Semiconductor Power Devices: A Comparison of Thyristors and IGBTs

Thyristor, also known as a silicon-controlled rectifier (SCR), is a semiconductor device used for high-power applications. It features three pn junctions and a 4-layer structure. Typically, two thyristors are connected in reverse parallel. The thyristor serves not only as a rectifier but also as a non-contact switch for fast circuit connection or disconnection. It enables the conversion of direct current (DC) to alternating current (AC) through inversion and the transformation of one frequency of AC to another. Thyristors have advantages such as small size, high efficiency, good stability, and reliable operation. They are widely used in applications such as controllable rectification, inversion, frequency conversion, voltage regulation, and non-contact switching.

Many household appliances rely heavily on thyristor devices, including dimmable lights, variable-speed fans, air conditioners, televisions, refrigerators, washing machines, cameras, combination audio systems, audiovisual circuits, timers, toys, wireless remote controls, cameras, and industrial control systems.

Another commonly used power device is the insulated gate bipolar transistor (IGBT), which consists of a bipolar junction transistor (BJT) and a metal-oxide-semiconductor field-effect transistor (MOSFET). IGBT combines the high-speed switching characteristics of MOSFETs with the low on-state voltage drop of GTRs. It requires less drive power, has fast switching speed, and is suitable for currents with DC voltages of 600 volts and above. IGBTs find extensive applications in fields such as AC motors, frequency converters, power supplies, lighting circuits, and traction drives.

Compared to thyristors, IGBTs offer their own advantages. Thyristors are controllable switch elements, but most of them can only control the on-state and cannot control the off-state. However, there are now thyristors with controllable turn-off capability available. On the other hand, IGBTs can operate at higher frequencies, reaching up to approximately 25 kHz, while thyristors primarily operate below 5 kHz. This is one of the advantages of IGBTs over thyristors.

However, IGBTs have higher costs and more complex manufacturing processes compared to thyristors, especially for manufacturing high-voltage and high-current components. Furthermore, IGBTs are far less capable in terms of overload protection compared to thyristors. With advancements in manufacturing processes and improved short-circuit protection measures, the cost of IGBTs has significantly reduced. In many cases, their prices are now competitive with thyristors. Additionally, due to their flexible and convenient control characteristics, IGBTs can eliminate the need for certain components in thyristor circuits, such as turn-off circuits. As a result, IGBTs can fully replace thyristors in many applications and offer better performance.

Consequently, many devices that used to rely on thyristors have gradually transitioned to using IGBTs. Whether in the field of power electronics or industrial applications, the utilization of IGBTs has become increasingly widespread, thanks to their flexibility, high performance, and relatively lower cost.