Noname Flashlight Chinese Quality

Following up to the previous page I did some testing as to the inner workings of the converter. And maybe to beef it up, as the brightness of the Luxeon Star is a bit weakish... Removing the coil (after opening the flashlight again) I could figure out the schematic of the converter. It's a blocking oscillator, a NPN transistor switching on a current in a coil (0.47 mH), and a PNP one swithing the NPN off so the current that wants to continue in the coil due to the magnetic energy stored in it has no other route but through the Luxeon. A similar oscillator can be built with a transformer instead of a transistor, but the latter is cheaper. Also, as can be seen in the second closeup, the Chinese actually mounted two transistors on top of each other, lowering the impedance. While for the NPN it's a good idea it is really silly for the PNP.

As can be seen in the scope display shot, the horizontal axis being 5 µs and the vertical axis 0.5 V, the LED voltage is nicely 3.4 volts. Note that the voltage rises when the transistor conducts, this is because the current in the coil increases linearly and the impedance of the transistor starts to have an impact. The component analyzer confirms this, as the coil resistance is only 1.5 ohms. The transistor types are unknown as I couldn't find the SMD markings. Probably a modern Chinese version of BC847/857 type transistors. Beefing up the converter would be a matter of changing the switching transistor and increasing the base current to get more energy in the coil, but I haven't looked into that. Maybe later...

A propos Noname: the brand is actually called "Super Tiger", touted as a "3 Watt Luxeon LED Flashligth" (sic), features being (amongst others): SUPER high intensity fixed light beam, Double Anodize (sic), Water and shock resistant. So you know... (should have scanned it for the sixth piccie!).

closeup_coil	closeup_coilless	conv_schematic
scope	inductance