Diy led driver. DC to DC converter.

[Leslie]

Design based on the LM2576HV.

Components.

LM2576HV 5 pin simple switcher IC. Data sheet<<<<
Hand wound 1650uh inductor.

1,2k series metal resistors feedback divider from ground.

10.54k series metal resistors, in series with 5k variable resistor with 1.4k parallel resistor = 1.2k. 10.54k to 11.7k total feedback divider from output.

100uf input filter capacitor

25v 2200uf capacitor output filter capacitor.

Heatsink.

Hand drawn diy etched circuit board.





Specs:
Input:  Tested on  48v and 36v packs.  OK

Output:12v to 13.2v adjustable.

500ma to 750ma efficient regulation.

75% to 85% efficiency.  Unconfirmed but it runs very cool.  Just above ambient temperatures.

Switching speed 52khz

I can make these regulate 60v to 3v however I want to run these on 12v auto leds and any and all 12v products, If you rewind the inductor with heavier gauge enamel copper and less turns you can draw 3 amps out of the lm2976hv chip.  I wanted efficiency in the 500ma range.

These chips can also be used as drivers for fets for higher voltages and much higher currents.
 

[Leslie]

1st test.

Running a 12v CFL and a 12v red auto led lamp drew 110ma from 50v input and output 12.25v 350ma

50v @ .110ma = 5.5 watts
12.25v @ 350ma = 4.28 watts

5.5 watts - 4.28 watts = 1.22 loss
 
Loss = 1.22 watts over 50v @5.5 watts DC to DC conversion.


Origin voltage percentage figure = 100% / 5.5 watts =18.18

loss = 1.2 watts X 18.18 = 21% loss = 81% efficiency.

Led driver = 81% efficiency.

I designed the 1650uh inductor as close to 500ma efficiency as I used the datasheet formula at based on 12.5v output, so when I load this driver up with more current with higher voltages to boot. we should see an improvement up to 550ma and efficiency should start to drop at 600ma and losses acceptable up to 750ma.

Most of the mechanics in this area are working in my head and am working on a better formula based on the inductor core fux densities permeability and dimensions.

I really think I could squeeze 90% efficiency.



 

[Leslie]

I designed a light.  The auto led lights were going to set me back $60 and found these little 24 led torches for $6AUD dollars each in the bargain shop.



I bought 4 of them so Im boasting 96 leds working 24p 4s and shes pretty bright. I dialed up the switcher to 12.5v under load this gave me 3.1v on each led drawing 280ma this is 3.5 watts.

I tested the driver at 24v, 36v, and 48v and the lumen output was identical at these three voltages.  This thing even works when the pack is at full charge on the charger at 60v.   

Even better I am looking into a 75v switcher for 60v, 48v, 36v and 24v regulation.

Hmmm maybe another time.

I will provide some pics later.  A bit tired to do the photo shoot just now.