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I have a led driver (LPC-20-700) that is 30V and 700mA, which makes it 21W.

I run 10 leds (≈ 2.8V drop) in series with it and it is an constant current device. If I plug my multimeter between, I do get the reading of 700mA.

When I use a little device (AC power consumption meter?) that checks the power consumption of devices I plug into DC, the reading tells me it's only 5.6W.

I can't wrap my head around what I'm missing here. Why are the numbers not equal?

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    \$\begingroup\$ What "little device that checks the power consumption" are you using? \$\endgroup\$
    – Ron Beyer
    Jan 15, 2018 at 17:36
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    \$\begingroup\$ How are the LEDs connected? How is the LED driver connected? Please show a schematic. \$\endgroup\$
    – vofa
    Jan 15, 2018 at 17:41
  • \$\begingroup\$ @RonBeyer I edited my question and added more information. \$\endgroup\$
    – Badr Hari
    Jan 15, 2018 at 17:47
  • \$\begingroup\$ @vofa The leds are just in series and the driver powers them. \$\endgroup\$
    – Badr Hari
    Jan 15, 2018 at 17:47
  • \$\begingroup\$ Are the LEDs all lighting up? \$\endgroup\$
    – Finbarr
    Jan 15, 2018 at 17:48

1 Answer 1

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This is a constant current driver that regulates its output voltage in order to generate the specified current.

30V is the maximum that your driver can output in order to drive 700mA through the LEDs. In practice, it will usually output a lower voltage depending on what sort of LEDs you have connected.

However, 5.6W would suggest an output voltage of just 8V, which is well short of what you'd expect to see across ten LEDs wired in series, so I suspect that either your device is not measuring what you think it is or your LEDs are not wired in series.

Use your multimeter to measure the output voltage across the LEDs and see what you get. Assuming you are still getting 700mA through the LEDs the actual power will be 0.7 times the actual voltage.

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  • \$\begingroup\$ Thank for taking time, I'm a real dumbass and connected them in parallel. I even don't know why or how I didn't notice it. If it makes any better, your answer made me realize. Mods please delete, close this question of ban me. \$\endgroup\$
    – Badr Hari
    Jan 15, 2018 at 17:54

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