公开(公告)号：US20120126901A1

公开(公告)日：2012-05-24

申请号：US12948896

申请日：2010-11-18

申请人： Chi Tak (Gerry) LEUNG ,  Chik Wai (David) NG ,  Hing Kit KWAN ,  Wai Kit (Victor) SO ,  Po Wah CHANG ,  Wing Cheong MAK ,  Kwok Kuen KWONG

发明人： Chi Tak (Gerry) LEUNG ,  Chik Wai (David) NG ,  Hing Kit KWAN ,  Wai Kit (Victor) SO ,  Po Wah CHANG ,  Wing Cheong MAK ,  Kwok Kuen KWONG

IPC分类号： H03L7/00

CPC分类号： H03L7/08

摘要： A frequency dithering circuit reduces emissions that cause Electro-Magnetic Interference (EMI) by spreading the spectrum of a clock. The clock sequences a counter that drives a digital count value to a digital-to-analog converter (DAC). The DAC outputs a sawtooth wave with a wide voltage swing. A subtractor scales down the voltage swing to produce a reduced-swing sawtooth wave which is used as an upper limit voltage. Comparators trigger a set-reset latch to toggle the clock when current pumps charge and discharge a capacitor beyond voltage limits. Since the upper limit voltage is the reduced sawtooth wave from the subtractor, the amount of time to charge the capacitor varies, dithering the period of the clock. The degree of dithering can be adjusted by programming the feedback resistance in the subtractor. The subtractor reduces the sensitivity of dithering to errors in the DAC, allowing for an inexpensive, less precise DAC.

摘要翻译： 频率抖动电路通过扩展时钟的频谱来减少引起电磁干扰（EMI）的辐射。 该时钟是将数字计数值驱动到数模转换器（DAC）的计数器。 DAC输出宽电压摆幅的锯齿波。 减法器缩小电压摆幅，产生用作上限电压的减小摆动锯齿波。 当电流泵对电容器充电和放电超过电压限制时，比较器触发设置复位锁存器来切换时钟。 由于上限电压是来自减法器的减少的锯齿波，所以对电容器充电的时间量变化，使时钟的周期抖动。 可以通过对减法器中的反馈电阻进行编程来调整抖动度。 减法器可降低抖动对DAC误差的灵敏度，从而实现廉价，精度更低的DAC。

公开(公告)号：US20110216559A1

公开(公告)日：2011-09-08

申请号：US12718707

申请日：2010-03-05

申请人： Chik Wai (David) Ng ,  Hing Kit Kwan ,  Po Wah Chang ,  Wai Kit (Victor) So ,  Kwok Kuen Kwong

发明人： Chik Wai (David) Ng ,  Hing Kit Kwan ,  Po Wah Chang ,  Wai Kit (Victor) So ,  Kwok Kuen Kwong

IPC分类号： H02M3/335

CPC分类号： H02M3/335

摘要： A fly-back AC-DC power converter has a constant-current control loop that senses the primary output current in a transformer to control the secondary output without an expensive opto-isolator. A primary-side control circuit can use either a Quasi-Resonant (QR) or a Pulse-Width-Modulation (PWM) control loop to switch primary current through the transformer on and off. A feedback voltage is compared to a primary-side voltage sensed from the primary current loop to turn the switch on and off. A multiplier loop generates the feedback voltage using a multiplier. A level-shift inverter and a low-pass filter act as the multiplier by multiplying an off duty cycle of the switch by the feedback voltage to generate a filtered voltage. A high-gain error amp compares the filtered voltage to a reference voltage to generate the feedback voltage. The multiplier produces a simple relationship between the secondary current and the reference voltage, yielding simplified current control.

摘要翻译： 回扫AC-DC电力转换器具有恒定电流控制回路，其感测变压器中的主要输出电流，以在没有昂贵的光隔离器的情况下控制次级输出。 初级侧控制电路可以使用准谐振（QR）或脉冲宽度调制（PWM）控制回路来切换通过变压器的一次电流的开和关。 将反馈电压与从初级电流回路感测的初级侧电压进行比较，以打开和关闭开关。 乘法器环路使用乘法器产生反馈电压。 电平移位反相器和低通滤波器通过将开关的占空比乘以反馈电压作为乘法器，以产生滤波电压。 高增益误差放大器将滤波电压与参考电压进行比较，以产生反馈电压。 乘法器产生二次电流和参考电压之间的简单关系，产生简化的电流控制。