Not too long ago, I installed one of those cheesy "puck" light kits from Home Depot for my neighbor. Anyway, I was really suprised to read the specs on the transformer that say it operates at 12 volts at 20 kHz!

Yesterday, I was putting up some low voltage track heads with an MR16 lamp, also with an electronic tranformer. Curiosity got the best of me, so I opened one up and looked inside.

Here's what I found: a cicuit board containing a small magnetic transformer, 4 diodes, some resistors, a couple caps, a coil, and 2 transistors mounted on a heat sink.

So, with my basic knowledge of electronics, I guessed the following: The magnetic transformer steps 120 volts down to 12 volts, and the 4 diodes make up a full-wave rectifier, which converts AC to pulsating DC. After that, I'm lost, and I have no idea what the other components do, even though I know how transistors, caps and coils work. I suspect they may have something to do with increasing the frequency. [Linked Image]


1. How do these work? What do the transistors do?

2.What is the advantage of operating halogen bulbs at such high frequency? More light output?

3.Don't these transformers intoduce undesirable radio frequncies and harmonics into power lines? I'm thinking of the full wave rectifier here (aka switching power supply).

*calling pauluk*