Patent Description:
In some implementations, AC mains power, or a derivative thereof (e.g., power from a step-down transformer), provides power to multiple circuits of an electronic device and/or system simultaneously. These multiple circuits or sub-circuits may be implemented separate from one another, such that communication is limited between the circuits. Further, some remote circuits may be configured to implement various system operations without inter-circuit communication capabilities. As such, when one of the multiple circuits fails to operate as expected, the other circuits or a controller of the electronic system may not be aware of the circuit failure (e.g., partial failure, complete failure), a condition of the failing circuit, or the failing circuit may cause power issues (e.g., brownouts) in the other circuits or the controller. An electronic system that partially functions, or functions on an intermittent basis, often leads to user frustration and results in a poor user experience. <CIT> describes a power supply circuit and air conditioner having the same. <CIT> describes a power-supply device, <CIT>relates to a chime control companion and communication, and <CIT> concerns a doorbell chime bypass circuit.

The invention is set forth in claim <NUM>. Specific embodiments are presented in the dependent claims. This document describes systems and techniques for alternating-current (AC) power harmonic-based circuit state detection. According to claim <NUM>, a system includes a passive component, a bypass circuit for the passive component, and a controller with an AC power harmonic-based circuit state detector that can determine a state of the bypass circuit. In some cases, the system is configured as a video-recording doorbell system in which the passive component includes a solenoid of a doorbell chime, and the bypass circuit includes a bypass device that bypasses the solenoid to allow AC power to flow directly to a controller of the video-recording doorbell system. The AC power harmonic-based circuit state detector is configured to convert an AC voltage of the AC power to a direct current (DC) voltage and filter the DC voltage to obtain a voltage of a harmonic of the AC power. The detector can then compare the voltage of the harmonic to a threshold to determine that the bypass circuit is in a fault state (e.g., fuse blown). By so doing, the controller of the system can notify a user that the bypass circuit needs to be reset or replaced to restore operation of the system and avoid poor user experience typically associated with a non- or mis-functioning system.

Specifically, the system of claim <NUM> includes a first current input/output (I/O) node configured to receive AC power, a second current I/O node configured to receive the AC power, and a passive component having a first terminal coupled to the first current I/O node. The system also includes a bypass circuit that includes a first terminal coupled to the first terminal of the passive component, a second terminal coupled to a second terminal of the passive component, and a switch coupled between the first terminal and second terminal of the bypass circuit. A controller of the system has a first terminal coupled to the second terminal of the passive component and the second terminal of the bypass circuit, a second terminal coupled to the second current I/O node, and an AC power harmonic-based circuit state detector. The AC power harmonic-based detector is configured to convert an AC voltage of the AC power received at the first terminal and second terminal of the controller to a DC voltage, filter the DC voltage to obtain a voltage of a harmonic of the AC power received at the first terminal and the second terminal of the controller, compare the voltage of the harmonic of the AC power to a voltage threshold, and determine a state of the bypass circuit based on the comparison of the voltage of the harmonic of the AC power to the voltage threshold.

A method (not claimed) includes receiving AC power from a circuit that includes a bypass circuit for a component of the circuit. The method then converts an AC voltage of the AC power to a DC voltage and filters the DC voltage to obtain a voltage of a harmonic of the AC power received from the circuit. The voltage of the harmonic is then compared to a voltage threshold and a state of the bypass circuit is determined based on the voltage of the harmonic exceeding the voltage threshold. Additionally, the method may include alerting a service provider or user of a system that includes the circuit to a fault condition of the bypass circuit when detected as the state of the bypass circuit.

The details of one or more implementations are set forth in the accompanying Drawings and the following Detailed Description. Other features and advantages will be apparent from the Detailed Description, the Drawings, and the Claims. This Summary is provided to introduce subject matter that is further described in the Detailed Description.

The details of one or more aspects of AC power harmonic-based circuit state detection are described in this document with reference to the following Drawings, in which the use of same numbers in different instances may indicate similar features or components:.

In implementations where mains power, or a derivative thereof (e.g., power from a step-down transformer), provides power to separate circuits or components of an electronic system simultaneously, the circuits or components may have limited or no communication between the circuits. Further, some remote circuits or components may be configured to implement various circuit operations without inter-circuit communication capabilities. As such, when one of the multiple circuits fails to operate as expected, the other circuits or controllers of the electronic system may not be aware of the circuit failure (e.g., partial failure, complete failure), a condition of the failing circuit, or the failing circuit may cause power issues (e.g., brownouts) for the other circuits or the controller of the system. An electronic system that partially functions, or functions on an intermittent basis, often leads to user frustration and results in a poor user experience.

This document describes systems and techniques for AC power harmonic-based circuit state detection that may enable a controller of a system to detect a fault in a circuit of the system and notify a user of the fault, thereby avoiding poor user experience associated with a nonfunctional system. Generally, the described examples enable a controller of a system or circuit to determine a state of a component or circuit of the system based on a harmonic of AC power that passes through or diverts around the component or the circuit. Although reference herein is made to a video-recording doorbell system, the described example may be applied to any system or circuit that shares or has access to AC power provided to components of the system or circuit.

In AC power harmonic-based circuit state detection, an electronic system may be configured as a video-recording doorbell system that is configured to couple to an AC-based system of a doorbell chime, which may be found in many homes. Although described in reference to a video-recording doorbell, the examples described herein may apply to any AC-based electronic system, which may include a thermostat, a garage door opener, an intercom system, a lighting controller, a smart electric panel (and breakers thereof), a smoke detector, an Internet-of-Things (IoT) device, a smart appliance, and so forth. Generally, a system configuration of the doorbell system may include a puck or doorbell bypass device that is coupled in parallel with a chime component of the doorbell and a user device, which includes a camera, microphone, and wireless transceivers, that couples in series with the chime and bypass device (or bypass circuit). Typically, the user device may couple into the AC wiring where a traditional doorbell button (e.g., normally open switch) is placed near an entry door of a residence. In normal operation, an AC current flows through the doorbell bypass device to the video doorbell user device. In most cases, the doorbell bypass device includes a normally closed (N. ) switch to selectively bypass a solenoid of the chime when closed or to short the AC current through the solenoid of the chime when closed to cause the chime to ring. Further, the video doorbell user device can include a normally open switch (N. ) switch to selectively lead the AC current into power circuitry of the user device to power the user device when open or to short the AC current through the solenoid of the chime when closed.

