I see a lot of requests for boost circuits with a little more current that the little multi vibrator ones. Also seems to be a need for a circuit without a boost ic - only easy to find parts.
Soo... I've been playing with this one. It uses a 555 running at about 75Khz. It is regulated (I use the term lightly) by changing the frequency of the 555. Good for about 100ma at 75% it can use a low cost radial lead inductor good for 900 ma. I thought I would post it to get comments as I have no plans to build it. So maybe we can shoot holes in it.
Brief description:
Power up reset C4, R4 and R3 hold off the timer to allow the output cap to charge before switching begins in case the inductor is saturated by power on.
Q2 limits current thru the switching transistor to a safe level giving kind of a soft start and short circuit protection. A 1 amp fuse would still be a good idea.
Q1 is the feedback to the control voltage of the 555 to achieve some level of regulation.
Seems like less than $5 in parts. I know a chip is better, the question is will it work? What would make it better?
Soo... I've been playing with this one. It uses a 555 running at about 75Khz. It is regulated (I use the term lightly) by changing the frequency of the 555. Good for about 100ma at 75% it can use a low cost radial lead inductor good for 900 ma. I thought I would post it to get comments as I have no plans to build it. So maybe we can shoot holes in it.
Brief description:
Power up reset C4, R4 and R3 hold off the timer to allow the output cap to charge before switching begins in case the inductor is saturated by power on.
Q2 limits current thru the switching transistor to a safe level giving kind of a soft start and short circuit protection. A 1 amp fuse would still be a good idea.
Q1 is the feedback to the control voltage of the 555 to achieve some level of regulation.
Seems like less than $5 in parts. I know a chip is better, the question is will it work? What would make it better?