Circuit arrangement and method for controlling a power switch

Abstract

Circuit arrangement (1) for controlling a power semiconductor switch (30, 32), wherein the switch has a load current input (300), a load current output (302) and a control input (304), with a switchable first voltage detection device (4) for detecting a first voltage (400) applied between the load current input (300) and the load current output (302), a second switchable voltage detection device (5) for detecting a second voltage (500) applied between the control input (304) and the load current output (302), and with a control device (6) configured to cyclically evaluate a second voltage value of the second voltage (500) and to switch on the first voltage detection device (4) when a second threshold value (502) of the second voltage value is reached, particularly if no further fault signal is present.

Description

[0001] The invention describes a circuit arrangement and a switching device therewith for controlling a power semiconductor switch, which has a load current input, a load current output, and a control input. The circuit arrangement comprises a first voltage detection device that can be switched on and off for detecting a first voltage present between the load current input and the load current output, and a second voltage detection device that can be switched on and off for detecting a second voltage present between the control input and the load current output. The invention further describes a method for using such a switching device.

[0002] DE 10 2022 104 700 A1 discloses circuits and techniques for protecting a circuit breaker when the circuit breaker is switched ON. A driver circuit can determine whether the circuit breaker is in a desaturation mode or an overcurrent condition based on a signal at a detection pin and deactivate the circuit breaker in response to determining that the circuit breaker is in the desaturation mode or overcurrent condition. Furthermore, the driver circuit can determine whether the circuit breaker is approaching a safe operating area (SOA) limit of the circuit breaker based on a rate of change of the signal and deactivate the circuit breaker in response to determining that the circuit breaker is approaching the SOA limit.

[0003] From daCunha, J. [et al.]: "A New Combined VGE and VCE Based Short-Circuit Detection for High-IC, desat HV-IGBTs and RC-IGBTs", in PCIM Europe 2018; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, Nuremberg, Germany, 2018, pages 1-8, an overcurrent detection for IGBT switches is known, which uses both the gate-emitter voltage VGE and the collector-emitter voltage VCE for detection. Delayed voltage monitoring, particularly for VCE, according to a predetermined "blanking time" (dead time) is a common measure to prevent erroneous detections and, in the case of cyclic switching operations, such as those found in IGBT-based DC / DC converters, also leads to cyclic activation and deactivation of the voltage monitoring.

[0004] From Hongyue, Z. [et al.]: "A self-adaptive blanking time circuit for fast IGBT desaturation short-circuit protection," in IEICE Electronics Express, Volume 17, Issue 11, 2020, pages 1-6, it is known that determining the blanking time and thus activating the collector-emitter voltage VCE monitoring can, in certain cases, advantageously be achieved dynamically by evaluating the gate-emitter voltage VGE and a corresponding control device. Thus, a self-adapting blanking time generation is presented.

[0005] The invention is based on the object of presenting both a method and a circuit arrangement which improves the protection of a circuit breaker, in particular during the switching-on process.

[0006] This object is achieved according to the invention by a circuit arrangement for controlling a power semiconductor switch, wherein the switch has a load current input, a load current output and a control input, with a first voltage detection device which can be switched on and off for detecting a first voltage applied between the load current input and the load current output, a second voltage detection device which can be switched on and off for detecting a second voltage applied between the control input and the load current output, and with a control device which is designed to cyclically evaluate a second voltage value of the second voltage and to switch on the first voltage detection device when a second threshold value of the second voltage value is reached, in particular if no further error signal is present.

[0007] In a preferred embodiment, a portion of the second voltage detection device is embodied as an integrated circuit, and this portion comprises a digitization device, in particular an analog / digital converter, that digitizes the second voltage value. It is further preferred if the control device is also arranged, at least partially, in the integrated circuit.

[0008] The object is further achieved according to the invention by a switching device with such a circuit arrangement and with a power switch which is designed as a power semiconductor component or as a group of parallel-connected power semiconductor components, wherein the respective power semiconductor component is designed as an IGBT or a MOS-FET, in particular as a SiC-MOS-FET.

