SMPS module with two optocouplers? Why?

Thread Starter

bloguetronica

Joined Apr 27, 2007
1,359
Hi,

I've bought a Mean Well EPS-65-24 switched-mode power supply module a while ago. It has a single 24V output. What I find it strange is that it has two optocouplers (U2 and U3, please see the photos). Both of them are PC123 and have the same orientation. One is beneath the transformer and the other is between the heat sinks.

My question is, why are there two optocouplers for a single output module? I've observed that pin 3, on both, share a common track. But I have no clues to why.

Kind regards, Samuel Lourenço
 

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crutschow

Joined Mar 14, 2008
23,349
Without a schematic about all you can do is a WAG.
Is the output isolated from the input.
If so , one could be for voltage feedback and one for current feedback from output to the control circuitry.
 

Thread Starter

bloguetronica

Joined Apr 27, 2007
1,359
Without a schematic about all you can do is a WAG.
Is the output isolated from the input.
If so , one could be for voltage feedback and one for current feedback from output to the control circuitry.
Hi cruthchow. What do you mean by WAG? Yes the output is isolated from the input. By the way, on the bottom side, there is a single SO-8 packaged chip with the markings "1380B" and "PTGo" on it. I went to investigate and it seems to be a NCP1380 from On Semi. I've verified that its pin 4 is connected to the same track shared by the optocouplers, which must be ground.

You can draw the circuit of two optocouplers and the other parts just use the block to show them, there is a SMPS circuit with two optocouplers on the end of the article, but it is not the circuit of that product.
Thanks, ScottWang. I'll have to read the article. The optocouplers are being used differently, though. In that schematic, the emitters are not directly connected to ground, while in my module they are. I have to figure if they function the same way.

Kind regards, Samuel Lourenço
 
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