converter with a gain of 3.

[0067] The voltage gain M4 of the converter is expressed as follows:

[0068] ;

[0069] The conditions for achieving ZVS for switching transistors Q1, Q4, Q2, and Q5 are as follows:

[0070] ;

[0071] In this operating mode, the voltage gain is changed by adjusting the switching frequency.

[0072] like Figure 6 The diagram illustrates the voltage gain characteristic curves of this invention under four different operating modes. For applications with a wide output voltage range, the converter can flexibly match and switch to the corresponding voltage gain mode based on real-time output voltage commands (or load requirements). This multi-mode collaborative working mechanism not only significantly expands the system's voltage regulation range but also effectively ensures the continuity and stability of voltage gain throughout the entire operating range.

[0073] Preferably, in another embodiment, a simulation circuit is provided to implement the above-described resonant converter design, and the specific simulation parameters are shown in Table 1:

[0074] Table 1. Main circuit parameter design of the present invention

[0075]

[0076] Among them, V gs1 It is the gate-source voltage of the switching transistor Q1, V ds1 It is the drain-source voltage of the switching transistor Q1; V gs2 It is the gate-source voltage of the switching transistor Q2, V ds2 It is the drain-source voltage of the switching transistor Q2; V gs3 It is the gate-source voltage of the switching transistor Q3, V ds3 It is the drain-source voltage of the switching transistor Q3; V gs4 It is the gate-source voltage of the switching transistor Q4, V ds4 It is the drain-source voltage of the switching transistor Q4; V gs5 It is the gate-source voltage of switching transistor Q5, Vds5 This is the drain-source voltage of switching transistor Q5. Lr It is the resonant current, i Lm It is the magnetizing current; U ab It is the voltage between node A and node B; V o This indicates the output voltage value.

[0077] When the output voltage V o Below 95V, the LLC resonant converter operates in half-bridge constant duty cycle pulse frequency modulation mode. At an output voltage of 70V, the switching frequency is 150kHz, and the simulated waveform is as follows. Figure 7 As shown.

[0078] When the output voltage V o When the voltage is greater than 95V and less than 190V, the LLC resonant converter operates in half-bridge fixed-frequency pulse-width modulation mode. With an output voltage of 126V, D1 is 0.25, the switching frequency is 100kHz, and the simulated waveform is as follows. Figure 8 As shown.

[0079] When the output voltage V o When the voltage is greater than 190V and less than 285V, the LLC resonant converter operates in full-bridge fixed-frequency pulse-width modulation mode. With an output voltage of 222V, D2 is 0.25, the switching frequency is 100kHz, and the simulated waveform is as follows. Figure 9 As shown.

[0080] When the output voltage V o When the voltage is greater than 285V, the LLC resonant converter operates in full-bridge constant duty cycle pulse frequency modulation mode. When the output voltage is 400V, D2 is 0.5, the switching frequency is 68kHz, and the simulation waveform is as follows. Figure 10 As shown.

[0081] Example 2

[0082] Based on the same inventive concept, this application also provides a voltage modulation method for an LLC resonant converter. Based on the aforementioned five-switch multi-mode wide voltage range LLC resonant converter, it includes four arbitrarily switchable control modes, namely:

[0083] In the half-bridge constant duty cycle pulse frequency modulation mode, switch Q4 is always on, while switches Q1 and Q2 are complementary and conduct with a duty cycle of 0.5. Switches Q3 and Q5 are not working. In this mode, the resonant converter is equivalent to a half-bridge LLC resonant converter. The voltage gain of the converter can be widened by adjusting the switching frequency.

[0084] In the half-bridge fixed-frequency pulse width modulation mode, switch Q2 is always on, switch Q1 is always off, and switch Q4 operates at the resonant frequency f. rFurthermore, with a duty cycle of 0.5, the on-time of switching transistors Q3 and Q4 is increased by an additional duty cycle D1 on top of their complementary conduction, providing additional on-time for the input inductor L. a For charging and energy storage, switching transistors Q5 and Q4 are turned on complementaryly, with a duty cycle of 0.5-D1 being advanced to enable the input power supply V. in Along with the input inductor, the intermediate capacitor C a Charging is performed by adjusting the duty cycle D1 to achieve the voltage U between node A and node B. ab Compared to a half-bridge LLC resonant converter, the voltage gain is continuously increasing, thereby expanding the voltage gain;

[0085] In the full-bridge fixed-frequency pulse width modulation mode, switches Q1 and Q2 conduct complementaryly with a duty cycle of 0.5. The turn-on and turn-off of switch Q4 are consistent with those of switch Q1. In addition to the complementary conduction of switches Q3 and Q4, an extra duty cycle D2 is added to the on-time of the input inductor L. a For charging and energy storage, switching transistors Q5 and Q4 are turned on complementaryly, with a duty cycle of 0.5-D2 being advanced to enable the input power supply V. in Along with the input inductor, the intermediate capacitor C a Charging is performed by adjusting the duty cycle D2 to achieve the voltage U between node A and node B. ab The voltage value of the full-bridge LLC resonant converter is constantly increasing during the positive half-cycle, thereby increasing the voltage gain;

