Design Of Data Acquisition Module For Energy Metering IC

With the increasing environmental problems,electric energy has been widely used due to its advantages of cleanliness an.d convenience.The increase in electricity consumption has led to the rapid development of electric energy metering.How to scientifically and accurately measure the consumed elec.trical energy becomes a problem that cannot be ignored.At present,the main working principle of the energy metering chip is to perform analog-to-digital conversion on the voltage and current collected by the transformer,and complete the calculation through the internal digital signal processing unit.The current fluctuates widely because of the magnitude of the load,which has a certain impact on the accurate metering of the energy metering chip.In order to solve the problem of metering accuracy under load change,a data acquisition module for wide current range energFy metering chip is designed.The module is realized by TSMC 0.18μm CMOS technology.The system consists of a low pass filter,an automatic gain control amplifier circuit,and a sigma delta modulator circuit.The low-pass filter adopts an active second-order low-pass filter circuit,and the automatic gain control amplifier circuit is composed of an 8-bit successive approximation analog-to-digital converter,a programmable gain amplifier,an amplitude detection module and a gain control module,and the Sigma Delta modulator adopts Fourth-order feedback cascaded integral structure.According to the accuracy grade of the meter,important parameters such as the order of the modulator and the number of quantizers that meet the accuracy requirements are determined.The parameter design of the modulators is completed,and various non-ideal factors are added to the modulator in Simulink.The model was verified by simulation.Secondly,the automatic gain control circuit model is established in Simulink,which verifies the function and stability of the automatic gain control system.According to the performance requirements of each module in the model,the design and simulation of low-pass filter circuit,bandgap reference circuit,automatic gain control amplifier circuit and fourth-order modulator circuit are completed.The final simulation results show that the cutoff frequency of the low-pass filter circuit is 2kHz.The automatic gain amplifier circuit realizes the differential signal amplitude between 250mV and 500mV when the amplitude of the differential input signal is between O～1V.At a clock frequency of 1.28MHz,an oversampling rate of 128,and a bandwidth of 2kHz,the SNR of the Sigma Delta modulator circuit reaches 101.8dB,which satisfies the acquisition accuracy requirements of the 0.1-level energy metering chip.The layout design of the circuit is completed,and the simulated partial layout area is 800μm×700μm.