Integrated GaN Half-Bridge Delivers MHz Performance

Article By : Maurizio Di Paolo Emilio

Navitas Semiconductor recently announced its GaNSense half-bridge power ICs that deliver 2-MHz switching frequency, with over 60% reduction in components and circuit size.

Traditionally, power designers had to build half-bridge circuits using discrete transistors and several external components, such as drivers, level-shifters, sensors, bootstraps, and peripherals. Navitas Semiconductor recently announced the industry’s first GaNSense half-bridge power ICs, available in a compact 6×8-mm surface-mount PQFN package.  

These next-gen gallium nitride (GaN) half-bridge ICs deliver 2-MHz switching frequency, with over 60% reduction in components and circuit size, according to the company. That, in turn, reduces the system cost and complexity compared with existing discrete solutions that require a higher number of components, are more expensive, and deliver lower switching frequency, density, and efficiency. 

As shown in Figure 1, the new devices integrate two GaN FETs with drivers, control, sensing, autonomous protection, and level-shift isolation, forming a complete power-stage building block for power electronics. 

Figure 1: GaNSense half-bridge integrates drive, control, sensing, and protection with level shifting isolation into a single 6×8-mm PQFN package (Source: Navitas)

GaN devices

“Our new GaNSense half-bridge power ICs are a huge step that will revolutionize power electronics, since we integrate everything in a single package, enabling megahertz switching frequencies in high-speed topologies”, said Llew Vaughan-Edmunds, a director at Navitas Semiconductor. 

For more reliability and robustness, the integrated GaNSense technology allows autonomous protection with loss-less current sensing for greater levels of efficiency and energy savings. High integration levels make it possible for a variety of AC-DC power topologies, such as LLC resonant, asymmetric half-bridge (AHB), and active-clamp flyback (ACF), to operate at megahertz frequencies by eliminating circuit parasitics and delays. The totem-pole PFC and motor-drive applications are likewise ideal fits for the GaNSense half-bridge ICs. 

The levels of electrical power required by the market are constantly increasing.  Typical power ratings for fast chargers have increased from 20-30W to 65W, and a new ultra-fast category introduced with >100-W power—even up to 200W delivering 0-100% charging of a 4,700mAhr battery in less than 10 minutes, Navitas said. Similarly, a data center’s target efficiency is going from 80% to 90% or more, while customers demand faster charging of EVs, too. 

The key features that the market demands for current and future power applications are size, weight, efficiency, and speed. By using soft-switching topologies, such as zero voltage switching (ZVS), the GaNSense half-bridge ICs minimize switching losses and increase efficiency, while also enabling faster switching and a smaller footprint. 

“We are enabling the highest frequency, efficiency and the most compact design in soft-switching topologies and half-bridge platforms,” Vaughan-Edmunds said. “Legacy silicon solutions have lower frequency, lower efficiency, and lower power density. With GaN, we are now talking about megahertz and plus switching frequency.” 

Navitas said its solution differs from competitors’ solutions in that it has an integrated gate drive (which eliminates parasitic inductance, turn-off, and false turn-on of eMode gate), protection of the sensitive eMode gate node (which protects device from system noise and voltage spikes), and the high-feature GaNSense technology.  

This includes advanced features to simplify design, such as standard and digital-logic inputs, high-side bootstrapping and level-shifting, and loss-less current sensing for the highest efficiency and greatest chance of first time-right, fastest time-to-market designs—in contrast to complex, expensive, and potentially unstable discrete implementations. Shoot-through protection, over-current, over-temperature sensing and autonomous control, 2 kV ESD, and 200 V/ns slew-rate capabilities are all standard with this genuine IC.  

A comparison between a discrete GaN half-bridge solution and an equivalent board designed using GaNSense half-bridge IC is shown in Figure 2, as described by Vaughan-Edmunds 

“We can see how the GaNSense solution requires 61% fewer components, has a significantly lower footprint and provides higher integration. Moreover, it does not require external high-voltage bootstrap, high-voltage bypass diodes, and it does not have exposed gates. As shown in Figure 1, the two pads underneath of the 6×8 mm PQFN package have a larger size for improving thermal management,” Vaughan-Edmunds said.  

Figure 2: GaNSense half-bridge IC solution has a smaller footprint, requires less components, and is exempt from ringing and glitching during switching transitions (Source: Navitas)

Among the different protection measures provided by GaNSense technology, short-circuit protection is a key factor for motor drive applications. Instead of having five microseconds or 10 microseconds of delay since the short circuit detection, the device switches itself off within 30 nanoseconds—six times faster than discretes.  

This is called autonomous protection, since the GaNSense half-bridge power IC doesn’t need to interrupt the microcontroller to tell it to switch it off; it switches off by itself. Footprint reduction is a relevant feature for mid-power motor drive applications, as well.  

The family of GaNSense half-bridge ICs begins with two parts: the NV6247, rated at 650 V, 160 m (dual), and the NV6245C, rated at 275 m (dual). Both are available in an industry-standard, low profile, low inductance, 6×8-mm PQFN package. Both ICs meet the demand coming from different power applications, including mobile fast and ultra-fast chargers, home appliances, and motor drive. 

Immediately available in production with a 16-week lead time, the NV6247 is suitable for mobile and consumer applications with power levels ranging from 100 W to 140 W (like PFC and chargers), and for pumps and fans with power up to 400 W. The NV6245C is currently sampling to select customers and will be broadly available in production to all customers by the end of this year. The GaNSense half-bridge IC family will then expand, offering a wide range of package styles and power levels in the coming quarters. 

Motor control 

GaNSense half-bridge ICs also enable inverter-motor integration. Three half-bridges are normally used to provide a three-phase topology in modern variable-speed drives for electric motors, as used in household appliances, HVAC, industrial machinery, EVs, and robotics. Most of today’s motor-drives are low-frequency and hard-switched. GaN’s low switching capacitance and the absence of a reverse-recovery charge allow switching frequencies to be increased while minimizing losses even in hard-switching applications. 

According to Navitas, a power loss comparison among IGBT, SJ MOSFET, and GaNFast IC in motor-drives shows how GaN achieves a 78% reduction in total power loss, while simultaneously running 3× faster than a legacy Si IGBT design. By using GaN Power ICs into a 2-kW motor drive design, the inverter efficiency increases 2.5% (from 96% to 98.5%), while total losses reduce 50% (from 15 W to 6.8 W). 

Figure 3: GaNSense half-bridge ICs enable inverter-motor integration (Source: Navitas)

“We’re also eliminating the heatsinks, and we’re going to put this into the motor shaft,” Vaughan-Edmunds said. “For the customers who want the motor-integrated inverter, this is a perfect solution. We feel we have the highest integration level.”

 

This article was originally published on EE Times.

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