Patent ID: 6385068
Filing Date: 2002-05-07
Classification: H05B

Abstract:
A circuit device for supplying an alternating current of frequency f to a lamp, which circuit device is provided with a DC-AC converter comprisinginput terminals for connecting the circuit device to a supply voltage source supplying a DC voltage, a first branch including a series arrangement of a first switching element and a second switching element, a control circuit coupled to respective control electrodes of the switching elements for rendering the switching elements conducting and non-conducting, a load branch shunting one of the switching elements and provided with a series arrangement of an inductive element and terminals for accommodating the lamp, characterized in that the control circuit generates a control signal at a frequency f during operation of the lamp, for successively rendering the first switching element conducting during a first time interval and the second switching element during a second time interval in each first half period of the control signal, each one of the switching elements being non-conducting during the remaining part of the first half period of the control signal, and for successively rendering the second element conducting during a third time interval and the first switching element during a fourth time interval in each second half period of the control signal, each one of the switching elements being non-conducting during the remaining part of the second half period of the control signal, and in that the control signal is additionally provided with a dimming circuit for setting the duration of at least one of the two time intervals during each half period of the control signal wherein one of the switching elements is conducting.