AVR Controlled Linear 0-30V 0-5A PSU - Page 1
Forum section: electronics / projects

author: janengelbrecht
author_rank: Regular Contributor
timestamp: November 29, 2016, 08:41:24 pm
content: I Would like some comments on this design inspired by Daves PSU design.I had the idea to use Daves original current regulator design and then a 2N3055 serie regulator for voltage control.

author: janengelbrecht
author_rank: Regular Contributor
timestamp: November 29, 2016, 08:45:37 pm
content: And yes...the MCU board are on another PCB than the PSU board. The reason is that one PSU board will be equipped with two potentiometers instead and a switch: 3V3 or 5V supply.What i like to hear from you is something about stability, what software options one ought to implement and of course if you spot errors....please feel free to comment(And yes i know that serious people would use different transformator outputs according to the specified output voltage to avoid too big losses.But that will have to come later....i dont have access to trafos with different outputs (different voltage outputs).And yes the 4 Serie transistors will be mounted on enormous heatsinks with fans, and the heatsink equipped with a 10K NTC to make it possible to make shut down if the cooling fails.)And yes...R37 has wrong value...ought to be 220R

author: prasimix
author_rank: Unknown
timestamp: November 30, 2016, 07:11:58 am
content: Quote from: janengelbrecht on November 29, 2016, 08:45:37 pmIt's not so hard today to find transformer with two secondary that have the same voltage (e.g. 2 x 30V). With additional simple circuit to control relays or mosfet switches you can wire them in series or parallel to decrease power dissipation on pass transistors and to get higher current output on the lower voltages.

author: janengelbrecht
author_rank: Regular Contributor
timestamp: November 30, 2016, 10:49:49 am
content: Thx for inputs. I will look into it (Y)Sendt fra min EVA-L09 med Tapatalk

author: Brutte
author_rank: Frequent Contributor
timestamp: November 30, 2016, 11:40:37 am
content: Quote from: janengelbrecht on November 29, 2016, 08:41:24 pm1.What happens when for three 1.5A fuses fail and the last BJT gets 1.5A at max Uce? Not sure why you are using 4 fuses..2. How do you plan to build R7? That is 36W at 6A.3. I suggest that you use a Kelvin connection with R7.4. Why do you power AD822 with >30V? Do you think MC3302 would accept such signal (sense_C)?

author: Kleinstein
author_rank: Super Contributor
timestamp: November 30, 2016, 05:20:38 pm
content: The circuit does not include compensation (adjustment of loop gain for stability).Choosing the emitter follower output stage can be a little tricky for a 30 V supply, as is requires the OPs to do the full 0-30 V swing plus a little overhead. So more like an OP with a -5 and + 35 V supply. It is possible but not that easy. The way of combining voltage and current regulation is tricky, as the resistor of OP get quite hot and the the extra gain in current loop could make stability difficult. But it least is might help with limited slew rate.To really take advantage of the low output impedance of the emitter follower output stage one would need a push-pull stage similar to an class AB audio amplifier.Usually just one fuse - before the rectifier and one at the primary of the transformer.0.1 Ohms resistors are rather small for current sharing. Usually 0.22 to 0.33 are used for the 2N3055. For the beginning, I would start with lower current / power - high power would than be version 2.