Background: I am preparing for a full-time employment starting in May. I am coming from a computer engineering background so I only have some working knowledge regarding EE. The job duty is Firmware Engineer - I will be mostly dealing with writing firmware on a micro-controller for a switching-mode power supply board.
My question is: in digital power electronic, how does the PWM generated by the MCU get translated into a output voltage? By looking at the image below, I understand how the transformer, rectifier, and filter works. What I want to know is: what's going on with the waveform between the regulator and the load such that the output voltage becomes so smooth without noise, i.e. how the input waveform of the regulator get transformed into a straight line. Please explain in detail how the PWM, MOSFET, output Inductor, and output Capacitor are involved in this process.
I have done quite a lot of researches online learning power electronics by myself. However, I am experiencing a huge gap in between the digital world and the analog world (as a computer engineer, I only have experience with digital circuit). By looking at the picture of a digital power regulator below, I know that the MCU is responsible for generating a PWM to switch On and Off of a power MOSFET switch - depending on the difference between a reference voltage and a feedback voltage, the On and Off time varies to regulate the output voltage.
My analog knowledge is quite limited, what I understand so far is:
- The PWM is providing a gate voltage above or below the threshold voltage of the MOSFET
- The input voltage is supplying the drain of MOSFET, and the source of MOSFET is connected with a inductor and a capacitor for some "filtering purpose".
- The inductor can lag response in current change where the capacitor can drag voltage.
But I must have missed something here. I have been struggling with seeing the whole picture of all these analog components working together to form a complete working regulator.
And, why there are two MOSFET instead of one?
Please help me out here.