Differential switched-capacitor dual slope watthour meter circuit
AssigneeGeneral Electric Company
InventorMiran Milkovic
Life of this patent
Estimating the term…
Abstract
Transient offset error voltages due to charge injection by MOS analog switches and DC offsets of multipliers in switched-capacitor integrators of electronic metering circuits are compensated by the common mode rejection of a differential switched-capacitor integrator. To cancel internal DC offset voltages of the integrator amplifier, a series capacitor connected to the inverting input of the amplifier is charged, during the autozero phase of the clock cycle, to a voltage equal to the internal DC offset voltage of the amplifier and subsequently, during the integration phase of the clock cycle, this voltage is applied to the inverting input of the amplifier.
Claims18
An electronic circuit for measuring energy consumption in an electrical system comprising:
- multiplying means for providing first and second signals of equal magnitude and opposite polarity, each of said signals representing instantaneous power in the electrical system;
- a switched-capacitor integrator for integrating said signals to provide a third signal representative of average energy, said integrator comprising a differential amplifier having an inverting input and a non-inverting input, a feedback capacitor connected between an output of the amplifier and the inverting input, a first switched-capacitor network coupled between the inverting input and said multiplying means for supplying the first signal to the inverting input, and a second switched-capacitor network coupled between the non-inverting input and said multiplying means for providing the second signal to the non-inverting input, said first and second switched-capacitor networks each comprising an input capacitor and analog switches for connecting the input capacitor between said multiplying means and a respective input of said amplifier or to a reference potential;
- and
- means for operating said switches such that during a first time interval said first and second signals are supplied substantially simultaneously to said amplifier inputs and during a second time interval said input capacitors are connected to said reference potential.
An electronic circuit for measuring energy consumption in an electrical system comprising, on an integrated circuit chip:
- multiplying means for providing first and second signals of equal magnitude and opposite polarity, each of said signals representing instantaneous power in the electrical system;
- a differential switched-capacitor integrator for integrating said first and second signals to provide a third signal representative of average power, said switched-capacitor integrator comprising a differential amplifier having inverting and non-inverting inputs;
- and
- network means coupled to said amplifier for supplying samples of the first and second signals to said inputs repetitively and substantially simultaneously.
Dependencies are inferred from the claim text.