Independently variable on-time and off-time pulse generator circuit

Claim 1

A pulse generator for controlling the on-time and off-time of the power switches in an EDM power supply comprising; an on-time generator and an off-time generator, each of said generators including a timing circuit having adjusting means for continuously varying the period of said timing circuits, a Schmitt trigger level detector responsive to the signal produced by said timing circuit, a field effect source follower circuit interposed for isolation between said Schmitt trigger and said timing circuit, discharge means associated with said timing circuit, said discharge means operating in response to the output of said Schmitt trigger; a bistable flip-flop circuit having first and second inputs and a pair of outputs, said first input of said flip-flop being coupled to the output of the Schmitt trigger of said off-time generator and said second input being coupled to the output of the Schmitt trigger of said on-time generator, said flip-flop being driven into a first stable state in response to the termination of the period of the on-time generator and a second stable state in response to the termination of the period of the off-time generator, a first means for disabling said on-time generator, a second means for disabling said off-time generator, the outputs of said flip-flop being coupled to said disabling means so that said on-time generator is disabled when said flip-flop is in its first stable state and said off-time generator is disabled when said flip-flop is in its second stable state, whereby the signal produced at the outputs of the flip-flop is a serial pulse train whose on-time period and off-time period are independently adjustable.