Thanks for a great reply, George. The design and thinking of your product ranges is much clearer now.
Next, bFlex and nFlex use 1A rated switcher chips. So, bumping the output current spec to 1.4A is more than just tweaking something - it's a complete new redesign. Bigger switcher, bigger inductor, bigger diodes, bigger board, bigger cost.
Next, MOST switcher chips that can fit on a small board, typically max out at around 1A - just a fact of life. Factor in efficiency of the switcher chip, junction temperature and dissipating capability of the IC package and there's a good reason you don't see 1.4A or 2A or ... switcher chips that are fully integrated and conventional SOIC packages.
This is what I had expected, that the 1A rating was not just because that's the datasheet limit for lots of popular LEDs, but because of hardware design limitations. However, don't the nightlightning lights from NZ use your bFlex board with their own UI, and they can drive 1.2A from it? MaxFlex drives at 1.2A also, but it's a different circuit. Not as though 1.2A is any kind of worthy increase from 1A.
Answering one post - show me a DX driver that is a SWITCHER that is capable of 1.4A... All the ones I've seen are essentially linear regulators. All they do is stack more & more regulators in parallel.
Yes, totally true. They're not $3 just because they're from China, they're $3 because they're poorly designed, inefficient, probably use substandard components, etc. TaskLED circuits are far better quality in addition to having a far better UI.
You can't parallel a driver like maxFlex or bFlex/nFlex etc at the LEDs - the way they current regulate doesn't lend to that. If you want more current, then you need a different design.
I'm not sure what you mean here. I have 4 Crees running in 2S2P on my bFlex, giving a Vf of ~7.4 and each getting half the current (500mA max) and in an email I asked if that was a good idea, and you said sure, it's fine, they'll just each get half the current the driver provides, and you should make sure the 2 strings have as similar a Vf as possible so one LED isn't much brighter than the others. Now you appear to be saying that I can't do that - are you saying something else here?
Yes, to get more current (than 500mA each with 2 in parallel) you need a different design - like your master/slave bFlexes! (Which are not yet available, right?) I was pretty excited to hear that they can do that; it means I could drive my 4 Crees at full 1000mA each with only 11.1V from the batteries, if I wanted to buy 2 bFlexes. For me, the small brightness increase is not worth the money and battery drain, but it's still a pretty cool idea.
Finally, there are LEDs that take several amps (multidie units) - just because they exist doesn't mean nFlex/bFlex should be able to output several amps
Use my CCHIPO driver if you want to do that - see my website. That's what happens when you want more power - things get BIGGER and more EXPENSIVE...
Yes, it's true that xFlex should not automatically have to output whatever the highest amperage multi-die LEDs can take at the moment, given the hardware limitations. However, it does seem that you'd want to maximize what your hardware can do (which you are doing).
I hadn't looked at your CCHIPO in detail before - that's a really cool (and big, expensive) driver! It can take 5A input - what's its max amperage output?
Say in a year or 2, Cree brings the 4A single-die 1,000 lumen LED they've announced in their lab to the market, but at well over 100lm/W, and it becomes the new cool LED everyone here wants. If you wanted to design a driver for it, would it necessarily be as big and need such heatsinking as the CCHIPO? If so, is that necessarily the future of high-power LED lighting - big drivers that need considerable heatsinking? Or is there some other way? It seems that a 85% efficient driver, pumping 100W to the LED or an array of them, would need to dissipate 15W - that's alot!
Alex
