Adjusting a DESAT detection threshold

Abstract

The present invention relates to a device (22) for detecting a bridge short circuit in a power semiconductor module (18) with two parallel switches (20a, 20b) of different technologies, comprising: a voltage interface (24) for receiving a voltage signal with information on a voltage drop across one of the two parallel switches; a status interface (26) for receiving a status signal with information on a current operating state of the power semiconductor module; an adaptation unit (28) for determining a threshold value for a voltage drop in the event of a bridge short circuit based on the status signal; and an output interface (30) for outputting an error signal based on the voltage signal and the threshold value when the voltage drop across the two parallel switches exceeds the determined threshold value.The present invention further relates to a gate driver for a power semiconductor, a traction converter for a vehicle, a method for detecting a bridge short circuit in a power semiconductor module (18) and a computer program product.

Description

[0001] The present invention relates to a device for detecting a bridge short circuit in a power semiconductor module with two parallel switches of different technologies. The present invention further relates to a gate driver for a power semiconductor, a traction converter for a vehicle, a method, and a computer program product.

[0002] The power electronics of electric and hybrid vehicles transfer the traction energy from the battery to the electric motor, converting direct current into alternating current. An AC converter, also known as an inverter, or traction converter, is used for this purpose. Typically, several transistors or other power semiconductors are used, combined to form a power semiconductor module that switches at short, regular intervals. MOSFETs (metal oxide semiconductor field-effect transistors) and IGBTs (insulated gate bipolar transistors) are used as switches in this context. When switched on, the battery current is transferred to the motor (conduction phase). These high-frequency switching processes create an alternating voltage profile, which can then be converted into traction energy in the electric motor.To increase the current carrying capacity, several power semiconductors are usually connected in parallel.

[0003] A short circuit in a power semiconductor due to a defect or due to aging of the component can lead to a phase short circuit. Due to the high currents and voltages, this can lead to dangerous situations. This can also result in fires. Desaturation detection (DESA) is therefore often used to detect a phase short circuit. In this context, a DESAT situation occurs when the voltage across a switch exceeds a threshold during the conduction phase, thereby signaling that the current through the switch exceeds the normal operating range. For example, if the voltage across an IGBT rises to a value of over 5 to 15 volts at full gate voltage, this can indicate a short circuit. As soon as the situation is detected, the switch can be switched off or the phase current can be disconnected.If, after a specified time after the active switch has been switched on, its forward voltage does not fall below a specified value, a DC link short circuit has occurred.

[0004] Current gate drivers for power semiconductors often incorporate such desaturation detection. For example, Texas Instruments' "UCC5880-Q1 isolated 20-A adjustable gate drive IGBT / SiC MOSFET gate driver with advanced protection features for automotive applications" discloses an integrated electronic circuit that includes desaturation detection with preset thresholds up to 14 volts.

[0005] In inverter structures, different semiconductor technologies are sometimes combined to utilize their respective advantages. For example, power semiconductor modules can be used in which MOSFETs are combined with IGBTs and operated in parallel. Furthermore, different semiconductor materials can be used. In this context, DE 10 2020 214 607 A1 discloses a topological semiconductor switch and a semiconductor package, a half-bridge module, a B6 module, an inverter, an electric motor arrangement, and a motor vehicle. The topological semiconductor switch comprises at least two power semiconductors, in particular two power transistors. The topological semiconductor switch has at least one first power semiconductor with a first semiconductor material and at least one second power semiconductor with a second semiconductor material.

[0006] A challenge when connecting multiple power semiconductors with different technologies in parallel within a topological switch lies in specifying an appropriate threshold for desaturation detection. When different technologies with different current-carrying characteristics are used, the short-circuit current of a failed switch of a first technology may be too low to trigger the desaturation detection trigger threshold of the functioning switch of the second technology. An existing short circuit may then go undetected. This can occur particularly when a low load current prevails.

[0007] Based on this, the present invention aims to provide an approach for the reliable detection of bridge short circuits in power semiconductor modules. In particular, reliable bridge short circuit detection should be enabled even when parallel switches of different technologies are used. Dangerous situations and material defects should be avoided.

[0008] To achieve this object, the present invention relates in one aspect to a device for detecting a bridge short circuit in a power semiconductor module with two parallel switches of different technology, comprising: a voltage interface for receiving a voltage signal with information about a voltage drop across a switch of the two parallel switches; a status interface for receiving a status signal with information on a current operating state of the power semiconductor module; an adjustment unit for determining a threshold value for a voltage drop in the event of a bridge short circuit based on the status signal; and an output interface for outputting an error signal based on the voltage signal and the threshold value when the voltage drop across the two parallel switches exceeds the determined threshold value.

[0009] In a further aspect, the present invention relates to a gate driver for a power semiconductor having a device as described above.

[0010] In a further aspect, the present invention relates to a traction converter for a vehicle, comprising: a power semiconductor module for converting a DC voltage of a battery into an AC voltage for an electric motor; and a device as previously described.

[0011] Further aspects of the invention relate to a method configured according to the device, as well as to a computer program product with program code for performing the steps of the method when the program code is executed on a computer. Furthermore, one aspect of the invention relates to a storage medium on which a computer program is stored which, when executed on a computer, effects execution of the method described herein.

[0012] Preferred embodiments of the invention are described in the dependent claims. It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or alone, without departing from the scope of the present invention. In particular, the device, the gate driver, the traction converter, the method, and the computer program product can be designed according to the embodiments described for the device in the dependent claims.

[0013] According to the invention, the threshold value for short-circuit detection (DESAT threshold) is implemented in a variably adjustable manner. In particular, it is proposed that a threshold value be used that is determined based on a current operating state of the power semiconductor module. In this respect, it is proposed that the threshold value be adapted during runtime and made dependent on the operating state of the power semiconductor module. A current operating state is understood in particular to be a current or instantaneous status. For example, sensor-detectable parameters or measured values ​​that reflect this operating state can be used as a status signal. For example, a temperature of the power semiconductor module or a component of the power semiconductor module, a voltage, a current flow (especially phase current), etc., or a variable based on one or more of these parameters / measured values ​​can be used.

[0014] Compared to previous approaches to desaturation detection, adjusting the threshold enables detection of bridge short circuits even in situations where a fixed threshold would not be exceeded.

[0015] This increases the reliability of bridge short circuit detection. Unlike previous approaches that allow presetting a threshold, the inventive approach allows for adjustment during runtime or operation of the power semiconductor module. This, in turn, results in increased reliability in bridge short circuit detection when using parallel switches of different technologies, as changes in the phase current can be addressed. Dangerous situations can be avoided, and material defects can be prevented.

[0016] In a preferred embodiment, the status interface is designed to receive a status signal containing information about a current phase current flowing through the power semiconductor module. The status interface corresponds, so to speak, to a current or current signal interface, via which a status signal can be received that reflects the current flow at the current time. A threshold value can then be used, which is determined based on a current phase current flowing through the power semiconductor module. In this respect, the threshold value can be adjusted during runtime and made dependent on the phase current flowing through the power semiconductor module.

[0017] In a preferred embodiment, the adjustment unit is designed to track the threshold value with the instantaneous phase current. In particular, tracking can result in a threshold value determination that is as realistic as possible. The threshold value is always selected to match the instantaneous phase current. For this purpose, a constant or predefined conversion ratio can be assumed, for example. The use of a lookup table or a characteristic curve is also possible. This results in reliable detection of bridge short circuits at different phase currents.

[0018] In a preferred embodiment, the adaptation unit is configured to determine the threshold based on a previously known saturation current of one of the two parallel switches. In particular, the adaptation unit is configured to determine the threshold based on a comparison of the instantaneous phase current with the saturation current of the switch of the two parallel switches with the lower saturation current. By additionally considering a previously known saturation current, situations in which the phase current exceeds the saturation current of an individual power semiconductor during the active short circuit can be mapped. For example, if one of the two technologies used in parallel is responsible for a large portion of the current conduction, a correspondingly higher threshold can be selected. This results in reliable detection of bridge short circuits.

[0019] In a preferred embodiment, the adaptation unit is configured to determine the threshold based on a selection from a plurality of predefined thresholds. In particular, the selection can be based on a predefined upper threshold and a predefined lower threshold. Several predefined thresholds can be specified in the form of a lookup table. Furthermore, the thresholds can also be determined based on precalibration. In particular, simple implementation is achieved if exactly two predefined thresholds are used (an upper threshold and a lower threshold). This then results in simple switching, which can also be reliably implemented in hardware if necessary.

[0020] In a preferred embodiment, the output interface is designed to interrupt the current flow through the two parallel switches if the voltage drop across the two parallel switches exceeds the determined threshold. To avoid dangerous situations, it is advantageous if the detection of a bridge short circuit directly triggers a response in the form of an interruption of the current flow. This results in a reliable avoidance of dangerous situations caused by short circuits.

