# What's the voltage used to power LEDs inside an LED light bulb?

I have opened an LED light bulb today, and there are two thick wires sticking out of the center to power the LEDs.

I know it will vary by design, but I can't find even a range of voltages, therefore I ask. What is a typical voltage used to power the LEDs in such an LED lightbulb ?

• Depends on country too. And the power supply it has in the base. It all has to do how many LEDs are in series, and if those are single LED packages or multi-LED packages. Guessing 70 to 200 volts. And they are not safe to touch as they can be assumed to be not isolated from mains. – Justme Jan 21 at 20:52
• As you said, it varies based on the design. Somewhere from 2V up to 300V. – user253751 Jan 21 at 21:11
• Usually voltage is pretty close to, but lower than, rectified line voltage in order to keep costs low. That is why 9v LED packages exist (3 diodes in series in one package). – user1850479 Jan 21 at 21:37
• Ah, Big Clive is my friend. :) bigclivedotcom on tearing down LED lamps youtube.com/user/bigclivedotcom/search?query=LED+lamp. – tlfong01 Jan 22 at 1:08
• @Mike Schroedel, I have almost completed my answer. Big Clive's YouTube (Ref 1) is the best reference I found on power electronics on LED, explaining how the "Capacitive Dropper" is used to interface directly with 110~230VAC, not using transform or switching power circuits. He even guided me how to read the power electronics IC datasheet and commented on the critical part of the schematic. I really enjoyed his lecture! :) – tlfong01 Jan 22 at 7:15

White LEDS start at 2.85V and operate near 3V. The designer chooses series, and maybe shunt arrays for redundancy to match the generated voltage. So if there were 80 LEDs that's almost a 240V string or two 120V strings.

The big contacts in the centre are for mechanical rigidity not current.

Count the LED's (in series) and multiply by ~2.8V

I did this the other day, get a variable power supply that can go up to 50V and has a current limit.

Plug in the LED's to the supply with the correct polarity (and make sure the electronics are removed)

Then set a current limit at say 50mA and set the voltage high, like 40 or 50V. Then keep turning up the current limit and watch the voltage go up. When the LED's get about as bright as they are in the bulb then record the voltage and that's how much they would take.

Make sure you don't apply too much voltage, because it could burn them out.

• For multi-chip LEDs, it also needs to be multiplied by LED chips in series inside the LED package (which might be 1 but in case it isn't). – Justme Jan 21 at 21:20
• Good point (I guess my count the LED's statement still holds) – Voltage Spike Jan 21 at 21:21

Question

What is a typical voltage used to power the LEDs in such an LED light bulb as shown below?

1W Power LED Tutorial - Components 101

1. Voltage applied between Anode and Cathode: 3.0 V to 3.5 V (Typical Operating Voltage : 3.3 V)

2. Current through LED (Light Emitting Diode): 300mA to 350mA (350mA being absolute maximum forward current allowed through LED)

3. Operating Life: 100000 hours