Controlling the operation of an electricity meter's secondary power supply during loss of AC power

Abstract

The AC line voltage detection circuit includes an AC sense circuit, a power supply control circuit, and a power supply hold up circuit. The AC sense circuit is configured to generate a signal to the processor and the power supply control circuit upon detecting the absence of AC line voltage. The power supply control circuit is configured to generate a control signal to a power supply that provides power to the processor to shut down the power supply. The processor is configured to generate a signal to the power supply control circuit and to generate a signal to a power supply hold up circuit configured to prevent shutdown of the power supply. The power supply hold up circuit signal overrides the AC sense circuit signal. The processor is further configured to generate a subsequent signal to the power supply hold up circuit to allow shutdown of the power supply.

Description

[Technical field]

[0001] Unless otherwise indicated herein, the material described in this section is not prior art to the claims of this application and is not admitted to be prior art by inclusion in this section.

[0002] Electric meters measure the power consumed by customers of an electric utility provider. Electric meters are plugged into a meter socket mounted in an enclosure in a building or other structure and draw their operating power from the electric distribution grid. Electric meters record electrical energy consumption and communicate that information, as well as the status of the meter itself, to the electric utility provider for monitoring and billing. In the event of an alternating current (AC) power outage, the electric meter will be unable to communicate with the electric utility provider.

[0003] In the event of a power outage, to operate the radio so that the electric meter can provide "last-gasp" communications to the utility provider, the electric meter may rely on energy stored in a storage capacitor to maintain operation of the communications circuitry for a limited time. The stored energy must be sufficient to operate the electric meter power supply and maintain radio operation. The capacitors required to store enough energy to operate the radio for extended periods of time can be large and expensive. Efficient power supply operation maximizes the amount of time the radio can operate with the limited energy available from the storage capacitor.

[0004] A system and method may be provided for operation of a power supply for an electric meter during a power outage.

[0005] According to various aspects, an alternating current (AC) line voltage detection circuit is provided. In some aspects, the AC line voltage detection circuit can include an AC sense circuit, a power supply control circuit, and a power supply hold-up circuit. The AC sense circuit can be configured to generate a signal to the processor and the power supply control circuit in response to detecting the absence of AC line voltage. In response to receiving the signal from the AC sense circuit, the power supply control circuit can be configured to generate a control signal to the power supply to shut down the power supply. The power supply can be configured to provide power to the processor.

[0006] In response to receiving a signal from the AC sense circuit, the processor can be configured to generate a signal to the power supply hold up circuit. In response to receiving a signal from the processor, the power supply hold up circuit can be configured to generate a signal to the power supply control circuit that prevents shutdown of the power supply. The signal generated by the power supply hold up circuit can override the signal from the AC sense circuit. The processor can be further configured to generate a subsequent signal to the power supply hold up circuit that allows shutdown of the power supply.

[0007] According to various aspects, an electric meter is provided. In some aspects, the electric meter can include a processor configured to control operation of a portion of the circuitry of the electric meter, a power supply configured to provide power to the processor, and an alternating current (AC) line voltage detection circuit. The AC line voltage detection circuit can include an AC sense circuit, a power supply control circuit, and a power supply hold-up circuit.

[0008] The power supply control circuit can be configured to generate a signal to the power supply based on the signal received from the AC sense circuit and the signal received from the power supply hold-up circuit. The signal generated by the power supply control circuit can maintain operation or shut down the power supply according to the signals received from the AC sense circuit and the power supply hold-up circuit.

[0009] According to various aspects, a method for operating an electricity meter during a loss of alternating current (AC) power is provided. In some aspects, the method can include detecting, by an AC line voltage detection circuit, the absence of AC line voltage, generating, by an AC sense circuit of the AC detection circuit, a first signal indicative of the detected loss of AC line voltage to a processor of the electricity meter, and generating, by a power supply control circuit of the AC detection circuit, a second signal configured to shut down a power supply. The power supply can be configured to provide power to the processor.

[0010] The method may further include generating, by the processor in response to receiving the first signal, a third signal to a hold-up circuit of the AC detection circuit that prevents shutdown of the power supply, and generating, by the power supply control circuit in response to receiving the third signal, a fourth signal to the power supply. The fourth signal may be configured to maintain operation of the power supply and enable the processor to complete a power loss operation. The fourth signal may override the second signal upon loss of AC line voltage.

[0011] The method may further include generating, by the processor, a fourth signal to the hold-up circuit upon completion of the power loss operation indicating that the processor has completed the power loss operation, and generating, by the hold-up circuit, a fifth signal to the power supply, the fifth signal causing the power supply to shut down. Shutting down the power supply shuts down the processor and other circuitry energized by the power supply.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS Aspects and features of various embodiments will become more apparent from the following detailed description of the invention, taken in conjunction with the accompanying drawings, in which: FIG. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 illustrates an example of a utility management system according to some aspects of the present disclosure. [Diagram 2]FIG. 1 is a block diagram illustrating an example of an electric meter according to various aspects of the present disclosure. [Diagram 3] FIG. 1 is a simplified block diagram illustrating an example of an electric meter illustrating power and control signals according to some aspects of the disclosure. [Figure 4] FIG. 2 is a simplified block diagram illustrating an example of an AC detection circuit according to some aspects of the present disclosure. [Diagram 5] 4 is a flow chart illustrating an example of a method for operating an electricity meter upon loss of AC power in accordance with an aspect of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Although specific embodiments are described, these are presented by way of example only and are not intended to limit the scope of protection. The devices, methods and systems described herein can be embodied in various alternative forms. Moreover, various omissions, substitutions and changes can be made in the exemplary method and system forms described herein without departing from the scope of protection.

