Analysis of electric energy metering circuit:ADE7755 uses a single power supply with + 5V and power consumption of 15MV. After power on, ADE7755 chip starts to work after initialization. The signals of current channel and voltage channel are amplified by amplifier and converted into two digital signals through internal analog-to-digital converter. During power measurement, the current path signal also needs to pass through the high pass filter to remove the DC bias in the channel. At this time, the phase of the two channels may be inconsistent. For this, the phase angle change can be compensated through the phase adjustment circuit, and then the two signals can be added to the digital multiplier at the same time, then pass through the low-pass filter, and finally enter the digital / frequency converter, The high-frequency pulse proportional to the instantaneous power and the low-frequency pulse proportional to the average power are obtained and output at terminals CF, F1 and F2 respectively. The voltage signal obtained by sampling from the power grid is sent to V2P and v2n on channel 2, and then directly enters the digital to analog converter, and then enters the multiplier to provide power calculation. The two analog-to-digital converters in the chip share a 2.5V reference power supply.

As shown in the figure, the electric energy metering circuit is mainly composed of voltage detection circuit, current detection circuit, electric energy metering chip ADE7755 and its peripheral circuits. Firstly, the load current is converted into appropriate voltage signal through the shunt and then through the filter circuit and sent to the current channel of the electric energy metering chip ADE7755, namely v1p and v1n terminals; The 220V phase voltage is reduced through the precision resistance attenuation network, and then sent to the voltage channel of the electric energy metering chip ADE7755 through the filter circuit, that is, V2P and v2n terminals are converted into active power through ADE7755, output from the CF terminal in the form of high-frequency pulse, and then connected to the external interrupt signal input terminal of the single chip microcomputer AT89C52, That is, the single chip microcomputer control circuit collects the pulse from the CF end of ADE7755, sends the processed data to the LCD display circuit for display, and transmits the data to the upper computer through the remote communication circuit. The CF pin is connected to the t0 counter of the single chip microcomputer through the optocoupler. The single chip microcomputer counts the pulses output by the CF pin, and then calculates the measured power according to the principle of ADE7755.

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