J
julesg
Hi
I have been scratching my head over this one - first time posting on here, so "hello"!
What I am looking for is the *best* solution to provide 2.4V DC at 700mA to a high power LED from a 12V DC supply (motorcycle indicator in this case).
The spec' of the LED is:-
Max Forward Current: 700mA
Peak Pulse Forward Current: 1500mA
I would like to drive it at close to the max current for max brightness, which equates to 2.4V. Looking at the pulse curve for the LED it would appear that in my scenario (1 second on, 1 second off flashing) the pulse peak should be 1300mA falling to 900mA in 0.1 seconds.
To try out the LED I just used some 7W 15R resistors - which worked fine for a quick test, but obviously I can't use this for the long term solution.
I have considered using a voltage regulator with heat-sink to get from 12V down to close to 2.4V and then a resistor to trim to precise voltage. However, I am not sure if this is viable? The 12V supply is currently already passed through a flashing control so is switching at around once per second. I could re-arrange things so the voltage reg is supplied a constant 12V and flash the output, but would really prefer not to.
The only other option I am aware of for this kind of voltage reduction would be to use a DC/DC converter, but I believe there would be an issue with this as the LED would not provide the necessary feedback for voltage reference, without a constant current DC/DC converter which seems a little extreme.
So there it is. Any advice greatly appreciated.
Jules.
I have been scratching my head over this one - first time posting on here, so "hello"!
What I am looking for is the *best* solution to provide 2.4V DC at 700mA to a high power LED from a 12V DC supply (motorcycle indicator in this case).
The spec' of the LED is:-
Max Forward Current: 700mA
Peak Pulse Forward Current: 1500mA
I would like to drive it at close to the max current for max brightness, which equates to 2.4V. Looking at the pulse curve for the LED it would appear that in my scenario (1 second on, 1 second off flashing) the pulse peak should be 1300mA falling to 900mA in 0.1 seconds.
To try out the LED I just used some 7W 15R resistors - which worked fine for a quick test, but obviously I can't use this for the long term solution.
I have considered using a voltage regulator with heat-sink to get from 12V down to close to 2.4V and then a resistor to trim to precise voltage. However, I am not sure if this is viable? The 12V supply is currently already passed through a flashing control so is switching at around once per second. I could re-arrange things so the voltage reg is supplied a constant 12V and flash the output, but would really prefer not to.
The only other option I am aware of for this kind of voltage reduction would be to use a DC/DC converter, but I believe there would be an issue with this as the LED would not provide the necessary feedback for voltage reference, without a constant current DC/DC converter which seems a little extreme.
So there it is. Any advice greatly appreciated.
Jules.