[0015] An electric meter measures the power consumed by a customer of an electric utility provider. The electric meter is plugged into a meter socket mounted in an enclosure in a building or other structure and provides the customer's connection to the power provided by the electric utility. The electric meter measures and controls the electricity delivered to the customer premises through the power grid. The electric meter is combined with a communication module that allows the meter to communicate with other meters and the electric utility. The electric meter may be part of a utility management system.

[0016] Fig. 1 is a diagram illustrating an example of a utility management system 100 according to various aspects of the present disclosure. With reference to Fig. 1, the utility management system 100 may include an electric meter 105, a head-end system 110, and a storage device 120. Although Fig. 1 illustrates one electric meter 105 for ease of explanation, one skilled in the art will understand that multiple electric meters 105 may be included in the disclosed utility management system 100 without departing from the scope of the present disclosure.

[0017] The electric meter 105 can monitor and / or record energy usage at the customer premises 130 and communicate information regarding the energy usage to the head-end system 110. For example, the electric meter 105 can continuously monitor and record the total energy usage at the customer premises 130. In accordance with various aspects of the present disclosure, the electric meter 105 can monitor and / or record the day of the week and time of day associated with the energy usage at the customer premises 130 and communicate that information to the head-end system 110. Additionally, the electric meter 105 can act as a sensor to detect and / or record anomalous readings and / or events, such as, but not limited to, power outages. Those skilled in the art will appreciate that other information can be monitored and communicated by the electric meter 105, such as, but not limited to, average power consumption, peak power, etc.

[0018] The electric meter 105 can communicate with the head-end system 110 and / or other electric meters via wired or wireless communication interfaces known to those skilled in the art using a communication protocol appropriate for the particular communication interface. A variety of wired or wireless communication interfaces and associated communication protocols can be implemented in the electric meter 105 for communication with the head-end system 110. For example, in some embodiments, a wired communication interface is implemented, while in other embodiments, a wireless communication interface may be implemented for communication between the electric meter 105 and the head-end system 110. In some embodiments, a wireless mesh network can connect multiple electric meters 105. The multiple electric meters 105 can communicate with other networks to transmit data to a collector (not shown) that transmits the data to the head-end system 110. The electric meters 105 can communicate using radio frequency (RF), cellular, or power line communication. Those skilled in the art will appreciate that other communication methods can be used without departing from the scope of the present disclosure.

[0019] The head-end system 110 may include a storage device 120. The storage device 120 may be, for example, but not limited to, one or more hard disk drives, solid state memory devices, or other computer readable storage media. Those skilled in the art will appreciate that other storage configurations may be used without departing from the scope of the present disclosure. A database 125 may be stored in the storage device 120. The database 125 may store information collected from the electric meter 105. For example, the database 125 may include days of the week and times of the day that correlate with operational information of the loads, for example, but not limited to, average power consumed by the loads, peak power consumed by the loads, etc. Those skilled in the art will appreciate that this information is exemplary and that other information may be included in the database 125 without departing from the scope of the present disclosure.

[0020] The head-end system 110 and the electric meter 105 may be connected to an electrical power distribution grid 140. The electrical power distribution grid 140 may include power plants (not shown) that generate electrical power (not shown), substations (not shown) that step up the voltage for transmission and step down the voltage for distribution, high voltage electrical transmission lines (not shown), and electrical distribution lines (not shown).

[0021] 2 is a simplified block diagram illustrating an example of an electric meter 200 according to some embodiments of the present disclosure. The electric meter 200 may be, for example, the electric meter 105 of FIG. 1. The electric meter 200 may also be referred to as a smart meter or a smart electric meter. The electric meter 200 may include a control circuit 205, a communication module 230, an auxiliary circuit 240, an offline switching power supply 260, one or more regulated power supplies 262, and one or more storage capacitors 270.

[0022] The control circuit 205 may include a memory 220, an AC detection circuit 250, and a power supply control circuit 265. The power supply control circuit 265 may control the operation of the offline switching power supply 260 during normal operation of the electric meter 200. For example, the power supply control circuit 265 may monitor and control the duty cycle and / or operating frequency of a pulse width modulator (PWM) of the offline switching power supply 260 depending on the load condition of the offline switching power supply 260.

[0023] The auxiliary circuitry 240 may include sensors 247 and a metrology processor 245, among other components. The metrology processor 245 may be, for example, but not limited to, a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device. The metrology processor 245 may be in electrical communication with the memory 220, the communication module 230 (e.g., wireless processor 235), and the sensors 247. The metrology processor 245 may receive data generated by the various sensors 247 of the electric meter 200, including, but not limited to, energy usage, voltage, current, and the like, and perform operations on the data or its processing. The metrology processor 245 may be in communication with the communication module 230 to transmit various operating parameters (e.g., energy usage, etc.), diagnostic data (e.g., error conditions, etc.), or other electric meter information (e.g., GPS coordinates, etc.) to a head-end system and / or other electric meters via a wired or wireless network. The metrology processor 245 may also be in communication with one or more regulated power supplies 262 .

