Patent Application
20100142104
The subject matter of the present invention relates to electronic systems and devices and, more particularly, to electrical protection circuits for electronic systems and devices.
Many household electrical or electronic devices are configured to utilize a standard wall outlet voltage waveform as an input power source, e.g., 110-120 volts AC at 60 Hz in the United States. Oftentimes, the AC input voltage is stepped down to a lower DC voltage using a transformer-based power supply internal to the device. In an electronic device, e.g., a household electric appliance, if a high voltage power wire or other voltage source internal to the electric appliance happens to electrically contact an external conductive surface of the device such as a metal housing (due to damage of the device or otherwise), the possibility exists for a person to be electrically shocked if he or she shorts the “live” conductive surface to ground. The same is true if a person accesses the electronic device internally and contacts a high voltage power wire or other voltage source inside the device.
Electrical protection devices exist for preventing shock hazards of the type noted above in household electronic devices. However, for determining when a fault condition exists, typical electrical protection devices are configured to monitor the power waveform of a device circuit (e.g., current flow) in a generic sense, based on relatively low levels of power waveform fluctuation. That is, fault conditions are determined based on the smallest degree of waveform fluctuation that might in theory present an electrical hazard, regardless of the type or characteristics of the electronic device in question. This “one size fits all” approach may result in the electrical protection device errantly activating, without the occurrence of a hazardous electrical fault, thereby unnecessarily disrupting operation of the household electronic device in question.
An embodiment of the present invention relates to an electrical protection system comprising a household electronic device and an electrical protection unit permanently interfaced with the household electronic device. (By “permanently interfaced,” it is meant that the electrical protection unit cannot be removed from the household electronic device without disabling the household electronic device.) The household electronic device is configured for detachable electric connection to an external household source (e.g., a wall outlet) and to utilize electrical power received from the household source. The electronic device operates according to an electrical power waveform, by which it is meant that the electronic device exhibits the electrical power waveform during operation. The electrical power waveform may include one or more electrical measurements (e.g., voltage and/or current over time) at one or more points of the electronic device.
The electrical protection unit is configured to allow electrical power to pass from the household source to the electronic device (or a portion thereof) if the power waveform is within a waveform profile, and to prevent electrical power from passing from the household source to the electronic device if the power waveform is outside a fault deviation of the waveform profile. The waveform profile is indicative of normal electrical operation of the electronic device, e.g., it is an electric “signature” of the electronic device during operation under designated normal conditions, across its various modes of operation. The fault deviation indicates the amount or extent to which the measured electrical power waveform of the electronic device can vary or deviate from the waveform profile before the electronic device is considered to be in a fault condition and not operating normally.
Thus, in operation, in one embodiment, the electrical protection unit allows electrical power to pass to the electronic device across the entirety of the electronic device's normal electrical operational range, as defined by the waveform profile. However, if the electronic device begins to operate outside its normal electrical operational range, which might be indicative of a short circuit or other electrical fault condition, the electrical protection unit prevents electrical power from passing to the electronic device. The fault deviation accommodates excursions outside the normal electrical operational range of the device that are not considered significant enough to be indicative of a fault condition.
In one embodiment, the electrical protection unit includes an AFCI (arc fault circuit interrupter) unit, a GFCI (ground fault circuit interrupter) unit, or a combination GFCI/AFCI unit.
Another embodiment of the present invention relates to a method for electrically protecting a household electronic device. An electrical waveform profile of the household electronic device is generated when the household electronic device is operating under designated normal conditions. An electrical protection unit is selected based on the waveform profile. The electrical protection unit is selected to allow electrical power to pass to the household electronic device from an external household source if an operational electric power waveform of the household electronic device falls within the waveform profile. Additionally, the electrical protection unit is selected to substantially prevent electrical power from passing to the household electronic device from the external household source if the operational electric power waveform of the household electronic device falls outside a fault deviation of the waveform profile. Once the electrical protection unit is selected, it is permanently integrated with the household electronic device, prior to distribution of the household electronic device to a household end user. This prevents the electrical protection unit from being removed from the household electronic device without disabling the electronic device.
This brief description of the invention is provided to introduce a selection of concepts in a simplified form that are further described herein. This brief description of the invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. Also, the inventors herein have recognized any identified issues and corresponding solutions.
