I am converting DC voltage to AC via H-bridge inverter. I am using bipolar SPWM signals to control IGBT switches of H-bridge. When i connect 470ohm load to output terminal it retains sine shape. when i decrease load to 70ohm, sine wave distorts at zero crossing. how to avoid this? attached figure of both results.(1)with 470ohm as load.(2)with 70ohm as load.
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