[0021] In a preferred embodiment, the device comprises a bypass switch for switching a bypass of an electronic component in a supply line of the voltage interface, in particular a Zener diode. The adjustment unit is designed to determine the threshold based on a selection from a predefined upper threshold and a predefined lower threshold. The bypass switch is designed to bypass the electronic component when the upper threshold has been determined. A hardware switch is used to initiate a change in the threshold. The use of the bypass switch allows for the continued use of regular desaturation detection of an integrated circuit, since the input voltage applied to the corresponding pin of the driver component is adjusted.Depending on whether the upper or lower threshold is selected, the input voltage can be adjusted by bridging the electronic component. It becomes possible to implement a runtime-adjustable threshold using additional circuitry for available components without a runtime-adjustable threshold. This allows for retrofitting. Furthermore, efficient implementation is enabled.

[0022] Herein, a power semiconductor module is understood in particular to be an assembly for use in an inverter structure. Typically, several power semiconductors are combined to form a power semiconductor module. A power semiconductor corresponds in particular to an electronic chip that has one or more integrated circuit components. For example, MOSFETs and / or IGBTs can be used. A different technology is understood in particular to mean a different semiconductor technology. For example, different semiconductor materials can be used and, based on them, different semiconductor technologies can be constructed. MOSFETs and IGBTs, for example, are understood here as different technologies. The terms "first switch" and "second switch" serve to differentiate the terminology. It is understood that both switches can also be controlled via the control interface.It is also understood that one switch can be controlled first and then the other, so that the designation “first switch” and “second switch” can change or transition during operation. A connection can be established directly or indirectly, whereby an indirect connection is understood to mean connecting or interposing another component. Controlling a switch is understood in particular to mean outputting a signal to a control terminal in order to switch the switch on or off, and the term “conducting phase” refers to a time interval. A switch can in particular be a semiconductor switch. A threshold value can be defined absolutely or relatively. For example, a threshold value can include an indication of a percentage value in addition to an absolute value.

[0023] The invention is described and explained in more detail below using selected embodiments in conjunction with the accompanying drawings. They show: Fig. 1 a schematic representation of a vehicle with a traction converter according to the invention; Fig. 2 a schematic representation of a device according to the invention for detecting a bridge short circuit in a power semiconductor module; Fig. 3 a schematic representation of a DESAT circuit; Fig. 4 is a schematic representation of a modified DESAT circuit for a device according to the invention; and Fig. 5 a schematic representation of a method according to the invention.

[0024] In Fig. 1 schematically shows a vehicle 10 with a traction converter 12 according to the invention. The traction converter 12 is arranged between a battery 14 and an electric motor 16 of the vehicle 10 in order to convert the direct current of the battery into the alternating current required by the electric motor 16. The traction converter comprises a power semiconductor module 18 with two parallel switches 20a, 20b of different technologies as well as a device 22 for detecting a bridge short circuit in the power semiconductor module 18. The illustration in Fig. 1 is to be understood as a schematic side sectional view.

[0025] In electric vehicles, power semiconductor modules, each containing multiple power semiconductors, are typically used to generate a three-phase alternating current. In this case, a power semiconductor module 18 is used, which comprises two parallel switches 20a, 20b of different technologies. In particular, the two switches 20a, 20b can comprise a MOSFET on the one hand and an IGBT on the other. Both switches 20a, 20b are arranged in a parallel circuit and switch the same connection. The two parallel switches together form, in particular, a high-side switch or a low-side switch. The switches are controlled via one or more gate drivers (not shown). By using two different technologies in parallel, efficiency advantages can be realized, since, depending on the load, the more suitable technology can be used predominantly for the circuit.

[0026] The device 22 according to the invention enables the detection of a bridge short circuit within the power semiconductor module 18. For this purpose, desaturation detection with a threshold value that can be adjusted during runtime is used. The device according to the invention is designed to adapt a threshold value for desaturation detection based on a current operating state of the power semiconductor module. For example, an instantaneous phase current can be detected and used as the basis for the adjustment. For example, at low phase current, i.e., at low load, a lower threshold value can be selected in order to enable reliable detection of a bridge short circuit even when two switches of different technologies are used in parallel.

