Method and device for short-circuit detection by saturation detection in power semiconductor switches

Abstract

The present invention relates to a method for short-circuit detection by saturation detection in a power semiconductor switch and a corresponding device. VDD ) to provide a reference voltage (U ref ). The voltage drop in the load path caused by the power semiconductor switch (U Δ ) and the reference voltage (U ref ) to generate a voltage difference (U diff ). The resulting voltage difference (U diff ) with a predetermined limit voltage (U lim ) is compared. If the voltage difference (U diff ) exceeds the limit voltage (U lim ), a short-circuit current in the load path of the power semiconductor switch is detected and in this case the power semiconductor switch is switched off.

Description

Technical Field

[0001] The invention relates to a method and a device for short-circuit detection by saturation detection in power semiconductor switches. Background Art

[0002] Power electronic circuits usually have power semiconductors that operate as switches (power semiconductor switches). These power semiconductor switches are mostly metal oxide semiconductor field effect transistors (MOSFETs) or bipolar transistors with an insulated gate electrode (insulated gate bipolar transistors, IGBTs). For the vast majority of applications, these MOSFETs and IGBTs are based on silicon (Si).

[0003] In many applications, especially for higher powers and series circuits of power semiconductor switches (e.g. as a half-bridge), the power semiconductor switches must be protected from short-circuit currents, in particular half-bridge short-circuits. To this end, the load current of the power semiconductor switch is measured directly or indirectly, and when the permissible operating range is exceeded, the power semiconductor switch is disconnected independently of its normal control signal, thereby interrupting the short-circuit current. Short-circuit detection must be performed relatively quickly, because power semiconductor switches have only limited short-circuit stability due to their low thermal inertia. The short-circuit stability is usually indicated as the permissible short-circuit duration. For industrial applications, this is approximately 10 μs [microseconds] and for vehicle traction inverters approximately 3 μs. The short-circuit current cut-off process lasts approximately 1-2 μs. Therefore, short-circuit detection in vehicle traction inverters must be performed within approximately 1-2 μs.

[0004] There are two main known methods for short circuit detection:

[0005] -I-Sense

[0006] -Desat (desaturation detection, in IGBT) or Sat (saturation detection, in MOSFET)

[0007] In order to avoid the expensive measurement of the load current of the power semiconductor switch, the (De)Sat detection is intended to indirectly measure the voltage drop in the load path of the power semiconductor switch (IGBT: collector-emitter voltage, MOSFET: drain-source voltage).

[0008] In the switched-on state, in normal operation, the voltage drop across the power semiconductor switch should be as small as possible in order to minimize the conduction losses. For example, in a 500 V application, a common voltage drop is approximately 1-3 V [volts]. The short-circuit current is mostly many times the normal operating current and therefore leads to a significantly higher voltage drop across the power semiconductor switch. In the event of a short circuit, the power semiconductor switch often limits the short-circuit current itself, since the normal operating range in the on state (e.g. MOSFET: ohmic range) is left. In this case, the IGBT desaturates and the MOSFET saturates. Therefore, the names of these short-circuit detection methods can also be used: "Desat" (IGBT) for "desaturation detection" and "Sat" (MOSFET) for "saturation detection".

[0009] Since the voltage drop across the power semiconductor switch in the switched-off state is significantly higher than in the switched-on state (e.g. 500 V to 1.5 V) and short-circuit detection should be performed quickly despite the steep switching process, the voltage drop is not measured directly via a high-resistance voltage divider (plus filter and measuring amplifier). Instead, an indirect measurement using a decoupling diode is used.

[0010] In order to measure the voltage drop across the power semiconductor switch in the on state, a (smaller) (auxiliary) current is fed into the power path of the power semiconductor via the decoupling diode. This (auxiliary) current is fed from the positive (gate driver) supply voltage, i.e. the supply voltage of the power semiconductor switch, by means of a pull-up resistor or a supply circuit. The voltage drop at the anode of the decoupling diode now corresponds to the voltage drop across the power semiconductor switch plus the forward voltage of the decoupling diode. The measurement signal can additionally be filtered and evaluated by means of a comparator circuit.

