Control unit for the power supplied to an incandescent lamp

A control unit is described for the power supplied to an incandescent lamp, which control unit applies pulses to the incandescent lamp, the width of which pulses is varied in accordance with the desired power, while the pulse repetition frequency (pulse repetition rate) remains fixed. The invention is distinguished by the fact that the polarity of the pulses is alternately positive and negative. In the case of a preferred exemplary embodiment of the invention, the pulse repetition frequency is between several 100 Hz and several kHz. The polarity reversal, according to the invention, of the pulses prevents crystalline structures building up on the lamp element, which would result in the emission behaviour being changed.