Basics of Electronic Components and Rectifiers

Welcome students. In this lecture you will be introduced with certain basic electronic components and one experiment that we will see which is on full wave bridge rectifier with capacitor. The objective of this lecture is to familiarize with the name of different electronic components. Basically, I will show you how they physically look like so that you can at least connect them whenever you want. it is required you can at least identify those electronic components if you see in the circuits function of these components that will see and what is rectification and what are the different ways ways by which rectification can be done that we will also see and finally one bridge full wave bridge rectification circuit will make that circuit will see that how full wave bridge rectification circuit is made and then how it works and finally we will see that the characteristic of this rectifier in a particular simulation platform ok So let us start with a very important component, electronic component which is called diode. Physically diode look like this as you can see here. One end you see it is a silvery color and other end is black. The silvery color end is called cathode that means that end remember you have to connect with the negative end of the power source or you have to connect with the ground and other end you have to connect with the positive end of the power source or some other power source is there. So, this is the way by which if you connect a diode then current will flow through the diode in this direction and diode is called that it is in a forward biased condition. But if you just connect it in a opposite way that means if you connect this end with the negative power source and this end with the positive one then there will be a negative no current through the diode. So here you can see there is a battery and this is the positive end and you see this positive end is connected to the anode part and the negative end is connected to the cathode part through this LED. That is why it is okay and the LED is glowing. Similarly here you can see this cathode part is connected to the negative that is okay and definitely this anode part is connected to the positive with this load. that is why the LED is glowing. But if you see here, you see that cathode part is connected to the positive end of the battery. That means it is in a reverse bias. So, there will be no current flowing through the diode and that is why you can see it is not glowing. Similarly, if you observe this connection, it is again in a reverse bias condition and that is why the LED is not glowing. So, what is the use of diode? Diode is used in a circuit as a switch. Now see this particular component resistor. It is very common component and remember that resistor is mostly used component in the electronic circuits. and here you can see there are different kinds of resistor depending upon their specification different types of color bands are there and depending upon the number of color bands they are also categorized and this color bands actually give the specification of the resistor that what is the magnitude of its resistance okay so let us see that how with the color bands we can identify the resistance let us take one example here you can see there are four this is a four band resistor where this is the first band the first band is brown color so where is the brown in this column here is the brown so brown in if it is in the first band then it is one So you just put 1. Then what is the second color? That is black. So go to the black color in the second band. That corresponds to 0. So just put 0. Then what is the third one? That is yellow. So go to the yellow and corresponding to third you see this is a multiplier. So it is a multiplier 10 kilo ohm. So multiply 10 kilo ohm. that means this resistor magnitude is this so 10 into 10 kilo ohm that means 100 kilo ohm this is what is the resistance and what is this fourth band the fourth band indicates the tolerance here You can see the fourth band indicates the tolerance that if you what is this if this is golden you see that it is a 5% tolerance that means this magnitude that is the specification of the resistance it may vary plus minus 5%. is the meaning of the tolerance. So, what is the use of the resistor? Resistors are used in a circuit, so that if in a component, if the current is limited and if you want to reduce that current, so that the component will not damage, in that case what we do, we connect a resistor in series with that component, so that the current value decreases and that component will not damage. Now, another very important component is the resistor, sorry, capacitor and you can see commonly used capacitors in the electronic circuits are this ceramic capacitor, electrolytic capacitor. Ceramic capacitor, as you can see, they are non-cooperative. polarized that means there is no cathode or anode you can connect with any one of them and here in electrolytic capacitor you can see that there is one anode and one cathode and cathode you can always identify through the this black color line okay so that remember is the cathode and you have to connect with the negative side of the source so capacitor the use of the capacitor remember capacitor tries to smoothen the voltage in a circuit so this is the main function of the capacitor though there are other functions like starting of a motor and all that but basically we are going to explore this particular application of the capacitor that it smoothen the voltage Here you see the LED or the light emitting diode and again you see that it has a cathode and anode legs and you see that cathode is the shorter one and anode is the longer one. This is the way physically you have to understand that which one is anode and which one is cathode. Now remember the shorter one is the cathode. Another way you can see that it is actually circular but one end is bend like this. That means. means a flat end is there and this flat end corresponding to the cathode side okay so if this flat end is there in an led you will understand that that corresponding to that leg is basically the cathode and the other one is anode because sometimes the legs are almost similar it is difficult to identify the which one is longer so in that case this flat surface always indicates the cathode okay here you can see that with a three volt battery this led is connected and you can see the anode the longer one is connected with the positive