Discharge lamp operating circuit with wide range dimming control

摘要

A DC/AC convert circuit for operating a discharge lamp includes a branch A having ends suitable for connection to a DC voltage source and comprising a series circuit of two switching elements for generating a periodic voltage by being conducting and non-conducting alternately at a frequency f, each switching element being shunted by a diode. A control circuit is coupled to control electrodes of the switching elements for rendering the switching elements conducting and non-conducting alternately at the frequency f. A load branch B shunts one of the switching elements and comprises an inductor. The discharge lamp is coupled to the load branch B. The power consumed by the discharge lamp is adjusted by adjusting the value of the difference Tt-Td, in which Tt is a time interval during which one of the switching elements is conducting during a half cycle of the periodic voltage, and Td is the time interval during which a diode is conducting during the same half cycle of the periodic voltage. Stable operation of the discharge lamp is achieved over a wide range of the adjustable power.