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Qorvo has unveiled the industry’s first 4-milliohm silicon carbide (SiC) junction field effect transistor (JFET) housed in a TOLL package. This achievement marks the lowest on-resistance among 650V to 750V power devices in standard discrete packages, substantially minimizing heat generation. With the use of the compact TOLL package, the UJ4N075004L8S reduces solution size by 40% compared to conventional TO-263 packages, addressing the spatial constraints of modern electromechanical circuit breakers. Its superior thermal performance eliminates the need for extensive cooling systems, thus expediting the transition to semiconductor-based solid-state circuit breakers (SSCBs).
In an interview with Power Electronics News, Andy Wilson, senior business development at Qorvo, highlighted the importance of this new solution for circuit protection applications including solid-state circuit breakers, where low resistance, superior thermal performance, small size, and reliability are paramount.
“We are thrilled to announce the introduction of a groundbreaking 4-milliohm JFET device, a significant advancement in circuit protection technology, particularly within the realm of solid-state circuit breakers. This development is poised to transform the industry,” said Wilson.
Qorvo’s most recent JFET is capable of withstanding high instantaneous junction temperatures without parametric drift or degradation. The JFET’s normally-on state facilitates its seamless integration into systems in which the switch is in the on-state by default and in the turn-off state under fault conditions.
The UJ4N075004L8S is currently available for sampling, and full production will be in Q4 2024. The SiC JFET family will be supplemented by variants, such as 750V with 5 milliohm and 1200V with 8 milliohm ratings, both of which are packaged in TO-247.
Solid-State Circuit Breaker Market
The market for solid-state circuit breakers (SSCB) is rapidly emerging, driven by the need for advanced circuit protection and efficiency. According to Wilson, while electromechanical circuit breakers have long been the industry standard, the past 18 to 24 months have seen a significant uptick in the development of solid-state alternatives. This shift is fueled by the superior performance characteristics of solid-state technologies, such as faster response times, greater reliability, and improved energy efficiency.
JFET technology, in particular, is an ideal fit for SSCBs. JFETs offer low conduction loss, high thermal stability, and the ability to interrupt high currents, which all make them well-suited for modern power distribution and protection needs. As the demand for more robust and efficient electrical systems grows, the adoption of JFET-based SSCBs is poised to increase, marking a significant advancement in circuit protection technology that paves the way for more resilient and efficient power management solutions.
Challenges and Solutions in High-Voltage Applications
In low-voltage applications like 12V or 48V e-fuses, silicon remains the dominant technology due to its cost-effectiveness and compact size at lower-rated voltages. However, for high voltage applications, particularly those requiring 230 V AC and currents exceeding 10A, silicon-based solutions face significant limitations unless advanced cooling methods are implemented. Given that the trend is to develop SSCBs that can be installed into existing circuit breaker panels that have limited cooling, the goal is to reduce the overall resistance of the semiconductor switch to reduce the amount of heat that is generated. Given this constraint, silicon carbide (SiC) emerges as a superior alternative due to its substantially lower RDS(on) within the same package size, enhancing efficiency and performance.
“Although SiC MOSFETs are viable, we prioritize JFETs for their superior performance,” said Wilson. “JFETs not only achieve a lower RDS(on) in a comparable package size, but also offer greater robustness.”
“For instance, our new 4-milliohm SiC JFET outperforms a 22-milliohm silicon solution in the same package, implying that five silicon devices would be necessary to match the thermal performance of a single SiC JFET. This highlights the significant advantages of SiC JFETs in high-power applications, ensuring efficiency and reliability.”
Development and Testing of JFET Technology
According to Wilson, collaborations with key customers highlighted that their current cascode solution, optimized for high-frequency switching in power conversion, falls short in circuit protection applications. Circuit protection demands relatively slower switching to manage energy absorption during switching events.
“Consequently, we’ve developed a new line of SiC JFETs tailored for circuit protection. These intrinsically robust JFETs can withstand unlimited high current events without degradation. This robustness is essential for safely handling the significant current surges and high inrush currents characteristic of fault conditions, including short-circuit events,” said Wilson.
In circuit breakers, where current can surge to 20x the nominal rated current during short circuits, JFETs must handle high inrush currents and absorb significant energy. Qorvo plans to test 100 4 milliohm JFETs switching over 350A at 100°C case temperature for 1.5 million cycles. Key parameters like thermal resistance, leakage current, threshold voltage, and RDS(on) will be measured before and after testing. According to Wilson, preliminary tests indicate no parameter drift, with future rounds including competitor parts.
Key Advantages and Market Adoption
Despite current cost disparities with electromechanical solutions, solid-state options provide benefits like remote connectivity and load management. Emerging standards (UL 489I, IEC 60947-10) will boost adoption.
“Qorvo’s IoT-enabled microprocessor integrates with our JFETs, enhancing control of circuit breakers. While solid-state solutions gain traction in safety-critical sectors like aviation and rail, broader industrial adoption will follow as silicon carbide costs drop, driven by the EV market. Advancements from our third to fourth-generation products show promising RDS(on) reductions, indicating further innovation potential,” said Wilson.
Although regulatory standards like UL 489I in the US and IEC 60947-10 in Europe are still evolving, their development supports the adoption of solid-state solutions. Future circuit protection will integrate technologies like JFETs, providing superior performance and robustness.
“Our ongoing advancements aim to introduce these innovative solutions, ushering in a new era of safety, efficiency, and reliability in circuit protection,” said Wilson.
The post Advancing Circuit Breakers: New 4-mΩ SiC JFET Redefines Power Device Standards appeared first on Power Electronics News.
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