What is a center tapped full wave rectifier?

In this type of rectification circuit a center tapped transformer has an extra wiretapped from mid of secondary coil winding and two diodes are used to input AC voltage into DC Voltage. reference to center tapped terminal transformer has two secondary coils with equal inductance value or number of turns. Both Secondary outputs voltages are reversed polarity from each other. In Fig 14 Anodes of D2 and D3 are connected to secondary outputs. and cathodes are connected to load and deliver positive supply. Center tapped terminal is used to provide a returning path to load current. or exhibit as a negative supply terminal or ground. Thus, the center tap transformer converts single-phase AC Voltage into Bi-Phase AC voltage with a 180-degree phase difference.

Center tapped full wave rectifier diagram

Full Wave Rectifier constructed with half bridge or two diodes negative output is obtained by tapping from transformer's secondary coil
Fig:14 Center tapped transformer FW rectifier with two diodes

Working of center tap rectifier               

 in fig 15 positive half cycle of the single-phase sine wave is applied to the input of the center-tapped transformer. The upper coil terminal is positive regarding GND or center tap terminal on the secondary side. D1 is forward biased and provides a positive voltage to RL and RL current is returned to the secondary coil from the center tap terminal. the center tap is working as a negative supply terminal. at this time lower secondary coil terminal voltage is negative so the D2 diode is reversed biased and greyed in figure 15. And D2 is preventing negative supply voltage from injecting into positive output.

Center Tap transformer rectifier operation in positive half cycle. half-bridge rectifier positive half cycle
Fig 15 Center Tapped transform rectifier operation in positive half cycle

After the ending of the positive half cycle. the polarity of input supply voltage is reversed as shown in fig 16. Now voltage on upper sec terminal is negative and at lower terminal voltage is positive with ground reference. So D2 is now reverse biased. And act as a barrier to protect the load from the negative supply voltage. and D2 is forward bias and supplies positive voltage to load from the lower secondary terminal. The center tap connection is working as a negative supply path.

Center Tapped half bridge rectifier operation in negative half cycle. half-bridge rectifier negative cycle.
Fig 16 Center Tapped transform rectifier operation in negative half cycle

in both figures, 16 output waveform is given. Both sinewave cycles are located on the positive side without changing the sinewave shape. we desire a smooth DC output. To remove these bumps filter circuit is used. The filter may consist of a single capacitor or multiple components like choke and inductors.

RMS value of output voltage of full wave rectifier

The RMS value of the output voltage of a full-wave rectifier is:

Vrms = (Vmax – Vf/2) / √(2)

where Vmax is the maximum voltage of the AC input signal and Vf is the forward voltage drop of the diode.

Center tapped full wave rectifier with capacitor filter

like bridge rectifier filter circuit center tap rectifier output may be smoothened by same circuits. Different filter configurations may be used to acquire a plane DC line on the graph. In figure 17 between rectifier output and load terminal, an LC pie filter circuit is applied. in this filter, capacitors store electrical energy and deliver it when the rectifier output voltage is decreasing. inductor blocks high frequencies noise and attenuates 100 Hz ripple voltage. so overall pie filter works better than a single capacitor filter. for sensitive loads common mode choke is used to remove spikes and external Electromagnetic interference. in Figure 8A effect of filters on full wave rectifier waveform is given. the chart is also applicable to the center tap rectifier. the only difference is the single diode forward bias voltage.

Center tap full wave rectifier with pie filter capacitor.
Fig 17 Center tap full wave rectifier with filter

A full-wave rectifier with an LC pi filter is a circuit used to convert an AC voltage into a DC voltage with reduced ripple voltage. The LC pi filter is used after the rectifier to filter out the unwanted AC components and smooth the output. Here are the formulas and calculations for a full-wave rectifier with an LC pi filter:

Capacitance calculation:

The capacitance required for the filter can be calculated using the formula:

C = I * (1 – cos(α)) / (2 * f * Vr * cos(α/2)^2)

where, C is capacitance required for the filter in Farads I is load current in Amperes α is the angle of conduction of the diodes, which is 180° for a full-wave rectifier f is frequency of the AC input Vr is desired ripple voltage

Inductance calculation:

The inductance required for the filter can be calculated using the formula:

L = (Vr * (1 – cos(α)) / (2 * f * I * cos(α/2)^2))^2

where, L is inductance required for the filter in Henries I, α, f, and Vr are the same as in the capacitance formula.

Ripple voltage calculation:

The ripple voltage can be calculated using the formula:

Vr = I * (1 – cos(α)) / (2 * f * C)

where, Vr is ripple voltage in Volts I, α, f, and C are the same as in the capacitance formula. The capacitance and inductance values calculated using the above formulas are theoretical and may need to be adjusted based on practical considerations such as the availability of suitable components and their tolerances.

Q&A about Center Tapped FW Rectifier

What is the purpose of center tapped transformer?

The purpose of a center tapped transformer is to provide a means of creating a split power supply from a single AC voltage source.

What is the meaning of centre tapped?

Center tapped refers to a transformer that has a wire or terminal connected to the center point of the winding, which is used to split the voltage into two halves.

What is the difference between full wave rectifier and center tapped?

The main difference between a full wave rectifier and a center tapped rectifier is the number of diodes used to rectify the AC voltage. A full wave rectifier uses four diodes, while a center tapped rectifier uses two diodes and a center tapped transformer.

Why it is called center tapped rectifier?

It is called a center tapped rectifier because it uses a center tapped transformer to split the AC voltage into two halves, which are then rectified by two diodes to produce a DC output.

Why bridge rectifier is better than center tapped?

A bridge rectifier is better than a center tapped rectifier because it uses four diodes to rectify the AC voltage, which results in a higher efficiency and lower ripple voltage compared to a center tapped rectifier.

What is meant by the ripple factor?

The ripple factor is a measure of the amount of AC voltage that remains in a DC output after rectification, expressed as a percentage of the total DC voltage.

What is ripple and ripple factor?

Ripple is the small AC voltage component that remains in a DC output after rectification. Ripple factor is the ratio of the RMS value of the AC voltage to the DC voltage, expressed as a percentage.





2 responses to “Center tapped full wave rectifier”

  1. […] Center-tapped full wave rectifier: This circuit uses a transformer with a center-tapped secondary winding and two diodes. The center-tap is connected to the ground, and the two outer ends of the secondary winding are connected to the diodes. The diodes conduct in alternate half-cycles of the AC waveform, allowing current to flow in one direction through the load. […]

  2. […] P.F.; Gules, R.; Romaneli, E.F.R.; Annunziato, R.C. A Modified SEPIC Converter forHigh-Power-Factor Rectifier and Universal Input Voltage Applications. IEEE Trans. Power Electron. 2010, 25,310–321. […]