A novel adaptive hysteresis band current control using a DSP for a power factor corrected on-line UPS

Hysteresis current control is one of the simplest and most popular techniques used to achieve unity power factor for an on-line uninterruptible power supply (UPS). However the conventional fixed band hysteresis control has a variable switching frequency which causes serious EMI problems and dead zones in the zero crossings of input current waveforms as well as high stress on power devices. In this paper, the adaptive hysteresis band current control strategy is proposed, where the hysteresis band is controlled in real time as variations of input current, input voltage and output voltage to keep the switching frequency constant at any operation conditions. This novel current control method with a digital signal processor (DSP) implementation is proposed in current control loop of power factor corrected converter (PFC) used in an on-line UPS. The proposed current control technique is verified by simulations and experiments.