Appliance Design - March 2008 - (Page 24)

POWER ing voltage rating, over-voltage transients may occur that exceed these limits. By integrating PPTC technology with the MOV, the 2Pro device improves over-current and thermal protection under conditions where the MOV is exposed to prolonged continuous over-voltage events. In the event of an over-voltage transient, such as a loss of neutral event shown in Fig. 3, the PPTC element of the 2Pro device heats up, trips and goes into a high-resistance state, helping to reduce the risk of MOV device failure. The LVM2P-015R10431 devices used in the test scenarios described here are 10 mm radial-leaded devices that utilize three leads. In the electrical schematic, shown in Fig. 5, the first lead is connected to the PPTC element, the second lead is connected to the MOV/PPTC series connection (providing a path to ground), and the third lead is connected to the MOV. The single, small form-factor, circuitprotection device helps reduce component count and footprint size, and provides a safe failure mode in case of varistor overstress. It also helps equipment comply with IEC 60950/IEC 60335 and IEC 61000-4-5 testing requirements. Fig. 4. Typical circuit diagram utilizing the 2Pro circuit protection device. Fig. 5. 2Pro in ungrounded system. Coordinated protection The thermally enhanced MOV is suitable for over-current and over-voltage protection in a wide range of telephony and VoIP equipment applications. These include cordless phones, VoIP gateways, data modems, set-top boxes, security systems, MDF (Main Distribution Frame) modules, analog linecards and ISDN (Integrated Services Digital Network) linecards. The widespread adaptation of VoIP gateways in homes and enterprise environments has resulted in increasingly stringent safety requirements for Customer Premise Equipment. The 2Pro device helps equipment manufacturers comply with UL 60950 and remain operational after specified lightning tests. It also helps equipment comply with surge tests per TIA-968-A, IEC 60950, and ITU-T K.20/K.21. The UL 497A listed protector also helps provide ESD protection. Fig. 5 and Fig. 6 illustrate how the device is used in both an ungrounded and grounded circuit protection scheme. Fig. 6. 2Pro in grounded system. Summary Coordinated circuit protection helps reduce board space requirements and component count, and improves equipment reliability. The resettable functionality of the thermally protected MOV can also help manufacturers reduce warranty returns and customer complaints related to transient over-current and over-voltage incidents. < For more information, enter.. . . . . . . . . . . . . . . . . . . 300 Or email: applianceprotection@tycoelectronics.com * Raychem, 2Pro, TE Logo and Tyco Electronics are trademarks. 24 applianceDESIGN March 2008 www.applianceDESIGN.com http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - March 2008

Appliance Design - March 2008 Contents Editorial Shipments/Forecasts News Watch A New Appliance is Set to Break into Homes Soon - the Micro CHP Unit, which Generate both Heat and Power. Thermally Enhanced Varistors Help Protect Low-Power Systems Against Damage Caused by Over-Current, Over-Temperature and Over-Voltage Faults. Hybrid Controller Reduces Standby Power Consumption and Improves Active-Mode Efficiency. Battery-Management ICs Solve Design Challenges for Cordless Appliances Using High-Voltage, Lithium-Ion Battery Technology. A Semiconductor Solution Protects the Relay in a Temperature Controller for a Cooking Appliance. New Polyurethane Foam Insulation System Optimizes both Insulation Performance and Productivity. Innovations in Decorative, Pre-Finished Metals Expand Range of Design Options for Appliance Designers. Design Marts Association Report: AHAM Advertiser's Index

Appliance Design - March 2008

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