System and method for differentiating short circuit events in high inrush current circuits

Abstract

A method of protecting a load circuit includes sensing a load current through a switch in electrical series with the load circuit, sensing a voltage drop across the switch, determining a rate of change of the voltage drop across the switch, determining whether to deactivate the switch based on the load current and the rate of change of the voltage drop across the switch, and activating the load circuit. In response to determining to deactivate the switch, the switch is deactivated to cut off current to the load circuit.

Description

Technical Field

[0001] Aspects of embodiments of the present disclosure generally relate to circuit breaker systems. Background Art

[0002] In power systems, switchgear with protection devices, such as solid-state power controllers (SSPCs), are used to control system loads and protect wires from fault currents or short-circuit currents. These devices use information about the load current to react to abnormal conditions. The high inrush currents required for high capacitive loads may be misunderstood by these devices as fault currents. This problem is further exacerbated under higher voltage applications, when the inrush currents of capacitive loads are much higher and cannot be distinguished from short-circuit currents. The switchgear of the related art with protection devices detects these large inrush currents as fault currents and mistakenly shuts down the load, which results in a false trip condition in the system.

[0003] Some prior art techniques address this problem by reducing the inrush current. In some systems, a precharge circuit is used with a capacitive load to limit the inrush current. This technique does not affect the short circuit detection of the upstream protection device of the wires between the power supply and the load; however, it does slow down the load's turn-on response time, which is undesirable. In addition, the precharge circuit system requires additional control hardware and can be quite large, requiring bulky power-consuming components. In airborne applications where weight is a critical factor, this is not a favorable option.

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

[0005] Conventional short circuit detection is based on the load current exceeding a predetermined trip threshold. The short circuit trip value is typically set to ten times the nominal load rated current. When current limiting techniques are utilized, the short circuit current in a short circuit event is also limited, which may interfere with conventional short circuit detection methods. When the conventional short circuit detection method is modified to set the trip threshold to be equal to or less than the limiting load current, a short circuit is detected when the current exceeds this lower trip threshold and lasts longer than a predetermined time to allow the inrush current to be reduced below the trip point. This implementation results in a slow protection response time to avoid false tripping. To prevent nuisance tripping, the short circuit detection system can be large in size and weight to manage the additional power consumption during this waiting time, thereby preventing damage to the solid-state switch. In addition, in high voltage systems such as 270VDC and 540VDC, slow short circuit detection can result in fault current or arc faults, leading to catastrophic events.

[0006] The above information disclosed in this Background section is only for enhancement of understanding of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0007] Various aspects of the embodiments of the present disclosure relate to systems and methods for protecting loads or wires from fault and short circuit currents while allowing rapid charging of capacitive loads. According to some embodiments, a protection device is able to quickly distinguish between high inrush currents and short circuit events of a capacitive load, which allows the protection device to quickly charge and provide power to the capacitive load, and also quickly shut down (trip) in the event of a short circuit event to protect the wiring and prevent device failure.

[0008] According to some embodiments of the present disclosure, a method for protecting a load circuit is provided, the method comprising: sensing a load current passing through a switch electrically connected in series with the load circuit; sensing 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 cut off current to the load circuit.

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

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

[0011] In some embodiments, determining whether to disable the switch includes: determining whether the load current is higher than a first threshold; determining 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, determining not to disable the switch.

[0012] In some embodiments, the first threshold is less than a 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 coupled 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 sense a load current passing through the switch; a voltage sensor configured to measure a voltage drop across the switch; a detector 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 coupled to a gate driver and a source electrode coupled to a load circuit.

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

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

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

[0019] In some embodiments, the detector is configured to perform: determining whether the load current is higher than a first threshold; determining 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 higher than the first threshold and the rate of change of the voltage drop is less than the second threshold, generating a switch control signal corresponding to the deactivation of the switch.

[0020] In some embodiments, the detector is configured to perform: determining whether the load current is above a first threshold; determining 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, generating a switch control signal to correspond to maintaining activation of the switch.

