FUZETEC PPTC TECHNOLOGY

PPTC device and Resettable Fuse ( PTC THERMISTOR, PTC VARIABLE RESISTER, Variable Resistance PTC Thermistor, Variable Resistor, Current Limiter ) technology synergistically integrate the advance polymer material technologies, conductive material science, novel processing engineering, and fundamental electronic and electrical theory. Electrical resistance of such material and devices increases with temperature increases and vice versa. Fuzetec has successfully integrated all theses and developed a wide range of PPTC devices specifically designed to protect circuits from overcurrent.

HOW DOES PPTC RESETTABLE FUSES WORK

FUZETEC™ resettable fuses are designed and made of patented novel PPTC material in thin chip form where conductive particles are dispersed in a polymer that has a crystalline structure. At normal operating conditions there are numerous chains forming conductive paths throughout the PPTC material. Under fault conditions (Tripped State), excessive current flows through the PPTC device and the PPTC material heats up. This makes the polymer matrix’s morphology change from crystalline to amorphous. Under these conditions the conductive particles move apart from each other, most of them no longer conduct current and the resistance of the device increases sharply. Upon fault current being removed, the resettable fuse is resetted and allows the current through the circuit again.

Fig 1	Fig 2

When connected in series to a circuit, Fuzetec’s PPTC resettable fuses remain at extremely low resistance and allow the electrical current to flow through it without any restriction. When overcurrent situations occur, Fuzetec PPTC resettable fuses limit the current to a very small value (nearly to “open state”) and therefore protect the circuit from being damage by the high current.

TRIP CURRENT, HOLD CURRENT AND THERMAL DERATING

Trip Current (IT) and Hold Current (IH) of resettable fuse are rated at 23°C. Typically its Trip Current is twice as much as its Hold Current. FUZETEC™ device will not trip at its Hold Current or blow and will trip at or above its Trip Current. However, due to the

PTC effect both IT and IH reduces with ambient temperature increase and vice versa. As shown on Figure 2, the currents are reduced nearly 50% at 85°C and increased to 150% at -40°C.