CT机高压发生器灯丝驱动电源的研制
摘要
高压发生器是CT机的重要组成部分,其性能好坏直接影响CT图象质量。本文以CT机高压发生器灯丝驱动电源为主要研究对象,重点研究并设计灯丝驱动电源。为了适应新型CT检测方式多样化要求,在“国家数字化医疗影像设备工程技术研究中心”的资助下,开展本研究,设计了一个可以实时变mA、自校准的灯丝驱动电源。
以PWM结构为基本拓扑,设计了一个能实行电流调节的灯丝驱动电源。首先针对新型CT高压发生器中灯丝驱动电源的功能、安规、电磁兼容性等方面的要求,提出采用与主逆变器相同的供电方式：380V交流电整流后的直流供电：其次在对灯丝驱动电源调功方案分析的基础上,提出了谐振式和PWM型两种可行的解决方案,通过对比,采用PWM型拓扑对灯丝驱动电源进行设计,在此基础上设计了半桥单相式缓冲型软PWM电路,并对其工作过程进行计算仿真,得出此结构可以减少开关损耗；最后设计了一个闭环反馈控制电路,引入了PI调节器以及误差补偿,根据灯丝电流设定与反馈值实时校准灯丝电流。
以UC3525为核心调节器,构建了包括多个功能模块的高性能灯丝驱动电源,把开关工作频率稳定在40KHz。设计了可选择输入的灯丝调准电路,可在高压发生器曝光与未曝光两种条件下工作；通过磁耦的方式组建了MOSFET的驱动电路,在开关频率不是非常高的状况下能有效驱动MOSFET,降低驱动电路复杂度。为了稳定灯丝电流,保证曝光时的mA稳定,通过电流互感器检测电流,经过调整后与设定电流进行比较,经调整后的误差直接送到UC3525的内部比较器里,以此来控制驱动脉冲占空比,做到了灯丝电流稳定输出。另外在电路设计过程中,充分考虑了电源保护这个问题,采用瞬态抑制、浪涌抑制和熔丝相结合的方法保护电路,并把反馈电流信息通过接口上传给主控制系统进行处理。
经测试,此设计样机能达灯丝电流反馈值与预设值趋于一致,最大误差为3.2%,最小达到了0.2%,可以满足灯丝加热需求。
Generator is an essential part of the CT. Its performance impacts the image of CT directly. This paper is based on High Voltage Generator, focuses on the filament driving power supply. This research is carried out to meet the requirements of diverse detection methods of CT. It is funded by National Digital Medical Imaging Equipment and Engineer Technology Research Center, and design a real-time and self-adjusting filament driving power supply.
Taking PWM as the base method, this thesis constructs a filament driving power supply which can adjust filament's current. Firstly, based on the requirements of function, Safety rules and EMC, adopt the direct current formed by rectifying 380VAC, the same method to the main inverter. Secondly, analyse the structure resonance and PWM, adopt PWM as the method and design half bridge single-phase buff soft-switch circuit, simulate its the course,and it can reduce the power loss.Fanally,design a close loop control circuit,adding PI adjuster and error compensator, adjust filament feedback current according to the set current.
Taking UC3525 as the main adjuster, a hign performance power supply which contains a variety of modules is designed. The frequency of switch is setted to 40KHz. Design a filament current setting circuit including two choices, It can meet the requirements of the High Generator when it's exposed or unexposed. Design a magnetically coupled circuit to drive power mosfet, which can work efficiently when the frequency is not too high, and reduce the complexity, guarantee the value of mA when exposing, compare the set current with the feedback current detected by current transformer, the error is adjusted and sent to the inner comparator of UC3525 to control pulse width and make the filament current stay steady state. Beside these, considering the power supply protection, adopt transient voltage suppressor, surge suppressor and fuse to protect the circuit, and the feedback current is sent to the main control system to deal through interface. It's measured that the greatest error of the filament current is 3.2%, the least reaches 0.2%, the feedback current is compatible with the set current, which satisfies the requirement.
