Flickering 12V LED downlighters

[bruce_the_loon]

I've been reading through the other thread on 240V or 12V downlighters and I picked up on the comments about flickering 12V LEDs when plugged into existing fittings with either central or per-fitting transformers.

I wonder if the issue is arriving from the fact that some downlighter transformers are producing 12V AC and the LED bulbs need 12V DC power. A halogen bulb won't care about this and neither will LED bulbs if they incorporate a rectifier circuit in the bulb.

A 240V AC LED bulb incorporates a power supply to produce the right voltage for the LED emitters, but a 12V DC bulb probably only has a dropping resistor.

It would mean that 12V downlighter transformers will need to be replaced with a DC power supply or, probably easier, use 240V AC bulbs instead.

 

[me_]

You technically aren't supposed to run an LED off a standard 12V AC transformer. You are supposed to use an LED driver: http://www.oznium.co.za/led-lights/9w-cree-compact-spotlight/
An LED driver does produce DC output and it doesn't have a minimum power requirement (like the electronic 12V AC transformers).

 

[bongski87]

When i first started using 230v led gu10 and LED floodlights on an emergency circuit to be powered by a ups/inverter and a generator, the flickering LEDs even when the cuircuit switch is off was a puzzle. Thought it were defective globes since not all the globes were flickering. Changing the globes did not solve it.Checking the polarity of the homemade extension socket where the ups/inverter was plugged, showed that the earth was cut and the neutral and line were also reversed. Rearranging the wires in the socket to the proper polarity solved the problem. No more flickering.

Off topic but a bit related, I found out that LEDs are more prone to failure due to transient voltages such as those coming from a near lightning hit. I had a street light circuit with a mix of different LED lights from mr light, phillips, osram and eurolux, and several CFLs and halogen. A lightning storm passed by and the circuit breaker was tripped. Resetting it , i found out that all the LEDS were kaput, but the CFLs and halogen were still working. Had to replace the LED globes with that of of the cheaper CFLs afterwards

 

[Gnome]

I've been reading through the other thread on 240V or 12V downlighters and I picked up on the comments about flickering 12V LEDs when plugged into existing fittings with either central or per-fitting transformers.

I wonder if the issue is arriving from the fact that some downlighter transformers are producing 12V AC and the LED bulbs need 12V DC power. A halogen bulb won't care about this and neither will LED bulbs if they incorporate a rectifier circuit in the bulb.

Actually that sounds very plausible. They don't say 12v DC, they just say 12v.

A 240V AC LED bulb incorporates a power supply to produce the right voltage for the LED emitters, but a 12V DC bulb probably only has a dropping resistor.

For AC they use a very simple switch mode circuit. For the DC case I wouldn't be surprised if they just put a bunch of LEDs (the actual LEDs) in series and call it a day.

It would mean that 12V downlighter transformers will need to be replaced with a DC power supply or, probably easier, use 240V AC bulbs instead.

12v lights were a fad. Get away from them if you can.

My 2c.

When i first started using 230v led gu10 and LED floodlights on an emergency circuit to be powered by a ups/inverter and a generator, the flickering LEDs even when the cuircuit switch is off was a puzzle. Thought it were defective globes since not all the globes were flickering. Changing the globes did not solve it.Checking the polarity of the homemade extension socket where the ups/inverter was plugged, showed that the earth was cut and the neutral and line were also reversed. Rearranging the wires in the socket to the proper polarity solved the problem. No more flickering.

The polarity doesn't really make sense...

I mean, I believe you, but I'm trying to think of a reason it would matter.