Protection circuit for LED driver 18650 battery 3.7v 2200mah

　　Although LED technology is the mainstream in today's market, there are still many unsolved problems in LED technology, and LED life, energy saving, and price issues have always been hotly discussed topics. In this process, the LED circuit protection circuit is very important. Let’s not talk about anything else. Let’s first discuss the experience summary of the three protection methods of the LED circuit:

　　1. Use fuses (tubes) to protect LED circuits

　　Because fuses are disposable, have slow response speed, poor effect, and are troublesome to use, fuses are not suitable for use in finished LED lights, because LED lights are now mainly used in urban glory projects and lighting projects. It requires the LED protection circuit to be very strict: when the normal current is exceeded, the protection can be started immediately, so that the LED 18650 battery 3.7v 2200mah path is disconnected, so that both the LED and the 18650 battery 3.7v 2200mah can be protected, and the 18650 battery 3.7v 2200mah can be automatically restored after the entire lamp is normal. Does not affect LED work. The circuit should not be too complicated, the volume should not be too large, and the cost should be low. Therefore, it is difficult to implement using fuses.

　　2. Use transient voltage suppression diodes (TVS for short)

　　The transient voltage suppression diode is a high-efficiency protection device in the form of a diode. When its two poles are impacted by reverse transient high energy, it can immediately reduce the high resistance between its two poles to low resistance at a very short speed of 10 minus 12 seconds, absorbing surge power up to several kilowatts. , clamping the voltage between the two poles at a predetermined voltage value, effectively protecting the precision components in the electronic circuit. Transient voltage suppression diodes have the advantages of fast response time, large transient power, low leakage current, good consistency of breakdown voltage deviation, easy control of clamping element voltage, no damage limit, and small size.

　　However, in actual use, it is found that it is not easy to find TVS devices that meet the required voltage value. The damage to the LED light source is mainly caused by excessive current causing overheating inside the chip. TVS can only detect overvoltage but not overcurrent. It is difficult to select the appropriate voltage protection point. This kind of device cannot be produced and is difficult to use in practice.

　　3. Select a resettable fuse

　　Resettable fuses, also known as polymer positive temperature thermistors PTC, are composed of polymers and conductive particles. After special processing, the conductive particles form chain-like conductive paths in the polymer. When the normal operating current passes (or the component is at normal ambient temperature), the PTC resettable fuse is in a low resistance state; when an abnormal overcurrent passes through the circuit (or the ambient temperature rises), a large current (or the ambient temperature rises) The heat generated causes the polymer to expand rapidly, thus cutting off the conductive path formed by the conductive particles. The PTC resettable fuse assumes a high resistance state; when the overcurrent (overtemperature state) in the circuit disappears, the polymer cools and the volume recovers. Normally, the conductive particles re-form the conductive path, and the PTC resettable fuse returns to its initial low-resistance state. In normal working conditions, the heat generated by the resettable fuse is very small. In abnormal working conditions, its heat generation is very high and its resistance is very large, which limits the current flowing through it, thus playing a protective role. In a specific circuit, you can choose:

　　①Shunt protection. Generally, LED lights are divided into many series-connected branches. We can add a PTC component in front of each branch for protection. The advantages of this method are high accuracy and good protection reliability.

　　②Overall protection. Add a PTC component in front of all light beads to protect the entire lamp. The advantage of this method is that it is simple and does not take up much space. For civilian products, the results of this protection in actual use are satisfactory.

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