[0009] It can be advantageous if two circuit breakers, each with an associated circuit arrangement, are arranged in a half-bridge topology.

[0010] The object is further achieved by a method for operating a circuit arrangement as part of a switching device, wherein during the switch-on process of the power semiconductor switch a second voltage value of the second voltage is determined by means of the second voltage detection device, this second voltage value is cyclically compared with a static or dynamic second threshold value and wherein upon reaching this second threshold value the first voltage detection device is switched on, in particular if no further error signal is present.

[0011] It may also be preferred if the second voltage detection device is switched on only after a static or dynamic first waiting time after the start of the switching-on process of the circuit breaker.

[0012] It may also be preferable for the first voltage detection device to be switched on only after a static or dynamic second waiting period after the second threshold value has been reached. It is advantageous if the second threshold value is between 90% and 98%, in particular between 92% and 95%, of a target value of the second voltage.

[0013] It may be particularly advantageous if, when the target value of the second voltage is exceeded by an excess value, the circuit breaker is switched to the non-conductive state by means of an output stage of the control device, and an error signal is generated. In this case, it may be particularly advantageous if the excess value is 5%, in particular 10%, above the target value of the second voltage. It may also be advantageous if the circuit breaker is switched to the non-conductive state after a static or dynamic third waiting time. The dynamic third waiting time may, in particular, depend on the second voltage value itself.

[0014] Of course, unless this is explicitly or per se excluded or contradicts the idea of ​​the invention, the features mentioned in the singular, in particular the second voltage detection device, can be present multiple times in the arrangement according to the invention.

[0015] It is understood that the various embodiments of the invention, regardless of whether they are mentioned in connection with the circuit arrangement or the switching device or with the methods, can be implemented individually or in any combination to achieve improvements. In particular, the features mentioned and explained above and below can be used not only in the specified combinations, but also in other combinations or on their own, without departing from the scope of the present invention.

[0016] Further explanations of the invention, advantageous details and features, emerge from the following description of the Fig. 1 to 3 schematically illustrated embodiments of the invention, or of respective parts thereof. Fig. 1 shows a switching device according to the invention with a circuit arrangement according to the invention. Fig. 2 shows voltage curves when applying an embodiment of the method according to the invention. Fig. 3 shows voltage curves when applying a further embodiment of the method according to the invention.

[0017] Fig. 1 shows a switching device 10 according to the invention with a circuit arrangement 1 according to the invention. The switching device 10 comprises a conventional half-bridge circuit of two power switches 30, 32, each with a load current input 300, a load current output 302, and a control input 304. The first, upper power switch 30 is connected by its load current input 300 to a first DC voltage terminal 80 of positive polarity, while the second, lower power switch 32 is connected by its load current output 302 to a second DC voltage terminal 82 of negative polarity. The center tap between the two power switches 30, 32 forms the AC voltage terminal 84.

[0018] Each of these power switches 30, 32 is designed in a conventional manner. Purely by way of example, the respective power switch 30, 32 can be designed as an IGBT 34, with an antiparallel-connected freewheeling diode, or as a power MOSFET 36, constructed using either silicon or silicon carbide technology. Likewise, the respective power switch 30, 32 can be a parallel connection of the aforementioned components. In the case of an IGBT 34, the collector terminal 340 forms the load current input 300, while the emitter terminal 342 forms the load current output 302. In the case of a MOSFET 36, the drain terminal 360 forms the load current input 300, while the source terminal 362 forms the load current output 302. The respective gate terminal 344, 364 forms the control input 304.

