Intelligent electronic switch

Abstract

The invention relates to an intelligent electronic switch. An electronic device is described herein that is used as an electronic fuse (smart fuse). The apparatus includes an electronic switch having a load current path coupled between an output node and a power supply node and configured to connect or disconnect the output node from the power supply node in accordance with a control signal. The apparatus also includes a control circuit configured to generate a control signal based on the input signal, a current sensing circuit configured to provide a current sensing signal, and a monitoring circuit configured to generate an overcurrent signal based on the current sensing signal. The overcurrent signal indicates whether to disconnect the output node from the power supply node. The control circuit is configured to operate in a normal mode, an idle mode, and a diagnostic mode. The control circuit is configured to change between a normal mode and an idle mode based on an idle mode condition. The control circuit is further configured to change between an idle mode and a diagnostic mode based on the diagnostic enable signal.

Description

Field of the technology

[0001] The present disclosure relates to the field of intelligent semiconductor switches. Background art

[0002] Almost every electrical device (e.g., in the electrical subsystems of automobiles, houses, industrial equipment, large devices) includes one or more fuses to provide overcurrent protection. A standard fuse includes a metal wire that provides a low-ohm current path when the current passing through the fuse is below the nominal current. However, when the current passing through the fuse exceeds the nominal current by a specific time, the metal wire is designed to heat up and melt or evaporate. Once triggered, the fuse must be replaced with a new one.

[0003] Today, conventional fuses are increasingly being replaced by circuit breakers. A circuit breaker is an automatically operated electrical switch designed to protect a circuit from damage caused by overcurrent, overload, or short circuit. A circuit breaker may include an electromechanical relay that is triggered to disconnect the protected circuit from the power supply when an overcurrent (i.e., a current exceeding the nominal current) is detected. In many applications (e.g., in the on-vehicle power supply of an automobile), an electronic switch (such as a MOS transistor, IGBT, etc.) can be used to implement the circuit breaker, and the electronic switch is configured to disconnect the circuit to be protected from the power supply in the case of overcurrent. Such an electronic circuit breaker can also be referred to as an electronic fuse (also known as an e-fuse or intelligent fuse). In addition to being used as a circuit breaker, an electronic fuse can also be used to regularly turn on and off a load (e.g., for pulse-width modulation operation). Generally, a so-called driver circuit or a simple driver (a gate driver in the case of a MOS transistor) is used to control the switching state (on / off) of an electronic switch such as a MOS transistor.

[0004] However, at least in some electronic fuses, ordinary driver circuits may be insufficient in terms of fault tolerance and functional safety, which may be a problem, especially in automotive applications where standards regarding functional safety (such as ISO 26262) must be complied with. In fact, an electronic fuse requires more than just replacing a traditional fuse with an electronic switch. The robust implementation of an electronic fuse needs to face various challenges. In addition, the current consumption of the electronic fuse itself may be a problem. Especially in automotive applications (or other applications where the power supply depends on a battery), low power consumption of devices such as electronic fuses is a desired design goal. To reduce power consumption, an electronic fuse can be designed to operate in a special mode, in which several functions and circuits of the electronic fuse are inactive to reduce power consumption in certain situations (e.g., when the electronic switch in the electronic fuse circuit is on, but the load current is low). In this article, this operating mode is referred to as the "idle mode".

[0005] During the idle mode, the very limited functionality of the electronic fuse causes further problems because during the idle mode, certain diagnostic functions may be unavailable, and switching to normal operation (increased power consumption) and back to the idle mode may take a relatively long time. The objective set by the inventor for himself is to improve the existing concept of the electronic fuse regarding the above problems. Summary of the Invention

[0006] The above-mentioned objective is achieved by the electronic device of claim 1 and the method of claim 14. The dependent claims cover various embodiments and further developments. Accordingly, a circuit used as an electronic fuse is described herein.

[0007] One embodiment relates to an electronic device. The device includes an electronic switch having a load current path coupled between an output node and a power supply node and configured to connect or disconnect the output node from the power supply node according to a control signal. The device further includes a control circuit configured to generate the control signal based on an input signal, a current sensing circuit configured to provide a current sensing signal representing the load current through the electronic switch, and a monitoring circuit configured to generate an overcurrent signal based on the current sensing signal. The overcurrent signal indicates whether to disconnect the output node from the power supply node. The control circuit is configured to operate in a normal mode, an idle mode, and a diagnostic mode. The control circuit is configured to change between the normal mode and the idle mode based on an idle mode condition, wherein in the idle mode, at least the monitoring circuit and the current sensing circuit are inactive. The control circuit is further configured to change between the idle mode and the diagnostic mode based on a diagnostic enable signal, wherein in the diagnostic mode, the monitoring circuit remains inactive while the current sensing circuit is active.

[0008] Another embodiment relates to a method for operating an electronic device as an electronic fuse. The method includes: generating a control signal based on an input signal, and connecting / disconnecting an output node of the electronic device from a power supply node using an electronic switch according to the control signal. The method further includes: generating a current sensing signal representing the load current through the electronic switch using a current sensing circuit; monitoring the load current using a monitoring circuit and based on the current sensing signal; and generating an overcurrent signal based on the current sensing signal, wherein the overcurrent signal indicates whether to disconnect the output node from the power supply node. The electronic device is configured to operate in a normal mode, an idle mode, and a diagnostic mode, wherein the method includes: initiating a change between the normal mode and the idle mode based on an idle mode condition, wherein in the idle mode, at least the monitoring circuit and the current sensing circuit are inactive, and initiating a change between the idle mode and the diagnostic mode based on a diagnostic enable signal, wherein in the diagnostic mode, the monitoring circuit remains inactive while the current sensing circuit is active. Brief Description of the Drawings

[0009] The present invention can be better understood with reference to the following drawings and description. The components in the drawings are not necessarily drawn to scale; rather, the emphasis is on illustrating the principles of the present invention. In addition, in the drawings, like reference numerals designate corresponding parts. In the drawings:

[0010] Figure 1 An example of an electronic fuse circuit including an electronic switch and a control circuit configured to drive the electronic switch is schematically illustrated.

