Control device for semiconductor switch of an inverter and method for activating an inverter; active discharging of an hv circuit via timing pulses

Abstract

The invention relates to a control device (4a, 4d) for activating a semiconductor switch (1a, 1d) of an inverter (10). The control device comprises a processor (15a, 15d) which is configured to: receive information from a controller (50); and generate a driver signal (18k) on the basis of the information; wherein the driver signal controls the semiconductor switch, and wherein the driver signal has a series of driver signal pulses with a pulse length (T) such that the semiconductor switch is not completely conductive during activating by way of the control signal during the pulse length.

Description

[0001] Description

[0002] title

[0003] Control device for semiconductor switches of an inverter and method for controlling an inverter: Active discharge of a HV circuit via starting pulses

[0004] The invention relates to a control device for controlling a semiconductor switch of an inverter and a method for controlling an inverter.

[0005] State of the art

[0006] Electric and hybrid vehicles often have power electronic circuit components in the drive system between the traction battery and the electric motor, which are typically designed as voltage source converters. A DC link serves as a coupling element between the traction battery and an inverter, which can be controlled to transfer electrical power from the DC link to the electric motor.

[0007] Inverters can, for example, be designed as a full-bridge circuit with a number of bridge arms, each with two semiconductor switches. The semiconductor switches of the bridge arms connected to a first output terminal of the DC link can be referred to as high-side switches (HS switches), and the semiconductor switches of the bridge arms connected to the second output terminal of the DC link can be referred to as low-side switches (LS switches). Semiconductor switches can be, for example, IGBT modules (insulated-gate bipolar transistors) with an antiparallel diode or MOSFETs (metal-oxide field-effect transistors).

[0008] Control systems are used to control the inverter, generating switching signals for the semiconductor switches. In the event of a fault, various requirements are placed on the control systems for safety reasons. For example, it may be necessary to safely short-circuit the motor windings of the electric machine in the event of a fault. This can be achieved by closing all high-side switches and opening all low-side switches (or vice versa), which is also referred to as an "active short circuit."

[0009] Furthermore, in the event of a fault, it is necessary to discharge the DC link quickly and reliably. This can be achieved through rapid discharge. Such rapid discharge is required by standards within a maximum rapid discharge time of five seconds to ensure the electrical operational safety of the vehicle.

[0010] The discharge of high-current circuits can be carried out via a discharge resistor (bleeding resistor) or the HV output stage (B6 bridge, full-bridge circuit). Discharge via the HV output stage (B6 bridge) can be achieved by permanently switching on one or more low-side (LS) switches and clocking a high-side (HS) switch with special gate control. Discharge can also be achieved the other way around by permanently switching on an HS switch and clocking LS switches. The current flow from T+ to T- leads to power conversion in the switches of the HV output stage. The discharge current is highly sensitive to the pulse width of the clock pulses. Therefore, the pulse width has currently been generated via programmable logic on the low-voltage side. In order for the discharge to take place in the desired time without thermally destroying the HV output stage, the control of the clock pulses must also be adjusted to the current operating point.The clock pulses of one or more HV switches (so-called gate switches) are correspondingly short and carried out with a small gate current so that the power loss of the HV output stage can be dissipated.The document DE 10 2011 089 316 A1 discloses a control device for controlling a semiconductor switch of an inverter, comprising a control circuit which is designed to generate a driver signal as a function of a switching signal generated by a control regulation of the inverter, and a driver circuit which is coupled between the control circuit and a control input of the semiconductor switch and which is designed to receive the driver signal and, as a function of the driver signal, to generate a control signal which controls the semiconductor switch and to feed it into the control input of the semiconductor switch, wherein the control circuit is designed to generate the driver signal as a sequence of driver signal pulses with a predetermined and adjustable pulse length, such that the semiconductor switch is not fully conductive during the pulse length when controlled with the control signal.

[0011] Disclosure of the invention

[0012] The invention provides a control device and a method having the features of the independent patent claims.

