Pay Attention to These Power-Device Trends

In the world of power technology, scores of new information on the lowest, highest, smallest, densest, etc., seemingly arrives daily, leaving engineers to scramble to keep up with the latest trends. It’s those engineering teams carefully considering and selecting the latest power devices and related circuits that will likely reap the most significant performance gains. For designers starting new projects, this quick update will help in that effort—and may even influence the direction of future change.

For decades, breakthroughs in technology have reshaped the power-device landscape. And the beat goes on with the latest crop of innovative device structures, thinner wafers, higher cell densities, new materials, greater integration, and new packaging technologies(see the figure)。

Whether it’s higher conductivity, faster switching, more robustness, or a combination thereof, progress is evident across most product categories. Compared to a just few years ago, systems engineers working on new designs have significantly better power devices at their fingertips. This, of course, spawns multiple benefits:

•More performance:In addition to the aforementioned performance enablers, stratification of power-device types into many sub-families has improved performance for narrowly targeted applications. These include MOSFETs with diodes optimized for several classes of reverse recovery time (t_RR），或带有延长短路的IGBT承受时间（t_SC) options.
•More packages:Taking full advantage of better devices at a system level requires new packages for smaller size, higher switching speeds, less resistance, less inductance, more integration, better thermal performance, etc.
•More applications:Power-semiconductor content continues to expand as demand grows for greater energy efficiency in applications such as handheld devices, vehicle electrification, grid storage, renewable energy, and motor-drive “inverterization.” Thus, there’s a broad trend toward higher unit volumes. On top of that, devices that feed these specific applications will likely receive more development resources while rapidly advancing up the performance ladder.
•More suppliers:Despite recent consolidations, the power-device business overall continues to add suppliers. In particular, IGBTs and wide-bandgap (WBG) devices are available from both traditional and “startup” suppliers, creating a greater array of new part, performance, integration, and packaging options. As a result, the relationship between power-device OEMs and their customers has become more important than ever.

Digging deeper on the last bullet point, power-device performance and selection is inherently tied to a load, inductor, capacitor, or heat sink that’s typically engineered on the system side. To ensure full capture of these device-level innovations at the system level, communication between power-device engineers and systems engineers is paramount. One sub-plot to it all, though, involves second-sourcing of discrete components—it’s become more difficult due to increased optimization of power devices for specific uses, meaning greater complexity when trying to match performance across suppliers.

Taken together, power semiconductors currently reside in a dynamic era of “more of everything,” particularly from the viewpoint of device users. What follows are some of the biggest movers and shakers.

25至30-V MOSFET
在行业中的主导地位，25至30-V_DS用于DC-DC下调的MOSFET在计算应用程序中使用的MOSFET位于顶部。四个突出的趋势突出了这个领域：

•Markedly improved silicon performance:Just a few years ago, the drain-source resistance (R_DS(ON)）对于表现最佳的SyncFets，是当今包装最佳设备的两倍（Syncfets是Fairchild的原始名称，用于具有整体Schottky Diodes的FET）。高侧FET也发生了类似的改进。现在，此类FET偶尔会在完全独立于SyncFET过程的以切换性绩效为中心的过程中开发。
•The move to 3-by-3 DFN packages and asymmetric half-bridge dual MOSFETs:These have replaced 5-by-6 dual flat no-lead (DFN) packages in many applications, much like when 5-by-6 DFNs replaced DPAKs just as a few short years ago. The move is consistent with the industry-wide trend of miniaturized integrated devices targeting applications demanding higher performance. These packaging transitions occurred within just three to four years.
•More integration for greater performance gains:To effectively reduce size, increase efficiencies, and push switching speeds to and beyond 1 MHz requires minimization of package resistance and related parasitic effect. That means greater emphasis on integration of FETs, drivers, and controllers. Integrated dc-dc converters can be partitioned in various ways. For example, asymmetric dual MOSFETs (two die in one package) come in 5-by-6, 3-by-3, or other sizes widely used in downconverters to 30 A and beyond. Or two MOSFETS plus drivers (three die in one package) can create “DrMOS” (driver-MOSFET, an Intel packaging standard) and similar multichip module devices in various packages, which handle up to 60 A at frequencies over 500 kHz. Further, two MOSFETs plus a driver and a controller (three or four die in one package) could form a point-of load (POL) device and run almost as high a current as the DrMOS type parts. Finally, monolithic components that combine the controller, driver, and high- and low-side MOSFETs in a single die can run to 15 A, with efficiencies near 90% from 100 mA to 15 A even when stepping down to 1 V from 12 V.
•Further segmentation counter trend:On the other hand, continued strong supplier support for the 25- to 30-V commodity zone may retard segmentation. For this segment, device performance significantly lags the cutting edge.

40- to 250-V MOSFETs
Key trends in this sector include:

•Many more available parts:现在更多的供应商为汽车开发电力设备drives in 48- to 80-V systems, synchronous rectification for ac-dc SMPS, isolated dc-dc converters for telecom/datacom, class-D audio amps, and UPSs.
•改进的技术：In terms of potential performance, the new SiC and GaN semiconductor technologies developed for this segment is far superior to conventional silicon. It increased efficiency and power density, thus minimizing paralleling and board-space requirements.
•Optimized SSR devices:固态 - 列层（SSR）设备已针对R进行了优化_DS(ON), switching, and diode recovery losses. Low-gate charge, low-output capacitance, and reduced body-diode recovery charge helped shrink losses in non-resonant switching circuits.

