1. Protection of LED circuits using fuses (tube)
Because the fuse is disposable, and the reaction speed is slow, the effect is poor, the use of trouble, so the fuse is not suitable for use in the finished LED light, because the LED light is now mainly in the city of luster engineering and lighting engineering. It requires LED protection circuit to be very harsh: in the normal use of current can immediately start the protection, so that the LED power supply circuit is disconnected, so that the LED and power can be protected in the normal light and then automatically restore power supply, Does not affect the LED work. The circuit can not be too complicated, the volume can not be too big, the cost is even lower. Therefore, the use of fuses to achieve very difficult.
2. Using transient voltage suppression diodes (referred to as TVS)
Transient voltage suppressor diode is a diode form of high-performance protection device. When its poles are subjected to the reverse transient high-energy impact, the high resistance between the two poles can be immediately reduced to low resistance at a very short negative time of 10 seconds 12, absorbing the surge power of up to several kilowatts , The voltage clamp between the two poles in a predetermined voltage value, the effective protection of electronic components in the circuit. Transient voltage suppressor diodes have the advantages of fast response time, large transient power, low leakage current, good breakdown voltage deviation consistency, easy control of clamp voltage, no damage limit and small size.
However, in actual use, it is not easy to find a TVS device that meets the required voltage value. LED light bead damage is mainly due to over current caused by overheating the chip internal. TVS can only detect over-voltage can not detect over-current. To choose the right voltage protection point is difficult to grasp, this device can not be produced is difficult to use in practice.
3. Select self-recovery fuse
Self-recovery fuse, also known as polymer positive temperature PTC thermistor, is composed of polymer and conductive particles. After special processing, the conductive particles form a chain-like conductive path in the polymer. When the normal operating current through (or components in the normal ambient temperature), PTC self-recovery fuse was low resistance state; when abnormal overcurrent in the circuit through (or ambient temperature), the high current (or ambient temperature) The heat generated by the rapid expansion of the polymer, also cut off the conductive particles formed by the conductive path, PTC self-recovery fuse was high impedance state; when the circuit over-current (over-temperature state) disappears, the polymer cooling LED drive power www.leadwayled.com, the volume returned to normal, in which the conductive particles and re-constitute the conductive path, PTC self-restoring fuse also showed the initial low resistance state. In normal working condition, the heat of self-recovery fuse is very small. In the abnormal working condition, its heat resistance is very high, which limits the current passing through it and thus plays a protective role. In the specific circuit, you can choose:
① shunt protection. General LED lights are divided into many tandem branches. We can add a PTC element in front of each branch separately for protection. The benefits of this approach are high accuracy and good reliability of protection.
② overall protection. Add a PTC element on the front of all the beads to protect the whole lamp. The benefits of this approach is simple, does not account for the volume. For the civilian product, the result of this protection in actual use is still satisfactory.