Patent ID: 6445140
Filing Date: 2002-09-03
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 rendering the first switching element, in each first half period of the control signal, successively conducting, non-conducting and conducting during, respectively, a first, a second and a third time interval, the second switching element always being conducting when the first switching element is non-conducting, and non-conducting when the first switching element is conducting, and for rendering the second switching element, in each second half period of the control signal, successively conducting, non-conducting and conducting during, respectively, a fourth, a fifth and a sixth time interval, the first switching element always being conducting when the second switching element is non-conducting, and non-conducting when the second switching element is conducting, and in that the control circuit is further provided with a dimming circuit for setting the duration of the second and the fifth time interval.