[0011] If the voltage drop across the power semiconductor switch exceeds a previously defined limit value, a short-circuit current is detected and a corresponding shutdown process is initiated.

[0012] In the switched-off state, the voltage across the power semiconductor switch drops to a value greater than the (gate driver) supply voltage. The decoupling diode is therefore switched off. Short-circuit monitoring is therefore not possible (but not required) in the switched-off state. In order to prevent the input filter from being charged via the pull-up resistor, a clamping transistor connected to ground is activated in the switched-off state.

[0013] The described form of short-circuit detection represents the most common short-circuit detection method and is already integrated in many commercially available gate driver integrated circuits, so that only a decoupling diode and an analog (RC) filter are required as external wiring structures.

[0014] DE 10 2016 212 211 A1 describes a short circuit detection. A device for disconnecting a bipolar transistor having a collector connection, an emitter connection and a gate connection is disclosed. The device comprises: a voltage detection unit for detecting a gate-emitter voltage dropping between the gate connection and the emitter connection; a comparison unit connected to the voltage detection unit for comparing the gate-emitter voltage with a predetermined threshold value, wherein the comparison unit provides a trigger signal on the output side when the gate-emitter voltage is greater than the threshold value; a switch state detection unit (19) for detecting a load current flowing from the collector connection to the emitter connection, wherein the switch state detection unit provides a load current signal on the output side when the load current is detected; and a control unit connected to the switch state detection unit and the comparison unit, wherein the control unit generates a disconnection signal for disconnecting the bipolar transistor when receiving the load current signal and the trigger signal. Summary of the invention

[0015] The present invention provides a method according to the present invention for short circuit detection by saturation detection in the power semiconductor switch and a corresponding device according to the present invention. Designs and improvements of the present invention are embodied in the subject matter described in other parts of the disclosure.

[0016] The triggering threshold of the comparator circuit is generally fixedly preconfigured for integrated (De)Sat detection integrated in a gate driver integrated circuit or can be configured from the primary side. Since the indirect measurement of the voltage drop across the power semiconductor is based on the current flow from the (gate driver) supply voltage via the decoupling diode and the power semiconductor, voltage drops across the power semiconductor that are greater than the (gate driver) supply voltage cannot be measured.

[0017] The (gate driver) supply voltage varies due to tolerances and errors. Typical values ​​can be:

[0018] -Typical power supply: 18V

[0019] -Typical tolerance: ±1V

[0020] - Voltage in error condition: 10V..20V

[0021] Since the short-circuit detection is a safety-related function, it must operate over the entire supply voltage range (that is to say also in the case of supply voltage tolerances). The triggering threshold of the short-circuit detection must be selected in such a way that the normal operating current is not detected as a short circuit and is switched off. This results in a minimum permissible triggering threshold (voltage drop across the power semiconductor). It depends on the application and the type and design of the power semiconductor. Typical values ​​for the minimum triggering threshold can be approximately 3 V in the case of IGBT applications and can be 10 V..15 V when using wide bandgap power semiconductors. Short-circuit detection below the minimum triggering threshold must only be ensured within a limited range of the supply voltage, for example within the nominal supply voltage range (supply without tolerances).

[0022] The invention tracks the trigger threshold as a function of the supply voltage. In particular, the invention also enables short-circuit detection for large supply voltage ranges, high minimum trigger thresholds and / or wide-bandgap power semiconductors (SiC, GaN, etc.).

[0023] According to a first aspect of the present invention, a method for short-circuit detection by saturation detection in a power semiconductor switch comprises the following steps: providing a reference voltage U ref , generate voltage difference U diff , the voltage difference U diff With the predetermined limit voltage U lim The comparison is performed and the power semiconductor switch is turned off. ref In the step, according to the supply voltage U of the power semiconductor switch VDD To provide the reference voltage U ref , so that the reference voltage U ref Follow supply voltage U VDD The voltage difference U diff In the step, the voltage difference U diff The voltage drop U corresponding to the load path of the power semiconductor switch Δ With the provided reference voltage U ref The voltage difference U diff With the predetermined limit voltage U lim In the comparison step, if the voltage difference U diff Exceeding the limit voltage U lim , a short-circuit current in the load path of the power semiconductor switch is detected. In the step of disconnecting the power semiconductor switch, if a short-circuit current in the load path of the power semiconductor switch is identified, the power semiconductor switch is disconnected.

[0024] According to a second aspect of the invention, a device for short-circuit detection by saturation detection in a power semiconductor switch comprises at least one decoupling diode, a power supply, a reference voltage source, a comparator circuit and evaluation electronics. The at least one decoupling diode is designed to be electrically connected to a drain connection or a collector connection of the power semiconductor switch. The voltage drop U at the anode of the at least one decoupling diode is Δ The voltage drop U in the load path corresponding to the power semiconductor switch Δ The power supply is electrically connected to at least one decoupling diode. The power supply is configured to feed an auxiliary current into a load path of the power semiconductor switch when the at least one decoupling diode is electrically connected to a drain connection or a collector connection of the power semiconductor switch. The reference voltage source is configured to be electrically connected to a power supply source for the power semiconductor switch. The reference voltage source is further configured to determine the power supply voltage U of the power supply source according to the power supply voltage U of the power supply source. VDD To provide reference voltage U ref , so that the reference voltage U ref Follow supply voltage U VDD The comparator circuit is electrically connected to at least one decoupling diode and the reference voltage source. The comparator circuit is configured to generate a voltage difference U diff , which corresponds to the voltage drop U in the load path of the power semiconductor switch. Δ With the provided reference voltage U ref The evaluation electronics are designed to convert the resulting voltage difference U diff With the predetermined limit voltage U lim If the voltage difference U diff Exceeding the limit voltage U lim , a short-circuit current in the load path of the power semiconductor switch is detected. Furthermore, the evaluation electronics are designed to disconnect the power semiconductor switch when a short-circuit current in the load path of the power semiconductor switch is detected.

[0025] The reference voltage U ref The supply voltage U VDD coupling so that the supply voltage U VDD In case of rising or falling reference voltage U ref The reference voltage U ref With supply voltage U VDD This coupling can be performed by an analog circuit so that the reference voltage U ref Variation of supply voltage U VDD This is done highly dynamically (essentially without time lag). refTracking supply voltage U VDD For example, the power supply can provide a supply voltage U of 18V. VDD of current.

[0026] The voltage drop U generated in the load path of the power semiconductor Δ With the reference voltage U ref The voltage difference U diff (U diff =U Δ -U ref ) and compare it with the predetermined limit voltage U lim The predetermined limit voltage U is thus selected. lim , so that it corresponds to the voltage which occurs at least in the case of a short circuit, for example U lim =10V..20V. Therefore, if the voltage drop U in the load path of the power semiconductor Δ Due to short circuit, the normal operating range (such as 17V..19V) is exceeded (such as U Δ =40V), then the voltage difference U diff The same increase (for example, U diff =U Δ -U ref =40V-18V=12V). Therefore, the voltage difference U diff Exceeding a predetermined limit voltage (such as U diff =10V) and detects a short circuit of the power semiconductor switch. ref Tracking, the voltage drop U Δ When it is very high, the triggering threshold for (De)Sat detection can also be detected or measured explicitly.

[0027] If the voltage difference U diff With the predetermined limit voltage U lim A comparison shows that the voltage difference U diff Equal to or greater than the predetermined limit voltage U lim , then a short circuit is detected and the power semiconductor switch is disconnected. diff With the predetermined limit voltage U lim The comparison of the power semiconductor switches and the disconnection of the power semiconductor switches when a short circuit is detected by the comparison can be performed by a (De)Sat detection implemented in an integrated circuit (IC). As an alternative, the described functionality can also be performed completely in a discrete (analog) circuit.

[0028] Because according to the present invention, the reference voltage U ref The triggering threshold of the (De)Sat detection is dependent on the supply voltage UVDD , thus achieving additional degrees of freedom in circuit design. As a result of this degree of freedom, a high minimum triggering threshold is achieved (within a restricted supply voltage range) and at the same time short-circuit detection can be guaranteed over the entire supply voltage range.

[0029] According to an improved solution of the present invention, the reference voltage U is provided between a Zener diode electrically connected to a power supply for the power semiconductor switch and a parallel circuit consisting of a first resistor and a first capacitor electrically connected to a ground line GND. ref .

[0030] According to another improved solution of the present invention, the reference voltage source comprises a Zener diode and a parallel circuit consisting of a first resistor and a first capacitor. The reference voltage U is provided between the Zener diode electrically connected to the power supply for the power semiconductor switch and the parallel circuit electrically connected to the ground line GND. ref .

[0031] This design of the reference voltage source provides a sufficiently accurate provision of the reference voltage U ref The result is a low-power (compared to e.g. a pure voltage divider) and is nevertheless cheap (compared to e.g. a precise reference).

[0032] According to a further development of the invention, a voltage drop U of the load path of the power semiconductor switch is tapped off at the anode of at least one decoupling diode. Δ The at least one decoupling diode is electrically connected to a drain connection or a collector connection of the power semiconductor switch. An auxiliary current from a power supply is fed to the at least one decoupling diode via a pull-up resistor.

[0033] The pull-up resistor allows the auxiliary current to be provided robustly and still be inexpensive.

[0034] According to a development of the invention, the device further comprises an input filter which is electrically connected in parallel with the power semiconductor switch.

[0035] The input filter improves the robustness of the circuit or application.

[0036] According to an improved solution of the present invention, the method further comprises a step of preventing charging of the input filter. In the step of preventing charging of the input filter, charging of the input filter electrically connected in parallel with the power semiconductor switch is prevented by a clamping transistor electrically connected in parallel with the input filter via a pull-up resistor in a switched-off state.

[0037] According to another development of the invention, the device further comprises a clamping transistor which is electrically connected in parallel with the input filter and which is designed to prevent the input filter from being charged via the pull-up resistor in the switched-off state.

[0038] For this purpose, the clamping transistor is connected to ground (GND) in the switched-off state. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The invention and the technical field are explained in detail below with the aid of the drawings. It should be pointed out that the invention is not to be restricted to the embodiments shown. In particular, partial aspects of the facts illustrated in the drawings can also be extracted and combined with other components and insights from the present description and / or the drawings, unless otherwise explicitly described. In particular, it should be pointed out that the drawings and in particular the dimensional ratios shown are merely schematic. The same reference numerals denote the same objects, so that explanations from other drawings can be supplementarily taken into account if necessary. Among them:

[0040] Figure 1 A schematic flow chart of a method for short-circuit detection by saturation detection in a power semiconductor switch is shown;

[0041] Figure 2 A schematic circuit diagram of a device for short-circuit detection by saturation detection in a power semiconductor switch is shown;

[0042] Figure 3 Shows Figure 2 A schematic equivalent circuit diagram of a special embodiment of the device. DETAILED DESCRIPTION

[0043] exist Figure 1 The method for short-circuit detection by saturation detection in a power semiconductor switch is schematically shown in FIG. The method comprises the following steps: providing a reference voltage U ref , generate 2 voltage difference U diff , the voltage difference U diff With the predetermined limit voltage U lim Comparison 3 is performed; the power semiconductor switch is switched off 4 and charging of the input filter is optionally prevented 5. The steps of the method can be performed in any order and / or at least partially simultaneously.

