Poorman’s Buck Schematic and BOM
Here are the schematic and the BOM (Bill Of Material) for the Poorman’s Buck LED driver.
Poormans_Buck_schematic-rev2a (PDF)
BOM
- 1 or 2x 1 ohm 1W – R10, R11 (use only one to get 350mA, or 500mA (with R2=2.7k) output current)
- 1x 10 ohm – R8
- 2x 1k ohm – R3, R9
- 3x 4.7k ohm – R1, R4, R7
- 3x 10k ohm – R2, R5, R6 (change R2 to 2.7k ohm to get 1A output current)
- 1x 10k ohm Potentiometer – VR1
- 1x 22pF – C5 (optional)
- 2x 0.1uF – C2, C3 (optional)
- 1x 2.2uF – C1
- 1x 100uF / 35V – C4
- 1x 47-100uH / 1.2A – L1
- 1x GPN (5551, 2222, 3904, etc.) – Q1
- 1x GPP (5401, 2907, 3906, etc.) – Q2
- 1x P-ch MOSFET (NTD2955 or IRFU9024) – Q3
- 2x 1N4148 – D1, D2
- 1x SB140 – D3
- 1x LM393 – IC1
For more information including assembly instructions, please view my instructables.
Follow
I have one doubt in this schematic. It has one diode D1. Why it is there won’t it will get short and all the current will drain through it.
October 25, 2012 at 2:58 am
Standard silicon diode has a forward voltage drop of about 0.6V. The current through D1 is limited by R1, to about 5mA.
D1 is used to create a reference voltage to compare the output current against.
October 25, 2012 at 10:25 am
This is a great LED driver!
June 19, 2012 at 12:39 pm