高效电荷泵DC_DC白光LED驱动芯片的设计
摘要
随着便携式电子产品的广泛应用，电源管理芯片日趋显现出其在电子产品中的重要地位。高效率、低成本和低噪声已经成为了便携式设备中电源管理芯片的发展方向。而近年来白光LED驱动芯片一直是电源管理芯片市场的热点。其中，电荷泵电路由于不需要电感元件就可以完成升压功能而备受关注。
本文设计了一种高效电荷泵DC_DC白光LED驱动芯片。它是基于高效自适应电荷泵电路，在0.5微米CMOS工艺条件下设计完成的。其输入电压范围为2.7V～5.5V，输出电压恒定为5V，可提供高达100mA的负载电流。在关断状态下，关断电流小于1μA。工作频率为固定的1MHz，芯片外部只需要接4个容值较小的陶瓷电容，大幅降低了EMI辐射干扰和芯片的应用成本。芯片正常工作温度为-40℃～85℃，内部集成了欠压锁定和过热保护功能。此外，该芯片还具有软启动功能，能够限制启动时的涌浪电流。
本文首先介绍了芯片的整体结构，给出了芯片的内部结构框图，并根据电荷泵的基本原理和拓扑结构，设计了芯片的核心模块1.5x／2x自适应电荷泵电路，它可随输入电压的变化而改变升压倍数。然后又对电荷泵的几个重要的参数进行了详细地分析，介绍了各个子电路模块的设计，包括偏置电路、带隙基准、振荡器、电荷泵逻辑控制电路、误差放大器、过热保护电路等等。
在完成电路原理分析与电路设计的基础之上，还应用EDA软件Hspice对各个模块和整体电路进行了仿真，仿真结果均达到了预期的设计目标，验证了理论分析和电路设计的正确性。最后给出了部分模块版图的设计。
Power management IC becomes more and more important due to popularizatization of portable equipments. High efficiency, low cost and low noise are becoming the development trend of DCDC regulations. White LED driver has been chief market for power manager IC these years. And charge pump converters become more attractive, because the tructure of charge pump can perform the conversion of rising input voltage without use of inductor.
By using a 0.5μm CMOS process, a high efficiency charge pump DCDC white LED driver is designed in this paper, which based on an auto-adjust capacitor charge pump. It produces a regulated output voltage 5v from a 2.7v to 5.5v input with up to 100mA of output current. Its shutdown supply current is lower than 1μA when chip is in the shutdown mode. The switching frequency is 1MHz. High switching frequency enables the use of small ceramic capacitors, so it can reduce disturbtion of EMI and the cost. Its operating temperature is -40°C to 85°C. The chip implements a thermal shutdown mechanism to protect the device from damage due to overheating and an under voltage lock out mechanism when the input voltage is too low. A tightly controlled soft start feature limits inrush currents during the chip activation.
Frist, the system design and its block diagram is introduced. 1.5x/2x auto-adjust charge pump is design according to the principle and structure of charge pump, which can automatically convert working mode with the change of input voltage. Then, important parameter of charge pump is analyzed in details. The sub-circuits are discussing, including of bias, band gap, oscillator, logic control, error amplifier a, over thermal protect, etc.
Based on the principle analysis and circuit design, the system and its sub-circuits are simulated by EDA tools HSPICE, the simulation results reach the requests and verified the correctnesss of the principle analysis and circuit design. Some layouts of sub-circuits are designed at last.