[0024] The AC detection circuit 250 can detect a loss of AC power from a power grid, e.g., a substation or other AC power, to the electric meter 200. When AC power is provided to the electric meter 200, the AC detection circuit 250 can generate one or more AC detection signals that indicate the presence of AC power. For example, the AC detection circuit 250 can generate a time-varying signal, such as a square wave signal having approximately the same frequency as the frequency of the AC line voltage from the power grid. Other signals can be used without departing from the scope of the present disclosure.

[0025] The AC detection signal can be received by the metrology processor 245. Upon detecting a loss of AC power, the AC detection circuit 250 can generate one or more AC power loss signals. The AC power loss signal can be, for example, a signal having a substantially constant DC voltage level. Other signals can be used without departing from the scope of this disclosure. The AC power loss signal can be received by the metrology processor 245. The AC power loss signal can enable the metrology processor 245 to control operation of one or more regulated power supplies 262 to conserve energy stored by the electric meter 200, for example, by one or more storage capacitors 270, required for last gasp communication.

[0026] The memory 220 may be a storage device, such as, for example, a solid state storage device or other storage device, or may be a combination of volatile and non-volatile storage or memory. The memory 220 may be configured to communicate with various processors (e.g., metering processor, radio processor, etc.) included in the electric meter 200. In some embodiments, portions of the memory 220 may be included within the various processors. The memory 220 may be configured to store instructions executable by the various processors, data generated by various sensors of the smart meter 200, and other applications executable by the various processors.

[0027] The communication module 230 may be a wired or wireless transceiver operable to communicate via various wired or wireless protocols known in the art, such as, but not limited to, an AMI protocol, an RF protocol, a cellular protocol, a PLC network protocol, etc. The communication module 230 may include a processor 235 configured to control the operation of the communication module 230. The wireless processor 235 may be, for example, but not limited to, a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, etc. The wireless processor 235 may be in electrical communication with the memory 220 and / or the metrology processor 245.

[0028] In some implementations, the communication module 230 may include an AMI device and / or an AMR device including an AMI radio and / or an AMR radio 237. The AMI radio and / or AMR radio 237 may send and receive data to and from a head-end system using radio frequency (RF) technology or power line communication (PLC). The communication module 230 enables the electric meter 200 to communicate with other electric meters in a network (e.g., an AMI network, etc.) and with a utility provider (e.g., a head-end system, etc.). The communication module 230 may send data and alarm signals to the utility provider and receive either updated program instructions, firmware updates, other setting updates, or other communications.

[0029] The sensors 247 may include, but are not limited to, voltage sensors, current sensors, accelerometers, tilt switches, temperature sensors, and other sensors configured to monitor electrical and physical characteristics of the electric meter 200.

[0030] Offline switching power supply 260 is a direct current (DC) power supply and may receive a primary DC voltage generated by rectifying a primary alternating current (AC) voltage from a grid to which electric meter 200 is connected. Power supply 260 may also be referred to herein as an offline switching power supply or an offline power supply. In some implementations, offline switching power supply 260 may receive and rectify a primary AC voltage. Offline switching power supply 260 may generate a lower secondary DC voltage from the primary DC voltage. The secondary DC voltage generated by offline switching power supply 260 may provide DC power to other components of electric meter 200.

[0031] One or more regulated power supplies 262 can receive the secondary DC voltage output from the offline switching power supply 260 and regulate the secondary DC voltage to a lower DC voltage to operate other circuitry of the electric meter 200, such as, but not limited to, the communications module 230 (e.g., the AMI radio and / or AMR radio 237 and the radio processor 235), and the auxiliary circuitry 240 (e.g., the metering processor 245, the sensors 247, etc.).

[0032] The storage capacitor 270 can provide primary power to the electric meter 200 for a short period of time immediately following a power outage. The storage capacitor 270 can be an electric double layer capacitor (EDLC), also referred to as an ultracapacitor or supercapacitor, or other types of capacitors. The storage capacitor 270 can store enough energy to operate the offline switching power supply 260 for a limited time period so that the electric meter 200 can send a “last gasp” message to the head-end system. The “last gasp” message can include notification of the power outage and other information about the time of the power outage (e.g., energy usage, error conditions, other electric meter information, etc.).

[0033] 3 is a simplified block diagram illustrating an example of an electric meter 300 illustrating power and control signals according to some aspects of the disclosure. With reference to FIG. 3, the electric meter 300 can include an offline switching power supply 310, a first regulated power supply 320, a second regulated power supply 325, a control circuit 305, and an AMI / AMR radio 330. The AMI / AMR radio 330 can include a radio processor 335. The radio processor 335 can be configured to receive data and instructions from a head-end system and to communicate data received from the metering processor 345 to the head-end system.

