A bridge arm multiplexing soft-switching DC-AC converter and modulation method thereof

Abstract

This invention discloses a bridge-arm multiplexed soft-switching DC-AC converter and its modulation method. The bridge-arm multiplexed soft-switching DC-AC converter multiplexes the secondary rectifier diodes of the front-stage full-bridge LLC resonant converter and the input bridge-arm switches of the subsequent DC-AC converter, thereby forming a quasi-single-stage DC-AC converter and reducing the number of switches. In this bridge-arm multiplexed soft-switching DC-AC converter, the full-bridge LLC converter operates in a fixed-frequency open-loop mode, and the subsequent DC-AC converter uses PWM + phase-shift modulation, thereby achieving soft switching of all switches. This topology is applicable to new energy power generation scenarios such as photovoltaic and wind power, enabling soft switching, electrical isolation, and wide-range voltage regulation of switching devices, while effectively reducing the number of devices, thus achieving high power density, high conversion efficiency, and high reliability.

Description

Technical Field

[0001] This invention relates to the field of power electronic converter technology, specifically to a bridge arm multiplexed soft-switching DC-AC converter and its modulation method. Background Technology

[0002] Driven by the "dual carbon" goals, the large-scale development of new energy power generation such as photovoltaic and wind power has led to the DC-AC converter becoming the core equipment for DC power inverter grid connection. Its performance directly determines the power generation efficiency and grid connection quality. However, new energy power generation such as photovoltaic and wind power faces problems such as input voltage fluctuations and installation space limitations, which place demands on the converter to have a wide range of voltage input, high efficiency under all operating conditions, and high power density.

[0003] Traditional two-stage inverters suffer from problems such as superimposed losses between the two stages and low power density, while single-stage inverters have poor wide-range voltage adaptability and concentrated component stress. These inverters generally suffer from difficulties in balancing wide-range voltage adaptability and soft switching, as well as the trade-off between efficiency and integration, making it difficult to fully meet the practical application requirements of wide voltage fluctuations, high efficiency under all operating conditions, and high power density in photovoltaic and wind power. To address this, a bridge-arm multiplexed soft-switching DC-AC inverter is proposed. This inverter modulates the inductor current waveform of the soft-switching DC-AC inverter into a quadrilateral shape, combining a quasi-single-stage architecture with bridge-arm multiplexing and the soft-switching characteristics of LLC under all operating conditions. This achieves wide-range voltage adaptability, high-efficiency energy conversion, and high-integration design, providing a practical solution for optimizing DC-AC converters for new energy power generation.

[0004] The invention disclosed in CN120074256A is a bridge-arm multiplexed soft-switching AC-DC converter and its control circuit and method. This bridge-arm multiplexed soft-switching AC-DC converter multiplexes the primary-side switches of a full-bridge LLC resonant converter and the rear-arm switches of a bridgeless AC-DC converter, enabling power factor correction, soft switching of all switches, and a reduction in the number of components. This invention achieves full-range soft switching, electrical isolation, and wide-range voltage regulation, while effectively reducing the number of components, resulting in high power density, high conversion efficiency, and high reliability. However, the bridge arm reuse design of this invention is only applicable to AC-DC rectification and conversion scenarios. It can only complete the unidirectional energy conversion from AC to DC and has no DC to AC inverter output capability. It cannot directly adapt to the inverter grid connection requirements of new energy power generation such as photovoltaic and wind power. At the same time, its modulation strategy is designed around the power factor correction and DC voltage regulation of AC-DC rectification. It cannot adapt to the AC output regulation requirements of DC-AC inverter and cannot achieve quadrilateral waveform modulation of the inverter side inductor current. It is difficult to solve the industry pain point of wide voltage adaptation and soft switching under all operating conditions in the DC-AC conversion of new energy power generation.

[0005] In summary, there is currently a lack of an isolated soft-switching DC-AC converter that is adapted to the needs of new energy power generation and is based on bridge arm multiplexing. This converter can achieve direct DC-AC inversion while meeting multiple technical requirements such as wide-range voltage input, soft switching under all operating conditions, high integration and high power density. Summary of the Invention

[0006] To address the shortcomings of the existing technology, this invention provides a bridge arm multiplexing type soft-switching DC-AC converter and its modulation method, which can achieve wide-range voltage input, high efficiency under all operating conditions, and high power density.

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

[0008] In a first aspect, the present invention discloses a bridge arm multiplexing type soft-switching DC-AC converter, wherein the bridge arm multiplexing type soft-switching DC-AC converter includes a full-bridge LLC resonant converter and a soft-switching DC-AC inverter.

[0009] The full-bridge LLC resonant converter includes an input DC voltage source V. in Resonant inductor L r Magnetizing inductance L m Resonant capacitor C r Transformer T r DC bus capacitor C bus First pre-stage switch Q1, second pre-stage switch Q2, third pre-stage switch Q3, fourth pre-stage switch Q4, first multiplexer switch Q A1 Second multiplex switch Q A2 The third multiplex switch Q B1 The fourth multiplex switch Q B2 Each switching transistor is equipped with a corresponding anti-parallel diode and junction capacitance;

[0010] In this configuration, the first and second pre-stage switches Q1 and Q2 are complementaryly turned on to form the first bridge arm, and the third and fourth pre-stage switches Q3 and Q4 are complementaryly turned on to form the second bridge arm. The first and second bridge arms are the primary-side bridge arms of the full-bridge LLC resonant converter; the first multiplexed switch Q... A1 Second multiplex switch Q A2 Complementary conduction forms the third bridge arm, and the third multiplexed switch Q B1 and the fourth multiplex switch Q B2 Complementary conduction forms the fourth bridge arm; the third and fourth bridge arms are the secondary bridge arms of the full-bridge LLC resonant converter; magnetizing inductor L m Transformer T connected in parallel r The two ends of the primary side, and the transformer T r One end of the primary side is connected in series with a resonant inductor L. rResonant capacitor C r Connect the midpoint of the first bridge arm, transformer T r The other end of the primary side is connected to the midpoint of the second bridge arm, and transformer T... r The two ends of the secondary side are connected to the midpoints of the third and fourth bridge arms, respectively;

[0011] The soft-switching DC-AC inverter includes a first inductor L. a Second inductor L b First output filter capacitor C out1 Second output filter capacitor C out2 Output load R Ld First stage switching transistor Q A3 The second-stage switching transistor Q A4 The third-stage switching transistor Q B3 The fourth stage switching transistor Q B4 The first stage switching transistor Q A3 The second-stage switching transistor Q A4 Complementary conduction forms the fifth bridge arm, and the third subsequent stage switch Q... B3 The fourth stage switching transistor Q B4 Complementary conduction forms the sixth bridge arm; the fifth and sixth bridge arms are the output bridge arms of the soft-switching DC-AC inverter; the first inductor L a The second inductor L is connected in series between the midpoint of the third bridge arm and the midpoint of the fifth bridge arm. b The first output filter capacitor C is connected in series between the midpoint of the fourth bridge arm and the midpoint of the sixth bridge arm. out1 With the first stage switching transistor Q A3 Drain in parallel, second output filter capacitor C out2 With the third stage switch Q B3 Drains in parallel, output load R Ld Connected in series with the first subsequent switching transistor Q A3 Drain and third-stage switching transistor Q B3 Between the drains, each switching transistor is equipped with a corresponding anti-parallel diode and junction capacitance; the soft-switching DC-AC inverter reuses the full third and fourth bridge arms as its own input bridge arms, forming a bridge arm multiplexing quasi-single-stage DC-AC conversion topology.

