具有环境温度补偿功能的白光LED驱动芯片的研究与实现
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摘要
白光LED(Light Emitting Diode,发光二极管)由于具有发光强度大、效率高、体积小、寿命长等优点,在电子消费产品照明和背光中是最受欢迎的选择,但是允许流过白光LED的电流受温度影响非常大。传统的白光LED驱动芯片设计,必须考虑高温情况下白光LED的安全性而将其输出电流限制在足够低的值。
针对该问题,本文设计了一款具有环境温度补偿电路的白光LED驱动芯片,能够按照白光LED电流的温度特性曲线,动态地调节驱动芯片的输出电流,从而保证了芯片在全工作温度范围内输出最大的电流值,因此可以用较少的白光LED来实现同样的亮度,降低了应用方案的成本,而且高温时LED不会因为驱动电流过大而损坏,提高了可靠性。
本文首先搭建了芯片的整体构架,采用了便携式应用的首选,电感式升压转换器来驱动白光LED,芯片采用了电流模式PWM控制方式,环境温度补偿技术,从而提高了芯片的快速性,可靠性,经济性和适用性。接下来,对芯片中的三个主要子模块——环境温度补偿电路、170mV比较器电路和欠压保护电路的设计进行了详细讨论,并利用HSPICE仿真工具结合UMC 0.6μm BCD工艺库对所设计电路进行了仿真验证。
最后,利用HSPICE仿真工具对芯片进行了全局仿真:芯片工作在1 MHz的频率下,最多能驱动7个LED,工作电流为25 mA,最高的转换效率可达到86%,低压下能利用欠压保护电路及时保护芯片,能够实现Analog和Direct-PWM亮度调节功能,仿真结果表明设计的芯片达到了预期的要求。
The white LED(Light Emitting Diode) is a welcome choice for illumination and backlighting in consumer electronics, but its allowable forward current is greatly affected by temperature. In traditional white LED driver design, its output current is determined by the maximum working temperature,comparatively small.
In this thesis, a novel white LED driver IC is proposed which can dynamically adjust the driver’s output current corresponding to the white LED’s current-temperature curve. Therefore the highest output current can be safely set over the entire operating temperature range, thereby allowing fewer LEDs to be used for normal display brightness which reduce the cost of application. Moreover, this circuit can protect LEDs from over-driving during high ambient temperatures, so it enhancing the chip’s reliability.
In the main part of this thesis, firstly, the whole chip’s structure is constructed. Using inductor step-up converter to drive White LED is a major method for portable applications. In the process of chip design, the current mode PWM control and ambient temperature compensation technology for increasing the chip's speed, reliability, economic and applicability. And then, the key interrelated technique for Boost DC/DC is studied and the whole chip structure is constructed. The main sub-circuits such as Ambient Temperature Compensation, 170mV Comparator and Under-Voltage Lockout Circuit are designed and implemented with UMC 0.6μm BCD process, and the simulation results are also presented.
Finally, HSPICE simulation results of the whole Chip are given: 1 MHz switching frequency. Up to 7 LEDs at 25 mA and the highest conversion efficiency of 86% can all be achieved. The chip can be timely protected by the under voltage protection function. Analog Direct-PWM and brightness adjustment functions can also be achieved. Simulation results show that the chip has achieved the expected demand.
针对该问题,本文设计了一款具有环境温度补偿电路的白光LED驱动芯片,能够按照白光LED电流的温度特性曲线,动态地调节驱动芯片的输出电流,从而保证了芯片在全工作温度范围内输出最大的电流值,因此可以用较少的白光LED来实现同样的亮度,降低了应用方案的成本,而且高温时LED不会因为驱动电流过大而损坏,提高了可靠性。
本文首先搭建了芯片的整体构架,采用了便携式应用的首选,电感式升压转换器来驱动白光LED,芯片采用了电流模式PWM控制方式,环境温度补偿技术,从而提高了芯片的快速性,可靠性,经济性和适用性。接下来,对芯片中的三个主要子模块——环境温度补偿电路、170mV比较器电路和欠压保护电路的设计进行了详细讨论,并利用HSPICE仿真工具结合UMC 0.6μm BCD工艺库对所设计电路进行了仿真验证。
最后,利用HSPICE仿真工具对芯片进行了全局仿真:芯片工作在1 MHz的频率下,最多能驱动7个LED,工作电流为25 mA,最高的转换效率可达到86%,低压下能利用欠压保护电路及时保护芯片,能够实现Analog和Direct-PWM亮度调节功能,仿真结果表明设计的芯片达到了预期的要求。
The white LED(Light Emitting Diode) is a welcome choice for illumination and backlighting in consumer electronics, but its allowable forward current is greatly affected by temperature. In traditional white LED driver design, its output current is determined by the maximum working temperature,comparatively small.
