Designing a power supply that drives an LED array supply

ledpower supply

I want to drive an LED array from mains power. The wall switch has a dimmer on it, I'd like the intensity of the LEDs to reflect the relative position of the dimmer, so as I dim the switch, the intensity of the LED array drops.

Because I already have an 8V 12W Halogen bulb system in place, I want to replace it with as few parts as possible to convert it to LED.

I'd like to do this as simple as possible. I know there are more sophisticated circuits that could utilize MCU or other clock driven PWM, but I am wondering if there is a more simple solution I am overlooking.

My current plan was to use a step down transformer / rectifier circuit. I would calculate the maximum DC voltage available when the dimmer was turned all the way off, apply the correct resistors to limit the maximum current in this "max voltage" scenario, and then use a simple constant voltage regulator circuit to control the intensity of the LEDs as I dimmed the circuit.

Would this work? Do I want to keep a constant voltage and have the current variable as I dim the switch? Is there a cheaper/better/easier way to do this than my current plan?

Best Answer

Wikipedia has some good examples about dimming. For as simple solution as possible (by electrical terms) I would use a transformer, full wave DC bridge and a thyristor. Again, wikipedia has a great picture of that

thyristor dimmer

Note that thyristor dimmers usually make some radio frequency noise but as I see it, this is one of the simplest AC dimmers.

You will find more info about different dimmers on http://en.m.wikipedia.org/wiki/Light_dimmer

And although you would like to keep out from MCUs, at least think about them. If the thyristor-stuff goes over your head, try to use MCUs. You will find them to be very useful for your future projects.