[0012] Furthermore, the input DC voltage source V in The positive terminal of the transistor is connected to the drain of the first pre-stage switch Q1 and the third pre-stage switch Q3. The source of the first pre-stage switch Q1, the drain of the second pre-stage switch Q2, and the resonant capacitor C are connected. r One end is connected to the resonant capacitor C. r The other end and the resonant inductor L r One end is connected to the resonant inductor L. r The other end is connected to the magnetizing inductor Lm One end and transformer T r One end of the primary winding is connected, and the magnetizing inductance L m The other end is connected to transformer T r The other end of the primary side is connected to the source of the third pre-stage switch Q3 and the drain of the fourth pre-stage switch Q4. The third pre-stage switch Q4 is connected to the source of the second pre-stage switch Q2 and the input DC voltage source V. in The negative terminal is connected, transformer T r One end of the secondary side is connected to the first multiplex switch Q. A1 The source and second multiplexed switch Q A2 The drain and the first inductor L a One end is connected, the first inductor L a The other end is connected to the first subsequent stage switch Q. A3 The source and the second-stage switch Q A4 The drains are connected, and the transformer T r The other end of the secondary side is connected to the third multiplex switch Q. B1 The source and the fourth multiplexed switch Q B2 The drain and the second inductor L b One end is connected, the second inductor L b The other end is connected to the third subsequent stage switch Q. B3 The source and the fourth post-stage switch Q B4 The drains are connected, and the first multiplexed switch Q is connected. A1 With the third multiplexed switch Q B1 The drain and DC bus capacitor C bus One end is connected to the DC bus capacitor C. bus The other end is connected to the second multiplex switch Q. A2 and the fourth multiplex switch Q B2 The source is connected to the first stage switch Q. A3 The drain of the first output filter capacitor C out1 One end and output load R Ld One end is connected, and the output load R Ld The other end is connected to the third subsequent stage switch Q. B3 The drain of the second output filter capacitor C out2 One end is connected to the second stage switch Q. A4 With the fourth stage switch Q B4 The drain and output capacitor C out1 With C out2 The other end is connected.

[0013] Furthermore, the modulation strategy of the bridge arm multiplexed soft-switching DC-AC converter is PWM + phase shift modulation. By coordinating the adjustment of the phase shift angle and the duty cycle, zero-voltage turn-on of all switching transistors in the converter is achieved.

[0014] Specifically, the duty cycle of all switches in the first, second, third, and fourth bridge arms is a fixed value; the first pre-stage switch Q1, the fourth pre-stage switch Q4, and the first multiplexed switch Q... A1 The fourth multiplex switch Q B2 Simultaneously switching on and off, the second pre-stage switch Q2, the third pre-stage switch Q3, and the second multiplex switch Q... A2 The third multiplex switch Q B1 Simultaneous on / off;

[0015] The first post-stage switch Q A3 The second-stage switching transistor Q A4 The third-stage switching transistor Q B3 The fourth stage switching transistor Q B4 The timing of the multiplexed third and fourth bridge arms is satisfied: the first multiplexed switch Q A1 Prior to the first stage switching transistor Q A3 Turn off, first stage switch Q A3 Prior to the second multiplex switch Q A2 Turn off, second multiplexer switch Q A2 Prior to the second-stage switching transistor Q A4 Turn off, second stage switch Q A4 Prior to the first multiplex switch Q A1 Turn off by adjusting the first stage switching transistor Q. A3 Duty cycle D y1 and the first multiplexed switch Q A1 With the first stage switching transistor Q A3 Phase shift angle D at the activation time θ1 This causes the first stage switching transistor Q to... A3 The second-stage switching transistor Q A4 The junction capacitance ensures complete charging and discharging, guaranteeing the natural conduction of its anti-parallel diode and achieving optimal switching timing for zero-voltage turn-on; the third multiplexed switch Q... B1 Prior to the third-stage switching transistor Q B3 Turn off, third stage switch Q B3 Prior to the fourth multiplex switch Q B2 Turn off, fourth multiplexer switch Q B2 Prior to the fourth stage switching transistor Q B4 Turn off, fourth stage switch Q B4 Prior to the third multiplex switch Q B1 Turn off by adjusting the third-stage switching transistor Q. B3 Duty cycle D y2 and the third multiplex switch Q B1 With the third stage switch Q B3Phase shift angle D at the activation time θ2 This causes the third-stage switching transistor Q to... B3 The fourth stage switching transistor Q B4 The junction capacitance ensures complete charging and discharging, guaranteeing the natural conduction of its anti-parallel diode and achieving optimal switching timing for zero-voltage turn-on; finally, by adjusting the first subsequent stage switch Q... A3 The second-stage switching transistor Q A4 The third-stage switching transistor Q B3 The fourth stage switching transistor Q B4 Voltage regulation is achieved by adjusting the duty cycle.

[0016] Furthermore, the duty cycle of all switches in the first bridge arm, second bridge arm, third bridge arm, and fourth bridge arm is 50%.

[0017] Furthermore, the bridge arm multiplexing type soft-switching DC-AC converter includes 12 switching modes, namely:

[0018] Switching mode 1 [t0,t1]: At time t0, the first pre-stage switch Q1 and the fourth pre-stage switch Q4 are simultaneously turned on, and the input DC voltage source V... in The resonant inductor L is continuously powered by the first pre-stage switch Q1 and the fourth pre-stage switch Q4. r and resonant capacitor C r Resonant operation, first multiplexed switch Q A1 Second stage switch Q A4 Turn on, applied to the first inductor L a The voltage across the terminals is V bus i La Linear increase; fourth multiplexed switch Q B2 and the fourth stage switching transistor Q B4 Simultaneously, it conducts, applied to the second inductor L. b The voltage across the terminals is 0, i Lb Remain unchanged;

[0019] Switching mode 2 [t1,t2]: At time t1, the resonant inductance L r and resonant capacitor C r Resonant operation, first multiplexed switch Q A1 Turn on, the second stage switch Q A4 Turn off, i La Give the second stage switching transistor Q A4 C A4 Charging, and simultaneously supplying power to the first subsequent stage switch Q. A3 C A3 Discharge; at time t2, C A4 The voltage is charged to V A Meanwhile, C A3The voltage is reduced to zero, and the first stage switching transistor Q... A3 anti-parallel diode D A3 Natural conduction, zero-voltage turn-on of the first stage switch Q A3 The fourth multiplex switch Q B2 and the fourth stage switching transistor Q B4 Simultaneously, it conducts, applied to the second inductor L. b The voltage across the terminals is 0, i Lb Remain unchanged;

[0020] Switching mode 3 [t2,t3]: At time t2, the resonant inductance L r and resonant capacitor C r Resonant operation, first multiplexed switch Q A1 and the first stage switching transistor Q A3 Turn on, applied to the first inductor L a The voltage across the terminals is V bus -V A i La Linear descent, fourth multiplexed switch Q B2 and the fourth stage switching transistor Q B4 Simultaneously, it conducts, applied to the second inductor L. b The voltage across the terminals is 0, i Lb Remain unchanged;

[0021] Switching mode 4 [t3,t4]: At time t3, the resonant inductance L r and resonant capacitor C r Resonant operation, first multiplexed switch Q A1 and the first stage switching transistor Q A3 Turn on, applied to the first inductor L a The voltage across the terminals is V bus -V A i La Linear descent, fourth multiplexed switch Q B2 Turn on, fourth stage switch Q B4 Turn off, second inductor L b Give the fourth stage switching transistor Q B4 C B4 Charging, and simultaneously supplying power to the third-stage switching transistor Q. B3 C B3 Discharge, at time t4, C B4 The voltage is charged to V B Meanwhile, C B3 The voltage is reduced to zero, and the third-stage switching transistor Q... B3 anti-parallel diode D B3 Natural conduction, zero-voltage turn-on of the third-stage switching transistor Q. B3 ;

[0022] Switching mode 5 [t4,t5]: At time t4, the resonant inductance L r and resonant capacitor C r Resonant operation, first multiplexed switch Q A1 and the first stage switching transistor Q A3 Turn on, applied to the first inductor L a The voltage across the terminals is V bus -V A i La Linear descent, fourth multiplexed switch Q B2 and the third-stage switching transistor Q B3 Turn on, applied to the second inductor L b The voltage across the terminals is -V bus i Lb Linear decrease;