[0027] In Fig. Figure 2 schematically shows a device 22 according to the invention for detecting a bridge short circuit in a power semiconductor module with two parallel switches of different technologies. The device 22 comprises a voltage interface 24, a status interface 26, an adaptation unit 28, an output interface 30, and an optional switch 32. The various interfaces and units can be implemented partially or completely in hardware and / or software. In particular, it is possible for the device to be implemented essentially in software that is executed on a driver IC (gate driver). In this case, individual functions can also be generated by wiring using electronic components. The switch can, in particular, correspond to an electronic component and can therefore be embodied in hardware.

[0028] The voltage interface 24 serves to receive a voltage signal containing information about a voltage drop across one of the two parallel switches. In particular, a drain-source or collector-emitter voltage can be measured or received at a MOSFET or an IGBT. The voltage interface 24 can be configured to receive an analog or digital signal. In particular, the voltage interface 24 can correspond to a pin of a semiconductor component or can be addressed via it.

[0029] A status signal containing information about the current operating state of the power semiconductor module is received via the status interface 26. For example, a status signal can be received that includes or represents information about a current phase current through the power semiconductor module. In this case, the status signal can be received based on a measurement in a corresponding shunt resistor, for example. An analog or digital signal can be received via the status interface 26. It is also possible for the status interface 26 to be connected to a bus system in order to receive corresponding information about the current operating state from another source.

[0030] In the adaptation unit 28, the threshold value for the voltage drop in the event of a bridge short circuit is determined based on the status signal. The threshold value is therefore determined and adjusted in the adaptation unit 28 during runtime. In this case, the adaptation unit 28 can be provided for a direct assignment based on a mathematical assignment rule. Likewise, additional use of predefined information, for example a characteristic curve or another assignment rule, can be provided. If an instantaneous phase current is received as a status signal, a specific threshold value can be assigned to a phase current, for example based on a predefined assignment, which is then determined by the adaptation unit 28. For example, the adaptation unit 28 can also additionally make use of previously known information.In particular, a saturation current of one of the two parallel switches can be taken into account. If the saturation current is lower, a threshold value can be lowered if necessary to still detect a bridge short circuit when the power semiconductor is operated at a comparatively low phase current.

[0031] The output interface 30 is designed to output an error signal. In particular, a comparison is performed between the voltage signal and the threshold value in the output interface 30. If the threshold value is exceeded, the error signal is output. An error signal is understood to be any type of output signal. For example, a shutdown of the phase current or the current through the relevant power semiconductor can also be directly triggered via the output interface 30.

[0032] The bypass switch 32 serves to switch a bypass of an electronic component in a supply line of the voltage interface 24. In particular, it is possible to bypass a Zener diode. By switching the bypass, the voltage level on the supply line to the voltage interface 24 can be adjusted. Thus, if an identical voltage drop occurs across one of the two parallel switches at the voltage interface 24, a different value will be received due to the bypass. The threshold value can therefore be changed by switching the bypass on or off. A transistor, for example, can be used for the bypass switch 32.

[0033] In other words, the device 22 according to the invention can be integrated into a conventional DESAT detection unit of a gate driver through integrated functionality. For this purpose, for example, an adaptation of the gate driver's software can be provided. Alternatively, the inventive approach can also be implemented in the form of external circuitry using the switch. A conventional gate driver can thus be expanded to include the inventive functionality of a variable DESAT threshold.

[0034] In this context, Fig. 3 a typical DESAT circuit and in Fig. 4 shows a modified DESAT circuit. It is possible to influence the threshold value by wiring the DESAT network and thus modify it during runtime. Fig. 4, the bypass switch M3 short-circuits the built-in Zener diode D8. By switching on the bypass switch M3, the voltage drop caused by the Zener diode D8 can be bridged. The conventional DESAT detection threshold in the driver IC remains constant, but the threshold value is reached at different drain-source voltages or at different collector-emitter voltages. When the Zener diode is switched on, a lower drain-source voltage or collector-emitter voltage is sufficient to trigger the detection, whereas with the Zener diode bypassed, a higher drain-source voltage or collector-emitter voltage is required. The voltage drop caused by the Zener diode D8 can also be caused by other means (e.g., resistively, by diodes, etc.) or bridged by other means.The bypass switch can be controlled by a separate component or by a corresponding implementation in software starting from the driver IC.