The present invention will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below:
Turning first to
The electrical protection unit 14 is configured to allow electrical power 20 to pass from the household source 16 to the electronic device 12 (or a portion thereof) if the power waveform 22 is within a waveform profile 26, and to prevent electrical power 20 from passing from the household source 16 to the electronic device 12 if the power waveform 22 is outside a fault deviation 24 of the waveform profile 26. The waveform profile 26 is indicative of normal electrical operation of the electronic device 12, e.g., it is an electric “signature” of the electronic device during operation under designated normal conditions. The fault deviation 24 is an amount or extent to which the electrical power waveform 22 of the electronic device 12 can vary or deviate from the waveform profile 26 before the electronic device is considered not to be operating normally and thereby to be in a fault mode.
Thus, in operation, in one embodiment, the electrical protection unit 14 allows electrical power 20 to pass to the electronic device 12 across the entirety of the electronic device's normal electrical operational range, as defined by the waveform profile 26. However, if the electronic device 12 begins to operate outside its normal electrical operational range, which might be indicative of a short circuit condition, an undesired electrical arcing condition, or other electrical fault, the electrical protection unit 14 prevents electrical power from passing to the electronic device. The fault deviation 24 accommodates excursions outside the normal electrical operational range that are not considered significant enough to be indicative of a fault condition.
Operational considerations of fault deviation 24 can be on an express basis or an implied basis. In the former, the power waveform 22 is measured on an ongoing basis, and a calculation or other determination is made of whether the power waveform 22 is within the fault deviation 24 of the waveform profile 22. In the latter, the electrical protection unit 14 is configured so that its electrical fault criteria or conditions for preventing power from passing to the electronic device are outside the normal operational range of the electronic device. In other words, the electrical protection unit is configured so that its criteria for cutting off power to the device are never met when the electronic device is operating normally in any of its various modes of operation.
The electronic device 12 is a standard household electronic device (e.g., a device powered by electricity), such as a stand-alone household appliance. In a typical configuration, the electronic device 12 includes a housing 28, a work unit 30 at least partially housed inside the housing 28, and a power unit 32, part of which is also housed inside the housing 28, electrically connected to the work unit 30. As an example, the housing 28 may be formed of one or more polymer and/or metal sheets and other components connected together to define an interior space and an exterior surface of the electronic device 12.
The electrical power unit 32 is configured for detachable electric connection to the household source 16, which is external to the electronic device 12, for receiving electrical power 20 from the external source. (This does not preclude the electronic device from having one or more internal batteries or other internal electrical power sources, but in at least one mode of operation the electronic device 12 draws power from the external source 16.) The electrical power unit 32 is configured to receive and utilize the external electrical power 20 received from the household source, which includes simply channeling the electrical power 20 to the work unit 30, converting the electrical power 20 into a waveform 34 adapted for use by the work unit 30 (including power regulation and/or voltage transformation), or the like. (For the sake of explanation, electrical power supplied by the electrical power unit 32 is referred to herein as internal electrical power 36, regardless of whether the electrical power unit 32 converts or otherwise modifies the received external electrical power 20.) In one embodiment, for example, the electrical power unit 32 includes a power supply 38, an electrical cable 40 electrically connected to the power supply 38, and an electrical plug 42 electrically terminating the cable 40. The plug 42 is a standard electrical plug (e.g., a NEMA 5 3-prong male plug) that is dimensioned to be removably received in the household source 16 (e.g., a female wall outlet 18 electrically connected to a household electric circuit) for establishing a detachable electrical connection between the household source 16 and electrical cable 40 (and thereby an electrical connection between the household source 16 and the power supply 38). As noted above, the power supply 38 may include circuitry for regulating and/or converting the external electrical power 20 received over the plug 42 and cable 40 from the external source 16. For example, in some electronic devices the power supply 38 converts the received external electrical power 20 to one or more DC voltages 34 for supply to various circuit components of the electronic device.
In a typical case, the electrical power 20 that is output by the household source 16 will be a standard power waveform for the geo-political area in which the household source 16 is located. For example, the standard power waveform in the United States is either 110-120 volts AC at 60 Hz (for standard or light-duty circuits) or 240 volts AC at 60 Hz for heavy-duty applications, e.g., clothes dryers and electric cooking ranges. In many other countries, the standard power waveform available at a household source 16 is 220-240 volts AC at 50 Hz. Thus, electronic devices 12 will typically be configured to utilize electrical power at about 110-240 volts AC at 50-60 Hz as received from the household source 16. (“About” means that the electronic device will work within this range, or a subset of this range, and that the electronic device will also work if the external electrical power fluctuates, due to supply variations from the power grid, up to ±5%.)
The work unit 30 is electrically connected to the power unit 32. The work unit 30 is electrically configured to use the internal electrical power 36 received from the power unit 32 (i.e., the work unit 30 runs on the internal electrical power 36) for carrying out one or more designated work functions of the electronic device. “Work function” refers to an electrically powered function or operation that the electronic device carries out at a macro, end-user application level (i.e., a function that the electronic device is used for by an end user). Examples include heating a stove element, turning a drum and heating air inside an electric clothes dryer, and the like.
The electrical protection unit 14 is permanently interfaced with the electronic device 12, by which it is meant that the electrical protection unit 14 cannot be removed from the electronic device without disabling the household electronic device. More specifically, the electrical protection unit 14 cannot be removed from the electronic device by an end user (e.g., a consumer) without putting the electronic device into a state that would require electrical repair for the electronic device to be functional. This prevents an end user from casually bypassing or disabling the functionality of the electrical protection unit 14, as might result in an unsafe condition.
The electrical protection unit 14 automatically controls the passage of electrical power from the external source 16 to the electronic device 12 in an “on/off” manner, for cutting off power to the electronic device if it enters a fault condition (e.g., an electrical short that might harm an end user), but while also accommodating the entire normal operational range of the electronic device 12. Thus, the electrical protection unit 14 automatically determines (e.g., as a function/result of its circuit/electric topology) whether the electronic device is operating normally, as expected. If so, the electrical protection unit 14 does nothing, and allows electrical power to pass to the electronic device 12. On the other hand, if the electrical protection unit 14 determines that the electronic device is not operating normally, the electrical protection unit 14 automatically prevents electrical power from passing from the external source 16 to the electronic device 12. For example, if normal operation of the electronic device includes current spikes at regular intervals and an associated transient mismatch of current levels in the power input/output lines of the cable 40 (or internal electrical lines of the electronic device connected thereto), due to device startup or cycling, battery charging, or the like, the electrical protection unit 14 does nothing. However, if in addition to the regular current spikes there is an unexpected current mismatch or imbalance in the power input/output lines, of the type that might indicate that electrical current is being shunted to ground in a non-intended manner, the electrical protection unit 14 automatically cuts off power to the electronic device. This is done quickly enough (e.g., <50 msec) to prevent substantial human injury due to electrical shock.
As should be appreciated, when the electrical protection unit is characterized herein as cutting off power to the electronic device, or preventing electrical power from passing from the external source to the electronic device, this includes both (i) electrical power is completely cut off (i.e., current draw=0 amperes) or (ii) electrical power/current is substantially prevented from passing to the electronic device, as further explained below with reference to
In one embodiment, selection and operation of the electrical protection unit 14 is based on several factors. These include the electronic device waveform profile 26, the electronic power waveform 22, and the fault deviation 24. The power waveform 22 is an electrical measure of the electronic device in ongoing operation, e.g., in “everyday” use in the home of an end user. The power waveform 22 may include voltage measurements over time at one or more circuit points in the electronic device, current measurements over time at one or more circuit points in the electronic device, a composite of the two (e.g., electrical power measurements), or the like. Thus, the power waveform 22 is in effect a composite of one or more electrical measurements of the electronic device 12 in ongoing operation. An example power waveform 22 is shown in
Typically, power waveform measurements are taken on an ongoing basis, e.g., current or voltage is measured as a function of time. Measurements over time may be taken continuously, in an analog manner, or may be taken periodically, based on digital sampling or a similar technique. (Samples would typically have to be taken fairly regularly, e.g., 1000 Hz, for quick response to a fault condition.)
The electronic device waveform profile 26 is indicative of normal electrical operation of the electronic device 12, e.g., as noted above, the waveform profile 26 can be thought of as an electric “signature” of the electronic device during operation under designated normal conditions. The designated normal conditions typically include (i) the electronic device operating as designed and intended, without any electrical faults such as faulty components, circuit shorts, or circuit opens, and (ii) the electronic device receiving a designated input power waveform. Other factors, or different factors, may be considered depending on the nature of the device, e.g., environmental conditions.
In one embodiment, to obtain the waveform profile 26, the electronic device 12 is tested prior to distribution to a consumer or other household end user. First, the electronic device 12 is inspected to make sure it is order, including that the component parts of the electronic device are operational and functioning and that there are no errant short or open circuit conditions in the electronic device. Then, the electronic device 12 is connected to an external power source that is regulated to ensure that it is outputting a power waveform that the electronic device is designed to receive and use as input power. (For example, if the electronic device is designed to accept a 120V AC 60 Hz input power signal, then the external power source is regulated to ensure it is outputting a 120V AC 60 Hz power signal.) Subsequently, the electronic device 12 is operated in its various modes of operation, to ensure that the electronic device is operating as designed and intended. Once the electronic device 12 is verified as functioning as intended, one or more designated electrical measurements are taken of the electronic device 12 in operation over time, across one or more modes of operation. (Typically, the electrical measurements are taken across all the various modes of operation of the electronic device.) These measurements constitute the waveform profile 26 of the electronic device 12. The points of measurement of the waveform profile 26 (and what is measured at these points) correspond to the points of measurement of the power waveform 22 that will be monitored in ongoing operation of the electronic device. That is, since the electrical protection unit 14 is configured to monitor the device's power waveform 22 while accommodating the various operational modes of the electronic device 12, the operational modes are electrically characterized in the waveform profile 26 in correspondence with what the electrical protection unit 14 measures in ongoing operation.
As an example, with reference to
As should be appreciated, many electronic devices are electrically specified (namely, their electrical characteristics are recorded in a set of specifications) during development and rollout. Accordingly, it may be possible to derive all or part of the waveform profile 26 from the specifications of the electronic device in question, for example, voltage and maximum current of the appliance or other electronic device.
In operation, the electrical protection unit 14 monitors the power waveform 22 of the electronic device. More specifically, the electrical protection unit 14 measures one or more designated electrical characteristics of the electronic device during ongoing operation of the device, at one or more designated points of the electronic device, where the measurements in combination form the power waveform 22. If the power waveform 22 is within the waveform profile 26 of the device (e.g., if the power waveform matches the waveform profile), then the electrical protection unit 14 continues to monitor the power waveform 22 but does nothing further. If the power waveform 22 is outside the waveform profile 26 (e.g., if the power waveform deviates from the waveform profile), this is indicative of a possible fault condition. However, since the power waveform 22 may vary from the waveform profile 26 even in normal operation, e.g., slight variations, the fault deviation 24 is taken into consideration to ensure that that the electrical protection unit 14 does not unnecessarily cut off power to the electronic device. The fault deviation 24 is an extent that the power waveform 22 must vary from the waveform profile 26 (typically as a function of both measured electrical values and time) before the electrical protection unit 14 prevents power from passing from the household source 16 to the electronic device.
Hypothetical example power waveforms, waveform profiles, and fault deviations are shown in
As another example, as indicated at 24b, the fault deviation may vary with respect to the waveform profile 26. Correspondingly, the electrical conditions 48b by which a fault is deemed to have occurred in this example do not vary over time. Thus, at any point in time, if the power waveform 22 exceeds the current difference level of 48b (e.g., in effect, if the power waveform is above/outside the fault deviation 24b of the waveform profile 26), a fault condition is deemed to have occurred and the electrical protection unit 14 cuts off power to the electronic device.
As another example, as indicated at 24c, the fault deviation may incorporate considerations of time duration, that is, not only does the power waveform 22 have to deviate from the waveform profile by a designated amount/value for a fault condition, but by at least that amount/value for at least a designated duration. In the example shown in
As noted above, it is not necessary for the electrical protection unit 14 to actually compare the power waveform 22, waveform profile 26, and/or fault deviation 24 per se (although doing so is one possibility). Instead, the electrical protection unit may be configured to prevent electrical power from passing to the electronic device if the power waveform 22 meets one or more designated fault conditions (e.g., exceeding a differential current level for a designated time period), where the designated fault conditions are selected so as to not be met by the electronic device when normally operating in any of its modes of operation. For example, with reference again to the fault conditions 48c in
In one embodiment, with reference to
In another embodiment, as shown in
In another embodiment, with reference to
In another embodiment, with reference to
The electrical protection unit 14 can be configured to control electrical power to the electronic device generally (e.g., to the totality of the electrical circuitry in the electronic device), or to one or more sub-portions or subsystems of the electronic device, e.g., to a high power AC subsystem but not a low power DC subsystem. Additionally, where it is described herein that the electrical protection unit 14 prevents power from passing from the external source to the electronic device, this includes any configuration where the electrical protection unit 14 creates a substantially open circuit condition in the electronic control device.
Except where otherwise noted, the electrical devices, circuits, etc. described herein can be implemented using standard electrical components and design methods by one of ordinary skill in the art having the benefit of the present disclosure.
When it is characterized herein that electrical current, power, etc. is substantially prevented from passing to the electronic device or otherwise, this includes both (i) complete prevention (no current, power, etc. passing) or (ii) partial prevention where the amount of current, power, etc. allowed to pass is limited to levels that are classified as safe by the applicable standards body for the region in which the electronic device is to be used.
It should be understood that the embodiments herein are illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof, are therefore intended to be embraced by the claims.
