有关LED照明电源设计难题的探讨

无 锡 职 业 技 术 学 院毕业设计说明书（英文翻译）英 文有关LED照明电源设计难题的探讨 The LED lighting power supply designProblems of design：1. Electrolytic capacitors and LED life issues do not match2. LED灯闪烁的常见原因与处理办法Common cause of LED lights flashing and approach 3. PWM 调光对LED的寿命有何影响利用TRIAC调光调控LED亮度的潜PWM dimming the impact on the life of LED dimming control4. Using RIAC LED brightness of the potential problems 在LED照明电源设计中，存在以下几个设计难题：电解电容寿命与LED不相匹配、LED灯闪烁的常见原因与处理办法、PWM 调光对LED的寿命有何影响、利用TRIAC调光调控LED亮度的潜在问题。In the LED lighting power supply design, there are several design challenges: life electrolytic capacitors do not match with the LED, LED lights flashing common causes and solutions, PWM dimming of the LEDs life impact of the use of TRIAC LED dimming control brightness of the potential problems. ON Semiconductor Senior Application Engineering Manager Cheng were in the text before the occurrence of these problems causes and solution to start on.1.电解电容寿命与LED不相匹配的问题Electrolytic capacitors and LED life issues do not match LED照明的一个重要的考虑因素，就是LED驱动电路与LED本身的工作寿命应该能够相提并论。LED lighting is an important consideration is the LED drive circuit and the LED itself should be able to compare the work of life. 虽然影响驱动电路可靠性的因素有很多，但其中电解电容对总体可靠性有至关重要的影响。Although the reliability of the factors affecting driver circuit a lot, but the overall reliability of electrolytic capacitors have a critical influence. 为了延长系统工作寿命，需要有针对性地分析应用中的电容，并选择恰当的电解电容。In order to extend the service life of the system, which requires focused analytical applications in capacitors, and select the appropriate electrolytic capacitors.实际上，电解电容的有效工作寿命在很大程度上受环境温度及由作用在内部阻抗上的纹波电流导致的内部温升影响。In fact, the effective working life of electrolytic capacitors in large part by environmental temperature and the role of the internal impedance of the ripple current caused by impact of the internal temperature rise. 电解电容制造商提供的电解电容额定寿命是根据暴露在最高额定温度环境及施加最大额定纹波电流条件下得出的。Electrolytic capacitor electrolytic capacitor manufacturers rated life is based on the maximum rated temperature, exposure to the environment and to exert maximum rated ripple current conditions obtained. 在105C时典型电容额定寿命可能是5,000小时，电容所实际遭受的工作应力相比额定电平越低，有效工At 105 C rated life of typical capacitance may be 5,000 hours, capacitance compared to the actual working stress suffered by the lower rating level, the more effective long working life. 因此，一方面，选择额定工作寿命长及能够承受高额定工作温度的电解电容当然能够延长工作寿命。Therefore, on the one hand, choose rated long life and can withstand high operating temperatures of electrolytic capacitors rated to extend the working life of course. 另一方面，根据实际的应力和工作温度，仍然可以选择较低额定工作温度和额定寿命的电容，从而提供更低成本的解决方案；换个角度说，在设计中考虑保持适当的应力和工作温度，可以有效地延长电解电容的工作寿命，使其更能与LED寿命相匹配On the other hand, according to the actual stress and temperature, you can still choose a lower temperature rating and rating life of the capacitor, thereby providing a more cost-effective solutions; another point of view, a proper consideration in the design of the stress and temperature, can effectively extend the service life of electrolytic capacitors, to better match with the LED lifetime.举例来说，安森美半导体符合“能源之星”固态照明标准的离线型LED驱动器GreenPoint参考设计选择了松下的ECA-1EM102铝电解电容，其额定值为1000 F、25 V、850 mA、2,000小时及85C。For example, ON Semiconductor meet Energy Star standards for off-line-based solid state lighting LED driver GreenPoint reference design chosen Panasonic ECA-1EM102 aluminum electrolytic capacitor, its rating of 1000 F, 25 V, 850 mA, 2,000 hours and 85 C. 在假定50C环境温度条件下，这电容的可用寿命超过12万小时Assuming 50 C ambient temperature conditions, the capacitance of the useful life over 120,000 hours. 因此，尽力使LED驱动电路工作在适宜的温度条件并妥善处理散热问题，就能实现LED驱动电路与LED工作寿命的匹配问题。Therefore, strive to make LED driver circuit in the appropriate temperature conditions and properly handle the heat dissipation, LED driver circuit can be achieved with LED working life of the matching problem.总的来看，如果LED驱动电路中必须使用电解电容，那就必须努力控制电容所受的应用力及工作温度，从而最大程度延长电容工作寿命，以期与LED寿命匹配；另一方面，设计人员也应该尽可能地避免使用电解电容。In general, if the LED drive circuit must use the electrolytic capacitor, it must strive to control the application of power capacitors and suffered operating temperature, thus extending the maximum capacitance of working life in order to match with LED life; the other hand, designers should also be possible to avoid the use of electrolytic capacitors.2.LED灯闪烁的常见原因与处理办3.Common cause of LED lights flashing and approach通常人眼能够感知到频率达70 Hz的光闪烁，高于这个频率则不会Usually the human eye can perceive frequencies up to 70 Hz flicker of light, above this frequency will not be perceived.