A bridge rectifier is a relatively simple but important electronic component, consisting of an arrangement of at least four diodes in a bridge circuit configuration. The main defining feature of a bridge rectifier diode is that its output polarity will always be the same, regardless of the polarity at its input terminals.
A key property of the diodes in a bridge rectifier is that they only allow current to flow through them in one direction. By arranging a series of diodes in a certain way, we can therefore ensure that the current output across the bridge rectifier is unidirectional, even if it is bidirectional at the input. As such, these diode devices are known as rectifiers, because they perform a process of current rectification (converting alternating current to direct current).
They play an important role in many types of device or circuit power supplies because raw AC power flowing from a mains source periodically changes its flow direction. As such, AC power effectively results in a back and forth motion of electrons coming from the mains source into the device circuitry.
For powering almost all device types based on a standard PCB electronic circuit, this bidirectional input current needs to be converted - or rectified - into a stream of electrons all flowing in the same direction. This results in a DC power (direct current) output signal, and thus a usable output Voltage from which the device or product in question can draw stable and consistent power.
The individual component that performs this key task in a discrete circuit is typically a diode known as a rectifier; specifically, a bridge rectifier, or diode bridge. Acting as a bridge rectifier is one of the most important roles for diodes in any type of electrical circuitry. Today, semiconductor diode bridges will be found in almost any electrically powered device.
A bridge rectifier arrangement is a particularly common feature of device power supplies. They effectively act as a transformer positioned between the AC socket input and the DC output that ultimately powers the circuitry and components in the device. Bridge rectifiers are typically attached to a circuit via a two-wire AC input connection.