DIMMING OF LIGHTING DEVICES

The invention relates to dimming of lighting devices. Lighting devices, in particular LED lamps, should be able to be effectively dimmed in the phase-cut operation. For this purpose, a dimming device is provided for the power control of a lighting device driven by alternating current, the dimming device is provided with a control device for driving the lighting device by means of phase-cut control, the control device is provided with a bidirectional switch which has two switching devices for applying a supply alternating voltage to the lighting device. The control device is designed for the common switching-on of the two switching devices in each half-wave of the supply alternating voltage and for switching off one of the two switching devices before an expected current zero crossing. A measuring device is connected to the control device in order to measure the voltage across the switched-off switching device. The control device is also designed to determine a current zero crossing for the phase-cut control on the basis of the measured voltage.