SEMICONDUCTOR FUSE WITH MEASUREMENT CIRCUIT FOR THE DETECTING OF A DRIFT OF THE GATE THRESHOLD VOLTAGE

A semiconductor fuse for disconnecting an electric consumer from an energy supply source for a battery electric vehicle includes at least one semiconductor switch element that is connected between the energy supply source and the electric consumer. The semiconductor switch element includes a gate control terminal for controlling a switch-on and switch-off of the semiconductor switch element. The semiconductor fuse includes: a driver circuit for applying a driver voltage that is lower than a predetermined gate threshold voltage of the semiconductor switch element at the gate control terminal of the at least one semiconductor switch element; a measurement circuit for determining a gate charge at the gate control terminal; and a control system that detects a drift of the gate threshold voltage based on the gate charge and indicates an issue with the semiconductor switch element based on the detected drift of the gate threshold voltage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a which claims priority to and the benefit of DE 10 2023 105 112.1 filed on Mar. 1, 2023. The disclosure of the above application is incorporated herein by reference.

FIELD

The present disclosure relates to the field of electrical and electronic fuses for switching off overcurrents in battery electric vehicles. The present disclosure relates to a semiconductor fuse with a measurement circuit for detecting a drift of the gate threshold voltage for a battery electric vehicle.

BACKGROUND

An electric fuse, such as a melting fuse, is commonly used when switching off sustained overcurrents within the high-voltage (HV) domain in battery electric vehicles. The melting fuse may melt due to the associated heat development and switches off the current before a threshold current is reached. An electronic fuse with semiconductors may be used as an alternative thereto. In an electronic fuse, the overcurrent are first detected before the switch-off process can be initiated. For this purpose, the overcurrent that runs over the electric fuse element may be detected and evaluated. Various methods that perform a switch-off based on the calculation of the line temperature or the average current exist for the evaluation. However, it has been shown that such a switch-off is too slow, and the electronic fuse may be adversely affected in the event of suddenly occurring short-circuit incidents.

SUMMARY

The present disclosure provides a concept for switching off overcurrents in battery electric vehicles.

The present disclosure is based on the idea of providing a semiconductor-based fuse or semiconductor fuse, also referred to in the following as digital fuse (“dFuse”), which detects threshold currents, such as, for example, short-circuit currents, and can disconnect them faster than circuit breakers, melting fuses, or Pyrofuses. Diagnostics are predetermined for the semiconductor depending on the technology, such as, for example, SIC-MOSFET, IGBT, SI-MOSFET, etc. in order to provide a disconnection with the semiconductor fuse according to ASIL B in the HV domain. One such diagnostic is the gate threshold voltage drift detection with the aid of a gate charge measurement, as presented in this disclosure. This provides that no undesired switch-on occurs or that a switch-off is provided in the event of a short circuit.

The gate threshold voltage drift detection presented herein functions as follows: before the main fuses or, depending on the installation location of the dFuse, the second main fuse activates the entire system, a voltage is applied at the control terminal (gate in the case of a MOSFET) that is lower than the typical gate threshold voltage, for example, 4V.

The gate charge may be determined with the aid of a voltage measurement at the gate resistance and subsequent integration. The linear gate-source capacitance is charged up to the threshold voltage. If a drift of the gate threshold voltage has occurred, the non-linear gate-drain capacitance (Miller capacitance) is also charged and represents a jump in the gate charge. This non-linear increase may be detected with the aid of a suitable measurement circuit and a shift of the gate threshold voltage can thus be deduced.

The gate threshold voltage drift detection can be used here in all types of electronic fuses or dFuses or semiconductor fuses, both within the low-voltage (LV) domain and within the high-voltage (HV) domain. An HV semiconductor fuse that fulfills the ASIL-B or higher standards for disconnection may be provided with the gate threshold voltage drift detection described herein. Conventional products may not fulfill these standards.

