Thursday, 19 February 2015

BenchTop Power Supply with XL4005

Almost finish't Power Supply
 (It burned up after i used it 3 times, So be carefull with this chip and don't push it to the limit)                            
On Ebay i found a neat little adjustable
power supply with LED display for about $7,-

I will try to change it into an Lab Benchtop Power supply.
Adjustable from 1..30V and 0..2.5A

At first i Googled the XL4005 chip to get some more information and not have to reinvent the wheel.
  1. On Youtube  i found a post from Julian Llett: Talk's about the short circuit isssue
  2. Datasheet
  3. Nuts and Volts Magazine: Learned about the regulators on the module. Also a circuit diagram.
  4. to keep the regulator cool
So don't short circuit this module at lowest voltage setpoint, the circuit with the opamp and the shunt resistor won't work. Current is limited by the XL4005 it self, that will be 5.5A !!.

Another issue are the voltage regulator's on the module. There's one on the regulator board, and one on the display pcb. They can't handle the 32V on the input !!. So as Nuts and Volts applied, I use an extra 7 volt power supply to feed those regulator's.

to Keep the XL4005 and the PCB cool i made a clamp with two pieces of Alu L profile and mounted the regulator board to the back of the alu case.
I mounted the display unit on the front panel together with the two multiturn potmeter's and the output terminal's

I made some extra winding's on the toroid transformer to create an extra output for the opamp and display regulator's.

On the left panel you can see the rectifier close to the Three 1000uF capacitors.
pcb mounted on the back
Inside the enclosure

I limited the output current to 2,5A
to prevent the supply to overheat. 

All part's are recycled so i payed
$7,- for this power Supply

L1 is a bit under dimensioned and
get's very hot. I will replace it by a bigger one.

Also the capacitor's on the regulator board get quite HOT, so
i might mount an little fan in the

Work in progress.

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