Topic: GaN Power Devices Offer Advantages In Industrial Motor Control
GaN Power Devices Offer Advantages In Industrial Motor Control
The superior electrical characteristics of GaN power devices are outpacing traditional MOSFETs and IGBTs in complex industrial motor control applications.
Motor control, particularly frequency-controlled drives, is a technology that has advanced rapidly in recent years as a result of the widespread use of motors in a variety of applications and the potential for huge energy savings. Frame-based power modules for motor control have brought about a significant revolution in application domains that are particularly sensitive to cost, size, and performance.
Electric motor designs that extract higher performance from compact platforms are required for emerging electronic applications. Motor driver circuits based on classical silicon MOSFETs and IGBTs have difficulty meeting the new criteria. It is becoming increasingly difficult for designers to keep power losses in check as silicon technology approaches theoretical limits for power density, breakdown voltage, and switching frequency. The main consequences of these limitations are reduced efficiency and additional performance issues at high operating temperatures and switching speeds.
Consider a silicon-based power device that operates at a switching frequency of ≥40 kHz. Under these conditions, the switching losses are greater than the conduction losses, with cascading effects on the total power losses. Dissipating the excess heat that is generated requires a heat sink, which increases the weight, footprint, and cost of the solution. Gallium Nitride (GaN)-based High Electron Mobility Transistor (HEMT) devices offer superior electrical characteristics and are a valid alternative to MOSFETs and IGBTs in high-voltage, high-frequency switching motor control applications. . Our discussion here focuses on the advantages GaN HEMTs provide in the power and inverter stages of high power density electric motor applications.
Size and energy efficiency are important in motors for robotics and other industrial uses, but other factors also come into play. A GaN solution enables higher pulse width modulation (PWM) frequencies, while low switching losses make it easier to drive very low inductance permanent magnet motors and brushless DC motors. These features also minimize torque ripple for precise positioning in servo drives and stepper motors, allowing high-speed motors to reach high voltages in applications such as drones.
Benefits of GaN
GaN is a wide bandgap material. As a result, its bandgap (the energy required for an electron to move from the valence band to the conduction band) is substantially wider than that of silicon: about 3.4 eV versus 1.12 eV. Because charges that normally build up at the joints can be dissipated more quickly, the improved electron mobility of a GaN HEMT correlates with a faster switching speed.
GaN’s low switching losses and ability to operate at switching frequencies up to 10 times higher than silicon are due to its shorter rise times, lower drain-to-source (RDS) turn-on resistance values ) and reduced output and gate capacitance. The ability to operate at high switching frequencies allows for a smaller footprint, weight, and volume and eliminates the need for bulky components like inductors and transformers. The switching losses of a GaN HEMT transistor remain much lower than those of a silicon MOSFET or IGBT as the switching frequency increases, and the higher the switching frequency, the more noticeable the difference becomes.
In short, GaN devices outperform traditional silicon-based power devices in several ways, including the following:
- GaN’s breakdown field is more than 10 times that of silicon (3.3 MV/cm vs. 0.3 MV/cm), allowing GaN-based power devices to support 10V voltage. times higher before being damaged.
- Operating with the same voltage values, GaN devices exhibit lower temperatures and generate less heat. As a result, they can operate at higher temperatures (up to 225˚C and higher) than silicon, which is limited by its lower junction temperature (150˚C to 175˚C).
- Due to its intrinsic structure, GaN can switch at higher frequencies than silicon and provides low RDS (turn-on) and excellent reverse recovery. That, in turn, results in high switching efficiency and low power losses.
- Being a HEMT, GaN devices have a higher electric field strength than silicon devices, allowing for a smaller die size and reduced footprint.
Motor Control Solutions
A common solution for driving an AC motor includes an AC/DC converter, a DC circuit, and a DC/AC converter (inverter). The first stage, usually based on a diode or transistor, converts the main 50Hz/60Hz voltage to an approximate DC voltage, which is then filtered and stored in the DC circuit for later use by the inverter. Finally, the inverter converts a DC voltage into three sinusoidal PWM signals, each of which drives a single phase of the motor. GaN HEMT transistors are typically used for the implementation of the inverter stage of the motor driver, the most critical point of a high-voltage, high-frequency motor driver solution.