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

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

[0023] In some embodiments, the protection device further includes: a controller configured to receive the load current and a voltage drop across the switch and to signal 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 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.

[0026] Figure 1 A protection device coupled between an input power source and a load according to some exemplary embodiments of the present disclosure is described.

[0027] Figure 2 The relationship between the change rate of the switch voltage and the load capacitance in a constant current scenario according to some exemplary embodiments of the present disclosure is described.

[0028] Figure 3 A block diagram illustrating a protection device according to some exemplary embodiments of the present disclosure.

[0029] Figure 4A Implementation of a protection circuit according to some embodiments of the present disclosure is described.

[0030] Figure 4B A block diagram illustrating a protection device according to some exemplary embodiments of the present disclosure, wherein differentiation is performed by a detector.

[0031] Figure 4C Implementation of a detector according to some embodiments of the present disclosure is described.

[0032] Figure 5A-Figure 5CTurn-on and inrush current control of the protection device 100 according to some embodiments of the present disclosure are described.

[0033] Figure 6A-6C The tripping function of a protection device when a short circuit condition is detected according to some embodiments of the present disclosure is described.

[0034] Figure 7 is a flow chart illustrating a process of protecting a load circuit according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0035] The detailed description set forth below is intended as a description of an example embodiment of a system and method for defect detection provided according to the present disclosure, and is not intended to represent the only form in which the present disclosure may be constructed or utilized. The specification sets forth the features of the present disclosure in conjunction with the illustrated embodiments. However, it should be understood that the same or equivalent functions and structures may be implemented by different embodiments that are also intended to be encompassed within the scope of the present disclosure. As shown elsewhere herein, similar element numbers are intended to indicate similar elements or features.

[0036] Various aspects of the disclosed embodiments relate to a protection device for controlling a system load and protecting an electric line from a fault current or a short circuit current. The present invention is capable of controlling a system load by relying not only on the magnitude of the current passing through a power semiconductor (i.e., a solid-state switch) in accordance with the load, but also on the rate of change of the voltage between the drain and source of the power semiconductor (dV / dt or dV DS / dt) to quickly differentiate between resistive short circuit currents and capacitive inrush currents. This allows the protection device to avoid nuisance tripping (e.g., a switch cuts off current on the wire in the event of a high inrush capacitive current charging a capacitive load) while facilitating simpler wire protection circuit design to protect against short circuit and overload conditions.

[0037] Figure 1 A protection device coupled between an input power source and a load according to some exemplary embodiments of the present disclosure is described.

[0038] In some embodiments, the protection device 100 is located in the current path between the input power source 10 and the system load (e.g., load circuit) 20, and monitors and manages the power transfer between the input source 10 and the load 20. The protection device 100 can be configured to protect the wiring / cable and / or other equipment connected to the electrical load 20 from damage caused by overcurrent from 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 detected fault. In some examples, the protection device 110 can be a circuit breaker (e.g., a thermal circuit breaker or a remote control circuit breaker), a fuse (e.g., a one-time fuse or a resettable fuse), etc. The protection device 100 can accurately measure and report voltage and current measurements, provide low-loss switches with controlled rise and fall times that can reduce EMI emissions, very fast short-circuit response, I2t (current squared over time) overload protection, etc. For example, the load 20 can be a wire / cable, an external circuit, etc.

[0039] When the protection device 100 is turned on to short circuit (ie, when the load 20 is short-circuited), the generated current (I LOAD ) is limited by the impedance of the input source 10 and the entire system. In this case, almost the entire supply voltage V IN Appears across the switch (e.g., a power semiconductor or solid-state switch) 110 of the protection device 100, resulting in high power dissipation. 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 consumed by the switch 110, which may eventually lead to its destruction if not prevented.

[0040] When the protection device 100 is switched on to a capacitive load 20 that has not yet been charged, the effective load impedance is initially a short circuit, resulting in a high inrush current. Also in this case, a high voltage may be generated across the switch 110. As the capacitive load 20 charges, its voltage increases, and the load current I LOAD decreases, thereby reducing the voltage drop across switch 110 over time.

