Driven by the development trends of new energy electric vehicles (NEVs), the demand for high power charging has become increasingly high, and gallium nitride field effect transistors (GaN FET), which support high power density, high performance, and high switching frequency, have become a popular product choice in the market. On the other hand, there are many tools and devices that use batteries on the market. In order to improve the safety and efficiency of battery operation and prolong the life of batteries, high-efficiency MOSFETs must be used for battery isolation. This article will show you the development of GaN FET and efficient battery isolation technology, and the product characteristics of GaN FET and dedicated battery isolation MOSFETs introduced by Nexperia.
GaN power technology meets the demand for efficient power conversion
One of the main challenges facing industrial applications today is to reduce power loss. In the face of growing pressure from society and increasing government legislation to reduce CO2 emissions, many industries are investing in more efficient power conversion and increased electrification, including automotive electrification, telecommunications infrastructure, server storage, and industrial automation, with significant growth in the use of electric and electronic products. This, in turn, leads to increased demand for efficient, innovative, high power field effect transistors (FETs) based on gallium nitride (GaN) technology.
In the semiconductor industry, the innovation of power devices is mostly driven by increased power conversion efficiency. GaN technology shows the greatest performance advantage over silicon (Si) and silicon carbide (SiC) solutions across a wide range of technologies. Specifically, GaN FETs provide optimal efficiency at lower system costs while making the system lighter, smaller, and cooler. Since the introduction of power GaN transistors, particularly GaN-on-Si devices, there have been significant improvements in performance, reliability, cost, availability, and a more powerful GaN power transistor can be used to drive higher power.
GaN has very high electron mobility which allows for the creation of devices with low on-resistance and very high switching frequency. These advantages are critical in next-generation power systems, such as electric vehicles (EVs) and renewable energy applications, and are well suited for applications in data centers, telecommunications infrastructure, and industry.
High-quality and highly robust high-power GaN FETs
Whether it is a motor drive/controller designed for next-generation NEVs or a power supply designed for the latest 5G telecommunications network, Nexperia's GaN FET will be the key to your solution, providing high power performance and high frequency switching. The design and structure of these normally-off GaN FET products ensures that low-cost standard gate drives can be used in your design.
Nexperia's cascode GaN FET offers high power density, high performance, and high switching frequency, which is a unique solution that facilitates the use of a well-known Si MOSFET gate drives for easy driving. In addition, unlike other solutions on the market, it has unmatched high junction temperatures (Tj [max] 175°C), design freedom, and improved power system reliability.
Nexperia's GaN FET portfolio is available in CCPAK and TO-247 packages. Nexperia brings with it nearly 20 years of experience in producing high-quality and highly robust SMD packages. CCPAK provides industry-leading performance with truly innovative packaging. It is wire-bond free for optimized thermal and electrical performance and has a simplified design with a cascode configuration to eliminate the need for complicated drivers and controls.
GaN FET products in the CCPAK package used by Nexperia adopt innovative copper clip package technology featuring 3 times lower inductances than industry-standard packages for lower switching losses and EMI and higher reliability compared to wire-bond solution. They have excellent thermal performance with low Rth(j-mb) typical (<0.5 K/W) for optimal cooling. They offer manufacturability and robustness with flexible leads for temperature cycling reliability, flexible gull winged leads for robust board levels and compatibility with SMD soldering and AOI. There are two cooling options, including bottom-side cooling (CCPAK1212) and top-side cooling (CCPAK1212i), with increased design flexibility and further improved heat dissipation. They are compliant with AEC-Q101 and MSL1 specifications and halogen-free devices. At present, the main products include GAN039-650NBB, GAN039-650NBBA, and GAN039-650NTB which support 650 V and 33 m Ω, and these three GaN FETs are packaged in CCPAK.
In addition, combining Nexperia's package expertise with industry standard TO-247 produces high-quality, highly robust GaN FET products to meet the most demanding applications with unmatched reliability. Nexperia's GaN FET product in the TO-247 package provides high performance (> 99% efficient), low dynamic characteristics, the lowest WBG loss in reverse conduction, and leading soft switching performance, which is fairly easy to drive and supports 0 to 12 V gate drives. GaN FET product lines in the TO-247 package include the GAN041-650WSB that supports 650 V and 35 mΩ, and the GAN063-650WSA that supports 650 V and 50 mΩ.
High energy density batteries require efficient battery isolation
The past few years have witnessed the rapid development of battery-powered cordless tools and outdoor power equipment that have a good mix of power and battery life, while being relatively light and easy to use. One of the key drivers of this trend is the emergence of the 10-cell 36V lithium-ion battery packs with a long service life, which, because of its high energy density, is well suited to professional tools and for traditional corded equipment, including engine-driven outdoor electric equipment, such as chainsaws and lawn mowers. However, they are even more in need of efficient battery isolation because of their increased energy density.
These hand-held and battery-powered tools and equipment use multi-cell lithium-ion battery packs, while having the advantage of high energy density, and can be problematic with the potential for a massive uncontrolled energy discharge in a fault condition, resulting in over-heating of loads and potential circuit fires. Batteries must be safely isolated and large amounts of discharge must be handled in a controlled manner before the system switched-off, requiring very robust and thermally efficient MOSFETs.
At standard MOSFET voltage ratings, designers use 60V MOSFETs for 36V batteries. However, for the nominal rating of 36V, a MOSFET using 50V or 55V is ideal. Reducing MOSFET voltage ratings provides the opportunity to optimize the safe operating area (SOA), drain current (ID) rating, and avalanche capability, thereby improving overall safety and efficiency.
