Make a smallest AC>DC power supply

Thread Starter


Joined Dec 17, 2015
I'm afraid you don't get that kind of current output in the size you are looking for. Just because you imagine it can be done doesn't mean it is possible or feasible.
I built one on the back of a nickel one afternoon. I thought people would prefer a big-ass block instead so I just threw my project in the dust bin.


Joined Feb 24, 2006
On the subject of money is no object to fit it all into an IC, the IC is not really the problem. The problem is dealing with that amount of power in an efficient way. Even a small amount of resistance in the high current path can produce a substantial amount of heat. The most efficient design will involve a buck regulator and a good sized transformer. With an output power of 360 watts and a minimum efficiency of 85%, we have about 425 watts of input power to deal with. Just for the record, what are the dimensions of those modules and how small does the one you want need to be?

Roderick Young

Joined Feb 22, 2015
I make the size of that supply to be about 8" x 4" x 2". The supplies in one of the high-end HP servers (no longer made) were those dimensions, except half that height, so half the volume. The supplies were rated at 1200 watts (and that's a real continuous 1200 watts, not something a low quality vendor just made up). It was 96% efficient, so had to dissipate about 50 watts of heat. It was quite heavy too, the inside having just about every free space filled with solid metal to conduct heat to the outside of the chassis. In a server, there is the luxury of having controlled airflow, so banks of fans forcing air past the supply. I guess what I'm saying is that if you can cool your supply, it's possible to achieve that size. It will be expensive. Add two more zeros to the prices in those Alibaba listings.

If you cannot fit the supply in your device, have you considered having an external brick?

Sorry to post and run, but I'm going to be busy for about the next week, most likely not visiting AAC. Good luck, though.

Thread Starter


Joined Dec 17, 2015
Thank you for you guys help. The reason I want it to be small is i need it portable. I have a guy who has been making transformer for medical device but he told me it is not possible to make it smaller so I come here to ask and confirm this.


Joined Aug 1, 2013
400 W and portable are not usually combined in a project unless portable means rolling around on wheels. If it is AC powered with a line cord, how portable does it have to be?

Also, how about some specifics? max height, width, depth dimensions, max. volume in cubic inches, max temperature rise under full load, is fan cooling allowed - anything? Also, is this for a patient-contact application, or does the supply need medical certification, or power factor correction, or, or, or?

This is not a complete power supply, but it can form the core of one:

Also, Vicor has a line of components with even greater power density (and even more...personality).