[0034] The control circuit 305 may be, for example, the control circuit 205 of FIG. 2. The control circuit 305 may be operable to provide a feedback signal 307 to the offline switching power supply 310 via the isolation device 312 for control of the offline switching power supply 310. The control circuit 305 may include an AC detection circuit 365. The AC detection circuit 365 may be, for example, the AC detection circuit 250 of FIG. 2. The offline switching power supply 310 may operate with an input voltage from a primary DC voltage of the electricity meter 300. The primary DC voltage may be generated from an AC line voltage rectified by a full-wave rectifier 302. The primary DC voltage may be, for example, 350 Volts DC (VDC) or another DC voltage. The offline switching power supply 310 may supply a secondary DC voltage HVDC to the first regulated power supply 320 and the second regulated power supply 325.

[0035] The offline switching power supply 310 may be a switching power supply operable to convert a primary DC voltage to a lower secondary DC voltage HVDC, such as, but not limited to, a buck-boost power supply or other power supply. The secondary DC voltage HVDC may be, for example, 12VDC or other DC voltage. The offline switching power supply 310 may convert the primary DC voltage to the secondary DC voltage HVDC by periodically transferring energy stored in a primary winding of the coupled inductor 315 to a secondary winding of the coupled inductor 315. Electrical isolation (e.g., galvanic isolation) between a circuit connected to the primary DC voltage and a circuit connected to the secondary DC voltage may be provided by the coupled inductor 315. In some implementations, the coupled inductor 315 may be a transformer. An isolated feedback of the secondary DC voltage HVDC may be provided to the offline switching power supply 310 via an isolation device 312, such as, but not limited to, an opto-coupler or other isolation device.

[0036] The first regulated power supply 320 may be a switching power supply or other power supply operable to convert the secondary DC voltage HVDC provided by the offline switching power supply 310 to a lower voltage, such as, for example, 3.6 VDC or other DC voltage. The first regulated power supply 320 may provide power to components of the electric meter 300, such as, for example, but not limited to, the AMI radio and / or the AMR radio 330.

[0037] The second regulated power supply 325 may be a switching power supply or other power supply operable to convert the secondary DC voltage HVDC provided by the offline switching power supply 310 to a lower voltage DC (LVDC), for example 3.3 VDC or other DC voltage. The second regulated power supply 325 may provide power to the metrology processor 345 and auxiliary circuits and / or components that do not need to operate after an AC outage. The auxiliary circuits 340 and the metrology processor 345 and / or components may be switched off after an AC outage.

[0038] The AC detection circuit 365 can monitor the AC line voltage from the power grid and generate an AC sense signal 352 to the measurement processor 345. While the AC line voltage is present, the AC detection circuit 365 can generate a time-varying signal, such as, for example, a square wave signal, having approximately the same frequency as the frequency of the AC line voltage, or other signal that indicates to the measurement processor that the AC line voltage is present. While the AC line voltage is present, the AC detection circuit 365 can generate a power supply control signal 356 that enables operation of the second regulated power supply 325.

[0039] In the event of an AC outage, AC detection circuit 365 can detect that AC line voltage is no longer available. AC detection circuit 365 can generate an AC sense signal 352 indicative of AC power loss, e.g., a signal having a substantially constant DC voltage level or other signal, to indicate to metrology processor 345 that AC power has been lost. Upon receiving AC sense signal 352 indicative of AC power loss, metrology processor 345 can perform actions such as taking electrical measurements, passing data to a radio processor, and enabling last-gasp communication to the head-end system.

[0040] The metrology processor 345 can generate a power hold up signal 354 to the AC detection circuit 365. The power hold up signal 354 can prevent the AC detection circuit 365 from disabling operation of the second regulated power supply 325 via the power control signal 356 until the metrology processor 345 has completed the power loss operation. After the power loss operation is completed, the metrology processor 345 can change the state of the power hold up signal 354, which in turn can cause the AC detection circuit 365 to change the state of the power control signal 356 to disable operation of the second regulated power supply 325. Disabling operation of the second regulated power supply 325 eliminates all additional current drawn by the second regulated power supply 325 and all auxiliary circuitry 340 (including the metrology processor 345) energized by the second regulated power supply 325, conserving energy that can be used for last-gasp communications by the AMI / AMR radio 330.

[0041] FIG. 4 is a simplified block diagram illustrating an example of an AC detection circuit 400 according to some aspects of the disclosure. With reference to FIG. 4, the AC detection circuit 400 may include an AC sense circuit 410, a power supply control circuit 450, and a power supply hold-up circuit 455. The AC sense circuit 410 may include a comparator 420 configured to detect the presence of an AC line voltage. As shown in FIG. 4, a voltage representative of the AC line voltage may be applied to a first input 422 of the comparator 420. A voltage representative of an HVDC voltage level (e.g., approximately 12V HVDC generated by the offline switching power supply 310) may be applied to a second input 424 of the comparator 420.

