DIY 3W constant current LED driver


Dilshan Jayakody wrote a post on his blog about his 3W constant current LED driver:

This is quick post about 3W constant current LED driver which I was design to combine with some homemade furniture piece. The main components of this system is LM311 voltage comparator and IRF9640 P-Channel MOSFET.
This module is design to drive maximum of two 3W high power LEDs and it requires 8V – 10V DC (500mA) power source. In this given configuration this module may not need any heat-sink (for IRF9640) and consume maximum of 500mA of power.

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  1. Unfortunately it’s a linear driver, looking at the schematics. If there is no dimming control, the whole thing can be replaced by a few resistors with a bit of testing, while making sure the heat loads are reasonable. LEDs will run fine at a variety of current loads. Since the circuit runs the LEDs at lower than rated current (which is reasonable, and still plenty bright) they will be about 7V and 500mA (in series), and say with Vin=9V, resistors will have only 1W to dissipate. Here I would go with resistors for short-term display, or a switching circuit for a long-lifed project.

    1. yep it is as if he started making a hysteretic buck controller, but then left out the induction and diode.
      The way it is drawn the comparator is basically used as a bad opamp

      1. I wonder if the thing oscillates or just hangs around the linear region… If there is about 2V headroom, we can also stick an LM317T there as a current regulator, that will need only a few components and the current is well under the limit for the TO-220 part.

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