A power supply or UPS is really a device that supplies electrical energy to one or more electrical loads. The term is most commonly applied to devices that convert one form of electrical energy to yet another, though it might also refer to devices that convert another type of energy (e.g., mechanical, chemical, solar) to electrical energy. A regulated power source is one that controls the output voltage or present to a certain value; the controlled worth is held nearly continual despite variations in either load electric current or the voltage supplied by the power supply's power source.

A typical power supply circuit usually includes with the following modul circuit:

Transformer

Transformers convert AC electrical power from one voltage to an additional with small loss of energy. Transformers function only with AC and this is among the reasons why mains electrical energy is AC.

Step-up transformers enhance voltage, step-down transformers minimize voltage. Most energy supplies use a step-down transformer to reduce the dangerously high mains voltage (230V in UK) to a safer low voltage.

The input coil is referred to as the main and also the output coil is referred to as the secondary. There's no electrical connection in between the two coils, rather they are linked by an alternating magnetic field developed within the soft-iron core from the transformer. The two lines within the middle of the circuit symbol represent the core.

Transformers waste very little energy so the power out is (almost) equal towards the energy in. Note that as voltage is stepped down electric current is stepped up.

The ratio with the variety of turns on each coil, called the turns ratio, determines the ratio in the voltages. A step-down transformer includes a big variety of turns on its primary (input) coil that is linked for the high voltage mains supply, as well as a small number of turns on its secondary (output) coil to provide a reduced output voltage.

Rectifier

There are numerous approaches of connecting diodes to create a rectifier to convert AC to DC. The bridge rectifier is the most essential and it generates full-wave varying DC. A full-wave rectifier can also be created from just two diodes if a centre-tap transformer is applied, but this technique is hardly ever being used now that diodes are more affordable. A single diode might be put to use as a rectifier however it only uses the positive (+) components from the AC wave to generate half-wave varying DC.

Smoothing

Smoothing is performed by a significant value electrolytic capacitor linked across the DC supply to act as a reservoir, supplying electric current to the output when the varying DC voltage from the rectifier is falling. The diagram exhibits the unsmoothed varying DC (dotted line) along with the smoothed DC (solid line). The capacitor charges quickly near the peak of the varying DC, after which discharges because it supplies electric current towards the output.

Voltage regulator ICs are obtainable with fixed (usually five, 12 and 15V) or variable output voltages. They're also rated by the maximum electric current they can pass. Negative voltage regulators are accessible, primarily for use in dual supplies. Most regulators contain some automatic protection from excessive electric current ('overload protection') and overheating ('thermal protection').