Abstract: A circuit for converting a direct current voltage into an alternating current voltage includes a buck converter, a resonant DC voltage/DC voltage converter, a DC voltage/AC voltage inverter, and a DC link capacitor. The buck converter generates a DC current according to an input voltage generated by a voltage source operating at an optimal operation point. The resonant DC voltage/DC voltage converter converts the input voltage to a DC voltage according to a switch clock and a resonant frequency determined by a resonant capacitor and a resonant inductance of the resonant DC voltage/DC voltage converter. The DC voltage/AC voltage inverter converts the DC voltage and outputs an AC voltage to an AC power supply network. The DC link capacitor adjusts power outputted by the DC voltage/AC voltage converter to regulate the DC voltage.

Abstract: A ballast according to the present invention operates in an ignition state, a warm-up state, and a steady state for igniting and powering a lamp. The ballast comprises an igniter that ignites the lamp during the ignition state and a switching power inverter, for example, a full bridge DC-AC inverter implemented with MOSFET switching transistors, that powers the lamp during the warm-up and steady states. The switching power inverter, which drives the igniter, operates at a first switching frequency during the ignition state and operates at a second switching frequency during the steady state. Preferably, the first switching frequency, which in one exemplary embodiment is in the kHz range, is higher than the second switching frequency.

Abstract: A ballast according to the present invention operates in an ignition state, a warm-up state, and a steady state for igniting and powering a lamp. The ballast comprises an igniter that ignites the lamp during the ignition state and a switching power inverter, for example, a full bridge DC-AC inverter implemented with MOSFET switching transistors, that powers the lamp during the warm-up and steady states. The switching power inverter, which drives the igniter, operates at a first switching frequency during the ignition state and operates at a second switching frequency during the steady state. Preferably, the first switching frequency, which in one exemplary embodiment is in the kHz range, is higher than the second switching frequency.