Discharge-lamp lighting circuit

摘要

A discharge-lamp lighting circuit designed to decrease the size of a driving circuit for driving switching elements constituting a DC-AC converter circuit 4 therein and to reduce the manufacturing cost likewise. With a bridge type circuit arrangement having a plurality of switching elements SW1 to SW4 in the DC-AC converter circuit 4, a plurality of bipolar transistors are used to form a driving circuit for controlling the on-off conditions of the elements SW1 and SW3 positioned on the high voltage side out of the switching elements. At this time, a plurality of transistors (22 and 23) are connected in series and the on-off conditions of the switching element SW1 are controlled by the transistor 23 on the low voltage side. Moreover, there is provided a resistance element 26 so as to limit current flowing from the node a between the switching elements forming the arms of the bridge to the transistor. Switching speed of the proper transistor 23 is also improved by controlling the base current flowing into the transistor.