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Three kinds of LED circuit protection methods summarized experience - (AddTime -2013-02-02)

Although LED technology is the market mainstream, but there are a lot of LED technology (no problem, and the life of the LED and energy saving, the price is always for your topic of discussion. And in this process LED circuit protection circuit is very important, what all do not say first, first to discuss three kinds of LED circuit protection method of experience conclusion:

1. Protect LED circuit with fuse (tube)

Due to the fuse is one-off, and reaction speed is slow, the effect is bad, the use of trouble, so fuse adapted for use in 200W led flood lights, 200W led flood lights in finished products because now it is primarily in cities that glorious engineering and lighting engineering. It requires LED protection circuit to very harsh: in beyond normal use current can immediately start protection, let LED power supply channel will be disconnected, LED and power can be protected, in the whole lamp normal and automatically restore power, do not affect LED work. Circuit can't too complicated volume can not be too big, the cost is still lower. So the fuse way difficult to achieve.

2. Use transient voltage inhibition diode (hereinafter referred to as TVS)

Transient voltage inhibition diode is a diode forms of effective protection device. When its polar is reverse transient high energy impact, to 10 negative power of 12 seconds a very short time speed, make oneself of the high resistance between the poles immediately reduced to low resistance, absorb as much as several kilowatts of surge power poles, between the voltage clamp yuan at a predetermined voltage value, effective protection of the electronic circuit precision components. Transient voltage inhibition diode has fast response time, transient power, low leakage current, breakdown voltage deviation good consistency, clamp yuan voltage is easy to control, no damage to the limit, and small volume etc advantages. But in actual use to find that meet the requirements of the voltage value TVS device is very not easy. 200W led Flood light source damage mainly because of a current ambassador chip internal caused by overheating. TVS can only detect overvoltage can't detection over current. To select the right voltage protection point difficult to master, this device can't production is hard to use in practice.

3. Choose from recovery fuse Since the recovery fuse is also known as polymer positive temperature thermal resistance PTC, is by the polymer and the conductive particles constitute. After special processing, conductive particles in polymer composition chain conductive path. When the normal work of the current through the (or element in the normal environment temperature), PTC since the recovery fuse is low resistance state; When the circuit has abnormal over current through the (or environmental temperature), large current (or environmental temperature) generated heat make polymer rapid expansion, also cut off conductive particle a conductive path, PTC since the recovery fuse is high impedance state; When the circuit over current (overtemperature condition) disappears, polymer cooling, the volume to return to normal, the conductive particles and to constitute a conductive path, PTC self recovery fuse and the initial state of low resistance. In normal working condition from recovering the pipe heat is small, in abnormal working state its heating very high resistance is very big, also limited the current passing through it, so as to protect the role. In the specific circuit, can choose:

(1) shunt protection. General LED lamp is divided into many cascading branch. We can in front of each branch with a PTC element separately protection. The benefit of this approach is of high accuracy, good reliability of protection.

(2) the overall protection. In front of all light bead and pick a PTC element, to protect the whole lamp. The benefit of this approach is simple, do not take a volume. For civil products it, this kind of protection in the actual use of the results is satisfactory.