The document describes an energy metering integrated circuit from Microchip Technology that provides active real power measurement capabilities. It features two 16-bit delta-sigma analog-to-digital converters, low measurement error over a wide dynamic range, and interfaces for driving mechanical counters and stepper motors. The document outlines the IC's functional blocks, current sensing options, and reference designs for using it in energy metering applications.
This is a training module on Microchip Energy Metering ICs with Active Real Power
Welcome to the training module on Energy Metering ICs with Active Real Power . This training module gives you a brief introduction to Energy meter ICs with Real power measurement.
The MCP3905 and MCP3906 devices from Microchip Technology Inc. are two fully functional, stand-alone energy-measurement ICs that output average and instantaneous real power. They are highly accurate solutions for single-phase energy measurement in residential power meters and industrial applications. The MCP390X energy-measurement ICs address the growing market for electronic-based energy meters, particularly in worldwide emerging markets. The new chips each integrate two 16-bit delta-sigma analog-to-digital converters (ADCs), an internal voltage reference, plus all of the digital circuitry needed to calculate average and instantaneous real power from voltage and current channels. The MCP3905 features a programmable gain amplifier (PGA) with a maximum gain of 16. For energy meters requiring higher accuracy, the MCP3906 has a maximum gain of 32. In addition, these solutions meet or exceed the requirements of the International Electro technical Commission IEC62053 international energy-metering specifications.
The MCP3905A/05L/06A devices are energy metering ICs that supply a frequency output proportional to active (real) power, and higher frequency output proportional to the instantaneous power for meter calibration. Both channels use 16-bit, second-order, delta sigma ADCs that oversample the input at a frequency equal to MCLK/4, allowing for wide dynamic range input signals. A Programmable Gain Amplifier (PGA) increases the usable range on the current input channel (Channel 0). The calculation of the active power, and the filtering associated with this calculation is performed in the digital domain, ensuring better stability and drift performance. Two digital high-pass filters cancel the system offset on both channels such that the real-power calculation does not include any circuit or system offset. After being high-pass filtered, the voltage and current signals are multiplied to give the instantaneous power signal.
The ADCs used in the MCP3905A/05L/06A for both current and voltage channel measurements are delta sigma ADCs. They comprise a second-order, delta sigma modulator using a multi-bit DAC and a third order SINC filter. The delta-sigma architecture is very appropriate for the applications since it is a waveform-oriented converter architecture that can offer both high linearity and low distortion performance throughout a wide input dynamic range. The clocking signals for the ADCs are equally distributed between the two channels in order to minimize phase delays to less than 1 MCLK period
This devices contain an internal POR circuit that monitors analog supply voltage AVDD during operation. This circuit ensures correct device startup at system power-up and system power-down events. The POR circuit has built-in hysteresis and a timer to give a high degree of immunity to potential ripple and noise on the power supplies, allowing proper settling of the power supply during power-up. Once a power-up event has occurred, an internal timer prevents the part from outputting any pulse for approximately 1s, thereby preventing potential meta stability due to intermittent resets caused by an unsettled regulated power supply.
The active real-power value is extracted from the DC instantaneous power. Therefore, any DC offset component present on Channel 0 and Channel 1 affects the DC component of the instantaneous power and will cause the real-power calculation to be erroneous. In order to remove DC offset components from the instantaneous power signal, a high-pass filter has been introduced on each channel. The MCP3905A/05L/06A low-pass filter is a first-order IIR filter that extracts the active real-power information from the instantaneous power signal. The output of the low-pass filter is accumulated in the digital-to-frequency converter. This accumulation is compared to a different digital threshold.
This page describes the current channel, voltage channel, and digital input.
This page is in continuation to previous page describing about the analog supply pin, and frequency output pin.
This page gives you an overview about the current sensing methods. Shunt type and Current transformer connecting types.
The MCP3905A/06A Energy Meter Reference Design is a stand-alone, single-phase residential meter design for active-energy meter designs. For advanced microcontroller-based meter products, this design also serves as the design of the Analog Front-End (AFE). This design includes a low-cost DC power supply circuit and the necessary protection for IEC62053 EMC compliance.
This reference design keeps all of the major components on the back-side of the PCB. This minimizes any ill effects from the environment in the situation that a meter case experiences failure. Only the necessary components for calibration, jumper selection and external connections are placed on the front-side of the board. Keeping the larger DC power supply components on the back-side of the board is also necessary for installation in some meter cases with PCB standoffs.
This evaluation board is designed to test out a variety of energy meter designs. On the input side high-voltage line and load AC-plug headers are included, along with mounting holes for shunts, current transformers and screw-type connections for wiring. On the output side a large prototype area is included along with optical isolation and a standard PIC tail header for experiments with a variety of PIC MCU-based energy meter designs.
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