On Wed, 30 Jun 1999 00:22:47 -0300 Mauricio Jancic writes: > Does anyones have a good idea on how to make a digital >controled power = >supply (a good one), I've already see the example on National's LM317 >= >datasheet, but I'm looking for something better. > Thanks all for your answers. > > Mauricio Jancic > VARIMAK S.A. What, exactly, do you have in mind? It seems the simplest method is to get some power supply chip (whether a linear or a switcher) and drive it with a D/A driven by a PIC. You could also possibly use the PWM output of a PIC to directly drive a FET (or a FET driver driving a FET) in a standard switcher circuit (whether buck, boost, flyback, or whatever). You can then use a PIC analog input to sample the output voltage and set up a feedback loop. You can get real fancy in the control algorithm, going to PID, etc., or just stay with a proportional loop. I recently did a PIC based boost converter to work as a power tracker for solar panels in a solar powered car. It varied the inductor "charge time" to result in maximum charge current into the batteries. We ended up with an interesting sort of converter. Again, we varied the charge time. We added a small secondary to the inductor that output +5V typical during the inductor "discharge". This drove another PIC pin (through a current limit resistor). As soon as the inductor was done discharging, we turned the FET on and started recharging it. This eliminated any time when there was NO inductor current (as would be the case with a standard duty cycle based PWM) and minimized inductor ringing at the end of inductor discharge. The PIC also did polled EIA-485 telemetry reporting solar panel voltage, current, battery voltage, current, and FET pulse duration to a central computer. I didn't get to see the whole thing work before they students building the car took off for a race with it. I haven't heard how it went yet. We should be doing more work on the converters this summer, when they get back. Harold Harold Hallikainen harold@hallikainen.com Hallikainen & Friends, Inc. See the FCC Rules at http://hallikainen.com/FccRules and comments filed in LPFM proceeding at http://hallikainen.com/lpfm ___________________________________________________________________ Get the Internet just the way you want it. Free software, free e-mail, and free Internet access for a month! Try Juno Web: http://dl.www.juno.com/dynoget/tagj.