In some cases, a fault occurs within circuitry of the bypass device, which prevents the bypass circuitry from causing the AC current to bypass the chime component. Thus, the AC current flows through the solenoid or coil of the chime component, which has a higher impedance than the switch circuitry of the bypass device (e.g., on-resistance of the switch plus resistance of a current-limiting resistor). This increase of impedance in the power circuit of the video doorbell user device may introduce a voltage drop or distortion of the AC voltage of the AC power received at the user device, which pollutes the AC power quality. Although the video doorbell user device may still partially operate on the low or polluted AC power supply, without a functional bypass device, function of the video doorbell system may be impaired. For example, the video doorbell device may brownout due to low voltage or lack of power, the chime component may no longer ring, or the redirected current may cause buzzing or other indeterminate system behavior that results in a poor user experience. As described herein, AC power harmonic-based circuit state detection may use characteristics of the polluted AC power supply to detect failure of the bypass device or other AC-based system circuitry, which may enable the issuance of system or user alerts to address a fault condition of the bypass device (or another circuit) to restore operation of the video doorbell system.

Generally, when AC power quality is polluted due to increased circuit impedance (e.g., AC current through chime solenoid), the pollution specifications include total harmonic distortion (THD), as well as individual order of harmonics. As described herein, AC power harmonic-based circuit state detection may use THD or an individual order of harmonics to detect a state of a circuit. In such cases, the described examples may implement low-cost and/or low-power analog circuitry to obtain and use an individual order of harmonics to detect a state of the circuit instead of attempting to compute the total harmonic distortion of the AC power supply using the computational power of the user device's processor, which consumes more power and adds to the computation load of the video doorbell user device. Thus, AC power harmonic-based circuit state detection can be implemented at least partially in analog circuitry to detect a fault in a bypass device with reduced cost, lower power consumption, and without increasing the computational load of the user device processor.

A harmonic-based circuit state detector may measure or use the polluted power quality (e.g., THD or harmonic of voltage) as criteria to detect a particular state or a fault of a circuit (e.g., bypass device). As noted, when the bypass device of the video doorbell system enters a fault state, the AC current can flow through the chime component to the user device of the video doorbell. In accordance with one or more examples, the user device may include a sensing bridge coupled between power-input terminals of the user device to sense or rectify the distorted AC voltage of the AC power. For example, the sensing bridge may convert the AC voltage into DC voltage through diode-based rectification. The DC voltage is then sent to a filter circuit to extract a harmonic (e.g., a <NUM>th-order harmonic) of the AC power entering the user device. A comparator of the user device compares a voltage magnitude of the extracted harmonic to a reference voltage and provides an output based on that comparison to the processor of the user device. In response to detecting a fault based on the comparison, the processor can initiate a system alert or user alert to notify the user of the fault in the bypass device. Alternatively or additionally, a device may use an amount or level of THD present in AC power received by the device to determine a state of an AC power source or a state of a circuit associated with the AC power source.

A system includes a passive component, a bypass circuit for the passive component, and a controller with an AC power harmonic-based circuit state detector that is configured to determine a state of the bypass circuit. In some cases, the system is configured as a video-recording doorbell system in which the passive component includes a solenoid of a doorbell chime, the bypass circuit includes a bypass device that bypasses the solenoid to allow AC power to flow directly to a controller of the video-recording doorbell system. The AC power harmonic-based circuit state detector is configured to convert an AC voltage of the AC power to a direct current (DC) voltage and filter the DC voltage to obtain a voltage of a harmonic of the AC power. The detector can then compare the voltage of the harmonic to determine that the bypass circuit is in a fault state (e.g., fuse blown). Alternatively or additionally, the AC power harmonic-based circuit state detector may determine an amount of THD present in the AC voltage and compare the amount of THD to a threshold to determine a state of the bypass circuit. By so doing, the controller of the system can notify a user that the bypass circuit needs to be reset or replaced to reenable operation of the system and avoid poor user experience typically associated with a non- or mis-functioning system.

Aspects of AC power harmonic-based circuit state detection may be implemented with or using low-power analog circuitry. Thus, in some aspects, a harmonic-based circuit state detector may include a diode-based sensing bridge, an analog filter circuit, and/or hardware-based comparator for signal processing, all of which consume low levels of power. Additionally, small package versions of these components can be selected to save board space on the printed circuit board (PCB) of a user device of a video-recording doorbell system. Further, the use of analog circuitry for circuit fault or state detection in accordance with various aspects does not increase computational load on the processor of the user device. Thus, the described aspects can be implemented at least partially in analog circuitry to enable detection of a fault in the bypass device with low cost, low power consumption, and without increasing computational load of the user device processor. Additionally, the use of analog components may enable aspects of AC power harmonic-based circuit state detection in devices with processors (e.g., low-power processor or microcontrollers) that are unable to filter and/or compare voltage levels. In other implementations, aspects of AC power harmonic-based circuit state detection may be implemented at least partially by a processor or system-on-chip (SoC) of the video-recording doorbell system. For example, an SoC of a video-recording doorbell may determine a level of THD present in AC supply voltage based on rectified and/or filtered voltage received at an input of the SoC. The SoC may then compare the level of THD to a threshold to determine a state of the bypass device or AC power supply from which the AC power is received.

The following discussion describes operating environments, systems, and techniques that may be employed in or by the operating environments, example systems, example methods, and example devices. Although systems and techniques for implementing AC power harmonic-based circuit state detection are described, it is to be understood that the subject of the appended claims is not necessarily limited to the specific features or methods described, but it is defined by the wording of the claims, which limits the scope of protection. Rather, the specific features and methods are described as example implementations, and reference is made to the operating environment by way of example only.

