An electronic device which converts A.C power into D.C power is called a rectifier.
TYPES OF RECTIFIER
It is of two types:
1. Half wave Rectifier (H.W.R)
2. Full wave Rectifier (F.W.R)
HALF WAVE RECTIFIER (H.W.R)
Rectifier which converts only one half of A.C into D.C is called half wave Rectifier.
FULL WAVE RECTIFIER (F.W.R)
Rectifier which converts both halves of A.C into D.C is called full wave Rectifier.
HALF WAVE RECTIFIER
In a half wave rectifier, we utilize only one half cycle of the input wave these are the circuits which convert an A.C voltage into D.C voltage.
Its principle is based on the fact that the resistance of p-n junction becomes low when forward baised and becomes high when reverse baised.
The A.C supply is fed across the primary coil P of the second step down transformer. The two ends of the secondary coil S of the transformer are connected to the P-Sections of the junctions diode D1 and D2. A load resistance Rc is connected across the n sections of the two diodes and the central tapping of the secondary coil. The D.C output will be obtained across the load resistance Rl.
Suppose that during first half of the input cycle. Upper end of the coil S is at-ive potential and the lower end is at-ive potential. The junction diode D1 will get forwarded baised, while the diode D2 reverse baised. The conventional current due to the diode D1 will flow along the path of full arrows.
When the second half of the input cycle comes the situation will be exactly reverse. Now, the junction diode D2 willl conduct and the conventional current willl flow along the path of the dotted arrows. Since current during both the half cycles flows from right to left through the load resistance RL the output during both half cycles will be of the same nature. The right end of the load resistance RL will be at tive potential W.R.T it left end. As discussed in case of half wave rectifier, the magnitude of output across RL at any time will vary in accordance with the A.C input.
A.C to be rectifier is connected to the primary P1P2 of a stepdown transformer. S1S2 is the secondary coil of the same transformer. S1 is connected to the portion p of the p-n junction. S2 is connected to the portion n through load resistance R. output is taken across the load resistance R.
During positive half cycle of input A.C
Suppose P1 is negative and P2 is positive on account of induction, S1 becomes positive, S2 becomes negative the p-n junction become low. The resistance of p-n junction become low the forwarded current flows in the direction shown by arrow heads. Thus we get output across load.
During Negative half cycle of input A.C
P1 is positive and P2 is negative on account of mutual induction, S1 becomes negative and S2 is positive the p-n junction is reverse baised. It offers high resistance and hence there is no flow of current and thus no output across load the process is repeated. In the output, we have current corresponding to one half of the wave, the other half is missing.
That is why the process is called half wave rectification. It is not of much use the output signal is available is burst and not continuously.