System and method for controlling current between power source and load

Abstract

Disclosed is a system (100), arranged between a power source (110) and a load (120), and a method (200) for controlling current. The system includes a first semiconductor switch (130) with a first (131) and a second terminal (132), and a second semiconductor switch (140) with a first (141) and a second terminal (142), connected to the power source and the load, respectively. The system includes a first driver (103) and a second driver (104), connected to control the respective semiconductor switches, via a control circuit (105). The control circuit is configured to initiate a pre-charge cycle by detecting a connection status between the power source and the load, activating the second semiconductor switch into saturation, and modulating the first semiconductor switch through its linear region by adjusting the first signal within a specified period, controlling the first semiconductor switch from a non-conductive to a fully conductive state.

Description

[0001] SYSTEM AND METHOD FOR. CONTROLLING CURRENT BETWEEN POWER

[0002] SOURCE AND LOAD

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to system for controlling current, configured to be arranged between a power source and a load. Moreover, the present disclosure relates to a method for controlling current by the system.

[0005] BACKGROUND

[0006] In electrical systems, particularly those involved in DC EV-charging and other battery charging applications, managing inrush current during the initial connection phase is important. The inrush current, if not properly controlled, may lead to significant voltage spikes and potential damage to system components. Traditionally, the process of pre-charging, which aims to gradually equalize the voltage levels between a power source and a load before full connection, has been a standard practice to mitigate these risks. This pre-charge phase ensures a smooth transition to full system operation, minimizing electrical stress and enhancing system stability.

[0007] Conventionally, pre-charge systems for DC EV-charging and other battery charging systems have relied on mechanical relays and resistors to limit inrush current and leveling voltage level between voltage output of the power source and input of the load. This approach, however, requires large, costly relays for high-voltage applications, complicating the design and increasing the size and expense of the system. Also it requires an extra control line for the relay / contactor from the system controller. In some cases, such pre-charge current limiting resistor needs thermal cooling, which may further complicate the design. Further, the mechanical construction for such systems is complicated because of possible high voltages, and may furthermore require physical isolation along with physically big components, leading to further complexities and costs.

[0008] Therefore, in the light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks.

[0009] SUMMARY

[0010] The aim of the present disclosure is to provide a system and a method for controlling current between a power source and a load, addressing the limitations associated with conventional pre-charge systems. The aim of the present disclosure is achieved by a system and a method, as defined in the appended independent claims, which employ semiconductor switches, replacing traditional mechanical relays and resistors, to regulate inrush current and manage voltage levels between a power source and a load. By utilizing the linear conduction properties of semiconductors, this present disclosure provides a more compact, cost-effective, and reliable solution compared to conventional pre-charge systems. Advantageous features and additional implementations are set out in the appended dependent claims.

[0011] Throughout the description and claims of this specification, the words "comprise", "include", "have", and "contain" and variations of these words, for example "comprising" and "comprises", mean "including but not limited to", and do not exclude other components, items, integers or steps not explicitly disclosed also to be present. Moreover, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is an illustration of schematic block diagram of a system for controlling current, configured to be arranged between a power source and a load, in accordance with embodiments of the present disclosure;

[0013] FIG. 2 is an illustration of a flowchart listing steps of a method for controlling current between a power source and a load, in accordance with embodiments of the present disclosure.

[0014] FIG. 3 is an illustration of a control curve for timing of pre-charge, when a connection element is fully in conductive state, in accordance with embodiments of the present disclosure; and

[0015] FIG. 4 is an illustration of a graph of linear region of a switch with various voltage input for switch gate-pin, in accordance with embodiments of the present disclosure.

[0016] DETAILED DESCRIPTION OF EMBODIMENTS

[0017] The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practising the present disclosure are also possible.

[0018] In a first aspect, the present disclosure provides system for controlling current, configured to be arranged between a power source and a load, the system comprising:

[0019] - a first semiconductor switch and a second semiconductor switch, wherein a first terminal of the first semiconductor switch is connected to a first rail of the power source and a second terminal of the first semiconductor switch is connected to a first rail of the load, and a first terminal of the second semiconductor switch is connected to a second rail of the power source and a second terminal of the second semiconductor switch is connected to a second rail of the load;

[0020] - a first driver and a second driver, wherein an output of the first driver is connected to a third terminal of the first semiconductor switch, and an output of the second driver is connected to a third terminal of the second semiconductor switch; and

[0021] - a control circuit connected to an input of the first driver and an input of the second driver, wherein the control circuit is configured to:

[0022] - detect whether the power source has been connected to, or disconnected from, the load, and when it is detected that the power source has been connected to the load, initiate a pre-charge cycle by controlling the second driver to output a second signal to turn on the second semiconductor switch, to operate it in a saturation region;

[0023] - upon initiating, control the first driver to output a first signal to the first semiconductor switch to operate it in a linear region; and

[0024] - control flow of current through the first semiconductor switch in the linear region by adjusting, during a first period of time, the first signal from a first value, through a range of values, to a second value, wherein the first value corresponds to a value in which the first semiconductor switch is not conducting, or it has not been fully turned on, and the second value corresponds to a value in which the first semiconductor switch has been fully turned on.

