Faster thyristor gives more options to high power designers

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By Nick Flaherty

The N1955MC16 developed by the UK subsidiary of IXYS has a turn-off time of 20 μs and a current rating of 1,955 A. The symmetrical blocking with forward and reverse voltage equal to 1,600 volts makes it suitable for both voltage and current fed applications such as induction heating and resonsant power supplies. The increase in current rating can be traded in adapting the turn-off characteristic to give faster turn-off even than the standard offering of 20 μs or tailoring the reverse recovery for series operation.

The device offers higher current, while retaining the same turn-off time, when comparted to other parts in the same footprint package size. The improved design has an average current rating of 1,955 amperes at a heat sink temperature of 55 ºC, a 35% increase over older IXYS designs. The improvement in performance is achieved by maximising the die size and improved distributed gate geometry. The 56 mm silicon dice are bonded to metal discs and encapsulated in fully hermetic 50 mm electrode contact diameter ceramic packages, with an industry standard overall diameter of 74 mm.

“Providing the correct thermal conditions are observed, with a repetitive di/dt rating of 1,000 A/s, the device can be used in applications with repetitive frequencies up to 25 kHz,” said Frank Wakeman, IXYS UK’s Marketing and Technical Support Manager.

The larger die sizes and higher current ratings offer more flexibility in customising the parts to meet the needs of customer specific applications such as induction power supplies for melting, billet heating and surface treatments as well as resonant power supplies and pulse switches for applications including high power magnets and lasers.

The full symmetrical blocking device is available in three different switching classes at two standard voltage grades. The 1,600 V parts are the N1955MC16D with a tq of 20 μs, the N1955MC16E with a tq of 25 μs and the N1955MC16F with a tq of 30 μs. The 1,400 volt parts are the N1955MC14D with a tq of 20 μs, the N1955MC14E with a tq of 25 μs and the N1955MC14F with a tq of 30 μs.

For data sheets please go to the IXYS UK website at


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