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Posted on 10 July 2019

New Generation of GaN Based Power Stage Products

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This generation heralds a era in high density and highly efficient power Conversion

With the introduction of commercial HEXFET® power MOSFETs more than three decades ago, International Rectifier started a revolution in switch-mode power supplies (SMPS). Now, 30 plus years later, as silicon matures, the demand from industry for smaller and more efficient DC-DC converter solutions continues.

By John Lambert, POL Marketing Manager, International Rectifier Corp., El Segundo, California, US

 

To meet new performance goals beyond the reach of silicon, IR has developed GaNpowIR™, the industry’s first family of commercial integrated power stage products utilizing IR’s revolutionary Gallium Nitride-on-silicon (GaN-on-Si) epitaxial power device technology platform. GaN has a critical electric field which is substantially greater than Si. Combined with device structures which yield excellent conductivity, this provides GaN-based devices with a far superior tradeoff between operating voltage and on-resistance. GaN-based devices are also capable of operating efficiently at much higher frequencies than comparable silicon-based devices since they present a significant drop in gate charge (Qg) and device switching RDS(on)*Qg Figure-of-Merit (FOM) is much lower than for silicon1.This allows the reduction in size of power conversion solutions, a key enabling feature in today’s power hungry end application markets. In addition, very efficient lateral devices are possible using GaN-based technology which allows relatively simple scaling with operating voltage, as well as for improved integration with other circuit functions, compared to state-of-the-art vertical Silicon based power devices.

New GaNpowIR Product Family

Presently aimed at point-of-load (POL) and multiphase regulators for servers, routers, switches, and general-purpose converters, the first two members of this commercial GaN-based power stage GaNpowIR product family includes the iP2010 and iP2011. These devices integrate a dedicated PowIRtuneTM driver IC matched to a multi-switch monolithic GaN-on-Si based power device as illustrated in Figure 1.

PowIRtuneTM driver IC matched to a multi-switch monolithic GaN-on-Si based power device

The proprietary PowIRtune™ driver has a superfast sensing scheme to precisely tune deadtime for optimal performance and maintain the optimal deadtime with variations in load current, input voltage and temperature. The incorporated high-side (Q1) and low-side (Q2) GaN power switches are combined in a monolithic power switch in order eliminate the parasitic switching losses that are inherent with the copper interconnects used in traditional power stage solutions that utilize discrete high and low side switches. This along with the intrinsically low on-resistance and low gate charge of the GaN-based technology provide the GaNpowIR devices the ability to switch at frequencies as high as 5MHz.

The iP2010 features an input voltage range of 7V to 13.2V and output voltage range of 0.6V to 5.5V with an output current up to 30A and can operate at up to 3MHz. Operating up to 5MHz, the pin-compatible iP2011 features the same input and output voltage range but is optimized for up 20A output current. The GaNpowIR devices are housed in a small LGA package measuring only 7.7 mm x 6.5 mm x 1.7 mm. By offering multiple current rating devices in a common footprint, the product family provides flexibility for meeting a broad range of customer requirements in terms of current level, performance and cost. To deliver high efficiency and more than double the switching frequency of the state-of-the-art silicon-based power MOSFETs, the GaNpowIR components are mounted in a flip chip package platform that eliminates the need for wirebonds. Combining GaNbased technology advances with novel packaging enables the integrated GaNpowIR devices to be optimized for operation in the 600kHz to 1.2MHz frequency range.

Taking into account the power stage, inductor and PC-board losses, Figure 2 demonstrates how the iP2010 and iP2011 deliver over 90 percent peak efficiencies while operating at 1.2MHz with; 12V input, 1.2V output and using a 90nH inductor.

iP2010 and iP2011 deliver over 90 percent peak efficiencies

GaNpowIR Compared to Traditional Silicon-based Solutions

Although most designers associate GaN technology with the ability to switch at higher frequencies than traditional silicon solutions, the GaNpowIR devices can be operated at lower frequencies to achieve highest possible efficiencies and energy savings. In fact, by operating the iP2010 at 600kHz, it can deliver much higher efficiencies than the competing leading-edge silicon based commercial power stage solutions operating at the same frequency.

As shown in Figure 3, the peak efficiency performance of iP2010 is over 93 percent in the 11 to 14A output current range, which offers more than 2 percent improvement over the nearest competing silicon based power stage device. This gap widens further as the output current is increased to 30A. At this output current, the conversion efficiency for the GaN based DC-DC converter is about 90 percent, which is at least 4.5 percent higher than the best competing power stage solution and 6.8 percent higher than the other competing solution.

Efficiency performance of iP2010 is over 93 percent

Since GaNpowIR devices can operate at higher frequencies than traditional silicon-based solutions, they can provide maximum power density when space is at a premium. By operating a power stage at these higher switching frequencies the value and size of output capacitors and inductors can be reduced, which in-turn reduces the overall board space. Figure 4 shows the potential space saving of an iP2010/11 power stage solution operating at 800kHz when compared to a discrete solution or a DrMOS power stage solution operating 400kHz. In this example the discrete solution using a 4x4mm discrete MOSFET driver, a 4x5mm high side MOSFET and a 5x6mm low side MOSFET requires about 495mm2 of board space. The DrMOS power stage integrates the driver and high and low side MOSFETs which reduces space compared to the discrete solution, but still requires 450mm2 of board space. Since the GaNpowIR solution can operate at double the frequency of the silicon solutions with about the same efficiency it only requires 280mm2 of board space. This translates to a GaNpowIR solution board space savings of more than 40 percent compared to a typical discrete solution and more than 35 percent compared to a typical DrMOS power stage solution. The space estimate for the GaNpowIR solution includes a 3x3mm P-Ch MOSFET and a 3x3mm Negative Voltage Generator IC. These components are included in the space measurements because one or both may be required for bias, sequencing and protection. However, many of today’s system power boards already have provisions for the bias, sequencing and protection and therefore may not be required.

Potential space saving of an iP2010-11 power stage solution

Summary

The pioneering GaN-based power device technology platform is the result of five years of research and development by IR based on the company’s proprietary GaN-on-Si epitaxial technology. The high throughput, 150mm GaN-on-Si, together with subsequent device fabrication processes which are fully compatible with IR’s cost effective silicon manufacturing facilities, offers customers a world-class, commercially viable manufacturing platform for GaN-based power devices. By taking advantage of the inherent high frequency capabilities of GaN, the iP2010 and iP2011 will allow the industry to provide the world’s highest density solutions with little or no sacrifice in efficiency when compared to traditional silicon solutions. These GaNpowIR products can also enable world highest energy saving solutions when operated in the higher end of the frequency range of today’s silicon based solutions.

 

References:

1. By Tim McDonald, International Rectifier, “GaN Based Power Technology Stimulates Revolution in Conversion Electronics”, Bodo’s  Power Systems, April 2009, p.2.

 

 

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