[0025] The system of the present disclosure is configured for managing current flow between the power source and the load, particularly during the precharging cycle. The system provides control over inrush current during the initial connection phase between the power source and the load by using semiconductor switches in place of traditional mechanical relays. By activating the second semiconductor switch to operate in its saturation region, the system provides a controlled ramp-up of current through the first semiconductor switch. The adjustment of the first signal, based on real-time conditions and predetermined parameters, allows the system to fine-tune the current flow to the requirements of the load. Further, the drivers ensure that the signals from the control circuit are translated into the operational states of the semiconductor switches. These features ensures that the system can provide optimal electrical performance while providing protection against potential damages associated with inrush currents.

[0026] In a second aspect, the present disclosure provides a method for controlling current by the aforementioned system, the method comprising:

[0027] - detecting, by a control circuit, whether a power source has been connected to / disconnected from a load;

[0028] - initiating a pre-charge cycle, by the control circuit, when it is detected that the power source has been connected to the load, by controlling a second driver to output a second signal to turn on a second semiconductor switch;

[0029] - upon initiating the pre-charge cycle, controlling the first driver, by the control circuit, to output a first signal to the first semiconductor switch to operate it in a linear region, wherein the first signal has initially a first value; and

[0030] - activating the pre-charge cycle, and upon activating of the precharge cycle, controlling, by the control circuit, flow of current through the first semiconductor switch in the linear region by adjusting the first signal from the first value to a second value as a function of time, wherein the second value corresponds to a value in which the first semiconductor switch has been fully turned on.

[0031] The method of the present disclosure provides a sequence of operations for controlling the electrical current during the pre-charge cycle. The method combines the components and functionalities of the aforementioned system to ensure a safe and efficient power transfer from the power source to the load. The method involving detection of the connection from the power source to the load, controlled initiation, and precise modulation of the pre-charge cycle, to enhance performance, reliability, and adaptability of such electrical systems to varying operational conditions.

[0032] The present disclosure provides the aforementioned system for controlling current between the power source and the load. The power source, in present context, may be any power supply capable of providing the necessary energy for intended application of the system, such as electric vehicle (EV) charging stations, energy storage systems, or other electric-powered systems. The load, on the other hand, represents the device or system that requires electrical power from the power source. The load may include an EV battery in the context of charging stations, energy storage devices, or any other electrical system that necessitates controlled power delivery.

[0033] The system is configured to address the challenges associated with inrush currents that typically occur when the power source is initially connected to the load, specifically for use in pre-charge applications. The term "inrush currents" refers to the initial surge of electrical current that occurs when the power source is first connected to the load. This surge typically happens at the moment of connection due to the inherent differences in voltage between the power source and the uncharged load or due to the capacitive or inductive characteristics of the load itself. The "pre-charge cycle," in present context, refers to the process to mitigate the effects of inrush currents by gradually equalizing the voltage levels between the power source and the load before establishing a full electrical connection. This is achieved by initially allowing a small, controlled amount of current to flow from the power source to the load, thereby slowly charging any capacitive elements and reducing the impedance encountered by the power source. The system is configured to be arranged between the power source and the load for its operation. By disposition between the power source and the load, the system acts as an intermediary controller that directly controls the electrical current from the power source to the load. Such arrangement of the system aids with initiating the pre-charge cycle, a process in which the system gradually equalizes the voltage levels between the power source and the load before allowing the full current to flow, thereby ensuring a smooth and controlled power-up phase. Herein, the system is configured to provide a controlled, gradual increase in current flow from the power source to the load, thereby preventing abrupt voltage spikes and potential damage to the electrical components involved.

[0034] In present embodiments, optionally, the power source is a direct-current power supply. That is, the system uses the DC power supply as the power source. This choice is particularly relevant for applications like EV charging stations and energy storage systems, where DC power is a standard. The nature of DC power, characterized by its unidirectional flow and constant voltage, makes it ideal for such applications, ensuring efficiency and reliability in the charging or power delivery processes. The direct-current supply ensures a steady flow of electricity, providing a stable and consistent power input for operation of the system.

[0035] Further, optionally, the load comprises a capacitor. The capacitors, known for their ability to store and release electrical energy, are inherently susceptible to inrush currents due to their initial low resistance when uncharged. As the capacitor charges, its resistance increases until it reaches a steady state where the capacitor is fully charged. The use of the capacitor in the system ensures that the capacitor within the load can be safely and gradually charged. This gradual charging process prevents the potential harm that could arise from a sudden inrush of current, thereby protecting the capacitor and ensuring the stability of the system as a whole. The system comprises the first semiconductor switch and the second semiconductor switch, wherein the first terminal of the first semiconductor switch is connected to the first rail of the power source and the second terminal of the first semiconductor switch is connected to the first rail of the load, and the first terminal of the second semiconductor switch is connected to the second rail of the power source and the second terminal of the second semiconductor switch is connected to the second rail of the load. As used herein, the "semiconductor switch" refers to an electronic device that can control the flow of electrical current in a circuit. The semiconductor switch operates based on the properties of semiconductor materials, which allow it to switch between conducting and non-conducting states under the influence of electrical signals. In the system, semiconductor switches (the first and second semiconductor switches) are employed to manage the current flow during the pre-charge cycle, replacing traditional mechanical relays. The term "terminal" denotes a connection point on or associated with the semiconductor switch through which electrical current enters or exits the semiconductor switch. Further, the term "rail" refers to the conductive paths within the power source and the load that carry electrical current.

