17mm 5-Mode LED Driver Circuit Board for Flashlight DIY

Flashlight Modding and DIY Parts
1

17mm 5-Mode LED Driver Circuit Board for Flashlight DIY




Driver is from Fasttech.com.

Official specifications

  • Constant Current: Yes
  • Driver Type: Linear regulator
  • Input Voltage: 3-4.2 -volt
  • Output Current: 800 mA
  • Flashlight Modes: Hi > Mid > Lo > Rapid > SOS
  • Mode Count: 5
  • Depth: 3 mm
  • Diameter: 17 mm
  • Product Weight: 0.7 g
  • Battery over-discharge protection kicks in (cuts off power) when input voltage drops to 3V to 3.1V





Measurements

Tested with: XM-L2
Driver uses direct drive
Diameter Ø17.3mm
Height 2.8mm
Modes: High, medium, low, strobe, sos
Driver does not remember modes, but always start in high.
A fast off/on will select next mode.
Medium uses pwm at 80Hz with 40% duty cycle.
Low uses pwm at 5.4kHz with 10% duty cycle.
Strobe is 9.8Hz with 50% duty cycle
DC resistance in driver is about 0.15 ohm at 2A (Measured directly at the driver pcb).



High



The driver uses direct drive, i.e. it only add an electronic switch and a small resistance in the current path.
This means that the battery and led current will be just about the same. Due to the small resistance the battery voltage has to be slightly higher than the led Vf.






The driver turns on at about 2.5 volt.






Being direct drive, the driver does not add any noise to the current.



Medium

The power and efficiency calculations does not work here, the efficiency will be very close to the high efficiency



The average current goes down when the led is switches on/off at a fast rate. The bump in the curve is due to the slow pwm.






The medium mode uses pwm at a very low frequency (80Hz). The dip in the pulses is due to my power supply, not the driver.



Low

The power and efficiency calculations does not work here, the efficiency will be very close to the high efficiency



In low mode the pwm is much faster.






The actual pwm frequency is 5.4kHz.


Strobe



Strobe is 9.8 Hz.



SOS





Conclusion

This is a driver with limited applications, i.e. only LiIon batteries and led must be suitable for direct drive.
The low pwm frequency in medium will mean that many people will see flickering from the light.



Notes

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

2

I wonder why the “800mA” in the specs. Avg based on voltage in is closer to 1.5A and logged over time should be even higher due to the flat discharge curve of lithium ion cells.