Embedded in-cord active inrush current limiter device for power supply unit

Abstract

To provide a device and a method for limiting inrush current to an end device to which alternating current (AC) is supplied via a power cord including first and second current carrying conductors.SOLUTION: In a method, a voltage sensor attached to a power cord and accommodated in a housing connected to conductors senses input voltage. A current sensor within the housing senses inrush current via a first conductor. A microcontroller unit (MCU) within the housing receives the sensed input voltage and inrush current. Based on the sensed input voltage, the MCU determines a voltage drop of both ends of a negative temperature coefficient (NTC) thermistor serially connected via a switching device to the first conductor. When the sensed inrush current and / or the sensed input voltage reaches a threshold level, the MCU engages the NTC thermistor to limit inrush current by opening the switching device.SELECTED DRAWING: Figure 3A

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 63 / 635,265, filed April 17, 2024, entitled "In-Cord Active Inrush Current Limiting Device for Power Supply Units," which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates to a power distribution apparatus that supplies alternating current (AC) power to power supply units and converts it into direct current (DC) operating power for end devices. [Background technology]

[0003] Bulk power supply unit (PSU) loads can generate inrush currents exceeding 200 A during certain normal or abnormal operating modes or under poor power quality conditions, such as brownouts and brownouts. For example, rack power distribution units (PDUs, rPDUs) incorporate 16 A TV-8 bistable power relays with an inrush current rating of 117 A. However, these relays can withstand inrush currents of up to 300 A and remain suitable for return to service. Above 300 A, the relays can fail due to terminal melting. The moving contacts can melt, causing the case to burst and spew molten metal around the chassis. This can cause a secondary arc flash and damage nearby components. Relay failures have also occurred in the field during steady-state operation, particularly when facilities are powered by unregulated utility power. Additionally, during supplemental electromagnetic compatibility (EMC) certification test conditions (such as IEC 61000-4-11 immunity tests for voltage dips, short interruptions, and voltage variations), inrush current surges have been observed to affect the regulation and stability of AC-powered meters, causing them to operate in a low-voltage current-limiting mode, potentially resulting in normal but unpredictable rPDU operation. Additionally, the size and cost constraints associated with rPDU devices make it impractical to add active overcurrent protection devices to every rPDU outlet. Summary of the Invention

[0004] In a first aspect, an in-cord inrush current limiting device is disclosed. In one embodiment, the device includes a flame-retardant plastic housing embedded in a power cord extending between a first connector and a second connector at each end. The first connector is pluggable into a power distribution unit (PDU), and the second connector is pluggable into an end device to which the PDU supplies alternating current (AC) operating power via a current-carrying conductor. A switch and a negative temperature coefficient (NTC) thermistor are connected in series with the first conductor, the switch having a closed state and an open state. A voltage sensor is also provided within the housing, coupled to the first conductor and the second conductor, for detecting an input voltage relative to the NTC thermistor. A current sensor is also coupled to the first conductor for detecting an inrush current. The detected input voltage and inrush current are provided to a microcontroller unit (MCU), which derives a voltage waveform based on the detected input voltage and a current waveform based on the detected inrush current. When either the inrush current or the input voltage, or both, reach or exceed a threshold, the MCU activates the NTC thermistor and opens a switch to limit the inrush current. After activation, the MCU closes the switch to shunt the NTC thermistor, allowing it to cool. A reset button allows the current limiting device to be activated or reset.

[0005] In some embodiments, the MCU measures the peak inrush current based on the current waveform.

[0006] In some embodiments, the MCU detects the operating status of the NTC thermistor based on the voltage or current waveform.

[0007] In some embodiments, the operating conditions include the resistance level or power consumption of the NTC thermistor.

[0008] In some embodiments, the voltage sensors include the line side voltage and the load side voltage on either side of the NTC thermistor.

[0009] In some embodiments, the MCU determines a voltage drop based on the sensed line-side voltage and / or load-side voltage (or line-side voltage information received from, for example, an offline AC / DC converter) and activates the NTC thermistor based on at least the voltage drop.

[0010] In some embodiments, the current sensor includes a toroidal current transformer.

[0011] In some embodiments, the current sensor includes a proximity current sensor.

[0012] In some embodiments, the switch includes a bistable power relay.

[0013] In some embodiments, the switch comprises a silicon controlled rectifier (SCR), an insulated bipolar gate transistor (IGBT), or other similar solid-state switching device.