[0042] When AC line voltage is present, the output signal 426 of the comparator 420 can change state between a high state and a low state when the voltage representing the AC line voltage applied to the first input 422 of the comparator 420 exceeds the voltage representing HVDC applied to the second input 424 of the comparator 420. Diode D1 causes the AC sense signal 440 to change state between a low state of about 0 volts and a high state of about the LVDC voltage level (e.g., about 3.3 V LVDC generated by the second regulated power supply 325), resulting in a square wave signal having about the same frequency as the frequency of the AC line voltage. The AC sense signal 440 can be the AC sense signal 352 shown in FIG. 3. The square wave AC sense signal 440 can be received by a metrology processor (e.g., metrology processor 345) as an indication that AC line voltage is present.

[0043] In the event of an AC power outage, a second voltage representative of the HVDC voltage level can be applied to the first input 422 of the comparator 420 instead of the voltage representative of the AC line voltage. The second voltage representative of the HVDC voltage level applied to the first input 422 of the comparator 420 can be lower than the voltage representative of the HVDC voltage level applied to the second input 424 of the comparator 420. As a result, the output signal 426 of the comparator 420 can stop changing state and remain in a high state. When the output signal 426 of the comparator 420 is in a high state, the AC sense signal 440 can also remain in a high state. The high state of the AC sense signal 440 can be received by a metrology processor (e.g., metrology processor 345) as an indication of a loss of AC line voltage.

[0044] Other circuits configured to detect the presence and absence of an AC line voltage and generate a corresponding sense signal may also be used without departing from the scope of this disclosure.

[0045] The output signal 426 of the comparator 420 may also be received by the power supply control circuit 450. The power supply control circuit 450 may include a diode D2, a capacitor C1, a resistor R1, and a first circuit M1. The first circuit M1 may be, for example, a metal oxide field effect transistor, a logic circuit, or other type of transistor or circuit. When the AC line voltage is present, the output signal 426 of the comparator 420 may change state between a high state and a low state, as described above. The diode D2 causes the signal 451 at the anode of the diode D2 to switch between a low state of approximately 0 volts and a high state of approximately an HVDC voltage level (e.g., approximately 12V HVDC generated by the offline switching power supply 310), resulting in a square wave signal having approximately the same frequency as the frequency of the AC line voltage.

[0046] The time constant provided by R1 and C1 discharges C1 through comparator 420 each time the output signal 426 of comparator 420 switches to a low state, thereby preventing the gate drive signal 452 for M1 from reaching a high enough voltage to turn on circuit M1. When M1 is maintained in an off state, the power supply control signal 453 is maintained in a high state. The power supply control signal 453 may be the power supply control signal 356 shown in FIG. 3. The power supply control signal 453 may be received by a second regulated power supply (e.g., second regulated power supply 325) to maintain operation of the second regulated power supply.

[0047] As described above, in the event of an AC power outage, the output signal 426 of the comparator 420 may stop changing state and remain in a high state. When the output signal 426 of the comparator 420 is in a high state, the capacitor C1 may charge to a voltage level high enough to generate the gate drive signal 452 to turn on the first circuit M1. When the first circuit M1 turns on, the power supply control signal 453 may change to a low state to stop the operation of the second regulated power supply. The charging of the capacitor C1 may be delayed by resistor R1, thereby delaying the turn-on of the first circuit M1 and the change in state of the power supply control signal 453. To complete a power loss operation, the metrology processor may require the second regulated power supply to continue supplying power.

[0048] Although the operation of the power control circuit has been described using transistor examples, other circuits (not limited to logic devices) can be used to perform similar functions without departing from the scope of the present disclosure.

[0049] According to aspects of the disclosure, a metrology processor (e.g., metrology processor 345) can generate a power hold-up signal 456 to allow the metrology processor to complete a power loss operation. The power hold-up signal 456 can be the power hold-up signal 354 shown in FIG. 3. The high state of the power hold-up signal 456 can be received by a power hold-up circuit 455. The power hold-up circuit 455 can include a second circuit M2. The second circuit M2 can be, for example, a metal oxide field effect transistor, a logic circuit, or other type of transistor or circuit. The high state of the power hold-up signal 456 can be applied as a gate drive signal to a gate of the circuit M2 to turn on the circuit M2.

[0050] Although the operation of the power supply hold up circuit has been described using transistor examples, other circuits (not limited to logic devices) can be used to perform similar functions without departing from the scope of this disclosure.

[0051] When circuit M2 is turned on, pull-down signal 457 is generated to hold the gate of circuit M1 in a low state, allowing circuit M1 to be turned off. When circuit M1 is turned off, power supply control signal 453 remains in a high state, maintaining operation of the second regulated power supply to power the measurement processor. Thus, in the event of AC power loss, power supply hold-up signal 456 generated by power supply hold-up circuit 455 can override output signal 426 from comparator 420 to prevent shutdown of the second regulated power supply and the measurement processor.

[0052] When the metrology processor has completed performing the power loss operation, the metrology processor may generate a low power hold up signal 456. The low power hold up signal 456 may be received by a power hold up circuit 455. The low power hold up signal 456 may be applied as a gate drive signal to the gate of circuit M2 to turn circuit M2 off. When circuit M2 is turned off, capacitor C1 may charge to a voltage level high enough to generate a gate drive signal 452 that turns on the first circuit M1.