[0036] Herein, the first terminal of the first semiconductor switch is connected to the first rail of the power source and the second terminal of the first semiconductor switch is connected to the first rail of the load, establishing a direct pathway for current flow from the power source to the load. Such connection ensures that the first semiconductor switch acts as a gatekeeper for the current flowing from the power source to the load, allowing for control over the current flow therebetween. Further, the second semiconductor switch has a configuration mirroring that of the first semiconductor switch but caters to the opposite polarity. The first terminal of the second semiconductor switch is connected to the second rail of the power source, while the second terminal of the second semiconductor switch is connected to the second rail of the load. This arrangement ensures that both positive and negative currents are equally managed, ensuring complete control of the system over the entire electrical circuit.

[0037] More specifically, the first and second semiconductor switches are configured to ensure controlled current flow between the power source and the load, effectively managing the pre-charge phase to mitigate inrush current. In the pre-charge cycle, the ability of the semiconductor switches to operate in a linear conduction range is utilized. This functionality allows the semiconductor switches to simulate the behavior of an adjustable resistor, providing control over the current flow which may not be possible with traditional mechanical relays. By adjusting the conductivity of at least one of the semiconductor switches, the system is configured to modulate the current flow from the power source semiconductor switches to the load, providing a controlled increase in current that aligns with the optimal pre-charge requirements of the system.

[0038] In an embodiment, each of the first semiconductor switch and second semiconductor switch is at least one of: a metal-oxide-semiconductor field-effect-transistor, a junction field-effect-transistor, an insulated-gate bipolar transistor, a bipolar junction transistor. That is, the first and second semiconductor switches may be constituted by a range of semiconductor devices, each with unique properties suited for specific aspects of the system's operation. These include the metal-oxide- semiconductor field-effect-transistors (MOSFETs), utilized for their high efficiency and fast switching capabilities; the junction field-effect- transistors (JFETs), utilized for their robustness and reliability; the insulated-gate bipolar transistors (IGBTs), utilized for their high power handling and ease of control; and the bipolar junction transistors (BJTs), utilized for their linearity and high current capacity. The selection among these options is typically based on the specific requirements of the application, such as the required switching speed, power handling capabilities, and efficiency levels.

[0039] Further, in an embodiment, the first rail is a positive rail and the second rail is a negative rail. The first and second rails provide two distinct pathways for the flow of electrical current from the power source to the load. Herein, the first rail serves as the positive rail and the second rail serves as the negative rail. This ensures that the system can accommodate and manage the direct current (DC) flow properly, aligning with the conventional representation of electrical circuits where current flows from a positive to a negative potential.

[0040] The system also includes the first driver and the second driver, wherein the output of the first driver is connected to the third terminal of the first semiconductor switch, and the output of the second driver is connected to the third terminal of the second semiconductor switch. The "driver," within the present system, refers to an electronic circuit or module configured to control the operation of the corresponding semiconductor switch. Particularly, the driver is configured to receive control signals from the control circuit and translate these signals into appropriate gate voltages or currents that directly control operation of the corresponding semiconductor switch. The driver acts as an intermediary, amplifying and shaping the control signals to ensure they are of sufficient magnitude and form to effectively modulate conductive state of the corresponding semiconductor switch. Further, the terms "input" and "output," in this context, refers to signal received from the control circuit and delivered by the driver to the third terminal (often the gate) of the corresponding semiconductor switch it controls, respectively.

[0041] The system further includes the control circuit connected to the input of the first driver and the input of the second driver. Herein, the "control circuit" refers to an electronic circuit designed to control the operation of the semiconductor switches, via the drivers, within the system based on specific inputs and predefined logic. The control circuit typically comprises a combination of analog and digital components, including microcontrollers, sensors, and other electronic devices, configured to process inputs, execute logic operations, and generate appropriate outputs. In the context of the present system, the control circuit is configured to perform a variety of functions, including but not limited to, detecting the connection status between the power source and the load, initiating and managing the pre-charge cycle, and controlling the operation of semiconductor switches through their respective drivers (as discussed later in more detail).

