【作者】 曾海青；

【导师】 邹豪；

【作者基本信息】 东北大学 ， 生物医学工程， 2009， 硕士

【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。更多还原

【Abstract】 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.更多还原