[0053] When the first circuit M1 is turned on, the power supply control signal 453 can change to a low state to stop operation of the second regulated power supply. Shutting down the second regulated power supply (e.g., second regulated power supply 325) eliminates all additional current drawn by the second regulated power supply and all auxiliary circuits (e.g., auxiliary circuit 340) (including the metering processor) energized by the second regulated power supply, conserving energy that can be used for last-gasp communication with the AMI / AMR radio. When the energy stored in the electric meter, e.g., capacitor 270, is depleted, the offline switching power supply (e.g., offline switching power supply 310) and the remaining circuits in the electric meter can stop operation.

[0054] When the AC line voltage is restored, the offline switching power supply can resume operation and generate the HVDC voltage (e.g., 12V or other voltage). The AC sense circuit 410 of the AC detection circuit 400 receives a representation of the AC line voltage and a representation of the HVDC voltage at a comparator 420 such that the output signal 426 of the comparator 420 can generate a square wave as described above. The output signal 426 of the comparator 420 is applied to the cathode of a diode D2 of the power supply control circuit 450 such that a signal 451 at the anode of the diode D2 can be switched between a low state of approximately 0 volts and a high state of approximately the HVDC voltage level.

[0055] The time constant provided by R1 and C1 discharges C1 through comparator 420 each time output signal 426 of comparator 420 switches to a low state, thereby preventing gate drive signal 452 for M1 from reaching a high enough voltage to turn on circuit M1. With M1 maintained in the off state, power control signal 453 to the second regulated power supply (e.g., second regulated power supply 325) is maintained in a high state, allowing the second regulated power supply to resume operation and provide power to auxiliary circuitry 340, including metrology processor 345.

[0056] Although the signals provided to and generated by AC sense circuit 410, power supply control circuit 450, and power supply hold up circuit 455 are described in terms of high and low states, it will be understood that the designations of high and low states are relative and signals having different states may be used without departing from the scope of the present disclosure. Additionally, logic and voltage levels may be manipulated throughout the implementation based on component selection.

[0057] Circuits M1 and M2 may be implemented with various transistor types or other switching components may be used without departing from the scope of this disclosure. For example, logic functions such as sensing AC line voltage and generating signals to switches may be implemented using logic gates or other discrete components in combination with or in place of a processor without departing from the scope of this disclosure. Values ​​of passive components (e.g., resistors and capacitors) may be manipulated to provide desired timing and performance over temperature and various operating voltages without departing from the scope of the invention.

[0058] Although the power supply hold up signal 456 is described as being generated by the metrology processor, it will be appreciated that another component or circuit may generate the power supply hold up signal, including a delay circuit. For example, the delay circuit may be configured to prevent shutdown of the second regulated power supply until the delay circuit detects that the power loss operation is complete.

[0059] 5 is a flow chart illustrating an example of a method 500 for operating an electric meter upon loss of AC power, according to an embodiment of the disclosure. Referring to FIG. 5, at block 510, a loss of AC line voltage can be detected. An AC sense circuit of the AC detection circuit can monitor the AC line voltage of the power grid. The AC sense circuit can generate an AC sense signal 440 that is transmitted to a metrology processor (e.g., metrology processor 345). The AC sense signal 440 can be a time-varying signal when the presence of AC line voltage is detected, or a DC signal when the absence of AC line voltage is detected.

[0060] At block 520, a signal indicative of the absence of AC line voltage can be generated. When the AC sense circuit detects the absence of AC line voltage, a first signal 426 can be generated to a power control circuit (e.g., power control circuit 450) of the AC detection circuit 400. The first signal 426 can be, for example, a DC signal indicative of the absence of AC line voltage. The first signal 426 can also be sent to the metrology processor 345 to transition the AC sense signal 440 to a DC signal indicative of the absence of AC line voltage.

[0061] In block 530, a signal can be generated to shut down the power supply. Based on receiving the first signal from the AC sense circuit, the power supply control circuit can generate a second signal 451 to the anode of the diode D2. The second signal 451 can be a DC signal that starts charging the capacitor C1 to a voltage that can turn on the first switch M1. Once the capacitor C1 is charged to a voltage sufficient to turn on the first switch M1, the power supply control signal 453 sent to the second regulated power supply 325 can transition from a high state to a low state to shut down the power supply. The second regulated power supply 325 can be configured to provide power to the metrology processor 345. Thus, shutting down the second regulated power supply 325 can shut down the metrology processor 345 and any additional circuitry powered by the second regulated power supply 325. The generation of the shutdown signal to the power supply can be delayed by an RC circuit in the power supply control circuit.

[0062] At block 540, a signal can be generated to a power hold-up circuit of the AC detection circuit. In response to receiving the first signal 426, the metrology processor 345 can generate a third signal (e.g., a high state of power hold-up signal 456) to a power hold-up circuit (e.g., power hold-up circuit 455) of the AC detection circuit to prevent shutdown of the second regulated power supply 325.

[0063] In block 550, a signal to the power control circuit can be generated. In response to receiving the power hold up signal 456, the power hold up circuit 455 can generate a fourth signal (e.g., pull down signal 457 in a low state) to the power control circuit 450. The high state of the power hold up signal 456 can cause a switch element (e.g., but not limited to, a transistor) in the power hold up circuit to change state of an output signal to generate the pull down signal 457 in a low state.

