Bringing GaN-based Power Devices to Market

Article By : Maurizio Di Paolo Emilio

ST presented MasterGaN, a platform that integrates a half-bridge driver based on silicon technology with a pair of gallium nitride power transistors. STMicroelectronics, in an interview with EE Times, highlighted how this new platform enables systems to be up to 80% smaller by offering lighter weight and 3 times faster recharge times. But above all

ST presented MasterGaN, a platform that integrates a half-bridge driver based on silicon technology with a pair of gallium nitride power transistors. STMicroelectronics, in an interview with EE Times, highlighted how this new platform enables systems to be up to 80% smaller by offering lighter weight and 3 times faster recharge times. But above all, it simplifies design, thereby optimizing time-to-market. MasterGaN combines silicon with GaN to accelerate the creation of next-generation, compact and efficient battery chargers and power adapters for consumer and industrial applications up to 400W. Through the use of GaN technology, the new devices can handle more power while optimizing their efficiency. ST Microelectronics has highlighted how integrating GaN with drivers simplifies the design, with a higher level of performance. GaN Market The GaN transistor is one of the “coldest” components that exist today. Its low junction resistance allows low temperature and low energy losses even at high temperatures and extreme conditions. This is one of the main reasons why this material is widely used in many critical sectors, where the need for high current is the main prerogative. The current GaN market is typically served by discrete power transistors and drive ICs that require designers to learn new implementation techniques to achieve the best performance. ST’s MasterGaN approach aims to offer faster time-to-market while maintaining efficient performance in a smaller footprint, simplified assembly, and increased reliability with fewer components. ST Microelectronics said that with GaN technology and the benefits of ST’s integrated products, chargers and adapters can reduce 80% of the size and 70% of the weight of standard silicon-based solutions. In power GaN transistors, there are two parameters of the component on which temperature plays an important role: RDS (ON) with the related operating losses and transconductance with the related switching losses. There are many reasons for maintaining a low temperature:
  • To prevent thermal runaway in the worst operating conditions
  • To reduce losses in general
  • To increase system performance and efficiency
  • To increase system power density
  • To increase the reliability of the circuit
ST Solutions ST’s platform, MasterGaN1, contains two half-bridge GaN power transistors with integrated high-side and low-side silicon drivers. The platform uses a 600V half bridge gate driver and normally-off high electron mobility GaN transistors (HEMT). The high electronic mobility allows a GaN transistor to switch in about a quarter of a silicon MOSFET time. In addition, switching losses are between about 10 and 30% of those of a silicon transistor for a given operating mode. As a result, GaN high electron mobility transistors (HEMTs) can be driven at much higher frequencies than silicon MOSFETs, IGBTs. GaN HEMTs require the addition of polarization networks that chip suppliers have integrated into their devices to function properly. The use of gallium nitride in applications such as power converters, , enable significant improvements compared to traditional solutions based on silicon: greater power efficiency, smaller size, lighter weight and lower overall cost. The built-in power GaNs in MasterGaN have RDS(ON) of 150 mΩ and 650 V drain-source breakdown voltage, while the high side of the built-in gate driver can easily be powered by the built-in bootstrap diode.
Figure 1: block diagram of MasterGaN1
Figure 1: block diagram of MasterGaN1. Click to enlarge the image. (Source: ST Microelectronics)
 
Figure 2: development board for MasterGaN1 (Source: ST Microelectronics)
Figure 2: development board for MasterGaN1. Click to enlarge the image. (Source: ST Microelectronics)
The MASTERGAN1 is equipped with protection against malfunctions in low efficiency or dangerous conditions, and the interlock function prevents cross-conduction conditions. The logic inputs are compatible with signals from 3.3V to 15V, thus offering easy interfacing with microcontrollers and various sensors.  UVLO protection on both the lower and upper driving sections, preventing the power switches from operating in low efficiency or dangerous conditions, and the interlocking function avoids cross-conduction conditions. These devices’ family will be offered as pin-compatible half-bridge products that allow engineers to scale projects with minimal hardware changes. Taking advantage of the low power-on losses and no body-diode recovery that characterizes GaN transistors, the products offer improved overall performance in high-end high-efficiency topologies such as flyback or forward with active clamp, resonant, PFC pole bridgeless totems and other soft and hard switching topologies used in AC/DC and DC/DC converters. The EVALMASTERGAN1 board allows you to evaluate the characteristics of MASTERGAN1 and quickly create new topologies without the need for a complete PCB design. The board provides a programmable dead time generator on board with a single VCC power supply (type 6 V). An integrated 3.3 V linear voltage regulator supplies the logic as microcontrollers or FPGAs. The board offers customization opportunities such as using an external bootstrap diode, separate power supply for various solutions, and the use of low side shunt resistors for peak current topologies.

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