[0013] Preferred embodiments are the subject of the respective subclaims.

[0014] According to a first aspect, the invention relates to a control device for controlling a semiconductor switch of an inverter, wherein the control device comprises: a processor configured to: receive information from a control system; and generate a drive signal based on the information; wherein the drive signal controls the semiconductor switch, and wherein the drive signal comprises a sequence of drive signal pulses with a pulse length such that the semiconductor switch is not fully conductive during the pulse length when controlled with the control signal.

[0015] According to a further development, the information comprises one or more of the following: a command for an active discharge; a side on which the semiconductor switch is controlled; a pulse length of the drive signal pulses; a shape of the drive signal pulses; and a parameter for the gate current. The accuracy of the trigger pulses (gate current and pulse width) can be realized without jitter due to the elimination of NV-HV transmission.

[0016] According to a further development, the pulse length (T) can be adjusted such that the semiconductor switch has a predetermined current value when controlled with the control signal

[0017] According to a further development, the processor is further configured to: receive measurement information relating to the inverter; and send the measurement information to the control system.

[0018] According to a further development, the control device is configured to: couple to a current sensor output of the semiconductor switch; detect a second measurement signal for a current through the semiconductor switch; and generate the drive signal as a function of the second measurement signal.

[0019] According to a further development, the control device is designed to control an IGBT switch, SIC switch and / or MOSFET switch.

[0020] According to a further development, the inverter has a half-bridge circuit, and wherein the control circuit is designed to control one of the semiconductor switches of a half-bridge with the driver signal and to permanently close the other of the semiconductor switches of the half-bridge.

[0021] According to a second aspect, the invention relates to a drive system for an n-phase electrical machine, where n is greater than or equal to 1, comprising: an intermediate circuit capacitor connected to two input voltage terminals; an inverter having a plurality of semiconductor switches, which is coupled to the intermediate circuit capacitor, is supplied with electrical energy from the intermediate circuit capacitor, and is designed to generate an n-phase supply voltage for the electrical machine; a plurality of control devices according to the first aspect, each of which is designed to generate a drive signal for controlling one of the semiconductor switches of the inverter based on the information; and a control system coupled to the plurality of control devices and designed to send the information to the plurality of control devices.

[0022] In particular, parallel clocking on high-side (HS) switches and / or on parallel LS switches allows for faster discharging and / or the power loss to be distributed across several switches.

[0023] According to a further development, the plurality of control devices are further configured to receive measurement information relating to the inverter and to send the measurement information to the control system; and the control system is further configured to send modified information to the plurality of control devices based on the measurement information.

[0024] According to a third aspect, the invention relates to a method for controlling an inverter, comprising the following steps: receiving information from a control system by a processor; and generating a drive signal based on the information by the processor for at least one semiconductor switch of the inverter, wherein the drive signal comprises a sequence of drive signal pulses, wherein the drive signal pulses each have a predetermined and adjustable pulse length, such that the semiconductor switch is not fully conductive during the pulse length when controlled with the control signal.

[0025] Short description of the drawings

[0026] They show:

[0027] Fig. 1 is a schematic representation of an electric drive system of a vehicle according to an embodiment of the invention;

[0028] Fig. 2 is a schematic representation of a signal diagram of a control signal for a semiconductor switch according to a further embodiment of the invention;

[0029] Fig. 3 is a schematic representation of a portion of an electric drive system of a vehicle according to an embodiment of the invention; and Fig. 4 is a schematic representation of an exemplary method 400 according to an embodiment.

[0030] In all figures, identical or functionally equivalent elements and devices are provided with the same reference numerals. The numbering of process steps serves the purpose of clarity and is generally not intended to imply a specific chronological order. In particular, several process steps can be performed simultaneously.