[0041] The protection device 100 utilizes a method to distinguish between inrush current and short circuit current. According to some embodiments, the short circuit detection utilized by the protection device 100 is based not only on the load current, but also on the time rate of change (dV / dt) of the voltage across the terminals of the switch 110. The protection device 100 monitors the load current I through the switch 110. LOAD In some embodiments, the protection device 100 uses a current limiter to prevent the load current I LOADThis is used to maintain a constant current during high current events (e.g., short circuit or high inrush current events). 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 or a resistive short circuit event.

[0042] During a capacitive inrush condition, the voltage variation across the switch 110 behaves identically to the voltage variation across the capacitive load 20, which can be described by the following equation:

[0043]

[0044] The current (I) determines the rate of change of the voltage established across a given capacitive (C) load. The constant current is controlled by the protection device 100, so the dV / dt in the above equation can be accurately measured to determine the load capacitance value. In some examples, the constant current value (i.e., the current limit) is set to be lower than the maximum current that the switch 110 can withstand during the charging cycle without being damaged. For example, the current limit can be set to about 600A, 1200A, or any other value suitable for the desired application.

[0045] Figure 2 The relationship between the change rate of the switch voltage and the load capacitance in a constant current scenario according to some exemplary embodiments of the present disclosure is described.

[0046] exist Figure 2 In the example of FIG. 1 , the protection device 100 operates in a current limiting mode (eg, a current upper limit of 600 A / limited to 600 A). As described in equation (1) and Figure 2 As shown, the smaller the capacitance value of the load 20, the higher the rate of change (dV / dt) of the switch voltage. Similarly, the larger the capacitance value, the smaller the dV / dt value. In some embodiments, when the current is high and the dV / dt is below a certain threshold (e.g., 1.5), the capacitance value is considered to be very high. In this case, the load is considered to be capacitive and the high current is considered to be a capacitive inrush current. When the current is high but the dV / dt is above the threshold, the load capacitance is small and the high current is considered to be the result of a resistive short circuit. For a given current limit, the threshold of dV / dt can be selected within the high slope region of the dV / dt vs. capacitance curve to improve detection accuracy.

[0047] Figure 3 A block diagram illustrating a protection device 100 according to some exemplary embodiments of the present disclosure.

[0048] In some embodiments, the protection device 100 includes a switch (e.g., a power semiconductor or a solid-state switch) 110, a voltage sensor 120, a current sensor 130, a differentiator 140, a detector 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 an nFET) whose drain and source terminals are connected between the input source 10 and the load 20. The voltage sensor 120 may be an operational amplifier (e.g., an error amplifier) ​​whose input terminal is connected between the source terminal and the drain terminal of the switch 110 and is configured to measure a voltage drop across the switch 110 (e.g., measuring a drain-source voltage V DS ) and generates a corresponding switch voltage. The differentiator (e.g., a differentiator circuit) 140 is coupled between the voltage sensor 120 and the detector 150 and is configured to generate a rate of change (dV ) corresponding to the voltage drop across the switch 110 based on the switch voltage from the voltage sensor 120. DS The current sensor 130 is electrically connected in series with the switch 110 and is configured to measure the load current I LOAD The current sensor 130 may be a sensing resistor, the voltage across which corresponds to the current passing through it.

[0049] According to some embodiments, the detector (eg, short circuit / overload detector) 150 is configured to detect the load current I LOADThe detector 150 can detect resistive short circuit events and capacitive overload conditions quickly by using the sensed current and 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 sensed current is high (i.e., the sensed current is greater than the first threshold) and the rate of change of the voltage across the switch 110 is low (i.e., the rate of change is less than the second threshold), the detector 150 determines that the high current is the result of a resistive short circuit, and generates a switch control signal to deactivate / turn off the switch 110. This can prevent damage to the switch 110 and / or the load 20 that might otherwise be caused by such a resistive short circuit condition. In addition, when the magnitude of the sensed current is high (i.e., the sensed current is greater than the first threshold) and the rate of change of the voltage across the switch 110 is also high (i.e., the rate of change is greater than or equal to the second threshold), the detector 150 determines that the high current is due to an inrush current into the capacitive load, and generates a switch control signal to maintain the activated / on state of the switch 110. As a result, in this case, the protection device 100 does not erroneously turn off the switch 110 and allow a high current to pass in order to charge the capacitive load 20. When the magnitude of the sensed current is less than or equal to the first threshold, the detector 150 determines that there is neither a short circuit event nor a capacitive overload condition, and the detector 150 generates a switch control signal to activate or maintain the activation state of the switch 110 and allow the load current to pass through the protection device 100. The first threshold may be a value 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 value. 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, the safety margin, the capacitive load, the current limit, and the system voltage.

[0050] In the description herein, reference is often made to "rate of change of switch voltage", "rate of change of voltage drop across switch", etc., rather than using the term "differential signal". This is done to better convey the concept behind the present invention. However, as will be appreciated by one of ordinary skill in the art, in embodiments of the protection device 100, the determination made based on "rate of change of switch voltage" or "rate of change of voltage drop across switch" may actually be based on a corresponding differential signal, which may be a voltage signal.

[0051] The gate driver 160 generates a gate control signal to activate or deactivate the switch 110 based at least on the switch control signal from the detector 150. The current limiter 170 ensures that the load current I LOAD The current limit is not exceeded. In some examples, the current limit may be about 50 A to about 1200 A. The current limit may be set to about 10 times the rated current of the channel.

[0052] The protection device 100 may further include a controller 200, which monitors the load current ILOAD The controller senses the voltage drop across the switch 110 (from the current sensor 130) and the voltage drop across the switch 110 (from the voltage sensor 120), and provides I2t (current squared over time) overload protection and other functions (such as turning the switch on / off) by transmitting control signals to the gate driver 160. The controller can also provide reporting functions (such as reporting current and voltage information) to external circuits.

[0053] Figure 4A The implementation of the protection device 100 according to some embodiments of the present disclosure is described. Figure 4B A block diagram illustrating a protection device 100 - 1 according to some exemplary embodiments of the present disclosure, wherein differentiation is performed by a detector 150 - 1 . Figure 4C Implementation of the detector 150 / 150 - 1 according to some embodiments of the present disclosure is described.

[0054] The current sensor 130 may include: a sensing resistor 132 electrically coupled in series with the switch 110 and the load 20; and a first error amplifier 134 coupled across the first error amplifier 134 for generating a current corresponding to the load current I LOAD The signal is transmitted to the detector 150 and the controller 200.

[0055] like Figure 4A As shown, the current limiting function of the current limiter 170 can be implemented by a bipolar junction transistor (BJT) 172 (e.g., an NPN BJT), which 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 and the current through the MOSFET 110 is limited. Additional signal conditioning blocks can be implemented to achieve specific requirements of the application, 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 can be utilized.

[0056] In some examples, the hardware implementation of the differentiator 140 includes an operational amplifier differentiator circuit having an operational amplifier 142, a second resistor 144, and a capacitor 146 in the illustrated configuration. In addition to the elements shown in the differentiator circuit 140 of FIG. 4, other components may be utilized to set the gain and frequency response of the differentiator 140 to tune the transfer function to a particular desired application of the protection device 100. However, the embodiments of the present disclosure are not limited to the circuit implementation of the differentiator 140, and the differentiator may also be implemented with the aid of software that monitors the voltage generated by the voltage sensor 120 and employs a digital algorithm and filtering to determine dV DSIn such an example, a differentiator may be incorporated into the detector 150-1 that receives the voltage reading from the voltage sensor 120 and performs a differentiation operation to calculate the rate of change of the voltage drop across the switch 110. Figure 4B In the description.

