PWM is used in a lot of electronics. It's used on transistors and mosfets. A transistor or mosfet is basically a switch. Not the game system, but an actual switch. You provide a small amount of electricity to one of the legs and it allows electricity to flow from another leg to the third leg. Think of it like a light switch.you have a wire that goes into the light switch, and when you flip the switch it allows the electricity to then travel out of the switch to the light. With a transistor you don't have a toggle that you flip, you have a thin wire that you can provide a very small amount of electricity and it will switch the transitor to an on state and allow a much larger amount of current to flow through it. But let's say that you are using that transistor to turn on and light up an led. You supply a small amount of power to the transistor and that allows the power to flow to the led and turn it on. But what if you wanted the led to be dimmer, or you want an electric motor to spin slower. A lot of components will not operate if you turn down the power. So to overcome this problem is to use PWM. Think of it as a way to turn the transitor on and off really, really fast. By doing that you are able to dim an led, or slow down a motor. So it can't create scan lines, but if it flashes the screen at a rate that happens to mess with the refresh rate of your actual vision you will see the screen flicker. I'm not saying this is a fix, but you can tell if the PWM is the problem by changing the brightness of your switch. If you are old enough to remember watching old TV's that would show another TV and you would see a grey bar that would travel from the bottom of the screen to the top over and over again, that was kind of the same thing the refresh rate of the camera and the TV were messing things up. Or say you are looking at fast spinning blade of a helicopter and it looks like the blades are spinning slower than they really are. That's because your visions refresh rate cannot keep up with something moving that fast.