[0031] Description of the embodiments

[0032] Fig. 1 shows a schematic representation of an electric drive system 100 of a vehicle (with an electric machine 3). The electric drive system 100 comprises two input terminals T+ and T-, which can be supplied with high voltage, for example, by an energy storage device such as a high-voltage battery or a traction battery of the vehicle. The input terminals T+ and T- are connected to a DC intermediate circuit, which has an intermediate circuit capacitor 2. The intermediate circuit capacitor 2 is connected via output terminals to input terminals of an inverter 10, for example a pulse-controlled inverter 10. The voltage intermediate circuit converter shown in Fig. 1 with the intermediate circuit capacitor 2 and the inverter 10 is shown by way of example as a three-phase converter, i.e., the inverter 10 comprises three bridge branches, each with two semiconductor switches.The first bridge branch comprises, for example, the semiconductor switches la and ld, the first bridge branch, for example, the semiconductor switches lb and le and the third bridge branch, for example, the semiconductor switches lc and lf. The semiconductor switches la, lb, lc on one side of the bridge are referred to as high-side (HS) switches, and the semiconductor switches ld, le, lf on the other side of the bridge are referred to as low-side (LS) switches. It should be clear that any other number of bridge branches or phases of the voltage source converter is also possible, and that the designation of the semiconductor switches la to lf as high-side and low-side switches is only an example. The semiconductor switches la to If shown in Fig. 1 can, for example, have field-effect transistors (FETs).In one possible embodiment, the semiconductor switches are each IGBTs (Insulated Gate Bipolar Transistors), but it is also possible to provide other semiconductor switches in a corresponding form, for example in the form of JFETs (Junction Field-Effect Transistors), SIC switches, or MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors). If the semiconductor switches 1a to 1f comprise IGBT switches, it may be provided to connect a diode (not shown in Fig. 1 for reasons of clarity) in anti-parallel to each of the IGBT switches.

[0033] The electric drive system 100 further comprises a control system 50 configured to generate switching signals 5a to 5f, which comprise information regarding the activation of the semiconductor switches 1a to 1f. The control system 50 may be or comprise a processor (microprocessor). Such information may include, for example, one or more of the following: a command for active discharge; the side (NV / HV, HS / LS) on which the activation pulses are activated (on which the switches 1 are activated); a pulse width / pulse length for the activation signal (of the driver signal pulses 18k) (see also "activated" operating modes below); a form of the activation signals (of the driver signal pulses 18k); a parameter for the gate current (this can be adjusted by the processor / control system 50 depending on an HV voltage and the temperature of the HV output stage). An exact timing (phase / starting point of the driver signal pulses 18k) does not need to be transmitted.The control system 50 feeds the switching signals 5a to 5f into corresponding control devices 4a to 4f, each of which is responsible for controlling one of the semiconductor switches 1a to 1f. The switching signals 5a to 5f can be transmitted via a single line (e.g., UART only) or via multiple lines (e.g., UART and PWM).

[0034] The control devices 4a to 4f can each comprise a processor (microprocessor and / or chip). The respective processors can execute the control (of the semiconductor switches 1a to 1f). The control can be based on the information from the switching signals 5a to 5f. For example, the control of the starting pulses in a short time frame (100ps) with regard to pulse duration and gate current can be handled by the control devices 4a to 4f (gate drivers).

[0035] The coupling of the control device 4a to the associated semiconductor switch 1a is explained below, wherein each of the remaining control devices 4b to 4f can be coupled accordingly.

[0036] The control device 4a has a control output via which a control signal 7a can be output to a control input of the semiconductor switch 1a in order to control the operation of the semiconductor switch 1a. The control device 4a can acquire measurement signals 8a and / or 9a via measuring lines (for example, to collect measurement information). The measurement signal 8a can, for example, indicate an instantaneous current through the semiconductor switch 1a. For this purpose, the measuring line via which the measurement signal 8a is acquired can, for example, be coupled to a current measurement output of the semiconductor switch 1a. The measurement signal 9a can, for example, indicate an instantaneous voltage at a connection terminal of the semiconductor switch 1a.For this purpose, the measuring line via which the measuring signal 9a is detected can be coupled, for example, to a collector terminal of the semiconductor switch la, in particular if the semiconductor switch la is an IGBT switch. The measuring signal 9a can be representative of the voltage at the intermediate circuit capacitor 2.