[0042] The operation of the first and second drivers is synchronized with commands from the control circuit, which control the initiation of the precharge cycle. Herein, by varying the signals sent to the third terminals, the first and second drivers may modulate conductivity of the corresponding one of semiconductor switches, effectively controlling the current flow from the power source to the load through the respective one of first and second rails. This modulation allows the system to control the flow of current through the semiconductor switches, facilitating the gradual increase of current characteristic of the pre-charge cycle. Specifically, by tuning the signals to the semiconductor switches, the drivers may adjust the conductivity of the semiconductor switches from a high-resistance state to a low-resistance state. This gradual adjustment allows for a controlled ramp-up of current, preventing the sudden inrush currents that could otherwise occur when connecting the power source to the load directly.

[0043] In the system, the control circuit is configured to detect whether the power source has been connected to, or disconnected from, the load, and when it is detected that the power source has been connected to the load, initiate the pre-charge cycle by controlling the second driver to output the second signal to turn on the second semiconductor switch, to operate it in the saturation region. Herein, typically, the detection process involves monitoring voltage levels, impedance changes, or other electrical signals that signify a connection between the power source and the load. Upon detecting that the power source has been successfully connected to the load, the control circuit is configured to initiate the precharge cycle. This prepares the system for a transition to full operational status, mitigating the risks associated with sudden inrush currents. For this purpose, the control circuit commands the second driver to output a signal, referred to as the second signal, to the second semiconductor switch. The second signal instructs the second semiconductor switch to enter into its saturation region, a state where the switch is fully conductive, allowing current to flow through with minimal resistance. By ensuring that the second semiconductor switch is fully turned on, the system establishes a stable pathway for current flow from the power source, via the second rail.

[0044] The control circuit is further configured to, upon initiating, control the first driver to output the first signal to the first semiconductor switch to operate it in a linear region. That is, following the initiation of the precharge cycle, as facilitated by activation of the second semiconductor switch into its saturation region, the control circuit sends command to the first driver, instructing it to generate and output a signal, referred to as the first signal, for the first semiconductor switch. The first signal is calibrated to engage the first semiconductor switch in a specific operational mode known as the linear region. The linear region provides that the first semiconductor switch, while conducting, does not yet allow the maximum possible current to flow through; instead, it operates similar to a variable resistor, whose resistance can be finely adjusted through changes in the gate voltage provided by the first signal. By modulating conductivity of the first semiconductor switch in this manner, the system can precisely control the rate at which the current increases, ensuring a gradual and controlled ramp-up. This controlled approach mitigates the risks associated with inrush currents. The control circuit is further configured to control flow of current through the first semiconductor switch in the linear region by adjusting, during a first period of time, the first signal from the first value, through the range of values, to the second value, wherein the first value corresponds to a value in which the first semiconductor switch is not conducting, or it has not been fully turned on, and the second value corresponds to a value in which the first semiconductor switch has been fully turned on. That is, once the first semiconductor switch is operating within the linear region (as discussed in the preceding paragraph), the control circuit dynamically adjusts the first signal, which is directed towards the first semiconductor switch, over a specified duration, referred to as the first period of time, to control the flow of current through the first semiconductor switch. This adjustment involves transitioning the first signal from an initial state, referred to as the first value, through intermediate values, and ultimately to a final state, referred to as the second value.

[0045] The first value, in this context, is set to a level where the first semiconductor switch is either not conducting at all or is just beginning to conduct but has not yet reached its full conduction capacity. This is indicative of a high-resistance state within the first semiconductor switch, effectively limiting the flow of current from the power source to the load. This acts as a starting point that ensures the system begins the precharge cycle without introducing a sudden surge of current, thereby safeguarding the components from potential electrical stress. As the control circuit progressively adjusts the first signal from the first value, it modulates the conductivity of the first semiconductor switch through the range of values. This gradual modulation allows for a precise and controlled increase in the current flow. Eventually, the first signal reaches the second value, where the first semiconductor switch is fully turned on. This state represents a low-resistance path through the first semiconductor switch, allowing the current to flow freely from the power source to the load. The transition to this state marks the completion of the pre-charge cycle, preparing the system for normal operation with the full connection established between the power source and the load.

[0046] Herein, the first value, the second value, the intermediate values in the range of values, and the first period of time are chosen to facilitate a linear increase in conductivity, mirroring the behavior of an adjustable resistor, thereby allowing the system to finely tune the current flow according to the specific requirements of the pre-charge cycle. In an nonlimiting example, an input voltage from the power source may be 500 volts. In such case, an input voltage to the first semiconductor switch, as controlled via the first driver, starts from zero volts and increases to 15 volts within 100 milliseconds (ms) of time. It may be appreciated that, in some alternate examples, this can be achieved passively by using R / C filter, or the like. In the present example, the output to the load, from the first semiconductor switch, is charged up to 500 volts within that 100 ms time. This limits the output current from the first semiconductor switch to the required level. In particular, the load depends on the equipment connected to output of the first semiconductor switch. It can be resistive, capacitance, inductive, or any combination of those. This way the loading current can be limited to less than 2 Ampere, which is typical in electric vehicle charging specifications. It may be understood that in this case, the load consists mainly of the charging cable capacitance.