[0023] Switching mode 6 [t5,t6]: At time t5, the first pre-stage switch Q1 and the fourth pre-stage switch Q4 are simultaneously turned off, and the resonant inductor L... r The capacitors C1 and C4 of the first and fourth pre-stage switches Q1 and Q4 are charged, while the capacitors C2 and C3 of the second and third pre-stage switches Q2 and Q3 are discharged. At time t6, the voltage of C1 and C4 is charged to the input DC voltage source V. in Simultaneously, the voltages of C2 and C3 are reduced to zero, and the anti-parallel diodes D2 and D3 of the second and third pre-stage switching transistors Q2 and Q3 naturally conduct, turning on the second and third pre-stage switching transistors Q2 and Q3 with zero voltage. The first multiplexed switching transistor Q... A1 and the fourth multiplex switch Q B2 Simultaneously turn off, resonant inductor L r The transformer supplies power to the first multiplexer transistor Q. A1 and the fourth multiplex switch Q B2 C A1 and C B2 Charging, and simultaneously supplying power to the second multiplexed switch Q. A2 and the third multiplex switch Q B1 C A2 and C B1 Discharge; at time t6, C A1 and C B2 The voltage is charged into the input DC voltage source V. in Meanwhile, C A2 and C B1 The voltage is set to zero, and the second multiplexed switch Q... A2 and the third multiplex switch Q B1 anti-parallel diode D A2 and D B1 Natural conduction, zero-voltage turn-on of the second multiplexed switch Q A2 and the third multiplex switch QB1 Resonant inductor L r Resonant capacitor C r And excitation inductance L m Resonant operation;

[0024] Switching mode 7 [t6,t7]: At time t6, the second pre-stage switch Q2 and the third pre-stage switch Q3 are turned on simultaneously, and the input DC voltage source V... in The resonant inductor L is continuously powered by the second pre-stage switch Q2 and the third pre-stage switch Q3. r and resonant capacitor C r Resonant operation, second multiplexed switch Q A2 and the first stage switching transistor Q A3 Turn on, applied to the first inductor L a The voltage across the terminals is -V A i La Linear descent, third multiplexed switch Q B1 and the third-stage switching transistor Q B3 Simultaneously, it conducts, applied to the second inductor L. b The voltage across the terminals is V bus -V B i Lb Linear increase;

[0025] Switching mode 8 [t7,t8]: At time t7, the resonant inductance L r and resonant capacitor C r Resonant operation, second multiplexed switch Q A2 Turn on, the first stage switch Q A3 Turn off, i La Give the first stage switching transistor Q A3 C A3 Charging, and simultaneously supplying power to the second-stage switching transistor Q. A4 C A4 Discharge; at time t8, C A3 The voltage is charged to V A Meanwhile, C A4 The voltage is reduced to zero, and the second stage switch Q... A4 anti-parallel diode D A4 Natural conduction, zero-voltage turn-on of the second stage switch Q A4 The third multiplex switch Q B1 and the third-stage switching transistor Q B3 Simultaneously, it conducts, applied to the second inductor L. b The voltage across the terminals is V bus -V B i Lb Linear increase;

[0026] Switching mode 9 [t8,t9]: At time t8, the resonant inductance Lr and resonant capacitor C r Resonant operation, second multiplexed switch Q A2 Second stage switch Q A4 Turn on, applied to the first inductor L a The voltage across the terminals is 0, i La The third multiplexer switch Q remains unchanged. B1 and the third-stage switching transistor Q B3 Simultaneously, it conducts, applied to the second inductor L. b The voltage across the terminals is V bus -V B i Lb Linear increase;

[0027] Switching mode 10[t9,t 10 At time t9, the resonant inductance L r and resonant capacitor C r Resonant operation, second multiplexed switch Q A2 Second stage switch Q A4 Turn on, applied to the first inductor L a The voltage across the terminals is 0, i La The third multiplexer switch Q remains unchanged. B1 Turn on, the third stage switch Q B3 Turn off, second inductor L b Give the third stage switching transistor Q B3 C B3 Charging, and simultaneously supplying power to the fourth subsequent switching transistor Q. B4 C B4 Discharge, at time t4, C B3 The voltage is charged to V B Meanwhile, C B4 The voltage is reduced to zero, and the fourth stage switch Q is... B4 anti-parallel diode D B4 Natural conduction, zero-voltage turn-on of the fourth stage switch Q B4 ;

[0028] Switching mode 11[t 10 ,t 11 ]: In t 10 At time, the resonant inductance L r and resonant capacitor C r Resonant operation, second multiplexed switch Q A2 Second stage switch Q A4 Turn on, applied to the first inductor L a The voltage across the terminals is 0, i La The third multiplexer switch Q remains unchanged. B1 and the fourth stage switching transistor Q B4 Simultaneously, it conducts, applied to the second inductor L.b The voltage across the terminals is V bus i Lb Linear increase;

[0029] Switching mode 12[t] 11 ,t 12 ]: In t 11 At that moment, the second pre-stage switch Q2 and the third pre-stage switch Q3 are simultaneously turned off, and the resonant inductor L... r The capacitors C2 and C3 of the second and third pre-stage switches Q2 and Q3 are charged, while the capacitors C2 and C4 of the first and fourth pre-stage switches Q1 and Q4 are discharged. At time t6, the voltage across C2 and C3 is charged to the input DC voltage source V. in Simultaneously, the voltages of C1 and C4 are reduced to zero, and the anti-parallel diodes D1 and D4 of the first and fourth pre-stage switching transistors Q1 and Q4 naturally conduct, turning on the first and fourth pre-stage switching transistors Q1 and Q4 at zero voltage. The second multiplexed switching transistor Q... A2 and the third multiplex switch Q B1 Simultaneously turn off, resonant inductor L r The transformer supplies power to the second multiplexer transistor Q. A2 and the third multiplex switch Q B1 C A2 and C B1 Charging, and simultaneously supplying power to the first multiplexed switch Q. A1 and the fourth multiplex switch Q B2 C A1 and C B2 Discharge; at time t6, C A2 and C B1 The voltage is charged into the input DC voltage source V. in Meanwhile, C A1 and C B2 The voltage is reduced to zero, and the first multiplexed switch Q... A1 and the fourth multiplex switch Q B2 anti-parallel diode D A1 and D B2 Natural conduction, zero-voltage turn-on of the first multiplexer switch Q A1 and the fourth multiplex switch Q B2 Resonant inductor L r Resonant capacitor C r And excitation inductance L m Resonant operation.

[0030] Secondly, this invention discloses a modulation method for a bridge-arm multiplexed soft-switching DC-AC converter. The modulation method employs a PWM + phase-shift fusion modulation strategy, achieving zero-voltage soft-switching of all switches in the converter by coordinating the adjustment of the duty cycle and turn-on / turn-off phase shift angles of the switching transistors, while simultaneously achieving wide-range voltage regulation of the output voltage. The modulation method specifically includes the following steps:

[0031] S1. Fix the duty cycle of all switches in the first bridge arm, the second bridge arm, and the multiplexed third and fourth bridge arms of the full-bridge LLC resonant converter to 50% to maintain the fixed frequency operation mode.

[0032] S2, controls the first pre-stage switch Q1, the fourth pre-stage switch Q4, and the first multiplex switch Q. A1 The fourth multiplex switch Q B2 Synchronous switching controls the second pre-stage switch Q2, the third pre-stage switch Q3, and the second multiplex switch Q. A2 The third multiplex switch Q B1 Synchronous switching on and off, with the two sets of switching transistors in a complementary conduction state;

[0033] S3, controls the first-stage switching transistor Q. A3 The second-stage switching transistor Q A4 The first multiplexer switch Q satisfies the strict turn-on and turn-off timing requirements of the third bridge arm. A1 Prior to the first stage switching transistor Q A3 Turn off, first stage switch Q A3 Prior to the second multiplex switch Q A2 Turn off, second multiplexer switch Q A2 Prior to the second-stage switching transistor Q A4 Turn off, second stage switch Q A4 Prior to the first multiplex switch Q A1 Turn off; by adjusting the first stage switching transistor Q A3 Duty cycle D y1 and the first multiplexed switch Q A1 With the first stage switching transistor Q A3 Phase shift angle D at the activation time θ1 This causes the first stage switching transistor Q to... A3 The second-stage switching transistor Q A4 The junction capacitance is fully charged and discharged, ensuring that its anti-parallel diode conducts naturally, achieving zero-voltage turn-on;