and the shorter one which is the cathode is connected with the negative so it is glowing but here you can see when you connect this led with a 6 volt then you see a resistance is connected in a series the reason is very simple because the current limit of the led is in the order of say 20 25 milliampere okay So, if the current is more than 20 milliampere through this LED, then this LED will burn. So, you cannot allow more than 20 milliampere. So, if you connect a larger voltage, definitely larger current will pass through this LED. to avoid the damage what we do we connect the resistor if you connect the resistor in series then definitely the current that is flowing in the circuit will be reduced and the current through this LED will be below this 20 20 milliampere. So, the LED is not going to burn even if you are connected with a 6 volt. So, definitely if you want to connect it with a 12 volt, the amount of resistance that is required to save this LED will be more. LED can be used as indicator in many circuits. Now coming to the transistor. Transistor is a very very important component and as you can see physically they look like this and it has three legs you can see 1, 2, 3 and these three legs corresponding to its base. emitter and collector. So by controlling this base basically you can change this collector current. So if you put that zero voltage in the base then you will get zero. current in the collector. So basically this base is kind of a control valve by which you can control the collector current. So if you increase the base voltage then the current will also increase in the collector. So the idea if you can compare with a water flow analogy suppose this is a tank Water is there and there is a valve connected with this pipe and there is a tap through which the water is coming out. So here this tap where from you are getting the water is basically the collector. So this is kind of an output that you are getting in the collector and this tank where some water is there is like an emitter. Okay, and the valve that is connected in the pipe by controlling that valve you can actually control at the output right collector. So this valve is like base. Okay, so by controlling the base basically you are getting the collector. output okay so if you put the zero base voltage then you will get no output so transistors can also be act as a switch or transistor can also be acts as amplifier because by controlling base you can increase the collector current also okay so these are the application of the transistors but in this lecture i am not going to explain the details of how transistor works and all that okay Okay, here you see another very important component that is breadboard. If you look at the construction of the breadboard, there are two channels at the top and there are two channels at the bottom. This top and bottom channels are called the power lines. lines these are called power lines here you can see one power line is shown here that red and blue and this red all these points all these holes they are internally connected by the conductor So, that means if through which if you give 5 volt here say if you give 5 volt here then if you draw something from here you will get 5 volt because all these are connected internally along the horizontal direction. So, along this direction they are connected similarly along this direction they are connected. So, this is true for this top 2 and the bottom 2 these are called power lines. Similarly here you see if you the connection these are called the component lines. here the connection is like this they are not along the length they are connected they are connected along this okay but these two are not connected they are connected along this way okay similarly they are connected along this way in this region but there is no connection between E and F okay so this is the internal connection of the breadboard what is the use of breadboard breadboard is used to hold the different electric components and since because of its own internal connections a lot of much wear connections are not required you can avoid lot of wears to connecting different parts Now, coming to the rectifier, what is rectifier? Rectifier is a device by which we can convert alternating current into direct current. This is the simple definition of what is rectifier. So, rectifier is a device by which AC can be converted into DC. Now what are the different types of rectifier? The different types of rectifiers it can be half wave rectifier or it can be full wave rectifier. Again full wave rectifiers can be center tap rectifier as you can see here or it can be bridge rectifier. Remember bridge rectifier is also a full wave rectifier. So both these are full wave rectifier. Here this is basically the center tap rectifier that has been shown and the bridge rectifier that we will see in the next page. So first you see what is the half wave rectifier. So here in the half wave rectifier you can see in the circuit only one diode has been used. In a center tap rectifier you will find it is full wave rectifier that is produced with the help of two diodes. And in a bridge rectifier you will find you require the four diodes to make a full wave rectifier. Now you see that how it works. Let us consider at a particular half cycle here is the AC input. You can see this one is the transformer and then this is the resistor where you are getting the output. Now here let us consider at a half cycle here it is plus and here it is minus and at that time this diode is in forward bias. So current will flow in this direction. So, in this way the circuit will be completed. So, you will get current in the half cycle, but since it is AC cycle in the next half cycle. the direction of the current will change so this end will become negative and say this will become positive at that time when it will become negative you see this diode will be in a reverse bias so there will be no current flow through this diode and that is why the you will do not get any current at the output. But again when this will become positive then you will get current. So, what will be the output? Output will be like this. In the first half cycle you will get current. Then you do not get any current. Then in the next half next half cycle you will get current then you do not get any current so in this way at the output you are getting dc voltage that is ok but you are getting half wave rectification not the full wave you ok so this is what is called the half wave