[0011] Figure 2 The application of the electronic fuse circuit is described in more detail, and in particular, the interoperability of the electronic fuse circuit with a controller circuit (such as, for example, a microcontroller).

[0012] Figure 3 A is a graph showing a set of characteristic curves (time - current) of a 0.35 mm 2 cable and different maximum cable temperatures.

[0013] Figure 3 B is a graph showing a set of characteristic curves (time - current) of the maximum cable temperature 25 Kelvin above the ambient temperature and different cable cross - sections.

[0014] Figure 4 An example of a monitoring circuit (intelligent fuse function) used in the Figure 1 example is illustrated.

[0015] Figure 5 An exemplary state diagram showing the control circuit included in the electronic fuse and different operating modes (states) of the electronic fuse is shown.

[0016] Figure 6 An example of a modification of the Figure 1 example is illustrated.

[0017] Figure 7 For a more detailed illustration of the timing diagram of the intelligent fuse function implemented by a circuit such as, for example, Figure 1 and Figure 6 is shown. Detailed Description

[0018] In the following detailed description, reference is made to the accompanying drawings. The drawings form a part of the specification and, for purposes of illustration, show examples of how embodiments can be used and implemented. It should be understood that the features of the various embodiments described herein can be combined with each other unless specifically stated otherwise.

[0019] Figure 1 An example including an electronic switch T L and a control circuit configured to drive the electronic switch T LExample of an electronic fuse circuit (intelligent switching device 1) of a control circuit. In this example, the electronic switch is an n-channel MOS (metal oxide semiconductor) field effect transistor (MOSFET). It should be understood that other types of transistors can be used instead of the n-channel MOSFET. In the depicted example, the electronic switch T L has a load current path (i.e., the drain-source current path in the case of a MOSFET) coupled between the output node OUT of the electronic fuse circuit and the power supply node VS. Thus, the electronic switch is configured to connect (and disconnect) the output node OUT from the power supply node VS according to the control signal S ON . The control signal S ON is a logic signal generated by the control circuit 11 based on the input signal S IN , and this input signal S IN can be regarded as an on / off command. The control signal S ON can assume a high level (S ON = 1) or a low level (S ON = 0), where the high level can indicate that the electronic switch T L will be turned on, and the low level can indicate that the electronic switch T L will be turned off. According to the actual implementation, the gate driver circuit 12 can be connected between the control logic 11 of the electronic switch T L and the control electrode (the gate electrode in the case of a MOSFET), where the gate driver circuit 12 is configured to generate, for example, a suitable gate-source voltage V ON (or gate current i GS ) based on the logic signal S G for turning on and off the MOSFET T L . Various suitable implementations of the gate driver circuit are known and thus will not be discussed further herein.

[0020] The electronic fuse circuit (intelligent switching device 1) further includes a current sensing circuit 13, which is configured to provide a current sensing signal CS representing the load current i L passing through the electronic switch T L . Various different types of current sensing circuits are known and thus will not be discussed in detail herein. In one example, the current sensing circuit includes a so-called sensing transistor, which operates at the same operating point as the MOSFET T L and thus provides a sensing current i L proportional to the load current i CS . In one example, multiple transistor cells (cell array) are used to implement the MOSFET TL , where the transistor cells of the cell array are used to implement the sense transistor. Then, the ratio i CS / i L is approximately equal to the ratio of the transistor cells of the sense transistor and the load transistor T L . In some embodiments, the current sense signal CS may be a digital signal. In this case, the current sense circuit 13 performs analog-to-digital conversion.

[0021] The actual fuse function is implemented by the monitoring circuit 14, which is labeled as "intelligent fuse" in Figure 1 . The monitoring circuit 13 determines an overcurrent signal OC based on the current sense signal CS, and the overcurrent signal OC indicates whether to disconnect the output node OUT from the power supply node VS (by turning off (turning on) the electronic switch T L ). The overcurrent signal OC can be provided to the control logic 11, which is configured to: when the overcurrent signal OC indicates that the electronic switch T L is turned off, set the logic signal S ON to a low level.

[0022] In one example, the monitoring circuit is configured to generate an overcurrent signal OC based on the current sense signal CS and at least one wire parameter, and the at least one wire parameter characterizes the wire / cable connected between the output node OUT and the electrical load Z LOAD during operation. The at least one wire parameter may include the wire cross-sectional area A (in mm 2 ) and the temperature threshold dT R (in K), and the temperature threshold dT R represents the maximum allowable temperature difference between the ambient temperature and the cable temperature. The wire diameter (or any other parameter representing the wire size) can be used instead of the cross-sectional area. In this embodiment, the monitoring circuit 14 can be configured to estimate the temperature difference dT between the cable temperature and the ambient temperature based on the current sense signal CS and the mentioned (multiple) wire parameters. If the estimated temperature dT reaches or exceeds the temperature threshold dT R , then the monitoring circuit 14 can issue an overcurrent by setting the overcurrent signal OC to a high level (OC = 1). Various suitable implementations of the monitoring circuit 14 are known. An example is described in the published US10,965,120B2.

