Building a DIY Sine Wave Inverter

A pure sine wave inverter is one of the most ambitious power electronics projects for a hobbyist. This is high-power, mains-voltage work — safety first.

The architecture: a DC-DC boost stage converts 12V battery to 400V DC bus. An H-bridge inverter stage generates a PWM-modulated sine at 50Hz/60Hz from the 400V bus. An LC filter removes the PWM switching frequency, leaving a clean 230V/120V sine wave output.

The control: a lookup table of 256 sine values drives the H-bridge via SPWM (sinusoidal PWM). The switching frequency is 20kHz, well above audio. Deadtime control between H-bridge legs prevents shoot-through. Total harmonic distortion with a good LC filter is under 3% — cleaner than many commercial UPS units.