[0037] In certain operating modes of the inverter, it may now be necessary to rapidly discharge the intermediate circuit. With the control device 4, an IGBT switch 1 can be selectively "clocked," i.e., controlled in a pulsed mode by feeding control pulses into the control input 13 of the IGBT switch 1. The duration of these pulses is so short that the IGBT switch 1 is not yet fully switched to conduction, but rather briefly remains in a transition state between the off-state and conduction state (clocking signal / clocking pulses). During this time, energy from the intermediate circuit capacitor can be converted into heat when a current flows through the IGBT switch 1, thus quickly and effectively reducing the voltage in the intermediate circuit.This enables, in particular, the setting of a rapid discharge mode in an inverter controlled in this way, which advantageously allows for rapid discharge of an intermediate circuit capacitor feeding the inverter, for example, intermediate circuit capacitor 2. It is particularly advantageous that the existing components of the inverter can be used for discharging without the need to install additional circuits or discharge elements such as switchable resistors or the like.

[0038] To implement this operating mode, the control device 4 can be designed to generate the drive signal 18 as a sequence of control signal pulses 18k with a predetermined and adjustable pulse length, so that the IGBT switch 1 is not fully conductive during the pulse length when driven by the control signal 7. An exemplary possibility for such a sequence of drive signal pulses 18k is shown schematically in Fig. 2. The drive signal pulses 18k each have a pulse length T. This pulse length T can be short with respect to the drive duration in a normal control operation of the IGBT switch 1. For example, the switching duration of an IGBT switch 1, during which the IGBT switch 1 is closed or kept open in normal operation, can be approximately 100 ps. The pulse length T can in this case be a few ps, for example between 0.2 ps and 5 ps.The pulse length T can depend on the physical parameters of the IGBT switch 1. For example, the time the switch is "open" can be 100 s.

[0039] The reference symbols used in Fig. 2 (as well as elsewhere) can each be provided with letters from a to f in order to identify the respective components of the electric drive system 100 shown in Fig. 1.

[0040] Fig. 3 shows a schematic representation of part of an electric drive system of a vehicle according to an embodiment of the invention. This electric drive system can be the same or different from that shown in Fig. 1. The drive system of Fig. 3 also has three phases, which are graphically shown by staggering the frames (a different number of phases is also possible). Only the (components for the) first phase is shown explicitly, while the other phases are only indicated (by the staggering). The control system 50 can be or comprise a processor (microprocessor). The control system 50 has connections (for example connections for signals 5a to 5f in Fig. 1) to each of the control devices 4a to 4f (here only 4a and 4d are shown). These connections can each have two channels (two lines and / or two connections): a communication interface (UART) and a PWM drive signal.There can also be only one connection for the UART. Information regarding the control of the semiconductor switches 1a to 1f (to the corresponding control devices 4a to 4f) can be transmitted via the communication interface (UART) (or via the corresponding connections in general, or via the single connection in each case). Such information can include, for example, one or more of the following: a command for active discharge; the side on which trigger pulses are to be applied (this can alternatively be transmitted via a static signal to the PWM control signals); a pulse width for the trigger signal; a form of the trigger signals; a parameter for the gate current (this can be adjusted by the processor / control unit 50 depending on the HV voltage and the temperature of the HV output stage). Precise timing (phase / starting point of the driver signal pulses 18k) does not need to be transmitted.This can be implemented by the control device 4.

[0041] The connection(s) can be coupled to the control devices 4 via corresponding communication interfaces.

