Hello. I want to find the power dissipation in my IR diode. I'm using pwm/pulses of 1/3 of the time it's on. It can handle 100 milliamps 100% of the time and 1 Amp when pulsing it. I want to know if 1/3 of the time is too short of a pause between pulses (200/400 microseconds)? It's maximum powerdissapation is 190 miliwatt and the resistor i'm using is 1,5 ohm.


Thank you in advance

 

"Hello. I want to find the power dissipation in my IR diode. I'm using pwm/pulses of 1/3 of the time it's on."

Do you mean that the duty cycle is 33.33%?

" It can handle 100 milliamps 100% of the time and 1 Amp when pulsing it. I want to know if 1/3 of the time is too short of a pause between pulses (200/400 microseconds)? It's maximum powerdissapation is 190 miliwatt and the resistor i'm using is 1,5 ohm."

We can not calculate the power dissipation if we do not know what the voltage is, so what is the supply voltage and part number of the diode?

 

The IR diode has no part number for us to see its detailed spec's.
The resistor value is useless without us knowing the LED's forward voltage and your power supply voltage.

 

Hello. I want to find the power dissipation in my IR diode. I'm using pwm/pulses of 1/3 of the time it's on. It can handle 100 milliamps 100% of the time and 1 Amp when pulsing it. I want to know if 1/3 of the time is too short of a pause between pulses (200/400 microseconds)? It's maximum powerdissapation is 190 miliwatt and the resistor i'm using is 1,5 ohm.


Thank you in advance

If it can only handle 100mA continuous, you cannot pulse it at 1000mA 1/3 duty cycle. That would be 3.3 times the average power .

Bob

 

For 100mA continuous rating than you should pulse it at most 10% of the time a 1A, probably more like 5% for reasonable derating.

 

If it can only handle 100mA continuous, you cannot pulse it at 1000mA 1/3 duty cycle. That would be 3.3 times the average power .

Bob

OK. Yes, it might not work in real life. However, I would like to calculate the power dissipation anyways, from this scenario. What formula should I use or how should I do this?

 

Yes. 33.33%
I am not sure about the voltage supply. I was wondering if I could use the formula: I^2*R ?

 

I am not sure about the voltage supply. I was wondering if I could use the formula: I^2*R ?

You would use I*V where I is the current through the diode and V is the voltage across the diode at that current.

 

Like crutschow says, try I*V. For example, if the forward voltage drop thru the LED is 2.0V, then 100mA through it would have 200mW dissipation. If forward voltage drop through the IR is higher, like 2.5V or 3.0V, you get 250mW or 300mW respectively.

 

Can you please supply the part number and name of the manufacturer, or just post the datasheet here.

The average power dissipation is = (peak current) X (voltage across the diode while that current is passing through it) X (duty cycle).