The Ultimate Guide to Power Semiconductor Devices: Everything You Need to Know

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Introduction

Power semiconductors are essential in contemporary electronics,allowing for effective management and transformation of electric power.These devices are crucial in numerous uses like power supplies,motor drives,renewable energy systems and electric vehicles.In this blog post,we will explore power semiconductor devices,looking at their different types,operational principles,benefits and uses.

Know about Power Semiconductor Devices and it's type

  • The progress in power electronics today has been possible primarily due to advances in power semiconductor devices. Of course, apart from device evolution, the inventions in converter topologies, pulse-width modulation (PWM) techniques, control and estimation techniques, digital signal processors, application specific integrated circuits (ASICs), control hardware and software, etc. also have contributed to this advancement.
  • Modern era of solid-state power electronic began with the advent of thyristor (silicon controlled rectifiers) in the late 1957.Gradually, various types of power semiconductor devices were developed and became commercially available since 1970.
Power semiconductor devices can be classified into three categories according to their degree of controllability. The categories are:
  1. Uncontrolled turn-on and off devices (e.g. diode)
  2. Controlled turn-on and uncontrolled turn-off (e.g. SCR)
  3. Controlled turn-on and off characteristics [e.g. Bipolar junction transistors (BJTs), MOSFETs, Gate-turn-off thyristors (GTOs), Static induction thyristor (SITH), Insulated-gate bipolar transistors (IGBTs),static induction transistors (SITs), mos-controlled thyristors (MCTs)]
  • The on and off states of diodes are controlled by power circuit. Thyristors are turned-on by a control signal and are turned-off by the power circuit whereas the controllable switches are turned-on and off by controlled signals.The devices which behave as controllable switches are BJT, MOSFET, GTO, SITH,IGBT, SIT and MCT.
  • BJT, MOSFET, IGBT and MCT can withstand unipolar voltage whereas thyristors and GTOs can withstand bipolar voltages. BJT, MOSFET, IGBT and SIT requires continuous signal for keeping them in turn-on state but SCR, GTO, SITH and MCT requires pulse-gate signal for turning them ON and once these devices are ON,gate-pulse is removed.
  • Triac and RCT (reverse conducting thyristor) possess bidirectional current capability whereas all other remaining devices (diode, SCR, GTO, BJT, MOSFET,IGBT, SIT, SITH, MCT) are unidirectional current devices.
  • As the evolution of new and advanced devices continued, the voltage and current ratings and electrical characteristics of the existing devices began improving dramatically. In fact, the device evolution along with converter,control and system evolution was so spectacular in the last decade of 20th century, that we define it as the "decade of power electronics".
  • Thyristors are used for high power low frequency applications. Devices are available with 8000 V and 4000 A ratings. ABB recently introduced a monolithic ac switch that has the voltage ratings of 2.8 kV-6.5 kV and current ratings of 3000-6000 A. The advent of large GTOs push the thyristor voltage-fed inverter from the market. Currently, GTOs are available with 6000 V, 6000 A (Mitsubishi) ratings for large voltage-fed inverter applications.
  • Power MOSFET has grown in rating, but it's primary popularity is in high frequency switching mode power supply and portable appliances. The BJT appeared and then fell into obsolescence due to the advent of IGBT at the higher end and power MOSFET at the lower end. The invention of IGBT is an important milestone in the history of power semiconductor devices.
  • Commercial IGBTs are available with 3500 V, 1200 A, but upto 6.5 kV and 10 kV devices are under test in laboratory. Trench gate IGBT with reduced conduction drop is available upto 1200 V, 600A. IGBT intelligent power modules (IPM) from a number of vendors are available for 600 V, 50-300 A and 1200 V, 50-150 A to cover upto 150 hp ac drive applications.
  • Integrated Gate-Commutated Thyristor (IGCT) is basically a hard-driven GTO with built-in gate driver, and the device is available with 6000 V, 6000 A (10kV devices are under test). Recently, ABB introduced reverse blocking IGCT (6000 V, 800 A) for use in current-fed inverter drives. Large band gap power semiconductor device with silicon carbide (SiC) that has high carrier mobility, high electrical and thermal conductivities and strong radiation hardness is showing high promise for next generation power devices.
  • These devices can be fabricated for higher voltage, higher temperature, higher frequency and lower conduction drop. SiC diodes are commercially available and other devices are expected in future.

