Simulation of rectifiers in Pspice: tutorial 4

In the last tutorial, we have seen how to simulate RL and RC circuits in Pspice. In this tutorial I will help you to simulate a circuit in which a rectifier is designed. Both full wave (bridge) rectifier and half wave rectifiers are designed with the help of PSPICE in this tutorial. At the start of the tutorial a brief introduction regarding rectifiers (both full wave and half wave) is provided. After that he circuits are implemented on PSPICE and the simulation output is verified. Both full wave and half rectifiers are implemented one by one. At the end of the tutorial you are provided with an exercise to do it by yourself, and in the next tutorials I will assume that you have done those exercises and I will not explain the concept regarding them.

Introduction to Rectifiers

A rectifier is an electrical term and is used to name a circuit which can convert AC (Alternating Current) signal to DC (Direct Current) signal. In simple words a circuit that can convert AC to DC is known as rectifier. The opposite of a rectifier is an inverter. Two main types of a simple rectifier are:

• Half wave rectifier
• Full Wave rectifier

Half wave rectifier

A half wave rectifier consists of a single diode and a load resistance. It only allows the positive part of an AC signal and during the negative half cycle the diode will act as reverse bias and the voltage at the output resistance will be zero.

Full wave rectifier

In a full wave rectifier four diodes are connected in the form of a bridge (that’s why called a bridge rectifier) and two of the diodes allow the positive half cycle of the AC signal to pass as it is and the other two diodes changes the direction of the negative half cycle and at the output resistor it also appears as a positive cycle and we get a pulsating DC as you will see shortly in the simulation part.

Full wave rectifier in PSpice

• Lets’ design a full wave rectifier first as it is the complex one. Open the PSPICE design manager on your PC by typing design manager in the search bar. From the design manager click on the run schematic button to open a new blank schematic as shown in the figure below,

Figure 1: Opening new schematic

• After opening the new schematic before jumping into designing first save the schematic by clicking on the file button at the top left corner and then selecting save as so that we can access it anytime in the future. Refer to the figure below,

Figure 2: Saving schematic

• Click on the get new part icon at the top bar of the schematic window in order to search for the components that are needed for circuit designing.

Figure 3: Getting new part

• In the get new part window, type ‘d’ it will display a list of diodes available in PSPICE. From that list select D1N4002 (a simple diode) as shown in the figure below,

Figure 4: Diodes

• After selecting the diode place four diodes on the schematic you created previously in such a manner that each two diodes are in series with each other and are in parallel with other pair of diodes already in series. Refer to the figure below to see the arrangement of the diodes in a full wave rectifier.

Figure 5: Diode bridge

• Again open the get new part window and in the pat name block type Vsin, select the supply from the list given and then click on place & close as shown in the figure below

Figure 6: Input sin

• Place the component in the circuit diagram, and again open the get new part window and in the pat name block type R, select the resistor to be used as a load from the list given and then click on place & close as shown in the figure below

Figure 7: Placing resistor

• Next step is to place a ground, do the same again and in the part name type Gnd and select the ground and then click on place & close as shown in the figure below,

Figure 8: Ground

• The placed components in the schematic window are shown in the figure below,

Figure 9: Placed components

• Next step is to make connections between all these components, on the top bar of the schematic window, select place wire option and connect all the components with the wire as shown in the figure below,

Figure 10: Complete circuit diagram

• Now set the properties of the Vsin block, i.e. double click on the Vsin component and the properties window will appear. Change the values of VAMPL, VOFF and FREQ according to your need and click on Save Attr after updating each value, as shown in the figure below,

Figure 11: Supply attributes

• On the top of the schematic window, click on the Voltage/Level Marker button as shown in the figure below,

Figure 12: Voltage marker

• Place it at the resistor node as shown in the figure below,

Figure 13: Voltage marker placed

• Next step is to adjust the properties of the simulations in order to produce the graph of the voltage at the marker. Click on analysis and then click on Setup as shown in the figure below,

Figure 14: Analysis setup

• A widow will appear, click on the transient block on the window and adjust the properties of the window according to your requirement, refer to the figure below

Figure 15: Transient properties

• If we are interested in checking the voltage on a specific wire in spite of checking it at a node, double click on the wire and inn the window that appear as a result, type the name of the wire you want to label it with, as shown in the figure below,

Figure 16: Labeling a wire

• Now comes the simulation part, click on the analysis at the top bar of the schematic window and then click on simulate as shown in the figure below,

Figure 17: Simulating the circuit

• A schematic window will appear showing the voltage across the load resistor as shown in the figure below

Figure 18: Output of full wave rectifier

• The output of the full wave rectifier as we have discussed previously is a pulsating DC and not pure DC. Introduction of a capacitor in parallel with the load resistor will result in the conversion of this pulsating DC into pure DC signal. From the graph above it is obvious that the signal at the load resistor is unidirectional i.e. no part of the signal is below the 0 line of the graph (negative), which implies that the rectifier is working properly.
• Lets’ design a half wave rectifier now. A half wave rectifier consists of a single diode connected in series with the input sin voltage and the load resistor, as shown in the figure below,

Figure 19: Half wave rectifier

• As you have placed the parts in case of full wave rectifier do the same with half wave. Adjust the input settings and the analysis setup settings and simulate the circuit. The output of the half wave rectifier is shown in the figure below,

Figure 20: Output of half wave rectifier

• As we have discussed in the introduction part, the negative part of the output of the half wave circuit will be clipped to zero so is obvious from the simulation results.

Exercise:

• Convert the pulsating DC at the output of a full wave bridge rectifier into pure non pulsating DC

(Hint: You can do this with the help of capacitor installation in the circuit)

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