[0023] In Figure 1 example, the input signal S IN is a logic signal received from an external controller at the input pin IN (see also Figure 2 ). In other embodiments, the input signal S can be received via a digital communication interfaceIN , a digital communication interface such as, for example, a Serial Peripheral Interface (SPI). In one embodiment, an input signal S can be generated (e.g., by the communication interface) based on a command received via a bus line connected to the digital communication interface IN . In the case of SPI, the bus line can be a so-called MOSI (Master Output / Slave Input) line. In Figure 1 the example of, another logic signal S is received from an external controller at another input pin DEN DEN . The signal S DEN is also referred to as a diagnostic enable signal. The electronic fuse circuit further includes a diagnostic circuit 15 that is activated and deactivated according to the diagnostic enable signal S DEN . In Figure 1 the example of, the diagnostic circuit 15 receives the diagnostic enable signal S DEN . Alternatively, the diagnostic circuit 15 can be activated and deactivated by the control logic 11 according to the logic level of the diagnostic enable signal S DEN .

[0024] The diagnostic circuit 15 is configured to: when the diagnostic enable signal S DEN causes the activation of the diagnostic circuit 15, output a signal i (diagnostic output signal) based on the current sensing signal CS S . In the depicted example, the diagnostic output signal i S is output at a chip pin IS, and the chip pin IS is connected to a reference potential (e.g., ground) via a resistor R IS . Thus, the diagnostic output signal i S is consumed via the resistor R IS , thereby causing a voltage drop V IS across the resistor R IS = R IS ·i S . This voltage drop V IS can be sensed and evaluated, for example, by an external controller (see also Figure 2 ).

[0025] If the current sensing signal CS is a digital signal, then the diagnostic circuit 15 can include a digital-to-analog converter (DAC) having a current output, where the DAC generates the diagnostic output signal i based on the digital signal CS S . Note that the diagnostic circuit 15 can be configured to output not only load current information but also additional information. In some embodiments, the diagnostic output signal i S can include temperature information or indicate an error, etc. The diagnostic circuit 15 can select the information to be output (such as the signal i DEN ) depending on the signal S S , the signal S DENIt can be modulated in different ways. In another example, a diagnostic enable signal can be received via a digital communication link (such as an SPI bus). In this case, signal S DEN can be a digital signal indicating what type of information is output at pin IS. In some embodiments, the diagnostic output signal is not a current signal similar to Figure 1 but a digital signal transmitted to an external controller via a digital communication link (such as the MISO (Master Input / Slave Output) line in the case of SPI).

[0026] In Figure 1 's example, the electronic fuse circuit has a ground pin GND, which is connected (optionally via a low-ohm resistor) to the ground potential during operation. The current i consumed via the ground pin GND represents the current consumption of the electronic fuse itself, i.e., the total current consumption of the circuit components included in the electronic fuse circuit (represented as the intelligent switch 1 in Figure 1 ). During normal operation (normal mode), when all components such as the current sensing circuit 13 and the monitoring circuit 15 are active, the current i GND can be quite large, for example, in the range of milliamperes (for example, 20 mA for illustration). Even in a situation where the electrical load Z LOAD is inactive and the load current i L is very low or even zero, the intelligent switch device 1 cannot be simply turned off to reduce the current (current i GND ) consumption because when used as an electronic fuse, the intelligent switch usually has to be turned on to apply the power supply voltage to the load Z LOAD . In applications where multiple electronic fuses are used (such as in automotive applications), the total current consumption of all electronic fuses can easily add up to several hundred milliamperes or a larger value, which is unacceptably high, especially when the power supply is provided by a battery.

[0027] To reduce the power consumption of the intelligent switch (although it is turned on), a so-called idle mode has been introduced, in which many internal components of the intelligent switch are inactive to reduce the current consumption i GND . In the example described herein, when the intelligent switch operates in the idle mode, at least the monitoring circuit 14 and the current sensing circuit 13 are inactive. The operating mode is controlled by the control logic 11 (or a part thereof). Therefore, the control circuit 11 is configured to change from the operation in the normal mode to the idle mode (and vice versa) based on the idle mode condition. Although not explicitly shown in Figure 1 , the control logic 11 can be configured to activate and deactivate certain components of the intelligent switch when the mode changes. In Figure 1In the example, the evaluation circuit 16 detects whether the idle mode condition is satisfied and generates a corresponding logic signal IDL supplied to the control logic 11. That is, the signal IDL indicates whether the idle mode condition is satisfied.

[0028] In a simple example, the idle mode condition is i L <i IDLE , where i IDLE is the current threshold. That is, when the load current i L is lower than the threshold i IDLE , the idle mode condition is satisfied. In another example, the idle mode condition is i L <i IDLE &T J <T JMAX , where T J is the measured temperature of the transistor T L , and T JMAX is the corresponding temperature threshold. That is, when the load current i L is lower than the current threshold i IDLE and the junction temperature T of the transistor J is lower than the temperature threshold T JMAX , the idle mode condition is satisfied. In other embodiments, more than two criteria (using conjunction) may be combined to define the idle mode condition. In the depicted example, the estimated wire temperature dT (provided by the monitoring circuit 14) is also considered.

