LED Lamp Identification

Hi Folks,

I’m trying to answer a few questions relating to LED lamps and was hoping you might be able to assist as I know very little about such things:

I have two different unidentified types of 20 LED, 4W, GU10 lamps both of which are fitted with a different PCB, could someone tell me what the difference between these would be (I suspect one is dimmable and one is not?).

Secondly would either or both of these lamps be compatible with a dimmer switch?

Thirdly would they be suitable for replacement in a ceiling light fitting connected to a normal 240V AC UK domestic lighting ring?

Is there a known issue for an internal capacitor failure occurring within these units.

Thanks in advance for your help.

SA4

The one on the left is not regulated. The circuit that it uses is utter crap. Produces 100/120 Hz flicker. The LEDs can easily fail and when one goes the rest are not far behind. Also, there is no electrical isolation of the power line to the LEDs. It is probably illegal to sell in most places.

The one on the right is regulated. LEDs can fail less easily. Bulb is still crap. I would not use either.

Judging by the size of the LED’s I would hazard a guess that they’re Nichia 5050 SMD’s

http://sell.pakuya.com/product-info/143903/5050-SMD-LED-Warm-White.html

I would not be so sure.
Can you see this flicker? I can’t.
Usually there is a capacitor 5µF 400V parallel to LEDs (perhaps the OP can add one).
Diodes in general can withstand current pulses several times the normal current.
This circuit has two advantages : better efficiency, produces no interference.

That simple circuit uses a series capacitor as a current limiter. The capacitor/resistor is selected to match the LED configuration. It depends upon the LEDs all being good. Once one goes or they start to change values, a cascade failure usually happens. Also it provides no protection against current spikes and voltage overloads. It is a cheap and dirty way to drive LEDs. And many people are very sensitive to the flicker that it produces. LEDs are not like incandescent bulbs… they don’t have thermal lag in a hot filament to smooth out the 120 Hz flicker.

Why is it crap (for those of us who don’t understand electronics)

Those SMD 5050 LEDs tend to have very poor CRI. Also they are usually wired in series/parallel arrangements that invite current hogging failures.

I also don’t trust that driver to meet UL/CSA safety regulations (see HKJ’s USB adapter teardown thread for what to look for). I’ve taken apart several of those type bulbs… and was usually scared of what I saw. G10 bulbs are very tight for space and that does not leave much room for required clearances.