USE OF AN ELECTRONIC FUSE AS A DAMPING ELEMENT

[0001] This disclosure relates in general to a method of using an electronic fuse

(e-fuse) as a damping element.

[0002] An e-fuse fuse is a protection device which may trip dependent on a current and a time duration the current flows. For example, the e-fuse may trip substantially in stantaneously if the current is higher than a maximum current, does not trip if the cur rent is a rated current or below the rated current, and trips after a delay time that is de pendent on the current if the current is between the rated current and the maximum cur rent. An e-fuse may be used to protect a load and a cable between a power source and the load. An e-fuse may include an electronic switch, and a drive circuit configured to drive the electronic switch.

[0003] An e-fuse may be used in various kinds of applications such as, a drive train of an electric vehicle or an industrial distribution circuit, and be connected be tween a power source and a load. For example, A drive train of an electric vehicle may include a plurality of different loads and one or more power sources. Such drive train can be considered as a rather complex RLC circuit, that is, a circuit that includes one or more resistances (R), one or more inductances (L), and one or more capacitances (C). In an RLC circuit, undesired oscillations of currents and/or voltages in the RLC circuit may occur, for example, when a power consumption of one of the loads changes. It is desirable to dampen such oscillations.

[0004] One example relates to a method. The method includes increasing an on- resistance of an e-fuse in order to dampen oscillations in a circuit that includes the e- fuse.

[0005] Examples are explained below with reference to the drawings. The draw ings serve to illustrate certain principles, so that only aspects necessary for understand ing these principles are illustrated. The drawings are not to scale. In the drawings the same reference characters denote like features. [0006] Figures 1 A and IB schematically illustrate examples of an e-fuse;

[0007] Figures 2A and 2B illustrate one example of an electronic circuit that in cludes an e-fuse and one example of a load, respectively;

[0008] Figure 3 illustrates an example of an electronic circuit that includes sev eral e-fuses;

[0009] Figures 4A - 4D illustrates examples of devices that may be included in an electronic circuit of the type shown in Figure 3

[0010] Figure 5 show timing diagrams of signals occurring in an electronic cir cuit of the type shown in Figure 4 when implemented with conventional fuses;

[0011] Figure 6 illustrates one example of an e-fuse that may be operated with an increased on-resistance;

[0012] Figure 7 illustrates another example of an e-fuse that may be operated with an increased on-resistance;

[0013] Figure 8 shows one example of an electronic circuit that includes an e- fuse and a controller controlling the e-fuse; and

[0014] Figure 9 shows timing diagrams of signals occurring in an electronic cir cuit of the type shown in Figure 4 when implemented with e-fuses which are at least temporarily operated with an increased on-resistance.

[0015] In the following detailed description, reference is made to the accompa nying drawings. The drawings form a part of the description and for the purpose of il lustration show examples of how the invention may be used and implemented. It is to be understood that the features of the various embodiments described herein may be com bined with each other, unless specifically noted otherwise. [0016] Figure 1A schematically illustrates an e-fuse 1. The e-fuse 1 includes an electronic switch 2 and a drive circuit 3. The electronic switch 2 includes a drive input 21 configured to receive a drive signal SDRV from the drive circuit 3 and a load path 22- 23 between a first load node 22 and a second load node 23. The electronic switch 2 switches on or off dependent on the drive signal SDRV. In an on-state (switched-on state) the electronic switch 2 is configured to conduct a current through the load path 22-23.

In the off-state (switched-off state), the electronic switch 2 is configured to block a cur rent, provided that a voltage across the load path 22-23 is lower than a voltage blocking capability of the electronic switch 11. The "voltage blocking capability" is the maxi mum voltage VI the electronic switch 11 can withstand in the off-state.

[0017] The electronic switch 11 includes an inherent on-resistance R2, which is an electric resistance of the electronic switch 2 when the electronic switch 2 is in the on- state. This on-resistance R2 is represented by a resistor in the circuit diagram shown in Figure 1.