[0047] In an embodiment, the control circuit is configured to prevent the initialization of the pre-charge cycle, or to stop the pre-charge cycle, when it is detected that the power source has been disconnected from the load, by controlling the second driver to output the second signal to turn off the second semiconductor switch, or by preventing the second semiconductor switch from being turned on. Herein, the control circuit is utilized, within the system, not only in initiating and managing the precharge cycle but also in appropriately responding to changes in the connection status between the power source and the load. The control circuit may either prevent the initiation of the pre-charge cycle or halt an ongoing pre-charge cycle under specific conditions, particularly when it is detected that the power source has been disconnected from the load. This is done as when the power source is disconnected, continuing or initiating the pre-charge cycle could lead to potential damage to electrical components.

[0048] For this purpose, the control circuit utilizes the second driver in conjunction with the second semiconductor switch. When the disconnection of the power source from the load is detected, the control circuit issues a command to the second driver, instructing it to generate and output the second signal to the second semiconductor switch, to transition the second semiconductor switch from its current state to an off state, effectively stopping the flow of current through the system. Alternatively, the control circuit may use prevention by ensuring that the second semiconductor switch does not turn on at all upon detecting the disconnection of the power source. This approach of either stopping the pre-charge cycle by turning off the second semiconductor switch or preventing initiation of the pre-charge cycle helps in maintaining operational safety and reliability of the system.

[0049] In an embodiment, the control circuit is configured to control the first semiconductor switch to operate it in a fully turned on state. In operation of the system, particularly following the completion of the pre-charge cycle, this facilitate the full flow of current from the power source to the load. It may be understood that operating the first semiconductor switch in the fully turned on state minimizes the resistance offered by the first semiconductor switch to the current flow. Such fully turned on state ensures that, once the voltages across the power source and load are equalized and the risks associated with inrush currents are mitigated, the system can transition to its normal operational mode, allowing the maximum designed current flow to the load, as may be required for its functioning. For this purpose, the control circuit adjusts the first signal, which it outputs to the first driver, to control the first semiconductor switch. The adjustment process involves ramping up the first signal to a level that ensures the third terminal (gate) of the first semiconductor switch is sufficiently biased, causing the first semiconductor switch to enter its conductive, or 'on', state. Such ability to control the first semiconductor switch to operate in the fully turned on state allows for a smooth transition between controlled pre-charge conditions and full operational capacity, ensuring that the system can respond dynamically to the varying requirements of the electrical load while maintaining safety and reliability.

[0050] In an embodiment, the control circuit is configured to control flow of current through the second semiconductor switch in the linear region. The linear region, in the context of semiconductor switches like FETs, describes a state where the semiconductor switch operates similar to a variable resistor. In the linear region state, the relationship between the gate-to-source voltage and the drain current is generally linear, allowing for the precise control of the current through the semiconductor switch by varying the gate voltage. This allows the system to provide a controlled ramp-up of current. This control is required, as it allows the system to manage current flow, especially during critical phases such as the pre-charge cycle or transitional states where current regulation is important.

[0051] For this purpose, the control circuit actively modulates the second signal output to the second driver, which in turn adjusts the input voltage of the second semiconductor switch. The control circuit calibrates the second signal such that it corresponds to the input voltage levels that maintain the second semiconductor switch within the linear region. The ability to control the second semiconductor switch in the linear region is particularly beneficial in scenarios where the system requires a gradual modulation of current across both rails therein. This capability ensures that the system can maintain stability and protect sensitive components from potential damage due to sudden current spikes.

[0052] In an embodiment, the control circuit is configured to:

[0053] - receive a current value and a voltage value, and compute, based on the received values, a control chart; and

[0054] - adjust the first signal from the first value to the second value based on the computed control chart.

[0055] Herein, the control circuit process electrical parameters, specifically the current value and the voltage value. It may be appreciated that the required data (the maximum current to which value the current need to be limited and the DC voltage) is received, e.g., from EV (connected to the load). Upon receiving these values, which are indicative of the operational conditions at any given moment, the control circuit derives a control chart. The control chart is a representation of relationship between the current and voltage parameters and the optimal operational trajectory for the semiconductor switches, particularly the first semiconductor switch. The computed control chart is utilized for modulating the first signal. The first signal, which is used for controlling the conductive state of the first semiconductor switch, is adjusted from the first value to the second value based on the computed control chart. Herein, as discussed, the first value is characterized by a condition where the first semiconductor switch is either in a non-conductive state or is not fully conductive, ensuring a controlled start to the modulation process without inrush currents. Conversely, the second value corresponds to a fully conductive state of the first semiconductor switch, facilitating the complete flow of current to the load, thereby completing the pre-charge cycle. By calibrating the first signal in alignment with real-time current and voltage values, the control circuit ensures that the system can adaptively manage the current flow through the first semiconductor switch, which, in turn, enhances the efficiency and reliability of the pre- charge process and contributes to the overall stability and safety of the system.

[0056] In an embodiment, the control circuit is configured to adjust, during the first period of time, at least one of:

[0057] - the first signal to the second signal by pre-determined steps; and

[0058] - the first signal to the second signal based on control curve.

