应用于高频数字化LLC谐振变换器的变模态调制策略

以数字化LLC谐振变换器为研究对象,针对其达到1MHz应用时出现的频率分辨率不足及其导致的输出电压脉动问题,提出了一种抑制该问题的变模态调制策略。该策略包含两个模态：传统的仅调节频率的频率调制模态和频率及占空比同时调节的复合调制模态。在复合调制模态下,当检测到开关频率以最小频率间隔来回跳动时,锁定开关频率并通过调节占空比以实现对变换器电压增益的精细调节,从而抑制单一频率调制下出现的输出电压脉动问题。文中给出了该策略的工作原理分析、设计要点分析,并在一台1 MHz的样机上完成了对比实验,实验结果验证了所提出变模态策略的有效性。     

A portable high-frequency digitally controlled oscillator (DCO)

A novel digitally-controlled oscillator (DCO) is reported. Utilizing a new capacitive load, the new DCO is capable of producing much higher output frequencies than existing DCOs. All other components are fully digital and modular, allowing portability to any CMOS process and customization for different applications. At the heart of the DCO is a digital ring oscillator (DRO) that utilizes the new shunt-capacitive loads. Unprecedented higher frequencies are obtained through a novel idea of electrically removing the effect of un-enabled loads. Simple design conditions for achieving proper operation of the DRO are provided and verified through simulations with several technologies. Spice simulations verified the correct and superior operation of the DCO even with device mismatch. A custom layout of the DRO was generated using LFoundry's 150 nm technology. The total DRO area was found to be 418 µm². Comparison with other DCOs and VCO shows that the new DCO outperforms conventional DCOs in all aspects; maximum attainable frequency, power efficiency and required number of control bits to achieve a certain resolution.     

不平衡电桥的自动平衡和测量

电桥是一种结构简单的检测电路,准确度和灵敏度都较高,广泛应用于检测仪器中.本文在分析电路原理及熟悉数字电位器、A/D转换芯片的基础上设计了电桥自动平衡和自动测量电路,按照这种设计整个平衡过程不需控制电路的参与,节省了CPU的调节时间.并讨论了电路设计中的关键问题.     

一种dB线性数字控制可变增益放大器的设计

设计了一种dB线性增益的数字控制可变增益放大器。以二极管做负载的全差分输入共源极放大器为原型,通过同时同比例地改变输入输出晶体管尺寸比和偏置电流比来控制增益变化,使输入输出晶体管的电流密度保持一恒定值,提高了电路在低增益时的线性度。电路采用NEC 0.35μm CMOS标准工艺库进行设计。仿真结果表明,dB线性增益范围为-11.85dB到11.64dB,增益误差小于0.5dB。增益为-11.85dB时,其1-dB压缩点达到8.35dBm,-3dB增益带宽大于62MHz,并且随设定的增益值在62MHz和240MHz之间变化。     

数字电视接收芯片中数控晶体振荡器的设计

运用负阻模型分析石英晶体振荡器,设计实现了一种用于数字电视接收芯片的数控石英晶体振荡器(DCXO).该DCXO采用Pierce结构,利用基带与振荡器的反馈环路产生的6位自动频率控制信号对振荡器的频率漂移进行校准,得到长期稳定的频率输出.电路采用TSMC混合/RF 0.13 μm CMOS工艺实现,中心频率为24 MHz.在1.2 V电源电压下的仿真结果显示:数控范围72×10-6@24 MHz,调节精度1×10-6/step,启动时间约900 μs,振荡器振荡峰值为0.8 V;在偏离中心频率1 kHz和10 kHz处的相位噪声分别为-141 dBc和-155 dBc.该振荡器除石英晶体外,均集成在片内.