Abstract: A method is described for driving a fluorescent lamp (L) with variable light output within a dimming range between a low dimming level and a high dimming level. The lamp power and the lamp current are monitored. At high dimming level the lamp control is based on current control; at low dimming level, the lamp control is based on power control; at intermediary levels the lamp control is based on both current and power control. A first measuring signal (Ilamp) indicating lamp current and a second measuring signal (Plamp) indicating lamp power are obtained. An error signal (Serr) is calculated as a function of the said two measuring signals and as a function of dim level. With increasing dim level, the contribution of the first measuring signal (Ilamp) to the error signal (Serr) increases while the contribution of the second measuring signal (Plamp) to the error signal (Serr) decreases.

Abstract: A method is described for driving a fluorescent lamp (L) with variable light output within a dimming range between a low dimming level and a high dimming level. The lamp power and the lamp current are monitored. At high dimming level the lamp control is based on current control; at low dimming level, the lamp control is based on power control; at intermediary levels the lamp control is based on both current and power control. A first measuring signal (Ilamp) indicating lamp current and a second measuring signal (Plamp) indicating lamp power are obtained. An error signal (Serr) is calculated as a function of the said two measuring signals and as a function of dim level. With increasing dim level, the contribution of the first measuring signal (Il-amp) to the error signal (Serr) increases while the contribution of the second measuring signal (Plamp) to the error signal (Serr) decreases.

Abstract: An electronic ballast for supplying a lamp load is described. The electronic ballast comprises an inverter arranged in a half-bridge configuration for providing an AC voltage and at least one lamp load circuit. The inverter comprises an upper switch, connected to a DC terminal for receiving a DC supply voltage, and a first lower switch arranged in a half-bridge configuration for generating an AC voltage at an inverter terminal of the inverter. A first diode and a second lower switch are connected in series. This series arrangement is connected in parallel with the first lower switch. A lamp load circuit for supplying the lamp load is connected to a node between the first diode and the second lower switch. When the inverter supplies a fluorescent lamp, and the lamp load circuit comprises a heating circuit for heating an electrode of the fluorescent lamp, the heating circuit includes a heating transformer and a second lower switch connected in parallel with the primary winding of the transformer.

Abstract: Power converter with a controllable first switch and a diode and a controllable second switch and a second diode, a transformer with a primary winding and a secondary winding, of which the secondary winding forms at least part of a control circuit for the first switch. As a result of an alternating voltage across the primary winding, a synchronously alternating voltage is induced in the secondary winding, which can be used to control the first switch essentially synchronously with the second switch.

Abstract: Power converter with a controllable first switch and a diode and a controllable second switch and a second diode, a transformer with a primary winding and a secondary winding, of which the secondary winding forms at least part of a control circuit for the first switch. As a result of an alternating voltage across the primary winding, a synchronously alternating voltage is induced in the secondary winding, which can be used to control the first switch essentially synchronously with the second switch.

Abstract: A switched mode power supply comprises a half bridge circuit or a full bridge circuit. A resonant circuit is connected to the bridge circuit and comprises an inductive element (105, 208): end a capacitive element (106, 209) connected in series, whereby the resonant circuit has a resonant frequency. The rate of change of a voltage across the resonant circuit is measured. A switching frequency of the switching elements is controlled for lowering the rate of change of the voltage across the resonant circuit to a predetermined minimum value. In ;:i no-load condition, the switching frequency of the switching elements is set to an operating frequency which is higher than the resonant frequency of the resonant circuit. In a load condition, the switching frequency of the switching elements is lowered to the resonant frequency of the resonant circuit.

Abstract: Switching arrangement for igniting and operating of a high-pressure discharge lamp which is provided with: input terminals for connecting a power source, output terminals for connecting the lamp which is ignited and operated by the arrangement, a flyback converter having a semiconductor switching element and a transformer of which a primary coil is electrically connected to one of the input terminals and a secondary coil having a secondary coil voltage is connected to one of the output terminals, a control circuit for generating a switching signal for control of the semiconductor switching element in a conducting or a non-conducting switching state, element M for generating a control signal S intended for the control circuit, which signal S depends on the secondary coil voltage and on a current through the secondary coil.

Abstract: Switching arrangement for igniting and operating of a high-pressure discharge lamp which is provided with: