System and method for identifying short circuit events during high inrush currents - Patents.com

Abstract

A method for protecting a load circuit includes detecting a load current through a switch electrically connected in series with the load circuit, detecting a voltage drop across the switch, determining a rate of change of the voltage drop across the switch, determining whether to disable the switch based on the load current and the rate of change of the voltage drop across the switch, and in response to determining to disable the switch, disabling the switch to interrupt current to the load circuit.

Description

[Technical field]

[0001] One aspect of an embodiment of the present disclosure relates generally to a circuit breaker system. [Background technology]

[0002] In power systems, switchgear with protective devices such as solid-state power controllers (SSPCs) are used to control the system loads and protect the wiring from fault and short circuit currents. These devices use information about the load current to respond to abnormal conditions. The high inrush currents demanded by highly capacitive loads can be mistaken as fault currents by these devices. This problem is exacerbated at high voltage applications where the inrush current of the capacitive loads is much larger and cannot be distinguished from short circuit currents. Related art switchgear with protective devices will detect such large inrush currents as fault currents and erroneously turn off the loads, creating a false trip condition in the system.

[0003] Some existing techniques address this problem by reducing the inrush current. In some systems, a precharge circuit is used in conjunction with a capacitive load to limit the inrush current. This technique does not affect the short detection of upstream protection devices to the wiring between the source and the load, but it slows down the turn-on response time of the load, which is undesirable. Furthermore, the precharge circuit can be large, requiring additional control hardware and bulky components for power consumption. In aviation applications where weight is a critical factor, this is not a preferred option.

[0004] In some other systems, various active current limiting techniques, including soft start, are used within SSPCs to reduce inrush current into capacitive loads. Soft start requires that switching devices such as MOSFETs and IGBTs be operated in their active operating region, increasing the complexity of the circuits designed to protect them from damage due to excessive power dissipation. In addition, soft start circuits undesirably slow the turn-on time of the system, which may be unacceptable in certain applications.

[0005] Traditional short circuit detection is based on the load current exceeding a predefined trip threshold. The short circuit trip value is typically set at 10 times the nominal load rated current. When current limiting techniques are utilized, the short circuit event also limits the short circuit current, which may disrupt traditional short circuit detection methods. If the traditional short circuit detection method is modified to have a trip threshold below the limited load current, a short circuit is detected when the current exceeds this lower trip threshold and takes longer than a predefined time for the inrush current to decrease below the trip point. In this implementation, the protection response time is slowed down to avoid false trips. To prevent nuisance trips, short circuit detection systems may be large in size and weight to manage the additional power consumption during this waiting time to prevent damage to solid-state switches. Furthermore, in high voltage systems such as 270V DC and 540V DC, slow short circuit detection may result in fault currents and arcing faults, which may cause catastrophic failures.

[0006] The above information disclosed in this Background section is intended to enhance the understanding of the present disclosure and, therefore, may contain information that does not constitute prior art already known to those skilled in the art. Summary of the Invention

[0007] One aspect of the embodiments of the present disclosure is directed to a system and method for protecting a load or wiring against fault and short circuit currents while allowing fast charging of the capacitive load. A protection device according to some embodiments can quickly distinguish between a high inrush current of the capacitive load and a short circuit event, so that the protection device can quickly charge and supply power to the capacitive load and can quickly turn off (trip) in the event of a short circuit event to protect the wiring and prevent failure of the device.

[0008] According to some embodiments of the present disclosure, a method of protecting a load circuit is provided, the method including detecting a load current through a switch electrically connected in series with the load circuit, detecting a voltage drop across the switch, determining a rate of change of the voltage drop across the switch, determining whether to disable the switch based on the load current and the rate of change of the voltage drop across the switch, and in response to determining to disable the switch, disabling the switch to interrupt current to the load circuit.

[0009] In some embodiments, determining whether to disable the switch includes determining whether the load current is greater than a first threshold; determining whether a rate of change of the voltage drop is less than a second threshold; and determining to disable the switch in response to determining that the load current is greater than the first threshold and the rate of change of the voltage drop is less than the second threshold.

[0010] In some embodiments, the method further includes, in response to determining not to deactivate the switch, maintaining actuation of the switch.

