Full Wave Rectification Using Four Diodes | Bridge Rectifier

Full wave rectification is a process to convert an alternating current (AC) signal into a direct current (DC) signal. 

Full Wave Rectification Using Four Diodes

This process makes use of four diodes which are arranged in a bridge configuration. 

Why converting AC to DC is necessary? 

AC is the electrical current that periodically changes direction and fluctuates between positive and negative values. AC current is used in power transmission since it is useful for long-distance transport. But, most electronic devices operate on DC — the unidirectional current. In order to power and use these devices, a rectifier is necessary to convert AC to DC.

Rectification

Rectification is the process of converting an AC signal into a DC signal. 

In a half wave rectifier, only one-half of the AC signal is utilized, which results in energy losses.

In full wave rectification, the entire AC signal is used, sufficiently increasing efficiency and reducing energy losses. Read out more here.

Diode

A diode is a two-terminal electronic component that conducts current in only one direction, It allows electrons to flow from the positive terminal to the negative terminal when a forward bias voltage is applied. This property makes diodes ideal for rectification purposes. The operation of the pn junction diode is covered here.

 Bridge Rectifier:

A full wave rectifier circuit consists of either two or four diodes. In four diodes Rectifier, Diodes are arranged in a specific configuration called a bridge rectifier. 

The AC input signal is applied across the bridge Rectifier, and the rectified DC output is obtained from the other two terminals. This configuration enables full wave rectification.

The operation of the diodes in the bridge rectifier is divided into two half cycles. 

Positive half cycle:

During the Positive half cycle, the voltage at Diode D1 becomes positive, making it the positive terminal. Diode D1 and Diode D2 conduct and D3 and D4 do not conduct. These two Diodes (Diode D1 and Diode D2) are in series with load resistance and there we obtain output. 

During negative alternation of the input signal, Diodes D3 and D4 conduct while Diodes D1 and D2 do not conduct. The Diodes (Diodes D1 and D2) are in series with load resistance and hence contribute to the output. 

During each half cycle, the direction of current through the load RL remains the same, which results in unidirectional current or Rectification. In this circuit, both halves of the AC signal have been utilised using the combinations of conducting and non-conducting diodes.

Advantages of Full Wave Rectification:

1. In comparison to half Wave Rectification, it provides a higher percentage of usable output. The conversion efficiency is doubled and power losses are minimized.  The power conversion capabilities are improved as well. 

2. Full wave rectification with a bridge rectifier eliminates the need for a center-tapped transformer which has a grounded middle point, on either side of which voltage signals are drawn. This results in low power efficiency due to energy loss in such a transformer and the complexity to the circuit and has lower power efficiency due to the energy loss in the center-tapped transformer. While bridge Rectifier Circuit is easy in comparison. 

Filter Capacitor: 

To smoothen the DC output and enhance its quality, capacities are added to the circuits called filter capacitors that reduce fluctuations in the voltage. 

 

The capacitors store energy during the peak of the rectified waveform and release it during the troughs, ensuring a more constant DC output. 

This filtering is useful in applications where a stable and smooth DC voltage is required, such as in electronic devices and power supplies.

Input Signal

Fully Rectified Signal

              Fully Rectified Signal in Opposite Direction