Power Supplies can be divided into two types for electronic devices, linear and switching power supplies. A switching mode power supply has the same rating as a Linear Power Supply but will be a lot more complex and usually Switching Mode Power Supplies are smaller. A Linear Power Supply is used for high current devices. They tend to be a lot bigger and bulkier than the Switching Mode Power Supply and a lot simpler in design.

Linear Power Supplies powered by AC tend to require the use of a transformer to convert the voltage from the mains outlet to a different voltage, this tends to be converted to a lower voltage. However a Rectifier is needed if it is used to produce DC, In addition a capacitor will be used smoothing the pulsating current from the rectifier. AC Power Frequency's relate the frequency the pulsations occur at (a multiple of 50Hz or 60Hz is a good example).

An unregulated power supply will produce a varying voltage depending on the variations and on the load of the AC Supply Voltage. A Linear Regulator will be used for critical electronics applications, the Linear Regulator will adjust and stabilise the voltage. When a Linear Regulator is used with a DC current it will greatly reduce the noise and ripple in the output of the current. They can also protect the Power Supply from overcurrent due to current limiting.

The AC supply in series with a single resistor and diode form the simplest DC Power Supply Circuit, these are very common in the use of rechargeable flashlights.

AC stands for Alternating Current, in Alternating Current the flow of electric charge reverses direction periodically, for instant an AC Current will move forward the backwards over and over again repeating the cycle of movement.

Electricity that is delivered to Residences and Businesses is in the form of AC Electricity. A 'Sine Wave' is the usual waveform of an AC Circuit; different waveforms can be used in different applications tho such as: Square Waves or Triangular Waves. Another example of an alternating current is electrical wires passing audio and radio signals.

DC stands for Direct Current and this is the unidirectional flow of electric current. Batteries, Solar Cells and Thermocouples are a few examples of sources that produce Direct Current. Semiconductors, Vacuum (Ion or Electron), insulators and wires are examples of conductors that DC (Direct Current) can flow through. Direct Current was formally known as Galvanic Current.

By use of a Rectifier, a Direct Current can be obtained from an Alternating Current. The rectifier contains electromechanical elements that will only allow the current to flow in one direction.

Nearly all electronic Power Supply Systems used Direct Current, it is also the current used to charge batteries. Electrochemical processes and the production of aluminium use very large amounts of direct current power supply, railway propulsion also requires a DC Current.

AC DC Power Supply is a very important source of power in the world we live in and many applications require them.