[0044] Provides a reference voltage U ref In the step, according to the supply voltage U of the power semiconductor switch VDD To provide a reference voltage. The reference voltage U ref Here the supply voltage U VDDTo this end, the reference voltage U is provided or tapped between the Zener diode and the parallel circuit consisting of the first resistor and the first capacitor. ref The Zener diode is electrically connected to a power supply for a power semiconductor switch. The parallel circuit formed by the first resistor and the first capacitor is electrically connected to a ground line GND. The power supply provides a supply voltage U having 18V. VDD of current.

[0045] U ref ~U VDD

[0046] The voltage difference U diff In the step, the voltage difference U diff The voltage drop U in the load path corresponding to the power semiconductor switch Δ With the provided reference voltage U ref difference.

[0047] U diff =U Δ -U ref

[0048] The voltage drop U of the load path of the power semiconductor switch is tapped off at the anode of at least one decoupling diode. Δ The at least one decoupling diode is electrically connected to a drain connection or a collector connection of the power semiconductor switch. Here, an auxiliary current from a power supply is fed to the at least one decoupling diode via a pull-up resistor.

[0049] The voltage difference U diff With the predetermined limit voltage U lim In step 3 of comparison, the voltage difference U diff With the predetermined limit voltage U lim Here, the limit voltage U lim is 10V to 20V. Here, if the voltage difference U diff Reach or exceed the limit voltage U lim , then the short-circuit current in the load path of the power semiconductor switch is detected.

[0050] U diff ≥U lim

[0051] In the step of turning off the power semiconductor switch, if a short-circuit current is detected in a load path of the power semiconductor switch, the power semiconductor switch is turned off.

[0052] Furthermore, in the optional step of preventing 5 charging of the input filter, the input filter is prevented from being charged in the disconnected state via a pull-up resistor. The input filter is electrically connected in parallel with the power semiconductor switch. Through the pull-up resistor, the input filter can be charged in the disconnected state. This is prevented by a clamping transistor electrically connected in parallel with the input filter.

[0053] exist Figure 2 The device 10 (short-circuit detection circuit) for short-circuit detection by saturation detection in a power semiconductor switch is schematically shown in FIG. Figure 1 method.

[0054] The device 10 comprises the following components:

[0055] a decoupling diode 11 to a drain connection 21 of a power semiconductor 20 (or alternatively to a collector connection (not shown) of a power semiconductor 20 );

[0056] - a power supply 12 (in the form of a pull-up resistor, not shown);

[0057] - Depends on the supply voltage U of the power semiconductor 20 VDD A reference voltage source 13;

[0058] - a comparator circuit 14;

[0059] -Evaluation electronic device 15;

[0060] - a clamping transistor 16; and

[0061] - Output wiring structure 17.

[0062] The decoupling diode 11 is electrically connected (with its anode) to the power source 12 and is also electrically connected in the flow direction (with its cathode) to the drain terminal 21 of the power semiconductor switch 20. The voltage drop U across the load path of the power semiconductor switch 20 is tapped off at the anode of the decoupling diode 11. Δ Here, the power supply 12 is supplied from the supply voltage U VDD An auxiliary current is provided for the decoupling diode 11 in order to be able to measure or tap off the voltage drop U at the anode of the decoupling diode 11 . Δ .

[0063] The reference voltage source 13 provides a reference voltage U ref The reference voltage U ref The supply voltage U of the power supply source following the power semiconductor switch 20 VDD .

[0064] The decoupling diode 11 (with its anode) and the reference voltage source 13 are electrically connected to the comparator circuit 14 in such a way that the output of the comparator circuit 14 has a voltage difference U diff , where the voltage difference U diff The voltage drop U corresponding to the load path of the power semiconductor switch 20 Δ With reference voltage U ref difference.

