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| FL5150 Light Dimmer Circuit |
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| Chet T16:
Hey all, I've built up a proof of concept dimmer that uses an ON Semi FL5150 dimmer controller and a Power Integrations LNK3204 demo board. The lnk3204 demo board has been modified to give 18v output and 300mA with an LNK3206. I've also switched the live and neutral inputs. Schematic attached as rdr506.png The FL5150 schematic from the datasheet is attached as fl5150circuit.jpg. Its actually the 120v 60Hz circuit but its the same for the 50Hz. The FL5150 derives its 17v VS power from the mains via resistor R1 in this circuit but in an effort to reduce power consumption I am feeding the output of the LNK3208 into the VS pin directly. My schematic is attached as fl5150_schematic.jpg The problem i'm seeing is that one of the output IGBTs/FETs are not turning off. I originally had two IGBTs in there, when it didn't work i swapped them out with the same result. I then replaced them with two mosfets. The mosfets are 07N60C3's and the IGBTs are NGTB10N60R2DT4G's. A scope trace is attached as scope.jpg Looking at the schematics now after a few days away I'm wondering is there some offset to ground being created by the diode D2 in the LNK3206 circuit that is preventing one of the transistors turning off? |
| RPLaJeunesse:
I suspect the LNK3206 stage is screwing something up, as the FL5150/60 chip GND pin needs to connect to the AC lines only through the MOSFET source pins & body diodes. As a quick test try using an isolation transformer to power the LNK3206 circuit. It might also help to draw up a full schematic so you can see what might be duplicate current paths. (FWIW I'm working on a trailing edge dimmer adapted from an old EDN design idea, and have been looking at the FL5160 as my next to try.) |
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