I am working on my LED Driver Inrush test fixture and have things working pretty smooth. I used an H11AA1 optoisolator with a diode to switch on the positive cycle when a momentary pushbutton switch is depressed. The optoisolator when it turns on pulls the base of an NPN transistor low and allows a ramp generator to generate an 8mS ramp that is fed to a comparator that allows me to output a positive 5V pulse that is fed to a transistor latch circuit that turns on a random crossing SSR relay that enables my driver at the peak positive voltage. The only issue is that I can still trigger the latch circuit if the button is pressed during the rise time of the positive cycle, which delays the start of the ramp and fires the SSR late. I believe that if I add a flip flop or some kind of counter between the comparator and the latching transistors that puts out a positive 5V pulse after the second positive output from the comparator, it will be timed perfectly every time the switch is pressed. I was looking at using a D type flip flop with /Q tied to D and the comparator output tied to the clock input, but the output will go high on the first clock. I want a circuit that will count 2 and then go high on the rising edge of the second pulse. I am guessing I may need to reset the circuit when the momentary button is released. I should be able to figure this out, but just want to get ideas quickly to consider.
Any ideas???? Thank you in advance.
Any ideas???? Thank you in advance.