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I mistakenly connected a power charger in series with my ceiling led lights... oh... whell... the reality is more complex, but essentially: 1) when the switch is off, the phone power charger is in series with the lights, the lights do switch off in this case (I presume because of too low voltage), and the charger works correctly 2) when the switch is on, the phone charger is shorted and goes off, but the led lights go on correctly.

The scenario 2 is of little interest to me.

Of course when in 1) they are in series they will not get 220V* each as normal/parallel connection, but a smaller portion. (*I am in europe)

It is my understanding that an electronic device may try to draw more current if working under lower voltage than what it should get, in order to generate the same amount of Watts and operate correctly.

In short: I am concerned about the power consumption in scenario 1). This is 99% of the time of course, and the main concern is that electricity will have to go through the led bulbs evenduring the 99% of the time while they are off.

Can anyone help?

Leds are non dimmable if that makes a difference, the mobile charger is of course 220/120v , this is hardwired in behind the wall, so no risk of someone coming in and connecting their hair dryer in place of it :D

Thanks for any help!!

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    \$\begingroup\$ Draw schematic! \$\endgroup\$ – winny Sep 5 '17 at 18:13
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When the switch is off, power is applied in series to non-dimmable buck regulated LED and buck regulated phone charger. The impedance of the Bulb must be lower so it sees an undervoltage conduction but may still be passing current and getting conduction losses.

You may check to see if the bulb gets warm even after a while indicating efficiency loss and beware that you have no power off condition or switch to enable both. Fix it properly.

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When the two devices are connected in series, the current through each of them will be the same, no matter how the voltages split.

When the phone charger is not actually charging, it will do its best not to pass any current (except for the small quiescent current the regulator circuit needs to work), which means that there is no current for the LED lights to work with. Thus the charger will actually see close to the full line voltage.

This goes no matter whether "not charging" is because there's no phone connected, or because the battery in the connected phone is already fully charged.

When you actually start charging, the charger will start drawing a current, which gives the lights a chance to consume power. If the lights were a good old-fashined ohmic(ish* load such as incandescents, we could compute how much power they would get if the charger does its best to maintain, say, a steady 5 W consumption.

However, LED lights are very much not ohmic, and will usually contain their own switching regulator to make sure each individual LED gets the current they want (since LEDs are much more picky about their current than filaments are). What do you get when you put two switch-mode power supplies in series and let them compete for the same supply voltage? Chaos and instability, that's what -- potentially with more than one possible equilibrium. What happens when the dust settles could depend heavily on the internals of each of the regulators. It sounds like in your case it ends with the lights being starved and the charger still seeing close to full line voltage. (It looks to me like this is the likely outcome when the native power demand of the lights is several times that of the charger).

In this situation the lights will still see too low a voltage to work correctly, but will pass enough current to allow the charger to work. Because of the low voltage, only a small amount of power will be delivered to the lights.

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I totally agree that I "should" fix it... however the way the apartment is cabled, the cables run through the ceiling to the lamp, and then only the live cable comes down to the switch... I don't know exactly what is the reasoning behind this, I do understand it may have some good reason such as saving on cables and/or allowing to have separate general switches for lights and power , etc... it still seems dumb to me, but it's beyond the scope of this conversation I suppose!

Anyway... I now measured the voltage between the 2 poles of the charger and it goes like this:

1) Lights off - charger connected and charging phone ~192V (hence ~30v are on the lights) 2) Lights on - charger connected to phone (but not chargin as described aboveg) ~0V (as expected, as it's shorted with lights on) 3) Lights off - charger not charging ~200V (hence ~20v are on the lights) 4) Lights on - charger not charging ~ -5V (negative... weird, but more or less as expected)

Now... the charger operating @ 190V/200V cannot be using all that much extra power compared with when operating @ full 220V... so it seems my concerns can be settled from that point of view :)

Thank you everyone for all the help, it was greatly appreciated and extremely useful to getting this understood!

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  • \$\begingroup\$ FYI: This is not a forum, so generally, questions are for questions and answers are for answers only. If you have additional information, add it as a comment or add it to your question as background info. Conversations / responses to other people don't belong in an answer, as it clutters information. \$\endgroup\$ – Bort Sep 7 '17 at 18:32

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