[0014] In some embodiments, the limiter device includes a visual indicator for reporting the device status and / or condition of the PDU.

[0015] In some embodiments, the visual indicator comprises a light emitting diode (LED).

[0016] In some embodiments, the status of the PDU includes an undervoltage severity, an overvoltage severity, or an overcurrent severity.

[0017] In some embodiments, the reset button can reset the visual indicator.

[0018] In a further aspect, a method for limiting inrush current to an end device is disclosed. In an embodiment, the method includes supplying alternating current (AC) operating power to the end device via a power cord including first and second current-carrying conductors. The method includes sensing an input voltage via a voltage sensor housed within a housing in the cord. The method includes sensing an inrush current via a current sensor housed within the housing. The method includes receiving the sensed input voltage and inrush current via a microcontroller unit (MCU) housed within the housing. The method includes limiting the inrush current by activating an NTC thermistor within the housing and opening a switch also housed within the housing when either the input voltage or the inrush current, or both, reach a threshold level. The NTC thermistor and the switch are connected in series with the first conductor.

[0019] In some embodiments, receiving the sensed input voltage includes capturing a voltage waveform, and receiving the sensed inrush current includes capturing a current waveform.

[0020] In some embodiments, the method includes measuring the peak inrush current.

[0021] In some embodiments, the method further includes detecting an operating condition (eg, resistance, power consumption) of the NTC thermistor based on the voltage waveform and / or the current waveform.

[0022] In some embodiments, the method includes shunting the NTC thermistor for a cool-down interval by closing a switch after activating the NTC thermistor.

[0023] In some embodiments, the method includes sensing line-side and load-side input voltages via line-side and / or load-side voltage sensors on either side of the NTC thermistor (or alternatively, receiving line-side input voltage information from an offline AC / DC converter). The method further includes determining a voltage drop across the NTC thermistor based on the line-side and load-side input voltages. The method further includes activating the NTC thermistor based at least on the determined voltage drop.

[0024] This summary is provided merely as an introduction to the subject matter which is more fully described in the detailed description and drawings. This summary should not be considered to describe essential features, nor should it be used to determine the scope of the claims. Moreover, it is to be understood that the foregoing summary and the following detailed description are exemplary and explanatory only and do not necessarily limit the subject matter claimed. [Brief explanation of the drawings]

[0025] The detailed description is set forth with reference to the accompanying drawings. Where the same reference numbers are used in different examples in the description and drawings, they may indicate similar or identical items. Various embodiments or examples ("Examples") of the present disclosure are disclosed in the following detailed description and accompanying drawings. The drawings are not necessarily to scale. In general, the actions of the disclosed processes can be performed in any order unless otherwise specified in the claims. In the drawings: [Figure 1] 1 is an environmental diagram of a power system in which alternating current (AC) power is converted to direct current (DC) operating power at end devices by respective power supply units (PSUs), incorporating in-cord embedded inrush current limiting devices according to exemplary embodiments of the inventive concepts disclosed herein. [Figure 2] 2 is a schematic diagram of the in-cord inrush current limiting device of FIG. 1. [Figure 3A] FIG. 1 is a process flow diagram of a method for limiting inrush current to an end device in accordance with the inventive concepts disclosed herein. [Figure 3B] FIG. 1 is a process flow diagram of a method for limiting inrush current to an end device in accordance with the inventive concepts disclosed herein. [Figure 3C] FIG. 1 is a process flow diagram of a method for limiting inrush current to an end device in accordance with the inventive concepts disclosed herein. [Figure 3D] FIG. 1 is a process flow diagram of a method for limiting inrush current to an end device in accordance with the inventive concepts disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0026] Before describing one or more embodiments of the present disclosure in detail, it should be understood that the scope of the embodiments is not limited to the details of the construction and arrangement of components, steps, or methodologies set forth in the following description or illustrated in the drawings. In the following detailed description of the embodiments, numerous specific details may be set forth to provide a more thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art having the benefit of this disclosure that the embodiments disclosed herein may be practiced without some of these specific details. Additionally, well-known features may not be described in detail to avoid unnecessarily complicating the present disclosure.

[0027] As used herein, a letter following a reference number is intended to refer to an embodiment of a feature or element that is similar, but not necessarily identical, to the preceding element or feature having the same reference number (e.g., 1, 1a, 1b). Such abbreviations are used for convenience only and should not be construed as limiting the disclosure in any way unless expressly stated to the contrary.