[0011] In some embodiments, determining whether to disable the switch includes determining whether the load current is greater than a first threshold; determining whether the rate of change of the voltage drop is less than a second threshold; and determining not to disable the switch in response to determining that the load current is less than or equal to the first threshold or the rate of change of the voltage drop is greater than or equal to the second threshold.

[0012] In some embodiments, the first threshold is less than or equal to the rated current of the switch.

[0013] In some embodiments, the switch comprises a field effect transistor (FET).

[0014] According to some embodiments of the present disclosure, a protection device connected to a load circuit is provided, the protection device comprising: a switch electrically connected in series with the load circuit; a current sensor configured to detect a load current flowing through the switch; a voltage sensor configured to measure a voltage drop across the switch; a detection device configured to generate a switch control signal based on a rate of change of the load current and the voltage drop; and a gate driver configured to selectively activate and deactivate the switch based on the switch control signal.

[0015] In some embodiments, the switch includes a field effect transistor (FET) having a gate electrode connected to a gate driver and a source electrode connected to a load circuit.

[0016] In some embodiments, the current sensor includes a sense resistor electrically connected in series with the switch and the load circuit, and the voltage sensor includes an error amplifier having an input terminal connected across the switch and configured to generate a switch voltage corresponding to the voltage drop across the switch.

[0017] In some embodiments, the protection device further comprises a differentiator connected between the voltage sensor and the detection device and configured to generate a differentiated signal corresponding to a rate of change of the voltage drop across the switch based on the switch voltage from the voltage sensor.

[0018] In some embodiments, the detection device is further configured to receive a voltage drop across the switch from the voltage sensor and calculate a rate of change of the voltage drop based on the voltage drop.

[0019] In some embodiments, the detection apparatus is configured to determine whether the load current is greater than or equal to a first threshold; determine whether a rate of change of the voltage drop is less than a second threshold; and in response to determining that the load current is greater than or equal to the first threshold and the rate of change of the voltage drop is less than the second threshold, generate a switch control signal corresponding to stopping the switch.

[0020] In some embodiments, the detection apparatus is configured to determine whether the load current is greater than or equal to a first threshold; determine whether the rate of change of the voltage drop is less than a second threshold; and in response to determining that the load current is less than or equal to the first threshold or the rate of change of the voltage drop is greater than or equal to the second threshold, generate a switch control signal corresponding to maintaining an actuation of the switch.

[0021] In some embodiments, the protection device further comprises a current limiter circuit coupled between the gate driver and the switch and configured to limit the load current to a current limit value.

[0022] In some embodiments, the current limiter circuit comprises a bipolar junction transistor (BJT) having a base, an emitter, and a collector connected to the gate of the switch, and the current sensor is connected between the base and emitter of the BJT.

[0023] In some embodiments, the protection device further comprises a controller configured to receive the load current and the voltage drop across the switch and to send a signal to the gate driver to disable the switch based on the load current and the voltage drop.

[0024] In some embodiments, the switch comprises a field effect transistor (FET). [Brief description of the drawings]

[0025] The accompanying drawings, together with the specification, illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. [Figure 1] FIG. 1 illustrates a protection device connected between an input power source and a load, according to some example embodiments of the present disclosure. [Diagram 2] FIG. 2 is a diagram illustrating the rate of change of switch voltage versus load capacitance in a constant current scenario, in accordance with some exemplary embodiments of the present disclosure. [Diagram 3] FIG. 3 illustrates a block diagram of a protection device according to some exemplary embodiments of the present disclosure. [Figure 4A] FIG. 4A illustrates an implementation of a protection circuit according to some embodiments of the present disclosure. [Figure 4B] FIG. 4B illustrates a block diagram of a protection device in which identification is performed by a detection device, according to some exemplary embodiments of the present disclosure. [Figure 4C] FIG. 4C illustrates an implementation of a detection device according to some embodiments of the present disclosure. [Figure 5A] FIG. 5A is a diagram illustrating turn-on and inrush current control of the protection device 100 according to some embodiments of the present disclosure. [Figure 5B] FIG. 5B is a diagram illustrating turn-on and inrush current control of the protection device 100 according to some embodiments of the present disclosure. [Figure 5C] FIG. 5C illustrates turn-on and inrush current control of the protection device 100 in accordance with some embodiments of the present disclosure. [Figure 6A]FIG. 6A illustrates a protection device trip function when a short circuit condition is detected, according to some embodiments of the present disclosure. [Figure 6B] FIG. 6B illustrates a diagram illustrating the tripping function of a protection device when a short circuit condition is detected, according to some embodiments of the present disclosure. [Figure 6C] FIG. 6C illustrates a diagram illustrating the tripping function of a protection device when a short circuit condition is detected, according to some embodiments of the present disclosure. [Figure 7] FIG. 7 is a flow diagram illustrating a process for protecting a load circuit according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The detailed description set forth below is intended as a description of exemplary embodiments of the systems and methods for defect detection provided in accordance with the present disclosure, and is not intended to represent the only manner in which the present disclosure may be constructed or utilized. This specification defines features of the present disclosure in relation to the illustrated embodiments. However, it should be understood that the same or equivalent functions and structures may be achieved by different embodiments that are intended to be encompassed within the scope of the present disclosure. As shown elsewhere in this specification, like element numbers are intended to indicate like elements or features.

[0027] One aspect of an embodiment of the present disclosure is directed to a protection device used to control a system load and protect wiring from fault or short circuit currents. The present invention provides a method and device for detecting not only the magnitude of current flowing through a power semiconductor (i.e., a solid-state switch) in line with the load, but also the rate of change of voltage from drain to source of the power semiconductor (dV / dt or dV / dt DS), the protective device can quickly distinguish between resistive short circuit currents and capacitive inrush currents. This allows the protective device to avoid nuisance tripping (e.g., interrupting current on the wiring with a switch in the case of high inrush capacitive currents charging a capacitive load) while facilitating simpler wiring protection circuit designs to protect against short circuit and overload conditions.

[0028] FIG. 1 illustrates a protection device connected between an input power source and a load, according to some example embodiments of the present disclosure.

[0029] In some embodiments, the protection device 100 is in a current path between the input power source 10 and a system load (e.g., a load circuit) 20 and monitors and manages the delivery of power between the input power source 10 and the load 20. The protection device 100 may be configured to protect wiring / cables and / or other equipment connected to the electrical load 20 from damage caused by excessive current due to a short circuit (e.g., a short circuit at the load 20). In other words, the protection device 110 interrupts the flow of current in response to a fault being detected. In some examples, the protection device 110 may be a circuit breaker (e.g., a temperature-based or remote-controlled circuit breaker), a fuse (e.g., a one-time fuse or a resettable fuse), etc. The protection device 100 may accurately measure and report voltage and current measurements, provide low-loss switching with controlled rise and fall times that can reduce EMI emissions, provide very fast short circuit response, I2t (current squared time) overload protection, and / or the like. Load 20 may be, for example, a conductive wire / cable, an external circuit, and / or the like.

[0030] When the protection device 100 is turned on under a short circuit condition (i.e., the load 20 is shorted), the resulting current (I LOAD ) is limited by the impedance of the input power supply 10 and the entire system. In such a case, the power supply voltage V INappears across the switch (e.g., a power semiconductor or solid-state switch) 110 of the protection device 100, resulting in high power consumption. This condition continues until the switch 110 is turned off. The longer the protection device 100 remains in the on state, the higher the energy dissipated by the switch 110, which, if not prevented, can eventually lead to destruction.

[0031] When the protection device 100 is applied to a capacitive load 20 that is not yet charged, the effective load impedance initially becomes a short circuit, causing a high inrush current. In this example, too, a high voltage can develop across the switch 110. As the capacitive load 20 charges, its voltage rises and the load current I LOAD decreases, so the voltage drop across switch 110 decreases over time.

[0032] The protection device 100 utilizes a method for distinguishing between inrush current and short circuit current. According to some embodiments, the protection device 100 utilizes short circuit detection based not only on the load current but also on the time rate of change (dV / dt) of the voltage at the terminals of the switch 110. The protection device 100 detects the load current I LOAD In some embodiments, the protection device 100 utilizes a current limiter to monitor the load current I LOAD does not exceed a set value. This serves to maintain a constant current during a high current event (e.g., a short circuit or high inrush current event). The protection device 100 simultaneously monitors the voltage change across the switch 110 and uses the voltage change in combination with the current information to determine whether the high current is the result of a capacitive inrush current event or a resistive short circuit event.

[0033] During a capacitive inrush condition, the behavior of the voltage change across switch 110 is equivalent to the voltage change across capacitive load 20, which can be described by the following equation:

number

[0034] The current (I) determines the rate of change of voltage that occurs across a given capacitive (C) load. Because the constant current is controlled by the protection device 100, the dV / dt in the above equation can be accurately measured to determine the load capacitance value. The constant current value (i.e., the current limit value) in some embodiments is set to be equal to or less than the maximum current that the switch 110 can withstand during a charging cycle without being damaged. For example, the current limit value can be set to approximately 600A, 1200A, or other value suitable for the desired application.

[0035] FIG. 2 is a diagram illustrating the rate of change of switch voltage versus load capacitance in a constant current scenario, in accordance with some exemplary embodiments of the present disclosure.

[0036] The protection device 100 in the example of FIG. 2 is operating in a current limit mode (e.g., with the upper current limit set / limited to 600A). As described in equation (1) and shown in FIG. 2, the smaller the capacitance value of the load 20, the higher the rate of change of the switch voltage (dV / dt). Similarly, the larger the capacitance value, the smaller the dV / dt value. In some embodiments, if the current is large and the dV / dt is below a certain threshold (e.g., 1.5), the capacitance value is determined to be large. In such a case, the load is considered to be capacitive and the large current is considered to be a capacitive inrush current. If the current is large but the dV / dt is above a threshold, the load capacitance is small and the large current is considered to be the result of a resistive short circuit. For a given current limit value, the dV / dt threshold can be selected to be a high slope of the dV / dt vs. capacitance curve to improve detection accuracy.

[0037] FIG. 3 illustrates a block diagram of a protection device 100 according to some example embodiments of the present disclosure.

[0038] In some embodiments, the protection device 100 includes a switch (e.g., a power semiconductor or solid-state switch) 110, a voltage sensor 120, a current sensor 130, a differentiator 140, a detection device 150, a gate driver 160, and a current limiter (e.g., a current limiter circuit) 170. The switch 110 may be a field effect transistor (e.g., an NMOS FET or nFET) having drain and source terminals connected between the input power source 10 and the load 20. The voltage sensor 120 may be an operational amplifier (e.g., an error amplifier) ​​with its input terminals connected across the source and drain terminals of the switch 110, and measures the voltage drop across the switch 110 (e.g., the drain-source voltage V DS A differentiator (e.g., a differentiation circuit) 140 is connected between the voltage sensor 120 and the detection device 150 and is configured to measure the rate of change of the voltage drop across the switch 110 (dV DS The current sensor 130 is electrically connected in series with the switch 110 and configured to generate a differential signal (e.g., a voltage signal) corresponding to the load current I LOAD The current sensor 130 may be a sense resistor across which a voltage corresponding to the current flowing through it is applied.

[0039] According to some embodiments, a detection device (e.g., a short circuit / overload detection device) 150 detects the load current I LOADand the rate of change of the voltage drop, and generate a corresponding switch control signal to control the state (e.g., on / off state) of the switch 110. For example, when the magnitude of the detected current is large, i.e., the detected current is larger than a first threshold, and the rate of change of the voltage at the switch 110 is small, i.e., the rate of change is smaller than a second threshold, the detection device 150 determines that the high current is the result of a resistive short circuit and generates a switch control signal to disable / turn off the switch 110. This can prevent damage to the switch 110 and / or the load 20 that may result from this resistive short circuit condition. Furthermore, when the magnitude of the detected current is large, i.e., the detected current is larger than a first threshold, and the rate of change of the voltage at the switch 110 is also large, i.e., the rate of change is equal to or larger than a second threshold, the detection device 150 determines that the high current is due to an inrush current to the capacitive load and generates a switch control signal to maintain the switch 110 in an activated / on state. As a result, in such a case, the protection device 100 will not erroneously turn off the switch 110 and will pass a large current to charge the capacitive load 20. If the magnitude of the detected current is equal to or less than the first threshold, the detection device 150 determines that neither a short circuit nor a capacitive overload condition exists, and the detection device 150 generates a switch control signal to activate or keep the switch 110 activated and allow the load current to pass through the protection device 100. The first threshold may be close to the current limit. However, due to component tolerances, the first threshold may be about 5% to about 15% lower than the current limit. The second threshold may be greater than about 0.5 V / s. The upper limit of the second threshold may depend on the power handling capability of the switch 110, a safety margin, the capacitive load, the current limit, and the system voltage.

[0040] Rather than using the term "differential signal" herein, it will generally be referred to as "rate of change of switch voltage", "rate of change of voltage drop across the switch", etc., in order to better convey the concepts behind the invention. However, as will be appreciated by those skilled in the art, in the implementation of the protection device 100, decisions made based on the "rate of change of switch voltage" or the "rate of change of voltage drop across the switch" may actually be based on the corresponding differential signal, which may be a voltage signal.

[0041] The gate driver 160 generates a gate control signal for turning on or off the switch 110 based on at least the switch control signal from the detection device 150. The current limiter 170 limits the load current I LOAD does not exceed the current limit. In some embodiments, the current limit can be from about 50 A to about 1200 A. The current limit can be set to about 10 times the rated channel current.

[0042] The protection device 100 may also include a controller 200, which is configured to detect the load current I (from the current sensor 130). LOAD , and provides I2t (current squared time) overload protection and other functions (such as switching on / off) by monitoring the voltage drop across the switch 110 (from a voltage sensor 120) and sending a control signal to the gate driver 160. The controller may also provide reporting functions (such as reporting current and voltage information) to external circuitry.

[0043] FIG 4A illustrates an embodiment of a protection device 100 according to some embodiments of the present disclosure. FIG 4B illustrates a block diagram of a protection device 100-1 in which discrimination is performed by a detection device 150-1 according to some exemplary embodiments of the present disclosure. FIG 4C illustrates an embodiment of a detection device 150 / 150-1 according to some embodiments of the present disclosure.

[0044] The current sensor 130 includes a sense resistor 132 electrically connected in series with the switch 110 and the load 20, and a load current I LOAD and a first error amplifier 134 connected across the first error amplifier 134 to generate a signal corresponding to

[0045] As shown in FIG. 4A, the current limiting function of the current limiter 170 may be realized by a bipolar junction transistor (BJT) 172 (e.g., an NPN BJT) that provides a feedback mechanism to limit the current through the switch 110. When the voltage drop across the first resistor 174 exceeds the base-emitter voltage of the BJT (e.g., 0.6V), the gate of the MOSFET 110 begins to pinch off, limiting the current through the MOSFET 110. Additional signal conditioning blocks may be implemented to meet application-specific needs, such as accuracy, speed, stability, and complexity. However, embodiments of the present disclosure are not limited to the current limiter 170 and any suitable circuit may be utilized.

[0046] A hardware implementation of the differentiator 140 in some examples includes an op-amp differentiator having an op-amp 142, a second resistor 144, and a capacitor 146 in the illustrated configuration. In addition to the elements shown in the differentiator 140 of FIG. 4, other components can be utilized to set the gain and frequency response of the differentiator 140, such that the transfer function can be tailored to a particular desired application of the protection device 100. However, embodiments of the present disclosure are not limited to a circuit implementation of the differentiator 140, and the differentiator can also monitor the voltage generated by the voltage sensor 120 and employ digital algorithms and filtering to calculate the dV DS 4B. The differentiator in this embodiment can be incorporated into the detection device 150-1 which receives the voltage readings from the voltage sensor 120 and performs a differentiation operation to calculate the rate of change of the voltage drop across the switch 110. This is shown in FIG.

[0047] As shown in FIG. 4C, the detection device 150 / 150-1 may include a processor (e.g., a processor or central processing unit (CPU)) 152 and a memory 154 containing instructions that, when executed by the processor 152, perform the operations described above with respect to the detection device 150 / 150-1.

[0048] The terms "processing circuit" and "processor" are used herein to include any combination of hardware, firmware, and software employed to process data or digital signals. Processing circuit hardware includes, for example, application specific integrated circuits (ASICs), general purpose or special purpose central processing units (CPUs), digital signal processors (DSPs), graphic processing units (GPUs), and programmable logic devices such as field programmable gate arrays (FPGAs). In a processing circuit as used herein, each function is performed by either a hardware configured to perform the function, i.e., hardwired, or a plurality of general purpose hardware such as a CPU configured to execute instructions stored in a non-transitory storage medium. The processing circuit may be fabricated on a single printed wiring board (PWB) or distributed across multiple interconnected PWBs. The processing circuit may include other processing circuits. For example, the processing circuit may include two processing circuits, an FPGA and a CPU, interconnected on a printed wiring board.

[0049] 5A-5C are diagrams illustrating turn-on and inrush current control of protection device 100 according to some embodiments of the present disclosure. FIG 5A illustrates the change in current through switch 110 according to some embodiments of the present disclosure. FIG 5B illustrates the change in voltage drop across switch 110 according to some embodiments of the present disclosure. FIG 5C illustrates the output of a differentiation circuit corresponding to the rate of change of switch voltage according to some embodiments of the present disclosure.

[0050] 5A-5C, when protection device 100 is first turned on with a capacitive load, nearly the entire input voltage (e.g., 270V) appears across switch 110 (see FIG. 5B), causing the load current to rapidly surge from zero to a high value, capped at a maximum value (e.g., 540A) by current limiter 170 (see FIG. 5A). The magnitude of the load current may remain capped at this value for some time (e.g., about 0.6 mS) while the capacitive load is charging. During this time, the rate of change of switch voltage (dV DS / dt) is constant (Equation 1, see Figure 5C), and the linear drop in the switch voltage (V DS 5B). The constant rate of change of the switch voltage drop in the example of FIGS. 5A-5C is greater than the second threshold, which is set at 1.5 V. Therefore, even though the switch current exceeds the first threshold of about 450 A, the protection device 100 correctly recognizes the large current as an inrush current of the capacitive load (rather than a short circuit current) and does not shut down the switch 110, thereby allowing the capacitive load to continue charging.

[0051] As the capacitive load 20 charges, the load voltage of the capacitive load 20 rises and the current through the switch falls below the current limit and gradually becomes zero (FIG. 5A). As a result, the switch voltage (V DS ) and its rate of change gradually become zero.

[0052] In some embodiments, the protection device 100 detects a potential short circuit event (i.e., I LOAD > First threshold and dV DS t<t0. / dt<second threshold, the protective device will not trip (or deactivate) switch 110 unless this condition persists for at least a period Δt (e.g., about 50 μS), referred to as a hold-off period. Thus, even if the load current exceeds the first threshold at time ta, after the hold-off period Δt, the load current falls below the first threshold and the short circuit condition no longer exists, so that protective device 100 will not erroneously trip switch 110 and nuisance tripping is avoided.

[0053] Figures 6A - 6C show the trip function of the protection device 100 when a short - circuit state is detected according to some embodiments of the present disclosure.

[0054] Referring to FIGS. 6A - 6C, when the protection device is first turned on to the resistive short - circuit circuit, almost the entire input voltage (e.g., 270V) appears across the switch 110 (see FIG. 6B), and the load current rapidly increases from zero to a high value (see FIG. 6A). When the detected load current exceeds a first threshold (e.g., 450A) at time tb, the rate of change of the voltage drop (dV DS / dt) across the switch is less than a second threshold (e.g., 1.5V). Therefore, the protection device 100 determines that a resistive short - circuit state exists. After a period equal to the hold - off period Δt (e.g., about 12 μS in the present embodiment of FIGS. 6A - 6C), since the condition of the resistive short - circuit still exists, the protection device 100 sends a signal to the gate driver 160 to stop the switch 110. As a result, the load current is immediately interrupted (see FIG. 6A), and damage to the switch 110 and the load 20 is prevented.

[0055] FIG. 7 is a flowchart showing a process 700 for protecting the load circuit 20 according to some embodiments of the present disclosure.

[0056] In some embodiments, the protection device 100 (e.g., the current sensor 130) detects the load current I flowing through the switch 110 (S702) and detects the voltage drop across the switch 110 via the voltage sensor 120 (S704). The protection device 100 (e.g., the differentiator 140) determines the rate of change of the voltage drop across the switch 110 (S706). LOAD

[0057] Next, the protection device 100 (e.g., the detection device 150) determines whether to deactivate the switch 110 based on the load current and the rate of change of the voltage drop across the switch (S708-S716). In this case, the protection device 100 determines whether the load current is greater than a first threshold (S708). If the load current is equal to or less than the first threshold (i.e., the magnitude of the load current is small), the protection device 100 determines that a short circuit event or a capacitive overload condition does not exist, and activates or keeps the switch 110 activated (S710).