[0042] Based on the above-mentioned information, a processor 15(a to f) (included in the corresponding control device 4(a to f)) can control the trigger pulses (using software). This can happen, for example, in a short time frame (100ps) with regard to pulse duration and gate current. The respective processors 15a to 15f of the control devices 4a to 4f can also base the control of the trigger pulses on additional information, whereby this additional information was not provided by the control system 50. Implementing the control by processors in the control devices 4 (i.e., using software) is cost-effective, especially compared to alternative circuits and / or programmable logic. The individual control (from the control device 4, rather than from the control system 50) reduces the jitter that can arise due to NV-HV transmission.By clocking the (multiple) high-side (HS) switches in parallel, either discharging can occur more quickly or the power dissipation can be distributed across multiple switches. This also helps to address the problem of the high sensitivity of the discharge currents, and thus the power dissipation, to the duration of the trigger pulses, because the discharge path between T+ and T- has a very low resistance. Less space is also required. The circuit can be more reliable. The demands on the control processor are reduced.

[0043] The processors 15 may be low-voltage processors, CPUs, and / or GPUs. The processors 15 may be multi-core processors and / or microprocessors. The processors 15 may include any suitable type of data storage medium, such as volatile memory (e.g., random access memory (RAM)), non-volatile memory (e.g., flash memory), optical media, magnetic media, and so on.

[0044] Each processor 15a to 15f of the control devices 4a to 4f can be supplied with the same information from the control system. The precise timing (starting pulses) can then be controlled individually by each processor 15a to 15f. Thus, this timing can vary between the control devices 4a to 4f, and thus also the precise switching of the switches 1a to 1f. Alternatively, different control devices 4 (or different processors 15) can receive different information (or sometimes no information) from the control system 50. For example, all control devices 4 (d to f) for the high-voltage switches can receive the same information, and all control devices 4 (a to c) for the low-voltage switches can receive the same other information. In another example, the corresponding high-voltage-low-voltage pairs (i.e., ad, be, and cf) can each receive the same information (but different pairs receive different information).

[0045] The respective processor 15 can implement the active discharge on the high-voltage side (HV side). The active discharge can be aborted by the respective processor 15 via a low-voltage side (NV side). The number of phases and control devices 4 (with processors 15) can vary. The number of control devices 4 can be twice the number of phases. There can also be only one control device 4 and one switch 1.

[0046] In one aspect (alternatively or in addition to that previously disclosed), tracking (adaptation according to measurement information) of the trigger pulses can be implemented via the application software in the control controller 50. The application software in the control controller 50 has measurement information from the HV voltage, conductivity, and temperature of the HV power stage (and / or SIC temperature). This measurement information can be sent from the respective control devices to the control controller 50 (e.g., via UART). Based on this measurement information, the control controller 50 can adapt information (such as pulse width, start of discharge, gate current, etc., see above) for the control devices 4 / processors 15 (changed information). The control of the trigger signal can further be controlled by the respective control devices 4 / processors 15 based on the information from the control controller 50.

[0047] This aspect allows the tracking of the trigger pulses to be implemented via the application software in the control system 50, eliminating the need for other necessary hardware circuitry. Tracking allows for faster discharge times or a more even distribution of the discharge over a (specified) time. Implementation via the application software is also cost-effective.

[0048] Fig. 4 shows a schematic representation of an exemplary method 400 according to an embodiment. The method 400 can be executed by the processor 15 (or one of the processors described above) of the control device 4. The method 40 is for controlling an inverter 10, comprising the following steps: receiving 410 information from a control system 50 by a processor 15. generating 420 a driver signal 18 based on the information by the processor 15 for at least one of the semiconductor switches 1a to 1f of the inverter 10, wherein the driver signal 18 has a sequence of driver signal pulses 18k, wherein the driver signal pulses 18k each have a predetermined and adjustable pulse length (T), such that the semiconductor switch 1a to 1f is not fully conductive during the pulse length (T) when controlled with the control signal 7a to 7f.