以PWM结构为基本拓扑,设计了一个能实行电流调节的灯丝驱动电源。首先针对新型CT高压发生器中灯丝驱动电源的功能、安规、电磁兼容性等方面的要求,提出采用与主逆变器相同的供电方式：380V交流电整流后的直流供电：其次在对灯丝驱动电源调功方案分析的基础上,提出了谐振式和PWM型两种可行的解决方案,通过对比,采用PWM型拓扑对灯丝驱动电源进行设计,在此基础上设计了半桥单相式缓冲型软PWM电路,并对其工作过程进行计算仿真,得出此结构可以减少开关损耗；最后设计了一个闭环反馈控制电路,引入了PI调节器以及误差补偿,根据灯丝电流设定与反馈值实时校准灯丝电流。
以UC3525为核心调节器,构建了包括多个功能模块的高性能灯丝驱动电源,把开关工作频率稳定在40KHz。设计了可选择输入的灯丝调准电路,可在高压发生器曝光与未曝光两种条件下工作；通过磁耦的方式组建了MOSFET的驱动电路,在开关频率不是非常高的状况下能有效驱动MOSFET,降低驱动电路复杂度。为了稳定灯丝电流,保证曝光时的mA稳定,通过电流互感器检测电流,经过调整后与设定电流进行比较,经调整后的误差直接送到UC3525的内部比较器里,以此来控制驱动脉冲占空比,做到了灯丝电流稳定输出。另外在电路设计过程中,充分考虑了电源保护这个问题,采用瞬态抑制、浪涌抑制和熔丝相结合的方法保护电路,并把反馈电流信息通过接口上传给主控制系统进行处理。
经测试,此设计样机能达灯丝电流反馈值与预设值趋于一致,最大误差为3.2%,最小达到了0.2%,可以满足灯丝加热需求。
Generator is an essential part of the CT. Its performance impacts the image of CT directly. This paper is based on High Voltage Generator, focuses on the filament driving power supply. This research is carried out to meet the requirements of diverse detection methods of CT. It is funded by National Digital Medical Imaging Equipment and Engineer Technology Research Center, and design a real-time and self-adjusting filament driving power supply.
Taking PWM as the base method, this thesis constructs a filament driving power supply which can adjust filament's current. Firstly, based on the requirements of function, Safety rules and EMC, adopt the direct current formed by rectifying 380VAC, the same method to the main inverter. Secondly, analyse the structure resonance and PWM, adopt PWM as the method and design half bridge single-phase buff soft-switch circuit, simulate its the course,and it can reduce the power loss.Fanally,design a close loop control circuit,adding PI adjuster and error compensator, adjust filament feedback current according to the set current.
Taking UC3525 as the main adjuster, a hign performance power supply which contains a variety of modules is designed. The frequency of switch is setted to 40KHz. Design a filament current setting circuit including two choices, It can meet the requirements of the High Generator when it's exposed or unexposed. Design a magnetically coupled circuit to drive power mosfet, which can work efficiently when the frequency is not too high, and reduce the complexity, guarantee the value of mA when exposing, compare the set current with the feedback current detected by current transformer, the error is adjusted and sent to the inner comparator of UC3525 to control pulse width and make the filament current stay steady state. Beside these, considering the power supply protection, adopt transient voltage suppressor, surge suppressor and fuse to protect the circuit, and the feedback current is sent to the main control system to deal through interface. It's measured that the greatest error of the filament current is 3.2%, the least reaches 0.2%, the feedback current is compatible with the set current, which satisfies the requirement.
引文
1.王鸣鹏.CT检查技术学[M],上海：复旦大学出版社,2004,6-7.
2.余晓锷,卢广文.CT设备原理、结构与质量保证[M],北京：科学出版社,2005,1-6.
3.柳橙,秦维昌.多层螺旋CT的技术改进[J],医学研究通讯,2004,33(11)：2-3.
4.王学明,沈克涵.医学成像系统[M],北京：清华大学出版社,2006,158-163.
5.张君秋.多层CT机DAS系统数据预处理模块的研制[D],沈阳：东北大学,2008.
6.吴维荣.CT机高压发生器控制系统设计与实现[D],沈阳：东北大学,2006.
7.张翔.电磁感应加热技术安全性设计与研究[D],西安：西北工业大学,2007.
8.方清城,李先详.高频开关电源的EMC设计[J],现代电子技术,2009,32(8)：170-172.
9.王延华.浅谈电磁兼容性设计与测量[C],中国电子学会可靠性分会第十二届学术年会,2004：299-304.