本文设计了一种高效电荷泵DC_DC白光LED驱动芯片。它是基于高效自适应电荷泵电路，在0.5微米CMOS工艺条件下设计完成的。其输入电压范围为2.7V～5.5V，输出电压恒定为5V，可提供高达100mA的负载电流。在关断状态下，关断电流小于1μA。工作频率为固定的1MHz，芯片外部只需要接4个容值较小的陶瓷电容，大幅降低了EMI辐射干扰和芯片的应用成本。芯片正常工作温度为-40℃～85℃，内部集成了欠压锁定和过热保护功能。此外，该芯片还具有软启动功能，能够限制启动时的涌浪电流。
本文首先介绍了芯片的整体结构，给出了芯片的内部结构框图，并根据电荷泵的基本原理和拓扑结构，设计了芯片的核心模块1.5x／2x自适应电荷泵电路，它可随输入电压的变化而改变升压倍数。然后又对电荷泵的几个重要的参数进行了详细地分析，介绍了各个子电路模块的设计，包括偏置电路、带隙基准、振荡器、电荷泵逻辑控制电路、误差放大器、过热保护电路等等。
在完成电路原理分析与电路设计的基础之上，还应用EDA软件Hspice对各个模块和整体电路进行了仿真，仿真结果均达到了预期的设计目标，验证了理论分析和电路设计的正确性。最后给出了部分模块版图的设计。
Power management IC becomes more and more important due to popularizatization of portable equipments. High efficiency, low cost and low noise are becoming the development trend of DCDC regulations. White LED driver has been chief market for power manager IC these years. And charge pump converters become more attractive, because the tructure of charge pump can perform the conversion of rising input voltage without use of inductor.
By using a 0.5μm CMOS process, a high efficiency charge pump DCDC white LED driver is designed in this paper, which based on an auto-adjust capacitor charge pump. It produces a regulated output voltage 5v from a 2.7v to 5.5v input with up to 100mA of output current. Its shutdown supply current is lower than 1μA when chip is in the shutdown mode. The switching frequency is 1MHz. High switching frequency enables the use of small ceramic capacitors, so it can reduce disturbtion of EMI and the cost. Its operating temperature is -40°C to 85°C. The chip implements a thermal shutdown mechanism to protect the device from damage due to overheating and an under voltage lock out mechanism when the input voltage is too low. A tightly controlled soft start feature limits inrush currents during the chip activation.
Frist, the system design and its block diagram is introduced. 1.5x/2x auto-adjust charge pump is design according to the principle and structure of charge pump, which can automatically convert working mode with the change of input voltage. Then, important parameter of charge pump is analyzed in details. The sub-circuits are discussing, including of bias, band gap, oscillator, logic control, error amplifier a, over thermal protect, etc.
Based on the principle analysis and circuit design, the system and its sub-circuits are simulated by EDA tools HSPICE, the simulation results reach the requests and verified the correctnesss of the principle analysis and circuit design. Some layouts of sub-circuits are designed at last.
引文
[1]周志敏，周纪海，纪爱华．LED驱动电路设计与应用．北京：人民邮电出版社，2006．
[2]方佩敏．如何选择便携式产品电源IC．今日电子，2000，(05)：25-27．
[3]Dario Nurzad．利用电荷泵驱动器优化百光LED背光应用效率．电子设计，2006．
[4]Ping Luo，Luyang Luo，Zhao Li，Chen Guangju．Skip Cycle Modulation in Switching DC-DC Converter．ICCCAS．Chengdu．2002：1716-1719．
[5]JOHN F DICKSON．On chip High—Voltage Generation in MNOS Integrated Circuits Using an Improved voltage Multiplier Technique．IEEE Journal of Solid-State Circuits，1976，11(5)：374-378．
[6]曹香凝，汪东旭，严利民．DC-DC电荷泵的研究与设计．通信电源技术．2004，21(5)：14-16．
[7]D.D. Cataldo, G. Palmubo. Double and Triple Charge Pump for Power IC: Dynamic Models,which take parasitic Effects into Account. IEEE Transaction on Circuits and Systems,1993,40(2):92-100.
[8]Harms Chiu. A Useful Model for Charge Pump Converter. Analog Integrations Corporation Application Note, http://www.analog. com. tw.
[9]Oliver Nachbaur. White LED power supply techniques: charge pump and boost converter,Texas Instruments, 2003.
[10]Erich Bayer, Hans Schmeller. Charge pump with active cycle regulation-closing the Gap between Linear-and Skip modes. IEEE Power Electronics Specialists Conference, 2000,18(3):1497-1502.
