Tyco Electronics, a global leader in circuit protection
solutions, has introduced a metal hybrid PPTC (MHP) technology, useful for
high-rate-discharge battery applications at ratings above 30 VDC/30 A. MHP
technology uses a new hybrid circuit protection approach that combines a
bimetal protector in parallel with a polymeric positive temperature coefficient
(PPTC) device. This integrated solution provides resettable overcurrent
protection and utilizes the low resistance of the PPTC device to help prevent
arcing in the bimetal protector at higher currents, while also heating the
bimetal to keep it open and in a latched position.
Due to advances in lithium ion (Li-ion) technology, smaller,
lighter weight, and higher power Li-ion batteries can now replace nickel
cadmium or lead acid batteries previously used in high-rate-discharge battery
applications. This trend has resulted in a rapidly expanding market for
high-rate-discharge Li-ion battery applications, which, in turn, has created
the need for cost-effective, robust circuit protection devices that help ensure
battery safety in end-products.
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 provides a cost-effective, space-saving device that conventional
circuit protection approaches are unable to deliver.
The initial product in a planned family of MHP devices, the
MHP30-36 device has a 36 VDC/100 A maximum rating and a time-to-trip of under
five seconds at 100 A (at 25°C). The device’s hold current is 30 A and the
initial resistance is under 2.0 mOhms.
The MHP30-36 device offers excellent arc suppression
characteristics compared to standard breaker devices that 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 typically use IC-plus-FET battery protection
designs.