[0065] The comparator circuit 14 is electrically connected with its output to an evaluation electronics system 15. The evaluation electronics system 15 is an integrated circuit (IC) here, which is able to implement a desaturation method. In this case, if the voltage difference U diff Equal to or greater than the predetermined limit voltage U lim , the power semiconductor switch 20 is opened by the evaluation electronics / IC 15. The predetermined limit voltage U lim , so that when the voltage difference U diff Reaching or exceeding a predetermined limit voltage U lim At this time, a short circuit exists in the power semiconductor switch 20 .

[0066] The clamping transistor 16 is electrically connected to the output of the comparator circuit 14 and the power supply 12. In this case, the clamping transistor 16 prevents the input filter of the device 10 from being charged via the pull-up resistor of the power supply 12 in the switched-off state.

[0067] Furthermore, an output wiring structure 17 is electrically connected to the output terminal of the comparator circuit 14. The output wiring structure is connected to the ground (GND).

[0068] The functions shown in the basic circuit diagram of device 10 can also be implemented in a (single) integrated circuit (IC) or completely in discrete (analog) circuits.

[0069] exist Figure 3 It is schematically shown in Figure 2 A special embodiment of the device 10. Figure 3 The device 10 in FIG. Figure 2 The difference in the device or special design.

[0070] The anode of the decoupling diode 11 is electrically connected via a pull-up resistor 19 to the power supply 12 , more precisely to the collector connection of a first PNP transistor 12 . 4 of the power supply 12 .

[0071] The power supply 12 includes a second resistor 12.1 and a fourth resistor 12.3, which are connected to the power semiconductor 20 to provide a supply voltage UVDD The power supply 12 is electrically connected to a power supply of the first resistor 12.1. In addition, the power supply 12 comprises a third resistor 12.2, which is electrically connected in series with the first resistor 12.1. In addition, the power supply 12 comprises a first PNP transistor 12.4, wherein the bulk connection (bulk-Anschluss) of the first PNP transistor 12.4 is electrically connected between the first resistor 12.1 and the second resistor 12.2, the emitter connection of the first PNP transistor 12.4 is electrically connected to the third resistor 12.3, and the collector connection of the first PNP transistor 12.4 is electrically connected to the anode of the decoupling diode 11 via a pull-up resistor 19. In addition, the collector connection of the first PNP transistor 12.4 is electrically connected to a third capacitor 18, wherein the third capacitor 18 is also connected to ground (GND).

[0072] The reference voltage source 13 comprises a Zener diode 13.1 and a parallel circuit consisting of a first resistor 13.2 and a first capacitor 13.3. The Zener diode is electrically connected (with its cathode) to the power supply of the power semiconductor switch 20. Furthermore, the Zener diode is electrically connected (with its anode) to the parallel circuit. Furthermore, the first resistor 13.2 and the first capacitor 13.3 of the parallel circuit are grounded (GND). Furthermore, the Zener diode 13.1 is electrically connected with its anode to the comparator circuit 14 (more precisely to the emitter connection of the NPN transistor 14.5 and to the anode of the first diode 14.6 of the comparator circuit 14).

[0073] The comparator circuit 14 comprises a second PNP transistor 14.1, which is electrically connected with its emitter connection to the power supply of the power semiconductor switch 20, with its collector connection to the fifth resistor 14.2 of the comparator circuit 14, and with its body connection to the sixth resistor 14.3 of the comparator circuit 14. In addition, the comparator circuit 14 comprises a first NPN transistor 14.5, which is electrically connected with its collector connection to the body connection of the second PNP transistor via the sixth resistor 14.3. In addition, the collector connection of the first NPN transistor 14.5 is electrically connected to the power supply of the power semiconductor switch 20 via the seventh resistor 14.4 of the comparator circuit 14. The emitter connection of the first NPN transistor 14.5 is electrically connected to the anode of the Zener diode 13.1 of the reference voltage source 13, the anode of the first diode 14.6 of the comparator circuit 14, and the third resistor 12.2 of the power supply 12. The body connection of the first NPN transistor 14.5 and the cathode of the first diode 14.6 are electrically connected to the cathode of the second diode 14.8 of the comparator circuit 14 and to the collector connection of the first PNP transistor 12.4 of the power supply via an eighth resistor 14.7 of the comparator circuit or additionally to the anode of the decoupling diode 11 via a pull-up resistor 19. The collector connection of the second PNP transistor is electrically connected to the evaluation electronics 15 via a fifth resistor 14.2.

