I am planning to make a simple DIY lab bench power supply using a old laptop power adapter with 18v 1.9A (35w) output. Adding a buckboost converter the current as well as the voltage can be adjusted using a potentiometer. This requires input voltage ranging from DC 5.5-30V; output voltage range is DC 0.5-30V, can be arbitrary adjustable; output current range is 0-3A, can be arbitrary adjustable with an inbuilt display and featuring constant current(CC) and constant voltage(CV).
The buck boost converter i can find is https://www.amazon.in/REES52-Converter-Buck-Boost-Adjustable-Regulator/dp/B07LCMHCV9/ref=sr_1_6?dchild=1&keywords=buckboost&qid=1612694167&sr=8-6
One could modify the feedback loop of the laptop PSU itself to get lower voltages. One could also get higher voltages however that would depend on the PIV rating of the output diode and the output filter capacitor voltage rating.
The buck boost converter shown here is rated for 5A input current max. Therefore at higher output voltages the max current is far lower than the advertised 3A. The heatsink fixing method is particularly bad and uses an adhesive backed rubber. These have extremely poor thermal conductivity. To do a proper heatsinking job you will have to screw mount the heatsink, requiring a weirdly shaped holder that attaches to the fixing holes.
On the plus side this is convenient as a quick fix low precision lab supply.
Thank you for your valuable feedback. I wont be able to touch the laptop psu as it is cased and has no kind of screws to open it and i just dont want to spoil opening it incorrectly. My currents requirements are mostly under 1A. Will this is board works for that, if not could you please tell me some alternative while also keeping the price under 1k
sorry for the late revert, i have recieved the buck boost converter and its working great, to my surprise i have recieved 4 boards on ordering and paying for 1. In this test i have attached an old laptop adapter with 18v/1.9a(35w) output. The max voltage this board can deliver is around 32v.
Then i gradually increase the voltage to 2v but due to current bieng limited at 120mA the supply only goes upto 1.2v, after which there is a constant current and the voltage only increases when i increase the current.
