Method for detecting faults in a DC-DC converter

Abstract

Method for detecting faults in a DC-DC converter (50) having a primary side (52) and a secondary side (54), wherein an output voltage (94) of the DC-DC converter (50) and an output current (88) of the DC-DC converter (50) are measured on the secondary side in order to detect a fault in the DC-DC converter (50).

Description

[0001] The invention relates to a method for detecting faults in a DC-DC converter, in particular a DC-DC converter in the on-board electrical system of a motor vehicle, and an arrangement for carrying out the method. State of the art

[0002] A DC-DC converter, also known as a DC / DC converter, is an electrical circuit designed and configured to convert a DC voltage at its input into a DC voltage that has a higher, lower or inverted voltage level compared to the DC voltage at the input.

[0003] In recent years, automotive development has seen a trend toward increasing electrification, meaning a growing number of electrical devices and components. In particular, the number of power electrical systems in vehicles is constantly growing. If one of these components malfunctions or even fails, the voltage supplied by the power grid can fall outside the normal operating range, resulting in a reduction in passenger comfort and safety.

[0004] Therefore, the rapid and early detection and identification of these faults when they occur is of great importance to increase the reliability and safety of power grids. Such detection has not yet been implemented.

[0005] A method for fault detection in a DC-DC converter is known from DE 10 2016 203 455 A1. The DC-DC converter has a primary side and an inductor. At least one switch is used on the primary side. In the method, a current through the inductor, a switch, or a diode of the DC-DC converter is measured during each switching period and compared with a calculated current to detect a fault. The method can detect a short circuit or an open circuit. Disclosure of the invention

[0006] Against this background, a method according to claim 1 and an arrangement according to claim 7 are presented. The invention further relates to a computer program according to claim 11 and a machine-readable storage medium having the features of claim 12. Embodiments emerge from the dependent claims and from the description.

[0007] The presented method is used to detect faults in a DC-DC converter that has a primary side and a secondary side. In the method, an output voltage of the DC-DC converter and an output current of the DC-DC converter are measured on the secondary side in order to detect a fault in the DC-DC converter.

[0008] In the method, an output voltage is measured on the secondary side of the DC-DC converter. If this output voltage differs from a reference voltage by at least a predetermined threshold value, an output current of the DC-DC converter is measured to detect a fault in the DC-DC converter.

[0009] If the output voltage differs from the reference voltage by at least the specified threshold and if the measured output current is almost zero, an open circuit fault caused by a switch on the secondary side of the DC-DC converter is detected.

[0010] If the output voltage differs from the reference voltage by at least the specified threshold and if the measured output current is negative, an error caused by an EMC filter on the secondary side of the DC-DC converter is detected.

[0011] It was thus recognized that, with existing solutions, an error caused by a power-off switch or an EMC (electromagnetic compatibility) filter cannot be detected. However, the method presented here makes it possible to detect such an error.

[0012] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0013] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention. Short description of the drawings Fig. 1 shows a block diagram of a DC-DC converter which is designed to carry out the described method. Fig. 2 shows a flow chart of a possible sequence of the presented procedure. Embodiments of the invention

[0014] The invention is illustrated schematically in the drawings using embodiments and is described in detail below with reference to the drawings.

[0015] Fig. Figure 1 shows a DC-DC converter, which is designated overall by the reference numeral 50 and has a primary side 52 and a secondary side 54. The illustration shows an energy storage device 62, a first switch S1 64 with associated driver 66, a diode D1 68, an inductance L1 70, a capacitor C1 72, a second switch S2 74, safety-relevant loads R1 76, non-safety-relevant loads R2 78 and a battery 80. Furthermore, currents are indicated in the illustration with the aid of arrows, namely i L 82, i S 84, i D 86 and i DCDC 88 at the output of the DC-DC converter 50.

[0016] Further arrows indicate voltages, namely U pn1 90, U c 92 and V DCDC 94, the output voltage of the DC-DC converter 50. Furthermore, a controller 100 is shown. At the input of the controller 100, a difference between U ref 102 and U c92. In addition, the block diagram shows an EMC filter 110 and an electronic load distributor ePDU 120.

[0017] The second switch S2 74 is used for reverse polarity protection. The first switch S1 64 is a key component in the converter 60. If the driver 66 fails, the same problem arises as with a full-bridge converter. Early identification of a driver failure is therefore a challenge, as is the requirement to switch off the non-safety-relevant loads R2 78 as early as possible.

[0018] An overvoltage may also occur on the output side if the driver 66 is malfunctioning, causing the first switch S1 64 to short-circuit. This can compromise vehicle safety. Therefore, such faults should be identified as early as possible to take appropriate measures to increase system safety.

[0019] Previously, methods have been presented that utilize hardware to detect faults in switch S164, which in turn includes some additional circuit components. However, this leads to additional costs and increased circuit complexity. This is where the presented method comes in.

