Insulated-gate bipolar transistors (IGBTs) are increasingly being incorporated in power system designs to decrease losses and improve switching behavior. Let’s look at some potential solutions for different applications. The three-terminal power semiconductor device, originally developed in the 1980s, has overcome early problems with issues such as latch-up and secondary breakdown. They give design engineers a viable power switching option in applications such as appliances, vehicles, and lamp ballasts, among others.
IGBT technology combines the high-speed switching performance of a power MOSFET with the high-voltage/high-current handling capabilities of a bipolar transistor. In general, an IGBT equivalent circuit (Figure 1) is a combination of a MOSFET transistor and a bipolar transistor.
The main advantages of using IGBTs over other types of transistors are relatively fast switching speeds, a low driving power and a simple drive circuit due to the input MOS gate structure. It also offers a very low on-state voltage drop, due to conductivity modulation, and has superior on-state current density. For example, in the case of a variable frequency driver (VFD), an IGBT will switch the current on and off so rapidly that less voltage will be channeled to the motor, helping to create a pulse-width modulation (PWM) wave to control the speed of the motor.
IGBT technology is available in a variety of voltage classes, current ratings, and topologies (e.g. half bridge, full bridge). They can be used in wide range of applications, and are an especially a good choice for moderate speed and high voltage applications. The growing need to minimize power system size and weight is increasing the design of IGBT modules that use the latest advances of IGBT technology (topologies, materials, etc.), and, moreover, the use of the latest advances in power semiconductor packaging. Here are some different IGBT solutions for three different applications:
Industrial Motor Drives
A good option to regulate the efficiency, speed, position, and torque of motors (e.g. pumps, fans, etc.) is the use of semiconductor devices such as IGBTs that can help to switch the current flow to motors with minimal switching-time or conduction-period losses.
One of the challenges for motor drives is the limitation of switching speed due to the inherent limitation of the motor insulation system. Most motor manufacturers typically recommend not exceeding a dv/dt limit of approximately 5 kV/μs under worst-case conditions for 400 V motors to avoid voltage spikes and rise times that can lead to arcing and eventually to coil-insulation failure.
Infineon’s 1,200 V TRENCHSTOP™ IGBT7 is specially optimized for industrial drives applications. It is based on micro-pattern trenches (MPT), and is characterized by implementing parallel trench cells separated by sub-micron mesas. IGBT7 offers the ability to vary the dv/dt by adjusting the value of the gate resistor (RG) (Figure 2). Infineon’s technology also allows operation at a temperature of 175°C under overload conditions that could result in higher power density, but such high temperatures might result in higher heatsink temperatures.
Renewable Energy
Solar and wind applications use high power semiconductor devices to optimize generation and network connection. IGBTs are an excellent option when working with the high-power levels found in high-scale renewable projects.
In solar inverter applications, inverters convert DC voltage from a solar array panel to AC voltage. The latter can be used to power AC loads (e.g. lighting, home appliances, power tools, etc.) using a single-phase AC sinusoidal voltage waveform at a frequency and voltage that depend on the design for which the inverter is intended. There are many IGBTs options that can help achieve those requirements, and here is one of them:
ON Semiconductor offers a power module solution (NXH160T120L2Q2F2S1G) for solar and industrial applications avoiding the use of discrete IGBTs. The module (Figure 3) contains a split T-type neutral point clamped three-level inverter, consisting of two 160 A/1,200 V half-bridge IGBTs with inverse diodes, two neutral point 100 A/1,200 V rectifiers, two 100 A/650 V neutral point IGBTs with inverse diodes, two half-bridge 100 A/650 V rectifiers and a negative temperature coefficient thermistor (NTC).
Devices are available in Q1 and Q2 packages targeted for 30 KW & 50 KW inverters, integrate field stop trench IGBTZ and fast recovery diodes that provide lower conduction and switching losses, and enable designers to trade off between low VCE(SAT) and low EON/EOFF losses to fully optimize circuit performance.
Automotive
Electric vehicles (EV) and hybrid electric vehicles (HEV) comprise a running motor driven by converting direct current (DC) power stored in a high-voltage battery using a power conversion system. IGBT modules are mainly used for such power conversion system and they are required to be compact, since many power components (e.g. high-voltage battery, power conversion system, motor, etc.) must be installed within a limited space.
Dynex has developed numerous technologies specifically for EV applications that meet automotive qualifications and embrace the demands of ISO26262 for functional safety. One of the IGBT technologies used by Dynex is called “double-sided cooling” where traditional wire-bond process is eliminated and replaced by another substrate that is soldered to the top of the silicon chip.
IGBT modules with double-sided cooling plates are part of integrated power units (IPUs) that are used in integrated power modules (IPMs) (Figure 4). Dynex claims that a double-sided cooling structure with thin and lightweight cold plates increases power density by more than 30 percent compared with a conventional single-sided cooled module approach.
According to Mordor Intelligence, The IGBT market was valued at $4.5 billion in 2017, and is expected to reach $7.8 billion by 2023, at a CAGR of 9.62 percent, during the forecast period (2018-2023). Power semiconductor devices (e.g. IGBTs) play a major role not only in the development of renewable energy ventures but in the development of technology for EVs and HEVs.
Major players designing IGBT products—Infineon Technologies, Fuji Electric Co. Ltd, ROHM Co. Ltd., Semikron International GmbH, Dynex Semiconductor, ABB Ltd.,—are seeing the potential opportunity in different markets, therefore expect more IGBT innovations in the future.