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How to protect the LED Driver
Jul 01, 2017

LED driver power market and the downstream industry, especially the development of high-power LED lights are closely related, but with the LED performance parameters continue to improve, LED lighting market gradually rise, the application of a wider range, especially in 2011, industry vision From outdoor to indoor commercial lighting applications at the same time, the LED drive power also has a different demand. Now the problem of LED drive power is gradually exposed, and today come together to see LED drive power supply common problems.

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LED drive power supply common problems

1, LED driver circuit directly affects LED life

    We said that the LED driver, including digital-driven and analog-like drive, digital-driven digital circuit drivers, including digital dimming control, RGB full color changes and so on. Analog push refers to the analog circuit driver, including AC constant current switching power supply, DC constant current control circuit. The drive circuit consists of electronic components, including semiconductor components, resistors, capacitors, inductors, etc., these components have the use of life, any failure of a device will cause the failure of the entire circuit may be some function failure. LED use of life is 5-10 million hours, according to 50,000 hours count, a series of light, nearly six years of life. Switching power supply life is difficult to reach 6 years, the market selling power supply warranty period is usually 2-3 years, to reach 6 years warranty power supply is the military level, the price is usually 4-6 times the power supply, usually The lighting factory is very difficult to bear. So LED lighting problems for the drive circuit problems.

2, LED drive power cooling problem

    LED for the cold light source, operating junction temperature can not exceed the limit, the description will have to leave the remaining margin. The whole description of the lamp to consider the appearance of beautiful, convenient device, with light, heat and many other problems, to find a balance in many elements, so that all the lamps is the best .LED lamps do not long time to develop The experience is not much, many depictions are constantly perfect. Some LED lighting manufacturers use power for outsourced perhaps outsourcing, lamp depicts the power to know little, to the LED cooling space larger, to the power of the cooling space is smaller. Usually painted after the light and then find the appropriate power to match, so give the power supply to bring a certain degree of difficulty. Often encountered due to the smaller interior space of the lamp may be higher internal temperature, and the cost of manipulation is low, can not be equipped with appropriate power. Some LED lighting factory has power development talent, in the beginning to describe the early evaluation of the lamp, the power of the description of the synchronization, will be able to deal with the above problems. In the description of the LED to sum up the heat and power of the heat, all control the temperature rise of lamps, so that the ability to draw a better lamp.

3, LED drive power in the depiction of the problem

A. Power depiction. Although the LED light efficiency, but there are 80-85% of the heat loss, resulting in 20-30 degrees inside the lamp temperature rise, if the room temperature of 25 degrees, the lamp has 45-55 degrees, the power supply for a long time in high temperature environment Under the operation, to ensure that life must increase the power margin, usually left to 1.5-2 times the margin.

B. Component selection. Lamp internal temperature 45-55 degrees situation, the power supply temperature rise is about 20 degrees, then the component adjacent to the temperature to reach 65-75 degrees. Some components in the high temperature conditions will drift parameters, and some life will be shortened, so the equipment to be selected at a higher temperature for a long time to use, pay special attention to electrolytic capacitors and wires.

C. Electrical function depiction. Switching power supply alignment LED parameters, mainly constant current parameters, the size of the resolution of the brightness of the LED, if the bulk current error is large, the brightness of the entire batch of light is not uniform. And the temperature change can also cause the power supply output current offset. The same time as the above-

E. Certification problem. At present, China has not yet aligned with the norms of LED lamps, the relevant part of the country is being developed, the domestic sales of lamps and lanterns is certified with reference to the norms of lighting, export CE or UL certification is done, and some reference to foreign LED lighting specifications to do The So the alignment of this situation, the description of the switching power supply to be satisfied with the above specifications are more difficult, we can only match the different needs of different certification is not the same.

4, LED drive power supply parameters.

    Outsourcing drive power on the selection of the main constant current and constant current voltage scale. The constant current value is chosen as the specification of the LED current. Voltage scale selection should be moderate, try not to choose a larger scale, to prevent the power of the spoil.

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LED drive power protection method

1. Protection of LED drive power using the fuse (tube)

    As the fuse is a one-time, and the reaction is slow, the effect is poor, the use of trouble, so the fuse is not suitable for LED lamp products, because the LED lights are now mainly in the city of glorious engineering and lighting works. It requires the LED protection circuit to be very harsh: beyond the normal use of current can immediately start the protection, so that the LED power supply path was disconnected, so that LED and power can be protected in the normal light after the normal power supply can be restored, Does not affect the LED work. The circuit can not be too complicated volume can not be too much, the cost is even lower. So the use of the fuse to achieve it is very difficult.

2. LED driver power supply using transient voltage suppression diode

Transient voltage suppression diodes are a high-performance protection device in the form of diodes. When its poles are subjected to a reverse transient high-energy impact, the high resistance between the two poles can be reduced to a low resistance at a rate of 10 times the negative time of 10 times the square, absorbing up to several kilowatts of surge power , The voltage between the two poles in a predetermined voltage value, the effective protection of the electronic circuit in the precision components. Transient voltage suppression diode has the advantages of fast response time, transient power, low leakage current, good consistency of breakdown voltage, easy control of clamping voltage, no damage limit, small size and so on.

But in actual use found to find the required voltage to meet the TVS device is not easy. The damage to the LED beads is mainly due to the overcurrent of the chip. TVS can only detect overvoltages can not detect overcurrent. To choose the appropriate voltage protection point is difficult to grasp, this device can not be produced it is difficult to use in practice.

3. LED drive power selection from the recovery fuse

Self-healing fuses, also known as polymer polymer temperature thermistor PTC, is composed of polymer and conductive particles. When the normal operating current passes (or the component is at normal ambient temperature), the PTC self-recovery fuse is in a low resistance state; when there is an abnormal overcurrent in the circuit (or ambient temperature rises), the high current (or ambient temperature rises) The heat generated by the rapid expansion of the polymer, also cut off the conductive particles formed by the conductive path, PTC self-recovery fuse was high resistance state; in the normal working state self-recovery fuse fever is very small, in the abnormal working state of its High heat resistance is very large, also limited through its current, which played a role in protecting the LED drive power.

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