rectification now coming to the full wave rectification you see here there is one connection where full wave rectification has been shown where there is a transformer let us consider for the first half cycle what what is happening. So, first half cycle let us consider this is plus, this is minus, this end is plus and this end is say minus. Now, what will happen in the first half cycle, this is plus. So, this diode will be in a forward bias. So, current will flow in this direction. So, here you can see the direction of current across the load. so this is the circuit and at that time you see this is negative so there will be no current flowing through this diode because this diode is in a reverse bias condition now consider in the next half cycle what will happen the next half cycle definitely the sign will change if the sign changes then what will happen suppose at that time this will become negative this part will become positive this part will become negative and this part will become positive now you see this is negative that is why this diode is in reverse bias okay but this is positive so this diode is now in forward bias so what will happen so current will flow in this way and you see in the both half cycle the current is flowing through the load in the same direction so you are getting a dc okay so you are getting a dc current in the both half cycle So, at the output, you will get this kind of a full wave rectification. Here it is the voltage and here it is the time. But this is called a center tap rectifier. There is a chance of leakage if there is a potential difference occurs between these two. So, this is not so efficient as the bridge rectifier is. So, bridge rectifier is the most efficient. one for the rectification purpose now we will see that how bridge rectifier works so this is what is the circuit of a bridge rectifier here you can see the transformer here the high voltage ac source is there and And that becomes the low voltage with the transformer ratio. Let us consider for a half cycle, this portion is positive and this portion is negative. Then what will happen? That current will flow in this direction. And you see this is in a forward bias condition. So current will flow. And here is basically your resistance or output you are measuring here. So this is what is the direction of current. and it will go in this way and complete the circuit. Now, consider the next half cycle what will happen. Next half cycle this will become negative and this will become positive. At that time you see that when this end, if you consider from this end that current will flow in this direction and this is in a forward bias. So, current will flow in this direction and again you see it is going through the load in the same direction. So, it is DC. And you see it is in a forward bias. So in this way the loop will be completed. So what we will get? We will get this kind of a DC full wave rectification across the load. But there is a problem. The problem is we are getting full wave rectification. We are getting DC voltage. That is okay. But the problem is there is lot of ripples. there right because ah we want this kind of a dc voltage that is voltage is constant same throughout the time so then that will be better definitely this kind of ripples are not intended so what we can do to what all these ripples how can we reduce these ripples okay to reduce this we use the capacitor as you know the capacitor is used in a circuit to smoothen the voltage so with the help of capacitor we will try to get this kind of a circuit. Let us see, here you can see with the load one capacitor is connected in parallel and when the capacitor is connected in parallel, if you see the output that that output actually shown in this diagram with a black line. This black line is showing the output when the capacitor is there and the dotted purple line which is showing basically if there was no capacitor. So, if there was no capacitor you can see that there were lot of ripples present, but when there is capacitor present then the ripples are not there and here you can see this kind of. output voltage you are going to get respectively smoother voltage what is actually happening you see that this region that i am showing here with the red line is basically the capacitor at that time is discharging let us consider the capacitor is charged in this region and then what happens that when this voltage here is gradually going down that means here the voltage is gradually going down this then the capacitor which is already charged is now discharge and since it will discharge it will try to keep up the voltage it will not allow to voltage to go down so in this way the main intention of the capacitor when capacitor is present it will always try to keep the same voltage so that is why during that period capacitor will not allow to fall the voltage here at the output so capacitor will itself discharge and and try to maintain the voltage. But after the full discharge of the capacitor, then again capacitor will charge and this is what is the charging period. Then again capacitor will discharge and try to maintain the voltage. So voltage will not fall down like this. So in this way by discharging and charging the capacitor is trying to smoothen the voltage there. Now here you can see this simple circuit that here some source AC is there, here this is showing the transformer, here you can see this like 9 is to 1 kind of a ratio is there. The important thing that you try to observe here is this is what is the diode. You see this is one diode, these are the physical diodes you see in the circuit. These are the four diodes present which are connected according to a bridge rectifier that you have seen. Here you can see the capacitor is connected in parallel and here you can see that output the resistance. is present in the form of an LED. So this is what is the bridge rectification circuit and it is connected with some oscilloscope and in oscilloscope we can see the characteristics of the voltage that we have just explained that we will be able to see. Suppose this capacitor when it is not connected when the capacitor is not there at that time what we you will see first of all let us consider if you put the probe of the oscilloscope here here it is the input so what you will you are going to get you are going to get probably this kind of a AC supply that is what is the input now when the capacitor is not there, when the capacitor is not present, let us consider, at that time, if you