High Power LED driver circuit




   Led lighting application are requiring a constant current source. High power LEDs are usually operated at a 350mA current and higher, much as 1A. With the right heat sink and a constant current operation the service lifetime of the LEDs can be as long as 50000 hours - that means up to eleven years .

    Integrated with a 2A power switch, the BD9001F flexible step-down switching regulator from Rohm offer a simple and efficient solution for the supply of high power LEDs.


Power LED driver circuit

Power LED driver circuit

 

   Switching frequency is variable with the R3 resistor between 50 and 300 kHz. A higher frequency allows the use of small surface mount inductors and capacitors. For R3=270kOhm we have a switching frequency of  about 140kHz. The supply current for LEDs is set by the R4  with this formula:

Id=(1+R2/(R2+R5))/R4

   The values shown in schematic will give a current of about 0.64A for a input voltage of 9V. This circuit can be used to power multiple LEDs in series connection, 10pcs. or more but the L1 inductor must to be resized. The input voltage must be increased too. A software to selecting inductors it is available for free download at Würth electronik website.

Specifications:

 

BOM list:

 

Component placement on Power LED driver board

Component placement on Power LED driver board

C7 it is placed very close to the L1 inductor. The PCB can be make at low cost and quick using the toner transfer method. The results:

Led driver PCB

Led driver PCB

 The heat sink from a  CPU cooler is one the best alternative solution for dissipate the LEDs heat.

 

Led module with driver and heat sink

Led module with driver and heat sink

 

Orcad schematic and layout files are available for download.

Download circuit diagram in pdf format.


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