[0034] S4, controls the third-stage switching transistor Q. B3 The fourth stage switching transistor Q B4 The third multiplexer switch Q satisfies strict turn-on and turn-off timing requirements with the fourth bridge arm. B1 Prior to the third-stage switching transistor Q B3Turn off, third stage switch Q B3 Prior to the fourth multiplex switch Q B2 Turn off, fourth multiplexer switch Q B2 Prior to the fourth stage switching transistor Q B4 Turn off, fourth stage switch Q B4 Prior to the third multiplex switch Q B1 Turn off; by adjusting the third-stage switching transistor Q. B3 Duty cycle D y2 and the third multiplex switch Q B1 With the third stage switch Q B3 Phase shift angle D at the activation time θ2 This causes the third-stage switching transistor Q to... B3 The fourth stage switching transistor Q B4 The junction capacitance is fully charged and discharged, ensuring that its anti-parallel diode conducts naturally, achieving zero-voltage turn-on;

[0035] S5. By coordinating the phase shift angle and duty cycle adjustments in steps S3 and S4, all switches in the converter's front-end, multiplexing, and rear-end stages achieve zero-voltage soft-switching; finally, by adjusting the first rear-end switch Q... A3 The second-stage switching transistor Q A4 The third-stage switching transistor Q B3 The fourth stage switching transistor Q B4 The duty cycle is adjusted to achieve wide-range continuous voltage regulation of the output voltage.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] First, this invention provides a bridge-arm multiplexed soft-switching DC-AC converter and its modulation method, which innovates the circuit topology by multiplexing the secondary-side switches of the full-bridge LLC resonant converter and the input bridge-arm switches of the soft-switching DC-AC converter. Compared with traditional DC-AC converters, the bridge-arm multiplexed soft-switching DC-AC converter of this invention can realize soft switching of all switches and effectively reduce the number of devices through bridge-arm multiplexing.

[0038] Secondly, the present invention provides a bridge arm multiplexing type soft-switching DC-AC converter and its modulation method, which electrically isolates the input voltage from the output voltage, better protects the downstream electrical equipment, can achieve wide-range voltage regulation, and has high power density, high conversion efficiency and high reliability. Attached Figure Description

[0039] Figure 1 This is a circuit diagram of the bridge arm multiplexing type soft-switching DC-AC converter of the present invention.

[0040] Figure 2This is a waveform diagram of the working state of a bridge arm multiplexed soft-switching DC-AC converter.

[0041] Figure 3a This is the equivalent circuit diagram of the switching mode 1 of the bridge arm multiplexed soft-switching DC-AC converter.

[0042] Figure 3b This is the equivalent circuit diagram of the switching mode 2 of the bridge arm multiplexed soft-switching DC-AC converter.

[0043] Figure 3c This is the equivalent circuit diagram of the switching mode 3 of the bridge arm multiplexed soft-switching DC-AC converter.

[0044] Figure 3d This is the equivalent circuit diagram of the switching mode 4 of the bridge arm multiplexed soft-switching DC-AC converter.

[0045] Figure 3e This is the equivalent circuit diagram of the switching mode 5 of the bridge arm multiplexed soft-switching DC-AC converter.

[0046] Figure 3f This is the equivalent circuit diagram of the switching mode 6 of the bridge arm multiplexed soft-switching DC-AC converter.

[0047] Figure 3g This is the equivalent circuit diagram of the switching mode 7 of the bridge arm multiplexed soft-switching DC-AC converter.

[0048] Figure 3h This is the equivalent circuit diagram of the switching mode 8 of the bridge arm multiplexed soft-switching DC-AC converter.

[0049] Figure 3i This is the equivalent circuit diagram of the switching mode 9 of the bridge arm multiplexed soft-switching DC-AC converter.

[0050] Figure 3j This is the equivalent circuit diagram of the switching mode 10 of the bridge arm multiplexed soft-switching DC-AC converter.

[0051] Figure 3k This is the equivalent circuit diagram of the switching mode 11 of the bridge arm multiplexed soft-switching DC-AC converter.

[0052] Figure 3l This is the equivalent circuit diagram of the switching mode 12 of the bridge arm multiplexed soft-switching DC-AC converter.

[0053] Figure 4 The simulation waveform diagram shows the overall waveform of the bridge arm multiplexed soft-switching DC-AC converter.

[0054] Figure 5 Simulation waveforms for the module expansion of the bridge arm multiplexed soft-switching DC-AC converter. Detailed Implementation

[0055] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0056] The circuit structure of the bridge arm multiplexing type soft-switching DC-AC converter of the present invention is as follows: Figure 1 As shown, the bridge arm multiplexed soft-switching DC-AC converter topology includes a full-bridge LLC resonant converter and a soft-switching DC-AC converter.

[0057] The full-bridge LLC converter includes an input DC voltage source V. in Resonant inductor L r Magnetizing inductance L m Resonant capacitor C r Transformer T r DC bus capacitor C bus Primary-side switch Q1 and its anti-parallel diode D1 and junction capacitance C1, primary-side switch Q2 and its anti-parallel diode D2 and junction capacitance C2, primary-side switch Q3 and its anti-parallel diode D3 and junction capacitance C4, primary-side switch Q4 and its anti-parallel diode D4 and junction capacitance C4, secondary-side switch Q... A1 and its anti-parallel diode D A1 junction capacitance C A1 Secondary switch Q A2 and its anti-parallel diode D A2 junction capacitance C A2 Secondary switch Q B1 and its anti-parallel diode D B1 junction capacitance C B1 Secondary switch Q B2 and its anti-parallel diode D B2 junction capacitance C B2 Q1 and Q2, Q3 and Q4 are complementary conductors, forming the primary side arms, referred to as arm 1 and arm 2; Q A1 and Q A2 Q B1 and Q B2 They are respectively complementary in conduction, forming secondary arms, referred to as arms 3 and 4. L m Parallel to T r The two ends of the original edge, and T r One end of the primary side is connected in series with L r C r Connect the midpoint of bridge arm 1, T r The other end of the primary side is connected to the midpoint of the primary side bridge arm 2, T r One end of the secondary side is connected to the midpoint of bridge arm 3, T r The other end of the secondary side is connected to the midpoint of bridge arm 4.

[0058] Soft-switching DC-AC inverters include inductor L a Inductor Lb Output filter capacitor C out1 C out2 Load R Ld Switching transistor Q A3 and its anti-parallel diode D A3 junction capacitance C A4 Switching transistor Q A4 and its anti-parallel diode D A4 junction capacitance C A4 Switching transistor Q B3 and its anti-parallel diode D B3 junction capacitance C B3 Switching transistor Q B4 and its anti-parallel diode D B4 junction capacitance C B4 and reuse of Q A1 and Q A2 The bridge arm 3 formed by Q and the bridge arm 3 formed by Q B1 and Q B2 The bridge arm 4 is formed. Q A3 and Q A4 Q B3 and Q B4 They are respectively complementary and conduct, forming bridge arms 5 and 6, L a Connected in series between the midpoint of bridge arm 3 and the midpoint of bridge arm 5, L b Connected in series between the midpoint of bridge arm 4 and the midpoint of bridge arm 6, C out1 With Q A3 Drain parallel, C out2 With Q B3 Drains in parallel, R Ld Connected in series with Q A3 Drain and Q B3 Between the drain electrodes.

[0059] like Figure 1 The input voltage source V shown in The positive terminal of Q1 is connected to the drain of Q3, and the source of Q1 is connected to the drain of Q2 and the C terminal. r One end is connected, C r The other end and L r One end is connected, L r The other end and L m one end and T r Connect one end of the original edge, L m The other end and T r The other end of the primary winding is connected to the source of Q3 and the drain of Q4. Q4 is connected to the source of Q2 and the voltage source V. in The negative terminal is connected, transformer T r One end of the secondary side is connected to Q A1 source and Q A2 Drain and inductance L aOne end is connected, inductor L a The other end and Q A3 source and Q A4 The drains are connected, and the transformer T r The other end of the secondary side is connected to Q. B1 source and Q B2 Drain and inductance L b One end is connected, inductor L b The other end and Q B3 source and Q B4 The drains are connected, Q A1 With Q B1 The drain and DC bus capacitor C bus One end is connected, C bus The other end and Q A2 and Q B2 The source is connected, Q A3 The drain and output capacitor C out1 One end is connected to one end of the output load, and the other end of the output load is connected to Q. B3 The drain and output capacitor C out2 Connect one end to Q A4 With Q B4 The drain and output capacitor C out1 With C out2 The other end is connected.