[0029] In the idle mode, when the transistor T L is turned on, the total power consumption i GND of the intelligent switching device 1 can be reduced to a few microamperes (e.g., 30 μA). However, the cost of this reduction is that most functions of the "intelligent functions" such as the monitoring circuit 14, the current sensing circuit 13, and the diagnostic circuit 15 are unavailable. In particular, in many applications, the unavailability of the diagnostic function is a problem. A straightforward approach is to temporarily switch from the idle mode to the normal mode when the diagnostic enable signal S DEN indicates a request to output diagnostic information (i.e., activate the diagnostic circuit). However, if the intelligent switch "wakes up" and changes from the idle mode to the normal mode, it must remain in the normal mode for a specific time (usually 100 ms or longer) before it can switch back to the idle mode. This delay time is required for various reasons. For example, when using an intelligent switch to drive a load Z LOAD with a PWM signal (e.g., the input signal S IN is modulated, and the transistor T L is turned on and off according to S IN(Periodically turned on and off), the permanent switching between the normal mode and the idle mode is avoided by the delay time. When changing from the idle mode to the normal mode, it also takes some time to restore the required register values in the monitoring circuit 14. Therefore, when diagnostic information is needed during the operation in the idle mode, in many applications, periodically temporarily switching to the normal mode is not an option because, since the intelligent switch must remain in the normal mode for a relatively long time before switching back to the idle mode, the average current consumption i GND will increase significantly, thus compromising the advantages of the idle mode.

[0030] To solve the problems discussed above, a new operation mode is introduced, which is referred to herein as the diagnostic mode. In the embodiments described herein, only the change from the idle mode to the diagnostic mode can be achieved. In one embodiment, the control circuit 11 is configured to change between the idle mode and the diagnostic mode based on the diagnostic enable signal S DEN wherein in the diagnostic mode, the current sensing circuit 13 is active (to enable the diagnostic output), while the monitoring circuit 14 remains inactive.

[0031] When changing from the idle mode to the diagnostic mode (and back to the idle mode), since the monitoring circuit 14 remains inactive, it is possible to temporarily switch to the diagnostic mode, where the time in the diagnostic mode can be very short (significantly shorter than the 100 ms required to switch to the normal mode and back to the idle mode). As a result, the brief and temporary switch to the diagnostic mode (for outputting diagnostic information) does not significantly increase the average value of the current consumption i of the intelligent switch device itself GND . The change between the idle mode and the diagnostic mode does not affect the (inactive) state of the monitoring circuit 14. The monitoring circuit 14 is only activated when changing back to the normal mode, where the activation of the monitoring circuit requires restoring the previous active state of the monitoring circuit 14, in particular restoring one or more internal register values of the monitoring circuit 14, which are lost when the monitoring circuit is deactivated.

[0032] Before discussing the function of the electronic fuse circuit (intelligent switch 1) in more detail, refer to Figure 2 the exemplary applications of the electronic fuse circuit are discussed, Figure 2 in particular showing the interoperability between the intelligent switch 1 and the controller circuit 2, and the controller circuit 2 can be, for example, an ordinary microcontroller ( Figure 2 marked as MCU in Figure 2 . The intelligent switch 1 can be implemented according to or similar to Figure 1 the example of

[0033] The microcontroller 2 is configured to generate signals S IN and S DEN, and output these signals at the digital output pins or so-called general-purpose input / output (GPIO) pins. The corresponding pins of the microcontroller are connected (e.g., via resistors) to the input pins IN and DEN of the intelligent switching device 1. The power supply pin VS is connected to a battery (e.g., connected to the so-called "terminal 30" ("permanent positive pole") providing the battery voltage V S , and the ground pin GND is connected to the ground potential. The output pin OUT is connected to the load Z LOAD (similar to the example of Figure 1 ). The diagnostic output IS is connected to the ground via a resistor R IS (similar to the example of Figure 1 ), and is also connected to the analog input of the microcontroller (e.g., via an RC filter). The microcontroller may include an analog-to-digital converter (ADC) configured to digitize the voltage V IS = R IS ·i S . In this way, the microcontroller can start the diagnostic output by outputting a diagnostic enable signal S DEN , and read the diagnostic information by digitizing the voltage V S proportional to the diagnostic current i IS . In the depicted example, the controller 2 is powered by a supply voltage V S different from the battery voltage V DD .

[0034] The controller 2 may include a processor having one or more processor cores configured to execute software instructions stored in the memory of the controller 2. Together with the peripheral circuits (such as ADC, memory, GPIO driver circuits, etc.) and appropriate software instructions, the controller is capable of providing the functions necessary to control the operation of the intelligent switch 1. It should be understood that the controller does not necessarily have to have a processor. In some embodiments, the controller may include one-time programmable or hardwired logic circuits, which together with the peripheral circuits are configured to provide substantially the same functions as the aforementioned processor. A combination of a processor and hardwired logic is also possible. Any hardware entity including a processor and / or other circuits configured to provide the functions described herein is considered a controller. Finally, note that the intelligent switch 1 may include more than one output channel to be able to connect more than one electrical load.

[0035] Before discussing in more detail the above-mentioned operating modes (normal mode, idle mode, diagnostic mode), the purpose and function of the monitoring circuit 14 are explained in more detail below. The monitoring circuit is one of the core functions of the electronic fuse circuit because it implements behavior similar to that of a conventional fuse.

[0036] As mentioned above, the line-connected load Z can be selectedLOAD and the intelligent switch 1 to bear the load Z LOAD The nominal current. The lifetime of the wire / cable depends on the wire temperature (among other factors). Figure 3 A and Figure 3 B are graphs including a set of characteristic curves, where each characteristic curve is associated with a specific combination of the maximum temperature difference dT (the maximum temperature above the ambient temperature) and the cable cross-sectional area A (e.g., the cross-sectional area in units of mm 2 Each characteristic curve represents the relationship between the load current and the maximum allowable time period during which the wire can carry the load current without exceeding the specified temperature difference dT. Figure 3 A includes characteristic curves for various temperature differences dT and a specific cross-sectional area of 0.35 mm 2 while Figure 3 B includes characteristic curves for a specific temperature difference dT of 25 K (Kelvin) and various cross-sectional areas. As can be seen from Figure 3 A and Figure 3 B, for a wire with a cross-sectional area of 0.35 mm 2 it can carry a current of approximately 9 A (amperes) for a practically infinite time without exceeding a temperature difference dT of 25 K above the ambient temperature. As can be seen from Figure 3 B, a wire with a cross-sectional area of 0.75 mm 2 can carry a current of 10 A (amperes) for approximately 100 seconds before reaching a temperature difference dT of 25 K above the ambient temperature. Generally, for a given cross-sectional area and a given temperature difference, the higher the load current, the shorter the allowable time period. Note that Figure 3 A and Figure 3 the characteristic curves shown in the graphs of A and B have a linearly decreasing branch in a double-logarithmic representation.

[0037] As can be seen from Figure 3 A and Figure 3 B, for a given current (see Figure 3 A, current i x ) and a specific cross-sectional area (e.g., 0.35 mm in the example of Figure 3 A 2 ), the temperature difference dT R (e.g., temperature values dT1, dT2, dT3, dT4, dT5, dT6) is associated with a given integration time t x (e.g., times t1, t2, t3, t4, t5, t6). Thus, for a specific wire cross-section, the current i L passing through the wire can be determined by xIntegrate over time to determine the temperature value dT (representing the temperature above the ambient temperature), and when the temperature value dT reaches a defined first reference temperature difference dT R (temperature threshold), the overcurrent signal OC can indicate the turn-off of the power transistor T L . The integration mentioned above can be effectively implemented using a digital filter, which can be included in the monitoring circuit 14 (see Figure 4 ). An exemplary simplified implementation of the monitoring circuit 14 is illustrated in Figure 4 .

[0038] Basically, Figure 4 the monitoring circuit is configured to determine the overcurrent signal OC based on the current sensing signal CS. As mentioned, the integration can be done in the digital filter 42 with integration characteristics. According to the depicted example, the current sensing signal CS, which can be a voltage proportional to the load current i L , is supplied to the input of the filter 45, which can be an (optional) analog low-pass filter to remove transients etc. with a relatively high frequency. The output of the filter 45 can be connected to the input of an analog-to-digital converter (ADC) 41, which is configured to digitize the filtered current sensing signal CS. If CS is already a digital signal, then the filter 45 and the ADC 41 are not needed. In this example, the ADC 41 can have logarithmic characteristics in order to interpret Figure 3 A and Figure 3 the logarithmic characteristic curves shown in B. Then, the (e.g., logarithmized) digital current sensing signal CS DIG is converted into the temperature signal dT by the digital filter 42. The resulting temperature value dT (representing the temperature difference above the ambient temperature) is then supplied to the digital comparator 43, which can be configured to: when the temperature value dT provided at the output of the digital filter 42 exceeds the reference temperature difference dT R (e.g., 25K) specified for a specific wire cross-section, set the overcurrent signal OC to a high level. Note that if the ADC 41 does not have logarithmic characteristics, then the digital current sensing signal CS DIG should be squared before being supplied to the filter 42. Additionally, when the current sensing circuit 13 has provided a digital current sensing signal, this signal is also squared before being fed to the filter 42. In this regard, reference is made to the published US20170294772A1, which describes the concept of such temperature calculation.

[0039] As mentioned, the digital filter 42 is configured to integrate the load current (represented by the digitized current sensing signal CS DIG(indicated) and the associated integration time (during which current passes through the wire) are converted into a temperature value dT. In this example, the filter characteristic 42 depends on the parameters characterizing the wire, such as the cross-sectional area of the wire, which carries the current and can be represented by a set of characteristic curves as shown in a diagram such as Figure 3 A (for an exemplary cross-sectional area of 0.35 mm 2 ). In a specific example, the characteristic curve (or related curve) can be stored as a look-up table, i.e., by storing multiple sampling points of the characteristic curve in a memory. Interpolation can be used, for example, to determine the value between two sampling points.

[0040] Conventional fuses are produced for specific triggering currents and specific triggering times (slow-blow fuses, medium-blow fuses, fast-blow fuses), where the triggering time corresponds to a reference temperature dT R and a specific combination of cross-sections, as explained above (see Figure 3 A and Figure 3 B). However, a configurable fuse is desired, which can be used for various different wire parameters, such as wire cross-section and maximum temperature value dT R (the maximum temperature above the ambient temperature). Therefore, the wire parameters can be configurable and set to the desired values for a specific application.

[0041] The filter 42 is a digital filter, and the filter output dT depends on the internal state of the filter, which is represented by register values. These state / register values are lost (reset) when the monitoring circuit 14 is deactivated when entering the idle mode. Therefore, the control logic 11 can be configured to store these register values when changing to the idle mode and restore these values when changing back to the normal mode. The restoration of the register values is triggered by the Figure 1 signal RES shown. The monitoring circuit (especially the digital filter 42) may require a clock signal for operation, and the clock signal is labeled as CLK in Figure 1 .

[0042] Figure 5 FIG. is an exemplary state diagram showing different operating modes (states) of the control logic 11, which determines the state of the entire electronic fuse circuit. In Figure 5 , the normal mode is labeled as S0, the idle mode is labeled as S1, and the diagnostic mode is labeled as S2. In all three modes S0 - S2, the electronic switch T L is on, and therefore the output pin OUT is approximately at the supply voltage V S . In the normal mode S0, the monitoring circuit 14 and the current sensing circuit 13 are active, and the current consumption i of the intelligent switch itself GNDin the range of milliamperes (e.g., 20 mA). In the idle mode S1, the monitoring circuit 14, the current sensing circuit 13, and other circuit devices are inactive to reduce the current consumption to a few microamperes (e.g., i GND = 30 μA). In the diagnostic mode S2, the monitoring circuit 14 remains inactive (and thus the register value is not restored), while the current sensing circuit 13 is active so that the diagnostic circuit 15 can output the load current information as diagnostic information.

[0043] In Figure 5 's example, the idle mode condition is a conjunction (i L < i IDLE ) & (V GS > V GSON ) & (T J < T JMAX ) & (dT < dT X ). That is, when (i) the load current i L is small enough (below the threshold i IDLE ) and (ii) the transistor T L is actually turned on (i.e., the gate-source voltage V GS is higher than the threshold voltage V GSON ) and (iii) the junction temperature T L of the power transistor T J is not too high (i.e., below the temperature threshold T JMAX ) and (iv) the estimated cable temperature dT (above the ambient temperature) does not exceed the threshold dT X , the idle mode condition is satisfied. If all the criteria are met, then the intelligent switching device changes from the normal mode S0 to the idle mode S1. If one of these criteria is not met, then the idle mode condition is no longer satisfied, and the intelligent switch changes back to the normal mode S0. Note that in the normal mode S0, the criterion i L < i IDLE can be evaluated by the circuit 16 (see Figure 1 ) using the current sensing signal CS. However, since this signal may not be available in the idle mode, when operating in the idle mode, the drain-source voltage V L on the transistor T DS (which is approximately proportional to i L , i.e., V DS = i L · R ON , where R ON indicates the on-resistance of the power transistor T L ) can be used to evaluate the criterion i L < i IDLE. Additionally, since the monitoring circuit 14 will not provide updated values, the temperature dT can be assumed to be constant in the idle mode. However, this assumption is valid because in the idle mode, the low load current (below i IDLE ) will not significantly heat the cable.

[0044] As Figure 5 seen, the diagnostic mode S2 can only be entered from the idle mode. In fact, the intelligent switch 1 is only in the diagnostic mode for a relatively short time to output diagnostic information, and then if the idle mode conditions are still met, it changes back to the idle mode. In this example, the high level of signal S DEN triggers the change to the diagnostic mode S2, while the low level of signal S DEN triggers the change back to the idle mode S1 (if the idle mode conditions are still met).

[0045] As explained above, the current sensing circuit 13 is active in the diagnostic mode S2 to enable the output of diagnostic information. However, the intelligent fuse function (monitoring circuit 14) remains inactive in the diagnostic mode S2 (see Figure 5 , "Intelligent fuse off"). Therefore, the time in the diagnostic mode (where i GND is higher than in the idle mode) may be very short and thus does not significantly increase the average current consumption.

[0046] Note that the operation in the diagnostic mode S2 is not a prerequisite for the output of diagnostic information. In the normal mode S0, in the same way as in the diagnostic mode, depending on the level of signal S DEN , the output of diagnostic information is also possible. However, in the diagnostic mode S2, the monitoring circuit 14 (intelligent fuse function) is inactive, which allows minimizing the time during which the current consumption i GND increases. That is, when the controller 2 (see Figure 2 ) polls the diagnostic information periodically during the idle mode, the intelligent switch will change to the diagnostic mode periodically for a relatively short time, but will not change to the normal mode as long as the idle mode conditions are met.

[0047] Figure 5 A fourth mode is also shown, which is optional and is called the sleep mode S3. When the input signal S IN indicates the active turn-off of the transistor T L , the intelligent switch will change to the sleep mode S3. When the input signal S IN signals to turn on the transistor T L again, the intelligent switch will always first change to the normal mode S0 and then, depending on the situation, change to the idle mode S0 if the idle mode conditions are met.

[0048] Figure 6 Describes Figure 1 modifications to the example of. In addition to the communication interface 17, Figure 6 the example of is the same as Figure 1 the example of, where the communication interface 17 is an SPI interface in the depicted example, which uses four bus lines MISO, MOSI, SCLK (serial clock), and CSN (chip select). The SPI bus is an industry standard and is therefore not described further here. Of course, other serial communication systems can also be used instead of SPI. The communication interface 17 provides signals S IN and S DEN in response to receiving the corresponding commands via the SPI bus. In addition, diagnostic information is not output via dedicated pins (as in the case of the example of Figure 1 ). Instead, when a request command is received via the communication interface, the diagnostic information can be sent as digital information (data) via the SPI bus. It should be understood that in this example, signals S IN and S DEN can be represented by digital values stored in, for example, the registers of the communication interface. Regarding Figure 6 the remaining components of the circuit of, refer to Figure 1 the above description of.

[0049] Figure 7 The timing diagram of further illustrates the intelligent fuse function provided by the monitoring circuit 14 and the control logic 11. When the input signal S IN (see Figure 1 and Figure 6 ) changes to a high level (indicating that the electronic switch T L is turned on, see Figure 7 , times t0, t2, and t5), the control logic 11 generates a control signal S ON with a high level, which causes the gate driver 12 to charge the gate of the transistor T L . For example, the control signal S ON can be provided by the output of an SR (set / reset) latch included in the control circuit 11, where the rising edge of the input signal S IN sets the SR latch, and the falling edge of the input signal S IN resets the SR latch (see Figure 7 , reset due to the falling edge of S IN at time t1). To trigger the turn-off, the monitoring circuit 14 (intelligent fuse function) generates an overcurrent signal OC with a high level, where the rising edge of the overcurrent signal OC also triggers the reset of the SR latch and thus causes the control signal S ON to return to a low level (see Figure 7 , time t3). As discussed above, the overcurrent signal OC is based on the load current iL and the given current-time characteristic curve used by the monitoring circuit 14 (determined, for example, by one or more wire parameters such as wire cross-section). To turn on the transistor T again L , the SR latch is set again at the subsequent rising edge of the input signal SIN to generate a high-level control signal S ON (see Figure 7 , time t5), the external controller (see Figure 2 ) can output a low level as the input signal S IN ( Figure 7 , time t4). It should be understood that Figure 7 the switching scheme shown is merely an illustrative example, and different schemes can be used depending on the requirements of the actual application.