[0018] The e-fuse 1 illustrated in Figure 1 A is a protection device which may trip dependent on a load current 12 through the load path 22-23 and a time duration the load current 12 flows. "Tripping of the e-fuse 1" includes that the drive circuit 3 switches off the electronic switch 2. For example, the e-fuse 1 may trip substantially in stantaneously if the load current 12 is higher than a maximum current, does not trip if the load current 12 is a rated current or below the rated current, and trips after a delay time that is dependent on the current level of the load current 12 if the load current 12 is between the rated current and the maximum current. According to one example, the e- fuse trips in accordance with an I ² t curve.

[0019] In order to monitor and evaluate the load current 12, the drive circuit 3 may receive a load current signal S12 that represents the load current 12. The load current signal S12 may be generated by a conventional current measurement circuit (not shown in Figure 1). Alternatively or in addition to the load current 12 the drive circuit 3 may monitor and evaluate further parameters of the e-fuse in order to switch off the elec tronic switch 2. According to one example, the at least one further parameter is a tem perature of the e-fuse, wherein the drive circuit 3 may be configured to switch off the electronic switch 2 when the temperature has reached a predefined temperature thresh old.

[0020] The drive circuit 3 may switch on the electronic switch 2 when a supply voltage VSUP (illustrated in dashed lines in Figure 1 A) received by the drive circuit 3 has reached a voltage level that is sufficient for the drive circuit 3 to switch on the elec tronic switch 2. In addition to the supply voltage VSUP, the drive circuit 3 may receive an input signal SIN. In this example, the input signal SIN may enable or disable the e- fuse, wherein the drive circuit 3 switches on the electronic switch 2 only when enabled by the input signal SIN.

[0021] Figure IB shows the e-fuse according to Figure 1 A and illustrates further options that may be included in the e-fuse. According to one example, the e-fuse in cludes an interface circuit 11 which is configured to provide for a communication be tween the e-fuse 1 and external circuitry, such as a microcontroller. Via the interface circuit 11 the e-fuse may receive instructions (control signals) or output information. In structions received by the e-fuse via the interface circuit 11 may include instructions to switch on or off the electronic switch 2 (corresponding to signal SIN shown in Figure 1 A) or instructions to adjust, in particular, increase an on-resistance of the electronic switch 2. The latter is explained in detail herein further below. Information output by the e-fuse 1 via the interface circuit 11 may include information on a status of the e-fuse 1, wherein the status may include one of "switched on", "tripped", or "increased re sistance".

[0022] The interface circuit 11 can be a conventional interface circuit, wherein the specific implementation is dependent on the type of communication channel it is connected to. According to one example, the communication channel is a communica tion bus.

[0023] The e-fuse shown in Figure IB further includes a control logic 12, which may be implemented by a microprocessor. The control logic 12 is coupled to the inter face circuit 11 and to the drive circuit 3. According to one example, the control logic 12 processes instructions received by the e-fuse via the interface circuit 11 and causes the drive circuit 3 to drive the electronic switch 2 in accordance with these instructions.

This may include switching on or switching off the electronic switch 2 or increasing the on-resistance of the electronic switch 2. Further, the control logic 12 may generate the status information output by the e-fuse. For generating the status information, the con trol logic may receive the load current signal S12.

[0024] According to one example, the drive circuit 3 is configured to receive a load path voltage signal Sv2 that represents a voltage V2 across the load path of the electronic switch 2 and is configured to drive the electronic switch 2 dependent on the load path voltage signal Sv2. This may include that the drive circuit 3 reduces the on-re sistance of the electronic switch 2 when, in the on-state, the load path voltage V2 reaches above a predefined threshold. The load path voltage signal Sv2 may also be re ceived by the control logic 11.

[0025] According to one example, a freewheeling circuit 13 is connected in par allel with the load path of the electronic switch 2.

[0026] In Figure IB, a current measurement device 13 that is configured to measure the load current and provide the current measurement signal S12 is schemati cally illustrated. The current measurement device 13 may be implemented in a conven tional way and may include, for example, a shunt resistor, or an inductive current sen sor. According to another example the electronic switch 2 is a transistor, such as a MOSFET, and the current measurement device 13 includes a so-called sense transistor coupled to the transistor forming the electronic switch.

[0027] An e-fuse 1 of the type shown in Figures 1 A or IB may be used to pro tect a device and/or a cable between a power source and the load. Figure 2A schemati cally illustrates an electronic circuit that includes an e-fuse 1 connected between a power source (power supply) 4 and a device 5. The e-fuse 1 may be configured to pro tect the device 5 and/or a cable (wire, harness) interconnecting the power source 4, the e-fuse 1 and the device 5. [0028] The device 5 may be any kind of device that receives power from the power source 4 or supplies power to the power source 4. Referring to Figure 2B, the de vice 5 may include in inverter 51 coupled to the power source 4 via the e-fuse, and a motor 52 coupled to the inverter and driven by the inverter 51.

[0029] Figure 3 illustrates one example of a more complex system (electronic circuit) that includes a power source (power supply) 4 connected to a power supply bus 41 and a plurality of devices 5i, 52, 53 that are each connected to the power supply bus through wires and respective e-fuses li, I2, I 3. Optionally, as illustrated in Figure 3, a further e-fuse may be connected between the power source 4 and the bus 41. The sys tem illustrated in Figure 3 4 is a drive train of an electronic vehicle or a drive train in an industrial application, for example. The power source 4 may be a battery in this exam ple.

[0030] The devices 5i, 52, 5 ₃ connected to the power source 4 can be imple mented in various ways, wherein the devices can be of the same type or can be of differ ent types. Further, although three devices are illustrated in Figure 23, this is only an ex ample. An arbitrary number of devices can be connected to the power supply 4. Some examples of devices that may be included in the system are explained with regard to Figures 4A to 4D in the following. In each of these figures, reference number 5 repre sents an arbitrary one of the devices shown in Figure 3.

[0031] Figure 4A illustrates one example of a device that includes an inverter 52 and an electric motor 52, as already explained with reference to Figure 2.

[0032] In the example shown in Figure 4B, the device 5 includes a DC-DC con verter 53 that is connected to the power supply. The DC-DC converter 53 may be con figured to regulate an output voltage V53 or an output current 153 and supply a load 54 connected to the DC-DC converter. The load may be any kind of DC load such as, for example, a DC motor, an LED (Light Emitting Diode) string, a heater, or the like. [0033] According to another example illustrated in Figure 4C, the device 5 in cludes an on-board charger (OPC), wherein this OBC is configured to charge the power supply 4.

[0034] According to yet another example illustrated in Figure 4D, the device 5 includes a power storage device such as a further battery 56. This storage device may be charged by the power supply 4 and may act as a remote power supply for certain loads or may act as a backup power supply for the loads connected to the supply bus 41.

[0035] The devices 5I-53 may include capacitors, resistances and inductances. In addition, the cables (wires, harnesses) interconnecting the fuses li-b, the devices 5I-53 and the bus 41 may include (parasitic) inductances, resistances and capacitances. The overall system therefore forms an RLC circuit, that is, a circuit that includes one or more resistances (R), one or more inductances (L), and one or more capacitances (C). In this type of RLC circuit parasitic oscillations of voltages across the devices 5I-53 and of currents into or from the devices 5I-53 may occur, in particular, when a power consump tion of one of the devices 5I-53 changes. A change of a power consumption of one of the devices 5I-53 is associated with a change of the respective current into the device 5i- 53, for example.

[0036] Such parasitic oscillations are illustrated in Figure 5, wherein Figure 5 shows timing diagrams of voltages across the loads 5I-53 and of currents into the loads 51-53 in a system of the type shown in Figure 4 when implemented with conventional fuses instead of e-fuses or when operating the e-fuses li-b in a conventional way. "Op erating an e-fuse in a conventional way" includes either switching on or switching off the e-fuse. Oscillations of the type illustrated in Figure 5 are highly undesirable. It is therefore desired to dampen such oscillations.

[0037] According to one example, damping such oscillation includes at least temporarily increasing the on-resistance of one or more of the e-fuses li-b included in the system. [0038] “Increasing the on-resistance” of an e-fuse includes operating the e-fuse in such a way that its on-resistance is higher than a minimum on-resistance, but still low enough to allow a load current 12 to flow through the respective e-fuse. According to one example, increasing the on-resistance includes adjusting the on-resistance such that it is between 1.1 times and 1000 times, in particular between 2 times and 100 times, or between 2 times and 10 times of the minimum on-resistance.

[0039] There are various ways to implement an e-fuse 1 such that its on-re sistance can be (temporarily) increased. Two different examples are illustrated in Fig ures 6 and 7.

