Super bright LEDs

[Bitsyncmaster]

Super bright is making some of there LEDs with capacitors on the circuit. You will see black cylinders on the back of the circuit board, those are the capacitors.

These will cause problems if used in the dome lights with my dome light unit. My dome light unit uses PWM to dim the dome lights and any capacitance or inductance on that circuit will prevent it from working properly.

They probably would also mess up the function of the unit if used in any of the light circuit. That is because I sample the light circuit current by switching the power on and off very quickly

[Tillsy]

Aw sh#t - all the LEDs I've already fitted, and those I am waiting to install via the dome light unit I was seconds away from ordering from you, are Super Bright LEDs. I have just quickly checked and, yep, they have the (non-flux variety) capacitors onboard...

http://dmctalk.org/attachment.php?attachmentid=14099&d=1350300144

[Tillsy]

Nevermind, I just ripped out the dome light module and the LEDs don't seem to be causing anymore problems - just no delayed lighting. Will deal with that later!

[RIUM+]

I don't know what their circuit layout is like, but wouldn't you be able to theoretically just snip off the capacitors to restore the old functionality without causing any harm? I assume they were added for protection against random voltage spikes & high-frequency noise reducing the LEDs lifespan. A DeLorean's not exactly the cleanest electrical system, but it's not THAT bad.

[Bitsyncmaster]

I don't know what their circuit layout is like, but wouldn't you be able to theoretically just snip off the capacitors to restore the old functionality without causing any harm? I assume they were added for protection against random voltage spikes & high-frequency noise reducing the LEDs lifespan. A DeLorean's not exactly the cleanest electrical system, but it's not THAT bad.

My guess is they are using the capacitors to filter noise and prevent there constant current circuit from blowing and LEDs from blowing out. So as long as the lights don't also drive motors and such you should be able to just cut off the capacitors.

They must know that circuit will not work with PWM dimming on any car. They should have used a zener diode rather than capacitor to protect the circuit. It looks like it was an after thought (adding those caps).

Let us know if you cut off the caps and how they work.

[Bitsyncmaster]

I'm placing an order for a few of these new LED bulbs. I will look at the circuit and confirm if you can just cut off the capacitors.

Looks like the old type are the ones with the plastic tube.

[Bitsyncmaster]

Just got the LEDs in the mail. It looks like they are using a switching type power supply. That would be great for efficiency but not good for my dome light unit.

I will have to draw up a schematic to see what they are doing.

Don't cut any components off your boards. It would probably stop working.

[Bitsyncmaster]

The Super Bright LEDs (high brightness) units are using a switching PMIC LED driver. I attached the spec sheet on the driver IC.

The two black cylinders soldered to the back of the board are one inductor and one capacitor (4.7 uf 50 volt). You can defiantly cut that capacitor off and it should help with a better dimming time. But there is another capacitor in parallel with that 4.7 uf which is an SMT 1.0 uf cap. I removed both caps and the LED still seems to work fine but removing the SMT part takes two soldering irons or solder wick.

The reason they use this in place of a current setting resistor is to save power and maintain a constant current in the LEDs. So you get the same LED power at 12 volts or 15 volts. I use a different type of constant current circuit which uses no capacitors. The switching constant current circuit is more efficient but will not work with my dome light dimming because of the capacitance. It may or may not confuse my unit if your using these LED in other (non-dome) lights.

Pleas post your results if you remove that 4.7 uf capacitor.

[Bitsyncmaster]

What super bright should have done to their new LEDs was add two more resistors to the control pin on the IC. Then when the input voltage fall below a set voltage, the LED turns fully off. That would restore the PWM capability. I bet Super bright is getting complaints with PWM dimming on these new LEDs since they also sell PWM units.

Maybe they will end up installing those resistors on new units. I guess you could install them but I will have to test it out myself.

[Tillsy]

I guess you could install them but I will have to test it out myself.

I was about to say just that :)

Let us know how you go

[Bitsyncmaster]

I added the two resistors on one of the new Super Bright LEDs and ran it on my test bench. Does not work because my PWM frequency is running a 4 KHz and that switching constant current driver Super Bright is using needs 500 Hz or slower frequency. Adding the resistors would take a lot of skill since you need to solder to that micro pitch surface mount IC. If Super Bright ever incorporates that change, I can change the software in new dome units to run at 500 Hz.

I tried another new Super Bright LED with the 4.7 uf cap removed and it still did not dim correctly. I then removed the second surface mount capacitor and it dims pretty good but not as smooth as a normal LED works. Again that is because I'm running my PWM frequency too high for that component.

[Bitsyncmaster]

I did a lot of testing and you can not use those new LEDs with the switching mode constant current circuit. Those are any of the ones with those two black cylinders on the back of board.

I can not detect when those lights are drawing power with my current dome light unit. It's the way I'm testing for power draw by turning the circuit off very quickly so the eye does not see any flashing. If I were to design a new dome unit, I would detect the power differently but even doing that, you could not PWM the dome lights with the new LEDs.

If you try to use them, the unit will not keep powered if only one of those LEDs is turned on.