请问led调光电源是怎么做到调光的？原理是什么？哪个厂家做的led调光电源好展开全部下一篇：led调光灯是顾名思义是一种可以调节亮度的灯具，一般分为LED可调光射灯、LED可调光球泡灯和LED帕灯三种，在生活之中应用十分广泛，下面我led调光灯是一种可以根据客户要求来调整亮度的灯具，既能节约能源，减少碳排放，又可以为室内照明增添氛围，是颇受消费者喜爱的一种灯具，下面我们二十一世纪的来临，使得很多新型产品涌现了出来，而led背光板这样的物品就是现阶段很多朋友都在使用的产品，不仅有着低功耗、高亮度的优势，在散热Led照明灯具的发光原理和传统照明灯具不同。不同的Led芯片会导致Led照明灯具的电流大小不同。因此导致了Led照明灯具不同的调光要求。led背光板常见于宣传领域，它是指用LED(发光二极管)来作为液晶显示屏的背光源，可以配合其他相关类似的产品被助保障理想的效果。泛光灯在很多行业中被广泛使用，其中led泛光灯是泛光灯的一种，LED泛光灯是可以向四面八方均匀照射的点光源，LED泛光灯的主波长是会红移的，led软光条是目前照明行业比较先进的照明灯饰，led软光条主要是以聚酰亚胺PI基材制作的柔性电路板为载体的，并且是通过串联和并联电路设计帖装LED灯在日常生活中使用广泛，它比起传统灯泡来说质量、照明效果都更好，使用寿命也更长。而led泛光灯是一种可以照亮四面八方的点光源。led柔光灯是采用超高显色led作为发光元件，满足了电视新闻演播厅，各种会议室，多功能等专业照明要求的灯。智能调光玻璃是一种比较高端的产品，这种产品已经可以说得上是玻璃中的奢侈品了。一种路基于boose_buck拓扑的LED驱动电_文档下载
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一种路基于boose_buck拓扑的LED驱动电
一种路基于boose_buck拓扑的LED驱动电
2009年9月第20卷　第3期照明工程学报
ZHAOMINGGONGCHENGXUEBAOSep.　2009
Vol120　No13
一种基于boose2buck拓扑的LED驱动电路
姚　帅　余桂英
(中国计量学院计量测试工程学院,浙江杭州　310018)
摘　要:采用AT9930芯片,设计了一款车载LED驱动电路,其驱动、拓扑、调光方式分别采用更具优势的开关型变换器、boost2buck(升降压型)拓扑和PWM(脉宽调制)方式。实验证明,该驱动电路具有输入电压范围宽,恒流精度高,可靠性高、EMI(电磁干扰)低等特点。关键词:AT9930;升降压拓扑;开关型变换器;脉宽调制
LEDDriverBasedon2(offChinaMeasurementUniversity,Hangzhou　310018)
Abstract　
ALEDusedinautomobileapplicationwasproposed,basedonAT9930.Switchingconverter,boost2
bucktopologyandpulsewidthmodulation(PWM)dimming,theperformanceofwhichwasexcellent,werechosen.Theexperimentresultshowsthatthedriverhasadvantagesofwideinputvoltagerange,highaccuracyconstantoutputcurrent,highreliabilityandlowEMI.
Keywords:AT9930;boost2PWM
LED被公认为是21世纪最具发展前景的一种电
2　驱动方式
LED驱动方式可分为电阻限流、线性稳压器和
光源,具有节能、环保、体积小、响应速度快、抗震性能好等优点。近年,随着技术的进步,大功率LED性能逐渐提升,价格不断下降,在汽车行业的应用得以快速发展,成为第四代汽车光源,可预见汽车照明将会越来越多的使用LED光源。LED驱动电路是LED车灯设计的一个重要环节,汽车电源电压典型值为12V,实际电压范围在9～16V之间变化,并伴随可达36V的瞬间峰值电压和低至6V的冷启动电压。如何满足苛刻的汽车环境,设计一种可靠性高、EMI低的LED驱动电路成为LED车灯制造技术的关键。
开关型变换器三类。原始的电阻限流方案适用于低要求应用,此方案会在电阻上产生大量的热量,降低效率,故这种方式不适用于对效率要求极高、输入电压范围宽的汽车照明;线性稳压器是相对简单的方案,对于低电流LED,尤其是串联后的LED正向压降和稍低于电源电压的场合,使用线性稳压器方案更为合适,其同样存在效率和输入电压范围小的问题,不适合汽车照明;开关型变换器最灵活、效率更高,开关电源通过控制开关,在一个周期,对RLC电路充电,在下一个周期,存储的能量用来驱动负载。开关稳压器能提供多种线性稳压器所不
3基金项目:浙江省科技计划项目:LED汽车前照灯的研制()
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Buck-Boost Converters
After studying this section, you should be able to:
Understand the need for a choice of DC to DC converter designs.
Understand the principles of Buck-Boost Converters.
& The switching transistors.
& Switching control systems.
Understand the relationships between different converter designs.
& Buck converters.
& Boost converters.
& Buck-Boost converters.
Recognise the limitations on the output voltage.
Recognise typical commercial I.Cs. using buck boost technology.
Buck-Boost Converters
A Buck-Boost converter is a type of switched mode power supply that combines the principles of the
in a single circuit. Like other SMPS designs, it provides a regulated DC output voltage from either an AC or a DC input.
The Buck converter described in
produces a DC output in a range from 0V to just less than the input voltage. The boost converter will produce an output voltage ranging from the same voltage as the input, to a level much higher than the input.
