Here is a simple, easy-to-build constant voltage buck converter based on the XL4016 buck IC. It uses minimal components and features a wide input/output voltage range. What's more, it can output up to 8amps of current! A 25turn trimmer mounted on the PCB allows the user to set the output voltage as desired. Included in this post is a set of PCB Gerber files you can download & use to order a set of PCB's from online PCB manufacturers such as JLCPCB.com
Please make sure to read all information under the "Notes:" header, before you attempt to build this buck converter 🙂
Specifications:
Minimum input voltage: 8v
Maximum input voltage: 40v
Minimum output voltage: 1.25v
Maximum output voltage: 36v
Maximum output current: 8A
Output voltage ripple, 32v input, 12v output with 8A load: <100mvpp
XL4016 features:
High efficiency up to 96%
Built-in thermal shutdown function
Built-in current limit function
Built-in output short protection function
Built-in input over-voltage protection
PCB Gerber files download:
https://drive.google.com/open?id=1eVJ_HyIm6lQEcE5Cmfargr02WNg8vWhP
PCB measures: 66x59mm
Mounting hole pitch: 58x52mm
Schematic:
Bill of materials:
1x Schematix XL Buckconverter v1.4 PCB
2x 2way screw terminal: P5.08mm (J1, J2)
3x 470uF 50v capacitor: D12.5mm P5.00mm (C1, C7, C8) (See notes)
6x 1uF Ceramic Disk capacitor: P5.08mm (C2, C3, C4, C5, C6, C9)
1x XL4016E1 buck IC: TO220-5L (U1)
1x MBR1545CT Dual Schottky diode: TO220 (D1)
1x 47uH 10~12A Inductor: L31.8mm W15.9mm P13.50mm (See notes)
2x 1/2w 360R resistor: L6.2mm D2.5mm (R1, R2)
1x 10k ohm 25 turn trimmer (model: 3296W) (RV1)
2x Extruded heatsink, TO220 compatible, P25.4 mm W35mm D12.7mm (See notes)
Notes:
Electrolytic capacitors C1, C7, C8 should have low ESR & ESL values & be suitable for use in switch-mode power supplies (for example the Nichicon UPW1H471MHD1TO)
Inductor L1 is a toroid style inductor who’s core material should be ‘powdered iron’ for optimal performance. I recommend the “Bel HCTI-47-10.7” inductor for this application
Heatsink: The recommended heatsinks to use is CUI HSE-BX-035H-01.
2 Heatsinks are required. One for the XL buck IC & another for the MBR Schottky diode.
Cooling: Consider adequate ventilation and/or a fan to keep the heatsinks at a reasonable temperature.
In free air with room temperature at 22c, at a full 8amp load the buck IC temp was measured at 116c. While at 4amp load the buck IC temp dropped to 70c. By the use of a fan blowing air over the heatsinks, these temps quickly drop. Personally I'd try to keep temps around 80c or lower.
High current PCB traces. On the underside of the PCB there are exposed traces that carry the high current between the input & output. On their own, these traces would overheat & potentially burn out. To avoid this the high-current traces are exposed (aka no solder mask) allowing the user to tin the traces with solder and thus allowing the traces to easily handle the maximum current the Xl4016 can output.
