Controller for a DC-to-DC converter, DC-to-DC converter device, motor vehicle, and method for inspecting a DC-to-DC converter

Abstract

The invention relates to the inspection of a DC-to-DC converter in the event of an output-side overvoltage. A physically detectable operating parameter of the DC-to-DC converter is used to decide whether the detected overvoltage is caused by the DC-to-DC converter or whether the cause for the overvoltage can originate from outside of the DC-to-DC converter.

Description

[0001] Description

[0002] title

[0003] Control device for a DC-DC converter, DC-DC converter device, motor vehicle and method for monitoring a DC-DC converter

[0004] Technical area

[0005] The present invention relates to a control device for a DC-DC converter and a method for monitoring a DC-DC converter. The present invention further relates to a DC-DC converter device and a motor vehicle having such a DC-DC converter device.

[0006] background

[0007] Vehicles that are fully or at least partially electrically powered usually have an electrical energy storage unit that provides the electrical energy to drive the vehicle. This electrical energy storage unit and the associated electric drive system usually have a voltage level of several hundred volts. The vehicle electrical system at this voltage level is referred to as the high-voltage network. In addition, such vehicles usually have an additional, so-called low-voltage network in the range between 12 and 48 volts. The high-voltage network and the low-voltage network can be coupled to one another via a DC-DC converter. This makes it possible to exchange electrical energy between the high-voltage network and the low-voltage network. In particular, the low-voltage network can also be supplied with electrical energy from the electrical energy storage unit in the high-voltage network.The publication DE 10 2008 002 177 A1, for example, describes a vehicle electrical system with several sub-networks which are coupled to one another by means of a voltage converter.

[0008] Disclosure of the invention

[0009] The present invention provides a control device for a DC-DC converter, a DC-DC converter device, a motor vehicle, and a method for monitoring a DC-DC converter with the features of the independent patent claims. Further advantageous embodiments are the subject of the dependent patent claims.

[0010] Accordingly, it is provided:

[0011] A control device for a DC-DC converter, wherein the DC-DC converter is configured to convert a first DC voltage provided at an input terminal into a second DC voltage and to provide this second DC voltage at an output terminal. The control device is configured to detect an overvoltage at the output terminal. Furthermore, the control device is configured to record at least one operating parameter in the DC-DC converter. Furthermore, the control device is configured to determine, using the recorded at least one operating parameter, whether the detected overvoltage is caused by the DC-DC converter.

[0012] Furthermore, it is planned:

[0013] A DC-DC converter device comprising an input terminal, an output terminal, a DC-DC converter, and a control device according to the invention. The input terminal is designed to be connected to a DC voltage source. The output terminal is designed to be coupled to an electrical load. The DC-DC converter is designed to convert a first DC voltage provided at the input terminal into a second DC voltage and to provide this second DC voltage at the output terminal. Furthermore, the following is provided:

[0014] A motor vehicle having a high-voltage vehicle electrical system, a low-voltage vehicle electrical system and a DC-DC converter device according to the invention, which is designed to be coupled to the high-voltage vehicle electrical system at the input terminal and to be coupled to the low-voltage vehicle electrical system at the output terminal.

[0015] Finally, it is planned:

[0016] A method for monitoring a DC-DC converter, wherein the DC-DC converter converts a first DC voltage provided at an input terminal into a second DC voltage and provides the second DC voltage at an output terminal. The method comprises a step for detecting an overvoltage at the output terminal. The method further comprises a step for recording at least one operating parameter in the DC-DC converter. The method further comprises a step for determining whether the detected overvoltage is caused by the DC-DC converter. The determination is carried out in particular using the recorded at least one operating parameter.

[0017] Advantages of the invention

[0018] When operating a DC / DC converter, such as one used in an electric vehicle to connect the high-voltage grid to the low-voltage grid, a secondary or output-side voltage can be monitored to detect, for example, overvoltages, i.e., voltages above a specified threshold. If such an overvoltage occurs, the DC / DC converter should no longer be operated if the DC / DC converter is the cause of the overvoltage. To do this, it must be determined whether a detected overvoltage was caused by the DC / DC converter or whether the cause of the overvoltage could be due to another, external cause.Conventional approaches for distinguishing the cause of an overvoltage fault typically require first deactivating the DC-DC converter for a specified, extended period of time, as well as evaluating the electrical voltage while the DC-DC converter is deactivated. Based on this insight, the present invention seeks to create a simple, safe, and reliable method for determining, when an overvoltage occurs at the output of the DC-DC converter, whether the overvoltage is caused by the DC-DC converter itself or by another, external cause.

