I was reading a bit from the excellent Ralim blog about the TS100 PCB design. There I met something I do not fully understand:
The output drive for the iron tip is run through a capacitor, then to a NPN transistor that switches the P MOSFET’s on/off to allow power to run through to the heating element directly from the DC IN. This is of note as it means that should the output be left HIGH or LOW the iron tip will be off, preventing any software errors from causing damage.
Can someone explain this to me? I am not sure what the circuit actually looks like from this description. Is this a common way to design a safe power controlling circuit? (It sounds like it based on the tone of the writing.)