According to a first aspect, the present disclosure provides a semiconductor fuse for disconnecting an electric consumer from an energy supply source for a battery electric vehicle, wherein the semiconductor fuse includes: at least one semiconductor switch element that can be connected between the energy supply source and the electric consumer, wherein the at least one semiconductor switch element includes a gate control element for controlling a switching on and off of the semiconductor switch element in order to connect or disconnect the electric consumer from the energy supply source; a driver circuit configured for applying a driver voltage at the gate control terminal of the at least one semiconductor switch element, the driver voltage being lower than a predetermined gate threshold voltage of the at least one semiconductor switch element; a measurement circuit configured for determining a gate charge at the gate control terminal of the at least one semiconductor switch element; and a control system configured for detecting a drift of the gate threshold voltage based on the gate charge, and for indicating a malfunction of the at least one semiconductor switch element in the event where the drift of the gate threshold voltage is detected.

In the event where the drift of the gate threshold voltage is detected, the control system may diagnose a malfunction of the at least one semiconductor switch element and quickly switch off the at least one semiconductor switch element so that it may be exchanged.

Due to the gate threshold voltage drift detection, such a semiconductor fuse offers the technical advantage of the diagnosis of whether the semiconductor switch element is still functional and can be switched off. The semiconductor fuse provides that an undesired switch-on is inhibited, or that a switch-off is provided in the event of a short circuit.

The semiconductor fuse can thus provide functions according to ASIL standards.

In a field-effect transistor or MOSFET, the gate threshold voltage is the gate voltage or gate source voltage at which an appreciable current flows in relation to the maximum drain current. The gate threshold voltage may be taken from data sheets of the transistors. In a field-effect transistor, the power path of the semiconductor switch element is the path between drain and source terminal.

According to one form of the semiconductor fuse, the control system is configured for controlling the driver circuit, applying the driver voltage at the gate control terminal of the at least one semiconductor switch element; and the control system is configured for controlling the measurement circuit to determine the gate charge at the control terminal of the at least one semiconductor switch element in response to the application of the driver voltage at the gate control terminal.

This results in that the measurement circuit can work synchronously with the driver circuit, and the gate charge can be determined.

According to one form of the semiconductor fuse, the gate control terminal of the at least one semiconductor switch element includes a gate resistor; and the driver circuit is configured for applying the driver voltage at the gate resistor of the gate control terminal.

This results in a voltage difference over the gate resistor which may be used for determining a current flow, and thus the gate charge.

According to one form of the semiconductor fuse, the measurement circuit is configured for determining a gate current at the gate resistor and the gate charge at the gate control terminal based on the gate current.

This may result in the gate charge being easily determined via the gate current, since a mathematical relationship exists between gate current and gate charge.

According to one form of the semiconductor fuse, the measurement circuit is configured for determining the gate current based on a difference of the given driver voltage applied at the gate resistor and a given voltage applied at the gate control terminal.

This results in that the gate current can be easily determined via Ohm's law since the gate current can be determined from the differential voltage at the gate resistor and the gate resistance with a known value of the gate resistance.

According to one form of the semiconductor fuse, the measurement circuit is configured for determining the gate charge based on a temporal integration of the gate current.

This results in the gate charge can be easily determined, since the relationship between electric current I and charge Q is given according to the formula I=dQ/dt.

According to one form of the semiconductor fuse, the control system is configured for detecting the drift of the gate threshold voltage based on a non-linear increase of the gate charge.

This results in that the drift of the gate threshold voltage can be determined. If a drift of the gate threshold voltage has occurred, the non-linear gate-drain capacitance is also charged in addition to the gate-source capacitance. A non-linear increase of the gate charge may be associated therewith.

According to one form of the semiconductor fuse, the non-linear increase of the gate charge is based on a non-linear charging process of a gate-drain capacitance of the at least one semiconductor switch element.

This results in that the non-linear increase of the gate charge may be easily detectable, with the result that the drift of the gate threshold voltage is easily detectable.

According to one form of the semiconductor fuse, the control system is configured for detecting the drift of the gate threshold voltage based on a comparison of the gate charge with a predetermined sequence of the gate charge with respect to a gate source voltage of the at least one semiconductor switch element.

