LED flicker

[hard-work]

A neighbour called me around to give a my view on their LEDs. In the bathroom there were three properly rated IP rated 12v MR18 halogen lamps. They changed them for the equivalent 5W 12v LED lamps. Total 15w.

When the lights have been off for a while and they are switched on there is no flicker. But if the light are on and off in quick succession for any reason they flicker. I have not looked at the transformer which is in the ceiling void preferring to get the views of people here first.

Is it that the transformer is is not rated low enough? Views would be appreciated before I look in their ceiling.

 

[bernardgreen]

Power supply ( 230 volts to 12 volts switch mode ) operating frequency may be interacting with the operating frequency of the switch mode current controller in the driver that is built into the 12 volt LED lamps.

 

[winston1]

LEDs require a special LED driver. You cannot use a SMPS designed for halogen lamps that most likely is still there. A real transformer is OK but most likely not fitted.

 

[aptsys]

Most likely if they have electronic transformers, the minimum load is not being satisfied. Either switch them for 12VDC constant voltage drivers or convert to mains downlights.

 

[bernardgreen]

LEDs require a special LED driver.

Which will be built into the lamp between the 12 volt supply input and the LED elements inside the lamp to control the current through the LED elements

 

[winston1]

Which will be built into the lamp between the 12 volt supply input and the LED elements inside the lamp to control the current through the LED elements

OK. Let's try again.

LED LAMPS require a special LED LAMP driver which is separate from anything inside the lamp itself. You cannot use a SMPS designed for halogen lamps that most likely is still there. A real transformer is OK but most likely not fitted

 

[bernardgreen]

OK. Let's try again.

LED LAMPS require a special LED LAMP driver

Not driver but a power supply that matches the needs of the lamp.

 

[aptsys]

OK. Let's try again.

LED LAMPS require a special LED LAMP driver which is separate from anything inside the lamp itself. You cannot use a SMPS designed for halogen lamps that most likely is still there. A real transformer is OK but most likely not fitted

No special LED driver required. A plain 12V power supply is sufficient as the LED driver is built into the lamp.

 

[hard-work]

No special LED driver required. A plain 12V power supply is sufficient as the LED driver is built into the lamp.

If the transformer is say 20w to 150w and the LEDs are drawing 15w, would that cause the flickering? Recall it does not flicker when the transformer is cold.

Replacing the existing IP rated 12v downlighter units to mains IP units is out of the question on cost grounds.

 

[stillp]

If the transformer is say 20w to 150w and the LEDs are drawing 15w, would that cause the flickering?

Very likely.

 

[hard-work]

Most likely if they have electronic transformers, the minimum load is not being satisfied. Either switch them for 12VDC constant voltage drivers.

So check the transformer's rating. If out of range then buy a transformer that is within range that is a `12VDC constant voltage`?

 

[hard-work]

Very likely.

That I can understand. But it does not flicker when cold and first switched on.

 

[winston1]

If the transformer is say 20w to 150w and the LEDs are drawing 15w, would that cause the flickering? Recall it does not flicker when the transformer is cold.

Replacing the existing IP rated 12v downlighter units to mains IP units is out of the question on cost grounds.

Better to find the money than wreck everything.

Or you need a 12 volt DC supply, or a real transformer. The 20 to 150 watt supplies are SMPS for halogen lamps (they are NOT transformers) as as I said previously they will not work properly with LEDs. Partly due to the loading and partly due to the fact that the LEDs are not designed to work at tens of kilohertz.

 

[hard-work]

It is a transformer, as it drops 230v to 12v. But are you saying it needs 12v DC not pulsating DC?

 

[winston1]

It is a transformer, as it drops 230v to 12v. But are you saying it needs 12v DC not pulsating DC?

That is not the definition of a transformer. Resistors can drop voltage but they are not transformers. Transformers are AC devices. They do not rectify.

LEDs require DC. Most LED lamps of the GU10 or GU5.3 type incorporate rectifiers so they can work on AC or DC, but AC at 50/60 Hz, not AC at tens of kilohertz.

As said several times your neighbour needs a proper LED power supply.