<FIG> illustrates an example operating environment <NUM> in which various aspects of AC power harmonic-based circuit state detection can be implemented. Generally, the example environment <NUM> includes an electronic system <NUM>, which may include a video-recording doorbell or any other type of electronic system that receives power from AC mains or a similar power source. For example, the electronic system <NUM> may include a thermostat, a garage door opener, an intercom system, a lighting controller, a smart electric panel (and breakers), a smoke detector, an Internet-of-Things (IoT) device, a smart appliance, or the like. The electronic system <NUM> includes a bypass circuit <NUM> or bypass device <NUM> that enables AC current to bypass a component or portion of the circuitry of the electronic system. In alternate configurations, such as a thermostat or smart electric panel, the electronic system may not include a bypass device and be configured to monitor AC power received by the system at one or more points. For example, a smart electric panel may include at least three terminals to monitor AC power quality between a first leg/phase, a second leg/phase, a neutral, and/or a ground reference. In yet other implementations, the electronic system may include a power grid-monitoring device, a solar inverter, a home battery storage system, a gas generator, or any other type of AC regenerative source. Thus, aspects of AC power harmonic-based circuit state detection may apply to phase-to-neutral measurements, phase-to-phase measurements, or phase-to-ground measurements when extracting a harmonic of AC power for comparison by a controller of the electronic system. Further, although described with reference to harmonics, the aspects described herein may also determine a level or amount of THD in received power to implement techniques of circuit state detection or determination of AC power characteristics.

<FIG> shows a right-front perspective view of an example implementation of a bypass circuit <NUM> that is enclosed to form a bypass device <NUM> that includes hooked terminals. In some cases, the bypass device <NUM> is implemented as a "puck" that is electrically coupled to a doorbell electro-mechanical assembly that includes wiring to a step-down transformer and one or more doorbell switches, as well as chimes and solenoid to produce one or more tones when activated via switched AC current. The bypass device <NUM> includes a first current input/output (I/O) node <NUM>-<NUM> (e.g., conductor, wire) and a second current I/O node <NUM>-<NUM> (e.g., conductor, wire). The first current I/O node <NUM>-<NUM> and the second current I/O node <NUM>-<NUM> may include electrically conductive wires or cables (e.g., a group or bundle of wires inside a common sheathing). The wires can be solid wires or stranded wires of any one of a variety of gauges (e.g., diameters) and electrically conductive materials (e.g., copper, aluminum). The cables can include two or more insulated phase line wires, an insulated or bare ground wire, a bare neutral wire, or any combination thereof. The sheathing is an electrically insulating material and can include any one of a variety of insulating materials, including thermoplastic, heat-resistant plastic, flame-retardant synthetic polymer, oil- and gasoline-resistant nylon, or the like.

<FIG> also illustrates that the first current I/O node <NUM>-<NUM> and the second current I/O node <NUM>-<NUM> include hook-shaped terminals <NUM>-<NUM> on one end and enter a housing <NUM> on an opposite end through an opening <NUM>. Alternatively, as shown, the first current I/O node <NUM>-<NUM> and the second current I/O node <NUM>-<NUM> can be implemented with Y-shaped terminals <NUM>-<NUM> on one end and enter the housing on an opposite end through the opening <NUM>. Although two types of terminals (e.g., hook-shaped terminals <NUM>-<NUM>, Y-shaped terminals <NUM>-<NUM>) are described herein, the current I/O nodes <NUM> can be implemented with terminals of any suitable shape or size appropriate to make an electrically conductive connection to an AC power source. The housing <NUM> may be implemented with a split housing design that includes a top cover, a bottom cover, and a mounting adhesive <NUM> disposed as a bottom layer beneath the bottom cover. The mounting adhesive <NUM> can be any one of a variety of adhesives, including wet adhesive, contact adhesive, reactive adhesive, pressure-sensitive adhesive (PSA), very high bond (VHB) tape, or the like. How the bypass circuit <NUM> and/or bypass device <NUM> may be implemented and used varies and is described throughout this disclosure.

As shown in <FIG>, the electronic system <NUM> also includes a user device <NUM>, which is coupled to an AC power source <NUM> through the bypass circuit <NUM>. An AC step-down transformer <NUM> (AC transformer <NUM>) may step down AC mains voltage of the AC power source <NUM> from a range of <NUM> Volts (V) to <NUM> V AC down to a range of <NUM> V to <NUM> V AC at <NUM>. The electronic system also includes a circuit component <NUM> coupled in series between the AC power source and the user device <NUM>. The circuit component <NUM> includes a passive component, including an inductor, coil, solenoid, or the like. For example, the circuit component <NUM> can include a solenoid that actuates a mechanical assembly of a doorbell chime to produce a multitone ring when activated by the user device <NUM> or doorbell switch. The first current I/O node <NUM>-<NUM> and the second current I/O node <NUM>-<NUM> of the bypass circuit <NUM> (or bypass device <NUM>) are electrically coupled or connected in parallel with a first terminal and a second terminal of the circuit component <NUM> via terminals <NUM>, respectively. Thus, the bypass circuit <NUM> may enable AC current to bypass the circuit component <NUM> to provide power to the user device <NUM> of the electronic system <NUM>. Generally, the circuit component <NUM> has a different or higher electrical impedance than an internal impedance of the bypass circuit <NUM>, such that AC power passing through the circuit component <NUM> has different harmonics or higher total harmonic distortion than AC power passing through the bypass circuit <NUM> (or bypass device <NUM>).

In aspects, the user device <NUM> includes power circuitry <NUM>, system circuitry <NUM>, a processor <NUM>, and a harmonic-based circuit state detector <NUM>. The power circuitry <NUM> can be configured to receive AC power from the AC transformer <NUM> and convert the AC power to direct current (DC) power for components of the user device <NUM>. The system circuitry <NUM> may be configured to enable functionalities of the user device <NUM>, which may include video recording, image capture, audio recording, two-way audio communication, audio or light-based notifications, hardware or touch-sensitive buttons, motion sensors, wireless data communication, and so forth. Thus, although not shown, the system circuitry <NUM> of a user device <NUM> configured as a video-recording doorbell may include a camera system, audio system, communication transceivers, light-emitting diodes, I/O for hardware buttons, or the like. The processor <NUM> may include any number or type of processor cores and other data processing capabilities to enable operation of the user device <NUM>. In some aspects, the processor <NUM> executes processor-executable instructions of an operating system or firmware of the user device <NUM> to implement various operations or functions of the user device <NUM>.

