Review/Test of 17mm 2-Mode LED Driver Circuit Board for Flashlight DIY






Driver is from Fasttech.com

Official specifications:

• Product Type: Flashlight Driver
• Constant Current: Yes
• Driver Type: Direct drive
• Input Voltage: 3-4.2 -volt
• Flashlight Modes: Hi > Lo
• Mode Count: 2
• Depth: 3 mm
• Diameter: 17 mm
• Product Weight: 0.7 g
• Suitable for single lithium battery
• Great for DIY project or repairing your flashlight
• Battery over-discharge protection kicks in (cuts off power) when input voltage drops to 3V to 3.1V

Measurements

Tested with: Cree XM-L2
Diameter: 17mm
Height: 3mm
Modes: Low, High
Driver changes mode with each turn on.
Low is with pwm at 207Hz and 17% duty cycle.
Driver is direct drive.
DC resistance in driver is about 0.18 ohm at 2A (Measured directly at the driver pcb).



High



This driver is only a direct drive driver, i.e. it is only a switch with a bit of resistance in. This means that the input and led current is the same (The curves are on top of each other) and the voltage/current curve will be very close to the led voltage/current curve.
I did not test higher than 3.9 volt, because the led is specified for 3A and I passed that at 3.9 volt (Most LiIon batteries will be below 3.9 volt when loaded with 3A. See my comparator for actual data).
I cannot see any traces of a low voltage protection, but the led by itself will to a large degree protect the battery.






Starting from a low voltage, shows that the driver starts at around 2.9 volt.







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



Low

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 actual pwm frequency is about 207 Hz (The dip in the pulses is due to my power supply, not the driver).



Conclusion

This is a simple driver with limited applications, i.e. only LiIon batteries and led must be suitable for direct drive.
I wonder why the driver has two IC's, it is probably a microprocessor and a EEPROM (For remembering mode), but why use an external EEPROM when most microprocessors has one build in.



Notes

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