Push-pull transistor inverter system - operates with trigger delay to prevent short circuits during switching operation

摘要

The power switching transistors (1-4) are controlled by signals from a pulse transformer (19) connected to the control unit (21). To prevent short circuits due to turning on an incoming transistor when the outgoing one is still in a conducting state during turn off signals are taken from current transformers (5-8) which prevent the incoming transistor from turning on when the outgoing one is still passing current. This is achieved by using the current signal to trigger a transistor (22, 25) and diode (23, 26) to short circuit part of the pulse transformer primary and thus prevent the transmission on of a turn on signal. The resistor (24, 27) in series with these logic transistors (22, 25) is chosen such that the voltage across, the part of the primary winding (20) is held to about 0.5 volt. Any pulse from the secondary windings (15-18) is then insufficient to turn on an incoming transistor.