[0019] For the analysis according to the invention, at least one operating parameter of the DC-DC converter is recorded and evaluated during the detection of an overvoltage in order to determine whether the DC-DC converter may be the cause of the overvoltage. Since suitable operating parameters are generally already recorded and thus available for other purposes, such as for controlling the DC-DC converter, the recording of the required operating parameters according to the invention does not require any additional hardware. This makes it particularly easy and cost-effective to decide whether the DC-DC converter may be responsible for an overvoltage.

[0020] From the operating parameter(s) under consideration, it can be deduced, for example, whether the DC / DC converter was providing electrical energy at the output at the time an overvoltage was detected. If, for example, it is determined based on an electrical voltage, an electrical current flow, or a control signal in the DC / DC converter that no energy was flowing to the output of the DC / DC converter at the time the overvoltage was detected, it can be assumed that the cause of the overvoltage was not the DC / DC converter. If, on the other hand, it is determined that the DC / DC converter was directing electrical energy towards the output terminal at the time an overvoltage was detected, this can be interpreted as an indication that this energy from the DC / DC converter could be a possible cause of the overvoltage.

[0021] Such an analysis of the operating parameters at the time of overvoltage detection thus enables a simple and reliable decision as to whether the DC / DC converter may be the cause of the overvoltage or not. In contrast to conventional approaches, it is not mandatory to first deactivate the DC / DC converter for a predetermined period of time and then analyze the voltage conditions at the DC / DC converter's output during this period. Thus, especially in the case where the DC / DC converter is not responsible for an overvoltage, electrical energy can be immediately supplied again by the DC / DC converter when the electrical voltage at the DC / DC converter's output terminal drops.This can prevent interruptions in the power supply at the output of the DC-DC converter if the DC-DC converter was not responsible for the overvoltage at the time of detection of the overvoltage.

[0022] According to one embodiment, the control device for the DC-DC converter is designed to at least temporarily deactivate the DC-DC converter if the overvoltage is caused by the DC-DC converter. If it is assumed that the DC-DC converter was responsible for the overvoltage, deactivating the DC-DC converter can prevent a potentially dangerous overvoltage from being present on the output side of the DC-DC converter for an extended period of time. If necessary, the DC-DC converter can be reactivated after a predetermined pause time. If no further overvoltage occurs, the DC-DC converter can continue to operate.

[0023] According to one embodiment, the control device is designed to continue operating the DC-DC converter in an active state if an overvoltage has been detected at the output terminal, but it has been determined that the overvoltage is not caused by the DC-DC converter. This ensures that when the electrical voltage at the output terminal drops, the DC-DC converter can immediately provide electrical energy again at the output terminal, thus ensuring a continuous energy supply at the output terminal.

[0024] According to one embodiment, the at least one operating parameter comprises a physical or sensor-detectable variable in the DC-DC converter. Such an operating parameter can be any suitable variable that can be measured using a corresponding sensor. In particular, the at least one operating parameter can be, for example, an electrical current, an electrical voltage, and / or a control signal within the DC-DC converter. Such variables are generally recorded and monitored anyway. In particular, these variables can also be used, for example, for control or regulation purposes in the DC-DC converter.

[0025] According to one embodiment, the DC-DC converter comprises a transformer. This transformer can be used, in particular, for galvanic isolation between the input terminal and the output terminal. In such a configuration, the at least one operating parameter can, for example, comprise an operating parameter on the secondary side of the transformer, i.e., in the region between the transformer and the output terminal. In particular, possible operating parameters include, for example, an electrical voltage on the secondary side of the transformer, an electrical output current, and / or a pulse-width-modulated control signal for a semiconductor switching element in the DC-DC converter.

[0026] In addition to secondary-side operating parameters, operating parameters on the primary side of the DC-DC converter are also possible, depending on the application. For example, an electrical current at the input of the DC-DC converter or a control signal, particularly a PWM signal, can be used on the primary side of the DC-DC converter.

[0027] According to one embodiment, the control device is designed to classify the DC-DC converter as the cause of the overvoltage if an output current, a secondary-side transformer voltage, and / or a duty cycle of the control signal in the DC-DC converter exceeds a predetermined threshold. The threshold can, in particular, be set such that exceeding the threshold represents a significant energy flow from the input terminal to the output terminal.

