Research On Digital Controlled Forward Converter With Active-Clamp Reset

The secondary power supply is very important in the area of communication power supply and industry power supply. Low voltage and high current DC/DC converter is the most rapid development branch of secondary power supply. In the thesis, the forward converter with active-clamp reset was took as a research and analysis object, when the duty ratio is above 0.5, the transformer can be operated in the NO.1 and NO.3 quadrant, as a matter of this fact, self-drive synchronous rectify and ZCZVS as well as high efficiency could be achieved. In the steady state, the topology of low voltage and high current has most advantages, however, The peak current of transformer and the peak voltage endured by the power switch would be greatly affected by the loop band width of forward converter with active-clamp reset while the transient change of the line voltage or output load, and it would cause hidden trouble of components breaking down. The transient characteristics of forward converter with active-clamp and stability of original side components couldn't be satisfied at the same time, due to fixed loop band width of fixed loop feeder under the analog control way. In order to solve those problems above, digital control way was adopted in the thesis, as a result, the peak voltage bore by the power switches of original side and peak current of transformer could be controlled in an appropriate range via changing different PID control ways, providing different loop band width for the forward converter with active-clamp reset. In this way, the better transient response of power supply system could be derived and the stability of original side components could also be guaranteed.The principle and parameters of the circuit were analyzed and calculated in detail. The digital power supply chips of type Si825x which manufactured by Silicon company was selected to build the digital control circuit. According to different transient status, the corresponding digital feeder was designed, and realized by the software programming in the end. The well-designed system of forward converter with active-clamp reset was simulated by the software of MathCad and Matlab respectively. The simulation results verified that the digital control way has a better performance to analog control way when controlling the forward converter with active-clamp reset.