[0020] If, for example, the first switch S1 64 or the driver 66 assigned to it is defective, or if there is a short circuit, for example, then in one embodiment of the method presented the function of the first switch S1 64 can be briefly performed by the second switch S2 74.

[0021] The presented method now allows the detection of two possible errors: 1. Error caused by an open or broken circuit

[0022] Usually the voltage U c 92 via the capacitor C1 is largely the same as the reference voltage U ref 102. Is there a clear or significant difference between the voltage reference U ref 102 and the output voltage V DCDC 94 of the DC-DC converter 50, which in this case is measured by the ePDU 120. If, for example, Vref>(VDCDC+xV) and the current i DCDC88 is almost zero, then the interruption error caused by switch S2 is detected. xV is an unspecified offset voltage that depends on the system voltage. This is, for example, 2 V and defines the threshold of the presented method.

[0023] V DCDC and V C are typically almost identical, slight deviations may occur due to voltage drops across the line resistances and across the switch S2 74. Usually, V C > V DCDC , but only with a slight difference. 2. Circuit fault caused by EMC filter 110 in the DC-DC converter 60

[0024] If V ref > V DCDC over a specified period of time and the current i DCDC is negative, then there is a problem with the intended function of the EMC circuit 110 in the DC-DC converter 100.

[0025] To implement the presented method, an arrangement 130 is provided, which includes an evaluation unit 132, which in turn is configured to record and evaluate the measured variables, i.e., output voltage 94 and output current 88, and evaluate them accordingly. Suitable measuring devices are provided for measuring the variables, i.e., a current measuring device for measuring the output current 88 and a voltage measuring device for measuring the output voltage 94, in this case, the electronic load distributor 120.

[0026] Fig. 2 shows a flowchart of a possible sequence of the presented method. In a first step 200, the operation of a DC-DC converter in the on-board electrical system of a motor vehicle begins. In a next step 202, the output voltage of the DC-DC converter is compared with a reference voltage. A difference is determined. If this difference exceeds a predetermined threshold value or, depending on the design, this difference reaches a predetermined threshold value, then (arrow 204) the process continues with step 206. In particular, it is determined whether the reference voltage exceeds the measured output voltage by a predetermined value. Otherwise, a jump occurs (arrow 208) to step 202. The measurement of the output voltage can take place continuously, at timed, possibly regular intervals, or as needed or requested.

[0027] In step 206, the current at the output of the DC-DC converter is measured. If this is almost zero, an open circuit fault (arrow 210) is detected, ie a fault caused by an open circuit, caused by switch S2 (reference number 74 in Fig. 1), is determined (step 212). If the current measurement shows that it is negative, it is determined (step 214) that a current passed through the EMC filter (reference number 110 in Fig. 1) induced circuit fault (step 216). A sufficiently high, positive current is the normal, fault-free case.

[0028] The method presented is therefore particularly used to detect faults on the secondary side of the DC-DC converter. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2016 203 455 A1

[0005]

Claims

[1] Method for detecting faults in a DC-DC converter (50) having a primary side (52) and a secondary side (54), wherein an output voltage (94) of the DC-DC converter (50) and an output current (88) of the DC-DC converter (50) are measured on the secondary side in order to detect a fault in the DC-DC converter (50). [2] Method according to claim 1, wherein an output voltage (94) of the DC-DC converter (50) is measured on the secondary side and, if this differs from a reference voltage (102) by at least one predetermined threshold value, an output current (88) of the DC-DC converter (50) is measured in order to detect a fault in the DC-DC converter (50). [3] Method according to claim 1 or 2, wherein, when the output voltage (94) differs from the reference voltage (102) by at least the predetermined threshold value and when the measured output current (88) is nearly zero, an interruption fault caused by a switch (74) on the secondary side (54) of the DC voltage converter (50) is detected. [4] Method according to claim 1 or 2, wherein, if the output voltage (94) differs from the reference voltage (102) by at least the specified threshold value and if the measured output current (88) is negative, an error caused by an EMC filter (110) on the secondary side (54) of the DC voltage converter (50) is detected. [5] Method according to any one of claims 1 to 4, wherein the output voltage (94) of the DC voltage converter (50) is measured with an electronic load distributor (120). [6] Method according to any one of claims 1 to 5, wherein, when a fault is detected, a suitable measure is taken. [7] Arrangement for detecting faults in a DC voltage converter (50) having a primary side (52) and a secondary side (54), wherein the arrangement includes an evaluation unit configured to perform a method according to any one of claims 1 to 6. [8] Arrangement according to claim 7, to which a voltage measuring device is assigned. [9] Arrangement according to claim 8, wherein an electronic load distributor (110) serves as the voltage measuring device. [10] Arrangement according to one of claims 7 to 9, to which a current measuring device is assigned. [11] Computer program with program code means configured to execute a method according to any one of claims 1 to 6 when the computer program is executed on a computing unit, in particular a computing unit in an arrangement according to claim 7. [12] Machine-readable storage medium with a computer program stored thereon according to claim 11.

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