Research on intermediate bus converter with asymmetrical half-bridge flyback structure

The Intermediate Bus Converter (IBC) can realize fixed ratio isolation conversion of bus voltage. Because it works in the open-loop or semi-open-loop control mode, the duty cycle is fixed, and soft-switching can be achieved, so it has a very high efficiency and power density. It can be cascaded with point-of-load power supplies to form an intermediate bus architecture (IBA), which is widely used in the fields of communication and computing. Based on the voltage regulation principle and technical characteristics of the asymmetric half-bridge flyback structure, this paper adopts the method of feedforward control to realize the open-loop voltage regulation control of IBC, and solved the problem of poor output voltage stability of IBC power supply, the zero-voltage switching (ZVS) operation on power switches and zero-current switching (ZCS) operation on output rectifier switch are also realized, so the switching loss is greatly reduced and the conversion efficiency is improved. Firstly, this paper analyzes the principle of the structure in detail, and the conditions of soft-switching are derived, the design method of the parameters of the circuit is also given. Then, according to the formula of the transmission gain of the structure, a voltage feedforward PWM control scheme is designed, and the simulation verification is carried out by PSIM software. Finally, a 36~60 V input, 12V output, 100 W/300 kHz prototype is built. The experimental results show that through the feedforward voltage regulation control, the variation of output voltage in the entire input range can limited to 80 mV, and the efficiency is above 90%, the peak efficiency reaches 91.25%, and the power switch is turned on with zero voltage, the output rectifier switch is turned on with zero current.