Battery isolation MOSFETs usually enter a linear mode when deep discharges occur due to the voltage generated at both ends of the circuit inductance at high currents. Maintaining a stable SOA is therefore essential. In addition, a battery isolation MOSFET is usually placed away from the load and may experience unclamped inductive spiking (UIS). Optimizing the VDS voltage (50V) to bring it closer to the battery voltage (36V) helps reduce the dissipative power by at least 20% (compared to 60 VDS part) and avoids potential failures. Given that typical applications often operate in harsh environments, avalanche events may be common.
In response to battery isolation needs, Nexperia introduced a new 50/55V dedicated MOSFET, which provides the necessary SOA and robustness, as well as significantly improved efficiency and high rated power with an overall size of 5*6 mm. In addition, Nexperia's MOSFET technology provides excellent SOA functionality, optimizing discharge performance from 1 ms to 10 ms using a 50/55V ASFET (Application-Specific FET). An example is the PSMN1R5-50YLH, a product that handles discharges of up to 5A at 40V for up to 1 ms. On the other hand, Nexperia's PSMN1R5-50YLH has an optimized avalanche capability with a single-phase avalanche rating (EAS) of 2000 mJ (at 25A current) and is able to withstand such events repeatedly.
With the release of these dedicated 50/55V ASFETs, Nexperia became one of the first companies to provide 50V rated MOSFETs specifically for 36V battery systems. The product is optimized for SOA, ID rating, and avalanche capability while maintaining good RDS(on), providing a very stable battery isolation solution for designers. It provides industry-leading performance with a DC battery rating of 200A and a calculated silicon limit of 312A, and is built based on Nexperia's mature battery isolation ASFET portfolio.
Enhanced MOSFETs powered by 36V battery for high load current
Nexperia's ASFET portfolio for battery isolation is specifically designed for multi-battery powered devices and is ideal for the most robust LFPAK package devices. In the event of a fault, since the circuit inductance at high current produces a voltage when a deep discharge is caused by a fault, battery isolation MOSFETs usually enter a linear mode, and an enhanced SOA MOSFET can continue to operate safely and controllably until it is switch off, completely isolating the battery from the load circuit.
Low RDS(on) is required to achieve low conduction loss during normal operation, but parameters need to be optimized to achieve safe battery isolation. This robust battery isolation MOSFET can be used as the primary protection for device approval and is suitable for applications that may require low Vt because a battery protection IC may only have a 2-3V gate drive capability.
In addition to the PSMN1R5-50YLH, Nexperia's ASFET portfolio includes the PSMNR70-40SSH, an N-channel 40V, 0.7 mΩ, 425A logic level MOSFET using an LFPAK88 package, the PSMN1R0-40ULD, an N-channel 40V, 1.1 mΩ, 280A logic level MOSFET using an SOT1023A package, and the PSMNR51-25YLH, an N-channel 25V, 0.57 mΩ, 380A logic level MOSFET using an LFPAK56E package.
Nexperia’s PSMN1R5-50YLH, developed for efficient isolation applications for 36V batteries, is an N-channel, 50V, 1.7 mΩ, 200 Amp continuous current and logic level gate drive enhanced MOSFET using an LFPAK56E package. As part of the ASFET portfolio for battery isolation and DC motor control series, Nexperia's unique “SchottkyPlus" technology is used to provide high efficiency switching and low spiking performance typically associated with MOSFETs with an integrated Schottky or Schottky-like diode but without a problematic high leakage current. An ASFET is especially suitable for 36V battery-powered applications that require strong avalanche capability, linear mode performance, high switching frequency, and safe and reliable switching at high load currents.
The PSMN1R5-50YLH is optimized for 36V (nominal) battery-powered applications. The LFPAK56E package uses a low-stress exposed lead frame with extremely high reliability, optimal soldering, and easy solder joint inspection. It can be used for low package inductance and resistance, as well as copper-clip and solder die attach with high ID(max) ratings. It can operate at 175°C, support avalanche rated, and be 100% tested, especially at high switching frequency. It can be efficient with low QG, QGD, and QOSS.
The PSM R5-50YLH has an ultra-fast switch with soft body-diode recovery, which can achieve low spiking and ringing. It is recommended for low EMI designs. It has a narrow VGS(th) rating, which facilitates parallel connections and improves current sharing. It has a very strong linear mode/SOA characteristic, and can switch safely and reliably under high current conditions. The PSMN1R5-50YLH can be applied to brushless DC motor controls and synchronous rectifiers in high-power AC-DC applications, such as server power supplies, battery protection and battery management systems (BMS), load switching, and 10-cell lithium-ion battery applications (36V - 42V).
Conclusion
In key EV and industrial applications, GaN FETs have excellent performance for on-board charging, DC-DC converters, traction inverters, solar (PV) inverters, AC servo drives/inverters, battery storage/UPS inverters, etc. Nexperia's GaN FET portfolio is available in CCPAK and TO-247 packages. They are high-quality, highly robust GaN FET products that meet the needs of various high-power power applications.
In addition, as more and more battery-powered devices are used, it is necessary to provide higher power densities and maintain a small form factor. Therefore, there is an increasing demand for high power density lithium-ion battery packs, but at the same time, it is necessary to maintain the safety and robustness of the batteries. Therefore, battery isolation MOSFETs play an important role. Nexperia’s GaN FETs and battery isolation MOSFET introduced herein features high performance and efficiency and is the best partner for battery-operated devices, which deserves your further understanding and adoption.