Technical Information Site of Power Supply Design

Product Key Points

Silicon Diodes Continue to Evolve, Driven by Applications | Si Fast-Recovery Diodes

Diodes for Low-Power and for High-Power Applications

  • Fast-recovery diode
  • FRD
  • Reverse-recovery time
  • trr
  • Ultra-low VF
  • Fast trr
  • Power factor correction
  • PFC
  • BCM
  • CCM

ROHM manufactures various silicon-base diodes. Among these, we here introduce diodes with characteristics and specifications suited to power applications. Many of the diodes used in power applications are employed for rectification. For example, in power supply circuits, Schottky barrier diodes and fast-recovery diodes are used for output rectification. The kind of diode to use is determined based on such parameters as the rated voltage and current, VF, IR, trr, and the like, but in recent years, Silicon-based power diodes have undergone improvements making them suited to numerous applications. Silicon-based diodes have been developed with previous drawbacks alleviated, thus reducing the need for trade-offs.

Fast-recovery diodes (FRDs) are silicon diodes with an improved reverse-recovery time trr. The trr of ordinary diodes ranges from several tens of microseconds to 100 μsec or so, but FRDs are extremely fast, with a trr of 100 nsec or less. However, they have the drawback of a forward voltage VF of 1 V to 2 V or so, which is higher than not only SBDs, but also than ordinary diodes. The fast trr means that switching losses are reduced, but the high VF results in larger conduction losses, and particularly when used in low-voltage rectification, the device parameters must be studied carefully.

ROHM's FRD lineup includes series that achieve ultra-low VF values, which is important for low-power applications at 200 W to 300 W or below, and for operation in PFC BCM (power factor correction, boundary conduction mode), as well as series with fast trr values that are suited to high-power applications at 200 W to 300 W or above and to PFC CCM (power factor correction, continuous conduction mode) operation. The following graphic maps ROHM FRD series, with trr along the vertical axis and VF along the horizontal axis, identifying different application requirements.


Details info on the devices of the above series can be accessed from the following links.

Si Fast-Recovery Diodes for Power Applications
Ultra-low VF RFNL series
Standard RFN series
Fast trr RFUH series
RFV series

A list of the entire lineup of ROHM FRDs can be found here.

Power Supply Design Technical Materials Free Download

Power Supply Design Technical Materials Free Download

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