[0040] In the example shown in Figure 6, the electronic switch 2 of the e-fuse 1 includes a plurality of switching elements 2i, 22, 2 _n connected in parallel, wherein each of these switching elements 2i, 22, 2 _n is driven by the drive circuit 3 through a respec tive drive signal SDRVI, SDRV2, SDRVII. Each of these switching elements 2i-2 _n has a re spective on-resistance R2i, R22, R2 _n in the on-state. In this type of e-fuse, the on-re sistance of the electronic switch 2 can be adjusted by selecting the number of switching elements that are in the on-state and the number of switching elements that are in the off-state. The overall on-resistance of the electronic switch 2 is given by the parallel cir cuit of the on-resistances of those switching elements that are in the on-state. The switching elements 2i-2 _n can be implemented using any kind of electronic switch such as a transistor, for example.

[0041] In the example illustrated in Figure 7, the electronic switch 2 includes a voltage controlled electronic switch that has an on-resistance which is dependent on the drive signal SDRV received by the drive circuit 3. The drive circuit 3 may be configured to adjust the drive signal SDRV such that the drive signal SDRV is between an off-level and a maximum on-level. The electronic switch 2 switches off when the drive signal SDRV has the off-level and the electronic switch 2 is in the on-state and has a minimum on-resistance, when the drive signal SDRV has the maximum on-level. The on-resistance of the electronic switch 2 increases when the drive signal SDRV is below the maximum on-level, but the electronic switch 2 is still in the on-state. [0042] Referring to Figure 7, the electronic switch may be implemented as a

MOSFET. In a MOSFET, the load path 22, 23 is an internal circuit path between a drain node D and a source node S, and the drive input is formed by a gate node G and the source node S. The drive signal SDRV is a voltage between the gate node G and the source node S (wherein the drive voltage may also be referred to as gate-source volt age). The on-resistance of a MOSFET is dependent on the gate-source voltage, wherein the on-resistance decreases when the gate-source voltage increases within a certain volt age range (wherein there is no further decrease of the on-resistance when the gate- source voltage has reached a certain threshold and further increases).

[0043] Implementing the electronic switch 2 as a MOSFET as illustrated in Fig ure 7 is only an example. Any other kind of transistor devices such as, for example, an IGBT (Insulated Gate Bipolar Transistor), a JFET (Junction Field-Effect Transistor), a BJT (Bipolar Junction Transistor), a HEMT (High Electron-Mobility Transistor) may be used as the electronic switch 2 as well.

[0044] It should be noted that Figures 6 and 7 only illustrate the drive circuit 3 and the electronic switch 2 of the e-fuse. In addition to these components the e-fuse 1 may include one or more of the components illustrated in Figure IB and explained with reference to this drawing. In each case, the e-fuse 1 may include a package (housing) in which the components are integrated. According to one example, the electronic switch 2 and the drive circuit 3 are integrated in the same semiconductor chip that is arranged in the housing. According to another example, the electronic switch 2 and the drive circuit 3 are integrated in two separate semiconductor chips, wherein both of these semicon ductor chips are arranged in the housing.

[0045] Operating the electronic switch 2 of the e-fuse 2 with an increased on-re sistance may be achieved in various ways. According to one example, operating the electronic switch 2 includes at least one of (a) monitoring the electronic circuit, in which the at least one e-fuse 2 is employed, for the occurrence of operating conditions which are likely to cause oscillations and operating the electronic switch 2 with an in creased on-resistance upon detecting such operating states; or (b) detecting oscillations of voltages and/currents in a current path that includes the at least one e-fuse and operat ing the electronic switch 2 with an increased on-resistance upon detecting such oscilla tions.

[0046] One operating condition which is likely to cause oscillations is a change of a power consumption of the device 6 connected to the e-fuse 1. According to one ex ample, operating the e-fuse 1 with an increased on-resistance therefore includes moni toring the load current 12 and operating the electronic switch 2 with an increased on-re sistance when, for example, the load current 12 indicates that a power consumption of the respective load has changed. According to one example, monitoring the load current 12 includes detecting a slope of the load current 12. wherein the electronic switch 2 is operated with an increased on-resistance upon detecting that the slope of the load cur rent 12 is higher than a predefined threshold.

