Driver regulation question

Flashlight Modding and DIY Parts
1

Hello everyone. Just a technical question that I hope one of the experts out there could answer quickly. Will driver regulation show during a tailcap measure? I’m assuming no as the regulation is done at the driver end? That and my JM07 that’s supposed to be regulated reads 1.2A with a depleted King Kong at 3.7v. (2.44A at 4.2v).

2

if it linear regulator, tailcap current = LED drive current

3

I'm no expert, but I think a tailcap measurement will show higher amperage at lower voltage in order for a regulated driver to keep the current within regulation. A true expert should chime in though.

-Garry

4

Thanks for the responses. The JM07 has the nanj 105c with 7 chips, I really don’t know a great deal about the different kinds of drivers out there. So does this mean my JM07 isn’t regulated if I’m getting a lower tailcap draw as voltage decreases?

5

The 105c is regulated, but only on high I believe.

-Garry

6

Thanks Horst, I think you answered my question. I had the impression from somewhere that under current regulation the driver would increase current as voltage decreases to meet a minimum current requirement, but this is probably only the case for certain drivers and not the nanj. Makes sense now…

7

A boost driver will draw more current as battery voltage decreases. A buck driver will draw less current from the battery than it supplies to the led by transforming excess voltage to current. Linear drivers like 105C waste excess voltage as heat and go direct drive when battery voltage drops to emitter Vf.

8

Linear Driver
Voltage: Input Must be higher than output for regulation to occur
Current: In all cases, Input Current (from battery) will equal output current (to LED)

Boost Driver
Voltage: Input voltage must be lower than output voltage for regulation to occur
Current: Input current must be higher than output current

Buck Driver
Voltage: Input voltage must be higher than output voltage for regulation to occur
Current: Input current must be lower than output current

Buck/Boost Driver
If input voltage is less than output voltage, then input current must be greater than output current
If input voltage is greater than output voltage, then input current must be less than output current
If input voltage is equal to output voltage then input current must be equal to output current

These statements all assume a 100% efficient driver (which will NEVER be possible), but they still hold true for generalized purposes.