Inverter for fluorescent lamp without output transformer - uses power transistors connected in series in bridge configuration and controlled by transformer

摘要

The lamp (17) is directly connected as the load in a variation on a four-arm half controlled bridge configuration utilising power transistors (19,20) as the switching element, and capacitors (15,16) as the uncontrolled arms. The DC supply (45,13,14) to the inverter is injected at the top of the bridge and at the mid-point of the capacitor arms (15,16) of the bridge. The power transistors (19,20) are switched by transformer coupling (23) into their base-emitter junction signals from a magnetically coupled blocking oscillator, (29,32) the output of which is dedicated to driving the main transistors (19,20). Another blocking oscillator circuit (46,51,54) is used to convert the DC supply to a high voltage AC supply which is rectified (13,14) to produce the DC rail of the inverter.