Will GaN replace SiC? PI's disruptive 1700V InnoMux2 is here to demonstrate

"Setting a New Benchmark for GaN Technology", the usually conservative Power Integrations (PI) rarely uses such a striking title to announce a new IC - the 1700V rated GaN InnoMux2, manufactured using the company's proprietary PowiGaN technology, is the industry's first and only 1700V GaN switch IC.

At an investor conference a few days ago, CEO Balu Balakrishnan specifically mentioned: "Many industrial customers prefer to use higher voltage ratings in three-phase applications to prevent surges and spikes, especially in areas where the AC grid voltage is unstable. At the same time, in the electric vehicle market, a 1700-volt rating is critical for flyback power supplies in 800-volt and 1000-volt battery systems, and currently only silicon carbide can solve this problem."

It is reported that when the new product was released, the CEO issued a rare letter to all employees to encourage everyone to innovate in the field of gallium nitride, which also showed PI's pride and attention to this product.

Recently, PI senior technical training manager Yan Jinguang also explained in detail the latest innovations of InnoMux2. As the first product in the 1700V GaN industry, it is truly worthy of the title of "new benchmark".

What does 1700V mean?

对于如今大火的宽禁带半导体而言，目前普遍认知是氮化镓适合中低压而碳化硅的耐压更强，同时氮化镓的成本优势显著大于碳化硅，而通过1700V氮化镓，PI再次证明了“鱼与熊掌”可以二者兼得。

Higher voltage has many benefits. With the increasing demand for power and efficiency, voltage is constantly increasing, because higher voltage means lower current, which can effectively reduce the loss during power transmission according to power P=I2R. At the same time, higher withstand voltage can also make it easier to deal with grid fluctuations.

The 1700V PowiGan can provide 80% derating at 1360V, which is very suitable for scenarios such as car chargers, solar inverters, three-phase meters and various industrial power systems, and can replace expensive silicon carbide.

PI has been continuously innovating in voltage resistance over the years. Yan Jinguang briefly reviewed PI's innovations in recent years. In 2018, PI launched the GaN product Innoswitch with integrated 750V voltage resistance, which completely changed the mobile phone charger market. In 2022, PI continued to launch 900V voltage-resistant products, meeting the 20% derating under 550VDC. In 2023, 1250V products were launched, continuing to push up the margin and durability of GaN, but "the sky is the limit", so we have today's 1700V GaN.

In fact, PI also has 1700V silicon carbide technology, but Yan Jinguang said that gallium nitride has more advantages in price, including materials, production processes, cutting, etc., which are all beyond silicon carbide. "Silicon carbide has been produced for so many years, and the cost has not been reduced enough because of the huge technical bottleneck. On the other hand, the success of gallium nitride in recent years has proved it enough." Yan Jinguang said.

Why can PI be made?

In just less than two years, PI has repeatedly broken the voltage resistance record of gallium nitride. Yan Jinguang explained the patented technology owned by PI.

Like silicon MOSFET, GaN is also divided into two types: depletion mode (D-MODE) and enhancement mode (E-MODE). GaN is normally on, that is, depletion mode. The main reason is that a high-concentration two-dimensional electron gas layer is naturally formed on the heterojunction interface between GaN crystal and other materials such as AlGaN (aluminum gallium nitride). This 2DEG layer has a high electron density and electron mobility, so it is very conductive. This feature means that when no gate voltage is applied, current can flow freely in the GaN channel, making the device conductive in the default state.

In order to improve safety, the device needs to be transformed from a natural normally-on state to an enhanced normally-off state, which requires a complex process. However, PI uses a cascode method to connect a MOSFET in series under gallium nitride, thereby achieving a safe, reliable and simple control method. This architecture also determines that gallium nitride with a higher voltage resistance can be developed. Yan Jinguang also emphasized that although the on-resistance will be slightly larger under the series method, it can ensure the high reliability and high voltage resistance of the product, so as to give full play to the true advantages of gallium nitride.