[0028] The above embodiments and further developments can be combined with one another as desired, where appropriate. Further embodiments, further developments, and implementations of the invention also include combinations of features of the invention not explicitly mentioned above or described below with respect to the exemplary embodiments. In particular, those skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

[0029] Brief description of the drawings Further features and advantages of the invention are explained below with reference to the figures. They show:

[0030] Fig. 1: a schematic representation of an on-board electrical system of a motor vehicle with a DC-DC converter device according to an embodiment;

[0031] Fig. 2: a DC-DC converter device with a control device for a DC-DC converter according to an embodiment; and

[0032] Fig. 3: a flowchart which may form the basis of a method for monitoring a DC-DC converter according to one embodiment.

[0033] Description of embodiments

[0034] Figure 1 shows a schematic representation of the coupling of two DC voltage networks 2, 3 by means of a DC-DC converter device 1 according to one embodiment. The two DC voltage networks 2, 3 can be, for example, the high-voltage on-board network 2 and the low-voltage on-board network 3 in an electric vehicle. The high-voltage network 2 can, for example, comprise an electrical energy storage device 21 such as a traction battery. Furthermore, an electric drive system 22 can be provided in the high-voltage network 2. In addition, any other electrical loads can of course also be fed from the high-voltage network 2. As a rule, such a high-voltage network will have a voltage level of several hundred volts, for example approximately 400 volts or 800 to 1000 V. One or more electrical consumers 32 can be provided in the low-voltage network 3.Furthermore, an electrical energy storage device 31 can also be provided in the low-voltage network 3. The high-voltage network 2 and the low-voltage network 3 can be coupled to one another by means of a DC-DC converter device 1. In this way, it is possible, for example, to transfer electrical energy from the high-voltage network 2, in particular from the electrical energy storage device 21, to the low-voltage network 3 by means of the DC-DC converter device 1 and thus to supply the electrical consumers 32 with energy. Furthermore, the electrical energy storage device 31 in the low-voltage network 3 can also be charged in this way, so that the electrical consumers 32 can be supplied with electrical energy even when the DC-DC converter device 1 is not active.The DC-DC converter device 1 can either be a unidirectional DC-DC converter device that only transfers energy from the high-voltage network 2 to the low-voltage network 3. Alternatively, a bidirectional DC-DC converter device 1 can also be provided, which also transfers electrical energy from the low-voltage network 3 to the high-voltage network 2.

[0035] To protect the low-voltage network 3 and in particular the components 31, 32 connected to the low-voltage network 3, the electrical voltage in the low-voltage network 3 can be monitored. If an electrical voltage above a predetermined threshold is detected, suitable protective measures can be provided when such an overvoltage occurs. These protective measures can, for example, distinguish whether an overvoltage that occurs was caused by the DC-DC converter device 1 or whether the cause of the overvoltage is not due to the DC-DC converter device 1.

[0036] In the event that an overvoltage may have been caused by the DC-DC converter device 1, provision may be made to deactivate the DC-DC converter device 1 at least temporarily. If necessary, the DC-DC converter device 1 can then be reactivated after a predetermined time. If no further overvoltage subsequently occurs in the output-side DC voltage network 3 of the DC-DC converter device 1, the DC-DC converter device 1 can continue to operate. Otherwise, the DC-DC converter device 1 must be deactivated again.

[0037] If, however, the cause of an overvoltage in the output-side low-voltage network 3 is not caused by the DC-DC converter device 1, the DC-DC converter device 1 can continue to be operated in an active state. In such an active state, in particular, the control of the DC-DC converter device 1 remains active. Thus, after a drop in the electrical voltage in the output-side low-voltage network 3, the DC-DC converter device 1 can immediately feed electrical energy back into the low-voltage network 3. This ensures that the electrical components 31 and 32 in the low-voltage network 3 can be immediately supplied with electrical energy again via the DC-DC converter device 1 after the cause of the overvoltage has been eliminated.This ensures that the consumers 32 in the low-voltage network 3 are continuously supplied with electrical energy, even if no electrical energy storage device 31 is provided in the low-voltage network 3.

[0038] Figure 2 shows a schematic representation of a DC-DC converter device 1 according to one embodiment. Even though the basic principle of the invention is described predominantly in connection with a unidirectional DC-DC converter device 1, which transmits electrical energy from a predetermined input side, in particular a first power supply network 2, to an output side, in particular a second power supply network 3, this is not intended to represent a limitation of the present invention. Rather, the basic principle of the invention can also be applied to bidirectional DC-DC converter devices 1, which can transmit electrical energy between two DC voltage networks in any direction.

[0039] The DC-DC converter device 1 can, for example, enable galvanic isolation between the first power supply network 2 and the second power supply network 3. For this purpose, the DC-DC converter 1a in the DC-DC converter device 1 can comprise a transformer 13 or transmitter that enables galvanic isolation. The primary-side components 11 of the DC-DC converter 1a can be provided between an input terminal 1b, which can be coupled to the first power supply network, and a primary side of the transformer 13. Analogously, the secondary-side components 12 can be provided between a secondary side of the transformer 13 and an output terminal 1c, which can be coupled to the second power supply network 3. Since the basic structure or circuit topology of such a DC-DC converter 1a is considered known, a more detailed explanation is omitted here.Rather, Figure 2 merely shows, by way of example, a voltage sensor, a current sensor, and a semiconductor switching element for the primary-side components 11 and the secondary-side components 12 to illustrate possible timing in the corresponding circuit area. For example, a current sensor in the primary-side components 11 can detect an input current of the DC-DC converter 1a. Analogously, a current sensor in the output-side components 12 can detect an output current of the DC-DC converter 1a. A voltage sensor in the primary-side components 11 can detect an input voltage and / or an electrical voltage on the primary side of the transformer 13. Analogously, for example, a voltage sensor in the secondary-side components 12 can detect an electrical voltage on the secondary side of the transformer 13.Furthermore, for example, clock signals, in particular clock signals for a pulse-width modulated control of semiconductor switching elements, can also be generated and thus also detected or monitored.

[0040] The previously described signals, such as current and voltage values ​​and clock signals, but also any other suitable operating parameters, in particular operating parameters which correspond to a physical variable in the DC-DC converter 1a and which can be detected, for example, by sensors, can be provided to a control device 10 in the DC-DC converter device 1. Furthermore, the control device 10 can also monitor the output-side electrical voltage and, in particular, detect an overvoltage if the monitored electrical voltage exceeds a predetermined threshold value. If an overvoltage is detected, the control device 10 can then determine whether the detected overvoltage is caused by the DC-DC converter device 1 or whether the cause of the detected overvoltage cannot be attributed to the DC-DC converter device 1.

[0041] For this purpose, the control device 10 can record one or more operating parameters of the DC-DC converter 1a. In particular, this can be one of the previously mentioned operating parameters of the DC-DC converter 1a. If an overvoltage is detected at the output terminal 1c, the control device 10 can then decide whether or not the cause of this overvoltage is the DC-DC converter 1a. For example, the control device 10 can compare one or more of the recorded operating parameters with corresponding threshold values. If at least one of the determined operating parameters exceeds (or falls below) a corresponding threshold value, the control device 10 can then decide that the cause of the detected overvoltage may possibly be the DC-DC converter 1a.If, however, none of the predetermined conditions is met after the detection of an overvoltage during an analysis of the determined operating parameters, the control device 10 can decide that the cause of the overvoltage is not caused by the DC-DC converter 1a and lies outside the DC-DC converter device 1.

[0042] If the control device 10 decides that the cause of the overvoltage was not caused by the DC-DC converter 1a, the DC-DC converter 1a can continue to be operated in an active state. As already explained above, in such an active state, the control of the DC-DC converter 1a can continue to be operated such that, when the electrical voltage at the output terminal 1c of the DC-DC converter 1a drops, electrical energy is immediately transferred again from the input side 1b to the output side 1c. If, on the other hand, it is determined that the cause of an overvoltage may be caused by the DC-DC converter 1a, the control device 10 can deactivate the DC-DC converter 1a, at least temporarily. This is intended to prevent the DC-DC converter 1a from further causing the detected overvoltage.If necessary, the DC-DC converter 1a can be reactivated after a specified waiting period. A check can then be made again to determine whether an overvoltage occurs on the output side 1c. If no overvoltage is detected, the DC-DC converter 1a can continue to operate. Otherwise, the DC-DC converter 1a is deactivated again.

[0043] Figure 3 shows a flowchart underlying a method for monitoring a DC-DC converter 1a according to one embodiment. The method can, in principle, comprise any steps as previously described in connection with Figures 1 and 2. Analogously, the previously described components can also comprise any elements that may be required to implement the method described below.

[0044] The method comprises a step S1 for detecting an overvoltage at an output terminal 1c of a DC-DC converter 1a.

