Increased energy saving in industrial applications

27th November 2015
Joe Bush

ROHM’s recently announced AC/DC converter control IC, designed specifically for SiC MOSFETs in industrial equipment such as servers and other large power applications, was showcased at SPS IPC Drives. The BD7682FJ-LB allows the easy implementation of SiC-MOSFETs to an AC/DC converter which has proved challenging when using discrete configurations due to the large number of components required. 

In contrast, ROHM’s latest product provides an integrated solution and creates new standards for energy savings and miniaturisation while supporting the adoption of SiC power semiconductors that provide breakthrough levels of efficiency and performance.

Compared to silicon MOSFETs used in conventional AC/DC converters, SiC MOSFETs enable AC/DC converters with improved power efficiency by up to six percent. Furthermore, components used for heat dissipation are not required (50W Class power supplies), leading to greater compactness. The specification of BD7682FJ-LB also includes multiple protection functions that enable support for high voltages up to 690V AC, making them well suited for general industrial equipment while improving reliability.

In recent years there has been an increasing trend to conserve energy in all areas. This includes high voltage industrial equipment applications. To achieve these targets it’s necessary to adopt advanced power semiconductors and power supply ICs. Among these, SiC power semiconductors are expected to gain ground over silicon solutions due to their higher voltage capability, greater energy savings and a more compact form factor. However, until now there has not been a control IC that can sufficiently draw out the performance of SiC MOSFETs, particularly in AC/DC converter systems. As a result designers are faced with numerous problems related to power consumption and stability in a variety of high power applications.

To meet these needs, ROHM utilises analogy technology with SiC power semiconductor expertise to develop the a AC/DC converter controller specialised for driving SiC MOSFETs.

Key features

1. Maximises SiC MOSFET performance for breakthrough energy savings The BD7682FJ-LB integrates a gate drive circuit optimised for SiC MOSFET drive by combining analogue design technology with SiC power semiconductor development expertise. In addition, a quasi-resonant system delivers lower noise and higher efficiency vs conventional PWM methods, making it possible to maximise the performance of SiC MOSFETs used in AC/DC converters, resulting in significant power savings.

2. SiC MOSFET contributes to unmatched miniaturisation Unlike conventional Si MOSFETs, adopting SiC MOSFETs in AC/DC converters eliminates the need for components used for heat dissipation, contributing to smaller, lighter AC/DC converter designs. Support for higher switching frequencies (i.e. 120kHz) is also ensured, expanding applicability while improving efficiency.

3.Multiple protection circuits support high voltage operation up to 690V AC Various protection circuits enable high voltage operation in AC/DC converters up to 690V AC – which is well suited for general 400VAC industrial applications. In addition to overvoltage protection for the supply voltage pin and brown in/out (undervoltage) countermeasure for the input voltage pin, overcurrent and secondary overvoltage protection functions are included, enabling continuous operation in industrial equipment while improving reliability.

SiC MOSFET Advantages

SiC MOSFETs provide several advantages over Si MOSFETs in the high voltage region, including lower switching and conduction losses, high power compatibility, and increased resistance to temperature changes. Leveraging these benefits makes it possible to improve power conversion efficiency, miniaturise components for heat dissipation, increase operating frequency to support smaller coils and more, resulting in increased power savings, lower component count, and smaller mounting area.

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