Test/Review of 1~2* AA/AAA 5-Mode 800mA Linear Booster LED Flashlight Driver Circuit

1~2* AA/AAA 5-Mode 800mA Linear Booster LED Flashlight Driver Circuit




Driver is from Fasttech.com

Official specifications:

  • 0.9V~3.6V / 500mA@1.5V / 800mA@3.6V / 17mm
  • Constant Current: Yes
  • Driver Type: Boost driver and Linear regulator
  • Input Voltage: 0.9~3.6 -volt
  • Output Current: 800 mA
  • PCB Height (w/o Components): 1.5 mm
  • Reverse Polarity Protection : No
  • Flashlight Modes: Hi > Mid > Lo > Strobe > SOS
  • Mode Count: 5
  • Mode Memory: No
  • Depth: 2 mm
  • Diameter: 17 mm
  • Product Weight: 1.1 g
  • Booster driver mode when input voltage is 1.5V or less
  • Linear regular (constant current) mode when voltage is between 1.8V and 3.6V
  • Rated at 500mA current output @ 1.5V input
  • Rated at 800mA current output @ 3.6V input





Measurements

Tested with: Cree XP-G2
Driver diameter 16.8mm
Driver height 5mm
The driver uses boost mode and will be forced into direct drive when voltage is to high.
The driver has high, medium, low, strobe and sos.
Driver diameter 16.8mm
Driver height 5mm
No memory, always starts in high.
A short off/on will select next mode.
Medium pwm 550Hz with 40% duty cycle
Low pwm 560Hz with 15% duty cycle
Strobe 7.6Hz with 50% duty cycle



High



Below 1.5 volt the driver will try to draw a constant current from the battery.
When 1.5 volt is reached the brightness is stabilized, until the voltage reaches Vf of the led.
Above Vf of the led the driver will be in direct drive mode.



At low voltage the efficiency is low (as always) and a lot of power is lost in the driver.
When the driver stabilizes its output, the power loss goes down, as the current goes down.






Starting from 0 volt, the driver turns on at 0.75 volt.








In high mode there is no pwm in the light and only a small amount of high frequency noise.



Medium



Because the driver uses pwm, the shape of this curve looks very much like high mode (With pwm the led is driven at full power, but not all the time).







Pwm is at 550Hz.



Low



Low mode is also the same, but at even lower currents.







Pwm is at around 560Hz.



Strobe




Strobe is at 7.6 Hz. Brightness is at full.


SOS




Brightness is at full.



Conclusion

The driver looks like a good driver for one or two NiMH batteries or a CR123 battery, but cannot safely be used with LiIon.
With one NiMH battery the voltage will be too low to stabilize brightness.
With a maximum current draw of about 2A it is not really a good driver for alkaline batteries.



Notes

How do I test a led driver
List of all tested drivers

Would these be ok with the new 3v LiFePO4

LeFePO4 is not 3 volt, but about 3.2 volt during the full discharge (Using small cells at high currents will give lower voltage).

That will work, but you are at the start of the direct drive phase.

Very similar to this I believe?

Yes, but not the same: http://lygte-info.dk/review/DriverTest%20Nanjg110%20UK.html

Thank you for the review!

Ah nice! Didn’t see that review.

What is meant by “direct drive phase”? Is that the spike in current after 3.25V input (unregulated range?)?

Thanks.

Yes, the current basically runs straight through the driver and through the led with only some (small) circuit resistance to limit it.

Thanks for your reviews HKJ. Very useful and scientific approach. A graph is much better than many lines of explanations. :slight_smile:
I really like your website too but it’s too bad that we can’t post comments.
Keep them coming please! :slight_smile:

Most of my test and articles you can find here on BLF, where it is possible to post comments. Opening up for comments would require that I used a lot of time on filtering spam and general maintains.

You can also use email or PM (from BLF) for specific questions, usual I do answer (But please, do not ask what is the best xxx, usual there is no best, because it depends on what you require).

Nice review thanks.

Looks like the current set resistor in the test driver is 0.15ohm ,which by the datasheet (pam2803) sets the maximum current to 633mA.The drivers I got from Fasttech few weeks ago have 0.12ohm resistors,this sets the current to 792mA,close to the promised 800mA.

I used this to replace a single mode driver in a 2 AA flashlight.First mode memory is superb.