[0058] When the load current is greater than the first threshold (i.e., the magnitude of the load current is large), a resistive short circuit condition or a capacitive inrush current may exist, and the protection device 100 attempts to distinguish between these two conditions by determining whether the rate of change of the voltage drop across the switch is less than a second threshold (S712). If the rate of change is greater than or equal to the second threshold (i.e., the rate of change is high), the protection device 100 determines that a capacitive load exists and keeps the switch 110 activated (on) to allow current to flow through the switch 110 (S714) to avoid false nuisance tripping. If the rate of change is less than the second threshold (i.e., the rate of change is low), the protection device 100 determines that a resistive short circuit exists in the load 20. After detecting a short circuit event, the protection device 100 monitors the load current and the rate of change for a hold-off period Δt (e.g., about 50 μS). If the short circuit event still exists after the hold-off period Δt has elapsed, the protection circuit 100 disables (turns off) the switch (S716) to interrupt the high current flowing through the load 20. The hold-off period allows the protection circuit to avoid nuisance tripping of the switch 110.

[0059] Thus, using the measured time rate of change of voltage and the magnitude of the inrush current, the protection device 100 can quickly distinguish between resistive and capacitive inrush currents, facilitating simpler line / load protection circuit designs to protect against resistive short circuits while avoiding nuisance tripping. This solution also provides switching capability for capacitive or pulse energy load systems and can operate with fast switching times without the use of costly and slow-responding pre-charge or soft-start functions.

[0060] The terms used herein are for the purpose of describing particular embodiments and are not intended to limit the inventive concept. As used herein, the singular forms "a" and "an" are intended to include the plural unless the context clearly indicates otherwise. It will be further understood that the terms "comprise", "include", "comprise", "comprises", and / or "consisting of" as used herein specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. A phrase such as "at least one", when preceding a list of elements, modifies the entire list of elements and not the individual elements of the list. Additionally, the use of "may" in describing an embodiment of the inventive concept refers to "one or more embodiments of the inventive concept". Additionally, the term "exemplary" is intended to refer to an example or illustration.

[0061] In this specification, terms such as "first", "second", "third" and the like may be used to describe various elements, components, and / or sections, but it will be understood that these elements, components, and / or sections should not be limited by these terms. These terms are used to distinguish one element, component, or section from another element, component, or section. Thus, a first element, component, or section described below can be referred to as a second element, component, or section without departing from the scope of the inventive concept.

[0062] When an element is referred to as being "connected" or "coupled" to another element, it will be understood that the element may be directly connected or coupled to the other element, or there may be one or more intervening elements. When an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present.

[0063] As used herein, the terms "use", "using", and "used" are considered synonymous with the terms "utilize", "utilize" and "utilized", respectively.

[0064] The protection device and / or any other associated devices or components, e.g., controller and detection device, according to embodiments of the invention described herein may be implemented utilizing any suitable hardware, firmware (e.g., application specific integrated circuit), software, or a suitable combination of software, firmware, and hardware. For example, the various components of the protection device may be implemented on a single integrated circuit (IC) chip, or separate IC chips. Furthermore, the various components of the protection device may be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or may be formed on the same substrate. Furthermore, the various components of the protection device may be processes or threads that run on one or more processors in one or more computing devices, execute computer program instructions, and interact with other system components to perform the various functions described herein. The computer program instructions are stored in a memory that may be implemented in the computing device using standard memory devices, such as, for example, a random access memory (RAM). The computer program instructions may also be stored on other non-transitory computer readable media, such as, for example, a CD-ROM, a flash drive, and the like. Additionally, those skilled in the art should recognize that the functionality of various computing devices may be combined or integrated into a single computing device, or the functionality of a particular computing device may be distributed across one or more other computing devices, without departing from the scope of the exemplary embodiments of the present invention.