[0060] The modulation strategy of the bridge arm multiplexing soft-switching DC-AC converter of this invention is PWM + phase-shift modulation. The duty cycles of the front-stage bridge arms 1 and 2, i.e., Q1, Q2, Q3, and Q4, are all fixed at 50%. Q1 and Q4 are simultaneously switched on and off, and Q2 and Q3 are simultaneously switched on and off, with Q1 and Q4 complementarily conducting with Q2 and Q3; the multiplexed bridge arms 3 and 4, i.e., Q... A1 Q A2 Q B1 Q B2 The duty cycle is fixed at 50%, Q A1 Q B2 When Q1 and Q4 are switched on and off simultaneously, Q A2 Q B1 Simultaneously switched on and off with Q2 and Q3; downstream bridge arms 5 and 6, i.e., Q A3 Q A4 Q B3 Q B4 The multiplexed bridge arm satisfies the timing requirement: Q A1 It should precede Q. A3 Off, Q A3 It should precede Q. A2 Off, Q A2 It should precede Q. A4 Off, Q A4 It should precede Q. A1 Shutdown, due to QA1 Q A2 The duty cycle is fixed at 50% and Q A3 Q A4 Complementary conduction, achieved by adjusting the switching transistor Q. A3 Duty cycle D y1 and switching transistor Q A1 With the switching transistor Q A3 Phase shift angle D at the activation time θ1 To achieve optimal switching timing; Q B1 It should precede Q. B3 Off, Q B3 It should precede Q. B2 Off, Q B2 It should precede Q. B4 Off, Q B4 It should precede Q. B1 Shutdown, due to Q B1 Q B2 The duty cycle is fixed at 50% and Q B3 Q B4 Complementary conduction, achieved by adjusting the switching transistor Q. B3 Duty cycle D y2 and switching transistor Q B1 With the switching transistor Q B3 Phase shift angle D at the activation time θ2 To achieve optimal switching timing, thereby enabling soft switching of all switching transistors, and finally by adjusting Q... A3 Q A4 Q B3 Q B4 Voltage regulation is achieved by adjusting the duty cycle.

[0061] The bridge arm multiplexing soft-switching DC-AC converter of the present invention includes 12 switching modes. Figure 2 Figure 3 shows the operating waveforms of the bridge-arm multiplexed soft-switching DC-AC converter. Figure 4 shows the equivalent circuit diagrams of the bridge-arm multiplexed soft-switching DC-AC converter under different switching modes, respectively:

[0062] like Figure 3a Switching mode 1 [t0, t1]: At time t0, Q1 and Q4 are simultaneously turned on, V in L is continuously powered by Q1 and Q4. r and C r Resonant operation, Q A1 and Q A4 Conduction, applied to L a The voltage across the terminals is V bus i La Linear increase; Q B2 and Q B4 Simultaneously activated, applied to L b The voltage across the terminals is 0, i LbRemain unchanged;

[0063] like Figure 3b Switching mode 2 [t1,t2]: At time t1, L r and C r Resonant operation, Q A1 On, Q A4 Turn off, i La Give Q A4 C A4 Charging, while simultaneously supplying Q A3 C A3 Discharge; at time t2, C A4 The voltage is charged to V A Meanwhile, C A3 If the voltage is set to zero, then Q A3 anti-parallel diode D A3 Natural conduction, at which point Q can be turned on with zero voltage. A3 Q B2 and Q B4 Simultaneously activated, applied to L b The voltage across the terminals is 0, i Lb Remain unchanged;

[0064] like Figure 3c Switching mode 3 [t2,t3]: At time t2, L r and C r Resonant operation, Q A1 and Q A3 Conduction, applied to L a The voltage across the terminals is V bus -V A (Assume V) bus <V A ), i La linear decrease, Q B2 and Q B4 Simultaneously activated, applied to L b The voltage across the terminals is 0, i Lb Remain unchanged;

[0065] like Figure 3d Switching mode 4 [t3,t4]: At time t3, L r and C r Resonant operation, Q A1 and Q A3 Conduction, applied to L a The voltage across the terminals is V bus -V A (Assume V) bus <V A ), i La linear decrease, Q B2 On, Q B4 Off, inductor Lb Give Q B4 C B4 Charging, while simultaneously supplying Q B3 C B3 Discharge, at time t4, C B4 The voltage is charged to V B Meanwhile, C B3 If the voltage is set to zero, then Q B3 anti-parallel diode D B3 Natural conduction, at which point Q can be turned on with zero voltage. B3 ;

[0066] like Figure 3e Switching mode 5 [t4,t5]: At time t4, L r and C r Resonant operation, Q A1 and Q A3 Conduction, applied to L a The voltage across the terminals is V bus -V A (Assume V) bus <V A ), i La linear decrease, Q B2 and Q B3 Conduction, applied to L b The voltage across the terminals is -V bus i Lb Linear decrease;

[0067] like Figure 3f Switching mode 6 [t5, t6]: At time t5, Q1 and Q4 are turned off simultaneously, and the inductor L... r C1 and C4 of Q1 and Q4 are charged, while C2 and C3 of Q2 and Q3 are discharged; at time t6, the voltage of C1 and C4 is charged to V. in Simultaneously, the voltage across C2 and C3 is reduced to zero, causing the anti-parallel diodes D2 and D3 of Q2 and Q3 to conduct naturally. This allows Q2 and Q3 to be switched on with zero voltage. A1 and Q B2 Simultaneously turn off, inductor L r After the transformer, Q is supplied. A1 and Q B2 C A1 and C B2 Charging, while simultaneously supplying Q A2 and Q B1 C A2 and C B1 Discharge; at time t6, C A1 and C B2 The voltage is charged to V in Meanwhile, C A2 and C B1If the voltage is set to zero, then Q A2 and Q B1 anti-parallel diode D A2 and D B1 Natural conduction, at which point Q can be turned on with zero voltage. A2 and Q B1 L r C r and L m Resonant operation;

[0068] like Figure 3g Switching mode 7 [t6, t7]: At time t6, Q2 and Q3 are turned on simultaneously, V in L is continuously powered by Q2 and Q3. r and C r Resonant operation, Q A2 and Q A3 Conduction, applied to L a The voltage across the terminals is −V A i La linear decrease, Q B1 and Q B3 Simultaneously activated, applied to L b The voltage across the terminals is V bus -V B (Assume V) bus >V B ), i Lb Linear increase;

[0069] like Figure 3h Switching mode 8 [t7,t8]: At time t7, L r and C r Resonant operation, Q A2 On, Q A3 Turn off, i La Give Q A3 C A3 Charging, while simultaneously supplying Q A4 C A4 Discharge; at time t8, C A3 The voltage is charged to V A Meanwhile, C A4 If the voltage is set to zero, then Q A4 anti-parallel diode D A4 Natural conduction, at which point Q can be turned on with zero voltage. A4 Q B1 and Q B3 Simultaneously activated, applied to L b The voltage across the terminals is V bus -V B (Assume V) bus >V B ), i Lb Linear increase;

[0070] like Figure 3i Switching mode 9 [t8,t9]: At time t8, L r and C r Resonant operation, Q A2 and Q A4 Conduction, applied to L a The voltage across the terminals is 0, i La Unchanged, Q B1 and Q B3 Simultaneously activated, applied to L b The voltage across the terminals is V bus -V B (Assume V) bus >V B ), i Lb Linear increase;

[0071] like Figure 3j Switching mode 10[t9,t 10 At time t9, L r and C r Resonant operation, Q A2 and Q A4 Conduction, applied to L a The voltage across the terminals is 0, i La Unchanged, Q B1 On, Q B3 Off, inductor L b Give Q B3 C B3 Charging, while simultaneously supplying Q B4 C B4 Discharge, at time t4, C B3 The voltage is charged to V B Meanwhile, C B4 If the voltage is set to zero, then Q B4 anti-parallel diode D B4 Natural conduction, at which point Q can be turned on with zero voltage. B4 ;

