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Circuit tech offers resettable over-current protection

Posted: 19 Nov 2010     Print Version  Bookmark and Share

Keywords:Li-ion  hybrid circuit protection  MHP 

useful for high-rate-discharge battery applications at ratings above 30VDC/30A.

Tyco Electronics introduced its Metal Hybrid PPTC (MHP) technology which utilises a new hybrid circuit protection design which merges a bimetal protector in parallel with a polymeric positive temperature coefficient (PPTC) device, offering resettable over-current protection. It utilises the low resistance of the PPTC device to help prevent arcing in the bimetal protector at higher currents, at the same time heating the bimetal, keeping it open and in a latched position.

It is useful for high-rate-discharge battery applications at ratings above 30VDC/30A. With the advances in lithium ion (Li-ion) technology, a rapidly growing market for high-rate-discharge Li-ion battery applications has created the need for cost-effective, robust circuit protection devices that help ensure battery safety in end-products. Currently, however, few protection solutions address high-rate-discharge battery applications and traditional circuit protection techniques tend to be large, complex and/or expensive. In response, MHP technology offers a cost-effective, space-saving option which conventional circuit protection approaches are unable to deliver.

The initial device in a planned family of MHP devices, the MHP30-36, has a 36VDC/100A maximum rating and a time-to-trip of under five seconds at 100A (at 25°C). The device's hold current is 30A and the initial resistance is under 2mΩ. This brings excellent arc suppression characteristics compared with standard breaker devices which must limit the number of switching cycles (since arcing between contacts may damage them).

The MHP30-36 device can also help reduce the number of discharge FETs and accompanying heat sinks in applications that usually use IC-plus-FET battery protection designs.

The MHP device technology may be configured for various applications; higher voltage (up to 400VDC) and hold current (60A) devices are now in development. Future design considerations consists of battery protection in Li-ion battery packs used in e-scooters and light electric vehicles (LEVs), as well as standby-power applications and non-battery applications such as electric motor protection.

Samples are now available for Model MHP30-36-T (30A, 36VDC).

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