[0019] The circuit arrangement 1 comprises a first voltage detection device 4, which has a first voltage detection element 42 and an evaluation circuit 40, which is embodied here in the form of an integrated circuit. The voltage detection element 42 detects the voltage drop across the power switch 30 between its load current input 300 and its load current output 302. The evaluation circuit 40, and thus the integrated circuit, further forms part of a control circuit for the power switch 30. The entire first voltage detection device 4, depending on switching commands for the associated power switch 30 and possibly other parameters, can be switched on and off, i.e., activated and deactivated. Such first voltage detection devices 4 are also known as so-called "VCE monitoring circuits" from the prior art.

[0020] The illustrated circuit arrangement 1 also has a second voltage detection device 5, which has a second voltage detection element 52 and an evaluation circuit 50, which here is also designed in the form of an integrated circuit. The second voltage detection element 52 detects the voltage drop across the power switch 30 between its control input 304 and its load current output 302. The evaluation circuit, and thus the integrated circuit, also forms part of the control circuit of the power switch 30. The entire second voltage detection device 5 is also designed to be switched on and off, i.e., activatable and deactivatable.

[0021] The circuit arrangement 1 further comprises a control device 6 which, cf. Fig. 2 and Fig. 3, is designed to cyclically evaluate a second voltage value of the second voltage 500 and, upon reaching a second threshold value 502 of the second voltage 500, to switch on the first voltage detection device 4, particularly if no further error signal is present. The switching itself is performed by means of the conventional output stage 7, which is designed to apply the voltage required for switching on or off to the control input 304 of the power switch 30. Advantageously, various components, in particular the two evaluation circuits 40, 50 and the control device 6, are part of a common integrated circuit.

[0022] Fig. Figure 2 shows voltage curves when applying an embodiment of the method according to the invention. Shown is the curve of the first voltage 400 during the switch-on process of a circuit breaker 30, for example according to Fig. 1. Also shown is the curve of the second voltage 500 during the power-on process. The lower part of the figure shows the entire range that the second voltage 500 can assume between the control input 300 and the load current output 302, here from -7 V to +15 V, while the upper part of the figure only shows a section for voltages between +9 V and +15 V. The respective time curve is, of course, identical above and below.

[0023] The respective voltage curves are temperature-dependent at least to the extent that as the temperature of the circuit breaker 30 increases, the respective course of the voltage curves is extended for longer periods.

[0024] Shown is the voltage curve of the first voltage 400, which after a first period of time, which depends, among other things, on the temperature of the circuit breaker 30, drops below an assigned first threshold value 402. In some applications, it is customary to only switch the first voltage detection device 4 on, i.e., to activate it, as soon as the value of the first voltage 400 is below this first threshold value 402. In this case, it is customary to set a fixed, customary waiting time during which the value of the first voltage 400 is reliably below this first threshold value 402. In the time window from the start of the switch-on process until the value safely falls below the first threshold value 402, no check for overload, in particular for short circuits, of the circuit breaker 30 takes place.

[0025] It is also preferred to be able to dynamically configure the waiting time until the first voltage detection device 4 is activated in a simple manner. According to the invention, the second voltage detection device 5 serves for this purpose. This is switched on, i.e., active, after a first waiting time T1, which is significantly shorter than the usual waiting time. After the second voltage detection device 5 is activated, the second voltage 500 is monitored, and after the period T4 and upon reaching a second threshold value 502, which in this case is 600 mV below the target value 504 of the second voltage 500 of +15 V, the first voltage detection device 4 is switched on. It can be advantageous to provide a second waiting time T2 before the active switching, although this should be as short as possible in order to be able to activate the first voltage detection device 4 at the earliest reasonable time.This first voltage detection device 4 is then active for a period T5 until switching off of the circuit breaker 30 is initiated.

[0026] In the simplest case, the respective waiting times T1, T2 can be selected statically, i.e., always covering the same period of time. However, it is preferable to select the respective waiting times T1, T2 dynamically, with the temperature of the circuit breaker 30 being added as a correction factor to a fixed waiting time, purely as an example.

[0027] Fig. Figure 3 shows voltage curves when applying a further embodiment of the method according to the invention. The representation is basically the same as in Fig. 2.

