This simple 12VDC to 220VAC inverter circuit produces an AC output at line frequency and voltage. The 555 is configured as a low-frequency oscillator, tunable over the frequency range of 50 to 60 Hz by Frequency potentiometer R4. The 555 feeds its output (amplified by Q1 and Q2) to the input of transformerT1, a reverse-connected filament transformer with the necessary step-up turns ratio.
Capacitor C4 and coil L1 filter the input to T1, assuring that it is effectively a sine wave. Adjust the value of T1 to your voltage.