400-V+ MOSFETs
The over-arching trend here revolves around high-voltage super-junction devices:

•带有更宽的电压范围的超级开关MOSFET：从传统的600 V基地，这些设备现在可用于1200V。
•Trench-based alternatives:使用深度沟通进行电荷平衡，而不是多级ePitaxial设备（至少低于650 V）提供了Q_Gand Q_GD（门电荷的两个不同定义）的优势导致切换损耗减少，但R仍然很低_DS(ON)。
•Thin SMD packaging:Low z-height surface-mount devices (SMDs), as opposed to TO-263 or TO-252, reduce size and parasitic inductances.
•Arrival of new varieties, like faster body diodes:零件更好t_RR(150 ns and lower) for hard-switched applications have become more prominent.
•Wider application of super-junction MOSFETs:这些设备现在正在进入消费者应用程序（例如LED照明），AC-DC反式反射和用于太阳能和电池充电器的低功率太阳能逆变器。

IGBTs
Insulated-gate bipolar transistors (IGBTs) have long maintained an amperes-per-dollar edge over MOSFETs, and that remains the case today. However, IGBTs are changing in many other ways:

•通过权衡提升绩效：由于传导性能之间的三路权衡，最近的重大改进以及即将到来的改进将实现并将实现（如V_CE(SAT)), switching performance (as measured by tF), and ruggedness (as measured by t_SC). For example, 100-A IGBTs with 10-μs t_SC现在可以使用典型V_CE(SAT)= 1.5 V @ 50 a和t_F= 80 ns. Just a few years ago, such a performance level would have required a device with a much lower t_SC。
•Availability of higher-current IGBT die:Such die, rated to hundreds of amperes, can help lessen the need for paralleling IGBTs, which brings added design challenges.
•Better monolithic reverse-conducting IGBT performance:The spike in performance makes it possible to reach more applications like resonant converters and small motor drives.
•Continued dominance of modules:出于成本和设计灵活性的原因，一个推测的趋势是从模块到基于离散的设计的逐步迁移。不过，这没有发生。但是，模块对于性能，大小和设计简单性的集成优点仍然是强大的特征。具有与硅 - 卡比德（SIC）二极管相匹配的IGBT的混合模块已出现，以进一步解决IGBT限制。即使是完全基于SIC的解决方案也可以找到。
•IGBT和MOSFET仍然特定于应用程序：Despite significant performance improvements from both IGBTs (faster) and MOSFETs (lower R_DS(ON)), there’s been little sign of traditional MOSFET applications moving to IGBTs or vice versa.

WBG Devices
宽带gap趋势表明这些设备正在进攻，尽管它很慢：

•Dominant footing in some spots:一个普遍的看法是，在WBG设备的广泛采用之前，成本必须降低。但是，当条件正确时，例如高端电源的功率因子校正（PFC）二极管插座，WBG设备的性能在尝试达到严格的效率标准时就会超过其更高的成本。
•WBG开关的采用仍然很低：To justify the use of higher-cost WBG devices, a system overhaul, including shrinking heat sinks, inductors, and capacitors, is needed to reduce cost and boost performance. This is even evident for applications such as renewable energy (or electric vehicles)—straight device performance directly translates into better end-product performance, yet WBG can’t seem to make a dent.
•降低成本最终将加速采用：这是一个协同的循环 - 采用greater会降低成本，这将推动更大的采用。早期进入，例如1200-V SIC MOSFET进入以前纯净的IGBT领土（例如，高功率太阳逆变器），将催化此循环。

Packaging Trends
Breakthroughs at the silicon level (or GaN or SiC) often necessitate better packages to take full advantage of the possible performance, as well as skirt the parasitic inductance and resistance limitations of traditional packages. Examples include leadless or minimal-lead SMD packages to replace TO-263s and TO-252s, the use of chip-scale packages for low z-height requirements, and embedded packaging to maximize thermal performance. Another example is the hole-less TO-247 package. These packages enable larger devices and offer increased power output compared to standard TO-247s.

另一个趋势是wire-bo的部署nding alternatives. Straps and clips can often replace wire bonding to maximize performance. Clips even enable higher currents in new packages, allowing migration away from through-hole packages such as TO-247s. Also trending is a rapid increase in integration. Development of new modules and multi-chip packages has sharply risen across all power levels, particularly for very-low and very-high voltages.

Power devices are no longer just a mix of a few TO-247 and TO-263 devices. A complex interaction of device R&D and packaging advances, plus a growing application, customer, and supplier base, have quickened the pace of power-device evolution. Designers can adopt simple practices to take advantage of these developments:

•Check datasheet revision dates on power-device choices. If the part is more than three or four years old, significantly improved devices are probably available.
•Look beyond previously preferred suppliers for better alternative devices.
•检查新的软件包选项。如果有更好的版本可用，但缺乏正确的设备评级，则供应商可能会根据要求在新包装中提供首选硅。
•如果电源设备对性能至关重要，请与供应商保持自定义解决方案的密切关系。
•更改产品，例如IGBT，而不是MOSFET，或者WBG而不是任何一个，以创造新的机会。