# Board mount AC/DC converter design concerns

I'm going to use board mount power supply (IRM-30-12) for first time. It has class 2 protections as per datasheet. Does it really protect my digital circuit in case of Hazardous situations like lightening and others?

Should I place any switching regulator/ battery charging components on its either side of PCB?

Does it really protect my digital circuit in case of Hazardous situations like lightening and others?

The data sheet says this about surges: -

EN55024, heavy industry level (surge L-N : 1KV), criteria A


And all that means is that the unit will survive a 1 kV surge when applied to the AC lines. It doesn't mean that a surge will not produce a knock-on transient of some form on the DC output so you need to take care of down-stream effects yourself. These days, surviving a 1 kV surge is old-hat and rather feeble so, you have to put things into context. If you can, try and find a device with better survival qualities - for instance, ethernet devices tend to be able to survive 6 kV.

However, the data sheet also says this: -

Protection type : Shut off o/p voltage, clamping by zener diode


And that likely means that the output DC voltage is fairly hard-limited to some upper value but there's no guarantee that your electronics can survive that upper value. For a 5 volt output power supply, the upper value is stated as being 6.75 volts - so, is your electronics capable of surviving that extreme?

You also need to consider that surges can produce a common-mode transient on the DC output and this may also cause your load a problem especially if your load is not galvanically isolated from earth.

Summary: It depends on your circuit!

• As I use 12v out the upper value is stated 16.2v in the datasheet. I have limited the voltage using overvoltage protector TISP4015L1BJR-S and SMBJ15A(TVS) in the DC input line, however the maximum input my regulator can accept is up to 40v(LM2596s). Will it get the transient issue to my load ? @Andy aka – PCBLearner182 Jun 25 at 6:37
• @PCBLearner182 there are some questions that cannot be 100% answered but, if your regulator is good for 40 volts then you should have confidence in surviving non-common-mode transients from the device. Common-mode is difficult to judge because there are so many factors to consider and it's probably wise to do a test. – Andy aka Jun 25 at 7:42
• Thank you. I'll do it. There is one more doubt I have regarding pcb design. Should I pour or remove copper on both top and bottom part where I placed the mounted converter (IRM-30-12). Should I place battery charging components on either layer of the converter? @Andy aka – PCBLearner182 Jun 25 at 7:51
• What does the data sheet tell you and also remember that you need clearance between live AC inputs and DC outputs for safety reasons. Never skimp on this requirement. I can't answer for you battery charging components because there are no generalizations I could make. The devil is always in the detail. – Andy aka Jun 25 at 7:55