High-Switching-Frequency TCM Digital Control for Bidirectional-Interleaved Buck Converters Without Phase Error for Battery Charging

This article proposes a high-performance, high-switching-frequency triangular-conduction-mode (TCM) bidirectional-interleaved buck converter for battery charging using digital control. Accurate conditions for achieving zero-voltage switching (ZVS) without zero-crossing detection (ZCD) are derived while considering the nonlinear parasitic capacitance of the switch components. This article also optimizes the method of calculating the switching frequency to reduce the delay time of pulsewidth modulation, thereby enhancing system stability. The conventional control method has inadequate resolution in the phase shift register of the digital controller under high switching frequency, hindering perfect interleaving of the two phases at 180°, which affects the characteristics of current ripple offset. The proposed control method effectively reduces the phase error between the two phases in an interleaving structure under high-frequency operation. In this way, full-range ZVS can be achieved when the circuit operates at the correct switching frequency. ANSYS Q3D Extractor software is employed to simulate the impedances of the power loops and investigate parasitic parameters, enabling optimization of the layout and modification of the switching frequency. An experimental prototype of a bidirectional buck converter using GaN switches was implemented with an output power of 1 kW, an input voltage of 66 V, an output voltage of 35-50 V, a switching frequency of 350 kHz-1 MHz, a highest efficiency of 97.52%, and a power density of 10 W/cm
³
.