In this thesis, a novel white LED driver IC is proposed which can dynamically adjust the driver’s output current corresponding to the white LED’s current-temperature curve. Therefore the highest output current can be safely set over the entire operating temperature range, thereby allowing fewer LEDs to be used for normal display brightness which reduce the cost of application. Moreover, this circuit can protect LEDs from over-driving during high ambient temperatures, so it enhancing the chip’s reliability.
In the main part of this thesis, firstly, the whole chip’s structure is constructed. Using inductor step-up converter to drive White LED is a major method for portable applications. In the process of chip design, the current mode PWM control and ambient temperature compensation technology for increasing the chip's speed, reliability, economic and applicability. And then, the key interrelated technique for Boost DC/DC is studied and the whole chip structure is constructed. The main sub-circuits such as Ambient Temperature Compensation, 170mV Comparator and Under-Voltage Lockout Circuit are designed and implemented with UMC 0.6μm BCD process, and the simulation results are also presented.
Finally, HSPICE simulation results of the whole Chip are given: 1 MHz switching frequency. Up to 7 LEDs at 25 mA and the highest conversion efficiency of 86% can all be achieved. The chip can be timely protected by the under voltage protection function. Analog Direct-PWM and brightness adjustment functions can also be achieved. Simulation results show that the chip has achieved the expected demand.
引文
[1]王晓明,郭伟玲,高国等. LED——新一代照明光源.现代显示, 2005, 53(7): 15-19
[2]艾朝霞,姬妍. LED照明光源前景展望.榆林学院学报, 2006, 16(4): 40-42
[3]崔元日,潘苏予.第四代照明光源-白光LED.灯与照明, 2004, 28(2): 31-34
[4]刘行仁,薛胜薜,黄德森.白光LED现状和问题.光源与照明, 2003, 3: 4-8
[5]王海鸥.认识照明LED.中国照明电器, 2004, 2: 1-3
[6] Doug Varghn.白光LED驱动方案,电子产品世界, 2002, 6: 50-52
[7] Nichia Corporation. Specifications for Nichia Chip Type White LED Model: NSCW215T. http://www.nichia.com/cn/product/led-smd/NSCW215T.pdf
[8] Nadarajah Narendran, Yimin Gu. Life of LED-Based White Light Sources. IEEE/OSA Journal of Display Technology, 2005, 9(1): 167-171
[9]陈汉汛,倪尔东,刘利. LED驱动电路及在车用光源设计中的应用.武汉理工大学学报, 2005, 27(1): 67-69
[10]翁寿松.白色发光二极管及其驱动电路.电子元器件应用, 2004, 5(6): 15-17
[11] Falin Jeff. LCD显示屏的核心(WLED)供电.电子产品世界, 2004, 12: 140-142
[12] Michael. Day. LED Driver Considerations. http://focus.ti.com/lit/an/slyt084/ slyt084.pdf
[13] Texas Instrument. TPS61059 powers white-light LED as photoflash or movie light. http://focus.ti.com/lit/an/slyt245/slyt245.pdf
[14] Madhu Rayabhari. LED背光照明设计中的各种选择,电子产品世界, 2004, 1: 95-96
[15]平立.白光LED驱动综述,现代显示, 2006, 6: 44-48
[16]程江华,谢剑斌,丁文霞.白光LED电源驱动电路的设计与实现,电子技术, 2005, 8: 51-54
[17]吴富昌. LED与LED驱动器的搭配设计.国际照明与灯饰, 2006, 4
[18] National Semiconductor. Low Noise White LED Constant Current Supply with Dual Function Brightness Control. http://www.national.com/pf/LM/LM2793.html
[19] Maxim. MAX8630Y Charge Pumps for 5 White LEDs. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4722
[20] Linear. Ultra low Noise Charge Pump LED Supply with Output Current Adjust. http://www.linear.com.cn/pc/productDetail.jsp?navId=H0,C1,C1003,C1039,C1133,P2132
