With the widely available DC-DC boost ready built modules based on MT3608 chip can I control it by adding the N-ch MOSFET to the Vin- line like this:
The module itself are pretty reference in design similar to this:
Module load are COB LED +12V light. +Vbat are Li-Ion power which also powers the MCU through 3.3V LDO and I want to enable/disable module & LED from MCU.
PS: I know the DC-DC IC has the ENABLE pin, but it's hard wired to the Vin+ on board and I don't want to deal with cutting traces.
I'm also aware it's possible to control LED by adding MOSFET to the LED GND line but this way the module will be always powered up and I want to save battery power by turning it off completely when not used.
Best Answer
Yes, it should work. But...
Note that your LEDs "GND" will not be the same as the GND of the rest of your ciruit, it will have an offset equal to, $$V_{DS} = R_{DS_{(ON)}} \cdot I_{DS}$$
Thus, a slightly "cleaner" way of doing this would be to have a P-channel MOSFET acting as a high-side switch. This would keep all GND the same and will save you some headaches. If you are not confortable driving the P-MOS directly (if the Vbat is to high for your MCU) you can use a circuit as shown bellow, where another transistor (N-channel) is used to drive the P-MOS. I did not chose the transistor carefully, don't pick the same (please find some that have Vgs compatible with your application).
simulate this circuit – Schematic created using CircuitLab