Application of programmable chopping gain amplifier to electric energy metering chip

Abstract

The invention discloses an application of a programmable chopping gain amplifier to an electric energy metering chip. The programmable chopping gain amplifier is arranged between a sensor outside the chip and an analog to digital converter in the chip and comprises 8 switches K1-K8, 4 resistors R1-R4 and an operation amplifier U1; and higher low-frequency noise of the operation amplifier is transferred to near the chopping frequency during secondary chopping, thus the low-frequency noise and signals of the operation amplifier are separated, and signal to noise ratio is increased. After the programmable chopping gain amplifier is adopted, the metering chip can reach the precision of 0.1 percent in a wide signal input range of 25uV-50mV.

Description

technical field [0001] The invention relates to the field of electrical devices, in particular to the application of a programmable chopper gain amplifier in an electric energy metering chip. Background technique [0002] At present, more and more watt-hour meters are changing from mechanical to electronic. In contrast, electronic watt-hour meters have many advantages in terms of measurement accuracy, life, and functions. The core of the electronic energy meter is the energy metering chip. The metering chip converts the 50Hz voltage and current signals on the grid into digital signals with an analog-to-digital converter (ADC), and then processes the digital signals with a digital signal processing unit (DSP). A lot of information such as energy, power, effective value, harmonic component, grid frequency, etc. can be obtained. [0003] The energy meter should achieve 0.1% accuracy in a wide current dynamic range (eg 1:2000). The magnitude of the ADC front-end signal for met...

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Problems solved by technology

[0004] The high precision requirements of the ADC for measuring current will bring three challenges: 1. The basic devices of CMOS technology, such as PMOS/NMOS transistors, have relatively high noise near 50Hz. This noise is called flicker noise

Higher noise will reduce the measurement accuracy under small current signals. For example, the requirement of 0.1% accuracy under 25uV signal is equivalent to the requirement that the noise must be less than 25nV. Considering the random characteristics of the noise, it may even require the noise to be less than 10nV; In a complex electromagnetic environment, electromagnetic interference in this environment will enter the input of the ADC that measures the current, and mix with the 50Hz current signa

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