This results in this characteristic being the same for every semiconductor switch element over the sequence of the gate charge, with the result that the drift of the gate threshold voltage may be determined based on data sheets of the semiconductor switch element.

According to one form of the semiconductor fuse, the predetermined sequence of the gate charge increases linearly with respect to the gate source voltage of the at least one semiconductor switch element up to the gate threshold voltage, then displays a jump and increases further after the jump.

This results in that a small drift of the gate threshold voltage already has large effects on the gate charge due to this characteristic with the jump, so that the drift of the gate threshold voltage may be determined based on the gate charge.

The figures are merely schematic representations and serve only to clarify the present disclosure. Identical or functionally identical elements are provided throughout with the same reference numerals.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings which are a part thereof, and in which specific forms are shown as illustration, in which the present disclosure can be implemented. It is understood that other forms can also be used, and structural or logical changes can also be undertaken without deviating from the concept of the present disclosure. The following detailed description is therefore not to be understood in a limiting sense. It is furthermore understood that the features of the different examples described herein can be mutually combined if not specifically indicated otherwise.

The aspects described with reference to the drawings, in which identical reference numerals generally refer to identical elements. Numerous specific details are presented in the following description for the purpose of explanation in order to convey a detailed understanding of one or more aspects of the present disclosure.

However, one or more aspects can be embodied with a lesser degree of the specific details. It is understood that other forms can be used, and structural or logical changes can be undertaken without deviating from the concept of the present disclosure.

FIG.1shows a schematic circuit diagram of a charging system100for charging a battery of a battery electric vehicle.

The charging system100comprises electrical and electronic components of the vehicle, which are shown on the left side, and electrical and electronic components of the charging infrastructure, which are shown on the right side. The charging infrastructure comprises a charging column120for charging the battery140of the vehicle, to which a capacitor C1is connected in parallel and an inductance L1is connected in series.

On the vehicle side, the electrical and electronic components of the vehicle comprise a battery140for powering the vehicle, or an HV storage connected in series to the inductance L3at a first pole and an inductance L4at a second pole of the battery140in the charging current path130.

An S-Box110(switch box or switchbox) is connected in the vehicle in the charging current path130, wherein the S-Box110facilitates a charging of the battery140. The S-Box110is also connected to a traction path as well as one or more auxiliary consumer paths. The S-Box110controls the charging of the battery140and the operation of the traction path and the auxiliary consumer paths via the battery140. Switches for switching on the charging infrastructure are not shown.

The traction path comprises an electric motor150, to which a capacitor C2is connected in parallel and an inductance L2is connected in series.

The auxiliary consumer paths comprise one or more electronic components connected in parallel, such as, for example, PTC151and KMV152, to which a capacitor C3is connected in parallel and an inductance L5is connected in series.

The S-Box110comprises a charging infrastructure-side fuse F1200, which can be a semiconductor fuse200according to the present disclosure. The S-Box110further comprises a battery-side fuse F3, and inductance LS-Box, and a circuit with switches S31and S32connected in parallel, which are connected in series to the fuse F1in the charging current path130. The battery-side fuse F3can also be a semiconductor fuse200according to the present disclosure. A second circuit with switches S4and S2branches off between the fuse F1and the inductance LS-Boxin order to connect the traction path and the auxiliary consumer paths to the battery140when the vehicle is disconnected from the charging infrastructure. The auxiliary consumer paths are connected to the second circuit via a fuse F2. The fuse F2can also be a semiconductor fuse200according to the present disclosure in which the fuse F2then does not serve to disconnect the charging current path130but rather to disconnect the current path between battery140and auxiliary consumers151,152.

The S-Box110further comprises a capacitor CS-Boxconnected in parallel to the charging infrastructure.

FIG.2shows a simplified block circuit diagram of a semiconductor fuse200according to the present disclosure for a battery electric vehicle.

The semiconductor fuse200serves for securely disconnecting an electrical consumer112from an energy supply source111for a battery electric vehicle. This can be, for example, a disconnection of the battery140from the charging column120, as shown inFIG.1, or a disconnection of the electric motor150or the auxiliary consumers151,152from the battery140, as shown inFIG.1.

