An uncontrolled full-wave rectifier is a type of rectifier circuit that converts AC power (Alternative Current) into DC power (Direct Current) by utilizing both halves of the AC waveform. It is called an "uncontrolled" rectifier because it does not use any external control signals to regulate the output DC voltage or current (it uses diodes as the switching devices).

Figure (1)

There are two main types of uncontrolled full-wave rectifiers: center-tapped and bridge rectifiers.

A center-tapped full-wave rectifier uses a transformer with a center-tapped secondary winding and two diodes to rectify the AC power. The transformer steps down the AC voltage to a suitable level, and the diodes are used to rectify the AC waveform. The output DC voltage is the average value of the AC voltage, and it has a smooth waveform without any pulsations.

Figure (2) Center tapped transformer FWR

A bridge rectifier uses four diodes arranged in a bridge configuration to rectify the AC power. The output DC voltage is also the average value of the AC voltage, and it has a smooth waveform without any pulsations.

Figure (3) Bridge FWR

Uncontrolled full-wave rectifiers have some advantages over uncontrolled half-wave rectifiers. They have a higher power conversion efficiency because they utilize both halves of the AC waveform. They also produce a smoother DC output voltage, which may be more suitable for some applications.

Uncontrolled full-wave rectifiers are used in a variety of applications where a simple, low-cost solution is needed to convert AC power into DC power. Some examples of applications for uncontrolled full-wave rectifiers include:

Power supplies for electronic devices: Full-wave rectifiers are commonly used in power supplies for electronic devices, such as computers, TVs, and smartphones, to convert the AC power from the wall outlet into DC power.
Battery chargers: Full-wave rectifiers are often used in battery chargers to convert the AC power from the wall outlet into DC power to charge the battery.
Renewable energy systems: Full-wave rectifiers are used in renewable energy systems, such as solar panels and wind turbines, to convert the AC power generated by the system into DC power that can be used by the load or stored in a battery.
Industrial power supplies: Full-wave rectifiers are used in industrial power supplies to convert the AC power from the utility grid into DC power for use by industrial equipment.

FWR with Resistive Load

A) Bridge Rectifier:

In the Bridge Rectifier Figure (4) Diode pairs D1,2 conduct (forward biased) in the positive half cycle and D3,4 in the negative half cycle of the input signal so that the load current never changes its direction (up to down in the figure). (nor load voltage polarity). as shown in figure (4)

Figure (4)

Figure (5) show the input output voltage and currents wave forms relations.

Figure (5)

B) Center-Tapped transformer Rectifier:

In the center tapped transformer circuit shown in Figure (6), diode D1 conducts in the positive half cycle and D2 conducts in the negative half cycle, so that the load current never changes its direction (right to left in the figure). (nor load voltage polarity).

Figure (6)

Figure (7) show the input output voltage and currents wave forms relations.

Figure (7)

The rms and average output voltage and current relations of FWR can be computed as following :

Example 1) A single-phase rectifier has a resistive load of 18 Ω. Determine (a) the average load current, (b) the rms load current, (c) the average and rms current in each diode (d) the average and rms source current. (e) power factor. For a bridge rectifier with an AC source of 120 V rms and 60 Hz.

Answer)

Example 2) A single-phase center-tapped transformer rectifier has an AC source of 240 V rms and 60 Hz. The overall transformer turns ratio is 3:1 (80 V rms between the extreme ends of the secondary and 40 V rms on each tap). The load is a resistance of 4 Ω . Determine (a) the average load current, (b) the rms load current, (c) the average source current, and (d) the rms source current. Sketch the current waveforms of the load and the source.

Answer)