Yep! Complete discharge guide!
I don't want to repeat that was there previously anyway, so - links.
- Part 1 (how efficiency works while you charge an electromagnetic field)
- Part 2 (why discharge time matters and how it affects heat dissipation)
- Part 3 (that one was half-wrong, but heat dissipation part is likely to be true, read carefully)
- Part 4 (what affects discharge time)
This time I want to make a finishing pass on discharge topic. It looks like that:
In theoretical Part 4 we came to a conclusion, what voltage drop affects discharge time significantly. Must-read, but simplified - coil tries to produce constant current while discharging and it's a very easy task if voltage drop is minimal. One approach is to use a diode, however, 0.4V is pretty high. And that is where MOSFETs come to play, acting as a low-resistance load.
Zener diode in MOSFETs structure is very helpful, since it can handle current until FET opened completely.
That's why this process has 3 stages and not two.
For example, we have 1A of current, conductive channel provides 10mOhm, U = I*R, voltage drop using this method is only 0.01V, 40 times smaller than what we have on a diode! There is a room to play, in different conditions channel shows different resistances. That's what I've got with a random transistor as proof of concept: