12V Power supply

12V high current linear power supply is very useful for HAM applications. I designed one based on s53mv schematic. The circuit is somehow odd because regulation transistors are in negative side of the current loop. Main reason for that is the collector or source of the transistors, which is connected to the housing of the transistor. To avoid isolation of the transistors from the heat sink it is better to have the housing, heatsink  and the transistors connected to negative rail of the power supply. It is similar to the car, where negative pole is connected to the chassis.

pcb pcb1

The schematics:                                                            and the PCB:

schpcbtop

Here is PDF of the schematic:  psu12v

The power supply is designed to fit inside standard metal housing. Custom designed housing is published on GrabCad (CLICK ON THE IMAGE):

ohisje

Power transistors are assembled in sandwich between PCB and heatsink. The pins must be bended toward the pcb, like this:

pritrditevTO220 sendvič

Some final testing:

test1

Top view inside the housing:

pogledzvrhaelko

The AC supply is provided with 17V/12A transformer. This is enough for 10-12A of permanent current draw:

trafo17v12a

Output voltage has fine adjustment with multiturn trimmer (R22 in schematic). The approximate range is from 10 to 14V.

 

Advantage of having negative pole on the housing is super simple assembly of the output connector:

rezkanje-ČP

The “PL” connector is feeding RG213 coax, which runs up the antenna tower for supplying the TNC, radio and other equipment like WiFi access point etc:

ant

 

The complete altium project is here: psu12v

Further improvement is crowbar protection based on LTC1696ES6. The PCB serves as Electrolytic capacitor holder at the same time:

crow-pcb crow-sch

The prototype with home made PCB is working – the schematic was tested!

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