 Hello everyone, welcome to this video lecture. Myself Deepali Vardkar, working as assistant professor at WIT Solapur. In this session, we will study half wave rectifier. These are the learning outcomes. At the end of this video lecture, student will be able to illustrate working of regulated power supply. Student will be able to examine working of half wave rectifier. And student will be able to examine the characteristic of half wave rectifier. Today almost all electronics device needs a DC supply for its smooth operation and they needs also power supply with its certain limit. This DC supply is derived from AC supply. The regulated power supply is used to convert unregulated AC supply into DC supply. So, the first block which is used in a regulated power supply that is the transformer. The transformer is used to increase or decrease the voltage level of input AC supply. So, in this example, this step down transformer is used which converts the high level AC voltage into low level AC voltage. Now the next block that is the rectifier. The rectifier it is the circuit which consists number of diodes which is used for the rectification purpose. So, the rectification means convert the AC signal that is the alternating current into DC quantity. So, there are basically two rectifiers full wave rectifier and half wave rectifier. In full wave rectifier, complete cycle of AC signal is get converted into pulsating DC. In half wave rectifier, only half cycle of input AC signal is get converted into pulsating DC. The output of rectifier is not pure DC. It consists repulse. So, these repulse are removed by using the filter circuit. So, number of filter circuits are used like capacitor filter, pi filter, choke filter, this block. So, this will the output after the filter circuit. Now, next block that is the regulator. In case of regulated power supply, sometimes there may be variation in input AC signal due to there are variation in AC mains or due to change in of temperature. So, regulator maintains the output constant even if there is a change in of input variations or even if there is a change in the input AC supply. In this session, we will study the rectifier circuit. The rectifier, it is electrical device that converts an alternating current into direct current by using one or more PN junction diodes. The types of rectifier, there are basically two types, half wave rectifier and full wave rectifier again divided into two types, center tapped rectifier and bridge rectifier. So, this is the half wave rectifier circuit. Here, the AC source provides the AC supply to the transformer. So, generally AC source is represented by the sinusoidal wave. In half wave rectifier, the step down transformer is used. For this transformer, number of terms for the primary winding is greater than number of terms of secondary winding. So, generally this step down transformer is used because here the diode which is used in this circuit that diode requires very low voltage as compared to input AC voltage. So, if the direct AC voltage is given to this diode, it will destroy permanently. So, that's why the high AC voltage is get converted into low level AC voltage by using the step down transformer. Now, the load resistance connected across it, this load resistance across it, the output is taken. In the series of the secondary winding, the diode is connected. Diode is two terminal device which allows the current only in one direction and blocks the current in another direction. So, now we'll see the working of half wave rectifier during the positive half cycle of input AC supply. So, this input AC supply is given to the primary of the transformer. Here the step down transformer is used. So, it converts the high voltage AC supply into low voltage AC supply where the frequency remains same. During the positive half cycle of this AC supply, the positive voltage is get applied to the anode of this diode and negative voltage is get applied to the cathode of this diode. So, in this condition diode becomes forward bias. So, in forward bias diode act as a closed switch. So, this is the equivalent circuit diagram for this condition. So, here the diode act as a closed switch. So, the current flows through this load and it is equivalent to the input AC supply. Now, next during the negative half cycle of input AC supply, this AC supply is applied to the primary of the, at the secondary the voltage level is decreases. During the negative half cycle of the AC supply, the negative voltage is get applied to the anode of this diode and positive voltage is applied to the cathode of this diode. So, in this condition diode act as a open switch. So, current flowing through this resistor is zero. So, current flowing through this load is zero. So, during the negative half cycle the output current is zero. So, these are the input output vapor. During the positive half cycle of input signal, the diode is on and current flows through the device or voltage present across the load. During the negative half cycle of input AC signal, the diode is off current flowing through the load is zero. So, voltage across that load is also zero. So, these are the output waveforms for a half wave rectifier. Now, the characteristic of half wave rectifier. So, first we will see the DC voltage which is appears across the load. So, if the peak voltage of this output waveform is Vm, then the DC voltage across the load is equal to V peak upon pi. That is equal to Vm upon pi. Next, the root mean square value. The root mean square value it is equal to V peak by 2. So, this is the root mean square value for the output of half wave rectifier which is equal to Vm upon 2. If Vm is the peak value of this waveform, then the root mean square value it becomes equal to Vm upon 2. Next, efficiency. The efficiency of half wave rectifier it is the ratio of DC output power to the AC input power. So, it is Pdc upon Pn. Efficiency for a half wave rectifier it is equal to 40.6. So, what indicate this 40.6 that is the half wave rectifier is capable to convert AC into DC only for 40.6%. Next, that is the ripple factor. It is defined as the amount of AC contained in a output DC. It is nothing but amount of AC noise in a output DC. So, the ripple factor for a half wave rectifier is equal to 1.21. The low ripple factor for a rectifier indicates its high performance. Next, peak inverse voltage it is defined as maximum voltage that diode can withstand in a reverse bias. So, in reverse bias the current flowing through the load resistance is 0. So, 0 voltage appears across the load resistance RL in reverse bias. So, entire voltage appears across this diode here. So, entire voltage that is the minus Vm voltage appears across the diode and that is nothing but peak inverse voltage. So, peak inverse voltage is it is equal to peak voltage that is the Vm. Next, transformer utilization factor transformer utilization factor is defined as the ratio of DC power which is delivered to load and AC rating of transformer secondary. So, for a half wave rectifier transformer utilization factor is equal to 0.287. Next, advantages. The advantages of half wave rectifier that is requires number of components very less. So, it is cheap and simple and it is easy to use. Now, question whether the output of half wave rectifier is pure DC. Pause the video for a while and think. So, this will come in a disadvantages that is the pulsating current in output contains AC component whose frequency is equal to supply frequency. So, filtering is needed. So, half wave rectifier in its outputs pulsating DC components are present. So, output of half wave rectifier is not pure DC. The AC supply delivers power during the half cycle only. So, output is low. These are the some references. Thank you.