As described herein, the harmonic-based circuit state detector <NUM> is configured to detect or determine a state of the bypass circuit <NUM> or components thereof. As shown in <FIG>, the harmonic-based circuit state detector <NUM> is electrically coupled to power input terminals or the power circuitry <NUM> of the user device <NUM> to receive or sense the AC power received by the user device <NUM>. The harmonic-based circuit state detector <NUM> rectifies AC power received at the user device <NUM> to provide DC power and filters the DC power to obtain a harmonic of the received AC power. The harmonic-based circuit state detector <NUM> can then compare a voltage of the harmonic to a threshold to determine whether the bypass circuit is operating normally to pass clean AC power, such as when the voltage of the harmonic is below the threshold. Alternatively, the harmonic-based circuit state detector <NUM> may determine, in response to the voltage of the harmonic exceeding the threshold, that the bypass circuit <NUM> is in a fault state, thereby directing AC power through the circuit component <NUM> causing polluted AC power to reach the user device <NUM>. Additional examples and implementations of the harmonic-based circuit state detector <NUM> are described throughout this disclosure.

<FIG> illustrates at <NUM> an example component configuration of the electronic system <NUM> of <FIG> in detail and with an example of AC current flow for powering a user device. Generally, the component configuration <NUM> describes components and circuits of an electronic system that implements an AC power harmonic-based circuit state detection. The electronic system may include a bypass device <NUM> and a user device <NUM> configured to implement a video-recording doorbell system with wireless communication capabilities. For the sake of visual brevity, various video and/or audio components may be omitted from <FIG>. The harmonic-based circuit state detector <NUM> associated with a user device <NUM> can determine that the bypass circuit <NUM> or bypass device <NUM> coupled to a doorbell chime (e.g., circuit component <NUM>) is in a fault state or non-operational state. Additionally, the harmonic-based circuit state detector <NUM> may indicate the fault state to the processor <NUM> or an operating system of the user device <NUM>, which may then alert a user or a service provider associated with the user device <NUM> such that the fault state may be addressed.

As shown in <FIG>, various components of the electrical system are coupled to a <NUM> V to 240V source of AC mains power <NUM> through a step-down AC transformer <NUM> that provides AC power at approximately <NUM> V to <NUM> V AC. The described voltage values may be nominal voltage ranges, such that the electronic system may receive AC voltage from <NUM> V to <NUM> V, or a wider range of voltage depending on the condition of the AC mains power <NUM> or a configuration of the step-down transformer <NUM>. In this example, the circuit component <NUM> includes a coil <NUM> of a doorbell chime solenoid, though the described examples may be implemented with any other type of passive component with an impedance that is different from an internal impedance of the bypass circuit <NUM>. A first terminal of the coil <NUM> is electrically coupled to a first leg, phase, or circuit branch of the AC power provided by the AC transformer <NUM> and a second coil of the coil <NUM> is electrically coupled to the user device <NUM>.

To enable current to bypass the coil <NUM>, the bypass circuit <NUM> may be connected in parallel with the coil <NUM> as shown in <FIG>. In aspects, the bypass circuit <NUM> includes a fuse <NUM> (e.g., thermal fuse, positive temperature coefficient (PTC) device) electrically coupled in series with a bypass switch <NUM> and/or a current-limiting resistor <NUM> of the bypass circuit <NUM>. The fuse <NUM> may be configured to protect components of the bypass circuit <NUM>, the user device <NUM>, or other portions of the electrical system (not shown). Although illustrated as a single switch, the bypass switch <NUM> may be implemented as a combination of one or more bypass switches, configured in series, in parallel, or any combination thereof. Furthermore, the bypass switch <NUM> may include a relay, a solid-state relay (SSR), a mechanical switch, a magnetic switch, and so forth. The current-limiting resistor <NUM> can include any number, type, or configuration of resistors, which may include a single resistor, as illustrated, or two or more resistors in parallel, two or more resistors in series, or any combination thereof.

The bypass circuit <NUM> may also include a rectifier <NUM> and power and control circuitry <NUM> (power and control circuitry <NUM>) for operating the bypass switch <NUM>. In some cases, the bypass switch <NUM> is configured as a normally closed (N. ) switch, such that the bypass switch normally enables AC current to flow from the AC transformer <NUM> to the user device <NUM> without passing through the coil <NUM> of the doorbell chime. Thus, the rectifier <NUM> may convert the AC power to DC power by which to operate the power and control circuitry <NUM> of the bypass switch <NUM>. For example, when the bypass switch <NUM> is activated, or opened, the AC current may be directed through the coil <NUM> to allow operation of the doorbell chime. As shown in <FIG>, when bypass switch <NUM> of the bypass circuit <NUM> is closed, the AC current (dashed lines) flows through the fuse <NUM>, bypass switch <NUM>, current-limiting resistor <NUM> to the user device <NUM> while bypassing the coil <NUM> of the doorbell chime.

The user device <NUM> receives AC power from the bypass circuit <NUM> through a first terminal that is electrically coupled to a second terminal of the bypass circuit <NUM> and/or a second terminal of the coil <NUM>. A second terminal of the user device <NUM> is electrically coupled to a second leg, phase, or circuit branch of the AC power provided by the AC transformer <NUM>. The user device <NUM> includes a switch <NUM> to direct the AC current into power circuitry <NUM> of the user device <NUM> (e.g., switch <NUM> open) or through the coil <NUM> (e.g., switch <NUM> closed and bypass switch <NUM> open) to activate or operate the doorbell chime. In some cases, the switch <NUM> is configured as a normally open (N. ) switch, such that the switch <NUM> normally enables AC current to flow from the bypass circuit <NUM> into the power circuitry <NUM> of the user device <NUM> without passing through the coil <NUM> of the doorbell chime. As shown in <FIG>, when the switch <NUM> of the user device <NUM> is open, the AC current (dashed lines) flows into a rectifier circuit <NUM> and AC/DC conversion block <NUM> of the power circuitry <NUM> to provide DC power to system circuitry <NUM>, which includes a doorbell system <NUM> in this example. In what may be referred to as a "normal" mode of operation, this AC current passes from the AC transformer <NUM> through the fuse <NUM>, the bypass switch <NUM>, and the current-limiting resistor <NUM> into the power circuitry <NUM> of the user device <NUM>. Thus, the AC current flow is subject to the combined impedance of the fuse <NUM>, the bypass switch <NUM>, and the current-limiting resistor <NUM>. These switch and current-limiting resistor components typically have a low impedance, such that AC power reaching the user device <NUM> through the bypass circuit <NUM> is clean or at least less polluted or with a lower level of total harmonic distortion than AC power passing through the coil <NUM> of the doorbell chime.

As shown in <FIG>, a harmonic-based circuit state detector <NUM> may be electrically coupled to AC power terminals of the user device <NUM>. Here, a first terminal of the harmonic-based circuit state detector <NUM> is coupled to the first terminal of the user device <NUM> and a second terminal of the harmonic-based circuit state detector <NUM> is coupled to the second terminal of the user device <NUM>. In aspects, the harmonic-based circuit state detector <NUM> may be implemented with a sensing bridge <NUM>, a filter <NUM>, and a comparator <NUM>. Although illustrated with three components or stages, a harmonic-based circuit state detector <NUM> may include additional components or fewer components, including additional power conditioning circuitry, additional filter stages, resistor networks for reference voltage, or the like. In aspects, some or all of the components of the harmonic-based circuit state detector <NUM> are implemented as analog or hardware circuits, which enables the detector to detect or determine circuit states or fault conditions without increasing a computational load on the processor <NUM> of the user device <NUM>.

As described herein, the harmonic-based circuit state detector <NUM> is configured to detect or determine a state of the bypass circuit <NUM> or the components of the bypass circuit <NUM>, which may include the fuse <NUM> or bypass switch <NUM>. The sensing bridge <NUM> rectifies AC power received at the user device <NUM> to provide DC power and the filter <NUM> filters the DC power to obtain a harmonic of the received AC power. The comparator <NUM> then compares a voltage of the harmonic to a threshold to determine whether the bypass circuit <NUM> is operating normally to pass unpolluted AC power, such as when the voltage of the harmonic is below the threshold.

Alternatively, the comparator <NUM> may determine, in response to the voltage of the harmonic exceeding the threshold, that the bypass circuit <NUM> is in a fault state, thereby directing AC power through the coil <NUM> causing polluted AC power to reach the user device <NUM>. In such cases, the redirection of AC current through the coil <NUM> may indicate that the fuse <NUM> is open or that the bypass switch <NUM> and/or the power and control circuitry <NUM> failed to operate properly. In this example, an output of the comparator <NUM> is coupled to an input of a system-on-chip <NUM> (SoC <NUM>) of the user device <NUM> that includes the processor <NUM>. In response to detecting fault state of the bypass circuit <NUM>, the comparator may output a signal or logic level to the SoC <NUM> indicating or alerting the SoC <NUM> of the fault condition. Based on the indication, the SoC <NUM> may then alert a user of the video-recording doorbell that the bypass circuit <NUM> (or bypass device <NUM>) is in a fault state and may need to be reset, repaired, or replaced to restore normal system operation.

<FIG> illustrates at <NUM> the example component configuration of the electronic system of <FIG> with another example of AC current flow for chime operation in accordance with one or more aspects. For visual brevity, components, circuits, or configurations described with reference to <FIG> may be omitted from <FIG> and <FIG>, which generally illustrate same or similar configurations of the bypass circuit <NUM> and user device <NUM>. As described herein, the bypass device <NUM> and the user device <NUM> may be configured to implement a video-recording doorbell system with wireless communication capabilities. To implement some operations, the bypass circuit <NUM> and user device <NUM> may selectively direct current through the coil <NUM> of the solenoid of the doorbell chime assembly (not shown).

As shown in <FIG>, the bypass circuit <NUM> and user device <NUM> may concurrently operate the bypass switch <NUM> and switch <NUM>, respectively, to cause the AC current to flow through the coil <NUM> of the doorbell chime. For example, when the user device <NUM> detects operation of a doorbell switch (e.g., doorbell button, not shown) the doorbell system <NUM>, which may be implemented by or at least partially separate from the SoC <NUM>, closes the switch <NUM> to electrically couple the second terminal of the coil <NUM> to the AC transformer <NUM>. The power and control circuitry <NUM> of the bypass circuit <NUM> can detect, in response to the second terminal of the coil <NUM> being coupled to the transformer <NUM>, a change in input voltage that indicates activation of the doorbell chime. In response to activation of the doorbell chime, the power and control circuitry <NUM> opens bypass switch <NUM> to prevent the flow of AC current through the bypass circuit <NUM> and direct the AC current flow through the coil <NUM> of the doorbell chime as shown by the dashed lines in <FIG>. In this state, the user device <NUM> may operate from local power, which may include a battery or a super capacitor, and disable the harmonic-based circuit state detector <NUM> while the switch <NUM> is closed. After the doorbell chime ringing operation is complete, the power and control circuitry <NUM> can close the bypass switch <NUM>, and the doorbell system <NUM> can open switch <NUM> to return to the current flow shown in <FIG>. The doorbell system <NUM> or SoC <NUM> may also re-enable the harmonic-based circuit state detector <NUM> to resume monitoring the state of the bypass circuit <NUM>.

<FIG> illustrates at <NUM> the example component configuration of the electronic system of <FIG> with yet another example of AC current flow caused by a circuit fault condition in accordance with one or more aspects. For visual brevity, components, circuits, or configurations described with reference to <FIG> may be omitted from <FIG> and <FIG>, which generally illustrate same or similar configurations of the bypass circuit <NUM> and user device <NUM>. As described herein, the bypass device <NUM> and the user device <NUM> may be configured to implement a video-recording doorbell system with wireless communication capabilities. In some cases, a component of the bypass circuit <NUM> may fail and/or prevent AC current from flowing through the bypass circuit <NUM> to the user device <NUM>. For example, as shown at <NUM>, the fuse <NUM> may open resulting in an open circuit condition or fault of the bypass circuit <NUM>. Alternatively, the switch <NUM> and/or power and control circuitry <NUM> may fail in an "open" switch condition, which would also prevent AC current from flowing through the bypass circuit <NUM>. In such cases and as shown by the dashed lines in <FIG>, the AC current may instead flow through the coil <NUM> of the doorbell chime to the AC power terminal of the user device <NUM>. Due to increased or different impedance of the coil <NUM>, the AC power reaching the user device <NUM> may be polluted or have an increased total harmonic distortion. Additionally, a constant flow of the AC current through the coil <NUM> may prevent or impair operation of the doorbell chime. Further, the energized coil <NUM> may cause the doorbell chime to ring, hum, or emit other unintended noise, resulting in user frustration or poor user experience.

The harmonic-based circuit state detector <NUM> detects a circuit state or fault state of the bypass circuit <NUM> based on the harmonics of the AC power received by the user device <NUM>. Here the sensing bridge <NUM> rectifies the polluted AC power received at the user device <NUM> to provide DC power and the filter <NUM> filters the DC power to obtain a harmonic of the received AC power. Due to the increased harmonic distortion caused by the impedance of the coil <NUM>, one or more harmonics of the polluted AC power may have an increased voltage magnitude relative to a corresponding harmonic of clean or unpolluted AC power (e.g., AC power that passes through the bypass circuit <NUM>). The comparator <NUM> then compares a voltage of the harmonic to a threshold to determine whether the bypass circuit <NUM> is operating normally or if the bypass circuit is in a fault state. In the context of this example, the output of the comparator <NUM> indicates to the SoC <NUM> that the bypass circuit <NUM> is in a fault state in response to the voltage of the harmonic exceeding the threshold configured to detect the fault state or other abnormal operation of the bypass circuit <NUM>.

<FIG> illustrates at <NUM> an example implementation of a harmonic-based circuit state detector implemented in accordance with one or more aspects. In this example, the sensing bridge <NUM> includes a diode rectification bridge to rectify the AC power received at the user device <NUM> and the filter includes a bandpass filter to filter out a residual harmonic of the AC power present in the rectified DC power. The filter <NUM> may be configured as any type of filter, which may include a bandpass filter to pass one or more harmonics or a high-pass filter to cut off harmonics below a particular frequency. In some cases, the filter <NUM> includes a bandpass filter that is configured to pass one of any harmonics between a second harmonic and a tenth harmonic of the AC power (e.g., a sixth harmonic). Alternatively or additionally, the filter <NUM> may be configured to pass any multiple of a fundamental frequency (e.g., <NUM> or <NUM>), including <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and so forth. After filtering, the filter <NUM> passes one or more harmonics (e.g., residual harmonics) of the AC power to the comparator <NUM>.

In aspects, the comparator <NUM> can be configured with a threshold to enable the detection of a fault in the bypass circuit <NUM> based on a voltage of the filtered harmonic received from the filter circuit <NUM>. As shown in Table <NUM>. at <NUM>, a reference voltage level for a sixth harmonic may be approximately <NUM> V (e.g., during normal bypass operation) and a voltage level of the sixth harmonic associated with a fault condition may be approximately <NUM> V. As such, the voltage threshold level of the comparator <NUM> may be set from between <NUM> V to <NUM> V to enable the harmonic-based circuit state detector <NUM> to detect a fault of the bypass circuit <NUM>. In some cases, the threshold level of the comparator is set using hardware, which may include a resistor, laser-trimmed resistors, a resistor network, a potentiometer, or the like. Alternatively, the SoC <NUM> may provide a configurable voltage threshold via an analog output, digital-to-analog (DAC) circuit, digital potentiometer, and so forth. In response to the voltage of the harmonic exceeding the threshold, an output <NUM> may transition to an active state to notify the SoC <NUM> or processor <NUM> of the detected fault condition. The SoC <NUM> may then provide an indication <NUM> of the fault condition, which may include a user alert <NUM> of the bypass device fault and/or notification to a service provider associated with the video-recording doorbell system.

By way of example, consider <FIG> in which example plots of electrical power for a bypass device operating in a normal circuit condition and a fault circuit condition are depicted at <NUM> and <NUM>, respectively. In plot <NUM>, waveform <NUM> represents AC current at the user device <NUM> (e.g., doorbell device) and waveform <NUM> represents AC voltage at the user device <NUM>. As shown at <NUM>, the AC voltage waveform <NUM> approximates a sinusoidal waveform that correlates to AC power with a lower level of harmonic distortion. Accordingly, a higher harmonic, such as a sixth harmonic of the AC voltage waveform <NUM>, may have a low voltage magnitude relative to a corresponding harmonic of a polluted AC power supply. In contrast with plot <NUM>, waveforms of plot <NUM> represent AC voltage and AC current of AC power received through a higher impedance path, such as the doorbell chime coil or solenoid when the fuse of the bypass circuit is open. In plot <NUM>, waveform <NUM> represents AC voltage at the user device <NUM> (e.g., doorbell device), waveform <NUM> represents AC current at the user device <NUM>, and waveform <NUM> represents an output of the sensing bridge <NUM> of the harmonic-based circuit state detector <NUM>. Note that the AC voltage waveform <NUM> and the waveform <NUM> of the rectified output of the sensing bridge <NUM> do not approximate a smooth sinusoidal wave due to harmonic distortion caused by the AC current flowing through the coil of the doorbell chime. Thus, a voltage magnitude of the sixth harmonic of the AC voltage <NUM> will exceed the voltage threshold of the comparator <NUM> and the harmonic-based circuit state detector <NUM> will detect that the bypass circuit <NUM> is in a fault condition or inoperable state.

Example methods <NUM> and <NUM> are described with reference to <FIG> and <FIG>, respectively, in accordance with one or more aspects of AC power harmonic-based circuit state detection. Generally, the methods <NUM> and <NUM> illustrate sets of operations (or acts) that may be performed in, but not necessarily limited to, the order or combinations in which the operations are shown herein. Further, any of one or more of the operations may be repeated, combined, reorganized, skipped, or linked to provide a wide array of additional and/or alternate methods. In portions of the following discussion, reference may be made to the environment <NUM> of <FIG>, apparatuses, devices, systems, or configurations of <FIG>, systems of <FIG>, and/or entities detailed in <FIG> or other figures, reference to which is made for example only. The techniques and systems described in this disclosure are not limited to an embodiment or performance by one entity or multiple entities operating on one device or those described with reference to the figures.

<FIG> illustrates an example method <NUM> (not claimed) for implementing AC power harmonic-based circuit state detection in accordance with one or more aspects, including operations performed by a harmonic-based circuit state detector (e.g., the harmonic-based circuit state detector <NUM> of <FIG>). In some aspects, operations of the method <NUM> may be implemented by a controller of a video-recording doorbell system to monitor a state of a bypass circuit and/or notify a user of possible fault conditions of the system.

At <NUM>, a controller of a system receives AC power from a circuit that includes a bypass circuit for a component of the circuit. For example, a video doorbell receives AC power from a step-down transformer through a circuit that includes a bypass puck for a doorbell chime assembly. Thus, the video doorbell receives one leg of the AC power through the bypass puck that is operably coupled to the doorbell chime assembly.

At <NUM>, a harmonic-based circuit state detector associated with the controller converts an AC voltage of the AC power to a DC voltage or a rectified voltage. In some cases, a hardware-based harmonic-based circuit state detector is electrically coupled to AC power terminals or AC power circuitry of the controller. The harmonic-based circuit state detector may include a diode bridge rectification circuit to convert the AC power to the DC power. In aspects, the DC power includes residual harmonics of the AC power received by the controller from the AC power circuit.

At <NUM>, the harmonic-based circuit state detector filters the DC voltage to obtain a voltage magnitude of a harmonic of the AC power received from the circuit. The harmonic-based circuit state detector may implement a bandpass filter or a high-pass filter to obtain the voltage magnitude of the harmonic. The harmonic for which the voltage is obtained may be any suitable harmonic, including a fourth harmonic, a fifth harmonic, a sixth harmonic, a seventh harmonic, and so forth. The harmonic-based circuit state detector may implement a hardware-based filter (e.g., analog circuitry) or digital filter (e.g., of an SoC) to filter the harmonic from the DC voltage. Alternatively or additionally, the harmonic-based circuit state detector filters the DC voltage to obtain multiple harmonics or an indication of THD present in the AC power.

At <NUM>, the harmonic-based circuit state detector compares the voltage magnitude of the harmonic to a voltage threshold. The voltage threshold may be configured to detect a circuit state or fault condition of the bypass circuit of the system. For example, a particular circuit state or a fault condition may divert current through the component instead of the bypass circuit resulting in distortion of the AC power that reaches the controller of the system. To do so, the harmonic-based circuit state detector may include a hardware-based comparator or a digital logic comparator (e.g., in digital logic of an SoC). Alternatively or additionally, the harmonic-based circuit state detector filters compares voltage magnitude of multiple harmonics or a voltage magnitude of THD present in the AC power to a threshold.

At <NUM>, the harmonic-based circuit state detector determines a state of the bypass circuit based on the voltage of the harmonic exceeding the voltage threshold. The harmonic-based circuit state detector may determine that the bypass circuit is in a fault state in response to the voltage of the harmonic exceeding the voltage threshold. For example, a fuse or bypass switch of the bypass circuit may be open, preventing current flow through the bypass circuit and causing the current received at the controller to pass through a high impedance path, which in turn results in the harmonic distortion of the AC power.

<FIG> illustrates an example method <NUM> for detecting a state of a bypass device of a doorbell chime in accordance with one or more aspects, including operations performed by a harmonic-based circuit state detector (e.g., the harmonic-based circuit state detector <NUM> of <FIG>). In some aspects, operations of the method <NUM> may be implemented by a controller of a video-recording doorbell system detect a fault condition of the doorbell chime bypass device and/or notify a user of possible fault conditions of the system.

At <NUM>, a controller receives AC power from a circuit that includes a bypass device for a doorbell chime of a doorbell system. For example, the controller may be a video doorbell that receives one leg of the AC power through the bypass device, which is electrically coupled in parallel with the coil of the doorbell chime.

At <NUM>, a harmonic-based circuit state detector associated with the controller converts AC voltage of the AC power to a DC voltage or rectified voltage. In the context of the present example, the video doorbell may include a diode rectification bridge that is coupled between AC terminal or AC power circuitry of the video doorbell.

At <NUM>, the harmonic-based circuit state detector filters the DC voltage or rectified voltage to obtain a voltage of a harmonic of the AC power received from the doorbell chime or the bypass device. Continuing the present example, a harmonic-based circuit state detector of the video doorbell includes a resistor-inductor-capacitor (RLC) bandpass filter configured to extract a sixth harmonic of the AC power received at the video doorbell.

At <NUM>, the harmonic-based circuit state detector compares the voltage of the harmonic to a threshold configured to detect a fault condition of the bypass circuit of the doorbell chime. In the context of the present example, an SoC of the video doorbell implements a digital comparator to compare the voltage magnitude of the harmonic provided by the hardware filter circuit to a threshold configured to determine if the bypass device of the doorbell system is in a fault state (e.g., blown fuse or N. stuck open).

Optionally at <NUM>, the harmonic-based circuit state detector determines that operation of the bypass device for the doorbell chime is normal. In response to the voltage magnitude of the harmonic not exceeding the threshold, the harmonic-based circuit state detector or SoC may determine that the bypass device of the system is operating normally.

Optionally at <NUM>, the harmonic-based circuit state detector detects a fault condition in the operation of the bypass device for the doorbell chime. In response to the voltage magnitude of the harmonic exceeding the threshold, the harmonic-based circuit state detector or SoC may determine that the bypass device of the system is in a fault state. For example, a fuse or switch in the bypass current path may be open, causing the AC current to divert through the coil of the doorbell chime.

Optionally at <NUM>, the controller provides an alert to a user of the doorbell system that the bypass device is in a fault condition. To alert the user, the SoC or video doorbell may cause an application associated with the video doorbell to warn the user that the bypass device (e.g., door chime puck) is not functioning correctly, and needs to be reset, repaired, or replaced to resume normal operation of the doorbell system.

<FIG> illustrates an example system-on-chip <NUM> (SoC <NUM>) that can implement various aspects of alternating-current (AC) power harmonic-based circuit state detection. The entities or components of the SoC <NUM>, either alone or in combination, may implement one or more aspects of alternating-current (AC) power harmonic-based circuit state detection described with reference to the preceding <FIG>. For example, the SoC <NUM> may implement a digital filter and/or comparator to filter and compare a rectified waveform received from a sensing bridge. The SoC <NUM> may be implemented with any suitable combination of components or elements and may include other components shown or described with reference to any of the other <FIG>.

