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    Optimal phase-shifted control for a series resonant converter
    1.
    发明授权
    Optimal phase-shifted control for a series resonant converter 有权
    串联谐振变换器的最优相移控制

    公开(公告)号：US06178099B1

    公开(公告)日：2001-01-23

    申请号：US09545449

    申请日：2000-04-07

    申请人： Michael Joseph Schutten ,  Vlatko Vlatkovic ,  William Frederick Wirth

    发明人： Michael Joseph Schutten ,  Vlatko Vlatkovic ,  William Frederick Wirth

    IPC分类号： H02M3337

    CPC分类号： H02M3/3376 ,  H02M2001/0058 ,  H02M2007/53878 ,  Y02B70/1433 ,  Y02B70/1441 ,  Y02B70/1491

    摘要： An optimal phase-shifted control for a series resonant converter involves instantaneous monitoring of state variables (resonant capacitor voltage resonant inductor current and output voltage) and implementation of a control law for providing a quasi-squarewave-with-maximum-coasting (QSWMC) mode of operation. The control law uses the instantaneous resonant inductor current, the instantaneous resonant capacitor voltage and the output voltage to determine the optimal time to perform switching events in order to operate on a desired control trajectory. The QSWMC converter operates at a minimized frequency in a super-resonant mode with zero-voltage switching, minimized electrical stresses, and reduced electromagnetic interference due to nearly sinusoidal resonant tank currents.

    摘要翻译： 用于串联谐振转换器的最佳相移控制包括对状态变量（谐振电容器电压谐振电感器电流和输出电压）的瞬时监测以及用于提供准方波最大惯性（QSWMC）模式的控制律的实现 的操作。 控制律使用瞬时谐振电感电流，瞬时谐振电容电压和输出电压来确定执行切换事件的最佳时间，以便在所需的控制轨迹上运行。 QSWMC转换器在具有零电压开关，最小化电应力的超谐振模式中以最小频率工作，并且由于几乎正弦谐振槽电流而导致的电磁干扰减小。

    Switching gradient amplifier with adjustable DC bus voltage
    2.
    发明授权
    Switching gradient amplifier with adjustable DC bus voltage 失效
    具有可调直流母线电压的开关梯度放大器

    公开(公告)号：US5663647A

    公开(公告)日：1997-09-02

    申请号：US581282

    申请日：1995-12-29

    申请人： William Frederick Wirth ,  John N. Park

    发明人： William Frederick Wirth ,  John N. Park

    IPC分类号： A61B5/055 ,  G01R33/385 ,  G01R33/38

    CPC分类号： G01R33/3852

    摘要： An amplification device is provided for driving a gradient coil in an MR system, wherein the gradient coil is required to generate a rapidly changing gradient magnetic field during a first time period, and a substantially constant field during an immediately following second time period. The device includes a adjustable bus, for providing first and second voltage levels, and a switching or PWM amplifier. A switch is coupled between the bus and the switching amplifier for applying the first voltage to the amplifier during the first time period, and the second voltage to the amplifier during the second time period. The switching amplifier comprises an inverter for generating a PWM voltage in response to its input, and an LC filter for converting the PWM wave into a DC voltage. The switching amplifier generates a substantially higher coil driving voltage during the first period, in response to the first voltage level, than during the second period in response to the second voltage level. The switching amplifier may have a substantially higher frequency of operation during the second period than during the first period, so that the LC filter is much more effective in removing a distorting ripple component during such second time period, when the gradient coil is being used to acquire MR data.

    摘要翻译： 提供了用于驱动MR系统中的梯度线圈的放大装置，其中需要梯度线圈在第一时间段期间产生快速变化的梯度磁场，并且在紧随其后的第二时间段期间产生基本恒定的场。 该装置包括用于提供第一和第二电压电平的可调整总线以及开关或PWM放大器。 开关耦合在总线和开关放大器之间，用于在第一时间段期间将第一电压施加到放大器，并且在第二时间段期间将第二电压施加到放大器。 开关放大器包括用于响应于其输入产生PWM电压的反相器和用于将PWM波转换为DC电压的LC滤波器。 响应于第一电压电平，开关放大器在第一周期期间响应于第二电压电平而产生比在第二周期期间更大的线圈驱动电压。 开关放大器可以在第二周期期间比在第一周期期间具有更高的工作频率，使得LC滤波器在这样的第二时间段内去除失真纹波分量时更有效，当梯形线圈被用于 获取MR数据。

    High-efficiency switching power amplifier
    3.
    发明授权
    High-efficiency switching power amplifier 有权
    高效开关功率放大器

    公开(公告)号：US6166602A

    公开(公告)日：2000-12-26

    申请号：US406405

    申请日：1999-09-27

    申请人： Robert Louis Steigerwald ,  William Frederick Wirth

    发明人： Robert Louis Steigerwald ,  William Frederick Wirth

    IPC分类号： H03F3/217

    CPC分类号： H03F3/2178

    摘要： A plurality of low-voltage, series-connected input dc-dc converters provide the input to a low-frequency, high-voltage dc-ac output bridge converter suitable for driving a gradient coil in an MRI system. The relatively low-voltage, series-connected dc-dc converters, or choppers, control the gradient coil current, while the dc-ac converter bridge steers the current to the proper coil polarity. A binary weighting of the voltage ratings of the input choppers results in the lowest voltage unit doing most of the high-frequency switching. Such an amplifier configuration is modular and allows for different gradient coil requirements to be met with a common approach by applying a predetermined number of choppers and bridges.

    摘要翻译： 多个低压，串联连接的输入dc-dc转换器将输入提供给适用于驱动MRI系统中的梯度线圈的低频，高压直流交流输出桥式转换器。 相对低压，串联连接的dc-dc转换器或斩波器控制梯度线圈电流，而dc-ac转换器桥将电流转向正确的线圈极性。 输入斩波器的额定电压的二进制加权导致最低电压单元进行大部分高频开关。 这种放大器配置是模块化的并且通过应用预定数量的斩波器和桥接器可以通过常见的方法来满足不同的梯度线圈要求。