The Background

I bought a 200W magnetic LED driver with hopes of replacing the 40W Philips-supplied driver that came with my set of Hue Lily outdoor lights. Each fixture requires 8W at 24v. This new driver should allow me to add about 25 fixtures, instead of 5...

The (unexpected) Problem

I wired up the driver and tested the output with my multimeter: 24.1v. Perfect, so I brought it outside and hooked it up to the 5 already-installed fixtures. Nothing happened

Back inside, I retested the output and sure enough, it was 24v. This time, I intercepted the voltage in-line while I plugged in ONE fixture... A flash, and then nothing. The multimeter was now reading 38v!!

Why would a driver rated for constant voltage suddenly jump and destroy my fixtures?

  • 3
    \$\begingroup\$ Now that you feel there is a serious problem, get some high-watt resistor loads (start low-power and work up) and test the device with dumb resistors. Measure and record voltages as you increase (decrease the resistor value) the load on the power supply. If something is wrong with resistors alone, you may need to return it or get a new unit. (Or else there's something you are missing about proper operation and you aren't hooking things up correctly.) Main thing is to go into "test mode" now and keep it simple. \$\endgroup\$
    – jonk
    May 4, 2019 at 18:49
  • 1
    \$\begingroup\$ Not a lot of specs on the regulation error of magnetic regulated supply and LED current characteristics vs voltage. In these cases, you don't want to make a substitution from the recommended Philips supply without knowing this. There is no clear spec on how the Lights react to dimming function or the start surge current with smart dimming functions built into the lights. The supply may have tripped the over-current protection on startup and latched then not liked the step load on a powered up supply then sagged and overshot the output from no load to 1 LED load, poof. \$\endgroup\$ May 4, 2019 at 19:57
  • \$\begingroup\$ It's always a concern with lack of specs. The supply was designed for dumb LEDstrips that have no capacitance. An ICL surge limiter chip might have corrected this compatibility issue, if my hunch is right. \$\endgroup\$ May 4, 2019 at 19:57
  • \$\begingroup\$ I'm an amateur tinkerer, so I mostly understand what you're saying. Before I go down the road of testing, etc. I'm going to call the manufacturer... \$\endgroup\$ May 5, 2019 at 23:37

1 Answer 1


The power supply for the Hue spots is a constant voltage DC supply.
The power supply is not an LED dimmer.
The Hue hub communicates directly with each spot via ZigBee.
I assume each spot has RGBW LEDs and each requires at least 4 dimmers. This means a single PWM dimmer could not possibility control the Hue spots.

You only need to use a higher wattage DC power supply than the one supplied by Phillips.


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