Sinewave inverter

Topology:

Its a single stage conversion. The low voltage is passed through a transformer low voltage winding using a 4-MOSFET H-bridge. Due to the turns ratio of the transformer, the voltage is stepped up to 230V. Using additional voltage control, the AC voltage can be maintained at 230V from no load to full load.

The other popular topology of inverter is a 2-stage conversion, where the low voltage DC is stepped up to about 325V DC using a DC-DC converter. Later the 325V DC is converted to AC using full bridge inverter. Since the DC-DC converter works at high frequency (100KHz), the size of transformer is reduced. Also, due to the high frequency operation, the transformer cores are made of ferrite, which is not suitable for single stage conversion, where they tend to saturate (lower frequency).

Video:

Voltage Waveforms:

From all voltage waveform, notice how the PWM increases from low (0%) to highest (98%) and then falls back to 0%. Then it repeats in the negative half cycle. The dead zone that is noticed around the zero cross (where sine wave crosses from positive to negative or vice versa) can be eliminated by keeping the lowest duty cycle to a higher value (higher than 0%). Because, the PWM is run in complementary mode, the dead time setting will eat into the low values of duty cycle making them non-existent. Hence, for such, the lowest value of duty cycle can be increased.