[0035] In Fig. Figure 5 schematically illustrates a method according to the invention for detecting a bridge short circuit. The method comprises steps of receiving S10 a voltage signal, receiving S12 a status signal, determining S14 a threshold value, and outputting S16 an error signal. The method can be implemented, for example, in software executed on a gate driver semiconductor chip. Likewise, the method can be executed on an externally arranged microcontroller that is in communication with a corresponding circuit or gate driver.

[0036] The invention has been comprehensively described and explained with reference to the drawings and the description. The description and explanation are to be understood as exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other embodiments or variations will become apparent to those skilled in the art upon use of the present invention and upon careful analysis of the drawings, the disclosure, and the following claims.

[0037] In the claims, the words "comprising" and "having" do not exclude the presence of further elements or steps. The undefined article "a" or "an" does not exclude the presence of a plurality. A single element or unit can perform the functions of several of the units recited in the claims. An element, unit, interface, device, and system can be partially or completely implemented in hardware and / or software. The mere mention of some measures in several different dependent claims should not be understood to mean that a combination of these measures cannot also be used advantageously. Reference signs in the claims are not to be understood as limiting. Reference symbol 10 vehicles 12 traction inverters 14 Battery 16 electric motors 18 power semiconductor module 20a, 20b Parallel switches 22 Device 24 voltage interface 26 Status interface 28 Adjustment unit 30 Output interface 32, M3 bridging switch QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 214 607 A1

[0005] Cited non-patent literature

[0000] Texas Instruments, “UCC5880-Q1 isolated 20-A adjustable gate drive IGBT / SiC MOSFET gate driver with advanced protection features for automotive applications

[0004]

Claims

[1] Device (22) for detecting a bridge short circuit in a power semiconductor module (18) with two parallel switches (20a, 20b) of different technology, comprising: a voltage interface (24) for receiving a voltage signal with information about a voltage drop across a switch of the two parallel switches; a status interface (26) for receiving a status signal with information on a current operating state of the power semiconductor module; an adaptation unit (28) for determining a threshold value for a voltage drop in the event of a bridge short circuit based on the status signal; and an output interface (30) for outputting an error signal based on the voltage signal and the threshold value when the voltage drop across the two parallel switches exceeds the determined threshold value. [2] The device according to claim 1, wherein the status interface is configured to receive a status signal with information about an instantaneous phase current through the power semiconductor module. [3] Device (22) according to claim 2, wherein the adaptation unit (28) is designed to entrain the threshold value with the instantaneous phase current. [4] Device (22) according to one of the preceding claims, wherein the adaptation unit (28) is designed to determine the threshold value based on a previously known saturation current of one of the two parallel switches (20a, 20b), in particular based on a comparison of the instantaneous phase current with the saturation current of the switch of the two parallel switches with the lower saturation current. [5] Device (22) according to one of the preceding claims, wherein the adaptation unit (28) is designed to determine the threshold value based on a selection from a plurality of predefined threshold values, in particular based on a selection from a predefined upper threshold value and a predefined lower threshold value. [6] Device (22) according to one of the preceding claims, wherein the output interface (30) is designed to interrupt a current flow through the two parallel switches (20a, 20b) when the voltage drop across the two parallel switches exceeds the determined threshold value. [7] Device (22) according to one of the preceding claims, with a bridging switch (32) for switching a bridging of an electronic component in a supply line of the voltage interface (24), in particular a Zener diode, wherein the adaptation unit (28) is designed to determine the threshold value based on a selection from a predefined upper threshold value and a predefined lower threshold value; and the switch is designed to bypass the electronic component when the upper threshold value has been determined. [8] Gate driver for a power semiconductor comprising a device (22) according to any one of the preceding claims. [9] Traction converter (12) for a vehicle (10), comprising: a power semiconductor module (18) for converting a direct voltage of a battery into an alternating voltage for an electric motor; and a device (22) according to any one of claims 1 to 7 or a gate driver according to claim 8. [10] Method for detecting a bridge short circuit in a power semiconductor module (18) with two parallel switches (20a, 20b) of different technology, comprising the steps: Receiving (S10) a voltage signal with information on a voltage drop across a switch of the two parallel switches; Receiving (S12) a status signal with information on a current operating state of the power semiconductor module; Determining (S14) a threshold value for a voltage drop in the event of a bridge short circuit based on the status signal; and Outputting (S16) an error signal based on the voltage signal and the threshold value if the voltage drop across the two parallel switches exceeds the determined threshold value. [11] A computer program product comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method according to claim 10.

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