EPC’s EPC2152, for example, is an eGaN FET half-bridge power stage IC and driver in a single package, based on the company’s proprietary GaN IC technology. A monolithic chip contains the input logic interface, level shifting, bootstrap charging, and gate drive buffer circuits, as well as the eGaN output FETs configured as a half-bridge. High integration enables the compact package size of 3.85 × 2.59 × 0.63 mm in a chip-scale LGA form factor. In a half-bridge topology, the two output FETs of eGaN are intended to have the same RDS (on). The use of on-chip gate driver buffering with eGaN FETs virtually eliminates the impacts of common source inductance and gate driver loop inductance (see Figure 1). Internal regulation of the gate drive voltage based on feedback from the driven output FETs ensures a safe gate voltage level while turning the output FETs to an RDS (on) low state.
Another example is the GaN-on-silicon enhanced mode power transistor GS-065-004-1-L from GaN Systems. GaN’s properties allow for high current, high voltage breakdown, and high switching frequency. GaN Systems implemented its patented Island Technology cell design for high current die performance and performance. The GS-065-004-1-L is a bottom-cooled transistor in a 5 × 6 mm PDFN package that offers low junction-to-case thermal resistance. These features combine to provide very high-efficiency power switching.
Navitas Semiconductor’s NV6113 integrates an enhanced 300 mΩ 650 V GaN HEMT, gate driver, and associated logic, all in a 5 × 6 mm QFN package. The NV6113 can support a slew rate of 200 V/ns and operates at up to 2 MHz. Optimized for high-frequency and soft-switching topologies, the device creates a “high-performance powertrain building block with digital input and output Easy to use”. The power IC extends the capabilities of traditional topologies (such as flyback, half-bridge, and resonant types) to switching frequencies above the megahertz band. The NV6113 can be deployed as a single device in a typical boost topology or parallel for use in the popular half-bridge topology.
Texas Instruments Inc. offers a broad portfolio of integrated GaN power devices. The LMG5200, for example, integrates an 80V GaN half-bridge power stage based on GaN FETs in enhanced mode. The device consists of two GaN FETs driven by a high-frequency GaN FET driver in a half-bridge configuration. To simplify the design of the device, TI provides the TIDA-00909, a reference design for high-frequency motor drives using a three-phase inverter with three LMG5200s. The TIDA-00909 is provided with a compatible interface to connect to a C2000 MCU LaunchPad development kit for easy performance evaluation. GaN Power Devices Offer Advantages In Industrial Motor Control.
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GaN vs. SiC
Due to properties such as energy savings, size reduction, integration options, and reliability, the use of silicon carbide (SiC) devices in motor control and electrical power control applications is a breakthrough. Among other things, it is now feasible to employ the optimal switching frequency for the connected motor in the inverter circuit, which has significant implications for motor design.
A loss reduction of up to 80% can be a game-changer in solutions where active cooling to regulate semiconductor losses is critical to performance and reliability. One example is the SiC-based CoolSiC MOSFET with XT lead technology in an optimized 1200V SMD D2PAK-7 package from Infineon Technologies, which offers attractive thermal capabilities in a small form factor. This combination enables passive cooling in high-density motor drive segments such as servo drives, enabling the robotics and automation industries to create fanless and maintenance-free motor inverters. Fanless solutions in automation open up new design possibilities because they save money and time on maintenance and materials. The small size of the resulting system makes it suitable for integrating drives into a robotic arm.
Compared to a similarly rated IGBT, a higher current can be achieved with the same form factor, depending on the power type chosen for the CoolSiC, while maintaining a constant junction temperature that is significantly lower in the case of a SiC MOSFET. (about 40–60 K) compared to an IGBT (105 K). A SiC MOSFET allows higher currents to be driven without a fan for a given device size.
Electric motors can be found in almost every aspect of modern civilization, from the electrical equipment we use in our homes and kitchens to the cars we drive (including gasoline, hybrid, and fully electric vehicles) and the factories that produce our smartphones. . Although some motors are quite simple and others extremely complicated, they all have one thing in common: they all need to be controlled.
Other motor applications, such as those found in today’s industrial plants, require complex motor control to deliver high-speed, high-precision motor control activities. Traditional silicon MOSFETs and PWM low-frequency inverters are being phased out of DC and battery-powered motor applications in favor of GaN-based PWM high-frequency inverters. Benefits include increased system efficiency and the elimination of large passive components, namely electrolytic capacitors, and an input inductor.