variable switch mode PSU

[Nekojita]

Hi,

For some class D experimentation that I am doing I need a switch mode PSU with the following basic specifications:

Adjustable 0-60V
Max current 3A @ 60V
Input 24V DC ( I have a 24V 10A offline PSU)

Adjustments means in order of preference:
1) Digital
2) Voltage
3) Potentiometer

I've looked everywhere online and cannot find something that I can easily modify for this including the DIY sites, Linear Technology website (LTSpice models), Ebay, Amazon (converter modules), etc.

If anyone has something that they could throw my way that could meet or be modified to meet my needs, it would be hugely appreciated.

Thanks,

Neko

 

[gmarsh]

Xantrex made a 60V/5A switching lab supply that I've seen in several different labs, and they can't be the only company making the things. Keep an eye on eBay, craigslist, etc.

But if you insist on building it yourself...

If you can get a higher voltage offline PSU that does 72V or 96V, your hunt will probably get a bit easier as you can use a buck instead of a buck-boost converter. Buying two 36/48V supplies, ungrounding the output of one of them and putting them in series will get you there, if a higher voltage supply is hard to come by.

Once you get that, if precise regulation of the output isn't that important, it'll probably be easier to build an open-loop buck converter using a 555 timer/pot/comparator to create an adjustable duty cycle PWM, and feeding it into a half bridge driver feeding a couple of fets.

To do precise regulation of the output, there's plenty of buck controllers out there that'll do the job -though you probably won't be able to adjust the output down to zero, and it might be hard to compensate the supply over the whole load/voltage range.

 

[Nekojita]

gmarsh,

Thanks for your reply and comments. I have looked at the lab supplies and really wonder how they are able to make these switching with such a wide voltage and load range. I'd love to a a copy of the Xantrex unit's schematic that you mentioned.

I am thinking that likely I'll need to use both a boost and buck converter and figure out an intelligent scheme to adjust both simultaneously.

Neko