ROHM’s Expanding Lineup of Power Devices

Introduction

ROHM is taking advantage of technology cultivated in the consumer electronics sector to actively advance product development for industrial equipment. In the field of semiconductor power devices that support greater energy savings, energy creation, and energy storage ROHM is mass producing silicon carbide (SiC) semiconductors that provide breakthrough characteristics which cannot be achieved using silicon. And even for conventional silicon semiconductor power devices, ROHM is developing hybrid products that leverage its collective strengths covering a range of solutions, from discrete semiconductors to ICs. The following is an introduction to just a few of these products.

The Increasing Adoption of SiC Power Devices

SiC power devices are made up of silicon carbide, a compound semiconductor composed of carbon and silicon. For many years SiC power devices were seen as the successor to silicon due to their superior characteristics and performance, and have recently begun to permeate into virtually all aspects of everyday life. (Figure above: SiC Power Devices are seeing increased adoption)

Examples of products that utilize SiC devices (including some that are still under development):

● Residential/Consumer: Computer power supplies, solar power conditioners (for home use), air conditioners

● Industrial: Data centers, UPS, robot delivery systems in factories, induction heating (IH) equipment, high frequency power supplies, solar power conditioners (for commercial use such as in solar power plants)

● Public/Commercial: Electric cars (on-board chargers), fast charging stations, generators, medical diagnostic equipment

ROHM leads the industry in all aspects of SiC power devices, from research and development to mass production. Below is a brief introduction to ROHM’s SiC power device product lineup and their characteristics.

1. SiC Schottky Diodes

Though over a decade has passed since the world’s first SiC Schottky barrier diodes were mass produced in 2001, ROHM became the first Japanese manufacturer to mass-produce SiC Schottky diodes in 2010. Currently, 2nd generation product development is underway, which will reduce forward voltage by 0.15V compared to older 1st generation products while maintaining extremely short reverse recovery times. (Figure 2)

               Figure 2. SiC Schottky Barrier Diode Forward Voltage Comparison (650V/10A Class)

Two breakdown voltages, 650V and 1200V, are available in numerous package types, including TO-220 (isolated/non-isolated), TO-247 and D2PAK. In addition, since reverse recovery loss can be significantly reduced compared to silicon fast recovery diodes (FRD), SiC SBDs are increasing being used in high frequency circuits in a range of fields, from household appliances to industrial equipment(Figure 3). ROHM also offers an AEC-Q101-compliant lineup that has been widely adopted in in-vehicle charging circuits for electric and plug-in hybrid vehicles both in Japan and overseas.

   Figure 3. Characteristics Comparison: SiC Schottky Barrier Diodes vs. FRD (650V/10A Class)

2. SiC MOSFETs

It widely known that, compared to Schottky barrier diodes, SiC MOSFETs suffer characteristics degradation (MOSFET on-resistance, increased forward voltage of the body diode) due to body diode current flow, which often causes reliability problems during mass production.

In response, ROHM was able to improve processes related to crystal defects and device structure and in December 2010 became the world’s first to successfully mass produce SiC MOSFETs. 2nd generation 650V and 1200V products are currently under development.

Compared to conventional silicon IGBTs that utilize a high-voltage switching element, switching loss is reduced by over 5 times, contributing to device miniaturization by increasing drive frequency (i.e. through smaller filters and cooling mechanisms) and improving power conversion efficiency. (Figure 4)       

                            Figure 4. Switching Loss Comparison: Si IGBT vs. SiC MOSFET

3. SiC Power Modules

ROHM was the first to develop a ‘full SiC’ power module with internal power elements comprised solely of SiC power devices, which it began mass producing in 2012. At present, two types of 1200V/120–180A rated power modules are being manufactured using an in-house production system, with 1200V/300A rated power modules scheduled for 2014 and further expansion of rated currents and voltages in the future (Figure 5). These SiC power modules, along with discrete SiC MOSFETs, are already beginning to see adoption globally, primarily in industrial applications such as commercial solar power conditioners and high frequency power supplies.

