New multi-function energy meter circuit design based on CS5463 - Power Circuit - Circuit Diagram

0 Preface

Traditional inductive electric energy meters are limited by their structure and principle. They usually have shortcomings such as small measurement range, poor stability and low precision, which cannot meet the needs of social development. With the development and popularization of microelectronics technology and single chip microcomputer, new intelligent measurement and control technology has developed rapidly. The electronic energy meter with the single chip as the core shows its obvious advantages. This article uses single-chip microcomputer as the main controller of the instrument, and Cirrus Logic's energy metering chip is responsible for collecting data, so it has the advantages of high cost performance, strong anti-interference ability and high measurement accuracy.

1 circuit working principle

This design adopts switching power supply, which regulates 220 V AC mains to analog and digital two +5 V voltage, which supplies power to the entire meter circuit. The system detects the current signal through the current transformer, and collects the voltage signal through the voltage dividing resistor, and then sends it into the single-phase power/power integrated chip CS5463, and performs signal sampling, calculation and error correction on the chip. The whole process is carried out under the control of the single-chip PLC916. Its principle block diagram is shown in Figure 1.



2 dedicated metering chip CS5463

The CS5463 is a highly integrated Δ∑-transformer with two Δ∑ analog-to-digital converters (ADCs), high-speed energy calculations, and a serial interface. It accurately measures and calculates active energy, instantaneous power, reactive power, I _RMS and V _RMS and can be used to develop single-phase 2-wire or 3-wire meters. The CS5463 can measure current using a low-cost shunt or current transformer and use a voltage divider resistor or voltage transformer to measure the voltage. The CS5463 has a bidirectional serial port that communicates with the microcontroller. The pulse output frequency of the chip is proportional to the amount of function. The CS5463 features a convenient on-chip AC/DC system calibration function. Its "self-booting" feature allows the CS5463 to work alone and automatically initializes when the system is powered up. In self-boot mode, the CS5463 can read calibration data and start-up instructions from an external EEP-ROM. With this mode, the CS5463 does not require an external microcontroller to operate, so when the meter is used for high-volume residential energy measurement, the cost of the meter can be reduced.

The CS5463 provides instantaneous voltage/current/power data sampling and periodic calculations with functional quantities, I _RMS , and V _RMS . To accommodate low-cost measurement applications, the CS5463 can also output bursts on a given pin. The number of pulses output is proportional to the value of the function register. The CS5463 is optimized for power measurement and is suitable for measuring current with a shunt or current transformer and is connected to a voltage divider resistor or voltage transformer to measure voltage. To accommodate different levels of input voltage, the CS5463's current path integrates a gain-programmable amplifier (PGA) that allows input level full scale selection to be ±250 mVRMS or ±50 mVRMS. The voltage channel's PGA accommodates an input voltage range of ±250 mV. For the VA+ and VA- terminals with a single +5 V supply, the common mode signal voltage applied between the differential mode input pins of the two channels is -0.25~+5 V. In addition, when designing, it is also possible to implement double-ended differential mode input in one channel or two channels. At this time, the common mode voltage of the input signal will be added to AGND. The CS5463 has a high-speed digital filter per channel that attenuates and integrates the output of two Δ∑ modulators by a factor of 10. The filter outputs 24-bit data at a word output rate (OWR) of (MCLK/K)/1024. To facilitate communication with external microcontrollers, the CS5463 integrates a simple three-wire serial interface. This serial port is compatible with the SPI ^TM and Micro wire ^TM standards. The serial clock (SCLK) and RESET pins of the serial port contain a Schmitt trigger that allows the use of slower rising signals.

The main features of the CS5463 are as follows:

◇In the dynamic range of 1000:1, the linearity of the energy data is ±0.1%;

â—‡ can measure instantaneous voltage, current and power, including IRMS and VRMS, apparent power, active and reactive power, active fundamental and harmonic power, reactive fundamental power, power factor, frequency, etc.

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