LED power quality identification

2019-08-12 16:52:58

The function of the LED driver is to convert the AC mains into a DC that is suitable for the LED. Factors such as reliability, efficiency, power factor, drive mode, surge protection, and temperature negative feedback protection should be considered when selecting and designing the LED driver. The LED driver of outdoor lamps should be waterproof and moisture-proof. Light fast, not aging to ensure that the life of the drive power can be matched with the life of the LED. Jinjian Lab is a third-party laboratory specializing in LED quality management. It has a professional technical team and accumulated rich experience in LED related testing to provide customers with efficient and high quality LED packaging services.

 

 

(1) Power output parameters: voltage, current; (2) Whether the driving power supply can guarantee the characteristics of constant current output, whether it is pure constant current driving mode or constant current constant voltage driving mode; (3) Whether it has separate overcurrent protection and short circuit Protection and open circuit protection; (4) Power supply leakage identification: When the power is on, the outer casing should be free of charge; (5) Ripple voltage detection: no ripple voltage is optimal, when there is ripple voltage, the smaller the peak value, the better; 6) Strobe evaluation: no strobe after LED street light is on; (7) Power output voltage/current: When powering on, the power output should not have large voltage/current; (8) Whether the power surge meets relevant standards

 

LED driver power is one of the core components of LED lighting products. Its performance has an extremely important impact on the overall quality of lighting products: the efficiency of driving power supply is not high, the energy conversion ratio is low, which not only affects the lighting quality of lighting products, but also Bringing a large heat dissipation problem; driving failure is an important factor affecting the life of LED lighting products. Statistical analysis of 5400 盏 outdoor LED street lamp power failure data in Elwood City, USA, 59% failure of LED street lamps and driving power supply and its control device Related to the failure. LED driver failure is related to many factors. Electromagnetic interference is an important aspect. Especially with the development of drive technology, the electronic integration of drive power is getting higher and higher, including not only the drive circuit, but also the LED electronic control or dimming circuit. . Therefore, Jinjian laboratory experts believe that the testing and evaluation of its electromagnetic compatibility characteristics (including electromagnetic interference and anti-interference) is very important, and it is an important factor to consider driving failure.

 

In recent years, dimming technology has been gradually applied in the field of LED lighting, especially in the field of commercial lighting. Dimmer Compatibility and Flicker performance have attracted the attention of many international standards organizations, such as the US Energy Star and the International Energy Agency's 4E plan, all of which propose dimming compatibility and strobe. Testing requirements. Therefore, the test and evaluation of the LED driver should be based on its own functional characteristics, and through the effective detection methods of Jinjian, comprehensive consideration.

 

 

LED drive power standards include LED drive electrical performance, EMC electromagnetic compatibility and other features and testing. In April 2013, ENERGY STAR released the final draft of the ENERGY STAR® Program Requirements Product Specification for Lamps (Lamps FD), which included the testing of the ringing wave in the transient protection characteristics. The test standard is ANSI. /IEEE C62.41.2. At the same time, for dimmable LEDs, it is also required to measure the maximum value of the flicker indicator. The International Energy Agency (IEA) has also previously suggested that the Flicker Index should not be greater than 0.3% for full-power street lighting. From the definition of various standards and the development trend of international standards, LED driver not only needs to measure the basic electrical properties, EMC and other characteristics, but also needs to investigate the transient protection characteristics and the scintillation index and other characteristic parameters according to its application.

 

Electrical performance is the basic characteristic of LED driving. The performance is directly related to the light quality and energy efficiency conversion of LED. There are many parameters to be considered, including steady flow (voltage) range, power factor, startup time, and output overvoltage ( Flow) protection value, input surge current, and output current (voltage) ripple. Such a large number of electrical performance indicators, generally need to use a variety of testing equipment combined measurement, the operation is very cumbersome. Figure 1 (left) shows a typical LED power performance analyzer (LT-101), Figure 1 (right) shows the measurement schematic of the LT-101 LED driver, and the LT-101 can simultaneously test the input and output characteristics of the LED driver. One instrument can meet all measurement requirements, can fully meet the standard requirements, and the LT-101 also has output ripple measurement and harmonic analysis.

