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方波激励下的环形二极管电容检测电路应用于微机械加速度计是一种新的尝试。根据实践,该方案可以很好地在闭环系统中工作。该文建立了这种解调电路的数学模型,进行了误差分析,给出了其参数对闭环系统的影响。该方案在将检测电容变化转换为电压变化的过程中会引入非线性因素,该文证明了这种影响在闭环后可以忽略。计算结果表明,较解调电容的变化,敏感结构电容的变化将对输出电压的变化起主要的影响作用。此外,推导出的静电力公式说明,较大的激励电压会减小系统的稳定裕量。
It is a new attempt to apply a ring diode capacitor detection circuit under the square wave excitation to a micro-mechanical accelerometer. According to practice, this solution works well in closed-loop systems. The paper establishes the mathematical model of this demodulation circuit, analyzes the error and gives the influence of its parameters on the closed-loop system. This scheme introduces a non-linear factor in converting the change in detection capacitance to a voltage change. This paper shows that this effect can be neglected after closed-loop. The calculation results show that the change of the capacitance of the sensitive structure will have a significant effect on the change of the output voltage compared with the change of the demodulation capacitance. In addition, the derived electrostatic force formula shows that a larger excitation voltage will reduce the system stability margin.