三种保护LED电路方法的经验总结-----three methods of protection Experience of LED circuit

1.保护LED电路中采用保险丝(管)
由于保险丝是一次性的，且反应速度慢，效果差、使用麻烦，所以保险丝不适宜用于LED灯成品中，因为LED灯现在主要是在城市的光彩工程和亮化工程。它要求LED保护电路要很苛刻：在超出正常使用电流时能立即启动保护，让LED的供电通路就被断开，使LED和电源都能得到保护，在整个灯正常后又能够自动恢复供电，不影响LED工作。电路不能太复杂体积不能太大，成本还要低。所以采用保险丝的方式实现起来很困难。
2.使用瞬态电压抑制二极体（简称TVS）
瞬态电压抑制二极体是一种二极体形式的高效能保护器件。当它的两极受到反向瞬态高能量冲击时，能以10的负12次方秒极短时间的速度，使自己两极间的高阻立即降低为低阻，吸收高达数千瓦的浪涌功率，把两极间的电压钳位元在一个预定的电压值，有效的保护了电子线路中的精密元器件。瞬态电压抑制二极体具有回应时间快、瞬态功率大、漏电流低、击穿电压偏差一致性好、钳位元电压较易控制、无损坏极限、体积小等优点。
但是在实际使用中发现要寻找满足要求电压值的TVS器件很不容易。 LED光珠的损坏主要是因为电流过大使芯片内部过热造成的。 TVS只能探测过电压不能探测过电流。要选择合适的电压保护点很难掌握，这种器件就无法生产也就很难在实际中使用。
3.选择自恢复保险丝
自恢复保险丝又称为高分子聚合物正温度热敏电阻PTC，是由聚合物与导电粒子等构成。在经过特殊加工后，导电粒子在聚合物中构成链状导电通路。当正常工作电流通过（或元件处于正常环境温度）时，PTC自恢复保险丝呈低阻状态；当电路中有异常过电流通过（或环境温度升高）时，大电流（或环境温度升高）所产生的热量使聚合物迅速膨胀，也就切断了导电粒子所构成的导电通路，PTC自恢复保险丝呈高阻状态；当电路中过电流（超温状态）消失后，聚合物冷却，体积恢复正常，其中导电粒子又重新构成导电通路，PTC自恢复保险丝又呈初始的低阻状态。在正常工作状态自恢复保险管的发热很小，在异常工作状态它的发热很高阻值就很大，也就限制了通过它的电流，从而起到了保护作用。在具体的电路中，可以选择：
①分路保护。一般LED灯是分成很多串接支路。我们可以在每个支路的前面加一支PTC元件分别进行保护。这种方式的好处是精确性高，保护的可靠性好。
②总体保护。在所有光珠的前面加接一支PTC元件，对整灯进行保护。这种方式的好处是简单，不占体积。对于民用产品来说，这种保护在实际使用中的结果还是令人满意的。

google translate

Three kinds of methods to protect LED Circuit Experience
1. Protect the LED circuit with fuse (tube)
As the fuse is a one-off, and the reaction is slow, ineffective, cumbersome to use, so not suitable for LED lights fuse finished, because LED lights are now mainly works in the city's glory and the lighting project. It calls for LED protection circuit to be very harsh: When in excess of normal can immediately start using the current protection for LED power supply channel was off, so that the power LED and can be protected, in the light then automatically resume normal for power, does not affect the LED work.Circuit size not too big not too complicated, the cost is even lower. So with the way the fuse was very difficult to achieve.
2. Use of transient voltage suppression diodes (referred to as TVS)
Transient voltage suppression diode is a diode form of high-performance protective devices. When it's poles by the reverse transient high-energy shock to the 10 th power of negative 12 seconds a very short period of time the speed, high resistance between the poles themselves immediately reduced to low resistance, absorb up to several kilowatts of power surge , the voltage between the poles clamp element in a predetermined voltage value, and effective protection in the circuit of precision components. Transient voltage suppression diodes have fast response time, transient power, low leakage current, breakdown voltage deviation consistency, for voltage clamp easier to control, no damage limit, the advantages of small size.
However, in actual use was found to meet the requirements of voltage to find the TVS device is not easy. LED Light bead damage was mainly due to overheating chip overcurrent caused by the Ambassador. TVS can detect over-voltage can not detect over-current. To select the appropriate voltage protection is difficult to grasp, this device can not be produced would be very difficult to use in practice.
3. Select from the restoration of fuse
Resettable fuse, also known as polymer positive temperature thermistor PTC, is a polymer with conductive particles such as composition. After special processing, the conductive particles form chains in the polymer conductive pathway. When the normal operating current through (or components in a normal ambient temperature) when, PTC resettable fuse presents low resistance state; when the circuit by an abnormal over-current (or environmental temperature), the large current (or environmental temperature) the heat generated by the rapid expansion the polymer, thus cutting off the conductive particles are composed of conductive pathways, PTC resettable fuse was high impedance state; when the circuit over-current (over temperature state) disappears, polymer cooling, the volume recovery normal, in which conductive particles constitute a conductive path again, PTC resettable fuse again showed the initial low resistance state. In normal operation to resume security control of the heat from a small, abnormal working conditions in the heat of its high resistance to large, thus limiting the current through it to play a protective effect. In the specific circuit, you can choose:
① shunt protection. LED lamp is generally slip into a lot of concatenation. We can slip in front of each component separately add a PTC protected. This approach has the advantage of high accuracy, good reliability of protection.
② overall protection. In all preceded by light beads then a PTC element, the entire light protection. Advantage of this approach is simple, not bulky. For civilian products, such protection results in actual use or satisfactory.