The F_Tech Driver. Geeky stuff.
The driver circuit is most easily understood if considered as being composed of two separate modules, the high efficiency buck driver and the analogue controller. The driver is based on a chip that accepts an analogue voltage signal to control brightness, rather than the usual Pulse Width Modulation (PWM). If the latter needs explanation, you can read all about it in Wiki. Biggest problem with off the shelf and cheaper drivers is falling output as the battery goes down, and also poor efficiency at lower brightness levels. This is basically what you can expect to get in most Chinese torches and headtorches. So how bad are the poor ones? I could say but would probably be disbelieved! At lowest outputs the eastern product is as bad as 68% efficiency, however I cant make a direct comparison as mine does not have an equivalent output, but standard mode on mine of 200mA runs on average 85% efficient, high mode averages about 95% efficiency.
The driver circuit is not complicated, basically typical buck circuit except the chip, a DC-DC converter has its own internal switching MOSFET and is one of most efficient designs. It has a base heat sink solder mount for which I fabricate a special copper mounting and assemble my PCB around it. It also has an over temperature shut down and on testing this (obviously full power use only causes the necessity); the output will go into a slow strobe. It’s unlikely a user will ever see this as my heatsinking is so efficient. This is entirely due to the rapid rise and fall in temperature causing ON/OFF switching, it’s not a digital function, its all analogue. Strobes and flashes etc are usually part of a firmware program.
The key to its operation is the 4 mode analogue controller of my own design which as an assembly gives a very consistent, efficient, and completely flicker free output on all brightness levels, and the consistency of output to the point where voltage in falls to the voltage of the LED array is very consistent and smacks of a boost driver although it is not. In effect, there is no falling off of output down to where the lamp powers down to “slow death” mode, bar the Turbo made. And that is sustainable for most of the battery life.
The lamp itself, the Ultra12, is similar in appearance to my old X8, the two vertical reflectors with a bare emitter each side, this suggests an 8V input, but its not, it’s a 12v model. The two bare emitters are parallel wired and then serial wired to the 2 serial emitters behind the reflectors. There are indicator LEDs mounted each side of the reflector, described later. The placement of the bare emitters gives a better external appearance as well as sharing the power and the subsequent heat generated between both sides of the lamp. This one will never burn out a flood, the weak point on many lamps.
The lamp is actuated by a double throw momentary toggle switch mounted on the same side of the lamp as the cable gland. It does look rather good as well as being extremely user friendly. Flicking down is ON/OFF, up is mode cycle through the 4 modes. Flicking up with lamp off enables the 4 blue LED battery meter, it works with it on but advised to use it lamp off.
Connecting the battery enables a bright green Gallium Nitride emitter pilot light. These are very efficient at low current and underground testing has confirmed that one can easily see ones feet; this would still operate in the event of failure of the main electronics.
The lamp shuts down at approx 9.5V (Adjustable) to a ‘slow death mode’ at which point the green pilot will go out and be replaced by a flashing red LED. The main output is now generated by a separate simple linear driver. These are not very efficient as current in = current out, the access voltage being burned off as heat. However the low battery voltage overhead over the LED array is so small that we are still hitting about 90% efficiency. Current at 9.5V is about 30mA falling to about 10 at battery shut down. Obviously, when the battery finally shuts down you will of course loose all light even the green pilot, this is true of all lamps as Li Ion cells cannot be run flat. The Slow Death Mode burn time is hours and hours, I tested for 5 hours and then lost interest.
The maximum output is slightly less than the lamp it replaces; however this one has a consistent output so the output rating is practical rather than theoretical. The old would output more than 3500 lumens, but on fresh charged battery, so it would fall off. This one outputs slightly less, but note the floods are running more efficiently due to power being shared by two rather than one, so this will output probably more flood light than the old, and of course it’s sustainable. Roundabouts and swings.
The old X12 had 6 output levels from two separate drivers; however the bottom 2 were in truth virtually useless, these are replaced by 4 in the new version. I would really have liked to get the lowest down a bit more but this was not possible without loosing more at the top, but even if it were possible it would then not have given the kind of slow death that I wanted. As the new lamp stands though, it really does offer the best of both worlds. It is also a good example of how my thinking on most things is outside of the normal box.
If the lamp is on Turbo made when the battery is low this obviously causes a voltage drop because of the load, if it drops to the setting of 9.5V the lamp will shut down to Slow Death mode, however the battery will recover and then the lamp will then automatically return to Standard Mode. It would then be best to keep to that setting to prolong battery life.
The new lamp has virtually nothing sourced from the Far East; all electronic and major components are from major western manufacturers. All the electronics are my own design, bar the main driver circuit which is based on the manufacturer’s data sheet ‘typical application’ schematic.