CrisisTech Blog

This psu is special recommended for radio amateur use, it’s a simple powerful solid state power supply for linear modules up to 30V/20A DC stabilized with voltage adjustment from 20V to 30V dc.
The basic part is the popular LM317 which has the role to adjust the output voltage, it’s really the perfect component to supply RF linear units where high frequency & RFI is present, the LM317 can give a 1.5 Amp max output so the current amplification stage is necessary, it seems like a monster & it uses 5 x transistors 100V/25A 40A peak current with Ib 5 max Amps , each of them is responsible to supply 5 Amps output current with total current (5 x 5A) = 25 Amps but who wants to push to the limits?
The circuit use 50000Uf input filter & is the best choice for a low ripple output, the pcb is FR4 epoxy with dimensions 16cm x 10cm & a metal aluminum rail installed with 7 screws directly on the pcb, the semiconductors were installed at the bottom side of the pcb to keep them pressed for sure on the heat sink in order to avoid the screwing process for each semiconductor, a square piece of pcb was removed for the bridge to be placed, all the above can give better stability & thermal induction.
This design is flexible & allows you to use less than 5 transistors in case you want to use it for smaller voltage or current output needs from 1.5 to 20Amps.
There are forwarding protection diodes & an output fuse 20 Amps holder for minimum protection, so please don’t forget to include them.
To decrease possible RFI problems small value ceramic capacitors were placed to the output area & I suggest you include the necessary well-calculated RFC choke to the linear input or directly on the psu output (+).
Warning: This psu was designed for indoor & solid state use there is no short circuit protection so it’s not recommend to use it like a variable voltage lab power supply.
It’s an old reliable design with a perfect MTBF, I made a lot of them 20 years ago & they are still working without problems.
Specifications.
Input: 30VAC/25A max (See text)
Output: 20-30VDC 1.5A-20A (see text)
Power Cosumption: 600W max
Ripple: Dimensions: 16cm x 10cm (Included bridge)
This project is for sale, available for manufactures only.
I hope you enjoy the pleasure of construction.
Thank you.