ROHM Releases 4th Generation Fast Recovery Diodes Delivering Low Loss Performance and Low Noise Characteristics

By Chad Cox

Production Editor

Embedded Computing Design

July 13, 2022


ROHM Releases 4th Generation Fast Recovery Diodes Delivering Low Loss Performance and Low Noise Characteristics
Image Provided by ROHM Semiconductor

ROHM Semiconductor announced the RFL/RFS Series, its fourth generation 650V fast recovery diodes (FRDs) with low forward voltage (VF) and fast reverse recovery time (trr), as well as ultra-low noise characteristics. The new devices are ideal for high-power industrial and consumer equipment, such as air conditioners and EV charging stations.

To keep up with the rise in global power consumption, more efficient use of electricity has become necessary in recent years. This is especially true for white goods and industrial equipment that uses a lot of power, like EV charging stations. These necessitate not only high electrical efficiency, but also reduced workload in circuit design for noise countermeasures. In response, ROHM created diodes with low VF for more efficient operation and fast trr characteristics for less loss and ultra-low noise when switching OFF.

The RFL/RFS Series achieves the best balance of VF and trr by optimizing the device structure and materials, which are important characteristics for FRDs but have a trade-off relationship. The low VF RFL series reduces VF by about 3.2 percent and trr by about 8.3 percent when compared to the conventional RFN series, while the high-speed RFS series reduces VF by about 17.9 percent when compared to the conventional RFUH series. Through optimal design based on circuit requirements, both products contribute to higher power supply efficiency. Furthermore, ultra-low noise diode recovery characteristics are achieved, which aid in the reduction of both workload and noise components.


  • PFC (Power Factor Correction) circuits in air conditioners, washers, refrigerators, etc.
  • Secondary rectifier circuits in EV charging stations and the like
  • Inverter circuits in machine tool robots, compressors, etc.
  • Power supplies for servers, base stations, and more

When designing power supply circuits, a circuit configuration (topology) that meets the required specifications for input/output voltages, power, isolation, and other factors must be chosen. ROHM provides a product selection page that recommends the best products for various topologies.

Terminology: VF / trr Characteristics

  • VF (forward voltage) is the voltage between the diode terminals generated from current flow in the forward direction. The lower this value, the more efficient application operation.
  • trr (Reverse Recovery Time) is the time it takes to switch from the ON state to completely OFF. The lower this value is, the smaller the loss during switching.
  • VF and trr are key characteristics related to diode loss and are in a trade-off relationship.

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Chad Cox. Production Editor, Embedded Computing Design, has responsibilities that include handling the news cycle, newsletters, social media, and advertising. Chad graduated from the University of Cincinnati with a B.A. in Cultural and Analytical Literature.

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