No , please read carefully what I said !...,Quote : " 5 minutes time ,soldered in place on top of the components , secured with thermal adhesive , resistor mod .., and I got 3.2 Amps to led , After 20 minutes in run , the inductor was just slightly warm ". As you can see , I said "resistor mod" !!!
I was looking on my papers ( I always write down what I'm doing , to be able to compare.., sometimes the memory is playing tricks (!) , and, for the driver I was talking about , was the following :
Original Driver : Led Current =1.85 A.
Inductor changed : Led Current =2.12 A(!). Same layout , diode was a SS54 , transistor 3400L , R limit=0.22.
Added a 0.22 resistor , parallel , Current=3.21 A !
You could ask why the current didn't double ? This is happening all the times , doesn't matter what driver you are modding . Is due to the resistance of the traces ,wires , Rds on of FET , all of these resistances will generate a bigger voltage drops on them...
It is logic that , in a system with a lower resistance in the load path to get higher currents.., a lot of people will say : " WTF, we are talking about constant current drivers..." , yes , is true , but WHICH is the start value of constant current ? This is the question that should be the ONE!
Please, do not think that I'm patronizing you , myself I'm learning every day , the things are changing so fast these days...So I'm giving you a link for a very simple explanation of buck drivers , go to page 2 , :Buck Converters
About the diodes that you ordered , those with 0.16 V drop , I think that they are going to work , your voltage in circuit is 8.4 V and this diode is working like this :
When the FET is in state ON, the diode is not existing in the circuit , because it is reversed biased ,the inductor is charging and limit the rush current thru LED.
When the FET is going in OFF state, the energy stored in inductor will go thru LED , thru diode ( that is gone be direct biased) ,back to inductor , in a loop.
If the inductor are able to store more energy , than the led could use , at the next state ON of FET , the current will not start to accumulate from zero , but from a value bigger than zero. This mode is called "continuous mode" , because the current is never going to zero, between the cicles ON-OFF.
So , the diode is seeing the maximum voltage from the LED ( in reverse bias) ,but the whole current that rushes thru circuit, in direct bias .Therefore , low Vf at big currents will be translated in low power loss in circuit.
Somehow, this thread seems to have only 2 players.., what is happening here , on BLF ,the people are not interested ,or just waiting to see the results ?
Wake up, Guys !!!!
