Design Of Special ADC For Energy Metering IC

With the increasing popularization of the electric energy meter, the high performance energy metering IC have been applied in electric automation system widely. Actual energy metering IC mainly uses sigma-delta ADC to convert the voltage and current signal collected by instrument transformer to digital signal. This ADC adopts oversampling, noise-shaping and digital filtering technique. It has a lot of advantages, such as high precision, low cost, low requirement of component match, easy interfacing with digital system and so on. Therefore comparing with other types ADC, it is more suitable for the energy metering IC's integration and improves the accuracy and reliability of energy metering.Based on CMOS process and the use of integrated circuit EDA design and simulation tools, the frontend design of special sigma-delta ADC for energy metering IC is completed in this thesis, including implementation of two orders sigma-delta modulator and digital decimation filter.By analyzing operation principle of the energy metering IC and the basic theory of sigma-delta ADC, Two orders distributivity feedforward structure based on loop filtering form is adopted in the system design of sigma-delta modulator to meet the requirement of energy metering application. Its feasibility and stability were proved by determining over-sampling ratio, system analysis after introducing storage gain factor and Matlab modeling. Then the modulator's sub-circuits, such as switch capacitor integrator, folded cascade operation amplifier, comparator, programmable gain amplifier, 1-bit DAC, nonoverlapping clock generator and so on, are design, analyzed and simulated according to performance demand of them. On the basis of these sub-circuits, the whole modulator is implemented. In the digital circuit part, this thesis presents a method in which high order combfilter directly decimates and filters the modulated signal. The hardware structure of the combfilter is optimized and described by Verilog-HDL. Finally the code of the combfilter is simulated, synthetized and verificated in the FPGA.