What are the differences between Linear and Switch Mode Power Supplies?

Switch mode power supplies differ from linear power supplies in how the primary AC voltage is converted into the output DC voltage. Switch mode power supplies use a power transistor to produce a high frequency voltage that is passed through a small transformer and then filtered to remove both the AC component and noise. Linear power supplies deliver DC by passing the primary AC voltage through a transformer and then filtering it to remove the AC component. Switching power supplies feature higher efficiencies, lighter weight, longer hold up times, and the ability to handle wider input voltage ranges. Linear power supplies are usually less expensive, but are limited in capability and tend to be larger in physical size.  more