put the probe here, of the, then what you will see? You will see may be this kind of a, ripple pulsating DC. So now if you add the capacitor, then what you will see? If you add the capacitor, then you will see. this kind of a respectively smoother voltage okay so this is what is the characteristics that we generally observe in oscilloscope here what we are going to do that in a simulator we want to see these characteristics okay so for this simulation we are going to use that lt spice okay so you can easily download this lt spice from the net and install it in your computer and you can do this simulation now let me show you how can we make the circuit in the lt spice platform so this is the lt spice platform you can see go to the file click on new schematic Then you choose the different components that you require. Here is the component. If you click on it, you will get the different components. Here you can see the diode, inductor, capacitor, resistors also all are there. So diode we require four diodes. So just click on it and you just rotate it to rotate the diode orientation. You press control plus R. okay now you just click you need four diodes so click four times one two three four then you just press escape okay so now what you have to do you just connect all these diodes with the help of where here click on where and you connect all these diodes. Press escape. Now you add one voltage source. Go to component and write here voltage. You see that voltage already came. So click on it. So you will get the voltage. Escape. Now what you need, you need a transformer. So use this inductor to make a transformer. Actually there is no transformer here. So click on it. You need another inductor. Just rotate it by CTRL plus R twice. And this is inductor 2. Keep it there and press escape. Now just click on this move tool to just orientation properly. Ok, next you click on escape and Connect this to inductor to make a transformer. To make a connection to couple this to inductor, you just click on the SPICE directive and write a one line code that is K for coupling L1. K basically indicates the coupling coefficient space L2, L1 and L2 are basically name of our inductors space 1. 1 indicates that as if there is no leakage loss. So K value of of the coupling coefficient generally from 0 to 1, 1 is the ideal situation, there is no leakage that we are considering. Click OK and if you click it here, you see that these two dots indicates that these two are now coupled. Next what we require, we require a resistor, so click on a resistor, press escape and Now you just connect all this with the help of wire. So take connection from here. Then connect all these and press escape so all the connections we have made now finally what we do we just assign the values right click on the voltage click on advance choose sine wave Let us consider this offset is 0, amplitude is say 230 volt is the power source and frequency is say 50 hertz. And the series resistance here you just put say 0.1 milli ohm. So 0.1 m, m corresponds to milli. Ohm is already there. Okay. So we have assigned it. So using the move tool, you just shift it there. Okay. Then you just assign the values of the press escape and assign the values of the inductors. Suppose we want the turn ratio of say 10 is to 1 in the transformer. Okay. We want to step down. by 10 times so 230 volt at the secondary it will become 23 volt okay so for a 10 trans ratio we have to use the inductor ratio square of that that you have to remember okay so remember inductor ratio will be square of the turns ratio so what we do right click here in l1 and put the inductance value is say 10 micro henry 10 u u corresponds to micron micro henry and here in l1 you just put say 0.1 so here is just observe that what we have used is that ratio of the these two is 100 that means the square root of that is basically the trans ratio so 10 is to 0.1 that means 100 is to 1 that means 10 is to 1 is the ratio now you go to the resistor and click right click and put the resistor value as 1 kilo ohm so ohm is already there right 1k press ok and you just uh make two grounds here you just make it ground and ground these two places Okay, so we have given all the values. Now in the simulate, go to the end simulation. And then here you give the stopping time say 50 milliseconds. For 50 milliseconds, suppose we want to observe, click OK. And now click on run. And let us see the simulation. So here you can see first if we want to see what is the input voltage so click on it here this probe is connected here and if you click on it you will get the input voltage. So now if you want to see just add another plane and there suppose we want to see the output. You see the output is like this. Okay. And here you can see if you click on it, you see that what is the voltage. You see the voltage is 224. It is expected to be 230 but 224 certain losses because of this resistance and all that. Okay. Here if you click on it, you see what is the maximum voltage you are getting at the output. you are getting okay at the output you are getting around 21 volt okay around 21 volt so 21 volt it is expected to be 23 volt okay some losses already taken place so 23 volt then through the diode some voltage is also lost around points 7 volt per diode. So for a particular direction it is two diodes will operate at the same time so around 1.5 volt will be less. So around 21 volt you are getting at the output the peak one and you can see lot of ripples are there. Now suppose you want to change it, you want to put some capacitor here and you want to see that what is the effect. just put the capacitor press escape connect the wire press escape so now you just give some value to the capacitor say 10 micro farad okay so now let us see that how the uh how the ripples will change so click on run and you see now the ripples are like this so as expected okay this is the discharging this is the charging and now you can also play with the capacitance value and you can see that instead of 10 microfarad if you put say 100 microfarad then what is the effect click on ok and click on run and then click on run and then click on run You see now the output voltage is much much smoother. So at the output with the help of large value of capacitance you can see you can get a smooth output voltage. So these characteristic curves their magnitudes and everything that we actually see in the oscilloscope here with the help of this simulator also we can see all these things. Thank you.

