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ROHM’s New 4th Generation Fast Recovery Diodes Deliver Low Loss Performance and Ultra-Low Noise Characteristics

RFL/RFS Series improves power supply efficiency and reduces noise in air conditioners and EV charging stations
Santa Clara, CA and Kyoto, Japan, July 12, 2022 (GLOBE NEWSWIRE) — ROHM Semiconductor today announced its fourth generation 650V fast recovery diodes (FRDs), the RFL/RFS Series, featuring low forward voltage (VF) and fast reverse recovery time (trr), respectively, as well as ultra-low noise characteristics. The new devices are ideal for industrial and consumer equipment that handle large amounts of power, such as air conditioners and EV charging stations.

In recent years, more effective use of electricity is necessary to cope with the rise in global power consumption. This is especially true for white goods and industrial equipment that handle large amounts of power, such as EV charging stations. These require not only high electrical efficiency, but also reducing workload for noise countermeasures in circuit design. In response, ROHM developed diodes that combine low VF for more efficient operation with fast trr characteristics that provide less loss and ultra-low noise during switching OFF.

Optimizing the device structure and materials allows the RFL/RFS Series to achieve the optimum balance of VF and trr, which are important characteristics for FRDs, but are in a trade-off relationship. The low VF RFL series reduces VF by approximately 3.2% and trr by about 8.3% over the conventional RFN series, while the high-speed RFS series decreases VF by approximately 17.9% versus the conventional RFUH series. Both products contribute to higher power supply efficiency through optimal design based on circuit requirements. Furthermore, ultra-low noise diode recovery characteristics are achieved – they help to reduce both workload and components for noise.

Going forward, ROHM will continue to expand the package lineup of the RFL/RFS series to provide automotive support while expanding applicability by reducing power consumption.


  • 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

Topology Selection

When designing power supply circuits, it is necessary to select a circuit configuration (topology) that matches the required specifications for input/output voltages, power, isolation, and other factors. ROHM offers a selection page that recommends the optimum products for various topologies.

Pricing: $5.14/unit (samples, excluding tax)

Availability: Now (in mass production)
Available for purchase through online distributors Digi-KeyMouser, and Farnell.

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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