Abstract
In High Voltage Flyback converters, the dominant factor that influences a converter operation is the parasitic capacitance. A significant portion of input energy is utilised 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 remain significant in High Voltage Low Power (HVLP) applications. This energy transfer phenomena involving parasitic capacitances results in reduced fraction of input energy reaching the load in every cycle, thereby resulting in an apparent deviation in converter operating point compared to ideal flyback in case of resistive loads. An analytical energy based model is derived including the effect of parasitic capacitances, valid for steady state and dynamics of High Voltage Low Power (HVLP) flyback converters feeding resistive loads. The influence of parasitic capacitances on switch voltage of the converter is exploited to achieve Zero Voltage Switching (ZVS) thereby minimising 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 load.
