LED technology is the mainstream of today's market, but the LED technically there are still many problems to overcome, and the life of the LED and energy saving, the price has been enthusiastic discussion of the topic. LED circuit protection circuit is very important in this process, do not speak, first to explore the experience of three kinds of led 10w circuit protection method:
(1) protect the led power 50w circuit fuse (tube)
Since the fuse is a one-time, and the reaction is slow and poor results, the use of trouble, so the fuse is not suitable for the finished LED lights, LED light is now primarily in the glory of the city engineering and lighting engineering. It requires very harsh: can start immediately to protect beyond the normal use of current LED protection circuit, LED power supply path is disconnected, the LED and power supply can be protected, normal throughout the light and then be able to automatically recover for electricity, does not affect the led power 10w. The circuit can not be too complicated and can not be too much volume, the cost is even lower. So the fuse is very difficult to implement.
(2) the use of transient voltage suppression diode (referred to as TVS)
Transient voltage suppression diode is a two-pole form of high-performance protection devices. When its poles by the reverse transient high-energy impact, the negative 12 power of 10 seconds of a very short time speed, so that between the poles of the high impedance immediately reduced to the low resistance to absorb up to several kilowatts power surge between the poles of the voltage clamp at a predetermined voltage value, the effective protection of the precision components in electronic circuits. Transient voltage suppression diode has a fast response time, the transient power, low leakage current, breakdown voltage deviation of consistency, the clamp voltage is easier to control, no damage to the limit, small size, etc..
But in actual use to find very easy to meet the requirements of the voltage value of the TVS device. Damage to the led 1w source is caused because the current ambassador chip internal overheating. TVS can only detect over-voltage can not detect over-current. Please select the appropriate voltage protection point difficult to grasp, this device will not be able to produce it would be difficult in practice.
3 Select the resettable fuse
Resettable fuse, also known as polymer positive temperature thermistor PTC, is constitute by the polymer and conductive particles. After special processing, The conductive particles in the polymer chain conductive path. When the normal operating current through (or components in a normal ambient temperature), PTC resettable fuse was the low resistance state; when the circuit when the abnormal over-current through (or environmental temperature), high current (or environmental temperature) heat generated by the rapid expansion of the polymer, also cut off the conductive path constituted by the conductive particles, PTC resettable fuse high-impedance state; When the over-current circuit (over-temperature state) after the disappearance of the polymer cooling, the volume recovery normal conductive particles to re-constitute a conductive path, PTC resettable fuse was the initial low resistance state. Since the resumption of normal operation small Fuse fever, abnormal working status of its high heating resistance limits the current through it, which plays a protective role. In a specific circuit, you can choose:
① shunt protection. High Power LED 50W generally divided into many cascaded slip. We can be in front of each branch and a PTC element to protect. The benefits of this approach is the high accuracy and the reliability of protection.
② overall protection. Increase access in all light beads in front of a PTC element, and to protect the whole lamp. The benefits of this approach is simple, does not account for the volume. For civilian products, such protection in the actual use of the results is satisfactory.