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Power/Alternative Energy??

Phototriacs isolate logic from power mains

Posted: 29 Mar 2006 ?? ?Print Version ?Bookmark and Share

Keywords:VO4154? VO4156? phototriac? Vishay?

Vishay Intertechnology Inc. introduced 12 new phototriac devices offering a static dV/dt of 5kV/s. These new phototriacs give customers a selection of 58 base phototriac part numbers (excluding electrical and lead form options).

The new phototriacs will be used to isolate low-voltage logic from high-voltage power mains in industrial systems running off 120-, 240- and 380V AC lines. Typical applications include control of resistive, inductive and capacitive loads, including AC motor drives, TRIAC drives, switching power supplies, programmable controllers, high-current thyristors, relays, temperature controls and solenoid/valve controls.

The devices include zero-crossing (ZC) and non-zero-crossing (NZC) phototriacs, all with an isolation test voltage of 5,300VRMS and on-state current of 300mA. Specific device options allow designers to choose from trigger currents of 1.6-, 2- or 3mA, which aim to simplify the interface to standard logic circuits, and block voltages of 400V or 600V. A proprietary dV/dt clamp results in a static dV/dt of greater than 5kV/s.

The new ZC VO4154 and VO4156 series phototriacs consist of a GaAs infrared LED that is optically coupled to a photosensitive ZC TRIAC detector chip. This design is said to reduce EMI noise harmonics while featuring lower peak operating currents, making it suitable for noise-sensitive circuits. Devices in the VO4254 and VO4256 series of NZC phototriacs, on the other hand, have the advantage of being able to trigger any time during the AC phase cycle and turn off at the next zero crossing. This, according to Vishay, makes NZC devices suitable for many phase modulation applications.

The new phototriacs feature reinforced insulation per IEC60950 2.10.5.1. Encased in the 6-pin DIP, samples of the new VO4154/6 and VO4254/6 phototriacs are available now. Production quantities have a lead-time of six to eight weeks.




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