[11]景卫兵，王宇华，张波．基于电荷泵高效LED驱动电路研究．中国集成电路，2005，63(8)：27-30．
[12]C C Wang, J C Wu. Efficiency Improvement in Charge Pump Circuits. IEEE Journal of Solid-State Circuits, 1997,32(6):852-860.
[13]Erich Bayer, Hans Schmeller. Charge pump with active cycle regulation-closing the gap between linear and skip modes. IEEE Power Electronics Specialists Conference, 2000,3(6):149-1502.
[14]J. Liu, Z Chen. A New Design of Power Supplies for Pocket Computer Systems. IEEE Transaction on industrial Electronics, 1998,45(2):228-235.
[15]熊富贵，罗萍，李肇基等．PSM调制电荷泵电路．微电子学，2004，34(2)：125-127．
[16]Behzad Razavi.Design of analog CMOS integrated circuits. 西安：西安交通大学出版社，2003.
[17]Paul R. Gray, Paul J. Hurst, Stephen H. Lewis, et al.模拟集成电路的分析与设计．北京：高等教育出版社，2005.
[18]Nicollini G, Senderowicz D. A CMOS bandgap reference for differential signal processing.IEEE J Sol Sta Circ, 1991,26(1):41-50.
[19]Phillip E. Allen, Douglas R. llolberg. CMOS模拟集成电路设计．北京：电子工业出版社，2005
[20] Pease R. The design of band-gap reference circuits:trials and tribulations. IEEE 1990 Bipolar Circuits and Technology Meeting[C],1990:214-218.
[21] Banba H, Shiga H, Umezawa A, et al. A CMOS bandgap reference circuit with sub-1-V operation. IEEE J Solid-Satate Circuits, 1999,34(5):670-671.
[22] 徐勇，王志功，关宇，等．一种高精度带隙电压基准源改进设计．半导体学报，2006，27(12)：2209－2213．
[23] Boni A. Op-amps and startup circuits for CMOS bandgap references with near l-V supply. IEEE J Solid-State Circuits, 2002,37(10):1339.
[24] 朱樟明，杨银堂，刘帘曦，等．一种高性能CMOS带隙电压基准源设计．半导体学报，2004，25：542-546．
[25] 江金光，王耀南．高精度带隙基准电压源的实现．半导体学报，2004，25[7]：852．
[26] 汪东旭，孙艺．一种频率稳定的改进型CMOS环形振荡器．微电子学，1999，29(5)：370－373．
[27] 赵胜华，陈建安．CMOS集成电路中振荡器的设计及性能分析．电子与封装，2004，4(6)：33-36．
[28] Sung-Mo Kang,Yusuf Leblebici.CMOS数字集成电路设计与分析．北京：电子工业出版社，2005．
[29] B. Roert Gregoire. A Compact Switched-Capacitor Regulated Charge pump Power Supply. IEEE Journal of Solid-State Circuits, 2006,41(8):1994-1953.
[30] 石伟韬，蒋国平．一种高稳定低功耗CMOS过热保护电路的设计．电子器件，2006，29(2)：330．
[31] Nagel M H, Fonderie M J,Meijer G GM,et al. Integrated lV thermal shutdown circuit. IEEE, Electronics Letters, 1992,28(lO):969-970.
[2]方佩敏．如何选择便携式产品电源IC．今日电子，2000，(05)：25-27．
[3]Dario Nurzad．利用电荷泵驱动器优化百光LED背光应用效率．电子设计，2006．
[4]Ping Luo，Luyang Luo，Zhao Li，Chen Guangju．Skip Cycle Modulation in Switching DC-DC Converter．ICCCAS．Chengdu．2002：1716-1719．
[5]JOHN F DICKSON．On chip High—Voltage Generation in MNOS Integrated Circuits Using an Improved voltage Multiplier Technique．IEEE Journal of Solid-State Circuits，1976，11(5)：374-378．
[6]曹香凝，汪东旭，严利民．DC-DC电荷泵的研究与设计．通信电源技术．2004，21(5)：14-16．
[7]D.D. Cataldo, G. Palmubo. Double and Triple Charge Pump for Power IC: Dynamic Models,which take parasitic Effects into Account. IEEE Transaction on Circuits and Systems,1993,40(2):92-100.