[0028] Furthermore, unless expressly stated to the contrary, "or" means an inclusive or, not an exclusive or. For example, condition A or B can satisfy any one of the following: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist).

[0029] Additionally, the terms "a" or "an" may be used to describe elements and components of the embodiments disclosed herein. This is done merely for convenience, and "a" and "an" are intended to include "one" or "at least one," and the singular also includes the plural unless specifically intended otherwise.

[0030] Finally, as used herein, references to "one embodiment" or "some embodiments" mean that a particular element, feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment disclosed herein. The appearances of the phrase "in some embodiments" in various places throughout this specification do not necessarily all refer to the same embodiments, and embodiments may include one or more of the features explicitly described or inherently present herein, or any combination or subcombination of two or more of such features, as well as other features that may not necessarily be explicitly described or inherently present herein.

[0031] Generally, embodiments of the inventive concepts disclosed herein relate to a compact, in-cord, active inrush current limiting device that is embedded in an rPDU power cord and operates independently of the rPDU itself. In situations where power quality is suboptimal due to inrush current surges, the device senses undervoltage or overcurrent conditions and, when these conditions are detected, actively mitigates excessive inrush current, thereby preventing damage to the rPDU or adjacent components (or end devices connected to and powered through the rPDU) and avoiding adverse effects on AC-powered instrumentation.

[0032] 1, there is shown a power distribution system 100. The power distribution system 100 may include a power distribution unit 102 (PDU, also called a rack PDU (rPDU)) with a set of outlets 104, a power cord 106 extending between connectors 108a and 108b, and one or more end devices 110.

[0033] In an embodiment, the power cord 106 can connect an end device 110 (e.g., a power supply unit (PSU), network switch, or other suitable powered device) to the PDU 102 via connectors 108a, 108b. For example, the power cord 106 may be a C20-to-C19 power cord with a “female” (e.g., C19) connector 108a at either end that can plug into the PDU 102 (112) and a “male” (e.g., C20) plug that can plug into the end device 110 (114). Additionally, the power cord 106 may include and encapsulate current-carrying conductors, such as a line conductor for carrying AC power from the PDU 102 to the end device 110, a neutral conductor for returning current to the PDU, and a ground conductor (e.g., protective earth (PE)) that can carry current only under fault conditions. Alternatively, the power cord 106 may include a line / line pair of current-carrying conductors rather than a line / neutral pair.

[0034] In an embodiment, end devices 110 may convert AC power from PDU 102 (e.g., from AC power source 116) into DC operating power of a desired current and / or voltage (e.g., high current, low voltage, secondary voltage) that can be accessed by servers, information technology (IT) devices, or other end devices 110 connected to PDU outlets 104 via power cords 106. For example, outlets 104 may include the C19 outlets described above (or, for example, C13 outlets, or a combination of C13 and C19 outlets, a combination of 20 A outlets (e.g., C19) and 30 A outlets (e.g., Anderson Saf-D-Grid, BizLink), or any other suitable outlet combination).

[0035] In an embodiment, the cord-embedded active inrush current (IC) limiter device 118 may be incorporated into a housing 120, such as a compact UL94 (Underwriters Laboratories 94) compliant colored opaque or translucent flame-retardant plastic enclosure embedded in the power cord 106. For example, the housing 120 may further include a reset switch or button 122 and / or one or more visual indicators 124, as described below.

[0036] 2, an active inrush current (IC) limiter device 118 is shown embedded in a cord. In an embodiment, the IC limiter device 118 may be contained in or located within a housing (120 in FIG. 1) embedded in the power cord (106 in FIG. 1) connecting the PDU 102 and the end device 110, or may be in close proximity to the offline AC / DC converter 200. For example, components of the IC limiter device 118 may include a microcontroller unit 202 (MCU), a current sensor 204, a voltage sensor 206, a switching device 208, a negative temperature coefficient (NTC) thermistor 210, and a local reset switch 212.

[0037] In an embodiment, because the housing 120 is embedded within the power cord (106 in FIG. 1), the various components of the IC limiter device 118 may be connected to one or more current-carrying conductors 214, 216 within the power cord (e.g., line conductor 214 and neutral conductor 216 (which in some embodiments may also be the current-carrying line conductor), and protective earth (PE) ground conductor 218). For example, the MCU 202 may incorporate one or more peripherals and manage data collection, measurement, power control, and human-machine interface (HMI) functions of the IC limiter device 118. Additionally, the MCU 202 may manage the control, status, and DC output voltage (VDC) reported by the offline AC / DC converter 200. For example, the MCU 202 may source operating power from the offline AC / DC converter 200 and vary the switching frequency of the offline AC / DC converter based, for example, on the magnitude of the AC input voltage. Additionally, the MCU 202 can be reset by control / status signals sent from the offline AC / DC converter 200 .

[0038] In an embodiment, the current sensor 204 may be a proximity current sensor, a toroidal current transformer, or a current sensor for detecting the inrush current I flowing through the line conductor 214. S For example, the current sensor 204 can report the detected inrush current to the MCU 202.

[0039] In an embodiment, the voltage sensor 206 is a load-side voltage divider circuit (e.g., including resistors R1 and R2) or a load-side input voltage V S1 The MCU 202 may include other similar voltage detection circuits configured to detect the load-side input voltage V (e.g., power supply voltage) and report the detected load-side input voltage to the MCU 202. Furthermore, the MCU 202 may detect and report the operating status of the NTC thermistor 210 based on the detected current and input voltage. For example, the MCU 202 may detect and report the operating status of the NTC thermistor 210 based on the detected load-side input voltage V (e.g., power supply voltage) detected by the voltage sensor 206. S1 and the line-side input voltage V via control / status updates from the offline AC / DC converter 200.S2 In an embodiment, based on the received load-side input voltage and line-side input voltage, the MCU 202 calculates the voltage drop V across the NTC thermistor 210. D = Δ(V S1 , V S2 ) can be determined. Furthermore, the voltage drop V across the NTC thermistor 210 can be calculated by D and the detected inrush current I S Given and, the MCU calculates the power dissipation of the NTC thermistor (for example, PW = V D × I S ) and / or resistance (e.g., R = V D / I S ) can be determined. In embodiments, based on the power dissipation and resistance of the NTC thermistor 210, the MCU 202 can determine whether the shunted NTC thermistor has cooled sufficiently to regain its nominal initial resistance (and therefore can be effectively reconnected by the MCU for inrush current limiting). In some embodiments, the IC limiter device 118 may be configured to limit the line-side input voltage V S2 A line-side voltage sensor 206a (eg, including resistors R3, R4) may be included to sense (and report to the MCU 202) the line-side voltage.

[0040] In an embodiment, the MCU 202 detects the sensed inrush current I reported by the current sensor 204 and the voltage sensor 206. C and the input voltage V S1 , V S2 For example, for either the sensed inrush current or the sensed input voltage, the waveform may include a time series of ordered samples collected at regular intervals. For example, voltage-based waveform data (e.g., sensed input voltage V S1 , V S2and / or based on voltage drop samples) can be further analyzed (by MCU 202 or offline) to detect, for example, voltage transients, voltage sags, voltage rises, voltage interruptions, harmonics, and / or other power quality conditions useful to MCU 202 in managing the relay / contact status of NTC thermistor 210. Similarly, waveform data based on the sensed inrush current can provide peak current (e.g., up to 300 A), root mean square (RMS), crest factor, and additional auxiliary data useful to MCU 202 in managing the NTC thermistor 210.

[0041] In an embodiment, switching device 208 includes a bistable power relay (e.g., a 16 A, TV-8 rated, single-pole, single-throw (SPST) contact-open relay, latching relay) and NTC thermistor 210 (e.g., a 5 Ω NTC thermistor) can be connected in series with line conductor 214. Alternatively, switching device 208 can include a silicon-controlled rectifier (SCR), insulated-gate bipolar transistor (IGBT), or other suitable solid-state switching device (if faster switching times are required, e.g., microseconds instead of milliseconds (as in the case of a bistable power relay)).

[0042] In an embodiment, switching device 208 can have an open state and a closed state. For example, under normal power quality conditions, MCU 202 can maintain switching device 208 in a closed state, causing steady current to pass through the switching device rather than through NTC thermistor 210 (e.g., because the resistance of an NTC thermistor is relatively high).

[0043] In an embodiment, under certain circumstances (e.g., when a condition that may cause a sudden increase in inrush current is detected or when such a condition may exist), MCU 202 may activate NTC thermistor 210 to limit the inrush current flowing through line conductor 214. For example, when a peak inrush current I sensed by current sensor 204 and / or measured by MCU 202 is Sreaches an overcurrent threshold, or the input voltage V sensed by the voltage sensor 206, 206a S1 , V S2 is the low voltage threshold (e.g., <230V PK ), the MCU 202 may open the switching device 208 to activate the NTC thermistor 210 in the circuit. Furthermore, when the inrush current heats up the NTC thermistor 210, the resistance decreases as the inrush current flows through the NTC thermistor 210. In an embodiment, the MCU 202 can signal the switching device 208 to open and connect the NTC thermistor 210 for inrush current limiting by opening the switching device 208 under other circumstances (e.g., during cold start or startup, when an end device is disconnected, during steady-state operation, when a power loss may be imminent (e.g., when an upstream circuit breaker is open, when the AC power source (116 in FIG. 1) is disconnected)).

[0044] In an embodiment, when the NTC thermistor 210 is connected, the MCU 202 may signal the switching device 208 to close and shunt the thermistor, disconnect the thermistor, and allow the thermistor to cool to a nominal temperature and resistance in a non-functional state, e.g., in preparation for the next connection. For example, after a predetermined number of line cycles, the MCU 202 may close the switching device 208 for at least a predetermined cool-down interval (e.g., 30 seconds).

[0045] In an embodiment, IC limiter device 118 may include one or more visual indicators 124. For example, each visual indicator 124 may be an RGB light-emitting diode (LED) capable of communicating the status of IC limiter device 118 and / or an operational condition associated with the AC supplied by AC power source 116. For example, visual indicator 124 may indicate the severity or magnitude of an undervoltage or overvoltage, the severity or magnitude of an overcurrent or undercurrent, or other sensed or determined power quality condition. In an embodiment, visual indicator 124 may signal the power quality condition on a discrete or binary basis (e.g., on / off), or by, for example, a color gradient, luminosity, or a combination thereof.

[0046] In some embodiments, IC limiter device 118 may include a local reset switch 212 configured to be activated by a button (122, FIG. 1) on the housing (120, FIG. 1). For example, activation of button 122 may allow for a local reset or arming of IC limiter device 118. In some embodiments, an inrush current surge event (e.g., activation of NTC thermistor 210) may activate visual indicator 124 as a warning, after which visual indicator 124 may remain illuminated indefinitely. Activating button 122 allows a user to reset visual indicator 124 to a default or off state.

[0047] Referring to FIG. 3A, a method 300 may be performed by the IC limiter device 118 and may include the following steps.

[0048] In step 302, alternating current (AC) (e.g., from an AC power source) is supplied (e.g., via a power cord connecting a power distribution unit (PDU, rack PDU (rPDU)) to a power supply unit (PSU) or similar end device) and converted to direct current (DC) operating power by the end device (e.g., a powered device connected to an outlet on the rPDU).

[0049] In step 304, a voltage sensor in the power cord-embedded IC limiter device senses the AC-related input voltage (eg, between the current-carrying conductors (eg, line-to-neutral, line-to-line) in the power cord).

[0050] In step 306, a current sensor in the IC limiter device senses an inrush current on the line conductor.

[0051] In step 308, a microcontroller unit (MCU) of the IC limiter device receives the sensed input voltage and inrush current. For example, the MCU samples or captures high-resolution waveforms of the sensed input voltage and inrush current and measures the peak inrush current (and other power quality conditions) based on the captured voltage and current waveforms.

[0052] In step 310, when the sensed input voltage and / or the sensed inrush current reaches a threshold level (e.g., an undervoltage threshold, an overcurrent threshold), the MTC activates an NTC thermistor of the IC current limiter device by opening the contacts of a switching device (e.g., a bistable power relay, a silicon-controlled rectifier (SCR), an insulated-gate bipolar transistor (IGBT), or other suitable solid-state switch) of the IC current limiter device. The NTC thermistor is connected in series with the switching device and configured to reduce the inrush current. In some embodiments, the NTC thermistor may be activated based on other power quality conditions derived by the MCU (e.g., determined or derived based on the voltage or current waveforms).

[0053] 3B, method 300 may include an additional step 312. In step 312, the MCU detects additional operating conditions of the NTC thermistor based on the voltage-based and current-based waveform data. For example, based on the voltage waveform, the MCU determines one or more of voltage transients, dips, swells, interruptions, harmonics, and / or other power quality conditions useful to the MCU in managing the relay / contact status of the NTC thermistor. Similarly, based on the current waveform data, the MCU determines peak current, RMS, crest factor, and / or other current-based information.

[0054] 3C, method 300 may include an additional step 314. In step 314, after activation of the NTC thermistor, the MCU closes the contacts of a switching device to shunt the thermistor for a predetermined cool-down interval (e.g., allowing the thermistor to cool in a non-functional state in preparation for future reactivation). For example, the MCU may shunt the NTC thermistor after a predetermined number of activation cycles to allow the NTC thermistor to return to its nominal temperature and initial resistance.

[0055] 3D, method 300 may include an additional step 316. In step 316, the MCU determines the voltage drop across an NTC thermistor connected in series with the line conductor. For example, the MCU may receive the line-side and load-side voltages from line-side and load-side voltage sensors, respectively, on either side of the thermistor, or may receive the line-side voltage from an offline AC / DC converter.

[0056] conclusion It is believed that embodiments of the inventive concepts disclosed herein have many advantages. For example, as discussed above, end devices can be equipped with a compact inrush current limiter function to protect end devices, power cords, and other components (e.g., AC power supplies, rPDUs) from current surges, equipment damage, and / or abnormal operation without significantly impacting cost, space, or weight factors.

[0057] Those skilled in the art will recognize that technology has advanced to the point where there is little distinction between hardware and software implementations of various aspects of a system. The use of hardware or software is typically (but not necessarily, and the choice between hardware and software may be significant in certain situations) a design choice representing a trade-off between cost and efficiency. Those skilled in the art will appreciate that there are various means (e.g., hardware, software, and / or firmware) for implementing the processes and / or systems and / or other techniques described herein, and that the preferred means will vary depending on the context in which the processes and / or systems and / or other techniques are deployed. For example, if an implementer determines that speed and accuracy are paramount, the implementer may select an implementation that is primarily based on hardware and / or firmware. Conversely, if flexibility is paramount, the implementer may select an implementation that is primarily based on software. Alternatively, a combination of hardware, software, and / or firmware may be selected. Thus, there are multiple implementation means for implementing the processes, devices, and / or other techniques described herein, none of which is inherently superior, and the implementation means used will depend on the situation in which the implementer is deployed and the implementer's particular concerns (e.g., speed, flexibility, predictability, etc.), all of which are subject to change. Those skilled in the art will recognize that the optical aspects of the implementation will typically use optically oriented hardware, software, and / or firmware.

[0058] The foregoing detailed description has set forth various embodiments of devices and / or processes via the use of block diagrams, flowcharts, and / or examples. To the extent that such block diagrams, flowcharts, and / or examples include one or more functions and / or operations, those skilled in the art will appreciate that each function and / or operation within such block diagrams, flowcharts, or examples can be individually and / or collectively implemented by a wide range of hardware, software, firmware, or any combination thereof. In one embodiment, portions of the subject matter described herein may be implemented by an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), or other integrated format. However, those skilled in the art will appreciate that some aspects of the embodiments disclosed herein can equivalently be implemented, in whole or in part, as an integrated circuit, one or more computer programs running on one or more computers (e.g., one or more programs running on one or more computer systems), one or more programs running on one or more processors (e.g., one or more programs running on one or more microprocessors), firmware, or substantially any combination thereof. Those skilled in the art will also appreciate that, in light of this disclosure, designing circuitry and / or writing software and / or firmware code is within the skill of those in the art. Furthermore, those skilled in the art will appreciate that the mechanisms of the subject matter described herein can be distributed as a program product in various forms, and that the exemplary embodiments of the subject matter described herein apply regardless of the particular type of signal-bearing medium used to actually achieve distribution. Examples of signal-bearing media include, but are not limited to, recordable media such as floppy disks, hard disk drives, compact disks (CDs), digital video disks (DVDs), digital tape, computer memory, and transmission-type media such as digital and / or analog communications media (e.g., fiber optic cables, wave guides, wired communications links, wireless communications links, etc.).

