I am totally confused.

Yesterday I put 3 x 3 Watt LEDs in series with the output of the LED driver LDD-H 300. The Imax of the LED's is 700mA. Using a 12 Volt Battery which is charged to 13.8 Volts I left the circuit on for 16 Hours with no problem.

I switched it off and about 5 hours later I went to switch it back on and the LED's would not come on. I disconnected the LEDs from the output and tested the voltage and there is no voltage.

From the datasheet it shows it has short circuit protection and over temperature protection. I left the unit off for 40 minutes then without the LED's connected switched it back on.

I don't understand how this has happened. Was I supposed to add additional protection like a fuse or an MOV across the Input. I would really like to know before I bin this driver.

 

Please find attached the datasheet.

I see on the datasheet it says do not put the input onto the output, is it advisable to fit a Diode to Prevent this Happening?

 

And did you have sufficient heatsinks?
Are any of the leds shorted now?
Did you measure the maximum junction temp of the LEDs during operation?

schematic of your circuit?
specs of LED?
rating of battery?
measured battery voltage after 5 hours?

"high power" LEDs require proper knowledge to use.

Its very possible that the battery voltage has dropped below the combined Vf of the LEDs and now its not high enough to work.

example.. if the Vf of each led is 3V (so 3 in series is 9V) if your battery is now drained below 9V it won't work.

 

And did you have sufficient heatsinks?
Are any of the leds shorted now?
Did you measure the maximum junction temp of the LEDs during operation?

schematic of your circuit?
specs of LED?
rating of battery?
measured battery voltage after 5 hours?

"high power" LEDs require proper knowledge to use.

Its very possible that the battery voltage has dropped below the combined Vf of the LEDs and now its not high enough to work.

example.. if the Vf of each led is 3V (so 3 in series is 9V) if your battery is now drained below 9V it won't work.

Today has been a comedy of errors and failures. The LDD-H300 failed to work and the earliest I can get another one is Wednesday next week. However when I read this post I realise I have a lot to learn about "High power LED's"

I connected a 10R 10 Watt resistor in series and recorded the results as shown in the attached. This worked but was very dull. Having measured the current and the total being 150mA I realised that by reducing the resistance the intensity would improve as higher current would flow in the circuit.

Disaster struck, the heat sink got to 100°C very quickly I had reduced the resistor to 3k9 5 watt ceramic. I switched off and put a fan blowing onto the aluminium heat sink. once cooled off I switched on the LED's again, they came on and started flashing on and off.

I Checked for dry joints but everything seems to be ok. So I have no idea what is going on.

I would like information on working with high power LED's

 

How do I work out what heat sink to use

 

How do I work out what heat sink to use

This should get you started..
http://sound.westhost.com/heatsinks.htm

 

Information on the Heat sinks is comprehensive, easy to read well written and VERY informative, several times is needed to read to absorb all the information.

 

Hello,

On that site there is also a page that descibes how to build the heatsinks yourself:
http://sound.westhost.com/articles/diy-heatsink.htm

Bertus