How to dim an LED with constant current supply?

I have a power RGB led with 350 mA max per color. If I get 3x 300-350 mA constant power supplies will I be able to dim each individual color from 0 to 100% power with Arduino (with NPN transistors)?

I am a bit confused since constant current psu's are the best way to power led's but since they provide constant current can they be dimmed with pwm as one would expect with any power supply?

I am thinking of this PSU.


Yes, you can use PWM to dim LEDs with constant current power supply.

Personally I would go with MOSFETs instead of NPN transistors. If nothing else MOSFET will dissipate less heat.

I have used this constant current LED driver with success in the past. May be worth checking out. It can be controlled with an analog voltage or a PWM signal.

As others have said, yes, it will work with PWM to control brightness. The name "constant current" is kind of misleading, I prefer "current limited". You can let the LED pull on the supply as hard as it wants, but it will only ever get 300 mA. If you shut off the LED the supply won't push harder than its rated voltage to force 300 mA through it. With the supply you linked that is 13 V, so it would just output 13 V and no current.

Category: led Time: 2012-12-04 Views: 0

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