Duty cycle design of battery equalizer based on multi-winding pulse transformer

For the inequality phenomenon of battery packs in electric vehicles, a charge equalization converter using flyback multi-winding transformer in electric vehicle battery system was designed. The principal and circuit of the equalization system were particularly presented, as well as two balancing strategies named Top balancing and Bottom balancing. Taking account of the maximum work duty cycle, the way to design the system control PWM was described, and the PSIM simulation model of the equalization circuit was built. The simulation and experiment results demonstrate that both primary and secondary winding achieve the maximum control duty cycle and the peak work equalization current, so the effectiveness of the PWM design method for equalizer is verified.