10. Colotti J. EMC Design Fundamentals Systems[C], IEEE Applications and Technology Conference,2006:1-2.
11. Luan J E, Tee T Y. Analysis of PCB Subassembly Dynamic Responses using Integrated Analytical, Numerical and Experimental Techniques[C], IEEE Electronic Packaging Technology,2005(6):133-140.
12.吕宏.PWM&PFM控制感应加热技术研究[D],杭州：浙江大学,2003.
13. Belaguli V, Bhat A K S. Series-Parallel Resonant Converter Operating in Discontinuous Current Mode—Analysis, Design, Simulation, and Experimental Results [J], IEEE Circuits and system-Ⅰ:Fundamental theory and applications,2000,47(4):433-488.
14.周伟成,马皓,张海军.半桥LLC谐振变换器效率优化方案的研究[J],电力电子技术,2007,41(9)：57-59.
15.任先进,马瑞卿.PWM型半桥式开关稳压电源的设计[J],计测技术,2006,26(05)：21-23.
16.王伟,徐申,吴建辉.非对称半桥式开关电源的分析与设计[J],通讯电源技术,2008,25(04)：42-47.
17.张占松,蔡宣三.开关电源的原理与设计[M],北京：电子工业出版社,2004：301-305.
18.秦岭,张航,王亚芳.基于新型箝位电路的低电压应力零电流开关半桥PWM变换器[J],中国电机工程学报,2008,28(24)：25-30.
19. Chen R G, Strydom J T, VanWyk J D. Design of Planar Integrated Passive Module for Zero-Voltage Switched Asymmetrical Half Bridge PWM Converter[C], IEEE Industry Applications Conference,2001,4:2232-2237.
20.林渭勋.现代电力电子技术[M],北京：机械工业出版社,2006,350-352.
21.胡寿松.自动控制理论[M],北京：科学出版社,2003,3-10.
22.王志强.现代开关电源[M],北京：电子工业出版社,2006,296-302.
23.张芬,来新泉,赵涛.电压模控制中的两种频率补偿方法[J],电子元器件运用,2009,11(1)：73-76.
24.赵听,王德强,韩崇伟.基于SG1525的全桥变换器设计[J],火炮发射与控制学报,2007,02：10-13.
25. Ye Z M, Jain P K, Sen P C. A Full-Bridge Resonant Inverter With Modified Phase-Shift Modulation for High-Frequency AC Power Distribution Systems[J], IEEE Transactions On Industrial Electronics,2007,54(5):2831-2844.
26. Ye Z M, Praveen J, Paresh S. Control of High Frequency Resonant Inverter System, Design and Implementation[C], IEEE Power Electronics Specialists Conference,2006:1-7.
27. Shih F Y, Chen Y T, Chen D Y. A PSpice-compatible model of PWM IC for switching power converters with soft-start characteristic[C], IEEE Power Electronics and Drive Systems Proceedings of 1995 International Conference 1995,1:335-340.
28.Zhu J Y, Lehman B. Control loop design for two-stage DC-DC converters with low voltage/high current output [J], IEEE Power Electronics,2005,20(1); 44-55.
29. Ridly R. Current mode or voltage mode[J], Switching Power Magazine,2000,10:4-5.
30.魏保权.高频逆变式弧焊机电源的设计[D],武汉：武汉理工大学,2007.
31.沈坚,钱猛,杨长玲.400KV高压脉冲变压器的设计与仿真[J],现代雷达,2008,30(12)：89-91.
32. Akemoto M, Gold S, Krasnykh A, et al. Pulse transformer R&D for NLC klystron pulse modulator[C], IEEE Pulsed Power Conference Digest of Technical Papers,1997,1(3): 724-729.
33.钟静宏,张承宁.基于脉冲电源的MOSFET驱动电路研究与应用[J],航空精密制造技术,2006,42(3)：57-62.
2.余晓锷,卢广文.CT设备原理、结构与质量保证[M],北京：科学出版社,2005,1-6.
3.柳橙,秦维昌.多层螺旋CT的技术改进[J],医学研究通讯,2004,33(11)：2-3.
4.王学明,沈克涵.医学成像系统[M],北京：清华大学出版社,2006,158-163.
5.张君秋.多层CT机DAS系统数据预处理模块的研制[D],沈阳：东北大学,2008.