[0059] In a general sense, those skilled in the art will recognize that the various aspects described herein can be individually and / or collectively implemented by a wide range of hardware, software, firmware, or any combination thereof, and can be considered to be comprised of various types of "electrical circuitry." Accordingly, "electrical circuitry," as used herein, includes, but is not limited to, an electrical circuit having at least one discrete electrical circuit, an electrical circuit having at least one integrated circuit, an electrical circuit having at least one application-specific integrated circuit, an electrical circuit forming a general-purpose computing device configured by a computer program (e.g., a general-purpose computer configured by a computer program that at least partially executes the processes and / or devices described herein, or a microprocessor configured by a computer program that at least partially executes the processes and / or devices described herein), an electrical circuit forming a memory device (e.g., a form of random access memory), and / or an electrical circuit forming a communications device (e.g., a modem, a communications switch, or an optoelectronic device). Those skilled in the art will understand that the subject matter described herein can be implemented in analog or digital form, or a combination thereof.

[0060] Those skilled in the art will understand that it is common in the art to describe devices and / or processes in the manner described herein and then use engineering techniques to integrate such described devices and / or processes into a data processing system. That is, at least a portion of the devices and / or processes described herein can be integrated into a data processing system through a reasonable amount of experimentation. Those skilled in the art will understand that a typical data processing system generally includes one or more of the following: a system unit housing; a video display device; memory, such as volatile and non-volatile memory; a processor, such as a microprocessor and a digital signal processor; computational entities, such as an operating system, drivers, a graphical user interface, and application programs; one or more interaction devices, such as a touchpad or screen; and / or a control system, including feedback loops and control motors (e.g., feedback for sensing position and / or velocity, and control motors for moving and / or adjusting parts and / or quantities). A typical data processing system can be implemented using suitable commercially available components, such as those typically found in data computing / communication systems and network computing / communication systems.

[0061] The subject matter described herein may illustrate different components contained within or connected to other different components. It should be understood that such illustrated architectures are merely exemplary, and that many other architectures that achieve the same functionality may actually be implemented. Conceptually, any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Thus, any two components combined herein to achieve a particular functionality can be considered to be "associated" with each other such that the desired functionality is achieved, regardless of the architecture or intermediate components. Similarly, any two components so associated can also be considered to be "operably connected" or "operably coupled" to each other to achieve the desired functionality. Additionally, any two components that can be associated in this manner can also be considered to be "operably coupleable" to each other to achieve the desired functionality. Examples of operably coupleable include, but are not limited to, components that are physically matable and / or physically interacting, components that are wirelessly interacting and / or wirelessly interacting, and / or components that logically interact and / or logically interacting.

[0062] While particular aspects of the inventive subject matter described herein have been shown and described, it will be apparent to those skilled in the art that, based on the teachings herein, changes and modifications can be made without departing from the subject matter described herein and its broader aspects, and therefore, the appended claims are intended to encompass within their scope all such changes and modifications that are within the true spirit and scope of the subject matter described herein. It can further be understood that the present invention is defined by the appended claims.

Claims

1. 1. An inrush current limiting device having a housing made of flame retardant plastic embedded within a power cord between a first connector and a second connector, the first connector is connectable to a power distribution unit (PDU) capable of supplying alternating current (AC) to an end device; the second connector is connectable to the end device; the power cord comprises at least one first current-carrying conductor and at least one second current-carrying conductor; the housing is configured to at least partially enclose at least one switching device, a negative temperature coefficient (NTC) thermistor, at least one voltage sensor, a current sensor, and a microcontroller unit (MCU); the switching device and the NTC thermistor are connected in series with the first current-carrying conductor, the switching device having an open state and a closed state; the at least one voltage sensor is operably coupled to the first and second current-carrying conductors, each voltage sensor configured to sense an input voltage to the NTC thermistor; the current sensor is operably coupled to the at least one first current-carrying conductor and configured to sense an inrush current; the microcontroller unit (MCU) is operatively coupled to the at least one voltage sensor, the current sensor, and the switching device; The MCU receiving the at least one sensed input voltage and the sensed inrush current; capturing a voltage waveform based on the at least one sensed input voltage; capturing a current waveform based on the detected inrush current; activating the NTC thermistor by opening the switching device to limit inrush current when one or more of the at least one sensed input voltage or the sensed inrush current reaches a threshold level; shunting the NTC thermistor for at least one cool-down interval after activating the NTC thermistor by closing the switching device; and at least one reset button operably connected to the MCU, the at least one button configured to at least one of arm the current limiting device or reset the current limiting device when operated by a user.

