A while back I remember seeing an SP70 on their Aliexpress store that was labeled as “BLF” but it was just the standard SP70 with the Sofirn 6 mode/ramping UI. I don’t see it on there anymore though.
Ok, my pictures of the driver are better than Sofirn's:
This is a classic FET design. Using the top pic as a reference, the large part on the left is a FET, one we are familiar with in fact. The bottom right pin of the FET is the FET gate, and you can see connected to that the 2 standard resistors our designs use for the FET gate - one is a low value inline, the other is a high resistor value going to ground.
The 5 leg part on the right is an LDO, to bring down the voltage to ~4V to run the MCU. The 3 leg part on the bottom appears to be another FET for lower power, but it appears to be not used, not connected to the MCU - I'm not sure, would have to trace the circuit myself.
I've seen these kind of dual FET, one hi power - one low power, driver designs before. In fact the Haikelite HK04 is very similar:
This uses 2 high power FET's instead of 1, and the part labeled Q7 near the FET's is the low power FET channel.
It’s connected. Look at pin 7 next to the “F1” on the MCU.
The small FET top pin looks to be ground get power through R2. Maybe that’s how they limit output? It’s not very robust looking (R2) so it must only handle very low output levels.
Then the bottom right pin looks to be hot grounded from the vias. (Logical guess) We need a picture of the backside to confirm.
Texas_Ace built a twin FET driver for the Haikelite MT09R. The smaller FET used a whole bank of resistors to limit output. It controlled thousands of lumens. This Sofirn small FET channel looks to control a couple lumen hundred at most.