It's actually pretty simple in concept. In a switching-type power supply, you rectify the incoming AC to DC, then chop it on and off (this is the "switching" part) to make a high frequency square wave. You step that down with a small transformer, then smooth it out into DC again. To regulate the voltage, you vary the "on" time of the chopper circuit.
The biggest advantage here is the transformer can operate at a very high frequency, usually around 30 kHz, instead of 50 or 60 Hz. Since the amount of core steel you need in a transformer is inversely related to the frequency, the transformer ends up being much smaller and lighter. Also, since you're rectifying the incoming power immediately, the input frequency doesn't matter. Finally, because the voltage is being regulated by a chopper that's always either on or off, instead of by a linear regulator, far less energy is wasted as heat. (A Commodore 64 power supply is an example of a linear design -- they were bulky and infamously hot-running.)
The main disadvantage is that switching supplies produce a lot more RF noise than linear supplies. Better designs are shielded to cut down on this.
(no subject)
Date: 2006-12-27 04:23 am (UTC)The biggest advantage here is the transformer can operate at a very high frequency, usually around 30 kHz, instead of 50 or 60 Hz. Since the amount of core steel you need in a transformer is inversely related to the frequency, the transformer ends up being much smaller and lighter. Also, since you're rectifying the incoming power immediately, the input frequency doesn't matter. Finally, because the voltage is being regulated by a chopper that's always either on or off, instead of by a linear regulator, far less energy is wasted as heat. (A Commodore 64 power supply is an example of a linear design -- they were bulky and infamously hot-running.)
The main disadvantage is that switching supplies produce a lot more RF noise than linear supplies. Better designs are shielded to cut down on this.