Is LNK304-Based 220Vac to 5Vdc Transformerless Power Supply Safe for Embedded Use?

Hi,

I am working on a project where I need to design a 220Vac to 5Vdc Power Supply without using the transformer. We need to use to to power up an embedded project.

I am an embedded designed so don't know much about power electronics. If anyone could provide me the exact circuit and components. If you could provide the PCB design that would be great.

I have seen one resource here: https://www.pcbway.com/blog/technology/220Vac...rless_Power_Supply_Using_LNK304_5b2e2d7d.html Can someone please confirm that this circuit will work. As it seems quite small and will work better for us.

Thanks.

Is this a commercial project, or for in house use only. If it is a commercial project, then I would buy something off the shelf, since they will (or should) have certification for electrical safety and EMI (VDE, URL etc, watch out though, sometimes the labels are fake)). I would still recommend it for an inhouse one off as well, for the same reason.
Why do you wish to avoid a transformer, is it just because you want to design your own power supply and don't have the requisite knowledge. They offer the advantage of isolation from the mains voltages present on the input if components break down. There are very compact flyback based switchers that use very small transformers (they operate at frequencies much higher than 50-60Hz of mains transformers so the core size is dramatically reduced) that have the required isolation. Solutions may be found as in line bricks or open frame for inclusion within a system. They are available from a few hundred mA up to tens of amps (you don't mention the current you need), and you probably couldn't design and build one for the price the commercially available ones sell for, since they are a commodity item. An additional advantage of buying is that you don't have to mess about with lethal mains voltages, PCB creepage and clearance issues, etc.
Cheers,
Richard

Andrea DO NOT under any circumstances use a design like this. The points labelled GND on the diagram will be at mains voltages and could kill you! This is what they mean by "non-galvanically isolated". If you connect the GND points to the mains ground it will just blow the bridge rectifier BR1. Also, this design can only supply about 150mA and you would probably need more than that. The ONLY time you would use a design like this is for powering something that had no connections at all to the outside world (a WiFi repeater for example).
A switching power supply with a transformer will have only a small transformer - 1 cubic inch or less - and will have an isolated output which is quite safe for development work. I have seen designs like that which are smaller than the one you linked to.
So please get a commercial power supply solution for your development work and leave the power supply design to the experts. I know a little bit about it and would hesitate to design something like this myself.
Good luck with your projects!

Hi,

Contact its author. There is a YouTube video in your link.

Hi.
There are many solutions. Give a lokk here:

https://www.eeweb.com/transformerless-power-supply/

https://www.eeweb.com/220vac-to-5vdc-transformerless-power-supply-using-lnk304/

https://www.eeweb.com/transformerless-5-volt-power-supply/

https://www.eeweb.com/low-voltage-power-supply-without-transformer/

Best regards.

Giovanni

First off: 220VAC can kill. I would suggest that you get someone with experience to guide you.
Also if you are going to make this into a product you will need regulatory approval to meet safety and EMI emissions requirements.

Now onto your resource. Make sure you read and understand the first paragraph which also reminds you that 220VAC CAN KILL.
And on to of that, the circuit is non-isolated. That means your design must be such that no outside fingers can touch any part of the electrical circuit. To say nothing of you actually designing and debugging it.

An isolated power supply would be preferable and a USB power supply design may be a simple way to go. There is a tear down of one here (https://www.youtube.com/watch?v=JuWT22Ck6Aw) which gives a fairly good idea in the issues of designing your own, but unfortunately doesn’t give you a complete parts list. And you would still have to jump through all the regulatory hoops.

In my (not so) humble opinion, you should use an existing USB wall-wart with a USB connector on your board. Or you could modify the USB cable and wire the 5V directly. No hassles with the officialdom, nor the expense of testing (and inevitably revising) the circuit.

You haven’t mentioned your current requirements. I have assumed a modest requirement, less than 0.5A say, although if to go with USB-C you can get to 0.9A.

And again, 220VAC CAN KILL.