# Center Tapped Rectifier in LTspice

A center-tapped rectifier is a type of full-wave rectifier in which a center-tapped transformer is used. It converts both halves of each cycle of an alternating signal into a pulsating signal. A rectifier is an electrical device that converts alternating current or voltage (AC), into direct current or direct voltage(dc). The rectifier is classified into two types.

• Half wave Rectifier
• Full wave rectifier.

A half-wave rectifier is fined as a type of rectifier that only allows one half-cycle of an AC voltage waveform to pass, blocking the other half-cycle. Half-wave rectifiers are used to convert AC voltage to DC voltage. It is done by using a diode or a group of diodes.

A full-wave rectifier converts both halves of each cycle of an alternating wave (AC signal) into a pulsating DC signal.

A full wave rectifier is classified in to two types .

1. Center tapped rectifier
2. Bridge rectifier.

Here we are discussing the center-tapped rectifier in ltspice. In the case of the center-tapped full-wave rectifier, only two diodes are used and they are connected to the opposite ends of a center-tapped secondary transformer as shown in the figure below.

Center tapped rectifier in Ltspice

The first step is to draw the circuit in lt spice. In this circuit, we are using only four components i.e a voltage source, a diode,Transformer and a resistor.

#### 1. Draw the ac voltage source

Here the transformer input is connected into the main AC supply. The normal ac input voltage is 230 v and 50 Hz. It means that the root-mean-square value of ac voltage is 230v. so the value of the peak to peak voltage= 1.414 x Vrms( Root means square value). Here, Vp.p =1.414 x 230 =325v. Draw the ac voltage source of a 325-volt peak to peak with 50 Hz frequency. In order to construct this, click on the component icon in the ltspice and select voltage source and click ok (Refer below figure). Then position it at the required place on the screen.

Right-click on the voltage source, click on the advanced button. You will get a similar screen like the below one.

By clicking the advanced button a pop-up window will open. In this window, you will have multiple options to select. Examples pulse, sine wave, exponential, etc. Here we need a sine waveform. So click on the “SINE(Voltst….” option and provide the valuers in the corresponding fields.

Dc offset= 0
Amplitude=162.5 ( 325/2)
Frequency=50HZ
AC amplitude=162.5 Series Resistance =.001ohm and click ok. Refer to the below figure

The resultant image is shown in the below figure.

#### 2. Draw the Transformer

Transformers and coupled inductors are key components in many switching regulator designs to include flyback, forward, and SEPIC converters. They perform a critical function in providing an isolation barrier, enabling high step-down or step-up ratios and accommodating multiple or inverting outputs. Although it is possible to make a dedicated subcircuit for a specific transformer, LT spice 4 preferred method is to define a separate inductor for each transformer winding. Here we are using a center tap transformer. In order to make this we need three inductors L1, L2, and L3. To do this, click on the Inductor button and position it on the required place on the screen. Refer to the below figure.

Right-click on the inductor L1 and rename the L1 as Lp( primary winding of transformer).Similarly, we can change the name of L2 as Ls1(secondary winding of transformer) and the name of L2 as Ls2(secondary winding of transformer). Setting the turns ratio of the transformer is simply a matter of choosing the right inductor values. Remember, the inductance is proportional to the square of the turns ratio. In the example above, a turns ratio of 3:1 gives a 9:1 inductance ratio. that means the value of inductor (Lp) is 900uf and the value of inductor (Ls) is 100uf.

Np2/Ns2 = Lp/Ls.

Np=Number of turns of primary winding.

Ns=Number of turns of secondary winding.

Lp=Inductance primary winding.

Ls=Inductance of primary winding.

Refer the below figure.

couples the inductors with a SPICE directive called a K-statement (e.g., “K1 Lp1 Ls1 Ls2 1”.) K is the coefficient of coupling. Its value s between 0 and 1. “1” means the winding is perfectly coupled.

#### 3. Draw the diode

We need two diodes here. To do this, click on the diode button and position it on the required place on the screen. Right-click on the diode and click “pick New diode” and select “1N4148 silicon diode “.Refer to the below figure.

#### 4. Draw the resister

To do this, click on the resister and position it on the required place on the screen. To give the value right click on the resister and type the value. Refer to the below figure.

After this join the component using wire and give ground. It is shown in the figure.

Now, the last step is to label the input and output port. To do this click on the “label net” icon. If you want to label the input port, then type Vin and port type “input”. Similarly, if you want to label the output port then type Vout and port type “output”. Then place the input and output label to the corresponding place on the screen. The final circuit diagram is shown in the below figures.

#### Simulation of Full -wave Center tapped rectifier

To do simulation click on the “simulate button” and select “edit simulation command”. Now, you will see a pop-up window. For the rectifier, we have to plot the waveform in the time domain. So, we are using transient analysis here.

Click on “Transient analysis”. And a submenu will appear. In this only enter the stop value=100ms and click ok. Then, click the “Run” button. Run button is available in the simulate icon on the title bar.

You will see the graphical window on your screen. In order to display both the input and output simultaneously in one plane, right click on the graphic plane and click on the “add plot” plane. Then two plane will appear. For displaying the input and out put, right click on the graphic plane and then click on the add traces. Here we need Vin and Vout. See the below screen

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