"The choice of technology route is very important. In fact, when we launched the 1250V product, the actual withstand voltage it could reach was 2100V. Now our 1700V product's actual withstand voltage can be even higher, so the future is still worth looking forward to." Yan Jinguang said.

InnoMux2 Architecture Innovation

In addition to higher voltage resistance, InnoMux2 has another innovation. When there are multiple outputs, a single chip can ensure that the adjustment accuracy of each output is controlled within 1%, thus eliminating the need for a post-stage regulator. Through unipolar voltage regulation, the efficiency of three-way or less multi-way output systems is increased by about 10%, while also saving the number of components and PCB area.

In general, InnoMux2 adopts the concept of "energy multiplexing", which multiplexes energy to each output according to immediate needs, and can provide precise and independent adjustment for each output. In addition, by sending energy to the load power rail in batches at high frequency and intelligently, the low-frequency noise of the transformer is effectively avoided. (For more information on the architectural innovation of InnoMux2, please refer to the previous article: DC-DC converters are going from dying to being replaced https://news.eeworld.com.cn/dygl/ic662043.html)

In addition, Yan Jinguang also mentioned that InnoMux-2's unique SR-ZVS technology can achieve zero voltage switching (ZVS) in multi-output flyback power supply designs without the need for active clamps or any additional devices. Through ZVS, switching losses can be reduced at 1000VDC.

As shown in the figure, PI's latest 1700V InnoMux2, compared with the previous high-voltage solution achieved through StackFET series voltage division, not only achieves multiple high-precision outputs, but also ensures maximum system efficiency and minimum cost and size.

PI reference design DER1053: A demo board that uses InnoMux2 to implement a 60W dual-output reference design. It is exceptionally simple and beautiful.

According to the measured results in the reference design, in the natural case without heat sink and forced air cooling, even at 1000VDC, InnoMux2 also exhibited amazing temperature characteristics, and the temperature rise was much lower than other components on the PCB, which shows the ultra-high energy efficiency of the product.

At the same time, PI's long-standing isolation technology FluxLink continues to be used in the latest InnoMux2. As Radu Barsan, PI's vice president of technology, summarized: "We have rapidly advanced the research and development of gallium nitride products, achieving three world-first rated voltage levels in less than two years: 900V, 1250V and now 1700V. Our new InnoMux-2 IC integrates 1700V gallium nitride technology and three other latest innovations: independent and precise multi-channel output adjustment technology; FluxLink secondary side control (SSR) digital isolation communication technology; and zero voltage switching (ZVS) technology that almost eliminates switching losses and does not require active clamping."

Gallium Nitride is going mainstream

“We developed a proprietary GaN process and device design with five key attributes in mind: cost, reliability, ease of use, voltage and power, and we are planning for each of them. We concluded early on that even with superior performance, our GaN would have to be cost competitive with silicon to achieve mass adoption. Over the past six years, we have executed an aggressive cost reduction roadmap that has brought our GaN close to state-of-the-art silicon MOSFETs, but with significantly superior performance,” said CEO Balu Balakrishnan.

Ezgi Dogmus, Marketing Activities Manager for Compound Semiconductors at Yole Group, also said: “By the end of 2029, the market size of power GaN devices will reach US$2 billion and will expand into various application areas, with more attractive cost advantages compared to SiC devices.”

Yan Jinguang also gave his own observation summary of the market: Currently in the 100W power supply market, gallium nitride has won, and in more high-power applications, even up to 100kW, gallium nitride products are also beginning to be tried.

Now, PI's ambition is not only to compete with silicon for the market, but also to "touch porcelain" silicon carbide. Whether in terms of cost or efficiency, gallium nitride is indeed superior to silicon carbide. The 1700V withstand voltage also gives PI enough courage. In the future, it will continue to make innovative combinations around high-voltage products and PI's unique circuit control technology.

“I think the future of our company is gallium nitride,” Balu said.