LED drivers suitable for groups of LED lamps

Question

Summary

Replacing MR16 SELV AC halogen spots with 12VDC LEDs. The halogens have individual drivers - need advice replacing these with (fewer) DC equivalents.

Setup

2 rooms with AC 240V supply, 6 lamp + 3 lamp
12VDC MR16 LED spots, 5W 660mA
These are smart - powered all the time and draw very low wattage when the light is off
Existing SELV AC drivers cause the DC LEDs to flicker inconsistently, and not turn on reliably

Constraints

Cost: Single driver for each room rather than 9 drivers

Question and Current Understanding

What drivers are suitable (+link to an example)?

Current Understanding:

DC driver to avoid flickering and damage to the smart components
Driver that supports a minimum wattage of close to zero, and a max of (5W*lamps_in_room)+20% headroom = ~36W and ~18W
Unclear on whether I need a constant current 660mA driver, or a constant voltage 12V driver, and whether to wire the lamps in series or parallel on each

Prior Research

I have asked lighting supply companies without success, and reviewed multiple StackExchange questions.

If they are "Smart", then they have their own control and current regulation, you need to only supply the appropriate voltage (12V). Please give us some pictures, models, wiring diagrams of exactly what you have and what are you trying to achieve. Don't shy away from details, the more you give us, the better we can help you. — Edin Fifić, Apr 25 '23 at 18:07
Added link to LED product data sheet. You're suggesting a 12V constant voltage driver? Should I wire them in series or parallel? — xddsg, Apr 25 '23 at 18:13
Loads which require constant voltage are connected in parallel (while not exceeding the maximum supply current), and those which require constant current go in series (while not exceeding the maximum supply voltage). — Edin Fifić, Apr 25 '23 at 18:16
If you want them to be dimmable, they will have to be wired in parallel. — Andrew Morton, Apr 25 '23 at 18:17
@AndrewMorton they have a on/off switch at the wall, but 'dim themselves' wirelessly. Does that change anything? — xddsg, Apr 25 '23 at 18:26
@EdinFifić they lamps specify 660mA on them, it is possible to buy constant current drivers with this spec. It seems unusual for them to have the current on rather than (W)atts if they are constant voltage? — xddsg, Apr 25 '23 at 18:28
@xddsg That counts as being dimmable. If the lamps are in series, then each one of them has the same current flowing through it as the others. A dimmed lamp has less current flowing through it, and so all the other lamps will get confused. If the lamps are in parallel, they can each have a different current independently of the others. — Andrew Morton, Apr 25 '23 at 18:28
@xddsg The lamps you linked to specify that they work on 12 V AC 50–60 Hz, DC does not fall into that range. Do you have any other information that they will work on 12 V DC? — Andrew Morton, Apr 25 '23 at 18:39
@AndrewMorton I believe they may be like this lamp https://www.ledvance.com/consumer/products/lamps/led-lamps/led-reflector-lamps/low-voltage-led-reflector-lamps-mr16-with-retrofit-pin-base-c6856 ...which is AC & DC. I have asked the manufacturer but they have not replied for over a week. — xddsg, Apr 25 '23 at 18:48
@xddsg *If* the lamp contains a bridge rectifier then running it on DC will result in two diodes having twice the expected average current, in which case they may not be rated for that. — Andrew Morton, Apr 25 '23 at 18:59
@AndrewMorton OK, AC it is. Series or parallel wiring? Following that, your comments have answered all my queries, thank you very much. Happy to mark an answer you make as accepted (if you wish). Otherwise I will accept the similar answer. — xddsg, Apr 25 '23 at 19:06
@xddsg I am not a qualified EE, so I would rather not put *my* name to an answer dealing with something that could burn down your house if it goes horribly wrong... — Andrew Morton, Apr 25 '23 at 19:09
@AndrewMorton understood. I take full responsibility for my own actions. In your unqualified opinion, should the lamps be wired in series or parallel on a 12V AC driver? — xddsg, Apr 25 '23 at 19:15

score 1 · Accepted Answer · answered Apr 25 '23 at 18:55

1

The lamps you linked are 12V AC (not DC) lights. You should power them with a normal 12V AC transformer. They include their own internal drivers. They might also be ok with DC, but I don't see that in the datasheet and it's not a good idea to ignore specifications when wiring something in your home.

If you want to use DC lighting, you would buy DC lights, wire them in parallel and then use a constant voltage DC supply.

answered Apr 25 '23 at 18:55

user1850479

14,842
1
21
43

My understanding as that even if they are AC, and internal rectifier makes them into DC (but with flickering). DC to the rectifier it fine(?) and removes the flickering. If I use a 12V AC transformer, I need one that can output between zero and the calculated (W)attage? – xddsg Apr 25 '23 at 18:59
series or parallel wiring for the AC transformer? – xddsg Apr 25 '23 at 19:15
@xddsg Maybe you should hire an electrician to make sure this is done safely. – user1850479 Apr 25 '23 at 19:30
1

The rectifier may not be rated for DC input (100% duty cycle on two diodes and 0% on the other instead of 50% on all four) or it might not use a bridge rectifier at all. And of course if there's a transformer or capacitive dropper in there, DC won't work. – vir Apr 25 '23 at 19:33

score 0 · Answer 2 · answered Apr 25 '23 at 19:18

The reason they flicker is because they require a standard steady sine wave AC and are not dimmable by chopping up the sine wave as is done with classic TRIAC control dimmers. I am not familiar with SELV drivers but I suspect that's the way they work.
You don't need a constant current driver, the 660mA specification is the maximum (peak) current draw and it tells you the minimum current your supply would need to provide for the lamp.
From what I can understand, these lamps include wireless drivers inside them, so all they need is that a Zigbee wireless controller.