光纤直流电流传感器中的V/F转换电路

Ultra-low-dissipation Voltage-frequency Converter Used in DC Optical Current Transformer

为了提高供能激光器的寿命和可靠性,降低高压侧信号调制电路的功耗。在介绍用于高压直流输电线路中测量直流电流的光供电式光纤电流传感器的基本原理后,利用CMOS器件的超宽工作电压范围、超低工作电流和窄脉冲的特性,采用集成电路和分立元件(改进型电荷平衡式V/F转换器)设计了含温度补偿电路的低成本超低功耗V/F转换电路,该电路经测试,该电路的功耗<0.7mW,线性度约为0.05%。该V/F转换电路已成功应用在光供电式光纤电流传感器的高压侧调制电路中。

An optical-power supplied optical current transformer is introduced, which is used to measure the dc current in pole bus of high voltage dc current transmission. DC shunt is adopted in optical fiber current sensor to sense de current signal. High-voltage processing unit converts the voltage signal proportional to the direct current to digital signal that drives the LED to generate optical pulse signals. Through fibers these pulse signals are transmitted to the earth-potential side where they are received and converted to electronic signals. To increase the life and reliability of power-supplied laser diode, it is requested that the dissipation of modulation circuit in high voltage side is as low as possible. In fact, modulating circuit is the key factor influencing the measuring performance and power consumption. Otherwise, modulation circuit should have excellent temperature characteristic. For this purpose, an ultra-low power dissipating voltage-frequency converter with temperature compensation is designed. It consists of integrated circuits and discrete elements and utilizes the characteristic of narrow pulses as well as the characteristics that CMOS components have ultra wide operation voltage range and ultra low operation current. This circuit is an improved charge-balanced voltage-frequency converter with good temperature performance and in low cost. Testing result shows its dissipation is less than 0. 7 mW and linearity is better than 0.05%. This V/F converter has been used in the high-voltage-side circuit of optical-power supplied optical current transformer successfully.