[0059] Herein, the control circuit provides a level of control over the modulation of the first signal, which is important for the operation of the first semiconductor switch. This control is exercised during a defined duration, referred to as the first period of time, for the transition of the system through various operational states, such as the initiation and completion of the pre-charge cycle.

[0060] In a first implementation, the control circuit may adjust the first signal towards the second signal through a series of pre-determined steps. This involves incrementing or decrementing the signal in fixed magnitudes at set intervals within the first period of time. This stepwise approach allows for a structured modulation of conductivity of the semiconductor switch, facilitating a gradual increase or decrease in current flow. The predetermined steps are established based on operational parameters of the system and the specific requirements of the load, ensuring that the transition from the first value to the second value of the first signal is executed in a manner that optimizes performance of the system and safeguards against potential electrical stresses.

[0061] In a second implementation, the control circuit may adjust the first signal towards the second signal based on the control curve. This approach employs a more dynamic and responsive strategy, where the modulation of the first signal is based on the control curve that represents the desired relationship between the signal and time (or another operational parameter). Such control curve may be derived from characteristics of the system, operational conditions, and the specific requirements of the pre-charge cycle or other controlled current modulation phases. By adjusting the first signal based on the control curve, the control circuit ensures precise control over operation of the semiconductor switch, allowing for an optimized current flow that aligns closely with the realtime needs of the system.

[0062] The present disclosure also relates to the method as described above. Various embodiments and variants disclosed above, with respect to the aforementioned system, apply mutatis mutandis to the method.

[0063] In an embodiment, the method further comprises preventing the initialization of the pre-charge cycle or stopping the pre-charge cycle, by the control circuit, when it is detected that the power source has been disconnected from the load, by controlling the second driver to output a second signal to turn off the second semiconductor switch, or by preventing the second semiconductor switch from being turned on.

[0064] In an embodiment, the method further comprises:

[0065] - receiving, by the control circuit, a current value and a voltage value, and computing, based on the received values, a control chart; and

[0066] - adjusting, by the control circuit, the first signal from the first value, through a range of values, to the second value based on the computed control chart.

[0067] In an embodiment, the method further comprises controlling, by the control circuit, the first semiconductor switch to operate it in a fully turned on state.

[0068] In an embodiment, the method further comprises controlling, by the control circuit, flow of current through the second semiconductor switch in a linear region.

[0069] In an embodiment, the method further comprises:

[0070] - receiving, by the control circuit, a current value and a voltage value, and computing, based on the received values, a control chart; and - adjusting, by the control circuit, the first signal from the first value, through a range of values, to the second value based on the computed control chart.

[0071] In an embodiment, the method further comprises adjusting, by the control circuit, the first signal to the second signal by pre-determined steps.

[0072] The system and the method of the present disclosure by replacing mechanical relays and resistors with semiconductor switches, significantly reduces the physical size and manufacturing cost of the precharge system. The ability to control the semiconductor switches with precision provides flexibility in managing inrush currents for various applications. This precise control also increases reliability of such system, as it reduces the likelihood of component failure due to excessive current. Furthermore, unlike mechanical systems that may require additional cooling solutions, the semiconductor-based approach of the present disclosure minimizes thermal issues, further enhancing overall efficiency and longevity of such systems.

[0073] DETAILED DESCRIPTION OF THE DRAWINGS

[0074] Referring to FIG. 1, illustrated is a schematic block diagram of system 100 for controlling current, configured to be arranged between a power source 110 and a load 120, in accordance with embodiments of the present disclosure. The system 100 includes a first semiconductor switch 130 and a second semiconductor switch 140. A first terminal 131 of the first semiconductor switch 130 is connected to a first rail of the power source 110 and a second terminal 132 of the first semiconductor switch 130 is connected to a first rail of the load 120, and a first terminal 141 of the second semiconductor switch 140 is connected to a second rail of the power source 110 and a second terminal 142 of the second semiconductor switch 140 is connected to a second rail of the load 120. The system 100 also includes a first driver 103 and a second driver 104. An output of the first driver 103 is connected to a third terminal 133 of the first semiconductor switch 130, and an output of the second driver 104 is connected to a third terminal 143 of the second semiconductor switch 140. The system 100 further includes a control circuit 105 connected to an input of the first driver 102 and an input of the second driver 104.

