dimmer switch for leds

I bought a light dimmer from IKEA.
If I connect my dimmer switch to a normal bulb and slide the controller from off to on slowly, the light intensity slowly increases from off to
full brightness.
If I connect a string of LEDs to the dimmer and do the same sliding from off to on, the bulbs first increase in brightness, then decrease in brightness to almost off, then increase again to full brightness. Why?
I'd appreciate any help you can offer.
Thanks ~Helen
(PS) I did a little research on how dimmer switches work, and they work by turning on the incoming AC signal only when it reaches a certain nonzero threshold, then keeping it on for the rest of the cycle. (The technology is called TRIAC - see http://en.wikipedia.org/wiki/Triac ). But, I don't see why this would cause the local minima in the led current.
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Two possible reasons... Simple triac dimmers have a minimum load requirement for proper operation. It may be that the load presented by the LED power supply is too low, or that it doesn't present a resistive load and meet the minimum requirements throughout the whole waveform. Add a regular lamp too, and see if that fixes the problem. Secondly, the LED power supply may well not be designed to take a phase controlled input waveform and generate a varying LED current from it. Does it claim to be dimmable?
--
Andrew Gabriel

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Andrew Gabriel wrote:

I will try this, good idea. Now to find a 2-pronged outlet extender...

No, the LED string does not claim to be dimmable. I'm sure the LED's AC->DC power supply is not intended to be used this way, but I just want to figure out from a circuits point of view what the likely source of this behavior is.
Thanks for your help.
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SIMPLE dimmers need a resistive load (for example a bulb filament) and in particular don't like to drive loads with conduction thresholds, like a bunch of LED's in series . Test this: put in parallel to the LED cluster a normal low wattage incandescent bulb. I bet that in this case you will have a perfectly working dimmer, because now, at least, some of the current passes through a resistive element (bulb filament). An analysis of a typical simple dimmer circuit would easily explain the reason
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to turn a diode into a resistive load, you should put a resistance with it.
EpsilonRho wrote:

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to turn a diode into a resistive load, you should put a resistance with it.
EpsilonRho wrote:

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