# AC-DC 5V 700mA 3.5W Power Supply Buck Converter Step Down Module [closed]

I am trying to implement 220V AC-DC 5V converter on my custom PCB. Anyone can refer me to the circuit schematic that is being used in the referred link below. I am expecting the converter to have main four cascaded stages (1) Transformer (2) Rectification (3) Smoothing (4) Regulation As shown in figure 4 in the following link: 230V AC to 5V DC converter, lossless However, the design in the link above doesn't have big capacitors (1mF,..) and doesn't have nine resistors and seven capacitors as the industrial design shown on ebay implements.

Thanks!

## closed as off-topic by Autistic, Voltage Spike, Dmitry Grigoryev, Daniel Grillo, ThreePhaseEelJan 13 '17 at 1:08

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• just buy one an copy it. – Jasen Jan 12 '17 at 5:41
• looks essentially the same as 75-95% efficiency except with more powerful parts. – Jasen Jan 12 '17 at 5:58
• If you need to ask basic questions like this and expect to copy a Chinese-knock-off, you are on deep water and possibly about to electroute and/or burn to death yourself and/or your customer. Buy an approved off-the-shelf separete power supply and implement that into your design instead. – winny Jan 12 '17 at 9:00
• @winny thats rude! – ousama kanawati Jan 12 '17 at 17:37
• Not compared to electrocuteing your customers. – winny Jan 12 '17 at 19:41

I am trying to implement 220V AC-DC 5V converter on my custom PCB

I think that you should not do this unless you do not care about your safety, other user's safety and fire hazard.

The fact that you link to this module:

tells me enough.

I am not a mains supply designer but I can tell a lot already from looking at the pictures of that product. This is a very cheap solution and I would not use it in any device with my name on it. It seems to have mains isolation but only the bare minimum. There's a green capacitor next to the transformer which does not look like the proper Y-rated capacitor which is needed here. That makes this module unsafe.

What you want to do is either power the device from a proper power adapter, like the one used for charging a phone. Make a power jack or USB connector on your PCB so that there's no need for 240 V AC on your PCB.

Or if that is not acceptable then buy a proper power adapter module.

Something like these. Note how those modules are much more complex and show a clear isolation gap between mains side and output.

• Actual mains supply designer here. You can get away with a product like that with great caution, tripple insulated wire in the transformer, lots of tape, cutouts in the PCB and big concerns for creepage, but just like you say, your average eBay power supply does not. Mr. Kanawati is out on very deep water and thin ice at the same time. – winny Jan 12 '17 at 8:57