[0050] Now summarize the above embodiments. It should be understood that the following is not an exhaustive list of technical features, but an exemplary overview. One embodiment relates to an electronic device (such as a packaged semiconductor chip). Thus, the device includes an electronic switch (see, for example, Figure 1 or Figure 6 , transistor T L ), which has a load current path coupled between an output node and a power supply node (see, for example, Figure 1 and Figure 6 , chip pins OUT and VS) and is configured to connect or disconnect the output node from the power supply node according to a control signal. The device further includes a control circuit configured to generate a control signal based on an input signal (such as, for example, Figure 1 , the signal S received at chip pin IN IN ), a current sensing circuit configured to provide a current sensing signal representing the load current through the electronic switch, and a monitoring circuit configured to generate an overcurrent signal based on the current sensing signal. The monitoring circuit can implement an intelligent fuse function, and the overcurrent signal indicates whether to disconnect the output node from the power supply node. The control circuit (and thus the entire intelligent switch device) is configured to operate in a normal mode, an idle mode, and a diagnostic mode. The control circuit is configured to change between the normal mode and the idle mode based on idle mode conditions (such as, for example, Figure 1 and 6 , evaluation circuit 16), where in the idle mode, at least the monitoring circuit and the current sensing circuit are inactive. The control circuit is further configured to change between the idle mode and the diagnostic mode based on a diagnostic enable signal (see, for example, Figure 1 , the signal S received at chip pin DEN DEN ), where in the diagnostic mode, the monitoring circuit remains inactive while the current sensing circuit is active.

[0051] The control circuit (see Figure 1 and Figure 6 , control logic 11) causes / initiates the activation and deactivation of certain components / circuits of the device upon a mode change. The monitoring circuit is configured to generate an overcurrent signal based on a current sensing signal and at least one wire parameter, where the at least one wire parameter can characterize a wire connected between an output node and an electrical load during device operation. The at least one wire parameter can include, for example, wire cross-section and temperature threshold.

[0052] In one embodiment, the control circuit can be configured to change from a diagnostic mode to a normal mode when the idle mode condition is no longer met. The electronic device can include a diagnostic circuit (see, for example, Figure 1 or Figure 6 , diagnostic circuit 15), which is configured to output a signal based on the current sensing signal depending on the logic level of a diagnostic enable signal. In other embodiments, different information (other than current information) can be output as diagnostic information.

[0053] In one embodiment, the monitoring circuit can be configured to estimate a property of the wire, where the overcurrent signal depends on the estimated property. The estimated property of the wire can represent the temperature difference between the wire temperature and the ambient temperature (see Figure 3 and Figure 4 ). The estimated property can be stored in a register of the monitoring circuit, where the register value is lost / reset when changing to the idle mode since the monitoring circuit is inactive in the idle mode. In one embodiment, the control circuit can be configured to restore the register value of the register when changing to the normal mode.

[0054] Depending on the actual implementation, the idle mode condition can depend on one or more criteria. In one embodiment, if the load current is below a given current threshold (first criterion) and meets at least one of the following additional criteria: the electronic switch is on, the temperature of the electronic switch is below a given temperature threshold, then the idle mode condition is met. For a specific application, the relevant criteria can be fixed, i.e., if a preset criterion or combination of criteria is met, then the idle mode condition is met.

[0055] The control circuit can be configured to cause a transition from the normal mode to the idle mode based on the idle mode condition, but not cause the transition until a defined time period (e.g., 100 ms or longer) has elapsed while in the normal mode. In some embodiments, the control circuit can be configured to change from the normal mode to the idle mode when the idle mode condition has been met for a defined time period.

[0056] Another embodiment relates to a method for operating an electronic device as an electronic fuse. Thus, the method includes: generating a control signal based on an input signal, and using an electronic switch (see, for example, Figure 1 , Figure 6 and Figure 7 ) to connect / disconnect an output node of the electronic device from a power supply node according to the control signal. The method further includes: using a current sensing circuit to generate a current sensing signal representing a load current passing through the electronic switch (e.g., see Figure 1 and Figure 6 , current sensing circuit 13); using a monitoring circuit and monitoring the load current based on the current sensing signal (see, for example, Figure 1 and Figure 6 , monitoring circuit 14); and generating an overcurrent signal based on the current sensing signal, where the overcurrent signal indicates whether to disconnect the output node from the power supply node (also see the timing diagram of Figure 7 ). The electronic device is configured to operate in a normal mode, an idle mode, and a diagnostic mode (see Figure 5 , modes S0 - S2), where the method includes: initiating a change between the normal mode and the idle mode based on an idle mode condition (see, for example, Figure 1 and Figure 6 , evaluation circuit 16), where in the idle mode, at least the monitoring circuit and the current sensing circuit are deactivated; and initiating a change between the idle mode and the diagnostic mode based on a diagnostic enable signal, where in the diagnostic mode, the monitoring circuit remains inactive while the current sensing circuit is active.