[0086] In the full-bridge constant duty cycle pulse frequency modulation mode, switch Q3 is always on, while switches Q1 and Q2 are complementary in conduction with a duty cycle of 0.5. In the half-bridge constant frequency pulse width modulation mode, the on and off states of switch Q4 are the same as those of switch Q1, and switch Q5 is complementary in conduction with switch Q4 with a duty cycle of 0.5. In this mode, the LLC resonant converter is equivalent to a half-bridge LLC resonant converter with a gain of 3x, and the voltage gain is widened by adjusting the switching frequency.

[0087] This invention is not limited to the embodiments described above. The above description of specific embodiments is intended to illustrate and explain the technical solutions of this invention. The specific embodiments described above are merely illustrative and not restrictive. Without departing from the spirit and scope of the claims, those skilled in the art can make many specific modifications based on the teachings of this invention, and these modifications all fall within the scope of protection of this invention.

Claims

1. A five-switch multi-mode wide voltage range LLC resonant converter, characterized in that, include: Inverter unit, resonant cavity, transformer (T), and full-wave rectifier circuit; The inverter unit includes a first bridge arm, a second bridge arm, a fifth switch (Q5), and an input inductor (L). a ), input capacitor (C) in ) and intermediate capacitor (C a The first bridge arm consists of a first switch (Q1) and a second switch (Q2) connected in series, and the second bridge arm consists of a third switch (Q3) and a fourth switch (Q4) connected in series; the input capacitor (C) in The first bridge arm is connected in parallel across the two ends of the input power supply; one end of the first bridge arm is connected to the positive terminal of the input power supply, and the other end is connected to the negative terminal of the input power supply; the input inductor (L) a One end of the bridge arm is connected to the positive terminal of the input power supply, and the other end is connected to one end of the second bridge arm. The other end of the second bridge arm is connected to the negative terminal of the input power supply. The source of the fifth switch (Q5) is connected to the drain of the third switch (Q3), and the drain of the fifth switch (Q5) is connected to the intermediate capacitor (C). a One end of the capacitor is connected to the intermediate capacitor (C). a The other end of the circuit is connected to the negative terminal of the input power supply. A node B is provided between the first switch (Q1) and the second switch (Q2), and a node A is provided between the third switch (Q3) and the fourth switch (Q4); The resonant cavity includes a resonant inductor (L) connected in series. r ) and resonant capacitor (C r ), and the magnetizing inductance (L) of the transformer (T) m The resonant capacitor (C) r One end of the resonant inductor (L) is connected to the other end of the resonant inductor (L). r The transformer (T) is connected to the magnetizing inductor (L) at one end and to the other end at node A; the primary winding of the transformer (T) is connected to the magnetizing inductor (L) at the other end. m After being connected in parallel, one end is connected to the resonant inductor (L). r The other end is connected to the other end of the ), and the other end is connected to the node B.

2. The five-switch multi-mode wide voltage range LLC resonant converter according to claim 1, characterized in that, The full-wave rectifier circuit includes a first rectifier diode (D). rec1 ), second rectifier diode (D) rec2 ), output capacitor (C) o and output resistance (R) o ); the first rectifier diode (D) rec1 ) and second rectifier diode (D rec2 The anodes of the first rectifier diode (D) are respectively connected to the two ends of the secondary winding of the transformer (T); rec1 ) and second rectifier diode (D rec2 After the cathode of the capacitor is connected, it is connected to the output capacitor (C). o and output resistance (R) o One end of the capacitor is connected to the output capacitor (C). o and output resistance (R) o The other end of the circuit is connected to the center tap on the secondary side of the transformer (T).

3. The five-switch multi-mode wide voltage range LLC resonant converter according to claim 1, characterized in that, The converter is configured to switch between four operating modes according to the output voltage requirements. The four operating modes include: half-bridge constant duty cycle pulse frequency modulation mode, half-bridge constant frequency pulse width modulation mode, full-bridge constant frequency pulse width modulation mode, and full-bridge constant duty cycle pulse frequency modulation mode.

4. A five-switch multi-mode wide voltage range LLC resonant converter according to claim 3, characterized in that, When operating in the half-bridge constant duty cycle pulse frequency modulation mode: the fourth switch (Q4) remains constantly on, the first switch (Q1) and the second switch (Q2) are complementary on with a duty cycle of 0.5, and the third switch (Q3) and the fifth switch (Q5) remain off; at this time, the resonant converter is equivalent to a half-bridge LLC resonant converter, and the voltage gain is adjusted by changing the switching frequency.