[0047] According to one example, alternatively to or in addition to monitoring the load current 12 the voltage V2 across the electronic switch 2 may be monitored and the electronic switch 2 may be operated with an increased on-resistance when the load path voltage V2 indicates that a power consumption of the respective load has changed or upon detecting that a slope of the load path voltage V2 is higher than a predefined threshold.

[0048] A duration for which the electronic switch 2 is operated with the in creased on-resistance may be dependent on the specific type of electronic circuit. Ac cording to one example, this duration is between several nanoseconds (ns) and several ten up to several hundred microseconds (ps), such as between 20 nanoseconds and 900 microseconds, in particular between 20 nanoseconds and 100 nanoseconds.

[0049] Referring to the above, operating the electronic switch 2 with an in creased on-resistance may include detecting oscillations of the load current 12 and/or the load path voltage V2 and operating the electronic switch 2 with an increased on-re sistance upon detecting such oscillations. In this example, the electronic switch 2 may be operated with an increased on-resistance until an amplitude of the oscillations has de creased to below a predefined level. [0050] The functionality of operating the e-fuse 1 with an increased on-re sistance may be implemented in the e-fuse 1 itself such as, for example, in the drive cir cuit 3. That is, the operating conditions that may cause oscillations and/or the oscilla tions itself may be detected by the drive circuit 3. In this case, the drive circuit 3 re ceives at least one of the load current signal S12 and the load path voltage signal Sv2 and includes a resistance control circuit that is configured to detect operating conditions that may cause oscillations and/or oscillations using at least one of these signals S12, Sv2. Ac cording to one example, the resistance control circuit inside the drive circuit 3 includes an oscillation detector that is configured to detect oscillations based on at least one of these signals S12, Sv2.

[0051] According to another example, the system includes a controller (not shown) that controls operation of the different loads and that provides a respective sig nal to the drive circuit 3 indicating that the power consumption of one of the loads has changed or is about to be changed. In this case, the drive circuit 3 may be configured to operate the respective electronic switch 2 with an increased on-resistance upon receiv ing the information that the power consumption of one of the loads has changed or is about to be changed.

[0052] According to another example, the functionality of operating the e-fuse 1 with an increased on-resistance, that is, the resistance control circuit, is implemented outside the e-fuse 1. In this case, the e-fuse 1 receives, from a controller 4, an input sig nal SIN that governs operation of the e-fuse 1 with an increased on-resistance. One ex ample of an electronic circuit that includes an e-fuse 1 and a controller 4 is illustrated in Figure 8.

[0053] In this example, the controller 4 receives at least one of the load current signal S12 and the load path voltage signal Sv2 and generates the input signal SIN that controls operation of the e-fuse 1. According to one example, the controller 4 is config ured to at least one of operating conditions that may cause oscillations, or the oscilla tions itself and is configured to cause the e-fuse to operate with an increased on-re sistance upon detection such operating condition and/or upon detecting such oscilla tions. The at least one of the load current signal S12 and the load path voltage signal Sv2 may be obtained by the e-fuse 1 and provided to the controller 4 by the e-fuse 1 or may be obtained by any other kind of current measurement circuit or voltage measurement circuit (not shown).

[0054] According to one example, the controller 4 controls operation of different loads in a system according to Figure 3, for example, and operates the e-fuse 1 with an increased on-resistance when the load has been controlled such or will be controlled such that the power consumption of the load has changed or will change.

[0055] Although Figure 3 illustrates a system with several devices and several e- fuses, operating an e-fuse with an (at least temporarily) increased on-resistance is not restricted to systems with several devices and e-fuses and is not restricted to drive trains of a vehicle. Instead, an e-fuse may be operated with an increased on-resistance in any kind of electronic circuit, in particular, any kind of automotive or industrial circuit, in which parasitic oscillations may occur and in which these oscillations can be damped by increasing the on-resistance of the e-fuse.

[0056] An improvement that can be achieved by temporarily operating the e- fuses in a system of the type shown in Figure 4 with an increased resistance is illus trated in Figure 9. Figure 9 shows timing diagrams of voltages across the loads 5I-53 and of currents into the loads 5I-53 when the e-fuses I 1-I 3 are temporarily operated with an increased resistance, in accordance with any of the examples explained above. It can be seen from Figure 9 that oscillations of the currents into the loads 5I-53 and the volt ages across the loads 5I-53 are significantly damped, that is, decline much faster than in the conventional scenario illustrated in Figure 5.