[0064] In block 560, a signal can be generated to maintain operation of the power supply. In response to receiving the pull-down signal 457 in a low state, the power supply control circuit can generate a fifth signal (e.g., power supply control signal 453 in a high state) to the second regulated power supply 325. The fifth signal (e.g., power supply control signal 453 in a high state) can be configured to maintain operation of the second regulated power supply 325 and enable the metrology processor 345 to complete the power loss operation. The fourth signal (e.g., pull-down signal 457) can override the second signal (e.g., signal 451 at the anode of diode D2) upon loss of AC line voltage.

[0065] At block 570, a signal can be generated to the power supply hold up circuitry indicating that the power loss operation is complete. Upon completion of the power loss operation, the metrology processor 345 can generate a sixth signal (e.g., a low state of the power supply hold up signal 456) to the power supply hold up circuitry 455 indicating that the metrology processor has completed the power loss operation.

[0066] In block 580, a signal can be generated to the power supply control circuit to allow the power supply to be shut down. In response to receiving the power supply hold up signal 456 in a low state, the power supply hold up circuit can generate a seventh signal to the power supply control circuit. The seventh signal can be the release of the pull down signal 457 from a low state, thereby allowing the second signal (e.g., signal 451 at the anode of diode D2) to control the first circuit M1. The sixth signal can change the state of an output signal of a switch element M2 (e.g., but not limited to, a transistor, etc.) of the power supply hold up circuit, thereby generating the seventh signal. The seventh signal can release control of the power supply control circuit by the power supply hold up circuit.

[0067] In block 590, a signal can be generated to shut down the power supply. In response to receiving the seventh signal from the power supply hold up circuit, the power supply control circuit can generate an eighth signal (e.g., power supply control signal 453 in a low state) to second regulated power supply 325, thereby shutting down the power supply. The eighth signal allows an RC circuit in the power supply control circuit to charge up to a voltage sufficient to change the state of the switch element, thereby generating the eighth signal.

[0068] The specific operations illustrated in FIG. 5 provide a particular method of operating an electric meter upon loss of AC power in accordance with an embodiment of the present disclosure. Other sequences of operations may be performed in accordance with alternative embodiments. For example, the operations described above may be performed in a different order in alternative embodiments of the present disclosure. Additionally, each operation illustrated in FIG. 5 may include multiple sub-operations that may be performed in various sequences as appropriate for the individual operation. Additionally, additional operations may be added or removed depending on the particular application.

[0069] The examples and embodiments described herein are for illustrative purposes only. Various modifications or variations therein will be apparent to those skilled in the art. These are intended to be included within the spirit and scope of this application and the scope of the appended claims.

Claims

1. 1. An alternating current (AC) line voltage detection circuit, comprising: an AC sense circuit; A power supply control circuit; a power supply hold-up circuit; the AC sense circuit is configured to generate a signal to the processor and power control circuit in response to detecting the absence of AC line voltage; In response to receiving the signal from the AC sense circuit, the power supply control circuit is configured to generate a control signal to the power supply to shut down the power supply; the power supply is configured to provide power to the processor; In response to receiving a signal from the AC sense circuit, the processor is configured to generate a signal to a power supply hold up circuit; In response to receiving a signal from the processor, the power supply hold up circuit is configured to generate a signal to the power supply control circuitry to prevent shutdown of the power supply; The signal generated by the power supply hold up circuit overrides the signal from the AC sense circuit; The processor further includes an AC line voltage detection circuit configured to generate a subsequent signal to the power supply hold up circuit that allows the power supply and the processor to shut down.

2. the AC sense circuit is configured to sense the presence or absence of an AC line voltage and generate a signal to the processor; in response to detecting the presence of the AC line voltage, the AC sense circuit is configured to generate a first signal to the processor and a second signal to the power supply control circuit; 2. The AC line voltage detection circuit of claim 1, wherein in response to detecting the absence of the AC line voltage, the AC sense circuit is configured to generate a third signal to the processor and a fourth signal to the power supply control circuit.

3. the first signal and the second signal are time-varying signals; 3. The AC line voltage detection circuit of claim 2, wherein the third signal and the fourth signal are DC signals.

4. The power supply control circuit includes a first circuit connected to a resistor-capacitor (RC) circuit and a diode; In response to receiving a second signal from the AC sense circuit, the RC circuit and the diode maintain the first circuit in a first state; 3. The AC line voltage detection circuit of claim 2, wherein the first circuit in the first state sends a signal to the power supply to maintain power supply operation.

5. in response to receiving a fourth signal from the AC sense circuit, the RC circuit and the diode maintain the first circuit in the second state; 5. The AC line voltage detection circuit of claim 4, wherein the first circuit in the second state sends a signal to the power supply to shut down operation of the power supply.

6. 5. The AC line voltage detection circuit of claim 4, wherein the first circuit is a logic circuit or a transistor.

7. in response to receiving the third signal from the AC sense circuit, the processor or the delay circuit is configured to generate a signal to the power supply hold up circuit; 5. The AC line voltage detection circuit of claim 4, wherein the signal to the power supply hold up circuit overrides a third signal from the AC sense circuit to prevent the power supply from shutting down.