[0072] like Figure 3k Switching mode 11[t] 10 ,t 11 ]: In t 10 At that moment, L r and C r Resonant operation, Q A2 and Q A4 Conduction, applied to L a The voltage across the terminals is 0, i La Unchanged, Q B1 and Q B4 Simultaneously activated, applied to L b The voltage across the terminals is V busi Lb Linear increase;

[0073] like Figure 3l Switching mode 12[t] 11 ,t 12 ]: In t 11 At that moment, Q2 and Q3 are turned off simultaneously, and inductor L... r C2 and C3 of Q2 and Q3 are charged, while C2 and C4 of Q1 and Q4 are discharged; at time t6, the voltage of C2 and C3 is charged to V. in Simultaneously, the voltages of C1 and C4 are reduced to zero, so the anti-parallel diodes D1 and D4 of Q1 and Q4 naturally conduct, allowing Q1 and Q4 to be turned on with zero voltage. A2 and Q B1 Simultaneously turn off, inductor L r After the transformer, Q is supplied. A2 and Q B1 C A2 and C B1 Charging, while simultaneously supplying Q A1 and Q B2 C A1 and C B2 Discharge; at time t6, C A2 and C B1 The voltage is charged to V in Meanwhile, C A1 and C B2 If the voltage is set to zero, then Q A1 and Q B2 anti-parallel diode D A1 and D B2 Natural conduction, at which point Q can be turned on with zero voltage. A1 and Q B2 L r C r and L m Resonant operation.

[0074] This invention can achieve full-range soft switching, electrical isolation, and wide-range voltage regulation, and effectively reduces the number of devices by multiplexing bridge arms, thus achieving high power density, high conversion efficiency, and high reliability.

[0075] To further illustrate the superiority of the circuit topology of this invention, a simulation example of this invention is given below.

[0076] Based on the main parameters of the 100W bridge arm multiplexed soft-switching DC-AC converter given in Table 1, a simulation circuit was built using Saber simulation software.

[0077] Table 1. Main parameters of bridge arm multiplexed soft-switching DC-AC converter

[0078] parameter symbol numerical values parameter symbol numerical values Input voltage <![CDATA[V in ]]> 360VDC Magnetizing inductor <![CDATA[L m ]]> 680µH Output voltage <![CDATA[V o ]]> 110VAC / 50Hz Resonant inductor <![CDATA[L r ]]> 141µH Output power <![CDATA[P o ]]> 100W Resonant capacitor <![CDATA[C r ]]> 15.3nF Transformer turns ratio N 1: 1 Intermediate bus capacitor <![CDATA[C bus ]]> 500µF Switching frequency <![CDATA[f s ]]> 100kHz DC side capacitor <![CDATA[C in ]]> 10µF inductance <![CDATA[L a ,L b ]]> 70µH AC side capacitor <![CDATA[C out1 、C out2 ]]> 20µF

[0079] Figure 4 and Figure 5 Simulation waveforms of a 100W bridge-arm multiplexed soft-switching DC-AC converter are presented. Figure 4 and Figure 5 It can be seen that during the switching cycle, L a Inductor current i La Modulated into a quadrilateral shape, it enables ZVS (zero-voltage turn-on) of the switching transistor; L b Inductor current i Lb When modulated into a quadrilateral shape, it can achieve ZVS (zero voltage turn-on) of the switching transistor.

[0080] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0081] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A bridge-arm multiplexing type soft-switching DC-AC converter, characterized in that, The bridge arm multiplexed soft-switching DC-AC converter includes a full-bridge LLC resonant converter and a soft-switching DC-AC inverter. The full-bridge LLC resonant converter includes an input DC voltage source V. in Resonant inductor L r Magnetizing inductance L m Resonant capacitor C r Transformer T r DC bus capacitor C bus First pre-stage switch Q1, second pre-stage switch Q2, third pre-stage switch Q3, fourth pre-stage switch Q4, first multiplexer switch Q A1 Second multiplex switch Q A2 The third multiplex switch Q B1 The fourth multiplex switch Q B2 Each switching transistor is equipped with a corresponding anti-parallel diode and junction capacitance; In this configuration, the first and second pre-stage switches Q1 and Q2 are complementaryly turned on to form the first bridge arm, and the third and fourth pre-stage switches Q3 and Q4 are complementaryly turned on to form the second bridge arm. The first and second bridge arms are the primary-side bridge arms of the full-bridge LLC resonant converter; the first multiplexed switch Q... A1 Second multiplex switch Q A2 Complementary conduction forms the third bridge arm, and the third multiplexed switch Q B1 and the fourth multiplex switch Q B2 Complementary conduction forms the fourth bridge arm; the third and fourth bridge arms are the secondary bridge arms of the full-bridge LLC resonant converter; magnetizing inductor L m Transformer T connected in parallel r The two ends of the primary side, and the transformer T r One end of the primary side is connected in series with a resonant inductor L. r Resonant capacitor C r Connect the midpoint of the first bridge arm, transformer T r The other end of the primary side is connected to the midpoint of the second bridge arm, and transformer T... r The two ends of the secondary side are connected to the midpoints of the third and fourth bridge arms, respectively; The soft-switching DC-AC inverter includes a first inductor L. a Second inductor L b First output filter capacitor C out1 Second output filter capacitor C out2 Output load R Ld First stage switching transistor Q A3 The second-stage switching transistor Q A4 The third-stage switching transistor Q B3 The fourth stage switching transistor Q B4 The first stage switching transistor Q A3 The second-stage switching transistor Q A4 Complementary conduction forms the fifth bridge arm, and the third subsequent stage switch Q... B3 The fourth stage switching transistor Q B4 Complementary conduction forms the sixth bridge arm; the fifth and sixth bridge arms are the output bridge arms of the soft-switching DC-AC inverter; the first inductor L a The second inductor L is connected in series between the midpoint of the third bridge arm and the midpoint of the fifth bridge arm. b The first output filter capacitor C is connected in series between the midpoint of the fourth bridge arm and the midpoint of the sixth bridge arm. out1 With the first stage switching transistor Q A3 Drain in parallel, second output filter capacitor C out2 With the third stage switch Q B3 Drains in parallel, output load R Ld Connected in series with the first subsequent switching transistor Q A3 Drain and third-stage switching transistor Q B3 Between the drains, each switching transistor is equipped with a corresponding anti-parallel diode and junction capacitance; the soft-switching DC-AC inverter reuses the full third and fourth bridge arms as its own input bridge arms, forming a bridge arm multiplexing quasi-single-stage DC-AC conversion topology.

2. The bridge-arm multiplexing type soft-switching DC-AC converter according to claim 1, characterized in that, The input DC voltage source V in The positive terminal of the transistor is connected to the drain of the first pre-stage switch Q1 and the third pre-stage switch Q3. The source of the first pre-stage switch Q1, the drain of the second pre-stage switch Q2, and the resonant capacitor C are connected. r One end is connected to the resonant capacitor C. r The other end and the resonant inductor L r One end is connected to the resonant inductor L. r The other end is connected to the magnetizing inductor L m One end and transformer T r One end of the primary winding is connected, and the magnetizing inductance L m The other end is connected to transformer T r The other end of the primary side is connected to the source of the third pre-stage switch Q3 and the drain of the fourth pre-stage switch Q4. The third pre-stage switch Q4 is connected to the source of the second pre-stage switch Q2 and the input DC voltage source V. in The negative terminal is connected, transformer T r One end of the secondary side is connected to the first multiplex switch Q. A1 The source and second multiplexed switch Q A2 The drain and the first inductor L a One end is connected, the first inductor L a The other end is connected to the first subsequent stage switch Q. A3 The source and the second-stage switch Q A4 The drains are connected, and the transformer T r The other end of the secondary side is connected to the third multiplex switch Q. B1 The source and the fourth multiplexed switch Q B2 The drain and the second inductor L b One end is connected, the second inductor L b The other end is connected to the third subsequent stage switch Q. B3 The source and the fourth post-stage switch Q B4 The drains are connected, and the first multiplexed switch Q is connected. A1 With the third multiplexed switch Q B1 The drain and DC bus capacitor C bus One end is connected to the DC bus capacitor C. bus The other end is connected to the second multiplex switch Q. A2 and the fourth multiplex switch Q B2 The source is connected to the first stage switch Q. A3 The drain of the first output filter capacitor C out1 One end and output load R Ld One end is connected, and the output load R Ld The other end is connected to the third subsequent stage switch Q. B3 The drain of the second output filter capacitor C out2 One end is connected to the second stage switch Q. A4 With the fourth stage switch Q B4 The drain and output capacitor C out1 With C out2 The other end is connected.

