switching power supply with lnk304

[electronicsIUST]

Hi, I use below circuit to build 12Volt 100-200mA from 220V AC with lnk304. But the problem that I have encountered is that some of these circuits explode after a while. But some of them are still working for 3-4 months. What can be the reason for this problem?!

 

[betwixt]

Could be for many reasons but first tell us what you have connected to the 12V outut please.

Brian.

 

[electronicsIUST]

Could be for many reasons but first tell us what you have connected to the 12V outut please.

Brian.

It is connected to two relays and also to input of a LM1117 in order to create 3.3 Volt.

 

[betwixt]

...and what part explodes?

You have no over voltage protection or EMC filtering on the AC input so it might be prone to to interference spikes. The other danger is that something connected to the output can sink current to ground because there is no voltaic isolation.

Brian.

 

[electronicsIUST]

...and what part explodes?

You have no over voltage protection or EMC filtering on the AC input so it might be prone to to interference spikes. The other danger is that something connected to the output can sink current to ground because there is no voltaic isolation.

Brian.

Thanks for your reply,
Usually the input of circuit and before lnk304 and also NTC explode. Also it seems that Phase and Null become short circuit because arc occurs and main fuse of home activates.
What can resolve this problem?!

 

[KlausST]

Hi,

please post the PCB layout of your circuit... so we are able to verify this against the datasheet.
Also post the manufacturer and exact names of the used parts.

Klaus

 

[treez]

also, you shoudl be careful you have used fast enough diodes. What diodes have you used.
Also, you have half wave rectifiaction.....so your lnk304 could be switching on/off/on...which mightbnt do it any good