A transformer-less power supply is provided for ozone generation. The power supply advantageously reduces costs and increases reliability of ozone generators. The power supply provides a first AC voltage from a power source to a resonant circuit and the resonant circuit provides a second AC voltage to the ozone generating unit, the second AC voltage being greater than the first AC voltage. A controller for the power supply that adapts to the resonance of the circuit to provide control with a wide tolerance for the high Q circuit component values of the circuit.