[8]Harms Chiu. A Useful Model for Charge Pump Converter. Analog Integrations Corporation Application Note, http://www.analog. com. tw.
[9]Oliver Nachbaur. White LED power supply techniques: charge pump and boost converter,Texas Instruments, 2003.
[10]Erich Bayer, Hans Schmeller. Charge pump with active cycle regulation-closing the Gap between Linear-and Skip modes. IEEE Power Electronics Specialists Conference, 2000,18(3):1497-1502.
[11]景卫兵，王宇华，张波．基于电荷泵高效LED驱动电路研究．中国集成电路，2005，63(8)：27-30．
[12]C C Wang, J C Wu. Efficiency Improvement in Charge Pump Circuits. IEEE Journal of Solid-State Circuits, 1997,32(6):852-860.
[13]Erich Bayer, Hans Schmeller. Charge pump with active cycle regulation-closing the gap between linear and skip modes. IEEE Power Electronics Specialists Conference, 2000,3(6):149-1502.
[14]J. Liu, Z Chen. A New Design of Power Supplies for Pocket Computer Systems. IEEE Transaction on industrial Electronics, 1998,45(2):228-235.
[15]熊富贵，罗萍，李肇基等．PSM调制电荷泵电路．微电子学，2004，34(2)：125-127．
[16]Behzad Razavi.Design of analog CMOS integrated circuits. 西安：西安交通大学出版社，2003.
[17]Paul R. Gray, Paul J. Hurst, Stephen H. Lewis, et al.模拟集成电路的分析与设计．北京：高等教育出版社，2005.
[18]Nicollini G, Senderowicz D. A CMOS bandgap reference for differential signal processing.IEEE J Sol Sta Circ, 1991,26(1):41-50.
[19]Phillip E. Allen, Douglas R. llolberg. CMOS模拟集成电路设计．北京：电子工业出版社，2005
[20] Pease R. The design of band-gap reference circuits:trials and tribulations. IEEE 1990 Bipolar Circuits and Technology Meeting[C],1990:214-218.
[21] Banba H, Shiga H, Umezawa A, et al. A CMOS bandgap reference circuit with sub-1-V operation. IEEE J Solid-Satate Circuits, 1999,34(5):670-671.
[22] 徐勇，王志功，关宇，等．一种高精度带隙电压基准源改进设计．半导体学报，2006，27(12)：2209－2213．
[23] Boni A. Op-amps and startup circuits for CMOS bandgap references with near l-V supply. IEEE J Solid-State Circuits, 2002,37(10):1339.
[24] 朱樟明，杨银堂，刘帘曦，等．一种高性能CMOS带隙电压基准源设计．半导体学报，2004，25：542-546．
[25] 江金光，王耀南．高精度带隙基准电压源的实现．半导体学报，2004，25[7]：852．
[26] 汪东旭，孙艺．一种频率稳定的改进型CMOS环形振荡器．微电子学，1999，29(5)：370－373．
[27] 赵胜华，陈建安．CMOS集成电路中振荡器的设计及性能分析．电子与封装，2004，4(6)：33-36．
[28] Sung-Mo Kang,Yusuf Leblebici.CMOS数字集成电路设计与分析．北京：电子工业出版社，2005．
[29] B. Roert Gregoire. A Compact Switched-Capacitor Regulated Charge pump Power Supply. IEEE Journal of Solid-State Circuits, 2006,41(8):1994-1953.
[30] 石伟韬，蒋国平．一种高稳定低功耗CMOS过热保护电路的设计．电子器件，2006，29(2)：330．
[31] Nagel M H, Fonderie M J,Meijer G GM,et al. Integrated lV thermal shutdown circuit. IEEE, Electronics Letters, 1992,28(lO):969-970.