VVD

[richcj10]

I am working on a variable voltage drive for pumps and fans/ It takes about 28 - 21v on the input and can on demand take the output from 8-24v @ 8-10A on the output. The 24v output will of coarse not be meet when the input ( battery) is dead.  I made something before but it was at 3A. Any IC ideas would be great. I need something that is low part count.

Thanks

[ajb]

So you supply varies from 21-28V, and you need an adjustable output from 8-24V, but the output voltage never needs to exceed the input voltage--did I understand that correctly?

If it's to drive a motor of some sort and you don't need to boost the voltage, can you just use PWM?  That's a heck of a lot easier than trying to provide a regulated voltage at 8-10A.

If you need a regulated voltage, I think the only low part count solution would be an off the shelf DC-DC module, but I don't expect that modules with such a wide adjustment range at that power level are common (or cheap).

[qwaarjet]

I've used the ltc3789 in a similar operating range to what you are describing. Though I was using as part of a solar panel mppt/ li ion charger so it wasn't as striped down as it could be.
http://www.linear.com/product/LTC3789

[richcj10]

So you supply varies from 21-28V, and you need an adjustable output from 8-24V, but the output voltage never needs to exceed the input voltage--did I understand that correctly?

If it's to drive a motor of some sort and you don't need to boost the voltage, can you just use PWM?  That's a heck of a lot easier than trying to provide a regulated voltage at 8-10A.

If you need a regulated voltage, I think the only low part count solution would be an off the shelf DC-DC module, but I don't expect that modules with such a wide adjustment range at that power level are common (or cheap).

The reason it needs to be "regulated" (we could have ripple on the line) is that we are controlling the voltage to water pumps that are brushless.  The control circuitry is built into the pump. If we control it with PWM, it my not regulate so well making the pressure in the cooling line not constant. This will cause our readings to be off (known and measured) and heat transfer not constant to a given voltage.  The pump is not as much of a problem as the fans. The fans run on 12v and have an average current of 2.8A. I want to have head room on top of that. Also we may be controlling more than on fan on each output.