Modeling, Analysis, and Implementation of High Voltage Low Power Flyback Converter Feeding Resistive Loads

In High Voltage flyback converters, the dominant factor that influences a converter operation is the parasitic capacitance. A significant portion of input energy is utilized in charging the parasitic capacitances of the circuit, which is circulated back to the source at the end of every switching cycle. The circulating energy is a function of output voltage, load power, and parasitic capacitances and remains significant in High Voltage Low Power (HVLP) applications. This energy transfer phenomenon involving parasitic capacitances results in a reduced fraction of input energy reaching the load in every cycle, thereby resulting in an apparent deviation in the converter operating point compared to ideal flyback in case of resistive loads. An analytical energy-based model is derived, which includes the effect of parasitic capacitances, and is valid for steady state and dynamics of HVLP flyback converters feeding resistive loads. The influence of parasitic capacitances on the switch voltage of the converter is exploited to achieve Zero Voltage Switching (ZVS), thereby minimizing the turn- on loss. The proposed analytical model is verified through simulation and experimental results on 1.5 kV/ 5 W and 1.5 kV/ 200 mW resistive loads.