[21] Vatche Vorperian. Simplified Analysis of PWM Converters Using Model of PWM Switch Part1: Continuous Conduction Mode. IEEE Transactions on Aerospace and Electronic Systems, 1990, 26(3): 490-496
[22] Vatche Vorperian. New Constant-Frequency Current-Mode Control for Power Converters, Stable for All Values of Duty Ratio, and Usable in All Four Quadrants. IEEE Transactions on Industrial Electronics, 1990, 37(4): 323-325
[23]陆鸣.智能功率集成电路的核心技术——BCD集成工艺简述.见:华东地区第二届电源技术研讨会论文集.南京: 2002: 163-171
[24] Alan Hastings.模拟电路版图的艺术(影印本).北京:清华大学出版社, 2004: 417-420
[25]毕查德?拉扎维.模拟CMOS集成电路设计.陈贵灿,程军,张瑞智等译.西安:西安交通大学出版社, 2003. 319
[26] Paul R Gray, Paul J Hurst. Analysis and Design of Analog Integrated Circuits. Fourth Edition. 2004: 210-222
[27]赵春波,许伟,吴玉广.一种CMOS欠压保护电路的设计.集成电路与元器件,2004,10: 10-13
[28] Phillip E Allen, Douglas R Holberg. CMOS模拟集成电路设计.第二版.冯军,李智群译.北京:电子工业出版社, 2005. 379-380
[29] Paul L Brohlin, Allen. Supply independent low quiescent current undervoltage lockout Circuit. US Patent, US6842321B2, 2005
[30] Roberto Gariboldi, Acireale. Circuit for generating a reference voltage and detecting an under voltage of a supply and corresponding method. US Patent, US5747978,1998
[31] Taiyo Yuden. High Value Multilayer Ceramic Capacitors: JMK107BJ225MA-T.ht tp://www.yuden.co.jp/us/product/capacitor/JMK107BJ225MA-T.html, 2006
[32] Murata. Monolithic Ceramic Capacitors: GRM188R71H104K.http://www.murata. com/catalog/c02e.pdf#page=9, 2006, 3
[33] Murata. Monolithic Ceramic Capacitors: GRM155R71C104K.http://www.murata. com/catalog/c02e.pdf#page=9, 2006, 3
[34] Murata. Chip Coils for Choke Wire Wound Type LQH32C_53 Series(1210 Size). http://www.murata.com/catalog/o05e.pdf#page=66, 2006, 3
[35] Central Semiconductor Corp. CMOSH-4E Surface Mount Enhanced Specification Silicon Schottky Diode. http://www.centralsemi.com/pdf/CMOSH-4E.PDF, 2004, 3
[36] coilcraft. SPICE Model-ME3220. http://www.coilcraft.net/pdfs/spice_me-3220.pdf
[37] eCircuit Center. Capacitor Model. http://www.ecircuitcenter.com/Circuits/cmodel1/ cmodel1.htm
[38]钱恩学.高速PCB设计电容的应用. http://www.dz863.com/all-technology/EDA-PCB/ PCB-capacitances-2.htm
[39] TAIYO YUDEN. EMK212BJ105KD-T datasheet. http://www2.yuden.co.jp/hp/com/ main/php/ct_detail.php?lang=CS
[40] TAIYO YUDEN. EMK107BJ224KA-T datasheet. http://www2.yuden.co.jp/hp/com/ main/php/ct_detail.php?lang=CS
[41] microsemi. High Brightness White LED. www.microsemi.com/datasheets/upwledxx. pdf
[2]艾朝霞,姬妍. LED照明光源前景展望.榆林学院学报, 2006, 16(4): 40-42
[3]崔元日,潘苏予.第四代照明光源-白光LED.灯与照明, 2004, 28(2): 31-34
[4]刘行仁,薛胜薜,黄德森.白光LED现状和问题.光源与照明, 2003, 3: 4-8
[5]王海鸥.认识照明LED.中国照明电器, 2004, 2: 1-3
[6] Doug Varghn.白光LED驱动方案,电子产品世界, 2002, 6: 50-52
[7] Nichia Corporation. Specifications for Nichia Chip Type White LED Model: NSCW215T. http://www.nichia.com/cn/product/led-smd/NSCW215T.pdf
[8] Nadarajah Narendran, Yimin Gu. Life of LED-Based White Light Sources. IEEE/OSA Journal of Display Technology, 2005, 9(1): 167-171
[9]陈汉汛,倪尔东,刘利. LED驱动电路及在车用光源设计中的应用.武汉理工大学学报, 2005, 27(1): 67-69
[10]翁寿松.白色发光二极管及其驱动电路.电子元器件应用, 2004, 5(6): 15-17
[11] Falin Jeff. LCD显示屏的核心(WLED)供电.电子产品世界, 2004, 12: 140-142
[12] Michael. Day. LED Driver Considerations. http://focus.ti.com/lit/an/slyt084/ slyt084.pdf