[0075] Referring to FIG. 2, illustrated is a flowchart listing steps involved in a method 200 for controlling current by the system 100, in accordance with embodiments of the present disclosure. At step 210, the method 200 includes detecting, by a control circuit 105, whether a power source 110 has been connected to / disconnected from a load 120. At step 220, the method 200 includes initiating a pre-charge cycle, by the control circuit 105, when it is detected that the power source 110 has been connected to the load 120, by controlling a second driver 104 to output a second signal to turn on a second semiconductor switch 140. At step 230, the method 200 includes, upon initiating the pre-charge cycle, controlling the first driver 103, by the control circuit 105, to output a first signal to the first semiconductor switch 130 to operate it in a linear region, wherein the first signal has initially a first value. At step 240, the method 200 includes activating the pre-charge cycle, and upon activating of the precharge cycle, controlling, by the control circuit 105, flow of current through the first semiconductor switch 130 in the linear region by adjusting the first signal from the first value to a second value as a function of time, wherein the second value corresponds to a value in which the first semiconductor switch 130 has been fully turned on. The aforementioned steps 210-240 are only illustrative, and other alternatives can also be provided where one or more steps are added, one or more steps are removed, or one or more steps are provided in a different sequence without departing from the scope of the claims herein. Referring to FIG. 3, illustrated is a control curve 300 for timing of precharge, when a connection element is fully in conductive state, in accordance with embodiments of the present disclosure. As shown in the control curve 300, upon the activation of the pre-charge cycle, marked by position 1 (Pos.l) as the commencement point, the first semiconductor switch begins its transition into a conductive state, initially operating within the linear region. This transition is facilitated by a gradual increase in the input voltage provided by the first driver to the first semiconductor switch (as represented by reference numeral 302), representing the increase in the first signal from the first value towards the second value. In an example, the input voltage from the power source is 500 volts. In such case, the input voltage to the first semiconductor switch from the first driver starts from zero volts and increases to 15 volts within 100 ms time. The controlled increment in the gate voltage ensures that the output voltage across the first semiconductor switch rises (as represented by reference numeral 304) at a deliberate pace, allowing for a measured escalation in current flow towards the load. As the pre-charge cycle progresses (as represented by reference numeral 308), the first semiconductor switch is guided through a series of incremental steps, each corresponding to a slight elevation in the first signal. This stepwise enhancement continues until the predefined conclusion of the first period of time, typically spanning a duration from milliseconds to seconds, as depicted by 100 ms timing in the control curve 300. By the end of this interval, denoted as position 2 (pos.2), the first semiconductor switch reaches a state of full conductivity (as represented by reference numeral 306), effectively transitioning from its initial linear operational mode to act as a fully closed switch. In the present example, the output to the load is charged up to 500 V within that 100 ms time. This state is achieved when the first signal has been elevated through the pre-determined steps to the second value, indicative of the gate voltage level required for full turn-on of the first semiconductor switch. Referring to FIG. 4, illustrated is a graph 400 for determining transfer characteristics (specifically, linear conductivity behavior) of a semiconductor switch (such as, the first and second semiconductor switches), in accordance with embodiments of the present disclosure. In the present example implantation of FIG. 4, the semiconductor switch is a silicon carbide field-effect transistor (SiC-FET). These transfer characteristics are utilized for understanding the behavior of the semiconductor switches under various junction temperatures and how they influence the pre-charge cycle within the system for controlling current. The graph 400 exhibits the relationship between the gate-to- source voltage (I / GS) and the drain-source current (ID) for the SiC-FET at different junction temperatures (7)). The three distinct curves represent the SiC-FET's performance at temperatures of -40 °C, 25 °C, and 175 °C. Notably, the transfer characteristics shift with temperature changes, affecting the gate voltage required to induce conductivity in the semiconductor switch. From the graph 400, it is observable that the SiC- FET begins to conduct, i.e., allows current to flow from the drain to the source when the gate-to-source voltage reaches approximately 4 volts at a standard room temperature of 25°C. This voltage level represents the threshold at which the semiconductor switch starts to transition from a non-conductive to a conductive state, entering the linear region of operation. This region is where the SiC-FET acts similarly to an adjustable resistor, for the controlled ramp-up of current during the pre-charge cycle. For a design scenario where the system aims to handle a continuous drain current of 20 A in the fully conductive state, the gate- to-source voltage needs to exceed about 9 volts at room temperature. This information is derived from the manufacturer's datasheet and is used by the control circuit for determining the appropriate first value of the gate voltage when initiating the pre-charge cycle.

[0076] The graph 400 serves as a reference for designing the slow turn-on behavior of the semiconductor switches to achieve the desired pre-charge characteristics. The graph 400 provides designers with the necessary data to calculate the timing for the input voltage rise time, considering factors such as transconductance, input capacitance, drain-source on- resistance, and continuous drain current capability of the switches. By utilizing this information, the control circuit can adjust the first signal to the first driver, ensuring that the rising time of the input voltage aligns with the pre-determined steps or control curve to achieve proper timing for the pre-charge cycle.