2. In claim 1, The inrush current limiting device, wherein the MCU is configured to measure a peak inrush current based on the current waveform.

3. In claim 1, The inrush current limiting device is characterized in that the MCU is configured to detect an operating state of an NTC thermistor based on one or more of the voltage waveform or the current waveform.

4. In claim 3, The operating state of the NTC thermistor includes at least one of a resistance of the NTC thermistor and a power consumption of the NTC thermistor.

5. In claim 3, 10. The inrush current limiting device, wherein the at least one voltage sensor includes at least one of a line-side voltage sensor configured to detect a line-side voltage or a load-side voltage sensor configured to detect a load-side voltage.

6. In claim 5, the MCU is configured to determine a voltage drop across the NTC thermistor based on at least one of the sensed line-side or load-side voltages, and to activate the NTC thermistor based at least on the determined voltage drop.

7. In claim 1, 10. An inrush current limiting device, wherein the at least one current sensor includes at least one toroidal current transformer.

8. In claim 1, 10. An inrush current limiting device, wherein the at least one current sensor includes at least one proximity current sensor.

9. In claim 1, 10. An inrush current limiting apparatus, wherein the at least one switching device includes a bistable power relay.

10. In claim 1, 10. The inrush current limiting apparatus, wherein the at least one switching device comprises at least one solid-state switch selected from the group consisting of a silicon-controlled rectifier (SCR) and an insulated gate bipolar transistor (IGBT).

11. In claim 1, further comprising at least one visual indicator operably coupled to the MCU; 10. The inrush current limiting device of claim 9, wherein the at least one visual indicator is configured to report at least one of a status of a current limiting device or a condition associated with the PDU.

12. In claim 11, 10. An inrush current limiting device, wherein the at least one visual indicator comprises at least one light emitting diode (LED).

13. In claim 11, the condition includes at least one of an undervoltage severity associated with the at least one detected input voltage, an overvoltage severity associated with the at least one detected input voltage, or an overcurrent severity associated with the detected inrush current.

14. In claim 11, The inrush current limiting device, wherein the reset button is configured to reset the at least one visual indicator.

15. supplying alternating current to an end device via a power cord including a first current-carrying conductor and a second current-carrying conductor; detecting at least one input voltage via at least one voltage sensor operably coupled to the first and second current carrying conductors and housed in a housing attached to the power cord; detecting an inrush current via a current sensor operably coupled to the first current-carrying conductor and contained within the housing; receiving at least one of the sensed input voltage and the sensed inrush current via a microcontroller unit (MCU) contained in the housing; activating an NTC thermistor to limit inrush current by opening a switching device via the MCU when at least one of the sensed input voltage or the sensed inrush current reaches a threshold level; and 10. A method for limiting inrush current to an end device, wherein the NTC thermistor and the switching device are connected in series with the first current-carrying conductor.

16. In claim 15, receiving the sensed input voltage and inrush current via a microcontroller unit (MCU) contained in the housing, capturing, via the MCU, a voltage waveform based on at least one of the sensed input voltages; capturing a current waveform based on the detected inrush current via the MCU; 1. A method for limiting inrush current to an end device, comprising:

17. In claim 16, A method for limiting inrush current to an end device, wherein the step of capturing a current waveform based on the detected inrush current via the MCU includes the step of measuring a peak inrush current based on the current waveform via the MCU.

18. In claim 16, The method for limiting inrush current to an end device further comprises detecting, via the MCU, at least one operating state of the NTC thermistor based on one or more of the voltage waveform or the current waveform.

19. In claim 15, 10. The method for limiting inrush current to an end device, further comprising: following activation of the NTC thermistor, shunting the NTC thermistor for a cool-down interval by closing the switching device via the MCU.

20. In claim 15, the step of detecting at least one input voltage via the at least one voltage sensor includes at least one of detecting a line-side input voltage via a line-side voltage sensor or detecting a load-side input voltage via a load-side voltage sensor; determining, via the MCU, a voltage drop across an NTC thermistor based on at least one of the line-side voltage or the load-side voltage; and activating the NTC thermistor to limit the inrush current when at least one of the detected input voltage or the sensed inrush current reaches a threshold level; 10. A method for limiting inrush current to an end device, wherein activating an NTC thermistor to limit the inrush current comprises activating an NTC thermistor based on at least the determined voltage drop.

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