Introduction and application of PPTC fuse protection components
Excessive heat or improper application can compromise the performance of LED light sources. The PPTC fuse component is made of a polymer
PosiTIve Temperature Coefficients doped conductor, and is used in series in a circuit. When a fault occurs, the PPTC becomes hot and the resistance increases, thereby protecting the device from being damaged; After the exclusion, the PPTC fuse is reset and returns to the low resistance state. Tyco Electronics Application Engineer Guo Tao said that because PPTC fuse components can be reset after fault clearing and circuit power is disconnected, warranty, service and repair costs can be reduced.
LED devices are susceptible to overvoltage, overcurrent and overheating, greatly reducing the LED's luminescence performance and lifetime. LED performance and lifetime are closely related to the LED's pn junction operating temperature. When the junction temperature in the LED chip rises by 10 ° C, the luminous flux is attenuated by 1% and the LED lifetime is reduced by 50%. Therefore, effective control of the junction temperature of the LED is the fundamental requirement for protecting the LED. In addition to good heat dissipation design, safe and reliable overheat protection must also be considered.
A major feature of PPTC fuse is that the thermal protection curve is very rich. Guo Tao said that with the increase of current, the same LED lamp is under different working currents.
The temperature points to be protected may be different. If only one point is protected, the overall performance will be impaired, so the same PPTC has different thermal shutdown protection points at different currents. While the damage current at different temperatures has its temperature breakpoint, PPTC helps LED lighting achieve a good balance between brightness and lifetime.
Whether it is automotive-grade lighting, LED street lighting, LED backlighting, or other electrical LED lights, you can protect the low-cost PPTC fuse series by plugging it into the circuit. For example, if most of the input LED's electrical energy is converted to heat and is not used for illumination, the LED can be over-current protected by a Polyswitch component in series, and it can be thermally bonded to a metal core printed board or LED heat sink to provide over-temperature. protection. For power input protection, driver input protection, driver circuit output protection, and electrostatic discharge protection, Tyco Electronics' PPTC series components provide solutions. Even in lighting systems that use Class 2 light sources to reduce lighting system costs and increase flexibility, a combination of circuit protection components can achieve safety standards.