Question

A battery charger with a series resistor is somewhat like a half-wave rectifier. Explain its operation.

Answer 1

Half Wave Rectifiers

A rectifier is a device that converts alternating current (AC) to direct current (DC). It is done by using a diode or a group of diodes. We know that the diode permits current only in one direction and blocks the current in the other. We will use this principle to construct various rectifiers.
By the no. of diodes used, we can classify rectifiers into two types:

Half-Wave Rectifier
Full-Wave Rectifier

Half Wave Rectifier

Half wave rectifier is the simplest form of rectifiers available. Half-wave rectifier will allow only one half-cycle (positive or negative half-cycle) of the AC voltage through and will block the other half-cycle. We only need one diode to construct a half-wave rectifier.

Construction of Half Wave Rectifier

A half-wave rectifier system consists of:

Transformer (Step-down)
Diode
Resistive Load

Working Principle of Half Wave Rectifier

We will apply a high AC voltage to the primary side of the step-down transformer and we will get a low voltage at the secondary winding which will be applied to the diode.During the positive half cycle of the AC voltage, the diode will be forward biased and the current flows through the diode. During the negative half cycle of the AC voltage, the diode will be reverse biased and the flow of current will be blocked. The output voltage waveform will be as above.We can classify the half-wave rectifier into two types based on the waveforms allowed:

Positive Half Wave Rectifier

Positive half-wave rectifier will allow positive half-cycles through the diode and will block the negative half-cycle.

Negative Half Wave Rectifier

Negative half-wave rectifier will allow negative half-cycles through the diode and will block positive half-cycle

Advantages of half Wave Rectifier

Due to the less no. of components used, they are cheaper to setup and construct.

Disadvantage of Half Wave Rectifier

The half-wave rectifier only allows half-cycle through and the other half-cycle is wasted. This leads to power loss.
Produces low output voltage.
The output current we obtain is not purely DC and there are a lot of ripples in it.