What happens if I power a 12 V LED lamp at twice its voltage with a 24 V power supply?

Question

If I have an LED lamp which is specified as, say, 350 mA at 12 V DC, what would happen if I fed it directly from a 48 V DC constant-current power supply capable of providing up to 350 mA?

I understand increasing the voltage on an LED lamp typically makes it run hotter as it tries to draw more current, but since it is fed by a current limited source is this issue voided?

Edit: I am talking about higher-powered LED lamps, like ones used for outdoor lighting such as streetlights, garden lights, etc. Say a maximum wattage of 30 W.

Answer 1

If it is a constant current driver, it will drive the LED with constant current and the LED voltage ends up being 12V or whatever it happens to be with the LED.

So the output voltage to LED must be identical with identical current, the output voltage from CC driver can't be any higher or different, or a different amount of current would flow.

Another thing is, does the constant current driver support 12V LEDs or not. It depends on the output range it requires to operate properly.

Answer 2

That is a "lamp" not an "LED". Yes, it uses LEDs inside it, but it also has electronic components to limit the current. Therefore, the answer is not straight forward because it depends on what those electronic components do:

I see these possibilities:

• It uses resistors: at 48 V the current would increase, possibly 10-fold; the supply is current limited to 350 mA; the result is that its output would stay at 12 V; therefore, no change
• It uses resistors: at 48 V the current would increase, possibly 10-fold; the supply is current limited to more than 350 mA, say 500 mA; the result is that its output would go up to, say, 14 V; therefore, the lamp would be brighter; at least for a while
• It uses resistors: at 48 V the current would increase, possibly 10-fold; the supply is current limited to more than 350 mA, say 500 mA; the result is that its output would go up to, say, 14 V; therefore, the lamp would be brighter but it can't handle it; it blows up: no light
• It uses resistors: at 48 V the current would increase, possibly 10-fold; the supply is not current limited and it blows up: no light
• It uses a current source: it that can handle 48 V; the LED would still see the same current: no change
• It uses a current source: it that can handle 48 V but not the heat; the LED would still see the same current; after a while, the current source overheats and blows up: no light
• It uses a current source: it that cannot handle 48 V; it blows up: no light

In summary, the most likely result is that either the power supply or the lamp blows up.

Answer 3

I understand increasing the voltage on an LED typically makes it run hotter as it tries to draw more current, but if it is fed by a current limited source is this issue voided?

Not only will it run hotter, it is likely to burn the LED and destroy it. A 350 mA constant current supply does what it says on the tin; it provides the current required by the LED (if 350 mA is what the LED specification indicates).