Hey guys, I am using a high powered LED from CREE (XHP70B-00-0000-0D0BP20E2). The datasheet says the forward current draw is 4.8 amps at 6.0 volts. I dialed in 6.0 volts on a bench power supply, and started dialing the current up. At 6 volts I was only getting 2.5 amp draw (if I turn the current up to max)... but as it heated up, the amp draw slowly increased. I found that if I increase the voltage up to 6.5 volts, then I could get the 4.8 amps.
So this brings me to my question: if I design a power supply that has a built in programmable peak current draw limit, for example using a TPS61088 or TPS61178, do I just set it to 6.5 volts, and 4.8 amp peak current limit? Or would I want some headroom and do something like 6.7 volts, and still limit current to 4.8 amps?
What if during runtime I want to dial the peak current limit down (to dim down the LED), to say 1 amp peak. Would the 6.7 volts still be ok in this situation? I am not quite wrapping my head around this. And the whole point is that I don't want to use a resistor, I want to limit the current via the power supply so its efficient and not generating more heat than necessary. Am I going about this all wrong?
Thanks and any help or advice is greatly appreciated!
So this brings me to my question: if I design a power supply that has a built in programmable peak current draw limit, for example using a TPS61088 or TPS61178, do I just set it to 6.5 volts, and 4.8 amp peak current limit? Or would I want some headroom and do something like 6.7 volts, and still limit current to 4.8 amps?
What if during runtime I want to dial the peak current limit down (to dim down the LED), to say 1 amp peak. Would the 6.7 volts still be ok in this situation? I am not quite wrapping my head around this. And the whole point is that I don't want to use a resistor, I want to limit the current via the power supply so its efficient and not generating more heat than necessary. Am I going about this all wrong?
Thanks and any help or advice is greatly appreciated!