5. A five-switch multi-mode wide voltage range LLC resonant converter according to claim 3, characterized in that, When operating in the half-bridge fixed-frequency pulse width modulation mode: the second switch (Q2) remains constantly on, and the first switch (Q1) remains constantly off; the fourth switch (Q4) operates at the resonant frequency f. r And it conducts with a duty cycle of 0.5; the conduction time of the third switch (Q3) and the fourth switch (Q4) are 180 degrees out of phase; the switching period of the third switch (Q3) and the fifth switch (Q5) is 3 / 2 times the switching period of the fourth switch (Q4); with the duty cycle of the fourth switch (Q4) as a reference, the duty cycle of the third switch (Q3) is 0.5 + D1 against the input inductor (L a Charging; the fifth switch (Q5) and the third switch (Q3) are complementary in conduction, and the conduction duty cycle is 1-D1; the voltage gain is adjusted by adjusting the duty cycle D1, 0≤D1≤0.

5.

6. A five-switch multi-mode wide voltage range LLC resonant converter according to claim 3, characterized in that, When operating in the full-bridge fixed-frequency pulse width modulation mode: the first switch (Q1) and the second switch (Q2) are complementary in conduction with a duty cycle of 0.5; the switching state of the fourth switch (Q4) is consistent with that of the first switch (Q1); the conduction time of the third switch (Q3) differs from that of the fourth switch (Q4) by 180 degrees; the switching period of the third switch (Q3) and the fifth switch (Q5) is 3 / 2 times the switching period of the fourth switch (Q4); with the duty cycle of the fourth switch (Q4) as a reference, the duty cycle of the third switch (Q3) is 0.5 + D2 against the input inductor (L). a Charging; the fifth switch (Q5) and the third switch (Q3) are complementary in conduction, and the conduction duty cycle is 1-D2; the voltage gain is adjusted by adjusting the duty cycle D2, 0≤D2≤0.

5.

7. A five-switch multi-mode wide voltage range LLC resonant converter according to claim 3, characterized in that, When operating in the full-bridge constant duty cycle pulse frequency modulation mode: the third switch (Q3) remains constantly on; the first switch (Q1) and the second switch (Q2) are complementary on with a duty cycle of 0.5; the switching state of the fourth switch (Q4) is the same as that of the first switch (Q1); the fifth switch (Q5) is complementary on with the fourth switch (Q4) with a duty cycle of 0.5; at this time, the resonant converter is equivalent to a half-bridge LLC resonant converter with a gain of 3 times, and the voltage gain is adjusted by changing the switching frequency.

8. A voltage modulation method for an LLC resonant converter, based on the five-switch multi-mode wide voltage range LLC resonant converter according to any one of claims 1 or 2, characterized in that, include: Half-bridge constant duty cycle pulse frequency modulation mode. In this mode, the fourth switch (Q4) is kept on, the first switch (Q1) and the second switch (Q2) are turned on complementaryly with a duty cycle of 0.5, and the third switch (Q3) and the fifth switch (Q5) are kept off. The voltage gain is adjusted by adjusting the switching frequency. In the half-bridge fixed-frequency pulse width modulation mode, the second switch (Q2) remains constantly on, and the first switch (Q1) remains constantly off; the fourth switch (Q4) operates at the resonant frequency f. r And it conducts with a duty cycle of 0.5; the conduction time of the third switch (Q3) and the fourth switch (Q4) are 180 degrees out of phase; the switching period of the third switch (Q3) and the fifth switch (Q5) is 3 / 2 times the switching period of the fourth switch (Q4); with the duty cycle of the fourth switch (Q4) as a reference, the duty cycle of the third switch (Q3) is 0.5 + D1 against the input inductor (L a Charging; the fifth switch (Q5) and the third switch (Q3) are complementary in conduction, and the duty cycle is 1-D1; the voltage gain is adjusted by adjusting the duty cycle D1, 0≤D1≤0.5; full-bridge fixed-frequency pulse width modulation mode, in which the first switch (Q1) and the second switch (Q2) are complementary in conduction with a duty cycle of 0.5; the switching state of the fourth switch (Q4) is consistent with that of the first switch (Q1); the conduction time of the third switch (Q3) and the fourth switch (Q4) is 180 degrees out of phase, the switching period of the third switch (Q3) and the fifth switch (Q5) is 3 / 2 times the switching period of the fourth switch (Q4), and with the duty cycle of the fourth switch (Q4) as a reference, the duty cycle of the third switch (Q3) is 0.5+D2 for the input inductor (L a Charging; the fifth switch (Q5) and the third switch (Q3) are complementary in conduction, and the conduction duty cycle is 1-D2; the voltage gain is adjusted by adjusting the duty cycle D2, 0≤D2≤0.5; In the full-bridge constant duty cycle pulse frequency modulation mode, the third switch (Q3) remains constantly on; the first switch (Q1) and the second switch (Q2) are complementary on with a duty cycle of 0.5; the switching state of the fourth switch (Q4) is the same as that of the first switch (Q1). The fifth switch (Q5) and the fourth switch (Q4) are turned on complementaryly with a duty cycle of 0.5, and the voltage gain is adjusted by adjusting the switching frequency.

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