Physically diode look like this as you can see here. One end you see it is a silvery color and other end is black. The silvery color end is called cathode that means that end remember you have to connect with the negative end of the power source or you have to connect with the ground and other end you have to connect with the positive end of the power source or some other power source is there.

So, this is the way by which if you connect a diode then current will flow through the diode in this direction and diode is called that it is in a forward biased condition. But if you just connect it in a opposite way that means if you connect this end with the negative power source and this end with the positive one then there will be a negative no current through the diode. So here you can see there is a battery and this is the positive end and you see this positive end is connected to the anode part and the negative end is connected to the cathode part through this LED.

That is why it is okay and the LED is glowing. Similarly here you can see this cathode part is connected to the negative that is okay and definitely this anode part is connected to the positive with this load. that is why the LED is glowing. But if you see here, you see that cathode part is connected to the positive end of the battery. That means it is in a reverse bias.

So, there will be no current flowing through the diode and that is why you can see it is not glowing. Similarly, if you observe this connection, it is again in a reverse bias condition and that is why the LED is not glowing. So, what is the use of diode? Diode is used in a circuit as a switch. Now see this particular component resistor.

It is very common component and remember that resistor is mostly used component in the electronic circuits. and here you can see there are different kinds of resistor depending upon their specification different types of color bands are there and depending upon the number of color bands they are also categorized and this color bands actually give the specification of the resistor that what is the magnitude of its resistance okay so let us see that how with the color bands we can identify the resistance let us take one example here you can see there are four this is a four band resistor where this is the first band the first band is brown color so where is the brown in this column here is the brown so brown in if it is in the first band then it is one So you just put 1. Then what is the second color? That is black. So go to the black color in the second band. That corresponds to 0. So just put 0. Then what is the third one?

That is yellow. So go to the yellow and corresponding to third you see this is a multiplier. So it is a multiplier 10 kilo ohm. So multiply 10 kilo ohm. that means this resistor magnitude is this so 10 into 10 kilo ohm that means 100 kilo ohm this is what is the resistance and what is this fourth band the fourth band indicates the tolerance here You can see the fourth band indicates the tolerance that if you what is this if this is golden you see that it is a 5% tolerance that means this magnitude that is the specification of the resistance it may vary plus minus 5%.

is the meaning of the tolerance. So, what is the use of the resistor? Resistors are used in a circuit, so that if in a component, if the current is limited and if you want to reduce that current, so that the component will not damage, in that case what we do, we connect a resistor in series with that component, so that the current value decreases and that component will not damage.

Now, another very important component is the resistor, sorry, capacitor and you can see commonly used capacitors in the electronic circuits are this ceramic capacitor, electrolytic capacitor. Ceramic capacitor, as you can see, they are non-cooperative. polarized that means there is no cathode or anode you can connect with any one of them and here in electrolytic capacitor you can see that there is one anode and one cathode and cathode you can always identify through the this black color line okay so that remember is the cathode and you have to connect with the negative side of the source so capacitor the use of the capacitor remember capacitor tries to smoothen the voltage in a circuit so this is the main function of the capacitor though there are other functions like starting of a motor and all that but basically we are going to explore this particular application of the capacitor that it smoothen the voltage Here you see the LED or the light emitting diode and again you see that it has a cathode and anode legs and you see that cathode is the shorter one and anode is the longer one. This is the way physically you have to understand that which one is anode and which one is cathode.

Now remember the shorter one is the cathode. Another way you can see that it is actually circular but one end is bend like this. That means.

means a flat end is there and this flat end corresponding to the cathode side okay so if this flat end is there in an led you will understand that that corresponding to that leg is basically the cathode and the other one is anode because sometimes the legs are almost similar it is difficult to identify the which one is longer so in that case this flat surface always indicates the cathode okay here you can see that with a three volt battery this led is connected and you can see the anode the longer one is connected with the positive and the shorter one which is the cathode is connected with the negative so it is glowing but here you can see when you connect this led with a 6 volt then you see a resistance is connected in a series the reason is very simple because the current limit of the led is in the order of say 20 25 milliampere okay So, if the current is more than 20 milliampere through this LED, then this LED will burn. So, you cannot allow more than 20 milliampere. So, if you connect a larger voltage, definitely larger current will pass through this LED.

to avoid the damage what we do we connect the resistor if you connect the resistor in series then definitely the current that is flowing in the circuit will be reduced and the current through this LED will be below this 20 20 milliampere. So, the LED is not going to burn even if you are connected with a 6 volt. So, definitely if you want to connect it with a 12 volt, the amount of resistance that is required to save this LED will be more. LED can be used as indicator in many circuits. Now coming to the transistor.