The semiconductor fuse200comprises at least one semiconductor switch element211that can be connected between the energy supply source111and the electrical consumer112. InFIG.2, one such semiconductor switch element211is shown, although there can be a plurality of semiconductor switch elements here, which are connected, for example, in parallel to each other in order to increase the current-carrying capacity of the entire circuit, or also a parallel circuit of semiconductor switch element pairs, in which the switch elements of the respective pairs are oppositely interconnected in series in order to produce a bidirectional blocking.

The at least one semiconductor switch element211includes a gate control terminal212for controlling a switch-on and switch-off of the semiconductor switch element211in order to connect the electrical consumer112to the energy supply source111or disconnect it from the energy supply source111. The semiconductor switch element211can be, for example, a MOSFET or an IGBT in which the gate control terminal212corresponds to the gate terminal.

The semiconductor fuse200comprises a driver circuit221configured for applying a driver voltage223at the gate control terminal212of the at least one semiconductor switch element211, in which the driver voltage223is lower than a predetermined gate threshold voltage501(seeFIG.5) of the at least one semiconductor switch element211.

The predetermined gate threshold voltage501is also referred to as the nominal gate threshold voltage and can be read from data sheets of the semiconductor switch elements211.

A driver voltage223which is lower by a predetermined threshold value than the predetermined gate threshold voltage501can be applied here so that a natural fluctuation of the gate threshold voltage501does not lead to an inadvertent drift detection.

A lowering of the threshold voltage is desired for the disconnection and also for the case to be detected. A positive drift of the gate threshold voltage501could also be desired for other applications. For this purpose, it could be desired to apply a driver voltage223with which such a positive drift can be detected, for example, a driver voltage223that is higher than the gate threshold voltage501.

InFIG.5an example sequence500of the gate charge with respect to the gate source voltage according to a data sheet of the semiconductor switch element211from which the characteristic gate threshold voltage501can be seen is represented.

Referring back toFIG.2, the semiconductor fuse200includes a measurement circuit222, which is configured for determining a gate charge227at the gate control terminal212of the at least one semiconductor switch element211.

The semiconductor fuse200further comprises a control system220that is configured for detecting a drift of the gate threshold voltage501based on the gate charge227and to indicate an issue with the at least one semiconductor switch element211in the event of detection of the drift of the gate threshold voltage501.

The control system220can be configured for controlling the driver circuit221to apply the driver voltage223at the gate control terminal212of the at least one semiconductor switch element211.

The control system220can be configured for controlling the measurement circuit222to determine the gate charge227at the gate control terminal212of the at least one semiconductor switch element211in response to the application of the driver voltage223at the gate control terminal212.

The gate control terminal212of the at least one semiconductor switch element211can include a gate resistor R8, as shown in more detail inFIG.3. The driver circuit221can be configured for applying the driver voltage223at the gate resistor R8of the gate control terminal212.

The measurement circuit222can be configured for determining a gate current225at the gate resistor R8and the gate charge227at the gate control terminal212based on the gate current225, as shown in more detail inFIG.3.

The measurement circuit222can be configured for determining the gate current225based on a difference of the driver voltage223applied at the gate resistor R8, and a gate voltage226applied at the gate control terminal212, as shown in more detail inFIG.3.

The measurement circuit222can be configured for determining the gate charge227based on an integration of the gate current225over the time, as shown in more detail inFIG.3.

The control system220can be configured for detecting the drift of the gate threshold voltage501based on a non-linear increase of the gate charge227, for example, corresponding to the representation inFIG.5.

The non-linear increase of the gate charge227can be based on a non-linear charging process of a gate-drain capacitance of the at least one semiconductor switch element211, as described in more detail further below.

The control system220can be configured for detecting the drift of the gate threshold voltage501based on a comparison of the gate charge227to a predetermined sequence500of the gate charge227with respect to a gate source voltage of the at least one semiconductor switch element211.