6.吴维荣.CT机高压发生器控制系统设计与实现[D],沈阳：东北大学,2006.
7.张翔.电磁感应加热技术安全性设计与研究[D],西安：西北工业大学,2007.
8.方清城,李先详.高频开关电源的EMC设计[J],现代电子技术,2009,32(8)：170-172.
9.王延华.浅谈电磁兼容性设计与测量[C],中国电子学会可靠性分会第十二届学术年会,2004：299-304.
10. Colotti J. EMC Design Fundamentals Systems[C], IEEE Applications and Technology Conference,2006:1-2.
11. Luan J E, Tee T Y. Analysis of PCB Subassembly Dynamic Responses using Integrated Analytical, Numerical and Experimental Techniques[C], IEEE Electronic Packaging Technology,2005(6):133-140.
12.吕宏.PWM&PFM控制感应加热技术研究[D],杭州：浙江大学,2003.
13. Belaguli V, Bhat A K S. Series-Parallel Resonant Converter Operating in Discontinuous Current Mode—Analysis, Design, Simulation, and Experimental Results [J], IEEE Circuits and system-Ⅰ:Fundamental theory and applications,2000,47(4):433-488.
14.周伟成,马皓,张海军.半桥LLC谐振变换器效率优化方案的研究[J],电力电子技术,2007,41(9)：57-59.
15.任先进,马瑞卿.PWM型半桥式开关稳压电源的设计[J],计测技术,2006,26(05)：21-23.
16.王伟,徐申,吴建辉.非对称半桥式开关电源的分析与设计[J],通讯电源技术,2008,25(04)：42-47.
17.张占松,蔡宣三.开关电源的原理与设计[M],北京：电子工业出版社,2004：301-305.
18.秦岭,张航,王亚芳.基于新型箝位电路的低电压应力零电流开关半桥PWM变换器[J],中国电机工程学报,2008,28(24)：25-30.
19. Chen R G, Strydom J T, VanWyk J D. Design of Planar Integrated Passive Module for Zero-Voltage Switched Asymmetrical Half Bridge PWM Converter[C], IEEE Industry Applications Conference,2001,4:2232-2237.
20.林渭勋.现代电力电子技术[M],北京：机械工业出版社,2006,350-352.
21.胡寿松.自动控制理论[M],北京：科学出版社,2003,3-10.
22.王志强.现代开关电源[M],北京：电子工业出版社,2006,296-302.
23.张芬,来新泉,赵涛.电压模控制中的两种频率补偿方法[J],电子元器件运用,2009,11(1)：73-76.
24.赵听,王德强,韩崇伟.基于SG1525的全桥变换器设计[J],火炮发射与控制学报,2007,02：10-13.
25. Ye Z M, Jain P K, Sen P C. A Full-Bridge Resonant Inverter With Modified Phase-Shift Modulation for High-Frequency AC Power Distribution Systems[J], IEEE Transactions On Industrial Electronics,2007,54(5):2831-2844.
26. Ye Z M, Praveen J, Paresh S. Control of High Frequency Resonant Inverter System, Design and Implementation[C], IEEE Power Electronics Specialists Conference,2006:1-7.
27. Shih F Y, Chen Y T, Chen D Y. A PSpice-compatible model of PWM IC for switching power converters with soft-start characteristic[C], IEEE Power Electronics and Drive Systems Proceedings of 1995 International Conference 1995,1:335-340.
28.Zhu J Y, Lehman B. Control loop design for two-stage DC-DC converters with low voltage/high current output [J], IEEE Power Electronics,2005,20(1); 44-55.
29. Ridly R. Current mode or voltage mode[J], Switching Power Magazine,2000,10:4-5.
30.魏保权.高频逆变式弧焊机电源的设计[D],武汉：武汉理工大学,2007.
31.沈坚,钱猛,杨长玲.400KV高压脉冲变压器的设计与仿真[J],现代雷达,2008,30(12)：89-91.
32. Akemoto M, Gold S, Krasnykh A, et al. Pulse transformer R&D for NLC klystron pulse modulator[C], IEEE Pulsed Power Conference Digest of Technical Papers,1997,1(3): 724-729.
33.钟静宏,张承宁.基于脉冲电源的MOSFET驱动电路研究与应用[J],航空精密制造技术,2006,42(3)：57-62.