[0074] The clamping transistor 16 is an N-channel insulated layer field effect transistor, which is connected with its gate terminal to ground (GND) and is electrically connected with its source terminal and its gate terminal to the collector terminal of the second PNP transistor 14.1 of the comparator circuit 14 and the evaluation electronics 15 on the one hand, and is electrically connected with its drain terminal to the collector terminal of the first PNP transistor 12.4 of the power supply 12 on the other hand, and is electrically connected via a pull-up resistor 19 to the anode of the decoupling diode 11.

[0075] The output wiring structure 17 here comprises a parallel circuit consisting of a ninth resistor 17.1 and a second capacitor 17.2, which are electrically connected on the one hand to ground (GND) and on the other hand to the collector connection of the second PNP transistor 14.1 (via the fifth resistor 14.2), the evaluation electronics 15 and the source connection and the gate connection of the N-channel field effect transistor 16.

[0076] Although specific embodiments have been illustrated and described herein, it is clear to those skilled in the art that there are many alternatives and / or equivalent implementations. It should be understood that the exemplary designs or embodiments are merely examples and are not intended to limit the scope, applicability, or configuration in some way. On the contrary, the foregoing overview and detailed description provide sufficient guidance for those skilled in the art to implement at least one preferred embodiment, wherein it is self-evident that the various changes in the functions and arrangements of the elements described in the exemplary designs do not depart from the scope of application set forth in the attached claims and their legal equivalents. In general, the present application is contemplated to cover any adjustments or changes to the specific embodiments discussed herein.

[0077] In the above detailed description, various features are summarized in one or more examples to make the disclosure concise. It goes without saying that the above description should be used as an illustration and not a restriction. It should cover all alternatives, modifications and equivalents that can be included within the scope of the present invention. When studying the above disclosure, many other examples will be obvious to those skilled in the art.

[0078] In order to provide a comprehensive understanding of the present invention, specific terminology used in the foregoing disclosure is used. However, it will be apparent to one skilled in the art from the description contained to this point that the specific details are not required to practice the present invention. Therefore, the foregoing descriptions of specific embodiments of the present invention have been described for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise embodiments disclosed above; it is apparent that many modifications and variations are possible in light of the teachings set forth above.

[0079] The embodiments are selected and described to best explain the principles of the invention and its practical application and thereby enable other technical personnel in the art to best use the invention and various embodiments with various modifications, if this is appropriate for the corresponding use. Throughout the specification, the concepts "including" and "wherein" are used as equivalent concepts of the corresponding concepts "including" and "wherein", respectively. In addition, the concepts "first", "second", "third", etc. are only used as identifiers and are not intended to be used to make numerical requirements on objects or to predetermine a specific order. In conjunction with this specification and the claims, the conjunction "or" should be understood as inclusive ("and / or") and not exclusive ("either...or").

