LED drivers and Accessories you want, but don’t exist

Looking for Emisar D1 firmware, simple 3-4 modes, temperature controled

Really good thread about loneoceans’ new driver: [ GXB172 - 50W Single Cell 17mm Boost Driver! ]

This driver has many similarities compared to the driver I’m currently developing (with the help of some others).

I have another wish:
A compact boost driver for COB LEDs in the 30-40V range with all the usual features of flashlight drivers.

I found a nice calculation for MOSFET losses

We’re seeing more and more low-Vf 3V LEDs out there. Luxeon MZ, quad E21, Q8WP to name a few. These lose a lot of efficiency when driven linearly and could benefit from some good buck driver for 1s out and either 1-2s in. Or simply 1s in, that would be enough.

So literally just a 7135 driver?

The AMC7135 is a linear regulator.
Agro wants a real 1S buck regulator (with an inductor) like many production flashlights have. This improves efficiency (runtime) when the voltage difference between the LED and the battery gets larger.

Yes, that’s precisely what I want.
Q8WP driven to 1.25 A does ~124 lm/W with Vf of 3V.
Drive it linearly and you get about 96 lm/W throughout battery discharge.
Buck it with 95% efficiency and end-up with 118 lm/W.

next monday placing an order in my board fab

next monday placing an order in my board fab

That calculation is not correct, correct calculation is:

Linear drive efficiency with fresh battery: n1=Vf/Umax=3/4.2=71.43%

Linear drive efficiency with empty battery: n2=Vf/Umin=3/3=~100%

Because discharge curve for typ. li-ions is fairly linear. no integration over time is needed to get average efficiency, it's simply average of n1 and n2 calculated above.

So, average efficiency of linear driver when driving LED with Vf=3V from 4.2V down to 3V is (71.43+100)/2=85,71%, and that means overall flashlight efficiency is 124lm/W*85,71%/100= 106,3lm/W.

Not as good as 95% efficient buck driver, but not that bad as some think. 1.25A is relatively low current these days,at higher currents efficiency of buck driver becomes similar to linear driver,but due to much higher internal resistances, buck driver will be in "out of regulation mode" sooner than linear driver, so there is almost no advantage at high current 1S setups.

That calculation is not correct, correct calculation is:

Linear drive efficiency with fresh battery: n1=Vf/Umax=3/4.2=71.43%

Linear drive efficiency with empty battery: n2=Vf/Umin=3/3=~100%

Because discharge curve for typ. li-ions is fairly linear. no integration over time is needed to get average efficiency, it's simply average of n1 and n2 calculated above.

So, average efficiency of linear driver when driving LED with Vf=3V from 4.2V down to 3V is (71.43+100)/2=85,71%, and that means overall flashlight efficiency is 124lm/W*85,71%/100= 106,3lm/W.

Not as good as 95% efficient buck driver, but not that bad as some think. 1.25A is relatively low current these days,at higher currents efficiency of buck driver becomes similar to linear driver,but due to much higher internal resistances, buck driver will be in "out of regulation mode" sooner than linear driver, so there is almost no advantage at high current 1S setups.

Let's @#$%ing face it: bearing in mind implied contact losses (and even if don't) the useful voltage window of li-ion cells overlaps operational emitter voltage windows. A multi-purpose 1S/1S driver should be able to accept input voltages from 2.5V, offering regulated output up to at least 3.8V. This means buck and boost.

And another thing: PWM is bad. Since little to no one complains, there's no @#$%ing care about. The usual high frequency (4+KHz) switching of 7135's is the last straw, it causes lower efficiency and much earlier loss of regulation. A proper LC filter at the output of linear regulators can fix these issues, providing proper stable DC to the emitter and doing away with the need to switch on/off faster than our poor 7135s can tolerate. This means an inductor in series with the emitter is required. Can someone bear with me and do some inductor calculations for 1 to 2KHz 7135 PWM frequency? Is this too low frequency to smooth out?

Cheers :-)

I did something wrong, your calculations look correct. Yes, at higher current the difference would be lower.

Either way, when I see that a different driver enables 5% higher sustained performance and 5-10% better runtime (depending on mode), I stop seeing the less efficient one as a top choice.

Agree, buck-boost would be even more awesome.

Shocki, Lexel, have you considered porting support for the external thermal sensor from GXB172?

It is possible to add external thermal support, but someone needs to write the firmware for it.

For those still waiting for the 17mm boost driver, I’m still working on it. It will look pretty similar to the one made by loneoceans.
But I still have problems with it, and need to solve them.

Looking for one side driver with fet only and original nanjg 105 firmware (stars option)

hello
where i can buy 12v booster driver to install xhp35 in my convoy s2+ ?

@Carrygun, you can’t for now. You will have to wait until 17mm boost converters are available.

it is possible to install xhp35 in s2+ in any way ? may be 20mm it is possible to “fit” ?