Abstract: A dimmer logic for fluorescent lamps is described which operates after the principal of a two-point circuit with two stable operating points, where in dimmer operation periodic changes between the two operating points takes place. By periodically switching on and off the fluorescent lamp the average brightness of the fluorescent lamp is reduced. The dimmer logic can be extended by sensor inputs for current and voltage to control the voltage, current and power. By appropriate design of the dimmer logic a control and protection circuit for overcurrent, overvoltage and overpower can be realized.

Abstract: A dimmer circuit for gas discharge lamps, having an electronic ballast equipped with a first converter circuit which first transforms an applied voltage by means of switching transistors into a first high-frequency alternating voltage. This first high-frequency alternating voltage is fed indirectly or directly to the gas discharge lamp. The dimmer circuit also includes a second converter circuit connected upstream. The second converter circuit is arranged so as to transform an input voltage into a second high-frequency alternating voltage and is also arranged so as to rectify the second high-frequency alternating voltage to produce a rectified output voltage. After rectification, the rectified output voltage is fed to the first converter circuit as the above-mentioned applied voltage. The second converter circuit contains switching means which, operated manually or by remote control, influence the magnitude of the rectified output voltage from the second converter circuit.