热Σ-Δ调制技术及在MEMS气体传感器中的应用

Thermal Σ-Δ Modulation Technique and Its Application in the MEMS Gas Sensor

微加热器是MEMS气体传感器的重要功能部件,其结构设计与温度控制是MEMS气体传感器设计的重要环节。针对一类典型MEMS气体传感器设计了一款采用热Σ-Δ调制技术的电路,对其微加热器进行闭环温度控制,相比传统的模拟闭环控制电路,该电路结构简单,对元件失配性要求低,在实现温度控制的同时实现了加热器激励信号的数字化。此外,作为调节控制的MOS管工作在开关状态,显著降低其功耗和对功率容量的要求。重点介绍了微加热器的热电等效模型、热Σ-Δ调制控制的基本工作原理、实现电路与测试结果等,实验数据表明微加热器温度控制环路信噪比可达60 dB以上。将其应用于一款可探测挥发性有机物(VOC)的MEMS气体传感器,温度控制稳定性达到0.75%,满足了传感器性能要求。

The micro heater is an important functional component of the MEMS gas sensor, and the structure design and temperature control of the micro heater are important parts for the design of the MEMS gas sensor. A closed-loop temperature control circuit using the thermal ∑-△ modulation technology was proposed for the typical micro heater which was commonly used in certain MEMS gas sensors. Compared to the traditional analog closed-loop control circuit, the new circuit has a simple structure and low requirement for the circuit element mismatch, and can realize the temperature control and digitize the excitation signal of the heater at the same time. Furthermore, the regulatory control MOS transistor worked in the on-off state, significantly reducing the MOS transistor power consumption and power capacity requirements. The thermoelectric equivalent model of the micro heater and the operating principle, the implement circuit and the test results of the thermal ∑-△ modulator were discussed primarily. The test results show that the signal to noise ratio of the temperature control loop for the micro heater is above 61） dB. Finally, the proposed method was used for a MEMS volatile organic compound （VOC） gas sensor. And the stability of the temperature control for the sensor reaches 0.75%, satisfying the performance requirements.