Schottky rectifiers move up to 250V

A new range of 200-250V Schottky diodes is claimed to outperform traditional ultrafast rectifiers - eliminating noise at all temperatures.

ON Semiconductor has pushed the Schottky voltage barrier above 200V with the introduction of the first 250V silicon Schottky device for plasma/LCD television, power supply, consumer and automotive applications.

Further expanding its high voltage Schottky portfolio, the company has also introduced two new 200V Schottky rectifiers in SMC packages.

The quiet operation and fast recovery time of ON Semiconductor's new 200 and 250V Schottky devices outperform ultrafast rectifiers reverse recovery time, forward voltage and softness.

As such, the new high-voltage Schottky devices simplify system design and offer a more cost-effective solution for the growing number of 200-250 V applications - including plasma television drive circuits, automotive body electronics and computer power supplies.

"Since first extending the Schottky voltage boundary to 200V in the early 1990s, ON Semiconductor has remained the high voltage silicon Schottky leader", said Keith Nootbaar, ON Semiconductor Director of Power Discrete Products.

"While our competitors are only now beginning to reach 200V, ON Semiconductor has set a new industry milestone of 250V and has plans to continue upward development of the technology in the future".

Traditionally, ultrafast rectifiers have been used for energy recovery, flyback surge and output rectification in applications where the reverse voltage can exceed 200V.

An example of a key application is energy recovery circuits for plasma TV panels.

In this application, switching frequencies are on the order of 250kHz and voltages run greater than 180V peak-to-peak.

This necessitates a low-forward-drop rectifier with the best possible switching.

The energy recovery rectifiers should have a minimum breakdown voltage on the order of 250V (allowing for derating and spikes).

Ultrafast rectifiers have traditionally been used in this application, but with advanced silicon Schottky technology ON Semiconductor has developed a better solution.

"The 250V breakdown was previously beyond the performance range of commercially available silicon Schottky rectifiers", said Nootbaar.

"A designer was left with a choice between standard ultrafast, soft-recovery ultrafast or expensive alternatives such as silicon carbide".

"Using advanced silicon Schottky technology, ON Semiconductor has achieved lower forward voltage (less than 1.0V) and addressed both the switching loss and electromagnetic interference (EMI) issues that are also significant at these (200-250kHz) frequencies".

The new devices introduced by ON Semiconductor to expand its existing 200V and above rectifier portfolio are: the MBR40250, a 40A, 250V Schottky offered in a T0-220 package and die; the MBRS4201, a 4A, 200V Schottky offered in an SMC package; and the MBRS3201, a 3A, 200V Schottky offered in an SMC package.

These new high-voltage Schottky devices eliminate reverse recovery oscillations present in ultrafast rectifiers at all temperatures.

Because oscillations (noise) are the main cause for EMI, the new 250V Schottky technology eliminates the need for EMI filtering - and with it the costs of EMI filtering.

In comparison, ultrafast rectifiers used in high-temperature applications show increased reverse recovery oscillations.

This increases EMI and adds filtering costs to the overall system design.

The softness factor (tb/ta) of these 200 and 250V Schottky devices also significantly outperforms ultrafast rectifiers.

The superior reverse recovery time and high stability of the Schottky at hot temperatures compared with a similar voltage ultrafast rectifier reduces switching losses in rectifier applications, improving the overall efficiency of the circuit.

The new devices are priced between $0.30 and $1.00 per unit in 10,000-unit quantities.

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