Hobbyist Power Supply

The XL4015 is a popular, inexpensive 5A DC-DC step-down (buck) converter module, typically operating at 180KHz, used to drop input voltages (4V to 38V) to a lower, adjustable output (1.25V to 35V). It is highly regarded for its Constant Current (CC) and Constant Voltage (CV) adjustment capabilities, making it ideal for LED driving and charging Lithium batteries.

Key Features and Specifications:

• Max Output Current: 5A (recommended to use a heat sink for currents over 2A or high power, up to 75W).
• Input Voltage: 4V to 38V DC.
• Output Voltage: 1.25V to 35V DC (adjustable).
• Efficiency: Up to 96%.
• Protection: Built-in thermal shutdown, current limit, and short-circuit protection.
• Usage: Often includes potentiometers to adjust voltage and current independently.

Common Applications:

• Battery Chargers: Acting as a CC/CV charger for lithium-ion batteries.
• Lab Power Supplies: Used to create DIY variable bench power supplies.
• LED Drivers: Powering high-power LEDs with current regulation.
• Voltage Conversion: Stepping down higher voltages 12V/24V for lower-voltage electronics.

Best Practices:While rated for 5A, it is generally recommended to keep continuous current around 3-4A, especially if not using additional cooling, as the board can get hot at higher loads

Parts Required

All parts were sourced from Ali-Express.

3D printing

All 3D printed parts are printed with a 0.2mm layer height. When printing "PS10_Text.stl", switch to a contrasting color at the start of layer 4. Supports are required for "PS10_Front.stl". You will need to rotate some of the parts to lie flat on the build plate.

Assembly

Start by adding Insert nuts in the base. You need the following sizes:

• 3.2mm Diameter, 3mm High, M2 brass insert (4 off)
• 3.5mm Diameter, 3mm High, M2.5 brass insert (4 off)
• 4 x M2 4mm screws
• 4x M2.5 4mm screws

Next modify the XL4015 module by removing the two 10k vertical trimpots and replacing them with 3-pin headers.

Remove the blue input terminal block from the XL4015 module and solder wires that run to the 24V power supply module and to power the Meter module (Thin red & black wires - leave the yellow wire unconnected for now).

Add the blue barrier terminal block you removed from the XL4015 and solder it on the AC input of the 24V power supply.

Wire the AC power socket and power switch to the 24V power supply. I used 4.8mm spade female connectors on the AC power socket and power switch as these can be damaged if too much heat is supplied.

When using barrier terminal connectors with high voltages or high currents, I strongly recommend using Ferrules when screwing in the cables. (See TO FERRULE OR NOT TO FERRULE).

Wire the front panel as follows:

• Thick black wire from Meter module to XL4015 Negative Terminal
• Thick red wire from Meter module to Negative Output Terminal Post
• Thin Yellow wire from Meter module to XL4015 Positive Terminal
• One side of Front panel rocker switch to XL4015 Positive Terminal
• Other side of Front panel rocker switch to Positive Output Terminal Post

Wire the current and voltage multi-turn potentiometers to 3 pin Du-pont female connectors and plug onto the headers you added previously.

Finally close the case using 4 off M3 6mm screws.

Conclusion

The XL4015 is a cheap solution to build a simple power supply. Total cost was around $20 to $30. Using the 24V power supply, the maximum voltage that can be outputted is around 22V, more than adequate for most home hobbyists.