 

The EMC (Electromagnetic Compatibility) of LED driving power sources includes electromagnetic interference (EMI) and electromagnetic sensitivity (EMS). EMI (Electromagnetic Interference) requires that the electromagnetic interference generated by the LED drive power system during the normal operation of the environment and other things (including equipment, systems, people, animals and plants) should not exceed a certain limit. EMS (Electromagnetic Susceptibility) is electromagnetic sensitivity (immunity resistance). This characteristic requires the LED driving power system itself to have stable running performance under electromagnetic disturbance, such as the ability to resist interference such as lightning strikes, static electricity, and ringing waves. For different EMC characteristics, the standard test requirements are different, and you must select your own professional test plan for testing. The following is a description of the EMS performance tests that are important for LED driver power supplies and that are most likely to cause failure.

 

Natural lightning strikes, power system switching, equipment grounding grids or short circuits between grounding systems can cause surges in the LED drive in this environment, which can lead to equipment failure and damage. Therefore, the standard GB/T 17626.5/IEC61000-4-5 clearly defines the anti-surge impact performance of electrical equipment.

 

There are many semiconductor devices in the LED driving power circuit, which may encounter electrostatic discharge during manufacturing, assembly, transportation, storage and use, resulting in malfunction and failure of the LED driving power supply. The electrostatic discharge test of LED driver power electronics can be in accordance with American national standards ANSI/ESD STM5.1, ANSI/ESD STM5.2, US military standard MIL-STD-883 and International Electrotechnical Association standards JESD22-A114D, JESD22-A115 -A, etc. Figure 4 shows the ESD-1000 LED electrostatic analysis test system designed for LED electrostatic test in Hangzhou Yuan. The machine mode (MM) and human body mode (HBM) electrostatic discharge test can be realized according to the standard requirements. The discharge voltage can reach up to 30kV. In addition, for the electrostatic discharge immunity of the overall LED drive power system, the test shall be carried out in accordance with GB/T 17626.2/IEC61000-4-2. Contact discharge is the first test solution, and air discharge can be used at locations where contact discharge is not possible. Indirect discharge shall be tested according to the content specification of Section 7 of GB/T17626.2.

The ringing wave detection is mainly for examining the ability to drive interference against the switching of power lines and control line switches of electronic and electrical equipment in the power grid. The ringing wave waveform is shown in Figure 5 (left). This feature has been included in the product certification considerations by ENERGY STAR and indicates that the test is performed in accordance with ANSI/IEEE C62.41.2. In addition, the standard IEC61000-4-12 and GB/T17626.12 also regulate this. Figure 5 (right) is a typical ringing wave generator (Hangzhou Yuanfang Instrument Co., Ltd., EMS6100-12C), its oscillation frequency is 100Hz, the test voltage peak can reach 6kV, and can repeat up to 60 transients in 1 minute, which can be very It is good to meet the test requirements of each relevant standard.

 

Dimming technology has been gradually applied to various types of LED lighting products, and the process of intelligent lighting has been opened, but the dimming compatibility and stroboscopic characteristics brought about by this have also attracted much attention. The LED can be dimmed by an integrated dimming circuit inside the driving power supply or by an external dimming controller, but both of them often cause ripple of the LED DC power supply due to incompatibility of the driving circuit, and the LED light source strobes. In theory, the stroboscopic characteristics can be evaluated by the output ripple characteristics (measured by the LT-101), but more of them reflect the LED light output characteristics. Therefore, the measurement of the light output variation characteristics through the LED will More objective.

 

Strobe can cause visual fatigue, vertigo, migraine, etc., and in the field of road lighting, strobe can also cause the driver to have the illusion and cause traffic accidents, so it is getting more and more attention from relevant international standards organizations. Both the US Energy Star and the International Energy Agency (4E Program) have performance requirements. The former specifies in its Lamps FD that the lighting fixtures need to measure the maximum value of the scintillation indicator. The latter stipulates in the performance specifications of its SSL street lighting fixtures that the flashing index of the luminaire is not more than 0.3% at full power.