Question about clamping diode...

[lloop9]

Hiya fellows, I was thinking of buying this ebay regulated PSU.

I read that it would be prudent to use clamping diodes on the output to prevent damage from reverse polarity spike. I need advice if installing the diodes before the 0.1uF bypass caps is correct? Can I use the 1N4004?





linky: +/- 1.5 to 32V DC Adjustable Voltage Regulator Module. Based on LM317/LM337 | eBay

cheers

[KatieandDad]

D5, 6, 7 and 8 already provide protection against reverse polarity at the output.

You dont need the extra diodes.

[DF96]

D5 and D6 prevent back-current through the regulator. They do not stop reverse voltage spikes. D7 (D8) might help if C5 (C6) is big enough.

[lloop9]

Hi, C5(C6) is 10uF. I believe clamping diodes across C7(C8) will help prevent reverse V spike but I could be wrong...

cheers

[DF96]

It all depends on what is producing the reverse spikes and how big they will be.

[nattawa]

The clamping diodes are there to discharge C5 and C6 at power turn off. Without them the adjustment terminal of the regulator may stay at a higher potential than that of the input and output terminals for a while, and the charge in C5 and C6 may or may not damage the IC.

[jitter]

Originally Posted by lloop9

Hiya fellows, I was thinking of buying this ebay regulated PSU.

I read that it would be prudent to use clamping diodes on the output to prevent damage from reverse polarity spike. I need advice if installing the diodes before the 0.1uF bypass caps is correct? Can I use the 1N4004?

My personal opinion is that the psu "as is" is fine. Only if I were expecting reverse polarity spikes would I consider using the extra diodes on the output, not 1N4004 but a type specifically meant for transient suppression, like 1.5KE.