Beginners question about variable output voltage switching topology

[Rendman]

Hello,

First a little background about me, I have ZERO formal education in any engineering specialty. Electronics has been an off and on again hobby for me. So that said, please excuse any question that seems completely ridiculous.

My question pertains to switching regulator topologies, specifically how one could build a laboratory grade variable output power supply built on a switching design. It seems to me that after a PFC block in the design I would have a fairly large output DC voltage that I could run through a buck converter. The problem that I see, is that it would not be possible to get the duty cycle down to the point where you could have a fractional voltage value (e.g. .5V, etc) with out the switch just shutting off and presenting 0V at the output. Is there a practical circuit that can regulate from 200V - 0V? Is there a specific topology that I have overlooked that would be best suited to this scenario?

Thanks,

Rendman

 

[milind.a.kulkarni]

with the best of my knowledge....generally laboratory grade power supply used switching and PWM based approach to get the corresponding voltages .....but in case of power supply the most important aspect is it's current driving capacity....you can get 0.5v also but provided that one need to design the current driving capacity of such source first....

Now related to 200 to 0 v regulation....can be obtained but you probability need a dimmerstat or auto transformer kind of device to control the input rating and ......the circuit for consequet voltage based sensing and selection of respective rectifer element selection or switching....

Good Luck

 

[Orson Cart]

A buck regulator can easily be made to control the output from 0.0V to max, in a smooth fashion, this is never done however for two reasons; 1, if the buck switch fails short full volts will be applied to the output (lots of smoke in the load) & 2, a straight buck converter provides no isolation - so if you touch the o/p you will get a mains shock. Regards, Orson Cart.