Read what rectification is and the purpose of rectifiers in any circuit. Learn more about them by its categories, their differences and its...
This image shows a basic circuit setup with the inclusion of a diode rectifier. This device will prevent the backwards flow of electrical current through the circuit.
A rectifier is the particular device that performs the rectification. Rectifiers force AC currents to behave as DC currents by only allowing a one-directional flow of electricity. Instead of allowing these AC currents to switch directions, they are essentially pushed into one. This is possible by using diodes, which are electrical parts with differing amounts of resistance on both sides. The differences in resistance create two possible paths and outcomes for the current when it passes through the circuit. Resistance is a property of certain materials that prevents the flow of an electrical current by making it difficult for it to pass through. This is similar to insulating material in a building, preventing heat loss. Some common examples of rectifiers include the diode tubes in vacuum cleaners, mercury-arc valves, junction diodes, solid-state diodes, and receivers in radio systems.
This gif shows a bridge rectifier with an alternating current passing through the circuit. As the current switches from the positive to the negative aspects of the cycle, it enters different diodes, shown by the alternating blue and red flashing routes.
When the electric current encounters the higher resistance side, it will have a much more difficult time trying to pass through and essentially be stopped entirely. This is compared to the side with lower resistance that doesn't prevent the flow of electricity. This dual setup forces the current to literally follow the path of least resistance, resulting in a rectified current that doesn't allow currents to flow backward or in different directions. Their inclusion in modern appliances is what makes them useful in creating a one-directional flow.
Diodes can have biases, or voltage preferences, based on their construction, and this determines when electricity flows. Diodes are said to be forward biased or reverse biased, depending on the situation. Diodes are forward biased when they allow the voltage to flow if it is positive. Alternatively, it is said to be reverse bias when it prevents the flow of a negative voltage.
There are two distinct types of rectifiers that can be used in electrical devices, controlled and uncontrolled. The notable difference between these two types is whether or not the voltage differential between the two poles of an electric current source can be controlled externally. As the names imply, controlled rectifiers are those where the voltage level can be manipulated, while uncontrolled rectifiers cannot. Voltage is an electrical property referring to the difference in potential between the two poles of an electric current source, i.e., the positive and negative ends of a battery. The higher the potential difference between the two ends, the higher the voltage.
Controlled rectifiers are created by adding semiconductor switches that allow for voltage regulation. These can include MOSFETS (metal-oxide-semiconductor field-effect transistor,) IBGTs (insulated-gate bipolar transistor,) and SCR silicon-controlled rectifier.)
There are two categories the types between controlled and uncontrolled rectifiers: half-wave and full-wave rectifiers. When referring to the type, uncontrolled rectifiers are simply called half-wave and full-wave rectifiers, but controlled rectifiers are further specified as half-wave controlled and full-wave controlled. The difference between these two categories here is which part of the electrical current cycle is utilized for output. Electrical currents propagate similar to waves, having both positive and negative aspects in their cycles, meaning the amplitude rises and dips below 0 as the current travels.
Half-wave rectifiers are named so because of their ability to convert part of an AC current into a direct current. These half-wave rectifiers include only one diode that will make use of the positive aspect of the cycle while blocking the negative side.
Unlike the half-wave, full-wave rectifiers can use the complete cycle of electrical currents, both positive and negative aspects. There are two methods to put together a full-wave rectifier, a bridge arrangement, and the center tap full-wave rectifier.
The center tap full-wave rectifier setup uses only two diodes and a central transformer. Because this is a full-wave rectifier, both positive and negative aspects of the voltage cycle will be utilized for the voltage output; however, only one diode is forward biased at a time. A single diode will be forward biased during the positive cycle, and the other will be reverse biased; these will switch when the cycle becomes negative.
The bridge rectifier arrangement utilizes four diodes to direct the flow of the current but does not utilize a transfer like the center tap rectifier. The four diodes are paired off, with only two diodes active at a given time, and assist with channeling AC current input into a DC current output. Two of the diodes are active during the positive part of the voltage cycle, and the other two are active during the negative part of the cycle. This means that at a given time, only two of the four diodes are forward biased while the other two are reverse biased.
Although both half-wave and full-wave rectifiers are useful in the conversion of AC currents to DC, they have different efficiencies and outputs. Half-wave rectifiers can only make use of half of the current cycle, while full-wave rectifiers use the complete cycle. Because only one-half of the wave is used in half-wave rectifiers, the output is not continuous because one-half of the wave output is blocked; this produces disruptions known as "ripples" and reported as the ripple factor for the type of rectifier. This causes the half-wave rectifiers to be less efficient than full-wave rectifiers. Full-wave rectifiers have twice as many waves to utilize for voltage output, and there are no ripples experienced; the output is continuous and undisrupted.
Types of Rectifiers Number of Diodes Ripple Factor Half-Wave Rectifiers 1 1.21 Center Tapped Full-Wave Rectifier 2 0.48 Bridge Rectifier Full-Wave 4 0.48In terms of cost, bridge rectifiers are cheaper to produce because they do not require a transformer. The transformers are also relatively large and can impact the device's overall size.
Because the voltage output of DC currents is steady and consistent, this is preferred for electrical devices to avoid loss of power and continuous usage. The purpose of rectifiers is to convert AC currents to DC currents and thus provide a steady voltage output for electrical devices and appliances. By using rectifiers, a wider range of electric currents can be used instead of only DC currents.
Some half-wave rectifiers are used in soldering equipment, AM radio waves demodulation, and detection. Full-wave bridge rectifiers are used in mobile phones, radios, and car alternators.
Rectification is the process of converting alternating currents into direct currents. Alternating currents (AC) are those that change their direction of flow numerous times within a given span of time, while direct currents (DC) keep a steady flow in only one direction. This process is accomplished by devices known as rectifiers, most often as diodes. Diodes are electrical components that have a notable difference in resistance on both sides. Resistance is the ability of a material to not allow electricity to flow through. Diodes make use of this by having one side with much higher resistance that discourages the flow of electrical current, while the other side has less resistance and encourages the current to flow in that direction. Diodes can be denoted as forward or reverse biased; forward biased means that the diode allows the flow of positive voltage, and reverse biased means that the diode prevents the flow of negative voltage. Voltage refers to the difference in potential between the two ends of a source.
There are two types of rectifiers, controlled and uncontrolled. An uncontrolled rectifier cannot control or moderate the voltage level, while a controlled rectifier can control the voltage level by using a semiconductor switch. The purpose of a rectifier is to control the flow of AC currents, forcing it in only one direction to behave like a DC current. Rectifiers can either be half-wave or full-wave, meaning they can take advantage of only the positive voltage-current (half-wave) or utilize both the positive and negative voltage of a cycle (full-wave.) Full-wave rectifiers provide a steady, uninterrupted voltage output for electrical devices, while half-wave rectifiers experience disruptions known as "ripples" when the negative voltage is blocked, reported as the ripple factor relating to the efficiency of that rectifier. Full-wave rectifiers can be further divided into center tap full rectifiers or bridge rectifiers. Half-wave rectifiers only use one diode, while center tapped full-wave rectifiers use two diodes and a transformer, and bridge rectifiers use four diodes that work in pairs. The two bridge rectifiers are more efficient, less expensive, and less bulky due to the absence of the transformer. Rectifiers are used in many common appliances and devices such as radios, soldering equipment, and mobile phones and are used in AM radio demodulation and detection.