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Help with diy bench psu circuit.

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Would this be alright for just variable voltage?
It would obviously need larger heatsink and i would not use more then around 3A but does the circuit look good for just variable voltage?

If you want the cheapest possible this is probably it. Go ahead and build it. Once you have the chassis, meters, connectors and switches in place, it isn't hard to replace the PCB with something more complicated in the future. I would use a larger heat sink mounted to the chassis and possibly use a chassis mount rectifier. The hardest part is probably finding a heat sink that fits your needs. Plan the chassis so that you could add a fan if needed. Then you could easily change the PCB to something else in the future. But that's just my opinion.

The LM338 is likely a relatively expensive solution, but a simple circuit. Because of power limits the regulator likely has a fold back current limiting. So if little voltage is droped the current can be high (like 5 A), but if more voltage is droped the current limit would be lower (like 1.5 or 2 A). This helps to limit the worst case power loss and is still OK to power a circuit running at a relatively high voltage (e.g.   < 10 V drop).

There are a few threads about lab supply circuits - some of them are OK, e.g. one based around LM324 OPs.

Basically it looks ok, but I'd compare it with the reference designs in the datasheet:


You might want to add the protection diodes in Figure 18.

Check the ** note in Figure 23 for the value of R2 in the schematic (120R vs 220R).

The LM338 also has a min. load current (< 10mA). You might consider adding some sort of permanent load on the output to satisfy this.

In general the TI datasheet has got a lot of good bits of advice especially with regard to component selection and layout.

Ok,thanks. I will think about all the options and choose one.


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