3. The bridge-arm multiplexing type soft-switching DC-AC converter according to claim 1, characterized in that, The modulation strategy of the bridge arm multiplexed soft-switching DC-AC converter is PWM + phase shift modulation. By coordinating the adjustment of the phase shift angle and the duty cycle, zero-voltage turn-on of all switching transistors in the converter can be achieved. Specifically, the duty cycle of all switches in the first bridge arm, second bridge arm, third bridge arm, and fourth bridge arm is a fixed value; First pre-stage switch Q1, fourth pre-stage switch Q4, first multiplexer switch Q A1 The fourth multiplex switch Q B2 Simultaneously switching on and off, the second pre-stage switch Q2, the third pre-stage switch Q3, and the second multiplex switch Q... A2 The third multiplex switch Q B1 Simultaneous on / off; The first post-stage switch Q A3 The second-stage switching transistor Q A4 The third-stage switching transistor Q B3 The fourth stage switching transistor Q B4 The timing of the multiplexed third and fourth bridge arms is satisfied: the first multiplexed switch Q A1 Prior to the first stage switching transistor Q A3 Turn off, first stage switch Q A3 Prior to the second multiplex switch Q A2 Turn off, second multiplexer switch Q A2 Prior to the second-stage switching transistor Q A4 Turn off, second stage switch Q A4 Prior to the first multiplex switch Q A1 Turn off by adjusting the first stage switching transistor Q. A3 Duty cycle D y1 and the first multiplexed switch Q A1 With the first stage switching transistor Q A3 Phase shift angle D at the activation time θ1 This causes the first stage switching transistor Q to... A3 The second-stage switching transistor Q A4 The junction capacitance ensures complete charging and discharging, guaranteeing the natural conduction of its anti-parallel diode and achieving optimal switching timing for zero-voltage turn-on; the third multiplexed switch Q... B1 Prior to the third-stage switching transistor Q B3 Turn off, third stage switch Q B3 Prior to the fourth multiplex switch Q B2 Turn off, fourth multiplexer switch Q B2 Prior to the fourth stage switching transistor Q B4 Turn off, fourth stage switch Q B4 Prior to the third multiplex switch Q B1 Turn off by adjusting the third-stage switching transistor Q. B3 Duty cycle D y2 and the third multiplex switch Q B1 With the third stage switch Q B3 Phase shift angle D at the activation time θ2 This causes the third-stage switching transistor Q to... B3 The fourth stage switching transistor Q B4 The junction capacitance ensures complete charging and discharging, guaranteeing the natural conduction of its anti-parallel diode and achieving optimal switching timing for zero-voltage turn-on; finally, by adjusting the first subsequent stage switch Q... A3 The second-stage switching transistor Q A4 The third-stage switching transistor Q B3 The fourth stage switching transistor Q B4 Voltage regulation is achieved by adjusting the duty cycle.

4. The bridge-arm multiplexing type soft-switching DC-AC converter according to claim 3, characterized in that, The duty cycle of all switches in the first, second, third, and fourth bridge arms is 50%.

5. The bridge-arm multiplexing type soft-switching DC-AC converter according to claim 1, characterized in that, The bridge arm multiplexed soft-switching DC-AC converter includes 12 switching modes, namely: Switching mode 1 [t0,t1]: At time t0, the first pre-stage switch Q1 and the fourth pre-stage switch Q4 are simultaneously turned on, and the input DC voltage source V... in The resonant inductor L is continuously powered by the first pre-stage switch Q1 and the fourth pre-stage switch Q4. r and resonant capacitor C r Resonant operation, first multiplexed switch Q A1 Second stage switch Q A4 Turn on, applied to the first inductor L a The voltage across the terminals is V bus i La Linear increase; fourth multiplexed switch Q B2 and the fourth stage switching transistor Q B4 Simultaneously, it conducts, applied to the second inductor L. b The voltage across the terminals is 0, i Lb Remain unchanged; Switching mode 2 [t1,t2]: At time t1, the resonant inductance L r and resonant capacitor C r Resonant operation, first multiplexed switch Q A1 Turn on, the second stage switch Q A4 Turn off, i La Give the second stage switching transistor Q A4 C A4 Charging, and simultaneously supplying power to the first subsequent stage switch Q. A3 C A3 Discharge; at time t2, C A4 The voltage is charged to V A Meanwhile, C A3 The voltage is reduced to zero, and the first stage switching transistor Q... A3 anti-parallel diode D A3 Natural conduction, zero-voltage turn-on of the first stage switch Q A3 The fourth multiplex switch Q B2 and the fourth stage switching transistor Q B4 Simultaneously, it conducts, applied to the second inductor L. b The voltage across the terminals is 0, i Lb Remain unchanged; Switching mode 3 [t2,t3]: At time t2, the resonant inductance L r and resonant capacitor C r Resonant operation, first multiplexed switch Q A1 and the first stage switching transistor Q A3 Turn on, applied to the first inductor L a The voltage across the terminals is V bus -V A i La Linear descent, fourth multiplexed switch Q B2 and the fourth stage switching transistor Q B4 Simultaneously, it conducts, applied to the second inductor L. b The voltage across the terminals is 0, i Lb Remain unchanged; Switching mode 4 [t3,t4]: At time t3, the resonant inductance L r and resonant capacitor C r Resonant operation, first multiplexed switch Q A1 and the first stage switching transistor Q A3 Turn on, applied to the first inductor L a The voltage across the terminals is V bus -V A i La Linear descent, fourth multiplexed switch Q B2 Turn on, fourth stage switch Q B4 Turn off, second inductor L b Give the fourth stage switching transistor Q B4 C B4 Charging, and simultaneously supplying power to the third-stage switching transistor Q. B3 C B3 Discharge, at time t4, C B4 The voltage is charged to V B Meanwhile, C B3 The voltage is reduced to zero, and the third-stage switching transistor Q... B3 anti-parallel diode D B3 Natural conduction, zero-voltage turn-on of the third-stage switching transistor Q. B3 ; Switching mode 5 [t4,t5]: At time t4, the resonant inductance L r and resonant capacitor C r Resonant operation, first multiplexed switch Q A1 and the first stage switching transistor Q A3 Turn on, applied to the first inductor L a The voltage across the terminals is V bus -V A i La Linear descent, fourth multiplexed switch Q B2 and the third-stage switching transistor Q B3 Turn on, applied to the second inductor L b The voltage across the terminals is -V bus i Lb Linear decrease; Switching mode 6 [t5,t6]: At time t5, the first pre-stage switch Q1 and the fourth pre-stage switch Q4 are simultaneously turned off, and the resonant inductor L... r The capacitors C1 and C4 of the first and fourth pre-stage switches Q1 and Q4 are charged, while the capacitors C2 and C3 of the second and third pre-stage switches Q2 and Q3 are discharged. At time t6, the voltage of C1 and C4 is charged to the input DC voltage source V. in Simultaneously, the voltages of C2 and C3 are reduced to zero, and the anti-parallel diodes D2 and D3 of the second and third pre-stage switching transistors Q2 and Q3 naturally conduct, turning on the second and third pre-stage switching transistors Q2 and Q3 with zero voltage. The first multiplexed switching transistor Q... A1 and the fourth multiplex switch Q B2 Simultaneously turn off, resonant inductor L r The transformer supplies power to the first multiplexer transistor Q. A1 and the fourth multiplex switch Q B2 C A1 and C B2 Charging, and simultaneously supplying power to the second multiplexed switch Q. A2 and the third multiplex switch Q B1 C A2 and C B1 Discharge; at time t6, C A1 and C B2 The voltage is charged into the input DC voltage source V. in Meanwhile, C A2 and C B1 The voltage is set to zero, and the second multiplexed switch Q... A2 and the third multiplex switch Q B1 anti-parallel diode D A2 and D B1 Natural conduction, zero-voltage turn-on of the second multiplexed switch Q A2 and the third multiplex switch Q B1 Resonant inductor L r Resonant capacitor C r And excitation inductance L m Resonant operation; Switching mode 7 [t6,t7]: At time t6, the second pre-stage switch Q2 and the third pre-stage switch Q3 are turned on simultaneously, and the input DC voltage source V... in The resonant inductor L is continuously powered by the second pre-stage switch Q2 and the third pre-stage switch Q3. r and resonant capacitor C r Resonant operation, second multiplexed switch Q A2 and the first stage switching transistor Q A3 Turn on, applied to the first inductor L a The voltage across the terminals is -V A i La Linear descent, third multiplexed switch Q B1 and the third-stage switching transistor Q B3 Simultaneously, it conducts, applied to the second inductor L. b The voltage across the terminals is V bus -V B i Lb Linear increase; Switching mode 8 [t7,t8]: At time t7, the resonant inductance L r and resonant capacitor C r Resonant operation, second multiplexed switch Q A2 Turn on, the first stage switch Q A3 Turn off, i La Give the first stage switching transistor Q A3 C A3 Charging, and simultaneously supplying power to the second-stage switching transistor Q. A4 C A4 Discharge; at time t8, C A3 The voltage is charged to V A Meanwhile, C A4 The voltage is reduced to zero, and the second stage switch Q... A4 anti-parallel diode D A4 Natural conduction, zero-voltage turn-on of the second stage switch Q A4 The third multiplex switch Q B1 and the third-stage switching transistor Q B3 Simultaneously, it conducts, applied to the second inductor L. b The voltage across the terminals is V bus -V B i Lb Linear increase; Switching mode 9 [t8,t9]: At time t8, the resonant inductance L r and resonant capacitor C r Resonant operation, second multiplexed switch Q A2 Second stage switch Q A4 Turn on, applied to the first inductor L a The voltage across the terminals is 0, i La The third multiplexer switch Q remains unchanged. B1 and the third-stage switching transistor Q B3 Simultaneously, it conducts, applied to the second inductor L. b The voltage across the terminals is V bus -V B i Lb Linear increase; Switching mode 10[t9,t 10 At time t9, the resonant inductance L r and resonant capacitor C r Resonant operation, second multiplexed switch Q A2 Second stage switch Q A4 Turn on, applied to the first inductor L a The voltage across the terminals is 0, i La The third multiplexer switch Q remains unchanged. B1 Turn on, the third stage switch Q B3 Turn off, second inductor L b Give the third stage switching transistor Q B3 C B3 Charging, and simultaneously supplying power to the fourth subsequent switching transistor Q. B4 C B4 Discharge, at time t4, C B3 The voltage is charged to V B Meanwhile, C B4 The voltage is reduced to zero, and the fourth stage switch Q is... B4 anti-parallel diode D B4 Natural conduction, zero-voltage turn-on of the fourth stage switch Q B4 ; Switching mode 11[t 10 ,t 11 ]: In t 10 At time, the resonant inductance L r and resonant capacitor C r Resonant operation, second multiplexed switch Q A2 Second stage switch Q A4 Turn on, applied to the first inductor L a The voltage across the terminals is 0, i La The third multiplexer switch Q remains unchanged. B1 and the fourth stage switching transistor Q B4 Simultaneously, it conducts, applied to the second inductor L. b The voltage across the terminals is V bus i Lb Linear increase; Switching mode 12[t] 11 ,t 12 ]: In t 11 At that moment, the second pre-stage switch Q2 and the third pre-stage switch Q3 are simultaneously turned off, and the resonant inductor L... r The capacitors C2 and C3 of the second and third pre-stage switches Q2 and Q3 are charged, while the capacitors C2 and C4 of the first and fourth pre-stage switches Q1 and Q4 are discharged. At time t6, the voltage across C2 and C3 is charged to the input DC voltage source V. in Simultaneously, the voltages of C1 and C4 are reduced to zero, and the anti-parallel diodes D1 and D4 of the first and fourth pre-stage switching transistors Q1 and Q4 naturally conduct, turning on the first and fourth pre-stage switching transistors Q1 and Q4 at zero voltage. The second multiplexed switching transistor Q... A2 and the third multiplex switch Q B1 Simultaneously turn off, resonant inductor L r The transformer supplies power to the second multiplexer transistor Q. A2 and the third multiplex switch Q B1 C A2 and C B1 Charging, and simultaneously supplying power to the first multiplexed switch Q. A1 and the fourth multiplex switch Q B2 C A1 and C B2 Discharge; at time t6, C A2 and C B1 The voltage is charged into the input DC voltage source V. in Meanwhile, C A1 and C B2 The voltage is reduced to zero, and the first multiplexed switch Q... A1 and the fourth multiplex switch Q B2 anti-parallel diode D A1 and D B2 Natural conduction, zero-voltage turn-on of the first multiplexer switch Q A1 and the fourth multiplex switch Q B2 Resonant inductor L r Resonant capacitor C r And excitation inductance L m Resonant operation.

