Design of electric energy measurement circuit using ADE7755 smart meter

　　Analysis of electric energy metering circuit: ADE7755 is powered by a single power supply of +5V and 15mV power consumption. After power is applied, the ADE7755 chip is initialized and starts to work. The signals of the current channel and the voltage channel are amplified by the amplifier and converted into two digital signals through the internal analog-to-digital converter. When measuring power, the current path signal also needs to pass through a high-pass filter to remove the DC bias in the channel, which may cause the phase inconsistency of the two channels. For this, the phase angle change can be compensated by the phase adjustment circuit, and then the two signals are added to the digital multiplier at the same time, and then pass through the low-pass filter, and finally enter the digital/frequency converter to obtain a high-frequency pulse proportional to the instantaneous power and a low-frequency pulse proportional to the average power, and output them at the CF, F1, and F2 terminals respectively. After the voltage signal is obtained from the grid sampling and sent to V2P and V2N on channel 2, it 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.

　　The electric energy metering circuit is shown in the figure, which is mainly composed of voltage detection circuit, current detection circuit, electric energy metering chip ADE7755 and its peripheral circuits. First, the load current passes through the shunt and then through the filter circuit to convert it into a suitable voltage signal and send it to the current channel of the electric energy metering chip ADE7755, namely the V1P and V1N terminals; while the 220V phase voltage is stepped down through the precision resistor attenuation network, and then sent to the voltage channel of the electric energy metering chip ADE7755, namely the V2P and V2N terminals, through the filter circuit. The two are converted into active power by ADE7755 and output from the CF terminal in the form of high-frequency pulses 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 pulses from the CF terminal of ADE7755 and sends the processed data to the LCD display circuit for display, and transmits the data to the host computer through the remote communication circuit. The CF pin is connected to the T0 counter of the microcontroller through a photocoupler . The microcontroller counts the pulses output by the CF pin and then calculates the measured power based on the principle of ADE7755.