Transistor is a very very important component and as you can see physically they look like this and it has three legs you can see 1, 2, 3 and these three legs corresponding to its base. emitter and collector. So by controlling this base basically you can change this collector current.

So if you put that zero voltage in the base then you will get zero. current in the collector. So basically this base is kind of a control valve by which you can control the collector current.

So if you increase the base voltage then the current will also increase in the collector. So the idea if you can compare with a water flow analogy suppose this is a tank Water is there and there is a valve connected with this pipe and there is a tap through which the water is coming out. So here this tap where from you are getting the water is basically the collector. So this is kind of an output that you are getting in the collector and this tank where some water is there is like an emitter. Okay, and the valve that is connected in the pipe by controlling that valve you can actually control at the output right collector.

So this valve is like base. Okay, so by controlling the base basically you are getting the collector. output okay so if you put the zero base voltage then you will get no output so transistors can also be act as a switch or transistor can also be acts as amplifier because by controlling base you can increase the collector current also okay so these are the application of the transistors but in this lecture i am not going to explain the details of how transistor works and all that okay Okay, here you see another very important component that is breadboard. If you look at the construction of the breadboard, there are two channels at the top and there are two channels at the bottom. This top and bottom channels are called the power lines.

lines these are called power lines here you can see one power line is shown here that red and blue and this red all these points all these holes they are internally connected by the conductor So, that means if through which if you give 5 volt here say if you give 5 volt here then if you draw something from here you will get 5 volt because all these are connected internally along the horizontal direction. So, along this direction they are connected similarly along this direction they are connected. So, this is true for this top 2 and the bottom 2 these are called power lines.

Similarly here you see if you the connection these are called the component lines. here the connection is like this they are not along the length they are connected they are connected along this okay but these two are not connected they are connected along this way okay similarly they are connected along this way in this region but there is no connection between E and F okay so this is the internal connection of the breadboard what is the use of breadboard breadboard is used to hold the different electric components and since because of its own internal connections a lot of much wear connections are not required you can avoid lot of wears to connecting different parts Now, coming to the rectifier, what is rectifier? Rectifier is a device by which we can convert alternating current into direct current. This is the simple definition of what is rectifier. So, rectifier is a device by which AC can be converted into DC.

Now what are the different types of rectifier? The different types of rectifiers it can be half wave rectifier or it can be full wave rectifier. Again full wave rectifiers can be center tap rectifier as you can see here or it can be bridge rectifier. Remember bridge rectifier is also a full wave rectifier. So both these are full wave rectifier.

Here this is basically the center tap rectifier that has been shown and the bridge rectifier that we will see in the next page. So first you see what is the half wave rectifier. So here in the half wave rectifier you can see in the circuit only one diode has been used.

In a center tap rectifier you will find it is full wave rectifier that is produced with the help of two diodes. And in a bridge rectifier you will find you require the four diodes to make a full wave rectifier. Now you see that how it works. Let us consider at a particular half cycle here is the AC input.

You can see this one is the transformer and then this is the resistor where you are getting the output. Now here let us consider at a half cycle here it is plus and here it is minus and at that time this diode is in forward bias. So current will flow in this direction. So, in this way the circuit will be completed.

So, you will get current in the half cycle, but since it is AC cycle in the next half cycle. the direction of the current will change so this end will become negative and say this will become positive at that time when it will become negative you see this diode will be in a reverse bias so there will be no current flow through this diode and that is why the you will do not get any current at the output. But again when this will become positive then you will get current.

So, what will be the output? Output will be like this. In the first half cycle you will get current.

Then you do not get any current. Then in the next half next half cycle you will get current then you do not get any current so in this way at the output you are getting dc voltage that is ok but you are getting half wave rectification not the full wave you ok so this is what is called the half wave rectification now coming to the full wave rectification you see here there is one connection where full wave rectification has been shown where there is a transformer let us consider for the first half cycle what what is happening. So, first half cycle let us consider this is plus, this is minus, this end is plus and this end is say minus.

Now, what will happen in the first half cycle, this is plus. So, this diode will be in a forward bias. So, current will flow in this direction.