[0028] However, the second voltage detection device 5 determines a voltage value of the second voltage 500 of more than +15.4 V. Exceeding this excess value 506 results from a short circuit in the bridge circuit and is therefore interpreted as an error, preferably by means of the control device 6, and an error signal is generated. This error signal then causes the control device 1 to close the power switch 30 by means of the output stage 7, see FIG. Fig. 2, switches to the non-conductive state. This switching operation only occurs once, after the time interval T6, the second voltage 500 has fallen below the excess value 506. Furthermore, this switching operation is preferably only executed after the expiration of a further third waiting time T3. This third waiting time T3, like the first and second waiting times, can be determined statically, but preferably dynamically.

[0029] Also shown is the temporal profile of current 410 through circuit breaker 30 and its decay after switching off. The dashed line shows the profile of current 420 if only a first voltage detection device 4 had been present and this had switched circuit breaker 30 to the non-conductive state later than if the second voltage detection device 5 had been present.

Claims

[1] Circuit arrangement (1) for controlling a power semiconductor switch (30, 32), said switch having a load current input (300), a load current output (302) and a control input (304), with a first voltage detection device (4) which can be switched on and off and is used to detect a first voltage (400) present between the load current input (300) and the load current output (302), with a second voltage detection device (5) which can be switched on and off and is used to detect a second voltage (500) present between the control input (304) and the load current output (302), and with a control device (6) which is designed to cyclically evaluate a second voltage value of the second voltage (500) and to switch on the first voltage detection device (4) when a second threshold value (502) of the second voltage value is reached, in particular if no further error signal is present. [2] Circuit arrangement according to claim 1, wherein a part of the second voltage detection device (5) is designed as an integrated circuit and this part has a digitization device, in particular an analog / digital converter, which digitizes the second voltage value. [3] Circuit arrangement 10 according to claim 2, wherein the control device (6) is also arranged, at least partially, in the integrated circuit. [4] Switching device with a circuit arrangement (1) according to one of the preceding claims and with a power switch (30, 32) which is designed as a power semiconductor component or as a group of parallel-connected power semiconductor components, wherein the respective power semiconductor component is designed as an IGBT (34) or a MOS-FET (36), in particular as a SiC-MOS-FET. [5] Switching device according to claim 4, wherein two power switches (30, 32) are arranged, each with an associated circuit arrangement (1), in half-bridge topology. [6] Method for operating a circuit arrangement according to one of claims 1 to 3 as part of a switching device according to one of claims 4 or 5, wherein during the switch-on process of the power semiconductor switch (30, 32) a second voltage value of the second voltage (500) is determined by means of the second voltage detection device (5), this second voltage value is cyclically compared with a second static or dynamic threshold value (502) and wherein when this second threshold value (502) is reached the first voltage detection device (4) is switched on, in particular if no further error signal is present. [7] Method according to claim 6, wherein the second voltage detection device (5) is switched on only after a static or dynamic first waiting time (T1) after the start of the switching-on process of the circuit breaker (30, 32). [8] Method according to claim 6 or 7, wherein the first voltage detection device (4) is switched on only after a static or dynamic second waiting time (T2) after reaching the second threshold value (502). [9] Method according to one of claims 6 to 8, wherein the second threshold value (502) is between 90% and 98%, in particular between 92% and 95% of a target value (504) of the second voltage (500). [10] Method according to one of claims 6 to 9, wherein the power switch (30, 32), when the target value (504) of the second voltage (500) is exceeded by an excess value (506), is switched to the non-conductive state by means of an output stage (7) of the control device (1) and an error signal is generated. [11] Method according to claim 10, wherein the excess value (506) is 5%, in particular 10%, above the target value (504) of the second voltage (500). [12] Method according to claim 10 or 11, wherein the switching of the power switch (30, 32) into the non-conductive state occurs after a static or dynamic third waiting time (T3).

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