[0049] Furthermore, the method 400 may comprise the following further steps: In step 430, the processor 15 may receive measurement information relating to the inverter 10 and send it to the control system 50. This may happen, for example, via measuring lines measuring signals 8a and / or 9a. In step 440, the control system 50 (not executed by the processor 15 of the control device 4) may send modified information to the plurality of control devices 4 based on the measurement information. In step 450, the processor 15 of the

[0050] Control device 4 receives the changed information and adjusts the driver signal 18 accordingly.

Claims

Claims 1. Control device (4) for controlling a semiconductor switch (1) of an inverter (10), wherein the control device (4) comprises: a processor (15) which is configured to: Receiving information from a control system (50); and Generating a drive signal (18) based on the information; wherein the drive signal (18) controls the semiconductor switch (1), and wherein the drive signal (18) comprises a sequence of drive signal pulses (18k) with a pulse length such that the semiconductor switch (1) is not fully conductive during the pulse length when driven with the control signal (7).

2. The control device (4) according to claim 1, wherein the information comprises one or more of the following: a command for active discharge; a side on which the semiconductor switch (1) is controlled; a pulse length of the drive signal pulses (18k); a shape of the drive signal pulses (18k); a parameter for the gate current.

3. Control device (4) according to one of claims 1 and 2, wherein the pulse length is adjustable such that the semiconductor switch (1) has a predetermined current value when controlled by the control signal (7).

4. Control device (4) according to one of claims 1 to 3, wherein the processor (15) is further configured to: Obtaining measurement information concerning the inverter (10); and Sending the measurement information to the control system (50).

5. The control device (4) according to any one of claims 1 to 3, wherein the control device (4) is configured to: couple to a current sensor output of the semiconductor switch (1); detect a second measurement signal (8) for a current through the semiconductor switch (1); and generate the drive signal (18) in dependence on the second measurement signal (8).

6. Control device (4) according to one of claims 1 to 5, wherein the control device (4) is designed to control an IGBT switch, SIC switch and / or MOSFET switch.

7. Control device (4) according to one of claims 1 to 6, wherein the inverter (10) has a half-bridge circuit, and wherein the control circuit (16) is designed to control one of the semiconductor switches (1) of a half-bridge with the driver signal (18) and to permanently close the other of the semiconductor switches (1) of the half-bridge.

8. A drive system (100) for an n-phase electrical machine (3), where n is greater than or equal to 1, comprising: an intermediate circuit capacitor (2) connected to two input voltage terminals (T+; T-); an inverter (10) having a plurality of semiconductor switches (1a, ..., 1f), which is coupled to the intermediate circuit capacitor (2), is supplied with electrical energy from the intermediate circuit capacitor (2), and is designed to generate an n-phase supply voltage for the electrical machine (3); a plurality of control devices (4a, ..., 4f) according to any one of claims 1 to 7, each of which is designed to generate a drive signal (18) for controlling one of the semiconductor switches (1a, ..., 1f) of the inverter (10) based on the information; and a control system (50) which is coupled to the plurality of control devices (4a, ..., 4f) and which is designed to to send the information to the plurality of control devices (4a, ..., 4f).

9. The drive system (100) according to claim 8, wherein: the plurality of control devices (4a, ..., 4f) are further configured to receive measurement information concerning the inverter (10) and send the measurement information to the control system (50); and the control system (50) is further configured to send modified information to the plurality of control devices (4a, ..., 4f) based on the measurement information.

10. A method (400) for controlling an inverter (10), comprising: Receiving (410) information from a control system (50) by a processor (15); Generating (420) a driver signal (18) on the basis of the information by the processor (15) for at least one semiconductor switch (1a, ..., lf) of the inverter (10), wherein the driver signal (18) has a sequence of driver signal pulses (18k), wherein the driver signal pulses (18k) each have a predetermined and adjustable pulse length, so that the semiconductor switch (1a, ..., lf) is not completely conductive during the pulse length when driven with the control signal (7a, ..., 7f).

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