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DC-DC Converter

DC-DC Converter

(OP)
Hi, I have recently built a dc-dc converter to convert supply voltage from 6V to 32V, the circuit diagram is as below:



and the circuit on the breadboard is looks like this:



My friend has built one with the same circuit diagram, I have double checked with him, both circuit connects exactly the same with same components, he circuit is working perfectly fine, but my circuit has a problem. my output voltage jump to the 42V, slowly drops to 32V, jump up again to 42V, slowly drops and it repeats this process over and over again. I have no idea what is wrong with it.

Here is how my friend circuit looks like:



Any help will be appreciate!

Thank you!

RE: DC-DC Converter

Copy his layout? Yours looks neater, but your layout has different stray capacitances to his layout. Sometimes that's all it takes to upset a switchmode PS circuit.

RE: DC-DC Converter

Some need a load or they become unstable. Add a resistor load about the size you need for your application.

Keith Cress
kcress - http://www.flaminsystems.com

RE: DC-DC Converter

Itsmoked has the answer. With no load, the circuit operates to charge your capacitors, overshoots the set voltage, shuts down, and turns-on again when the capacitors finally discharge below the set voltage, then repeats. You need a minimum load.

RE: DC-DC Converter

(OP)
it is the problem with breadboard. problem solved. thank you

RE: DC-DC Converter

Thanks for the follow up.

The breadboard.. You mean a bad connection? Or not understanding the actual routing of that particular breadboard? (some can be pretty odd)

Keith Cress
kcress - http://www.flaminsystems.com

RE: DC-DC Converter

Breadboards can be pretty crappy as far as connections. The 33063 is a pretty old design and tends to be slow. You wouldn't stand a chance doing a breadboard like this with newer switch converters. The inductance and induced pickup would drive the chip crazy. Even some circuit board designs fail when they don't take those factors into account.

RE: DC-DC Converter

(OP)
It is bad connection problem. The breadboard is faulty...

RE: DC-DC Converter

Another thing about those breadboards.
You do not have any control of capacities! There can easily be 1 nF between two neighboring rows, and that can couple things where they are not supposed to go!

RE: DC-DC Converter

Yes it should be the problem,as you described both of your projects are the same,then it must should be the same results otherwise your breadboard miss something.

Happy for you

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