I was curious how they implemented a 220W variable output e-cigarette. 

For me the most important thing was to see what actually drives the coil and how the internals of the power circuitry were designed.

As always I made a YouTube video about this project. You can either check that out or simply continue reading :)

But lets first take a look at todays subject:

It is a Smok Alien 220W Kit (product page).

As you might (or might not) know, this product is driven by two 18650 cells. They're connected in series so the device has about 8 volts to play with. (8 volts also keeps down the amperage when dealing with 220 watts)

The logic stuff mainly consists of an ARM Cortex M0 from Nuvoton as the main MCU, a 0.95" OLED display and a couple of transistors, small mosfets and a boost converter (probably for charging).

Under the heatsink we have a synchronous buck converter made out of two "N-Channel Enhancement Mode" mosfets which are directly connected to a buck converter driver. 
As a feedback for regulating the output they installed a shunt resistor with a current sense amplifier which is connected to one of the analog inputs of the MCU.