[13] Texas Instrument. TPS61059 powers white-light LED as photoflash or movie light. http://focus.ti.com/lit/an/slyt245/slyt245.pdf
[14] Madhu Rayabhari. LED背光照明设计中的各种选择,电子产品世界, 2004, 1: 95-96
[15]平立.白光LED驱动综述,现代显示, 2006, 6: 44-48
[16]程江华,谢剑斌,丁文霞.白光LED电源驱动电路的设计与实现,电子技术, 2005, 8: 51-54
[17]吴富昌. LED与LED驱动器的搭配设计.国际照明与灯饰, 2006, 4
[18] National Semiconductor. Low Noise White LED Constant Current Supply with Dual Function Brightness Control. http://www.national.com/pf/LM/LM2793.html
[19] Maxim. MAX8630Y Charge Pumps for 5 White LEDs. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4722
[20] Linear. Ultra low Noise Charge Pump LED Supply with Output Current Adjust. http://www.linear.com.cn/pc/productDetail.jsp?navId=H0,C1,C1003,C1039,C1133,P2132
[21] Vatche Vorperian. Simplified Analysis of PWM Converters Using Model of PWM Switch Part1: Continuous Conduction Mode. IEEE Transactions on Aerospace and Electronic Systems, 1990, 26(3): 490-496
[22] Vatche Vorperian. New Constant-Frequency Current-Mode Control for Power Converters, Stable for All Values of Duty Ratio, and Usable in All Four Quadrants. IEEE Transactions on Industrial Electronics, 1990, 37(4): 323-325
[23]陆鸣.智能功率集成电路的核心技术——BCD集成工艺简述.见:华东地区第二届电源技术研讨会论文集.南京: 2002: 163-171
[24] Alan Hastings.模拟电路版图的艺术(影印本).北京:清华大学出版社, 2004: 417-420
[25]毕查德?拉扎维.模拟CMOS集成电路设计.陈贵灿,程军,张瑞智等译.西安:西安交通大学出版社, 2003. 319
[26] Paul R Gray, Paul J Hurst. Analysis and Design of Analog Integrated Circuits. Fourth Edition. 2004: 210-222
[27]赵春波,许伟,吴玉广.一种CMOS欠压保护电路的设计.集成电路与元器件,2004,10: 10-13
[28] Phillip E Allen, Douglas R Holberg. CMOS模拟集成电路设计.第二版.冯军,李智群译.北京:电子工业出版社, 2005. 379-380
[29] Paul L Brohlin, Allen. Supply independent low quiescent current undervoltage lockout Circuit. US Patent, US6842321B2, 2005
[30] Roberto Gariboldi, Acireale. Circuit for generating a reference voltage and detecting an under voltage of a supply and corresponding method. US Patent, US5747978,1998
[31] Taiyo Yuden. High Value Multilayer Ceramic Capacitors: JMK107BJ225MA-T.ht tp://www.yuden.co.jp/us/product/capacitor/JMK107BJ225MA-T.html, 2006
[32] Murata. Monolithic Ceramic Capacitors: GRM188R71H104K.http://www.murata. com/catalog/c02e.pdf#page=9, 2006, 3
[33] Murata. Monolithic Ceramic Capacitors: GRM155R71C104K.http://www.murata. com/catalog/c02e.pdf#page=9, 2006, 3
[34] Murata. Chip Coils for Choke Wire Wound Type LQH32C_53 Series(1210 Size). http://www.murata.com/catalog/o05e.pdf#page=66, 2006, 3
[35] Central Semiconductor Corp. CMOSH-4E Surface Mount Enhanced Specification Silicon Schottky Diode. http://www.centralsemi.com/pdf/CMOSH-4E.PDF, 2004, 3
[36] coilcraft. SPICE Model-ME3220. http://www.coilcraft.net/pdfs/spice_me-3220.pdf
[37] eCircuit Center. Capacitor Model. http://www.ecircuitcenter.com/Circuits/cmodel1/ cmodel1.htm
[38]钱恩学.高速PCB设计电容的应用. http://www.dz863.com/all-technology/EDA-PCB/ PCB-capacitances-2.htm
[39] TAIYO YUDEN. EMK212BJ105KD-T datasheet. http://www2.yuden.co.jp/hp/com/ main/php/ct_detail.php?lang=CS
[40] TAIYO YUDEN. EMK107BJ224KA-T datasheet. http://www2.yuden.co.jp/hp/com/ main/php/ct_detail.php?lang=CS
[41] microsemi. High Brightness White LED. www.microsemi.com/datasheets/upwledxx. pdf
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