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rlynch:
What is an "electronic dimmable driver" for an LED lighting fixture? I don't know. Can you describe it.
Some general background information for you.
Broadly there are two ways to electrically adjust the light intensity for various bulbs, if adjustable, and excluding special ballasts for some bulbs. These are a variable auto-transformer or equivalent, or phase shift control.
The auto-transformer method retains at the output a sine wave, but of adjustable amplitude. Thus, peak voltage or current, and average voltage or current are adjustable resulting from the amplitude adjustment.
In phase shift control or something with a similar effect, some portion of the cycle is off and the other portion looks like the input. Here average voltage or current is adjustable by the amount of on time in the cycle.
Different loads respond to these waveforms in different ways.
You need to understand the theory of your dimmer, and the way your load responds to the waveform.
With a Variac dimmer and an incandescent lamp the dimming action is very good and allows dimming to 0 light output. This is basically an adjustment of the current thru the filament and therefore its temperature. With a Sylvania A19 LED dimming action is good and down to 0 light output, but much of the major dimming occurs at lower voltage, whereas much of the dimming action of an incandescent occurs in the higher voltage range. Some standard CFL bulbs dim fairly well, but can not be dimmed to anything like 0 output. A GE dimmable CFL shows little light change down to about 100 V, then just quits.
With what I describe as a three terminal dimmer of the phase shift type by Lutron the results are:
With a standard incandescent lamp good control down to a moderately low intensity, but not as low as I would like. They do not shift the turn on point close enough to 180 deg.
With a GE dimmable CFL dimming is possible, but not to a low enough level. With regular CFLs you can describe dimming as not available, and a high probability of damaging the bulb.
The Sylvania LED works fairly well except because of the dimmer design the low intensity end is still fairly bright. This is a problem of the dimmer and not the bulb. Also note this is an 8 W bulb with no additional load on the dimmer.
A three wire dimmer by my definition is one where the dimmer uses supply voltage for powering the electronics, and the electronics is not dependent upon current thru the load for its power. This requires hot and neutral at the input, and the output hot is modified in waveform, and the same neutral as at the input is used for the output. The three wire dimmer has better control at low light levels and automatically restarts on power loss when at a low intensity setting.
Lutron has no idea of what I am talking about when I use the term "three wire dimmer" when in fact they make such a device. It happens to have 5 wires. The extra wires are green (EGC), and red (a switched full voltage output). This dimmer is designed for regular dimmable fluorescent fixtures, and thus the need for the switched full voltage output to power the bulb filaments.
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