There are many applications however, such as battery-powered systems, where the input voltage can vary widely, starting at full charge and gradually decreasing as the battery charge is used up. At full charge, where the battery voltage may be higher than actually needed by the circuit being powered, a buck regulator would be ideal to keep the supply voltage steady. However as the charge diminishes the input voltage falls below the level required by the circuit, and either the battery must be discarded or re- at this point the ideal alternative would be the boost regulator described in .
By combining these two regulator designs it is possible to have a regulator circuit that can cope with a wide range of input voltages both higher or lower than that needed by the circuit. Fortunately both buck and boost converters use ver they just need to be re-arranged, depending on the level of the input voltage.
Fig. 3.3.1 Buck and Boost Converters Combined
In Fig. 3.3.1 the common components of the buck and boost circuits are combined. A control unit is added, which senses the level of input voltage, then selects the appropriate circuit action. (Note that in the examples in this section the transistors are shown as MOSFETs, commonly used in high frequency power converters, and the diodes shown as Schottky types. These diodes have a low forward junction voltage when conducting, and are able to switch at high speeds).
Operation as a Buck Converter
Fig. 3.3.2 Operation as a Buck Converter During Tr1 &on& Period
The basic operation of the buck boost converter is illustrated in Figs. 3.3.2 to 3.3.5
Fig. 3.3.2 shows the circuit operating as a Buck Converter. In this mode Tr2 is turned off, and Tr1 is switched on and off by a high frequency square wave from the control unit. When the gate of Tr1 is high, current flows though L, charging its magnetic field, charging C and supplying the load. The Schottky diode D1 is turned off due to the positive voltage on its cathode.
Fig. 3.3.3 Operation as a Buck Converter During Tr1 &off& Period
Fig 3.3.3 shows the current flow during the buck operation of the circuit when the control unit switches Tr1 off. The initial source of current is now the inductor L. Its magnetic field is collapsing, the back e.m.f. generated by the collapsing field reverses the polarity of the voltage across L, which turns on D1 and current flows through D2 and the load.
As the current due to the discharge of L decreases, the charge accumulated in C during the on period of Tr1 now also adds to the current flowing through the load, keeping VOUT reasonably constant during the off period. This helps keep the ripple amplitude to a minimum and VOUT close to the value of VS.
Operation as a Boost Converter
Fig. 3.3.4 Operation as a Boost Converter During Tr2 &on& Period
In Boost Converter mode, Tr1 is turned on continually and the high frequency square wave applied to Tr2 gate. During the on periods when Tr2 is conducting, the input current flows through the inductor L and via Tr2, directly back to the supply negative terminal charging up the magnetic field around L. Whilst this is happening D2 cannot conduct as its anode is being held at ground potential by the heavily conducting Tr2. For the duration of the on period, the load is being supplied entirely by the charge on the capacitor C, built up on previous oscillator cycles. The gradual discharge of C during the on period (and its subsequent recharging) accounts for the amount of high frequency ripple on the output voltage, which is at a potential of approximately VS + VL.
The Off Period
Fig. 3.3.5 Operation as a Boost Converter During Tr2 &off& Period
At the start of the off period of Tr2, L is charged and C is partially discharged. The inductor L now generates a back e.m.f. and its value that depends on the rate of change of current as Tr2 switches of and on the amount of inductanc therefore the back e.m.f can be any voltage over a wide range, depending on the design of the circuit. Notice particularly that the polarity of the voltage across L has now reversed, and so adds to the input voltage VS giving an output voltage that is at least equal to or greater than the input voltage. D2 is now forward biased and so the circuit current supplies the load current, and at the same time re-charges the capacitor to VS + VL ready for the next on period of Tr2.
Buck-Boost Converter Animation
Fig. 3.3.6 Buck-Boost Converter Animation
Click the blue text box to start.
Choose Buck or Boost form the control unit.
See the operation ot the circuit in either Buck or Boost mode
See the current paths during the on and off periods of the switching transistor.
See the magnetic field around the inductor grow and collapse, and observe the changing polarity of the voltage across L.
Watch the effect of ripple during the on and off states of the switching transistor.
See the input voltage and the back e.m.f. of VL add to give an output voltage greater than the input voltage.
pause to hold the animation in either the on or the off state.
back to reset the animation.
Circuit Variations
There are a number of variations of this basic Buck-Boost circuit, some designs working at lower frequencies or at high voltages may use bipolar transistors instead of MOSFETs; at low frequencies the higher speed switching of MOSFETs is less of an advantage. Also, in high voltage designs, silicon diodes may be used in preference to Schottky types due to the silicon diode&s higher reverse voltage capabilities. Another variation is to use synchronous switching where, instead of using diodes that simply respond to the voltage polarity across them, four synchronised (by the control unit) MOSFETs do all the switching.
The control unit may also carry out over current and over voltage protection, as well as the normal oscillator and pulse width modulation functions to regulate the output voltage.
Another commonly used facility is &pulse skipping& where the control unit prevents charging on one or more oscillator pulses when it senses that the load current is low. This reduces the overall current drawn from the (typically battery) supply, prolonging battery life.
Buck-Boost Converter I.Cs. are commonly used to carry out the control unit functions. These range from very low power, high efficiency I.Cs. for portable devices such as mobile phones and automotive applications, such as the
series from , and the
from , to large industrial high power DC-DC converters providing many kilowatts of output power.}