[0057] like Figure 4C As shown, the detector 150 / 150-1 may include processing circuitry (e.g., a processor or central processing circuit (CPU)) 152 and a memory 154 including instructions that, when executed by the processor 152, perform the operations described above with respect to the detector 150 / 150-1.

[0058] The terms "processing circuit" and "processor" are used herein to include any combination of hardware, firmware, and software for processing data or digital signals. Processing circuit hardware may include, for example, an application-specific integrated circuit (ASIC), a general or dedicated central processing unit (CPU), a digital signal processor (DSP), a graphics processing unit (GPU), and a programmable logic device such as a field programmable gate array (FPGA). As used herein, in a processing circuit, each function is either performed by hardware configured (i.e., hardwired) to perform the function, or by more general hardware (such as a CPU) configured to execute instructions stored in a non-temporary storage medium. The processing circuit may be manufactured on a single printed wiring board (PWB) or distributed on several interconnected PWBs. The processing circuit may contain other processing circuits; for example, the processing circuit may include two processing circuits interconnected on a PWB, i.e., an FPGA and a CPU.

[0059] Figure 5A-Figure 5C Turn-on and inrush current control of the protection device 100 according to some embodiments of the present disclosure are described. Figure 5A The change of the current passing through the switch 110 according to some embodiments of the present disclosure is illustrated. Figure 5B The change of the voltage drop across the switch 110 according to some embodiments of the present disclosure is illustrated. Figure 5C The output of a differentiator circuit corresponding to a rate of change of a switch voltage according to some embodiments of the present disclosure is illustrated.

[0060] refer to Figure 5A-Figure 5C When the protection device 100 is first connected to the capacitive load, almost the entire input voltage (eg, 270V) appears across the switch 110 (see Figure 5B ), and the load current surges rapidly from zero to a high value, which is capped by the current limiter 170 at a maximum value (e.g., 540A) (see Figure 5A). When the capacitive load is being charged, the magnitude of the load current can remain capped at this value for a period of time (e.g., about 0.6 mS). During this period, the rate of change of the switch voltage (dV DS / dt) is constant (see Equation 1, Figure 5C ), which is caused by the linear decrease of the switch voltage (V DS ; See Figure 5B ) to reflect. Figure 5A-Figure 5C In the example of FIG. 1 , the constant rate of change of the switch voltage drop is greater than the second threshold value set at 1.5 V. Therefore, although the high switch current exceeds the first threshold value of about 450 A, the protection device 100 correctly identifies the high current as an inrush current of the capacitive load (rather than a short circuit current) and does not deactivate the switch 110, which allows the capacitive load to continue charging.

[0061] As the capacitive load 20 is charged, the load voltage of the capacitive load 20 increases and the current through the switch drops below the current limit and gradually decreases to zero ( Figure 5A As a result, the switch voltage (V DS ) and its rate of change gradually decrease to zero.

[0062] In some embodiments, when the protection device 100 detects a potential short circuit event (ie, I LOAD > first threshold and dV DS / dt<second threshold value), the protection device will not trip (or disable) the switch 110 unless this condition lasts for at least a period of time Δt (e.g., about 50 μS), which is referred to as the hold-off period. Therefore, at time ta, even if the load current exceeds the first threshold value, since the load current is lower than the first threshold value after the hold-off period Δt and the short-circuit condition no longer exists, the protection device 100 will not trip the switch 110 in error, and nuisance tripping is avoided.

[0063] Figure 6A-6C The tripping function of the protection device 100 when a short circuit condition is detected according to some embodiments of the present disclosure is described.

[0064] refer to Figure 6A-6C When the protection device is first switched on as a resistive short, almost the entire input voltage (eg, 270 V) appears across switch 110 (see Figure 6B ), and the load current surges rapidly from zero to a high value (see Fig. 6A When the sensed load current exceeds a first threshold value (eg, 450A) at time tb, the rate of change of the voltage drop across the switch (dV DS / dt) is less than a second threshold value (e.g., 1.5V). Therefore, the protection device 100 determines that a resistive short circuit condition exists. After a period of time equal to the delay time Δt (e.g., Figures 6A-6C In the example of FIG. 1 , about 12 μS), the resistive short circuit condition still exists, so the protection device 100 signals the gate driver 160 to disable the switch 110. This results in an immediate cutoff of the load current (see Fig. 6A ), which prevents damage to the switch 110 and the load 20.

[0065] Figure 7 is a flow chart illustrating a process 700 of protecting a load circuit 20 according to some embodiments of the present disclosure.

[0066] In some embodiments, the protection device 100 (eg, the current sensor 130 ) senses the load current I passing through the switch 110 LOAD (S702), and senses a voltage drop across the switch 110 via the voltage sensor 120 (S704). The protection device 100 (eg, the differentiator 140) determines a rate of change of the voltage drop across the switch 110 (S706).

[0067] Then, the protection device 100 (e.g., the detector 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). By doing so, the protection device 100 determines whether the load current is higher than the first threshold (S708). When the load current is less than or equal to the first threshold (i.e., when the magnitude of the load current is low), the protection device 100 determines that there is no short circuit event or capacitive overload condition, and activates or maintains the activation state of the switch 110 (S710).

[0068] When the load current is greater than the first threshold (i.e., when the magnitude of the load current is high), there may be a resistor short circuit condition or a capacitive inrush current, 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). When 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 there is a capacitive load, and allows current to pass through the switch 110 by keeping the switch 110 activated (S714), thereby avoiding a false barrier trip. When the rate of change is less than the second threshold (i.e., the rate of change is low), the protection device 100 determines that there is a resistive short circuit at the load 20. After detecting a short circuit event, the protection device 100 monitors the load current and the rate of change for a duration of a delay period Δt (e.g., about 50 μS). If the short circuit event still exists after the delay period Δt has passed, the protection circuit 100 proceeds to deactivate the switch to cut off the high current to the load 20 (S716). The delay period allows the protection circuit to avoid a barrier trip of the switch 110.

[0069] Thus, the protection device 100 is able to quickly differentiate between resistive and capacitive inrush currents by using the measured time rate of change of voltage and the magnitude of the inrush current to avoid nuisance tripping while facilitating simpler line / load protection circuit design to prevent resistive shorts. This solution also provides switching capability for capacitive load systems or pulse energy loads to operate with fast switching times without expensive and slow-responding pre-charge or soft-start functions.

[0070] The terms used herein are used for the purpose of describing a particular embodiment and are not intended to limit the inventive concept. As used herein, the singular forms "one" and "an" are also intended to include plural forms unless the context clearly indicates otherwise. It should be understood in addition that the terms "include", "including", "comprises" and / or "comprising" specify the presence of the features, integers, steps, operations, elements and / or parts when used in this specification, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or their groups. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. When before the element list, expressions such as "at least one of ..." modify the entire element list without modifying the individual elements of the list. In addition, when describing the embodiments of the inventive concept, "may" is used to refer to "one or more embodiments of the inventive concept". In addition, the term "exemplary" is intended to refer to an example or explanation.

[0071] It should be understood that although the terms "first", "second", "third", etc. may be used herein to describe various elements, components and / or parts, these elements, components and / or parts should not be limited by these terms. These terms are used to distinguish one element, component or part from another element, component or part. Therefore, without departing from the scope of the present invention, the first element, component or part discussed below may be referred to as a second element, component or part.

[0072] It should be understood that when an element is referred to as being "connected to" or "coupled to" another element, it may be directly connected to or coupled to the other element, or one or more intervening elements may be present. When an element is referred to as being "directly connected to" or "directly coupled to" another element, there are no intervening elements.

[0073] As used herein, the terms "use," "using," and "used" may be considered synonymous with the terms "utilize," "utilizing," and "utilized," respectively.

