A bench power supply is an essential piece of equipment if you do a lot of electronics or other powered projects on your bench and need a reliable source of power at different voltages. They are very useful tools in testing circuits, as they allow you to adjust the voltage to a specific value depending on what project you are working on. A variable DC bench power supply also allows you to set a maximum current, so if there is a short circuit in your project the bench supply will shut down hopefully preventing any harm to some components in your project. Bench power supplies are versatile, accurate and stable and don’t cost too much.
When it comes to power you have 4 units to be aware of, Current, Voltage, Power and Resistance. It's very important that if you are supplying your circuit with some voltage, your supply can keep up with the current drawn.
There are two basic types of power supplies in common use: linear and switch-mode. Both are available for use as bench DC power supplies.
Linear power supplies operate by rectifying AC line power to create DC and then filtering and regulating it to produce a user-selectable voltage or current levels. Linear supplies are heavier because the 50 Hz or 60 Hz transformer and associated filters are physically larger.
Switch-mode power supplies start out the same way, rectifying and filtering AC line input voltage, however, they chop (or "switch") the DC into high-frequency AC. Switch-mode power supplies are significantly smaller, lighter and more efficient than linear power supplies, so they have replaced linear supplies in many applications.