Discharge lamp ballast circuit with duty cycle dimming control

摘要

A circuit for supplying a discharge lamp, comprising a converter for generating a high-frequency current at a frequency f from a supply voltage and a circuit portion I for adjusting the power consumed by the discharge lamp through adjustment of the frequency. The circuit portion I is provided with a circuit portion II for low-frequency square-wave modulation of the frequency f and for the adjustment of the duty cycle of the square-wave modulation. As a result, the discharge lamp can be dimmed over a very wide range without striations or moding occurring and without undesirable shifts in the color point of the light.