Claims

CLAIMS1. A system (100) for controlling current, configured to be arranged between a power source (110) and a load (120), the system (100) comprising:- a first semiconductor switch (130) and a second semiconductor switch (140), wherein a first terminal (131) of the first semiconductor switch (130) is connected to a first rail of the power source (110) and a second terminal (132) of the first semiconductor switch (130) is connected to a first rail of the load (120), and a first terminal (141) of the second semiconductor switch (140) is connected to a second rail of the power source (110) and a second terminal (142) of the second semiconductor switch (140) is connected to a second rail of the load (120);- a first driver (103) and a second driver (104), wherein an output of the first driver (103) is connected to a third terminal (133) of the first semiconductor switch (130), and an output of the second driver (104) is connected to a third terminal (143) of the second semiconductor switch (140); and- a control circuit (105) connected to an input of the first driver (102) and an input of the second driver (104), wherein the control circuit (105) is configured to:- detect whether the power source (110) has been connected to, or disconnected from, the load (120), and when it is detected that the power source (110) has been connected to the load (120), initiate a pre-charge cycle by controlling the second driver (104) to output a second signal to turn on the second semiconductor switch (140), to operate it in a saturation region;- upon initiating, control the first driver (103) to output a first signal to the first semiconductor switch (130) to operate it in a linear region; and- control flow of current through the first semiconductor switch (130) in the linear region by adjusting, during a first period of time, the first signal from a first value, through a range of values, to a second value, wherein the first value corresponds to a value in which the first semiconductor switch (130) is not conducting, or it has not been fully turned on, and the second value corresponds to a value in which the first semiconductor switch (130) has been fully turned on.

2. A system (100) according to claim 1, wherein, the control circuit (105) is configured to:- prevent the initialization of the pre-charge cycle, or to stop the pre-charge cycle, when it is detected that the power source (110) has been disconnected from the load (120), by controlling the second driver(104) to output the second signal to turn off the second semiconductor switch (140), or by preventing the second semiconductor switch (140) from being turned on.

3. A system (100) according to claim 1 or 2, wherein the control circuit(105) is configured to:- control the first semiconductor switch (130) to operate it in a fully turned on state.

4. A system (100) according to any of the previous claims, wherein the control circuit (105) is configured to:- control flow of current through the second semiconductor switch (140) in the linear region.

5. A system (100) according to any of the previous claims, wherein the control circuit (105) is configured to:- receive a current value and a voltage value, and compute, based on the received values, a control chart; and- adjust the first signal from the first value to the second value based on the computed control chart.

6. A system (100) according to any of the previous claims, wherein the control circuit (105) is configured to adjust, during the first period of time, at least one of:- the first signal to the second signal by pre-determined steps; and- the first signal to the second signal based on control curve.

7. A system (100) according to any of the previous claims, wherein the first rail is a positive rail and the second rail is a negative rail.

8. A system (100) according to any of the previous claims, wherein each of the first semiconductor switch (130) and second semiconductor switch (140) is at least one of: a metal-oxide-semiconductor field-effect- transistor, a junction field-effect-transistor, an insulated-gate bipolar transistor, a bipolar junction transistor.

9. A system (100) according to any of the previous claims, wherein the power source (110) is a direct-current power supply.

10. A system (100) according to any of the previous claims, wherein the load (120) comprises a capacitor.

11. A method (200) for controlling current by a system (100) according to any of the previous claims 1-10, the method (200) comprising:- detecting, by a control circuit (105), whether a power source (110) has been connected to / disconnected from a load (120);- initiating a pre-charge cycle, by the control circuit (105), when it is detected that the power source (110) has been connected to the load (120), by controlling a second driver (104) to output a second signal to turn on a second semiconductor switch (140);- upon initiating the pre-charge cycle, controlling the first driver (103), by the control circuit (105), to output a first signal to the firstsemiconductor switch (130) to operate it in a linear region, wherein the first signal has initially a first value; and- activating the pre-charge cycle, and upon activating of the precharge cycle, controlling, by the control circuit (105), flow of current through the first semiconductor switch (130) in the linear region by adjusting the first signal from the first value to a second value as a function of time, wherein the second value corresponds to a value in which the first semiconductor switch (130) has been fully turned on.

12. A method (200) according to claim 11, further comprising:- preventing the initialization of the pre-charge cycle or stopping the pre-charge cycle, by the control circuit (105), when it is detected that the power source (110) has been disconnected from the load (120), by controlling the second driver (104) to output a second signal to turn off the second semiconductor switch (140), or by preventing the second semiconductor switch (140) from being turned on.

13. A method (200) according to claim 11 or 12, further comprising:- receiving, by the control circuit (105), a current value and a voltage value, and computing, based on the received values, a control chart; and- adjusting, by the control circuit (105), the first signal from the first value, through a range of values, to the second value based on the computed control chart.

14. A method (200) according to any of claims 11-13, further comprising:- controlling, by the control circuit (105), the first semiconductor switch (130) to operate it in a fully turned on state.

15. A method (200) according to any of claims 11-14, further comprising:- controlling, by the control circuit (105), flow of current through the second semiconductor switch (140) in a linear region.

16. A method (200) according to any of claims 11-15, further comprising: - receiving, by the control circuit (105), a current value and a voltage value, and computing, based on the received values, a control chart; and- adjusting, by the control circuit (105), the first signal from the first value to the second as a function of time based on the computed control chart.

17. A method (200) according to any of claims 11-16, further comprising:- adjusting, by the control circuit (105), the first signal to the second signal by pre-determined steps.

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