So, here you can see the direction of current across the load. so this is the circuit and at that time you see this is negative so there will be no current flowing through this diode because this diode is in a reverse bias condition now consider in the next half cycle what will happen the next half cycle definitely the sign will change if the sign changes then what will happen suppose at that time this will become negative this part will become positive this part will become negative and this part will become positive now you see this is negative that is why this diode is in reverse bias okay but this is positive so this diode is now in forward bias so what will happen so current will flow in this way and you see in the both half cycle the current is flowing through the load in the same direction so you are getting a dc okay so you are getting a dc current in the both half cycle So, at the output, you will get this kind of a full wave rectification. Here it is the voltage and here it is the time. But this is called a center tap rectifier. There is a chance of leakage if there is a potential difference occurs between these two.

So, this is not so efficient as the bridge rectifier is. So, bridge rectifier is the most efficient. one for the rectification purpose now we will see that how bridge rectifier works so this is what is the circuit of a bridge rectifier here you can see the transformer here the high voltage ac source is there and And that becomes the low voltage with the transformer ratio.

Let us consider for a half cycle, this portion is positive and this portion is negative. Then what will happen? That current will flow in this direction.

And you see this is in a forward bias condition. So current will flow. And here is basically your resistance or output you are measuring here. So this is what is the direction of current.

and it will go in this way and complete the circuit. Now, consider the next half cycle what will happen. Next half cycle this will become negative and this will become positive. At that time you see that when this end, if you consider from this end that current will flow in this direction and this is in a forward bias. So, current will flow in this direction and again you see it is going through the load in the same direction.

So, it is DC. And you see it is in a forward bias. So in this way the loop will be completed. So what we will get?

We will get this kind of a DC full wave rectification across the load. But there is a problem. The problem is we are getting full wave rectification.

We are getting DC voltage. That is okay. But the problem is there is lot of ripples.

there right because ah we want this kind of a dc voltage that is voltage is constant same throughout the time so then that will be better definitely this kind of ripples are not intended so what we can do to what all these ripples how can we reduce these ripples okay to reduce this we use the capacitor as you know the capacitor is used in a circuit to smoothen the voltage so with the help of capacitor we will try to get this kind of a circuit. Let us see, here you can see with the load one capacitor is connected in parallel and when the capacitor is connected in parallel, if you see the output that that output actually shown in this diagram with a black line. This black line is showing the output when the capacitor is there and the dotted purple line which is showing basically if there was no capacitor. So, if there was no capacitor you can see that there were lot of ripples present, but when there is capacitor present then the ripples are not there and here you can see this kind of. output voltage you are going to get respectively smoother voltage what is actually happening you see that this region that i am showing here with the red line is basically the capacitor at that time is discharging let us consider the capacitor is charged in this region and then what happens that when this voltage here is gradually going down that means here the voltage is gradually going down this then the capacitor which is already charged is now discharge and since it will discharge it will try to keep up the voltage it will not allow to voltage to go down so in this way the main intention of the capacitor when capacitor is present it will always try to keep the same voltage so that is why during that period capacitor will not allow to fall the voltage here at the output so capacitor will itself discharge and and try to maintain the voltage.

But after the full discharge of the capacitor, then again capacitor will charge and this is what is the charging period. Then again capacitor will discharge and try to maintain the voltage. So voltage will not fall down like this. So in this way by discharging and charging the capacitor is trying to smoothen the voltage there.

Now here you can see this simple circuit that here some source AC is there, here this is showing the transformer, here you can see this like 9 is to 1 kind of a ratio is there. The important thing that you try to observe here is this is what is the diode. You see this is one diode, these are the physical diodes you see in the circuit.

These are the four diodes present which are connected according to a bridge rectifier that you have seen. Here you can see the capacitor is connected in parallel and here you can see that output the resistance. is present in the form of an LED. So this is what is the bridge rectification circuit and it is connected with some oscilloscope and in oscilloscope we can see the characteristics of the voltage that we have just explained that we will be able to see. Suppose this capacitor when it is not connected when the capacitor is not there at that time what we you will see first of all let us consider if you put the probe of the oscilloscope here here it is the input so what you will you are going to get you are going to get probably this kind of a AC supply that is what is the input now when the capacitor is not there, when the capacitor is not present, let us consider, at that time, if you put the probe here, of the, then what you will see?

You will see may be this kind of a, ripple pulsating DC. So now if you add the capacitor, then what you will see? If you add the capacitor, then you will see.

this kind of a respectively smoother voltage okay so this is what is the characteristics that we generally observe in oscilloscope here what we are going to do that in a simulator we want to see these characteristics okay so for this simulation we are going to use that lt spice okay so you can easily download this lt spice from the net and install it in your computer and you can do this simulation now let me show you how can we make the circuit in the lt spice platform so this is the lt spice platform you can see go to the file click on new schematic Then you choose the different components that you require. Here is the component. If you click on it, you will get the different components. Here you can see the diode, inductor, capacitor, resistors also all are there.

