Microprocessor Technology

Before we go any further, we will here make some review and introduction of electronic fundamentals, needed to completely understand what's going on inside computer, then we will start focusing on some of the specifics of what makes a computer operate, centered around the processor, which are made of millions of tiny semiconductor transistors today. So before we can get too far into our study of processors we need to take a look at the building blocks of those transistors, starting with the study of semiconductors.

We have seen earlier that resistor represents the friction component. The inductor and the capacitors represent the ability to take kinetic energy, in the form of electrical current, and store it as potential energy. In the capacitor, the potential energy is stored in an electric field. In the inductor, it’s stored in a magnetic field. The stored potential energy can then later be released back into electrical energy.
Making the mechanical comparison, energy is utilized either in kinetic (moving) form or potential form. For example, a spring at rest has no energy. As we push the ends of a spring together, we are putting kinetic energy into the spring. Once we have the spring completely compressed, it now has stopped moving and the energy is now in its potential form. Once we release the spring, the potential energy converts back to kinetic energy and the spring expands. Over time, some of the energy is lost by friction. The spring may lose some of its energy via friction to the air, to our hands, and to anything else it comes into contact with.

The Power Supply

All of the electronics inside of the computer (or most other consumer electronics) depend on the power supply. The power supply is responsible for converting, managing, and maintaining the power requirements of the machine.
Most consumer electronics make use of DC to provide power to their internal components. They need DC power because they rely on a constant flow of power in order to maintain the state they are operating in. Since AC power is constantly switching on and off it’s not suitable for powering many devices.
We already know that electrical power is distributed to end locations via AC. This presents a slight problem, and we must create DC from AC.
To create DC from AC, it must go through a conversion process known as rectification that converts AC into DC. In order to rectify, we need a new component - a diode.

Diodes

A diode is an electrical component that allows current to flow in only one direction. Later on, we will explain how a semiconductor diode works, when we will be talking about semiconductors; for now on, it is sufficient to know that current can only flow in one direction through the diode.

Half Wave Rectifier

The most basic diode rectifier is called a half-wave rectifier. In a half wave rectifier, current can only flow in one direction, so we can only produce a voltage in one direction. When the source voltage is positive, current can flow in the circuit and create a positive voltage on the resistor. When the source voltage goes negative, no current flows (the diode acts like an open circuit) and thus there is no voltage across the resistor. The interesting thing about this simple half-wave rectifier is that if we average the voltage over time, we get a positive value, which is not true with regular AC, as over time it always averages out to zero. Since the average value is not zero, a half-wave rectified AC voltage can also be viewed as a DC voltage (the average value) with a little bit of fluctuation (the AC part).

Full Wave Rectifier

Analyzing the idea of half wave rectifier further, we can create a full-wave rectifier. This circuit is made up of four diodes in a bridge configuration, which allows current to flow in alternating pairs of the diodes. No matter which part of the source AC voltage phase we are in, the current through the resistor is always flowing in the same direction. This means that our output voltage is always going to be positive. With full wave rectification, we are able to transmit the whole portion of the wave to the other side of the bridge. This new rectified voltage, much like its half wave counterpart, also has a positive average value. This means that a full wave rectified voltage can also be thought of as a DC voltage that fluctuates a little bit. The averaged voltage of a full wave rectified circuit is twice as much as its half wave counterpart.
By removing the negative part of the AC voltage we’ve created a new voltage that, over time, has a positive average value. In effect, we’ve created a DC voltage that fluctuates. The amount of fluctuation is known as the ripple voltage.

Full wave rectifier can even be better with adding a capacitor at the output, parallel to the resistor.
The capacitor attempts to maintain a constant voltage. It does this by storing charge inside of itself, and when the voltage starts to change it uses this excess charge to try and make up for the difference - keeping the voltage constant. We can think of it like a little battery that doesn’t have a very long life. However, before the capacitor loses all of its stored charge, the source voltage waveform returns and the capacitor is recharged again.

As shown above, there is still some small ripple in the output voltage. However, it is significantly less than without the smoothing capacitor. So, in conclusion, the use of a diode bridge and capacitors are all that we need to rectify AC into DC.