故在LED照明应用中，如果脉冲信号出现频率低于70 Hz的低频分量，人眼就会感受到闪烁Therefore, in LED lighting applications, if the pulse signals frequency below 70 Hz low-frequency components, the human eye will feel the flicker. 当然，在具体应用中，有多种因素可能导致LED灯闪烁Of course, in specific applications, there are several factors that may cause LED light flashes. 例如，在离线式低功率LED照明应用中，一种常见的电源拓扑结构是隔离型反激拓扑结构For example, in offline LED lighting low-power applications, a common power supply topology is isolated flyback topology. 以安森美半导体符合“能源之星”固态照明标准的8 W离线型LED驱动器GreenPoint参考设计为例，由于反激稳压器的正弦方波功率转换并未给初级偏置提供恒定能量，动态自供电(DSS)电路可能会激活并引发光闪烁。ON Semiconductor to meet the Energy Star 8 W solid-state lighting standards-based off-line LED driver GreenPoint reference design, for example, because the flyback voltage regulator sine square wave power conversion bias is not to provide a constant primary energy, Dynamic Self-Supply (DSS) circuit may be activated and trigger a flashing light. To avoid this problem, must be made to the initial bias in each half cycle part of the discharge, the corresponding need to properly select the bias circuit constitute the capacitance and resistance value.另外，即使是在使用提供极佳功率因数校正、支持TRIAC调光的LED驱动应用中，也要求电磁干扰(EMI)滤波器。In addition, even in the use of power factor correction to provide excellent support of TRIAC dimming LED driver applications, also called electromagnetic interference (EMI) filter. 由TRIAC阶跃(step)引起的瞬态电流会激发EMI滤波器中电感和电容的By the TRIAC step (step) induced transient current EMI filter will stimulate the natural resonant inductor and capacitor. 如果这谐振特性导致输入电流降至TRIAC维持电流之下，TRIAC将会关闭If this resonance characteristics lead to reduced input current below the holding current TRIAC, TRIAC will be closed. After a short delay, TRIAC will turn often to stimulate the same resonance. 在输入电源波形的一个半周期内，这系列事件可能会重复多次，从而形成可见的LED闪烁。In a semi-input power waveform cycle, this series of events may be repeated several times to form the visible LED blinks. To address this problem, TRIAC dimmer is a key requirement is very low input capacitance EMI filter and the capacitor to be able to through the TRIAC and the winding impedance decoupling. 根据 公式，调光模块中电容减小的话，就能够增大谐振电路的电阻，原理上就抑制振荡，恢复想要的电路工作According to the formula, dimming module capacitance decreases, then it can increase the resonant circuit of resistance, on the principle of vibration suppression, restoration of the desired circuit.3.PWM 调光对LED的寿命有3PWM dimming of the LEDs life impactLED本身的寿命很长，PWM调光并不会损及LED的预期寿命；甚至由于PWM调光帮助减小LED发热量，实际上还能帮助延长LED预期寿命。Its very long life LED, PWM dimming LED will not hurt the life expectancy; even as PWM dimming LED to help reduce the heat, in fact, also help to extend the LED life expectancy. 当然，在系统设计中，需要有效地检测及控制LED温度，保证LED可靠工作，体现其长寿命和低维护成本的优势Of course, in the system design, the need for effective detection and control of LED temperature, to ensure reliable operation LED，reflecting its long life and low maintenance cost advantages.4.利用TRIAC调光调控LED亮度的潜4LED dimming control using TRIAC brightness of the potential problemsCurrent TRIAC dimming is fairly popular with the market welcomed the dimming mode. TRIAC dimmer originally designed for incandescent lamps, but such as ON Semiconductor has introduced a leading provider of support TRIAC dimming of the LED driver is ideal for LED lighting is provided in the TRIAC dimmer. However, this approach has its limitations lie, such as increased circuit complexity, affect the power factor; dimming level is relatively limited and so on. ON Semiconductor, as applied to the first green high-performance electronic products, energy efficient silicon solutions provider recently introduced for residential and commercial LED lighting applications. This device is using the critical conduction mode (CrM) anti-shock structure of a single-stage topology to provide power factor higher than 0.95,so they save DC - DC (DC-DC) conversion section, simplifying the circuit. This is low even when the device also offers high energy efficiency; comply with all regulatory requirements and overall system optical efficiency requirements. In addition, this device is compatible with the front end of TRIAC dimmer and dimmer along the transistor, depending on the use of dimmers, LED light output can be adjusted to less than 2%, providing excellent dimming performance.5. ON Semiconductors LED driver pushing the recent hot program安森美半导体近期推出了几款重要的高能效GreenPoint LED驱动器参考设计，分别是Semiconductor recently introduced several important energy-efficient GreenPoint LED driver reference design is:1) 3W至5 W LED驱动器参考设计方案。