With the introduction of Apple’s new generation of 140W gallium nitride (GaN) fast charging, GaN has further entered the public eye. GaN has a switching speed 20 times faster than silicon, and a band gap 3 times faster. Natural advantages can make the overall power supply design higher power density, making the overall power supply solution smaller in size and weight. But as a new material device, GaN still needs a lot of new technology accumulation to support it in order to play its real advantages. “The split GaN power solution can increase the power density to 2 times or 3 times that of the traditional silicon solution, but it is far from reaching the 1W/cc figure.” Huang Xiucheng, Senior Application Director of Nanomicro semiconductor, shared, “The integrated solution of Nanomicro Semiconductor The switching frequency and speed advantages of GaN can be fully released. Many of our cases have been far greater than 1W/cc.” Recently, Navitas Nano Semiconductors released a new GaNSense technology, which further improved the integration level on the basis of GaNFast.
GaNFast: Only integrated solutions can realize the potential of GaN
At present, there are two main schools of power GaN. As shown in the figure below, one is the dMode normally-on type. This technical route requires an additional silicon FET cascade configuration in addition to GaN. It can also be combined with controllers and GaN. Seal them together to form an integrated solution. The other is the eMode normally-off type, which requires a special gate driver to drive GaN. In the eMode normally-off technology route, an integrated solution that integrates control, drive, and protection on a single chip is represented by GaNFast of Nanomicro Semiconductor. According to Huang Xiucheng’s sharing, the complexity of GaN drive circuits is relatively high, and the discrete solution does not integrate the drive into the power device. Due to the influence of the layout and wiring parameters of external devices, the switching frequency has not been brought into full play. the height of. GaNFast integrates control, drive and protection in it, so it does not depend on the influence of external integrated parameters, so the designed power density is much higher than traditional silicon or discrete gallium nitride.
But GaNFast is not the end of the highly integrated normally-on GaN power device. Less than a month after Nanomicro Semiconductor’s U.S. stock market went public, GaNSense’s new technology was released, integrating more competitive functions for GaNFast: lossless current sampling, over-current protection, over-temperature protection and smart standby.
New GaNSense technology: further integration of GaN power solutions
The GaNFast power chip supported by GaNSense’s new technology has achieved breakthroughs in intelligent GaN solutions in four major areas.
The method of lossless current sampling is to collect the current signal of some representative cells on the GaN crystal element, and then convert the current to voltage, and finally output to an external programmable resistor as a current source, and adjust the size of the resistor to recover. There is a current flowing through the GaN. According to Huang Xiucheng’s sharing, taking the NV6134 as an example, although the specification indicates a certificate deviation of 4 to 5%, thousands of test results show that the sampling error is about plus or minus 1.36%, and the sampling accuracy is very high. high.
This lossless current sampling scheme can cancel the sampling resistor in the traditional scheme. This loss is completely saved, and the on-state loss of the loop will be halved, thereby achieving the effect of improving energy efficiency; in addition, it further saves PCB area and achieves more Flexible and compact layout; after removal, the thermal coefficient will be better, the coupling coefficient will be lower, and the operating temperature of the device itself will be lower, the overall efficiency of the system will also be improved.
The overcurrent protection is based on the sampling signal to set an overcurrent threshold inside the GaN power chip. The traditional discrete solution, including the previous GaNFast integrated solution, requires an external sampling resistor to be connected to determine whether an overcurrent situation occurs. In order to avoid the noise problem, the controller sets a delay of 300ns. And now the internal threshold response time of GaNSense is far less than 100ns, and the saved 200ns can avoid the deterioration of the transformer current caused by abnormal conditions such as short circuit and overpower.
According to Huang Xiucheng’s sharing, if the current signal touches the internally set threshold, no matter whether the PWM signal of the external controller is high or low, it will be directly shut down, thereby protecting the serial current in the system from continuing to expand beyond the threshold. This is a cycle-by-cycle protection method that precisely controls the overcurrent point within the threshold.
The over-temperature protection method is also to collect the temperature of the GaN wafer. When the temperature exceeds the set threshold, the chip is directly turned off regardless of whether the external PWM control signal is high or low, allowing the chip to cool naturally. After the chip cools below the threshold temperature, it will re-reference the external PWM signal to determine whether it needs to continue working. This is different from the overcurrent protection, which is not in a cycle-by-cycle manner, but it can precisely control the range of the temperature range within the interval.
The smart standby function is a further step on the basis of GaNFast’s previous technology. Although the internal quiescent current of GaNFast was only 700u~1mA in the early days, in order to pursue better standby power consumption, it is still necessary to arrange circuits externally and cut off VCC during standby to reduce chip power consumption. The current GaNSense technology is more complete, allowing the chip to enter the standby mode by intelligently detecting the PWM signal. When the chip detects that the PWM signal is in a periodic mode with a non-operating frequency, it will let the chip enter the standby mode. At this time, the standby current will be reduced from about 1mA to about 100uA. In addition, the speed of wake-up is also very important. The new generation of GaNFast supported by GaNSense can return the chip to normal operating mode within 30ns. According to Huang Xiucheng, on the same platform, after replacing the early GaNFast chip with a new generation of GaNFast supported by GaNSense, it can achieve a power saving of 6-7mW, and the standby power consumption is close to 20%, which is a very good performance.