[0074] The protection device and / or any other related devices or components (such as controllers and detectors) according to the embodiments of the present invention described herein can be implemented using any suitable hardware, firmware (such as a dedicated integrated circuit), software, or a suitable combination of software, firmware, and hardware. For example, the various components of the protection device can be formed on an integrated circuit (IC) chip or on a separate IC chip. In addition, the various components of the protection device can be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or formed on the same substrate. In addition, the various components of the protection device can 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 various functions described herein. Computer program instructions are stored in a memory that can be implemented in a computing device using a standard memory device such as a random access memory (RAM). Computer program instructions can also be stored in other non-temporary computer-readable media such as CD-ROMs, flash drives, etc. In addition, those skilled in the art should recognize that without departing from the scope of the exemplary embodiments of the present invention, the functions of various computing devices can be combined or integrated into a single computing device, or the functions of a specific computing device can be distributed on one or more other computing devices.

[0075] Although the present disclosure has been described in detail with particular reference to the illustrative embodiments of the present disclosure, the embodiments described herein are not intended to be exhaustive or to limit the scope of the present disclosure to the precise forms disclosed. Those skilled in the art and technology to which the present disclosure belongs will appreciate that changes and variations may 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 set forth in the appended claims and their equivalents.

Claims

1. A method for protecting a load circuit, the method comprising: sensing a load current through a switch electrically connected in series with the load circuit; sensing 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; as well as In response to determining to deactivate the switch, The switch is deactivated to cut off current flow to the load circuit.

2. The method of claim 1, wherein the determining whether to disable the switch comprises: determining whether the load current is higher than a first threshold; determining 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 above the first threshold and the rate of change of the voltage drop is less than the second threshold, Make sure to deactivate the switch.

3. The method according to any one of claims 1 to 2, further comprising: In response to determining not to deactivate the switch, The switch is maintained activated.

4. The method according to any one of claims 1 to 3, wherein the determining whether to disable the switch comprises: determining whether the load current is higher than a first threshold; determining 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, Make sure not to deactivate the switch. The method of claim 4 , wherein the first threshold is less than a rated current of the switch.

6. The method of any one of claims 1 to 5, wherein the switch comprises a field effect transistor (FET).

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

8. The protection device according to claim 7, wherein the switch comprises: A field effect transistor (FET) has a gate electrode coupled to the gate driver and a source electrode coupled to the load circuit.

9. The protection device according to any one of claims 7 to 8, wherein the current sensor comprises: a sense resistor electrically coupled in series with the switch and the load circuit, and The voltage sensor comprises: An error amplifier has an input terminal coupled across the switch and is configured to generate a switch voltage corresponding to the voltage drop across the switch.

10. The protection device according to any one of claims 7 to 9, further comprising: A differentiator is coupled between the voltage sensor and the detector and is configured to generate a differential signal corresponding to the rate of change of the voltage drop across the switch based on a switch voltage from the voltage sensor. 11 . The protection device according to claim 7 , wherein the detector is further configured to receive the voltage drop across the switch from the voltage sensor and calculate the rate of change of the voltage drop based on the voltage drop.

12. The protection device according to any one of claims 7 to 11, wherein the detector is configured to perform: determining whether the load current is higher than a first threshold; determining 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 above the first threshold and the rate of change of the voltage drop is less than the second threshold, The switch control signal is generated corresponding to deactivation of the switch.

13. The protection device according to any one of claims 7 to 11, wherein the detector is configured to perform: determining whether the load current is higher than a first threshold; determining 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, The switch control signal is generated corresponding to maintaining activation of the switch.

14. The protection device according to any one of claims 7 to 13, further comprising: A current limiter circuit is coupled between the gate driver and the switch and is configured to limit the load current to a current limit.

15. The protection device of claim 14, wherein the current limiter circuit comprises: A bipolar junction transistor (BJT) has a base, an emitter, and a collector coupled to the gate of the switch, and the current sensor is coupled between the base and the emitter of the BJT.

16. The protection device according to any one of claims 7 to 15, further comprising: A controller is configured to receive the load current and the voltage drop across the switch and to signal the gate driver to disable the switch based on the load current and the voltage drop.

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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