1) 3W to 5 W LED driver reference design. This reference design for MR16 LED replacement with the size and characteristics of configuration, have been carefully constructed and tested for driving high-brightness LED. 这参考设计基于降压-升压型拓扑结构，使用安森美半导体的非隔离型恒流配置、工作在约150千赫兹(kHz)频率的NCP3065开关稳压器。This reference design is based on buck - boost topology, using ON Semiconductors non-isolated constant current configuration, the work of about 150 kHz (kHz) frequency NCP3065 switching regulator. 这参考设计电路适合轨道照明、汽车照明及景观照明等12 Vac或12 Vdc应用，不论输入线路及输出LED电压如何变化，均提供平坦的电流稳流。This reference design circuit for track lighting, automotive lighting and landscape lighting, 12 Vac or 12 Vdc applications, regardless of input and output LED line voltage to change, provide a smooth steady flow of current. 这参考设计还提供独特的自动检测电路，支持12 Vdc或12 Vac电源输入，同时维持目标输出电流。 This reference design also provides a unique auto-detection circuit, supporting 12 Vdc or 12 Vac power input，while maintaining the target output current. 2) 隔离型8 W恒流LED驱动器GreenPoint参考设计方2) Isolated Constant Current LED Driver 8 W GreenPoint reference design. 这参考设计是为期望符合美国“能源之星”(ENERGY STAR)住宅照明应用1.1版固态照明(SSL)要求的设计人员而设，同样经过了精心构建及测试，用于驱动便携台灯、橱柜内照明及户外走廊灯等应用中的1到8颗大功率LED。This reference design is expected to meet the United States, Energy Star (ENERGY STAR ) residential lighting applications, version 1.1 Solid State Lighting (SSL) requests the designers designed the same have been carefully constructed and tested, used to drive portablelamps,cabinets corridors within the lamps and other lighting and outdoor applications in 1-8 high-power LED. 这参考设计采用新颖的电路配置，无须增加额外的无源功率因数校正(PFC)网络，即可在115 Vac条件下提供高于0.85的功率因数，减少了元器件数量，并轻松满足住宅LED应用功率因数要This reference design uses a novel circuit configuration，without additional passive power factor correction (PFC) network, you can under the conditions provided in the 115 Vac power factor above 0.85，reducing component count, and easily meet the residential LED Applications power factor requirements.这设计支持90 Vac至265 Vac的通用输入电压工作，采用安森美半导体集成了固定频率电流模式控制器和700 V MOSFET的NCP1014开关稳压器集成电路(IC)。This is designed to support 90 V to265 Vac universal input voltage, using ON Semiconductor integrated fixed-frequency current-mode controller and 700 V MOSFET in the NCP1014 switching regulator integrated circuit (IC).3) 针对离线式高功率因数TRIAC调光LED驱动器的GreenPoint参考设计。3) High power factor for offline TRIAC dimmer LED driver GreenPoint reference design. 这参考设计采用了NCL30000这关键器件，旨在用于美国“能源之星”商业及住宅照明应用This reference design uses NCL30000 this critical devices， intended for the United States, Energy Star commercial and residential lighting applications. NCL30000工作温度范围为-40C至+125C，确保能用于大多数固态照明(SSL)应用中规定的不同环境NCL30000 operating temperature range of -40 C to +125 C, to ensure that for most solid-state lighting (SSL) applications, the scope of work under different circumstances. NCL30000拥有典型值24微安(A)的低启动电流及典型值2 mA的低工作电流，配合高能效设计。NCL30000 has a typical value of 24 microamps (A),low startup current and low typical operating current of 2 mA, with energy-efficient design. NCL30000的其它关键特性包括可编程导通时间限制器、零电流检测(ZCD)感测模块、门驱动器，以及应用CrM开关电源所需的全部其它PWM电路和保护功能NCL30000 other key features include programmable on-time limiter, zero current detection (ZCD) sensor module, gate drivers, and application CrM switching power supply required by the other PWM circuit and protection.6.安森美半导体LED驱Semiconductor LED driver design advantages安森美半导体提供众多不同的LED驱动方案，用于宽广范围的应用：汽车、移动/便携(手机和数码相机的LCD背光及相机闪光)、中大尺寸的LCD屏幕(笔记本、上网本、液晶电视)的LCD背光、标志、建筑物，以及通用照明。ON Semiconductor offers a wide range of different LED-driven programs for a wide range of applications: automotive, mobile / portable (mobile phones and digital cameras, LCD backlight and camera flash), the large size of the LCD screen (laptop, netbook, LCD TV ) in LCD backlighting, signs, buildings, and general illumination.安森美半导体提供的产品涵盖3种LED驱动方法：线性方案(极简单且极少外部元件)、直流-直流(DC-DC)电感型开关转换器(用于提供高能效及较大电流)，以及电荷泵开关转换器(用于提供高能效及紧凑的尺寸)。ON Semiconductors offerings span three kinds of LED driving method: linear program (very simple procedure with few external components), DC - DC (DC-DC) inductive switching converter (used to provide energy efficiency and high current) and the charge pump switching converter (used to provide energy efficiency and compact size).总的来看，无论是何种LED照明应用，无论需要何种驱动方案，无论需要何种调光方法，无论采用何种常见电源电压供电，安森美半导体均可提供适合的LED驱动器方案，满足客户的不同需求。