Figure 5. SiC Power Modules

4. Future Products

ROHM is planning a lineup of 1700V breakdown voltage SiC Schottky barrier diodes and SiC MOSFETs, and is currently developing 3rd generation SiC MOSFETs utilizing a trench gate structure that significantly reduces on-resistance per chip area. This technology is expected to accelerate the adoption of SiC by lowering on-resistance and decreasing chip costs.

Silicon IGBT Power Devices Utilizing ROHM’s Collective Strength

SiC power devices that provide small switching loss are particularly effective in fields that require both high breakdown voltage and high frequency operation. However, there are still a number of areas in which silicon power devices are utilized due to their superior price point. As a result, ROHM is continuing to develop unique products in the conventional silicon power device sector, such as a ‘Hybrid MOS’ that features the best characteristics of both MOSFETs and IGBTs.

For silicon IGBTs, ROHM offers a wide range of hybrid products that leverage the company’s expertise as a manufacturer of both individual discrete semiconductors and integrated semiconductor components. Below is an introduction of ROHM’s silicon IGBT power device product lineup.

1. Individual IGBTs

ROHM has commercialized two types of 650V breakdown voltage IGBT devices. One, the RGTH series, provides low saturated voltage characteristics (1.6V typ. at rated current) and is designed in such a way that puts a priority on high-speed switching performance demanded for converter circuits. This makes them ideal for power factor correction (PFC) circuits in switching power supplies, boost circuits for solar power generator power conditioners, and the like. The other type – the RGT series – delivers low saturated voltage characteristics along with short-circuit handling capability (5μs), which is particularly required for inverter circuits in air conditioners, large household appliances such as washing machines, solar power conditioners, and welders. Both series include an ultra-high-speed soft recovery FRD.ROHM plans to gradually expand its product lineup with a 1200V breakdown voltage series as well as products that comply with AEC-Q101 for automotive use.

2. IGBT IPM

An IPM (Intelligent Power Module) that integrates an individual IGBT with superior low saturated voltage characteristics, ultra-high-speed soft recovery FRD, gate drive IC, and bootstrap diode in an inverter configuration has also been added to the product lineup. (Figure 6)  

                Figure 6. ROHM IGBT-IPM

Key features are as follows.

・The gate drive IC adopts a 600V SOI process that prevents problems caused by latch up

・Inrush current is suppressed while stability of the floating power supply on the ARM side achieved using a proprietary current limiting system for the current limiting resistance of the bootstrap circuit

・Multiple protection functions are implemented, such as UVLO, short circuit protection, and temperature detection, increasing reliability

・Available in a class-leading isolated low thermal resistance ceramic package.

Mass production is scheduled to begin in 2014 for two series optimized for large household appliances and smaller industrial motor drive applications: a ‘low-speed switching drive series’ featuring reduced saturated voltage VCEsat ideal for drive operations at low carrier frequencies (4–6kHz), and a ‘high-speed switching drive series’ that reduces switching loss, enabling compatibility with high carrier frequency drive (15–20kHz). (Figure 7)

Figure 7. Series development based on carrier frequency

3. Igniter IGBT

For products designed for automotive use, ROHM has developed a gasoline engine igniter IGBT, which is slated for start mass production in late 2014 (Figure 8).

  Figure 8. Igniter IGBT Development Roadmap

Low saturated voltage characteristics have been achieved in addition to the required rated avalanche energy (250mJ @25°C). The product is available in the D-PAK package, and conforms to the AEC-Q101 standard for automotive reliability.

In the future, after releasing products with a Collector-Emitter protection voltage of 430V±30V, ROHM will develop models that combine Collector-Emitter protection voltage with avalanche resistance and implement product development with an eye toward commercialization of an igniter IGBT IPM that integrates a driver IC into a single package.

In Conclusion

In addition to SiC semiconductors, which have garnered increased attention, ROHM will continue to offer a complete lineup of power devices for the silicon semiconductor field, and going forward will leverage its collective strength as a market-leading supplier of a broad array of semiconductor products and solutions – from discretes to ICs – to meet a variety of market needs. Please visit ROHM’s website for additional information and to access technical data on individual products.