LED surge current rating

[eem2am]

led surge current

HELLO

What is the maximum forward surge current for a power LED?

(eg for a 350mA LED, what is the surge current withstand? 10A? 20A?)

There datasheets never state it

eg

https://www.philipslumileds.com/pdfs/DS56.pdf

 

[FvM]

led surge forward current

When the datasheet tells maximum pulsed forward current and nothing else, this is the specification.

But I can't agree regarding datasheets never state it. Osram datasheets generally have a permissible pulse handling diagram.

 

[eem2am]

led current rating

Thankyou FvM,

i looked at the Osram LD G5AP LED

**broken link removed**

...and its Average current rating is 200mA.

....The datasheet says it can survive pulses of 1000mA as long as the pulses are for less than 10us and occur with a duty cycle of less than 0.1.

Unfortunately it does not say what would happen if the surge lasted for longer than this, say 1ms.

-It also doesn't say what would happen if a 2A surge went through the LEDs for say 10us ?

I asume the LEDs would be very badly damaged?

 

[FvM]

current ratings of led

Yes, it must be assumed. At least you should expect degradation of parameters.

 

[eem2am]

what is top of surge forward current

to demonstrate if i may,

here is the overcurrent in some Luxeon Rebel LEDs which are good in the datasheet for 360mA.

here the current goes up to 490mA OVER 500us as can be seen in green.

The blue waveform is the input voltage bouncing up and down between Vin_min and Vin_max.

It is not possible to know if this will severely reduce the LEDs life-time. There is no word in the datasheet for the 350mA ones.

https://www.philipslumileds.com/pdfs/DS56.pdf

Added after 10 minutes:

sorry , forgot...this is the circuit that causes the ripple.

it is 10W boost LED driver.

The resonant frequency of the output LC filter (72KHz) is excited when the input volts jumps upwards.

I cannot stop this as i need the output LC filter for EMC.

Also, since the bandwidth of a continuous mode boost is so inherently low, i cannot use compensation to avoid it, but can only reduce it , though not enough.

 

[FvM]

surge current rating

There are only few designs, that can tolerate high Q LC filters in power supply. This one apparently isn't among them, because it's intended to work with a pulsed supply voltage.

Without reducing the filter Q, you won't come far, I fear.

 

[eem2am]

hello,

The supply voltage isn't supposed to pulse, but unfortunatley it does so occasionally. -at least once every time it is on.

The degree of overcurrent is very dependent on the rise time of the input voltage step as you will know.

and i am wondering if the subsequent LED surge current warrants extra mitigation circuitry such as fee-forward etc ?