[0045] The method further comprises a step S2 for recording at least one operating parameter in the DC-DC converter 1a. The step S2 for recording the at least one operating parameter does not necessarily have to take place after the overvoltage has been detected. Rather, the recording of the operating parameter can also take place in parallel with the overvoltage detection. Furthermore, it is also possible to begin recording the operating parameter before the overvoltage is detected. This can be particularly appropriate if the operating parameter is also used for other purposes, for example for controlling the DC-DC converter 1a. This operating parameter can be a physical operating parameter, i.e. an operating parameter that can be recorded physically or sensorily using suitable measuring technology.

[0046] Furthermore, the method comprises a step S3 for determining whether the detected overvoltage is caused by the DC-DC converter 1a. This determination can be carried out in particular using the detected at least one operating parameter.

[0047] In a further optional step, the DC-DC converter 1a can be deactivated at least temporarily if it has previously been determined that the overvoltage could have been caused by the DC-DC converter 1a. Otherwise, the DC-DC converter 1a can continue to be operated in an active state in which, after the electrical voltage at the output terminal 1c of the DC-DC converter 1a drops, electrical energy can be immediately provided again at the output terminal 1c.

[0048] In summary, the present invention relates to the monitoring of a DC-DC converter when an overvoltage occurs on the output side. Using a physically detectable operating parameter of the DC-DC converter, it is possible to determine whether the detected overvoltage is caused by the DC-DC converter or whether the cause of the overvoltage may lie outside the DC-DC converter.

Claims

Claims 1. Control device (10) for a DC-DC converter (1a), which is designed to convert a first DC voltage provided at an input terminal (1b) into a second DC voltage and to provide it at an output terminal (1c), wherein the control device (10) is designed to detect an overvoltage at the output terminal (1b), to record at least one operating parameter in the DC-DC converter (1a), and to determine, using the recorded at least one operating parameter, whether the detected overvoltage is caused by the DC-DC converter (1a).

2. Control device (10) according to claim 1, wherein the control device (10) is designed to deactivate the DC-DC converter (1a) at least temporarily if the overvoltage is caused by the DC-DC converter (1a).

3. Control device (10) according to claim 1 or 2, wherein the control device (10) is designed to continue to operate the DC-DC converter (1a) in an active state if an overvoltage has been detected at the output terminal (1c) and it has been determined that the overvoltage is not caused by the DC-DC converter (1a).

4. Control device (10) according to one of claims 1 to 3, wherein the at least one operating parameter comprises a physical and / or sensor-detectable quantity in the DC-DC converter (1a).

5. Control device (10) according to one of claims 1 to 4, wherein the at least one operating parameter comprises an electrical current, an electrical voltage and / or a control signal in the DC-DC converter (1a).

6. Control device (10) according to one of claims 1 to 5, wherein the DC-DC converter (1a) comprises a transformer (13) for galvanic isolation between the input terminal (1b) and the output terminal (1c), and wherein the at least one operating parameter comprises an operating parameter on the secondary side (12) between the transformer (13) and the output terminal (1c).

7. Control device (10) according to claim 6, wherein the control device (10) is designed to classify the DC-DC converter (1a) as the cause of the overvoltage if an output current, a secondary-side transformer voltage and / or a duty cycle of a control signal in the DC-DC converter exceed a predetermined threshold value.

8. A DC-DC converter device (1) comprising an input terminal (1b) configured to be connected to a DC voltage source (21), an output terminal (1c) configured to be coupled to an electrical load (32), a DC-DC converter (1a) configured to convert a first DC voltage provided at the input terminal (1b) into a second DC voltage and to provide it at the output terminal (1c); and a control device (10) according to one of claims 1 to 7.

9. Motor vehicle, with a high-voltage vehicle electrical system (2), a low-voltage vehicle electrical system (3), and a DC-DC converter device (1) according to claim 8, which is coupled to the high-voltage vehicle electrical system (2) at the input terminal (1b) and is coupled to the low-voltage vehicle electrical system (3) at the output terminal (1c).

10. A method for monitoring a DC-DC converter (1a), wherein the DC-DC converter (1a) converts a first DC voltage provided at an input terminal (1b) into a second DC voltage and provides it at an output terminal (1c), the method comprising the following steps: Detecting (Sl) an overvoltage at the output terminal (1c); detecting (S2) at least one operating parameter in the DC-DC converter (1a); and Determining (S3) whether the detected overvoltage is caused by the DC-DC converter (1a) using the detected at least one operating parameter.

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