I am working with LED drivers and compatible LED lights. They look somewhat like this:
These come in two versions: (1) Constant voltage type and (2) Constant current type
I am implementing a circuit which is able to dim the light. It involves a mosfet switch which sits between the driver and the LED.
For the driver which outputs constant voltage, the circuit works fine. I am able to vary the brightness of the LED by varying the duty cycle of my PWM signal.
However it doesn't work for the driver which outputs a constant current.
What would be the equivalent method for dimming the LEDs in case of a constant current source?
Best Answer
Mains-powered constant current drivers will only work as current source inside a certain voltage range (see the label) and they will have a capacitor on the output, so you can't use a shorting FET to apply PWM dimming. They're more like constant voltage supplies whose voltage is adjusted (not very fast) to keep the current constant, which only works if the load isn't changing too fast...
You need a dimmable driver, with a 0-10V dimming input, which you can use to control it. Or something DMX compatible if you have lots of lights and a DMX controller.