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Full wave Rectifier- Formula, Working, Efficiency, Circuit

Full Wave Rectifier

A full-wave rectifier converts both halves of each cycle of an alternating wave (AC signal) into a pulsing DC signal. To convert AC voltage to DC voltage, full-wave rectifiers are utilised, which require numerous diodes to build. The technique of converting an AC signal to a DC signal is known as full wave rectification.

Full Wave Rectifier Circuit

Rectifiers are circuits that convert alternating current (AC) to direct current (DC). The rectifiers are full-wave rectifiers if they rectify both the positive and negative half cycles of an input alternating waveform. A collection of diodes is used in full-wave rectifiers to achieve this. A diode only allows current to flow in one direction and prevents it from flowing in the opposite way. This approach is used to build various rectifiers.

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Full Wave Rectifier Types

There are two categories in which Rectifiers can be divided: Half Wave Rectifiers and Full Wave Rectifiers

Half Wave Rectifier

Full wave Rectifier- Formula, Working, Efficiency, Circuit_40.1

When we utilise a half-wave rectifier, we waste a lot of power since only half of each cycle passes through while the other cycle is blocked. Furthermore, the half-wave rectifier is inefficient (40.6 percent), so it can’t be used for applications that require a smooth and consistent DC output. A full wave rectifier is used to produce a more efficient and stable DC output.

Full Wave Rectifier

Full wave Rectifier- Formula, Working, Efficiency, Circuit_50.1

Two diodes are now utilised in a Full Wave Rectifier circuit, one for each half of the cycle. The secondary winding of a multiple winding transformer is split evenly into two halves with a common centre tapped connection (C).

When the anode terminal of each diode is positive with respect to the transformer centre point C, each diode conducts in turn, producing an output throughout both half-cycles, double that of the half-wave rectifier, making it 100 percent efficient.

Full wave Rectifier: Formula

Because the intervals between each half-wave created by each diode are now filled in by the second diode, the average DC output voltage across the load resistor is now double that of the single half-wave rectifier circuit and is approximately 0.637Vmax of the peak voltage, assuming no losses.

Full wave Rectifier- Formula, Working, Efficiency, Circuit_60.1

VRMS = 0.7071VMAX, where VMAX is the maximum peak value in one half of the secondary winding and VRMS is the rms value. IDC = VDC/R is the formula for DC current.

If each half of the transformer windings has the same rms voltage value, the output waveform’s peak voltage is the same as before for the half-wave rectifier. Different transformer ratios can be utilised to get different DC voltage outputs.

Full wave Rectifier: Diagram

Full wave Rectifier- Formula, Working, Efficiency, Circuit_70.1

 

Full wave Rectifier: Working

The full wave rectifier’s input AC is extremely high. The rectifier circuit’s step-down transformer converts high voltage AC to low voltage AC. The load resistor is connected to the anode of the centre tapped diodes, which is connected to the secondary winding of the transformer. The top half of the secondary winding becomes positive during the positive half cycle of the alternating current, while the second half of the secondary winding turns negative. Diode D1 is forward biassed during the positive half cycle because it is connected to the secondary winding’s top, whereas diode D2 is reverse biassed since it is connected to the secondary winding’s bottom. As a result, diode D1 will conduct as a short circuit, but diode D2 will not conduct as an open circuit.

Because the top half of the secondary circuit becomes negative and the bottom half of the circuit becomes positive during the negative half cycle, diode D1 is reverse biassed and diode D2 is forward biassed. DC voltage is obtained for both the positive and negative half cycles in a full wave rectifier.

The Positive Half-cycle

Diodes D3 and D4 conduct in series during the negative half cycle of the supply, but diodes D1 and D2 switch “OFF” since they are now reverse biassed. The load’s current is flowing in the same direction as before.

The Negative Half-cycle

As the current flowing through the load is unidirectional, so the voltage developed across the load is also unidirectional the same as for the previous two diode full-wave rectifier, therefore the average DC voltage across the load is 0.637Vmax.

 

Full-wave Rectifier: Advantages and Disadvantages

Advantages

The key benefit of this bridge circuit is that it does not require a specific centre tapped transformer, which reduces the size and expense of the circuit. The load is connected to one side of the diode bridge network, while the single secondary winding is connected to the other. The other advantages of a full wave rectifier are:

  • The frequency of the ripple of a full wave rectifier is two times that of the input.
  • The efficiency of a full wave rectifier is much more than half wave rectifier.
  • The full wave rectifier has the high DC power output.
  • The ripple factor in a full wave rectifier is reduced.
  • Because the ripple voltage in a full wave rectifier is low and the frequency is higher, only a basic filtering circuit is needed.
  • The full wave rectifier has more output voltage.
  • The factor of transformer use is higher in full wave rectifier.
  • Both parts of the AC waveform are used in a full wave rectifier.
  • Using the ripple frequency of a full wave rectifier makes it easier to offer smoothing.

Disadvantages

The disadvantages of a full wave rectifier are as follows:

  • Comapred to a Half-wave rectifier, a full-wave rectifier is much more complex.
  • For a full wave rectifier, two diodes for the centre tap rectifier and four for the bridge rectifier are required.
  • The diode’s PIV rating for a full wave rectifier is greater.
  • PIV diodes with a higher PIV of a full wave rectifier are larger and more expensive.
  • The centre tap transformer of a full wave rectifier is expensive.
  • On an audio circuit in a full wave rectifier, the double frequency hum may be more perceptible.
  • The middle tap on the secondary winding of a full wave rectifier is difficult to locate.
  • Because each diode only uses one-half of the transformer secondary voltages in a full wave rectifier, the DC output is modest.
  • The full-wave rectifier circuit is ineffective when only a little voltage needs to be rectified.

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Full wave Rectifier: FAQs

Ques. What is the working principle of full wave rectifier?

Ans. Only a half cycle of an AC waveform is used by the half-wave rectifier. A full-wave rectifier has two diodes and uses both halves of the AC signal to produce its output. During the time when one diode is blocking current flow, the other diode is conducting and allowing current to flow.

Ques. Why full wave rectifier is used?

Ans. The full-wave rectifier, when used in a power supply, allows us to convert practically all of the incoming AC power to DC. The full-wave rectifier also serves as the brains behind the circuitry that allows sensors to connect to the RCX in either polarity.

Ques. What is the conclusion of full wave rectifier experiment?

Ans. A full wave rectifier has an efficiency of roughly 81.2 percent, which is twice that of a half wave rectifier. The full wave bridge rectifier is used to acquire DC voltage from an AC supply.

Ques. What is ripple and ripple factor?

Ans. The residual periodic change of the DC voltage within a power supply obtained from an alternating current (AC) source is known as ripple (particularly ripple voltage) in electronics. After rectification, the alternating waveform is not completely suppressed, resulting in this ripple.

With increasing firing angle, the ripple factor, which is defined as the ratio of the rms value of the ac component to the dc component, rises.

Ques. Which full wave rectifier is better?

Ans. The peak inverse voltage across each diode in a center-tapped rectifier is twice the maximum voltage over half of the secondary winding. Bridge rectifiers have a higher transformer utilisation factor than centre tapped full wave rectifiers, making them more advantageous.

Ques. What is the difference between half wave and full wave rectifier?

Ans. The transformation of a half wave rectifier employs only half of the AC cycle. The negative half of the input is blocked when the positive half is passed, and vice versa. A full wave rectifier is an electrical circuit that converts an entire cycle of alternating current into pulsating DC.

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