Lamp parameter detection in a full bridge circuit
Publication Date: 2004-Sep-29
The IP.com Prior Art Database
Lamp parameter detection in a full bridge circuit.
The power converter topology as shown in the figure is often used as a power supply for HID lamps. Different switching patterns can be applied for the power switches T1 -T4. The switches can for instance be controlled in the Full Bridge Commutating Forward mode, in which switching elements T1 and T2 are respectively controlled at a high frequency during successive low frequency half periods. In the first low frequency half period, T4 is maintained conductive and T3 non-conductive, while in the second half period T4 is maintained non-conductive and T3 conductive. Thus an efficient operation of the HID-lamp can be realized.
A drawback associated with this topology is that it is difficult to measure lamp voltage and lamp current, because the lamp is floating. This problem can be overcome by measuring the lamp voltage and/or lamp current at the terminals indicated in the figure by means of arrows (Ila and Vla) only when T4 is conducting.