Overview of Power Semiconductor Device Categories
Power semiconductors are the core of power electronic systems, responsible for key tasks such as energy conversion (rectification, inversion, frequency conversion, transformation, etc.) and circuit control. They mainly work in the on/off state to efficiently handle and control larger power (current, voltage). According to its structure, working principle, and control characteristics, it can be mainly divided into the following categories:
Power diodes
Core feature: The simplest power semiconductor device with unidirectional conductivity (forward conduction, reverse blocking). Uncontrollable devices, whose conduction and turn off are entirely determined by the polarity of the external circuit voltage.
Main types:
General Purpose Rectifier Diodes: used for low-frequency rectification.
Fast Recovery Diodes (FRDs): With extremely short reverse recovery time, they are used in high-frequency switching circuits (such as switching power supplies) to reduce switching losses and electromagnetic interference.
Schottky Barrier Diodes (SBDs): Utilizing metal semiconductor junctions, they have lower forward voltage drop and extremely fast switching speed (with almost no reverse recovery problem), but relatively lower reverse voltage resistance and larger reverse leakage current. Widely used in low voltage and high frequency applications.
Thyristors and Derivatives
Core feature: Semi controlled device. Once the conduction is triggered by the gate signal, even if the gate signal is removed, as long as the anode current is greater than the holding current, the device will maintain conduction until the anode current drops below the holding current before it can be turned off. Therefore, it can only control conduction and cannot directly control shutdown (relying on external circuit conditions).
Main types:
Ordinary thyristor (Silicon Controlled Rectifier SCR): The most basic type, mainly used for AC voltage regulation, rectification, and active inverters at power frequency or medium low frequency.
Gate Turn Off Thyristor GTO: Developed on the basis of SCR, it increases the gate turn off capability. Applying negative pulse current to the gate can forcibly turn off the GTO in conduction. The control capability is stronger than SCR, but the driving circuit is complex and the switching speed is relatively slow (especially when turned off).
Integrated GateCommutated Thyristor (IGCT): an improved version of GTO. The gate drive circuit is highly integrated into the device module, optimizing the gate commutation path, greatly improving switching speed and reliability, and reducing driving power and losses. Commonly used in high-power converters.
Power Transistors
Core feature: Fully controlled device. It can be controlled to conduct or turn off through continuous control signals (current or voltage). Flexible control and generally faster switching speed than thyristor devices.
Main types:
Bipolar Junction Transistor (BJT): A current controlled device. Continuous base current is required to maintain conduction. The conduction voltage drop is relatively low, but the switching speed is slow, the driving power is high, and there is a problem of secondary breakdown. In modern high-frequency applications, MOSFETs and IGBTs have basically replaced them.
Power Metal Oxide Semiconductor Field Effect Transistor (MOSFET): a voltage controlled device. Control conduction and shutdown through gate source voltage. Main advantages: extremely fast switching speed (up to MHz level), simple driving (low driving power), no secondary breakdown problem, positive temperature coefficient of conducting resistance, easy parallel connection. Main limitation: The on resistance increases significantly with the increase of withstand voltage (Rdson A constant), resulting in significant conduction losses in high-voltage devices. Therefore, it is most suitable for medium and low voltage (usually<1000V), high-frequency applications (such as switching power supplies, DCDC converters, motor drives).
Insulated Gate Bipolar Transistor (IGBT): A composite fully controlled device. Combining the voltage control (gate) of MOSFET with the low conduction voltage drop advantage of BJT. Structural essence: It can be regarded as a Darlington PNP type BJT driven by MOSFET (more precisely, a composite structure of MOSFET input and BJT output). Advantages: In the medium to high voltage range (600V 6500V+), it has a much lower conduction voltage drop (lower conduction loss) than MOSFETs, while maintaining the advantage of voltage control. The switching speed is higher than GTO/BJT but lower than MOSFET. Application: It is currently the absolute main component for medium to high power and medium to high voltage applications, such as industrial frequency converters, electric vehicle main drive inverters, new energy generation inverters, UPS, welding machines, etc.
Wide Bandgap WBG Power Devices
Core feature: A new generation of power devices manufactured using wide bandgap semiconductor materials such as silicon carbide (SiC) or gallium nitride (GaN). Compared to traditional silicon (Si) devices, it has excellent physical properties such as higher bandgap, higher critical breakdown electric field, higher thermal conductivity, and higher electron saturation drift velocity.
Revolutionary advantages:
Higher withstand voltage capability: Under the same withstand voltage, the device thickness can be thinner and the on resistance can be lower.
Higher operating temperature: The theoretical limit temperature far exceeds that of Si devices.
Higher switching speed: Extremely low switching losses (Eon/Eoff), capable of operating at MHz level frequencies.
Lower conduction loss: particularly advantageous at high voltage levels.
Main types (similar in structure to Si, but with a leap in performance):
SiC Schottky diodes (SiC SBDs): First commercialized with almost no reverse recovery, they are an ideal alternative to FRDs in high-frequency PFC and inverter bridge arms.
SiC MOSFET: At high voltages (650V, 1200V, 1700V+), its on resistance and switching losses are much lower than those of Si IGBT and Si MOSFET, and it is rapidly replacing IGBT in high-end applications such as electric vehicle main drive and photovoltaic/energy storage inverters.
SiC junction field-effect transistors (SiC JFETs)/SiC normally on devices: Another structure typically used in a normally off module cascaded with Si MOSFETs.
GaN high electron mobility transistors (GaN HEMTs): The main advantages are concentrated in ultra-high frequency (MHz level) and ultra-high power density applications at voltage levels of 650V and below (such as fast charging adapters, data center server power supplies, LiDAR, wireless charging). Usually it is a normally open device that needs to be used in conjunction with a driver to form a normally closed module. The switch speed is extremely fast and there is no reverse recovery.
Summary logic:
From the perspective of control capability: uncontrollable (diode)>semi controlled (thyristor)>fully controlled (transistor, WBG device).
From the perspective of structural principles: diode>four layer three terminal device (thyristor type)>three layer three terminal bipolar junction (BJT)>three layer three terminal unipolar junction (MOSFET)>four layer three terminal composite junction (IGBT)>new structures based on new materials (SiC MOSFET, GaN HEMT).
From the perspective of application trends, Si based devices (diodes, thyristors, BJTs, MOSFETs, IGBTs) are still widely used, while WBG devices (SiC, GaN) are rapidly penetrating high-end, high-frequency, and high-power density fields due to their excellent performance, which is the future development direction.
This classification clearly demonstrates the technological evolution and application differences of power semiconductors from basic to advanced, from low frequency to high frequency, from low power to high power, and from silicon-based to wide bandgap.