So diode we require four diodes. So just click on it and you just rotate it to rotate the diode orientation. You press control plus R. okay now you just click you need four diodes so click four times one two three four then you just press escape okay so now what you have to do you just connect all these diodes with the help of where here click on where and you connect all these diodes.

Press escape. Now you add one voltage source. Go to component and write here voltage.

You see that voltage already came. So click on it. So you will get the voltage.

Escape. Now what you need, you need a transformer. So use this inductor to make a transformer.

Actually there is no transformer here. So click on it. You need another inductor.

Just rotate it by CTRL plus R twice. And this is inductor 2. Keep it there and press escape. Now just click on this move tool to just orientation properly. Ok, next you click on escape and Connect this to inductor to make a transformer. To make a connection to couple this to inductor, you just click on the SPICE directive and write a one line code that is K for coupling L1.

K basically indicates the coupling coefficient space L2, L1 and L2 are basically name of our inductors space 1. 1 indicates that as if there is no leakage loss. So K value of of the coupling coefficient generally from 0 to 1, 1 is the ideal situation, there is no leakage that we are considering. Click OK and if you click it here, you see that these two dots indicates that these two are now coupled.

Next what we require, we require a resistor, so click on a resistor, press escape and Now you just connect all this with the help of wire. So take connection from here. Then connect all these and press escape so all the connections we have made now finally what we do we just assign the values right click on the voltage click on advance choose sine wave Let us consider this offset is 0, amplitude is say 230 volt is the power source and frequency is say 50 hertz.

And the series resistance here you just put say 0.1 milli ohm. So 0.1 m, m corresponds to milli. Ohm is already there.

Okay. So we have assigned it. So using the move tool, you just shift it there. Okay. Then you just assign the values of the press escape and assign the values of the inductors.

Suppose we want the turn ratio of say 10 is to 1 in the transformer. Okay. We want to step down. by 10 times so 230 volt at the secondary it will become 23 volt okay so for a 10 trans ratio we have to use the inductor ratio square of that that you have to remember okay so remember inductor ratio will be square of the turns ratio so what we do right click here in l1 and put the inductance value is say 10 micro henry 10 u u corresponds to micron micro henry and here in l1 you just put say 0.1 so here is just observe that what we have used is that ratio of the these two is 100 that means the square root of that is basically the trans ratio so 10 is to 0.1 that means 100 is to 1 that means 10 is to 1 is the ratio now you go to the resistor and click right click and put the resistor value as 1 kilo ohm so ohm is already there right 1k press ok and you just uh make two grounds here you just make it ground and ground these two places Okay, so we have given all the values.

Now in the simulate, go to the end simulation. And then here you give the stopping time say 50 milliseconds. For 50 milliseconds, suppose we want to observe, click OK. And now click on run. And let us see the simulation.

So here you can see first if we want to see what is the input voltage so click on it here this probe is connected here and if you click on it you will get the input voltage. So now if you want to see just add another plane and there suppose we want to see the output. You see the output is like this.

Okay. And here you can see if you click on it, you see that what is the voltage. You see the voltage is 224. It is expected to be 230 but 224 certain losses because of this resistance and all that.

Okay. Here if you click on it, you see what is the maximum voltage you are getting at the output. you are getting okay at the output you are getting around 21 volt okay around 21 volt so 21 volt it is expected to be 23 volt okay some losses already taken place so 23 volt then through the diode some voltage is also lost around points 7 volt per diode.

So for a particular direction it is two diodes will operate at the same time so around 1.5 volt will be less. So around 21 volt you are getting at the output the peak one and you can see lot of ripples are there. Now suppose you want to change it, you want to put some capacitor here and you want to see that what is the effect. just put the capacitor press escape connect the wire press escape so now you just give some value to the capacitor say 10 micro farad okay so now let us see that how the uh how the ripples will change so click on run and you see now the ripples are like this so as expected okay this is the discharging this is the charging and now you can also play with the capacitance value and you can see that instead of 10 microfarad if you put say 100 microfarad then what is the effect click on ok and click on run and then click on run and then click on run You see now the output voltage is much much smoother. So at the output with the help of large value of capacitance you can see you can get a smooth output voltage.

So these characteristic curves their magnitudes and everything that we actually see in the oscilloscope here with the help of this simulator also we can see all these things. Thank you.

Transcript for:Basics of Electronic Components and Rectifiers

Transcript for:
Basics of Electronic Components and Rectifiers