The Various Kinds of Power Semiconductor Devices

  1. Diodes: Diodes are the simplest semiconductor devices that would enable current to flow in one direction only. The rectifiers made of diodes are a widely used components of power electronics for conversion of AC to DC. They also employment in freewheeling and clamping circuits to catching voltage spikes and conserving other components.
  2. Transistors: Transistors are three-terminal semiconductor devices featuring emitter, base, and collector terminals. The two most widely used types of transistors in power electronics are Bipolar Junction Transistors (BJT) and Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFET).
  3. BJT: BJT are very reliable and can handle the high current flow. They are more often used for amplification and switching circuits.
  4. MOSFET:The MOSFET have greater switching speeds and lower power losses as compared to the BJTs, they are therefore compatible with high frequency switching applications such as the inverter drives in the power system and switching power supplies.
  5. Insulated Gate Bipolar Transistors (IGBT): IGBT comprise the speed switching ability of MOSFET and BJT current carrying capacity. They have been widely applied to the particular fields of medium to high-power, such as motor drives, renewable systems and industrial automation.
  6. Thyristors:Thyristors are four-layer semiconductor devices that are able to tackle large currents when they are under voltage. They are widely applied in high-power switching circuits which involve motor control, voltage regulation, AC power control and so on.

Working Principles of various Power Semiconductor Devices

The exploitation of power semiconductor devices is practiced to the inner structure and through matching the control signs well.

Diodes

Forward bias in a diode results in the flow of electricity in the forward direction due to which electrons can flow from the cathode to the anode. They are used to stop current in the reverse bias mode and also block electron flow.

BJT

At the base in a BJT , by applying a small current at the base terminal, one can control the larger current flow between the emitter and the collector terminals. That results in the fact that such devices are applied for signal amplification and switching.

MOSFET

The flow of current through the channel of MOSFET is regulated according to the voltage applied to the gate terminal, which determines the conductivity between the source and the drain. They have a fast switching performance and acceptable efficiency levels, which are ideal for high-frequency applications.

IGBT

IGBT then combines both the insulated gate control of MOSFETs with the high current capability of BJTs. Those are done by regulating the electrons flow from the collector to the emitter terminal via the gate signal.

Thyristors

The thyristors have three operational states. The states are off state, forward conducting state, and reverse blocking state. They need a trigger signal to activate the transition from the off state into the conducting state; after such triggering, the current can be very high until they are turned off.

Power semiconductor devices have different applications

Power Supplies

Switch-mode power supplies have been developed through the use of power semiconductors like MOSFETs and diodes which efficiently convert the AC power to DC power for electronic devices that now includes computer equipment.

Motor Drives

In like manner to the inverter drives and motor control systems, that use power semiconductor devices of type IGBTs and MOSFETs for regulating the speed and commutation of electric motors, in industrial and vehicle applications.

Renewable Energy

Power electronics occupy a key position on renewable energy systems like a solar inverters and wind turbine converters where they convert DC power from the solar panels and wind turbines into usable AC power for future grid connection.

Electric Vehicles (EVs)

The power semiconductor devices employed in electric vehicles are used to convert electricity and control motor power efficiently, one of the dominant factors toward ubiquitous sustainable transport mode.

Industrial Automation

Semiconductor based power electronics facilitates pin-point control and automation in industrial processes that improves efficiency and brings down the energy consumption.

Conclusion

In conclusion, power semiconductor devices are indispensable components that drive efficiency, reliability, and innovation across diverse sectors ranging from consumer electronics to renewable energy. As research and development efforts continue to push the boundaries of performance and functionality, we can expect even more groundbreaking applications and advancements in the realm of power electronics, shaping a greener and more electrified future.
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