Abstract:

The main circuit topology and technical requirements of current source used in proton therapy accelerator transport dipole magnet is presented. The requirements for the magnet power supply are that output current accuracy is less than 25ppm and the current ripple is less than 25ppm. The output current ripple of the power supply is composed of low and high frequency components. The formation mechanism of the output current ripple is analyzed and computed in detail. It is obtained that Pulse Width Modulation (PWM) current tracking control based on the impulse control principle can effectively eliminate the influence of low frequency ripple on the output current. Meanwhile, two methods are used for quantitative mathematical analysis of the high frequency ripple. The quantitative conclusions and formulas of computation are achieved. With the help of AnsoftSimplorer power electronic simulation software, the correctness of the conclusions and formulas is verified. Corresponding strategies for ripple suppression are proposed.

Key words: Magnet coils power supply, Current ripple, PWM control, Impulse control

摘要：

介绍了质子治疗加速器输运部二极磁铁电流源的技术要求、主电路拓扑。该电源要求输出电流精度为25ppm，纹波小于25ppm。电源输出电流纹波由低频纹波和高频纹波组成。对电源输出电流纹波的形成机理进行了详细的理论分析和数学计算。得出了基于冲量控制原理的脉冲宽度调制(PWM)电流跟踪控制技术可以有效消除输入低频纹波对输出电流的影响。同时也对输出电流高频纹波采用两种方法进行了定量的数学分析，并得出量化的结论和计算公式。借助AnsoftSimplorer电路仿真软件构建模型，验证了纹波规律结论及计算公式的准确性，并且提出了相应的纹波抑制策略。

关键词: 磁体电源, 电流纹波, PWM控制, 冲量原理