From R&D, production to full-chain AE support: Nanotech helps GaN customers to innovate
From the introduction of the technical details of GaNSense above, we can see that many technologies need to be implemented at the wafer level. For traditional silicon chip manufacturers, this is a brand new technology accumulation, which is based on Si and SiC devices. Some technological accumulation cannot be directly used in the design of GaN, and these technological innovations of GaN require the close cooperation of the fab to carry out process design improvements together. According to Li Mingzhao, Director of Sales and Operations of Nano-Micro Semiconductors, Nano-Micro is now mainly produced in TSMC’s No. 2 factory, mainly producing 6-inch wafers. In the packaging part, the world’s top three packaging manufacturers are used to achieve zero-fault quality control. Now a total of 30 million GaN power chips have been shipped, and zero failures have been confirmed. The yield capacity is over 90%, and the delivery time is about 12 weeks.
In the upstream and downstream cooperation of the industry chain, Nanomicro Semiconductors has also been closely cooperating. According to Xu Yingchun, in the earliest product development stage of Nanomicro Semiconductors, many magnetic core manufacturers sent magnetic cores to Dr. Huang Xiucheng for evaluation on how to apply them to the field of gallium nitride, including magnetic cores, magnetic rings, and filters. Power converters and transformers are very important, accounting for 25% of the cost of the power supply. The second is electrolytic capacitors. Nanomicro Semiconductors cooperates with head manufacturers to obtain customized products to be applied to GaN. The third is the very core technologies such as PCB and flat-panel transformers, which are also led by Dr. Huang Xiucheng. It is the close connection of these entire upstream ecosystems that enables downstream end customers and ODM customers to focus on their product development.
A brand-new device such as GaN will also bring a brand-new design, so for customers, the work of support is equally important. Nanomicro has deployed a strong AE team in China, from the customization of customer needs, the discussion of requirements, to the drawing of schematics, to the design of the entire layout, to the assembly of the structure, to the EVT (electrical performance prototype test) , To the final EMI debugging of the entire detailed design stage, to small-batch trial production, medium-batch trial production, to large-volume mass production, Nanomicro provides full service. With this support, more than 140 GaN charger projects have been mass-produced, and more than 150 cases are being developed, which have been recognized by more than 90% of brand owners.
The application of power GaN is more than fast charging
Although GaN power devices are currently used in consumer fast charging applications, their excellent characteristics are not limited to fast charging, but also drive innovation in data centers, electric vehicles and other applications. Nanomicro Semiconductor does not just want to be a provider of fast charging power solutions, but will continue to focus on data centers and automobiles. According to Li Mingzhao, traditional GaN manufacturers start from the industrial and automotive industries. Unlike the GaN manufacturers at the beginning, Nanomicro Semiconductors is to start with the consumer products and increase the overall GaN volume. Prove technology, build production capacity and surrounding ecosystems in the market. Through the huge market of a large number of consumer applications, the entire industry chain is driven to keep up. In Nanomicro’s plan for the next five years, the server is the second step, the third step is the industrial development, and the fourth step is the automotive development.
The European Union requires that the highest efficiency point of the data center efficiency curve be increased to 96% by 2023. To achieve such a performance, the traditional silicon topology will increase a lot of costs. The GaN solution will have better cost and performance, which can save 1.9 billion in electricity bills every year. Therefore, Nanomicro Semiconductors regards the data center as its second main application direction after the consumer fast charging market has been won, and has established a dedicated team.
In addition, in the field of solar energy, the GaN solution can reduce the size of the Inverter, reduce its cost by more than 25%, reduce energy consumption by more than 40%, and shorten the return period of investment, thereby promoting the application of residential solar energy. It is reported that this market opportunity for GaN power chips will be USD 1 billion/year.
In the field of electric vehicles, the main force of GaN is the OBC and DC/DC parts. At present, some patented technologies of GaNFast, such as OCP, OTP protection, etc., can be applied to automotive applications. But for example, lossless sampling, etc., it is necessary to add some isolation functions to meet the requirements of automotive applications. At present, Nanomicro Semiconductors has also begun research and development in this area. It is reported that Nanomicro Semiconductor and foreign auto parts production companies have already had a cooperation, and will start a large project with European auto manufacturers.
“Now, gallium nitride is constantly moving upwards, with voltage levels, current levels, and power levels constantly moving upwards. So Nanomicro’s future layout includes servers, data centers, EVs, etc., and we continue to explore gallium nitride upwards. “Huang Xiucheng shared,” There is no limit to the upward exploration of gallium nitride itself. We will produce devices less than 20 milliohms by the end of the year or next year. This means that we can achieve a single power of 3.3 kilowatts to 5 kilowatts. In the future, we will make this module, such as 3 dies, or several dies, as bridge walls for parallel connection, etc., and soon the power level will be from 10 kilowatts to 20 kilowatts, 30 kilowatts, EV charging piles, and even the main drive of electric vehicles. They were all in our plans. At that time, looking at gallium nitride was completely another keynote. This is our judgment on the future market.”
The blessing of GaNSense’s new technology has further improved the integration and intelligence of the new generation of GaNFast chips. Based on this, the customer’s overall plan design can also become more concise and efficient. Just like Nanomicro Semiconductor’s vision, after starting from the demand for GaN chips in the consumer market, GaN will play its value in more applications in the future. In five or ten years, GaN chip applications will be a bigger market.
Remarks: GaNSense and GaNFast are registered trademarks of Nanomicro Semiconductors