Claims

1. A method for short-circuit detection by saturation detection in a power semiconductor switch, the method comprising the following steps: - According to the supply voltage (U VDD ) to provide the reference voltage (U ref ), so that the reference voltage (U ref ) follows the supply voltage (U VDD ) in the - Produce (2) voltage difference (U diff ), the voltage difference corresponds to the voltage drop (U Δ ) and the reference voltage (U ref ) difference; - The resulting voltage difference (U diff ) and the predetermined limit voltage (U lim ) is compared (3), wherein if the voltage difference (U diff ) exceeds the limit voltage (U lim ), a short-circuit current in a load path of the power semiconductor switch (20) is detected; and - disconnecting (4) the power semiconductor switch (20) if a short-circuit current is detected in the load path of the power semiconductor switch (20), characterized in that the reference voltage (U) is provided between a Zener diode (13.1) electrically connected to a power supply source for the power semiconductor switch (20) and a parallel circuit consisting of a first resistor (13.2) and a first capacitor (13.3) electrically connected to a ground line (GND) ref ).

2. The method according to claim 1, wherein a voltage drop (U Δ ), the at least one decoupling diode being electrically connected to a drain connection or a collector connection of the power semiconductor switch (20), wherein an auxiliary current from a power supply (12) is fed to the at least one decoupling diode (11) via a pull-up resistor (19).

3. The method according to claim 2, further comprising the following steps: In the switched-off state, the pull-up resistor (19) prevents (5) the input filter from being charged by means of a clamping transistor (16) which is electrically connected in parallel with the input filter, which is electrically connected in parallel with the power semiconductor switch (20).

4. A device (10) for short circuit detection by saturation detection in a power semiconductor switch, comprising: at least one decoupling diode (11) which is designed to be electrically connected to a drain terminal (21) or a collector terminal of a power semiconductor switch (20), wherein a voltage drop (U Δ ) corresponds to a voltage drop (U Δ ); a power supply (12) which is electrically connected to the at least one decoupling diode (11) and is designed to feed an auxiliary current into a load path of the power semiconductor switch (20) when the at least one decoupling diode (11) is electrically connected to a drain terminal or a collector terminal of the power semiconductor switch (20); a reference voltage source (13) which is designed to be electrically connected to a power supply source for the power semiconductor switch (20) and to generate a reference voltage according to a supply voltage (U VDD ) to provide a reference voltage (U ref ), so that the reference voltage (U ref ) follows the supply voltage (U VDD ) changes; a comparator circuit (14) which is electrically connected to the at least one decoupling diode (11) and the reference voltage source (13) and is designed to generate a voltage difference (U diff ), the voltage difference corresponds to the voltage drop (U Δ ) and the reference voltage (U ref ) difference; as well as - an evaluation electronics system (15) which is designed to convert the generated voltage difference (U diff ) and the predetermined limit voltage (U lim ) is compared, where if the voltage difference (U diff ) exceeds the limit voltage (U lim ), a short-circuit current in a load path of the power semiconductor switch (20) is detected, and if a short-circuit current in the load path of the power semiconductor switch (20) is detected, the power semiconductor switch (20) is disconnected, characterized in that the reference voltage (U) is provided between a Zener diode (13.1) electrically connected to a power supply for the power semiconductor switch (20) and a parallel circuit consisting of a first resistor (13.2) and a first capacitor (13.3) electrically connected to a ground line (GND). ref ).

5. The device (10) according to claim 4, wherein the reference voltage source (13) comprises a Zener diode (13.1) and a parallel circuit consisting of a first resistor (13.2) and a first capacitor (13.3), wherein the reference voltage (U ) is provided between the Zener diode (13.1) electrically connected to the power supply for the power semiconductor switch (20) and the parallel circuit electrically connected to the ground (GND). ref ).

6. The device (10) according to claim 4, wherein the auxiliary current is fed to the at least one decoupling diode (11) via a pull-up resistor (19).

7. The device (10) according to claim 6, further comprising an input filter electrically connected in parallel with the power semiconductor switch (20).

8. The device (10) according to claim 7, further comprising a clamping transistor (16) which is electrically connected in parallel with the input filter and is designed to prevent the input filter from being charged via the pull-up resistor (19) in the switched-off state.

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