The predetermined sequence500of the gate charge227with respect to the gate source voltage of the at least one semiconductor switch element211can rise linearly, as shown inFIG.5, up to the gate threshold voltage501, then display a jump502, and increase further after the jump502.

FIG.3shows a circuit diagram of a semiconductor fuse200according to one form of the present disclosure.

The semiconductor fuse200inFIG.3corresponds to the semiconductor fuse200shown inFIG.2, wherein details are shown inFIG.3regarding the interconnection of the driver circuit221and the measurement circuit222with the semiconductor switch element211. The semiconductor switch element211can be a MOSFET (M1), as shown by way of example inFIG.3.

The semiconductor switch element211includes a gate control terminal212for controlling a switch-on and switch-off of the semiconductor switch element211. The gate control terminal212corresponds to the gate terminal of the MOSFET M1, as shown inFIG.3.

The driver circuit221is configured for applying a driver voltage (U_G-Driver)223at the gate control terminal212of the MOSFET M1which is lower than a predetermined gate threshold voltage501of the MOSFET M1. The driver circuit221can be, for example, a voltage source V1.

The measurement circuit222is configured for determining a gate charge227(Q-GATE) at the gate control terminal212of the MOSFET M1.

The control system220(seeFIG.2) is configured for detecting a drift of the gate threshold voltage501based on the gate charge227, and for switching off the MOSFET M1in the event the drift of the gate threshold voltage501is detected.

The gate control terminal212of the MOSFET M1includes a gate resistor R8. The driver circuit221is configured for applying the driver voltage223to the gate resistor R8of the gate control terminal212.

The measurement circuit222is configured for determining a gate current225at the gate resistor R8and the gate charge227at the gate control terminal212based on the gate current225, as shown inFIG.3. Here, the gate current225is determined as (V(U_G-Driver)−V(U_G-MOSFET))/100, wherein the 100 corresponds to a resistance value of the gate resistor R8.

The measurement circuit222is configured for determining the gate current225based on a difference of the driver voltage V(U_G-Driver)223, applied at the gate resistor R8and a gate voltage V(U_G-MOSFET)226applied at the gate control terminal212, as shown inFIG.3.

The measurement circuit222is configured for determining the gate charge227(Q_GATE) based on an integration of the gate current225over the time, as shown inFIG.3: V=idt((V(U_G-Driver)−V(U_G-MOSFET))/100).

The mode of operation of the semiconductor fuse200is explained in more detail in the following.

Before the main fuses or, depending on the installation location of the dFuse, the second main fuse enables or activates the entire system (seeFIG.1), a voltage is applied at the gate control terminal212(gate in the case of a MOSFET) of the dFuse200with the aid of a driver circuit221(V1), which voltage is lower than the typical gate threshold voltage226(U_G-MOSFET).

With a measurement circuit222(shown inFIG.3as B1), the differential voltage U_G-Driver-U_G-MOSFET is measured at the gate resistor R8and divided by the value of R8(corresponds to the gate current225) and subsequently integrated (corresponds to the gate charge227).

FIG.4shows a diagram400with example time sequences of the gate charge227with different gate voltages.

Until the gate threshold voltage is reached, the gate charge227increases linearly with the gate voltage226, as can be seen from the curves401,402,403. If a drift of the gate threshold voltage has happened also the non-linear gate-drain capacitance is charged in addition to the gate-source capacitance. A non-linear increase of the gate charge227is detected, as can be seen from the curves404and405.

FIG.5shows a diagram of an example sequence500of the gate charge227with respect to the gate source voltage according to a data sheet of the semiconductor switch element211.

The values for the gate charge227can be detected and the non-linear increase when the threshold voltage501is reached are documented in the component data sheets, as shown by way of example inFIG.5.

As can be seen from the sequence inFIG.5, the measurement is in order with a gate voltage of 4V and approximately 50 nC charge. In contrast, with a gate voltage of 4V and approximately 90 nC charge, the measurement is not in order since the Miller capacitance has been charged and the gate threshold voltage501has shifted downward.