[0065] Although the present disclosure has been described in detail with particular reference to exemplary embodiments thereof, the embodiments described herein are not intended to be exhaustive or to limit the scope of the disclosure to the precise forms disclosed. Those skilled in the art to which the present disclosure pertains will recognize that changes and modifications can be made to the described structures and methods of assembly and operation without meaningfully departing from the principles and scope of the present disclosure, as defined in the following claims and their equivalents.

Claims

1. 1. A method for protecting a load circuit, comprising: Detecting a load current through a switch electrically connected in series with the load circuit; Detecting a voltage drop across the switch; determining a rate of change of the voltage drop across the switch; determining whether to disable the switch based on the rate of change of the load current and the voltage drop across the switch; in response to determining to turn off the switch, turning off the switch to interrupt current to the load circuit; The method includes:

2. Determining whether to deactivate the switch comprises: determining whether the load current is greater than a first threshold; determining whether the rate of change of the voltage drop is less than a second threshold; deactivating the switch in response to determining that the load current is greater than the first threshold and the rate of change of the voltage drop is less than the second threshold. The method of claim 1 , comprising:

3. in response to determining not to deactivate the switch, maintaining the activation of the switch; The method of claim 1 or 2, further comprising:

4. Determining whether to deactivate the switch comprises: determining whether the load current is greater than a first threshold; determining whether the rate of change of the voltage drop is less than a second threshold; determining not to disable the switch in response to determining that the load current is less than or equal to the first threshold or that the rate of change of the voltage drop is greater than or equal to the second threshold. The method of any one of claims 1 to 3, comprising:

5. The method of claim 4 , wherein the first threshold is less than a rated current of the switch.

6. The method of claim 1 , wherein the switch comprises a field effect transistor (FET).

7. A protection device connected to a load circuit, comprising: a switch electrically connected in series with the load circuit; a current sensor configured to detect a load current through the switch; a voltage sensor configured to measure a voltage drop across the switch; a detection device configured to generate a switch control signal based on a rate of change of the load current and the voltage drop; a gate driver configured to selectively activate and deactivate the switch based on the switch control signal; A protection device comprising:

8. The switch is a field effect transistor (FET) having a gate electrode connected to the gate driver and a source electrode connected to the load circuit; 8. The protection device of claim 7.

9. The current sensor is a sense resistor electrically connected in series with the switch and the load circuit; Equipped with The voltage sensor is an error amplifier having an input terminal connected across the switch and configured to generate a switch voltage corresponding to the voltage drop across the switch; Equipped with 9. A protection device according to claim 7 or 8.

10. a differentiator connected between the voltage sensor and the detection device, the differentiator configured to generate a differentiated signal corresponding to the rate of change of the voltage drop across the switch based on a switch voltage from the voltage sensor; 10. The protection device of claim 7, further comprising:

11. 11. The protection device of claim 7, wherein the detection device is further configured to receive the voltage drop across the switch from the voltage sensor and to calculate the rate of change of the voltage drop based on the voltage drop.

12. The detection device includes: determining whether the load current is greater than a first threshold; determining whether the rate of change of the voltage drop is less than a second threshold; generating the switch control signal corresponding to disabling the switch in response to determining that the load current is greater than the first threshold and the rate of change of the voltage drop is less than the second threshold.

12. A protection device according to any one of claims 7 to 11, configured to:

13. The detection device includes: determining whether the load current is greater than a first threshold; determining whether the rate of change of the voltage drop is less than a second threshold; generating a switch control signal corresponding to maintaining actuation of the switch in response to determining that the load current is less than or equal to the first threshold or that the rate of change of the voltage drop is greater than or equal to the second threshold.

12. A protection device according to any one of claims 7 to 11, configured to:

14. a current limiter circuit connected between the gate driver and the switch and configured to limit the load current to a limited current. A protection device according to any one of claims 7 to 13.

15. The current limiter circuit includes: a bipolar junction transistor (BJT) having a base, an emitter, and a collector connected to the gate of the switch; the current sensor is connected between the base and emitter of the BJT; 15. The protection device of claim 14.

16. a controller configured to receive the load current and the voltage drop across the switch and to send a signal to the gate driver to disable the switch based on the load current and the voltage drop. A protection device according to any one of claims 7 to 15.

17. 17. A protection device according to any one of claims 7 to 16, wherein the switch comprises a field effect transistor (FET).

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