IACS CO., LIMITED (Yiwu Fuwei e-commerce firm)

The led lamp bead is a voltage-sensitive device that is capacitively resistant to load. In actual work, the current accuracy is higher, which is one of the main problems affecting the luminous efficiency and the life of the LED lamp bead. In the drive circuit, various factors cause a sudden change in the voltage. If no protective measures are taken, the LED will be damaged after the increased current exceeds a certain time and amplitude.

The main causes of LED damage are:

1 The power supply voltage suddenly rises and the surge increases.

2 A short circuit of a component or printed line or other wire in the line forms a partial short circuit of the LED power supply path, which increases the voltage at this place; the solder joint is soldered or loose.

3 An LED is short-circuited due to its own quality, and its original voltage drop is transferred to other LEDs; the internal resistance of the LED changes, and the voltage on the LED is uneven.

4 The temperature inside the lamp is too high, which makes the characteristics of the LED deteriorate; the local temperature rise inside the lamp is too fast; the temperature is too high during soldering or immersion.

5 The inside of the lamp is filled with water, and the water is electrically conductive; the heat flow inside the enclosed lamp is accumulated to form water vapor or mist.

6 In the process of the process, there is no anti-static work, so that the inside of the LED has been damaged by static electricity. Despite the application of normal voltage and current values, it is extremely susceptible to LED damage.

7 The light source test is quickly turned on and off, and the inter-electrode charge discharge (ie, fading out when turned off).

8 Washing the plate water and washing the nano wave.

9 live operation; all fixtures and fixtures do anti-static work; maintain the temperature and humidity of the environment.

The protection of LED circuits can be considered as follows:

1. Self-recovery insurance in the protection circuit

The self-recovery insurance at the input end is more suitable for the protection of the large current load as a protection device. Multi-channel LEDs are suitable for self-recovery insurance with high power or at higher temperatures.

2. Use transient voltage suppression diode (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 subjected to reverse transient high energy shock, the high resistance between the two poles can be immediately reduced to low resistance at a very short time of 10 minus 12 power seconds, absorbing up to several kilowatts of surge power. The voltage between the two poles is clamped to a predetermined voltage value, which effectively protects the precision components in the electronic circuit. The transient voltage suppression diode has the advantages of fast response time, large transient power, low leakage current, good uniformity of breakdown voltage, easy control of clamping voltage, no damage limit, and small volume.

However, in actual use, it has been found that it is not easy to find a TVS device that satisfies the required voltage value. The damage of the LED beads is mainly caused by overheating inside the chip due to excessive current. TVS can only detect overvoltages and cannot detect overcurrents. It is difficult to master the proper voltage protection point, and the device cannot be produced and is difficult to use in practice.

3. Use varistor

The voltage output terminal is connected to a surge suppression type pressure sensitive function, which can well absorb the set value surge, and the load LED can be prevented from being over-voltage. The working principle is simply to use the nonlinear characteristic of the varistor. When an overvoltage occurs between the two poles of the varistor, the varistor can clamp the voltage to a relatively fixed voltage value, thereby realizing the circuit of the latter stage. protection.

4. Select PTC

The positive temperature thermistor PTC is composed of a polymer, conductive particles, and the like. After special processing, the conductive particles form a chain-like conductive path in the polymer. When the normal working current of the conductive particles passes (or the component is at normal ambient temperature), the PTC self-recovery fuse is in a low-resistance state; when there is abnormal overcurrent in the circuit (or the ambient temperature rises), the large current (or ambient temperature) The heat generated by the rapid expansion of the polymer causes the conductive path formed by the conductive particles to be cut off, and the PTC self-recovery fuse is in a high resistance state; when the overcurrent (overtemperature condition) in the circuit disappears, the polymer is cooled. The volume returns to normal and reconstitutes the conductive path, and the PTC is in an initial low resistance state. In the normal working state, the self-recovery fuse has little heat, and in the abnormal working state, its heat is very high, which limits the current passing through it, thereby protecting. In the specific circuit, you can choose:

1 branch protection

      The general LED light is divided into a number of serial branches. We can add a PTC component in front of each branch for protection. The benefits of this approach are high accuracy and good reliability of protection.

2 overall protection

       A PTC component is attached to the front of all the beads to protect the entire lamp. The benefit of this approach is simple and does not account for size. For civilian products, the results of this protection in actual use are still satisfactory.

5. Output capacitor and output capacitor bleeder resistor

There is an output output capacitor bleeder resistor, which does not necessarily have an output capacitor, but the output capacitor bleeder resistor must have it. Its function as a dummy load will work after the LED is disconnected.

Yiwu Fuwei e-commerce firm (IACS Co., Limited) is a very professional Led manufacturer who produces high quality outdoor led light. Our popular products are solar led lights, UFO lights, underwater lights and so on. If you have any question about the led product, please feel free to contact us.