What Are the Types of Rectifiers and Diodes Used in Aircraft?

A rectifier is an electronic device that converts the power generated by an engine, APU, or Ground Power Unit (GPU), typically, 120V AC to 28V DC power for various electrical components available in aircraft. The most common type of rectifiers used in aircraft are dry disk rectifiers and solid-state rectifiers. As commonly used rectifying methods in modern aircraft are half-wave and full-wave, we will be looking at these particular methods in more detail to better understand how they compare and contrast.

Half-Wave Rectifier

A half-wave rectifier is an excellent choice for converting AC signals to DC signals through the use of a reverse-biased diode. However, because the construction of half-wave rectifiers is relatively simple, they are typically less efficient when compared to full-wave rectifiers. Additionally, the maximum efficiency of a half-wave rectifier is roughly 40.5%.

Due to the fact that half-wave rectifiers utilize only one diode, and considering that diodes only carry current in one direction, they are called half-wave rectifiers. While they may also face some irregularities when passing half an AC signal, a capacitor should always be used to smooth out any rectified signals. In addition, half-wave rectifiers a part of a circuit should always consist of the following componen

A diode
A transformer
A resistive load

Full-Wave Rectifier

As diodes allow current to only flow in a positive direction, a full-wave rectifier converts an AC signal into a DC signal by rectifying the negative value of an input voltage into a positive voltage using a diode bridge configuration. Then, the capacitor is charged/discharged to smooth out any fluctuations in voltage. This process results in a smooth DC signal. However, ripple voltage may still be present afterwards due to its dependence on the capacitor's capacitance and load. When using a full-wave rectifier, the amount of ripple voltage is typically smaller than with half-wave rectifiers. Meaning, the less a power supply fluctuates, the more it can lead to better stability and performance in your device.

Full-wave rectifiers are created in two ways: by using a center-tapped transformer and two diodes or by using a standard transformer and four diodes arranged as a bridge. Their only drawback is that they require more components than half-wave rectifiers, making them costlier to use.

Diodes

Diodes are often used to convert AC current to DC current, and vice versa. A rectifier diode is the electrical equivalent of a one-way valve; it allows current flow in only one direction. As a result, a diode can be forward-biased when conducting, and reversed-biased when opposing current flow. In a circuit, this means that a diode can offer a range of resistances to current flow.

Power Rectifier Diodes: This diode is crucial in many applications, such as power supply equipment. The range of current it can handle varies anywhere from 1 to 100 amperes, with an average peak voltage between 50-1000 volts.

Zener Diodes: Zener diodes are a semiconductor specifically designed to allow current to flow "backward" when a specific set voltage, known as the Zener, is reached. Depending on this diode’s design, the reverse voltage range can be anywhere between 2 volts to 200 volts.

Light-Emitting Diode (LED): In LEDs, energy is used with elements like gallium, arsenic, and phosphorus to radiate colors such as red, green, yellow, blue, and infrared light. These diodes are useful for instruments, indicators, and even cabin lighting. Moreover, LEDs typically have longer lifespans than the aforementioned diodes, require less voltage for faster on/off operations, and release less heat.

Conclusion

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