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zener diode

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Hello, I need to charge a capacitor to its maximum allowed voltage which is 11V.
There is 11V zener diode to protect it. Can I use a AC 12V 2A supply? Will the voltage be clamped by the zener?
Thank you!

You can not charge capacitor from AC source, you need at least one series diode to rectify AC (half wave rectifier) or better - diode bridge (full wave rectifier). Also, to use zenner as a clamp, you need to limit current, because otherwise the zenner can get very hot and burn. To limit current you may add series resistor.

Draw a schematic of what you are planning to do. It will be much more clear.

Thanks for replying.
Sorry, is a DC 12V 2A supply, not AC.
Attached the schematic. Is it ok just like this? Thanks!

Zener diodes aren't very accurate. You're better off using a programmable shunt regualtor such as the LM431.

Actually, in this case a normal shunt regulator like lm317n might be better in terms of power efficiency as it won't dissipate heat when capacitor is not charging. Just I'd check there is not overshooting on the output. So, an lm317, and a trimpot will do the job. Add small input capacitor if you want to get fancy :). Although, that's approximately complexity of tl431...

Zenner will work too, but they are annoyingly drifty. As they heat-up the voltage will drift. Also, initial voltage is not accurate. It is like +-5%. It also changes with current.


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