I have a light fixture I just converted to LEDs. It uses a 12V LED strip cut into 4 sections, with each pair connected to a 40W constant voltage 12V power supply. Each pair draws about 28W.

When I turn on the lights the strips flicker fast and randomly like it's a rave and eventually, after 15-20 seconds, they stop and output normally. If I turn off the lights and turn them back on without waiting much they turn on normally without flickering. But if I let them "cool down" for a while the cycle starts again.

I've tried to search why this is happening but found nothing applicable: the power supplies are properly sized and it shouldn't be an issue with connections, since the flickering eventually goes away on its own.

Any idea why this is happening and how to fix it?

  • when cold they draw more
    – Traveler
    Oct 2, 2022 at 2:38

1 Answer 1


To make the system more stable, try adding an electrolytic capacitor across the power supply. A starting value would be 500 or 1,000 microfarads (µF) at 20 VDC or higher. N.B.: Connect + of the cap to + of the supply.

BTW, a constant current supply is recommended for LED's... do the strips contain a small current limiter? If so, there could be an interaction between the two power supplies, which could require a small disc capacitor, perhaps 0.1 µF at 20 VDC or higher.

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