6. A modulation method based on the bridge arm multiplexing soft-switching DC-AC converter of claim 1, characterized in that, The modulation method employs a PWM + phase-shift fusion modulation strategy. By coordinating the adjustment of the duty cycle and turn-on / turn-off phase shift angle of the switching transistors, it achieves zero-voltage turn-on soft switching for all switching transistors in the converter, while simultaneously enabling wide-range voltage regulation of the output voltage. The modulation method specifically includes the following steps: S1. Fix the duty cycle of all switches in the first bridge arm, the second bridge arm, and the multiplexed third and fourth bridge arms of the full-bridge LLC resonant converter to 50% to maintain the fixed frequency operation mode. S2, controls the first pre-stage switch Q1, the fourth pre-stage switch Q4, and the first multiplex switch Q. A1 The fourth multiplex switch Q B2 Synchronous switching controls the second pre-stage switch Q2, the third pre-stage switch Q3, and the second multiplex switch Q. A2 The third multiplex switch Q B1 Synchronous switching on and off, with the two sets of switching transistors in a complementary conduction state; S3, controls the first-stage switching transistor Q. A3 The second-stage switching transistor Q A4 The first multiplexer switch Q satisfies the strict turn-on and turn-off timing requirements of the third bridge arm. A1 Prior to the first stage switching transistor Q A3 Turn off, first stage switch Q A3 Prior to the second multiplex switch Q A2 Turn off, second multiplexer switch Q A2 Prior to the second-stage switching transistor Q A4 Turn off, second stage switch Q A4 Prior to the first multiplex switch Q A1 Turn off; by adjusting the first stage switching transistor Q A3 Duty cycle D y1 and the first multiplexed switch Q A1 With the first stage switching transistor Q A3 Phase shift angle D at the activation time θ1 This causes the first stage switching transistor Q to... A3 The second-stage switching transistor Q A4 The junction capacitance is fully charged and discharged, ensuring that its anti-parallel diode conducts naturally, achieving zero-voltage turn-on; S4, controls the third-stage switching transistor Q. B3 The fourth stage switching transistor Q B4 The third multiplexer switch Q satisfies strict turn-on and turn-off timing requirements with the fourth bridge arm. B1 Prior to the third-stage switching transistor Q B3 Turn off, third stage switch Q B3 Prior to the fourth multiplex switch Q B2 Turn off, fourth multiplexer switch Q B2 Prior to the fourth stage switching transistor Q B4 Turn off, fourth stage switch Q B4 Prior to the third multiplex switch Q B1 Turn off; by adjusting the third-stage switching transistor Q. B3 Duty cycle D y2 and the third multiplex switch Q B1 With the third stage switch Q B3 Phase shift angle D at the activation time θ2 This causes the third-stage switching transistor Q to... B3 The fourth stage switching transistor Q B4 The junction capacitance is fully charged and discharged, ensuring that its anti-parallel diode conducts naturally, achieving zero-voltage turn-on; S5. By coordinating the phase shift angle and duty cycle adjustments in steps S3 and S4, all switches in the converter's front-end, multiplexing, and rear-end stages achieve zero-voltage soft-switching; finally, by adjusting the first rear-end switch Q... A3 The second-stage switching transistor Q A4 The third-stage switching transistor Q B3 The fourth stage switching transistor Q B4 The duty cycle is adjusted to achieve wide-range continuous voltage regulation of the output voltage.

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