Development Of CT's High Voltage Generator Filament Driving Power Supply

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.