Every electronics circuit needs DC source to be operated . Full wave rectifier or a battery is good source of DC Power.
If we represent AC Voltage using time graph, then you can see voltage sign wave. You can see two half cycle. Upper part is called “Positive Half Cycle” and “Lower Part” is called Negative Half Cycle. So it is called Alternate current.
Why Electronics Devices operates in DC not In AC?
Because most of electronics component are made of semiconductor, which need particular polarity to turn on or off. Also Digital electronics are completely based on 0 and 1, means switch on and off. If we provide AC to electronics circuits, because of alternate polarity circuits will very frequently switch on and off, and digital logic won’t be work. Don’t be so much confuse, as you will learn more, it will clear.
Why we need diode, why not other components?
Diode have one property, current can flow through diode only if, positive voltage is applied at Anode of diode and negative voltage is applied on cathode of diode, If you reverse the polarity current cant flow. So this property of diode can be used to convert AC to DC, Let’s Learn How.
Let’s Connect One Diode to ac power source and see what happens
As you can see, one diode is connected to AC power source and the output waveform is like shown in blue signal.
You can see, when positive half cycle of AC waveform comes, Diode get forward bias and when –ve half cycle of diode comes, diode did not get forward bias, so –ve half cycle is absent in the output. Only positive half cycle is present. Interesting right?
The Above circuit is called half wave rectifier, as it only pass half cycle of AC waveform.
But DC means, there is no sinusoidal signal, it should be pure fully rectified. For that we have to use full wave rectifier.
Full wave rectifier looks like above circuit. You can see there are 4 diode connected in bridge.
When first half cycle comes thought this circuit, Diode D1 and D2 gets forward bias. Current flows like D1 — > Load — >D2 and positive half cycle appears in the output circuit.
When –ve half cycle of AC signal comes through this circuit Diode D3 and D4 gets forward bias
Current flow in the above circuit will be like D4 — > Load — > D3 and other half cycle appear in the output side. Thus both the half cycle is appeared , it is somehow closed to DC signal but not pure DC.
For that we have to use another component. As we know the property of capacitor is store charge and discharge slowly when needed. We will use this property to smooth the output.
In the output side of Full Wave Rectifier we had added one capacitor, parallel to load.
When positive half cycle comes in the output, capacitor charges and when capacitor starts to discharge through the load, within that time period, the next half cycle comes and capacitor gets charged again.
So there is no time for capacitor to fully discharge against load. Charging and discharging of capacitor makes the output voltage steady and smooth rather than semi sinusoidal signal as shown in above figure.
If we will present this on the graph it will be pure DC.
Hope You like this tutorial, If you have any doubt or any mistake in this article please comment down below.