[0057] Although the present disclosure is not so limited, the following numbered examples demonstrate one or more aspects of the disclosure.

[0058] Example 1 - A method, comprising: increasing an on-resistance of at least one electronic fuse connected between a power source and respective load. [0059] Example 2 The method of claim 1, wherein increasing the on-re sistance comprises temporarily increasing the on-resistance.

[0060] Example 3. The method of claim 2, wherein temporarily increasing the on-resistance comprises increasing the on-resistance for a duration of between 20 nano seconds and 900 microseconds.

[0061] Example 4. The method of any one of claims 1 to 3, wherein the elec tronic fuse comprises a minimum on-resistance, and wherein increasing the on-re sistance comprises adjusting the on-resistance such that the on-resistance is between 1.1 times and 1000 times, between 2 times and 100 or between 2 times and 10 times of the minimum on-resistance.

[0062] Example 5. The method of any one of claims 1 to 4, wherein the elec tronic fuse comprises a plurality of electronic switches connected in parallel, and wherein increasing the on-resistance comprises switching off at least one but less than each of the plurality of electronic switches.

[0063] Example 6. The method of any one of claims 1 to 4, wherein the electronic fuse comprises a voltage controlled electronic switch con figured to receive a drive voltage, and wherein increasing the on-resistance comprises adjusting the drive voltage such that an on-resistance of the electronic switch increases.

[0064] Example 7. The method of any one of the preceding claims, wherein the electronic fuse is connected between a power source and a device.

[0065] Example 8. The method of claim 7, wherein increasing the on-re sistance comprises increasing the on-resistance in response to a current through the electronic fuse.

[0066] Example 9. The method of claim 8, wherein increasing the on-re sistance in response to a current through the electronic fuse comprises: detecting a slope of the current through the electronic fuse, and increasing the on-resistance when the slope is higher than a predefined threshold.

[0067] Example 10. The method of claim 7, wherein increasing the on-re sistance comprises: detecting a change in an operating state of the load, and increasing the on-resistance in response to detecting the change of the operating state.

[0068] Example 11. The method of any one of the preceding claims, wherein the electronic fuse is connected between a power source and a device in a drive train of an electric vehicle.

[0069] Example 12. The method of claim 11, wherein the at least one elec tronic fuse comprises a plurality of electronic fuses each connected between the power source and a respective one of a plurality of devices.

[0070] Example 13. The method of claim 12, wherein at least one of the de vices comprises at least one of an inverter and a motor connected to the inverter; a DC- DC converter and a load connected to the DC-DC converter; an on-board charger; a power storage device.

[0071] Example 14. A system, comprising: at least one electronic fuse con nected between a power source and respective load; and a resistance control circuit con figured to temporarily increase an on-resistance of the e-fuse.

[0072] Example 15. The system of claim 14, wherein the resistance control cir cuit is integrated in the e-fuse.

[0073] Example 16. The system of claim 14, further comprising: a controller coupled to the e-fuse, wherein the resistance control circuit is integrated in the control ler. [0074] Example 17. The system of claim 14, wherein the resistance control cir cuit is configured to temporarily increase the on-resistance of the e-fuse based on at least one of: a current through the e-fuse; a voltage across the e-fuse; a voltage across the load; or an operating condition of the load.

[0075] Example 18. The system of any one of claims 14 to 17, wherein the electronic fuse comprises a minimum on-resistance, and wherein the resistance control circuit is configured to increase the on-resistance such that the on-resistance is between 1.1 times and 1000 times, between 2 times and 100 or between 2 times and 10 times of the minimum on-resistance.

[0076] Example 19. The system of any of claims 14 to 18, wherein the at least one electronic fuse comprises a plurality of electronic fuses each connected between the power source and a respective one of a plurality of devices.

[0077] Example 20. The system of any of claims 14 to 19, wherein at least one of the devices comprises at least one of an inverter and a motor connected to the in verter; a DC-DC converter and a load connected to the DC-DC converter; an on-board charger; a power storage device.