8. the power supply hold-up circuit comprises a second circuit; in response to receiving a signal from the processor or the delay circuit, the second circuit is configured to change from a first state to a second state; 8. The AC line voltage detection circuit of claim 7, wherein in the second state, the second circuit is configured to generate a signal to the power supply control circuit that overrides the second signal from the AC sense circuit.

9. 9. The AC line voltage detection circuit of claim 8, wherein the second circuit is a logic circuit or a transistor.

10. 8. The AC line voltage detection circuit of claim 7, wherein the processor is configured to generate the signal to a power supply hold-up circuit during a period when the processor completes a power loss operation.

11. 11. The AC line voltage detection circuit of claim 10, wherein the power loss operations include one or more of: a) performing voltage or current measurements, or both; b) processing data related to the loss of AC power; or c) transmitting data to a radio of the electric meter for subsequent transmission to a head-end system.

12. An electricity meter, a processor configured to control operation of a portion of the circuitry of the electricity meter; a power supply configured to provide power to the processor; an alternating current (AC) line voltage detection circuit including an AC sense circuit, a power supply control circuit, and a power supply hold-up circuit; the power supply control circuit is configured to generate a signal to the power supply based on the signal received from the AC sense circuit and the signal received from the power supply hold-up circuit; An electricity meter in which the signal generated by the power supply control circuitry maintains operation of the power supply or shuts it down according to signals received from the AC sense circuitry and the power supply hold-up circuitry.

13. 13. The electric meter of claim 12, wherein the AC sense circuit is configured to generate a first signal to the processor and power control circuit when an AC line voltage is detected and to generate a second signal to the processor and power control circuit when an AC line voltage is not detected.

14. 14. The electricity meter of claim 13, wherein the first signal is a time-varying signal and the second signal is a direct current (DC) signal.

15. The power supply control circuit includes a first circuit connected to a resistor-capacitor (RC) circuit and a diode; the RC circuit and the diode are configured to maintain the first circuit in a first state upon receiving a first signal from the AC sense circuit; 14. The electric meter of claim 13, wherein the first circuit in the first state is configured to send a signal to the power supply to maintain power supply operation.

16. the RC circuit and the diode are configured to maintain the first circuit in a second state upon receiving a second signal from the AC sense circuit; 16. The electric meter of claim 15, wherein the first circuit in the second state sends a signal to the power supply to shut down operation of the power supply.

17. 16. The electricity meter of claim 15, wherein the first circuit is a logic circuit or a transistor.

18. In response to receiving the second signal from the AC sense circuit, the processor or delay circuit is configured to generate a signal to the power supply hold up circuit; 14. The electric meter of claim 13, wherein the signal to the power supply hold up circuit is configured to override a second signal from the AC sense circuit and prevent the power supply from shutting down.

19. the power supply hold-up circuit comprises a second circuit; in response to receiving a signal from the processor, the second circuit is configured to change from a first state to a second state; 20. The electric meter of claim 18, wherein in the second state, the second circuit is configured to generate a signal to the power control circuit that overrides the second signal from the AC sense circuit.

20. 20. The electricity meter of claim 19, wherein the second circuit is a logic circuit or a transistor.

21. 20. The electricity meter of claim 18, wherein the processor or delay circuit is configured to generate the signal to the power supply hold up circuit during a period when the processor completes a power loss operation.

22. 22. The electric meter of claim 21, wherein the loss of power operations include one or more of: a) performing voltage or current measurements, or both; b) processing data related to the loss of AC power; or c) transmitting data to a radio of the electric meter for subsequent transmission to a head-end system.

23. 1. A method for operating an electricity meter during a loss of alternating current (AC) power, comprising: detecting the absence of AC line voltage with an AC sense circuit; generating a first signal indicative of a sensed loss of AC line voltage by the AC sense circuit to a processor and power control circuit; generating, by a power supply control circuit, a second signal configured to shut down the power supply, the second signal being generated after a delay time, and the power supply being configured to provide power to the processor; generating, by the processor, a third signal to a hold-up circuit in response to receiving the first signal, the third signal preventing shutdown of the power supply; in response to receiving the third signal, generating, by the hold-up circuit, a fourth signal to the power control circuit prior to expiration of the delay time; generating, by the power supply control circuitry in response to receiving the fourth signal, a fifth signal to the power supply, the fifth signal configured to maintain operation of the power supply and to enable the processor to complete a power loss operation, the fourth signal overriding the second signal upon loss of AC line voltage; generating, by the processor, upon completion of the power loss operation, a sixth signal to the hold-up circuit indicating that the processor has completed the power loss operation; generating, by the hold-up circuit, a seventh signal to the power control circuit in response to receiving the sixth signal, the seventh signal causing the power control circuit to be controlled by the first signal; generating, by the power supply control circuitry in response to receiving the seventh signal, an eighth signal to the power supply, the eighth signal causing the power supply to shut down; A method of shutting down a power supply, thereby shutting down a processor and other circuitry energized by the power supply.

24. 24. The method of claim 23, wherein the power loss operations include one or more of: a) performing measurements of voltage or current or both; b) processing data related to the loss of AC power; or c) transmitting data to a radio of the electric meter for subsequent transmission to a head-end system.

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