三種保護LED電路方法的經驗總結,three methods of protection Experience of LED circuit

關鍵字：三種保護LED電路方法的經驗總結

1.保護LED電路中采用保險絲(管)
由于保險絲是一次性的，且反應速度慢，效果差、使用麻煩，所以保險絲不適宜用于LED燈成品中，因為LED燈現在主要是在城市的光彩工程和亮化工程。它要求LED保護電路要很苛刻：在超出正常使用電流時能立即啟動保護，讓LED的供電通路就被斷開，使LED和電源都能得到保護，在整個燈正常后又能夠自動恢復供電，不影響LED工作。電路不能太復雜體積不能太大，成本還要低。所以采用保險絲的方式實現起來很困難。
2.使用瞬態電壓抑制二極體（簡稱TVS）
瞬態電壓抑制二極體是一種二極體形式的高效能保護器件。當它的兩極受到反向瞬態高能量沖擊時，能以10的負12次方秒極短時間的速度，使自己兩極間的高阻立即降低為低阻，吸收高達數千瓦的浪涌功率，把兩極間的電壓鉗位元在一個預定的電壓值，有效的保護了電子線路中的精密元器件。瞬態電壓抑制二極體具有回應時間快、瞬態功率大、漏電流低、擊穿電壓偏差一致性好、鉗位元電壓較易控制、無損壞極限、體積小等優點。
但是在實際使用中發現要尋找滿足要求電壓值的TVS器件很不容易。 LED光珠的損壞主要是因為電流過大使芯片內部過熱造成的。 TVS只能探測過電壓不能探測過電流。要選擇合適的電壓保護點很難掌握，這種器件就無法生產也就很難在實際中使用。
3.選擇自恢復保險絲
自恢復保險絲又稱為高分子聚合物正溫度熱敏電阻PTC，是由聚合物與導電粒子等構成。在經過特殊加工后，導電粒子在聚合物中構成鏈狀導電通路。當正常工作電流通過（或元件處于正常環境溫度）時，PTC自恢復保險絲呈低阻狀態；當電路中有異常過電流通過（或環境溫度升高）時，大電流（或環境溫度升高）所產生的熱量使聚合物迅速膨脹，也就切斷了導電粒子所構成的導電通路，PTC自恢復保險絲呈高阻狀態；當電路中過電流（超溫狀態）消失后，聚合物冷卻，體積恢復正常，其中導電粒子又重新構成導電通路，PTC自恢復保險絲又呈初始的低阻狀態。在正常工作狀態自恢復保險管的發熱很小，在異常工作狀態它的發熱很高阻值就很大，也就限制了通過它的電流，從而起到了保護作用。在具體的電路中，可以選擇：
①分路保護。一般LED燈是分成很多串接支路。我們可以在每個支路的前面加一支PTC元件分別進行保護。這種方式的好處是精確性高，保護的可靠性好。
②總體保護。在所有光珠的前面加接一支PTC元件，對整燈進行保護。這種方式的好處是簡單，不占體積。對于民用產品來說，這種保護在實際使用中的結果還是令人滿意的。

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.