Half Wave Rectifier
A Half wave rectifier is a Circuit which converts Ac voltages to Pulsating Dc Voltages. Let us Observe how this Half wave rectifier converts Ac voltages to Pulsating Dc, I have illustrated the process below: The process called half-wave rectification. and the circuit which performs this operation is called Half Wave Rectifier.
Note that A diode is connected to an ac source and to the load resistor, that makes a half-wave rectifier. here all ground symbols represent the same point electrically. Let’s examine that what happens during one cycle of the input voltage using the ideal model for the diode. When the alternating input voltage (Vin) goes positive (during Positive Cycle), the diode is forward-biased and conducts current through the load resistor, as shown in part (a). The current which makes an output voltage across the load resistor which is RL, which has the same shape as the +ve half-cycle of the input voltage as you can verify see below.
Now see here when the input voltage goes -ve during the second half of its cycle, the diode is going in reverse-bias. There is no current there, so the voltage across the load resistor (RL) is 0V or at the ground, as shown in Figure (b).
The final result is that only the +ve half-cycles of the ac I/P voltage appear across the load. Since the output does not change polarity, it is a pulsating dc voltage in nature with a frequency of 60Hz (here we are using 60Hz that does not matter you can use 50Hz as well), as shown in part (c).
Average Value of the Half-Wave Rectifier Output Voltage
The average value of the half-wave rectified output voltage is the value you would measure on a dc voltmeter. Mathematically, it is determined by finding the area under the curve over a full cycle, as illustrated in Figure given below, and then dividing by the number of radians in a full cycle. The result of this is expressed in given Equation, where Vp is the peak value of the voltage. This equation shows that Average value of Half Wave Rectifier Output voltage is approximately 31.8%.
Effect of the Barrier Potential on the Half-Wave Rectifier Output
As we discussed, the diode was considered an ideal one. When the practical diode model is used with the barrier potential of 0.7 V( Silicon Diode) taken into account, this is what happens. During the +ve half-cycle, the input voltage must overcome the barrier potential before the diode becomes forward-biased. This results in a half-wave output with a peak value that is 0.7 V less than the peak value of the input, as shown in Figure given below. The expression of the peak output voltage is.It is usually more preferable to use the ideal diode model because it neglects the effect of the barrier potential when the peak value of the applied voltage is much greater than the barrier potential (at least 10V). However, we will use the practical model of a diode, taking the 0.7 V barrier potential into account unless stated otherwise.
Peak Inverse Voltage (PIV) of Half Wave Rectifier
The peak inverse voltage (PIV) it’s it maximum possible voltage the diode has to withstand, or the diode must be capable of withstanding this amount of continuous reverse voltage. For the diode in Figure given Below, A diode should be rated at least 20% higher than the PIV.
Practical Applications of Half Wave Rectifier
- . Half Wave Rectifier can be used to obtain the desired level of dc voltage by using Step up or Step down Transformer.
- It is used in soldering iron, Soldering Iron circuit uses Half Wave rectifier and it is also used in mosquito repellent to drive the led.
- A half wave rectifier is mostly used as an detector in an AM radio, where the output is not only DC, but an audio signal. The current is so small that there is no advantage to a more complex rectifier.
- A Half Wave Rectifier is used in pulse generator circuits,firing circuits.