Sonsivri

Hi,

I am designing an automatic sort of Power Supply in which i need to control the Output DC voltage in range 0 to 12V in precise steps of 0.5V. I need to control the output voltage using computer commands (frond end software in .NET or C++ using serial/USB) Please suggest some design ideas?

I thought of using PWM duty cycle based DC level control, Is it possible to achieve that much accuracy using PWM method? If YES, suggest some switching devices for that...

Thanks...

maybe this topic can help you
www.sonsivri.to/forum/index.php?topic=37575.msg122223

Regards

We should know how much power you need at the output side, and how experienced you are in electronics, to give an optimal answer.
For smaller loads there are relatively easy schematics on the web (i. e.: http://www.drbob.net/project/powersupply/linear/12v1alvdfxd/default.html ), using op-amps with FET or transistor output. Because the output voltage depends on the reference voltage, changes in reference will result in changes at the output; if, for example, we replaced the reference diode with a shift register (or counter) - R2R ladder - op-amp block, the ref. voltage could be changed digitally. The drawback is that these are linear regulators, and may have high losses at high output currents.
PWM-controlled switchmode supplies are much better for high currents but those usually are more difficult to build, mainly when one must calculate and wind the coils by hand, and some devices need very careful filtering of the ripples of the generated voltage. Your application will determine the possibilities.

A linear regulator with a digital pot in the feedback strap would be fairly simple, although not as efficient as switching ofcourse. Add an FTDI USB->SPI bridge and you can control the pot from .NET->USB. Precision would depend on the tolerance and resolution of your digital pot.