A power supply, comprising: a transformer-less oscillator comprising a power source (320, 410, 710) and a resonant circuit (330, 420, 720), the resonant circuit (330, 420, 720) having a q-factor and being directly coupled to the power source (320, 410, 710); and a controller for controlling the power source (320, 410, 710), wherein the resonant circuit (330, 420, 720) comprises a resonant inductor (422, 722) coupled in series with a resonant capacitor (424, 724), the resonant capacitor (424, 724) configured to be directly coupled in parallel with an ozone generating unit, where the q-factor is greater than or equal to 10, wherein the controller is configured to provide signals to the power source (320, 410, 710) that allow the resonant circuit (330, 420, 720) to operate at its resonant frequency and to control the power source (320, 410, 710) to tune an initial frequency of a first AC voltage from the power source (320, 410, 710) to the maximum operating frequency of the resonant circuit (320, 410, 710), and to approach the frequency of the first AC voltage to a resonant frequency of the resonant circuit (320, 410, 710) and obtain a second AC voltage having a desired voltage magnitude by comparing a sensed input DC current inputted to the power source (320, 410, 710) with a set point DC current, the power source (320, 410, 710) being configured to provide the first AC voltage to the resonant circuit (330, 420, 720), and the resonant circuit (330, 420, 720) being configured to provide the second AC voltage to the ozone generating unit, the second AC voltage being greater than the first AC voltage and powering the ozone generating unit. a transformer-less oscillator comprising a power source (320, 410, 710) and a resonant circuit (330, 420, 720), the resonant circuit (330, 420, 720) having a q-factor and being directly coupled to the power source (320, 410, 710); and a controller for controlling the power source (320, 410, 710), wherein the resonant circuit (330, 420, 720) comprises a resonant inductor (422, 722) coupled in series with a resonant capacitor (424, 724), the resonant capacitor (424, 724) configured to be directly coupled in parallel with an ozone generating unit, where the q-factor is greater than or equal to 10, wherein the controller is configured to provide signals to the power source (320, 410, 710) that allow the resonant circuit (330, 420, 720) to operate at its resonant frequency and to control the power source (320, 410, 710) to tune an initial frequency of a first AC voltage from the power source (320, 410, 710) to the maximum operating frequency of the resonant circuit (320, 410, 710), and to approach the frequency of the first AC voltage to a resonant frequency of the resonant circuit (320, 410, 710) and obtain a second AC voltage having a desired voltage magnitude by comparing a sensed input DC current inputted to the power source (320, 410, 710) with a set point DC current, the power source (320, 410, 710) being configured to provide the first AC voltage to the resonant circuit (330, 420, 720), and the resonant circuit (330, 420, 720) being configured to provide the second AC voltage to the ozone generating unit, the second AC voltage being greater than the first AC voltage and powering the ozone generating unit.