<FIG> illustrates an example system-on-chip (SoC) that may implement aspects of alternating-current (AC) power harmonic-based circuit state detection to determine that a component or circuit of a system is in a fault state. The SoC <NUM> may be embodied as or within any type of user device (e.g., user device <NUM>), video-recording doorbell system, thermostat, smart electric panel, apparatus, another device, or system as described with reference to <FIG> to implement alternating-current (AC) power harmonic-based circuit state detection in accordance with one or more aspects. Although described with reference to chip-based packaging, the components shown in <FIG> may also be embodied as other systems or component configurations, such as, and without limitation, a Field-Programmable Gate Arrays (FPGA), an Application-Specific Integrated Circuits (ASIC), an Application-Specific Standard Products (ASSP), a digital signal processor (DSP), Complex Programmable Logic Devices (CPLD), a system in package (SiP), package on package (PoP), processing and communication chipset, communication co-processor, sensor co-processor, or the like. In the context of <FIG>, the SoC <NUM> may be coupled with an instance of a harmonic-based circuit state detector <NUM> as described with reference to <FIG>. For example, the harmonic-based circuit state detector <NUM> can be implemented as analog or discrete circuitry operably coupled to an input of the SoC <NUM>.

In this example, the SoC <NUM> includes communication transceivers <NUM> that enable wired or wireless communication of system data <NUM> (e.g., video data, audio data, data scheduled for transmission, packetized, or the like). In some aspects, the communication transceivers <NUM> includes a modem or baseband processor that is configurable to communicate in accordance with various communication protocols and/or in different frequency bands, such as those protocols or frequency bands described throughout this disclosure. The communication transceivers <NUM> may include a transceiver interface (not shown) for communicating encoded or modulated signals with transceiver circuitry, including transmitter chain and receiver chain circuitry, operably coupled with respective antennas.

The system data <NUM> or other system content can include configuration settings of the system or various components, media content stored by the system, and/or information associated with a user of the system. Media content stored on the SoC <NUM> may include any type of recorded audio, video, and/or image data. The SoC <NUM> also includes one or more data inputs <NUM> via which any type of data, media content, signals, and/or inputs can be received, such as circuit state indications, user input, user-selectable inputs (explicit or implicit), or any other type of audio, video, and/or image data received from a content and/or data source. Alternatively or additionally, the data inputs <NUM> may include various data interfaces, which can be implemented as any one or more of a serial and/or parallel interface, a wireless interface, a network interface, and as any other type of communication interface enabling communication with other devices or systems.

The SoC <NUM> includes one or more processor cores <NUM> (e.g., processor <NUM>), which process various computer-executable instructions to control the operation of the SoC <NUM> and to enable techniques for AC power harmonic-based circuit state detection. Alternatively or additionally, the SoC <NUM> can be implemented with any one or a combination of hardware, firmware, or fixed logic circuitry that is implemented in connection with processing and control circuits, which are generally shown at <NUM>. Although not shown, the SoC <NUM> may also include a bus, interconnect, crossbar, or fabric that couples the various components within the system.

The SoC <NUM> also includes a memory <NUM> (e.g., computer-readable media), such as one or more memory circuits that enable persistent and/or non-transitory data storage, and thus do not include transitory signals or carrier waves. Examples of the memory <NUM> include RAM, SRAM, DRAM, NVRAM, ROM, EPROM, EEPROM, or flash memory. The memory <NUM> provides data storage for the system data <NUM>, as well as for firmware <NUM>, applications <NUM>, and any other types of information and/or data related to operational aspects of the SoC <NUM>. For example, the firmware <NUM> can be maintained as processor-executable instructions of an operating system (e.g., real-time OS) within the memory <NUM> and executed on one or more of the processor cores <NUM>.

The applications <NUM> may include a system manager, such as any form of a control application, software application, signal processing and control module, code that is native to a particular system, an abstraction module or gesture module and so on. The memory <NUM> may also store system components or utilities for implementing aspects of AC power harmonic-based circuit state detection, such as a user alert system and a lookup table of voltage thresholds useful for circuit state determination. These entities may be embodied as combined or separate components, examples of which are described with reference to corresponding entities or functionality as illustrated in <FIG>. In some aspects, the harmonic-based circuit state detector <NUM> interacts with the SoC <NUM> to implement aspects of AC power harmonic-based circuit state detection. Although shown as separate from the SoC <NUM>, one or more elements of the harmonic-based circuit state detector may be implemented, in whole or in part, through hardware or firmware of the SoC <NUM>.

In some aspects, the SoC <NUM> also includes additional processors or coprocessors to enable other functionalities, such as a graphics processor <NUM>, audio processor <NUM>, and image sensor processor <NUM>. The graphics processor <NUM> may capture and/or render graphical content associated with a user interface, operating system, or applications of the system-on-chip <NUM>. In some cases, the audio processor <NUM> encodes or decodes audio data and signals, such as audio signals and information associated with audio recorded along with a video by a video-recording doorbell system for playback, upload, or streaming. The image sensor processor <NUM> may be coupled to an image sensor and provide image data processing, video capture, and other visual media conditioning and processing functions.

Claim 1:
A system (<NUM>) comprising:
a first current input/output, I/O, node (<NUM>-<NUM>) configured to receive alternating current, AC, power;
a second current I/O node (<NUM>-<NUM>) configured to receive the AC power;
a passive component comprising a first terminal coupled to the first current I/O node;
a bypass circuit (<NUM>) comprising a first terminal coupled to the first terminal of the passive component, a second terminal coupled to a second terminal of the passive component, and a switch (<NUM>) coupled between the first terminal and second terminal of the bypass circuit (<NUM>); and
a controller comprising a first terminal coupled to the second terminal of the passive component and the second terminal of the bypass circuit (<NUM>), characterized in that the controller further comprises a second terminal coupled to the second current I/O node, and an AC power harmonic-based circuit state detector (<NUM>) configured to:
convert an AC voltage of the AC power received at the first terminal and second terminal of the controller to a direct current, DC, voltage;
filter the DC voltage to obtain a voltage of a harmonic of the AC power received at the first terminal and the second terminal of the controller;
compare the voltage of the harmonic of the AC power to a voltage threshold; and
determine a state of the bypass circuit (<NUM>) based on the comparison of the voltage of the harmonic of the AC power to the voltage threshold.