Starting (ignition) device for a discharge lamp

摘要

A device for starting a discharge lamp is provided with an invertor circuit (3) which causes an input voltage supply (2) to generate a voltage required for the discharge lamp (1), a rectifier smoothing circuit (4)for rectifying and smoothing the output of the invertor circuit (3), a feedback control circuit (8) for calculating the required power for the discharge lamp (1) for the purpose of controlling the feedback control circuit (8) using a feedback method, a polarity-switching circuit (9) for switching the polarity of the rectified and smoothed output for the purpose of applying the output with a low-frequency square wave to the discharge lamp (1), and a starter (11) for superposing a high-voltage pulse on the discharge lamp (1) when the discharge lamp (1) is started. For this purpose, the device furthermore comprises an overcurrent control circuit (14) for determining an overcurrent flowing in the discharge lamp (1) for the purpose of causing the polarity-switching circuit (9) to carry out a radio-frequency chopper operation together with the low-frequency operation only over an interval during which an overcurrent flows, so that the life of the discharge lamp (1) is prolonged by suppressing the overcurrent flowing in the discharge lamp (1) and preventing wear of its electrodes.