Overall, no matter what kind of LED lighting applications, no matter what kind driver program, no matter what kind dimming method, regardless of what common power supply voltage, ON Semiconductor may provide a suitable LED driver program to meet of customers the different needs.7. Current LED lamp features:High-power LED street lamp with conventional high pressure sodium lamps is different is that high-power LED street lamp light source with low voltage DC power supply, power from the GaN-based blue LED and yellow phosphor-based synthesis of highly efficient white LED, LED (Light Emitting Diode, abbreviated as LED) is based on the formation of semiconductor PN junction with the faint light of the high power solid-state light source can, in certain positive bias voltage and injection current into the P region into the hole and electron diffusion region N After the active region to be issued by the radiative photon light energy directly into electrical energy.LED lamp as light source, which compared the traditional lamp light source has many advantages：1. LED Street light, point of itself, does not diffuse light, to ensure optical effect;2. LED lamp has a unique secondary optical design, LED street lamp light shines on the area required for lighting, that is the road to further improve the light efficiency and save energy;3. LED light source efficiency of the current has reached 100lm / W, but there is still much room for development, the theoretical value can reach 250lm / W. The luminous efficiency of high pressure sodium lamp with the power to increase only increase, and therefore, the overall optical efficiency stronger than the high pressure sodium lamp LED lamps;4.LED street light color rendering than the high-pressure sodium lamp high pressure sodium lamp color rendering index of only 23, while the LED lamp color rendering index can reach 75 or more, from the visual psychological perspective, to achieve the same brightness, LED street lamp illumination average of lower than 20% above the high-pressure sodium lamp (lighting the light of British standard); and, in the middle of the visual level, the human eye in high color temperature environments with low color temperature than the environment can identify more easily things, to avoid the occurrence of some danger;5. LED street light decline of small, one-year decline of less than 3% of light, using 10 years of road use is still to achieve illumination requirements, therefore, LED street lamp design, the use of power can be lower than the high-pressure sodium lamp;6. LED lights that automatically adjust light, to achieve different times to meet the lighting requirements, the maximum possible reduction in power, saving energy;However, recently heard the views of many experts and scholars, that the LED lights to replace high pressure sodium lamp as technically immature. The main reasons are the following:1. LED luminous efficiency and high-pressure sodium lamp can not be compared2. LEDs light is too concentrated, the poor uniformity of illumination3. LED street light failure severe, life is not long4. LED lamp itself, the excessive weight, not easy installation, wind5. LED lamps and high cost, can not be widelyWe view one by one according to the above analysis:1. Luminous efficiencyAt present, LED light-emitting efficiency of Looking at the figures do not as high pressure sodium. LED light efficiency is generally 65 75lm / w, but with the technology, LED light effects increased each year, while the high-pressure sodium lamp can reach 125lm / w. However, the high-pressure sodium lamp of the spectrum are relatively concentrated in yellow, it The color temperature is relatively low, only 2000 2500K, and LED color temperature higher than can reach 3500 4500K. Another high pressure sodium light is launched to 4, with much of the light can not reach the road. Also, high pressure sodium lamp color index is poor, only 23 or so, feeling faint; the LEDs high CRI, can reach 75 to 80. Road bright, comfortable. So from a practical perspective glow, LED but much higher than the high-pressure sodium lamp. The LED can replace 250W 135W high pressure sodium lamp, or 300W for mercury. 135W of LED, the output of only about 7020 lumens luminous flux (after the second optical design, will be lost), to reach the road when the number is still 6500 lumens lumens, while the average road surface illuminance can reach 16Lux (12m high pole). 250W high pressure sodium lamp luminous flux output of 20,000 lumens. But the road to reach