One of the questions of this design is how to run higher current LEDs. Keep in mind the design above is already running at 100mA per string.
Two ways to go about it:
- If multiple strings are needed, larger transistor drivers would be required.
- If one string is enough, an alternative is to use multiple transistors on the mirror.
As a simple test, I left the current resistors as above (so Q4 is running at about 90 mA), and combined used Q5 and Q6 and Q7 and Q8 collectors to drive a single string of high current LEDs. These are 8 White LEDs with a Vf of 3.2V which makes the total 19.3V and are running off a 24V power. About 6.8W total.
Here the result, multimeter measuring current through the LEDs.
Needless to say, the onboard regulator now needs a good heatsink.