[0057] Several embodiments have been described. Note that the technical features and elements described with respect to different embodiments can be combined to create additional embodiments. It should be understood that changes and / or modifications can be made to the examples described herein without departing from the spirit and scope of the appended claims. For example, it should be understood that depending on the actual implementation of the logic circuit, the logic levels can be inverted. That is, a high level in one embodiment can have the same meaning and purpose as a low level in another embodiment, and vice versa. In particular, with respect to the various functions performed by the above-mentioned components or structures (units, circuit components, devices, circuits, systems, etc.), the terms used to describe such components (including references to "means") are intended to correspond to (unless otherwise specified) any component or structure that performs the specified / intended function of the component (e.g., functionally equivalent), even if it is not structurally equivalent to the described structure, which performs the functions in the exemplary implementations of the present invention described herein.

Claims

1. An electronic device, comprising: Electronic switch (T L ), having a load current path coupled between an output node (OUT) and a power supply node (VS), and the electronic switch (T L ) is configured to connect or disconnect the output node (OUT) from the power supply node (VS) according to a control signal (S ON ); Control circuit (11), configured to generate the control signal (S IN ) based on the input signal (S ON ); A current sensing circuit (13), configured to provide a current sensing signal (CS) representative of a load current (i L ) flowing through the electronic switch (T L ); and a monitoring circuit (14) configured to receive the current sensing signal (CS) and generate an overcurrent signal (OC) based on the current sensing signal (CS), the overcurrent signal (OC) indicating whether to disconnect the output node (OUT) from the power supply node (VS); and wherein the control circuit (11) is configured to operate in a normal mode (S0), an idle mode (S1), and a diagnostic mode (S2), wherein the control circuit (11) is configured to change between the normal mode and the idle mode based on an idle mode condition (IDL), wherein in the idle mode, at least the monitoring circuit (14) and the current sensing circuit (13) are inactive; and wherein the control circuit (11) is configured to change between an idle mode and a diagnostic mode based on a diagnostic enable signal (S DEN ), wherein in the diagnostic mode, the monitoring circuit (14) remains inactive while the current sensing circuit (13) is active.

2. The device according to claim 1, wherein the monitoring circuit (14) is configured to determine an overcurrent signal (OC) based on the current sensing signal (CS) and at least one wire parameter (dT R , A).

3. The device according to claim 2, wherein the wire parameters characterize a wire connected between the output node (OUT) and an electrical load (Z LOAD ) during operation of the device.

4. The device according to any one of claims 1 to 3, wherein the control circuit (11) is configured to change from the diagnostic mode to the normal mode when the idle mode condition (IDL) is no longer satisfied.

5. The device according to any one of claims 1 to 4, further comprising: Diagnostic circuit (15), configured to output a signal (i DEN ) based on the current sense signal (CS) depending on the logic level of the diagnostic enable signal (S S ).

6. The device according to any one of claims 1 to 5, wherein the monitoring circuit (14) is configured to estimate an attribute of the wire, and wherein the overcurrent signal (OC) depends on the estimated attribute.

7. The device according to any one of claims 1 to 5, wherein the control circuit (11) is configured to restore a register value of a register of the monitoring circuit (14) when changing to the normal mode, the register value representing the estimated attribute of the wire.

8. The device according to claim 7, wherein the register value is reset when the monitoring circuit (14) becomes inactive due to a change to the idle mode.

9. The device according to any one of claims 6 to 8, wherein the estimated attribute of the wire represents a temperature difference (dT) between the wire temperature and the ambient temperature.

10. The device according to any one of claims 1 to 9, wherein the idle mode condition (IDL) is satisfied if at least the following criteria are met: the load current (i L ) is below a given current threshold (i IDLE ), the electronic switch is turned on, and the temperature (T L ) of the electronic switch (T J ) is below a given temperature threshold (T JMAX ).

11. The device according to claim 10, wherein the idle mode condition (IDL) is satisfied if a combination of preset criteria is met.

12. The device according to any one of claims 1 to 11, wherein the control circuit (11) is configured to change from the normal mode to the idle mode based on the idle mode condition (IDL), but not to change until a defined time period has elapsed while remaining in the normal mode.

13. The device according to any one of claims 1 to 11, wherein the control circuit (11) is configured to change from the normal mode to the idle mode when the idle mode condition (IDL) has been satisfied for a defined time period.

14. A method, comprising: Generate a control signal (S IN ) based on the input signal (S ON ); Use an electronic switch (T L ) to connect and disconnect an output node (OUT) of an electronic device from a power supply node (VS) according to the control signal (S ON ); A current sensing signal (CS) representing a load current (i L ) flowing through the electronic switch (T L ) is generated by a current sensing circuit (13); By monitoring the circuit (14) and monitoring the load current (i based on the current sensing signal (CS) L ), and generating an overcurrent signal (OC) based on the current sensing signal (CS), the overcurrent signal (OC) indicating whether to disconnect the output node (OUT) from the power supply node (VS); and wherein the electronic device is configured to operate in a normal mode (S0), an idle mode (S1), and a diagnostic mode (S2), A change between the normal mode and the idle mode is initiated based on an idle mode condition (IDL), wherein in the idle mode, at least the monitoring circuit (14) and the current sensing circuit (13) are inactive; and wherein a change between an idle mode and a diagnostic mode is initiated based on a diagnostic enable signal (S DEN ), wherein in the diagnostic mode, the monitoring circuit (14) remains inactive while the current sensing circuit (13) is active.

15. The method according to claim 14, wherein a change from the normal mode to the idle mode is not performed until the normal mode has been operated for a defined period of time.

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