Overcoming Circuit Protection Challenges in Lithium Battery Cell Operated Electronics

Komatsulite™ Mini-Breakers Application Note

12/15 • e/C1564

LC Series

HC Series

KCA Series

NR-C Series

NR-A Series

In the consumer market, specific applications present additional circuit protection issues

such as laptop personal computers, tablets, smartphones, and portable appliances such as

vacuum cleaners. Electric bicycles, also called e-bikes, and controllers for automotive seats

are additional examples of applications that may need an additional level of circuit protection

to handle the overcurrent and overtemperature requirements of lithium battery cells. For

instance, a Thermal Cut Off device or bi-metal switch on its own may not be able to effectively

protect the batteries in these types of applications. A false trip could render a one-time fusing

device inoperable, so a device with a reset mechanism is preferred. In such applications, a

mini-breaker solution is a good option.

Mini-breakers incorporate existing technology in such a way to enhance their protection

capabilities. Mini-breakers put a bi-metal switch and PTC in parallel to deliver the best

features of both. Since a PTC latches and does not have a mechanical contact, it offsets the

bi-metal switch’s lack of latching providing a significant design advantage. Similarly, the bi-

metal switch enhances the mini-breaker solution by providing a higher operating current. The

temperature sensing capability and low resistance of the bi-metal switch are additional benefits

gained by incorporating the mini-breaker into the hybrid device. With several temperatures

available and 100 % in-line inspection of trip temperature, reset temperature, and impedance

before shipping, Komatsulite™ mini-breakers offer reliable battery cell protection for multiple

instances of overcurrent and overtemperature threats. Taking a look inside, Figure 1 illustrates

that the mini-breaker is composed of a base terminal, PTC, bi-metal disc, base, arm terminal,

arm, cover plate, contact, and cover.

MINI-BREAKER TECHNOLOGY OVERVIEW

Figure 1. Construction of the Komatsulite™ Mini-Breaker

ARM

TERMINAL

COVER

PLATE

CONTACT

COVER

ARM

BASE

TERMINAL

BASE

AVAILABLE WITH AND WITHOUT PROJECTIONS.

PROJECTION

BIMETAL DISC

PTC

PROJECTION