Tom Baldwin Posted October 31, 2009 Share Posted October 31, 2009 We're all familiar with ghost loads, for when the dimmers won't play nice with an unusual load... but how do they actually work? I'm running some LED fairy lights via a Minipack at the moment, and they won't extinguish at 0% control input (preheat=off) without a ghost load. Fine, problem solved... but what actually just happened?The LEDs are not an inductive load (there's no transformers in this circuit, just bridge rectifiers and LEDs), so I & V shouldn't be out of step. Can anyone give me a detailed technical explanation of what the extra resistance of the ghost load is doing, in terms of the triac, snubber etc? Thanks! Tom Link to comment Share on other sites More sharing options...
J Pearce Posted October 31, 2009 Share Posted October 31, 2009 The LED fairy lights probably don't present enough load for the triac to operate properly. A triac needs a certain amount of load in order for it to open and close properly. With less that this load the triac might stick on, and not turn off. The dummy or ghost load puts enough load on the triac for it to operate correctly. Link to comment Share on other sites More sharing options...
DrV Posted November 1, 2009 Share Posted November 1, 2009 Any triac based dimmer passes a certain amount of leakage current. Semiconductors aren't perfect switches and also, filter components connected in parallel with the triac will allow a certain amount of current to pass even if the triac IS perfect. It may only be a milliamp or two but some LEDs only require a miniscule amount of current to operate, hence they end up being illuminated by this leakage current. By sticking a ghost load on the dimmer you are giving this current somewhere to go instead of through the LEDs. HTHDave Link to comment Share on other sites More sharing options...
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