MATLAB Simulation of Zero-Voltage Switching and Soft Turn-off in Phase-Shifted Full-Bridge Converters

The Phase-Shifted Full-Bridge (PSFB) topology is a common power electronics structure widely used in high-power DC-DC converters. Through phase-shift control, it achieves zero-voltage switching (ZVS) turn-on and soft turn-off of switching devices, thereby reducing switching losses and improving efficiency. MATLAB/Simulink serves as an ideal platform for such simulations, enabling validation of control strategies through built-in power electronics libraries and customized modeling approaches. Working Principle of Phase-Shifted Full-Bridge Converters PSFB converters utilize phase difference adjustment between bridge arm drive signals along with resonant inductance and parasitic capacitance to achieve ZVS. Specifically, a deliberate phase delay between leading-leg and lagging-leg switches allows current to charge/discharge parasitic capacitors during switching transitions, creating zero-voltage conditions. Soft turn-off is achieved by optimizing dead-time and resonant parameters to ensure gradual voltage rise during switch turn-off, minimizing voltage-current overlap losses. In MATLAB implementation, this involves precise timing control through PWM generation blocks and parasitic parameter modeling using Simulink's capacitor and inductor components. Key Aspects of MATLAB Simulation Model Construction: Build the main PSFB circuit in Simulink incorporating MOSFET/IGBT switches, resonant inductors, transformers, and output rectification sections using SimPowerSystems library blocks. Control Strategy Implementation: Employ PWM generator modules with phase-shift capability, typically using MATLAB's Phase-Shifted PWM block or custom MATLAB Function blocks to dynamically adjust phase differences and observe ZVS effects. Parameter Optimization: Systematically configure dead-time settings, resonant inductance values, and load conditions through parameter sweeps and optimization algorithms to ensure wide ZVS operating ranges. Simulation Analysis: Monitor switch voltage (Vds) and current waveforms using Simulink scopes to verify voltage dropping to zero before turn-on and suppressed voltage spikes during turn-off. Analysis of Simulation Results Successful simulations should demonstrate: Vds ≈ 0 at turn-on instant for both leading and lagging leg switches, confirming ZVS achievement. Gradual voltage rise slope during turn-off transitions, indicating effective soft switching. Maintained ZVS performance under varying load conditions, validating control strategy robustness through multiple test scenarios. MATLAB simulations provide intuitive verification of PSFB soft-switching characteristics, offering theoretical foundations for practical hardware design while enabling algorithm testing through Simulink's co-simulation capabilities with actual control hardware.