DC-to-DC converter and method for operating a DC-to-DC converter

Abstract

The invention relates to a DC-to-DC converter and to a method for operating a galvanically separating DC-to-DC converter, wherein additional or alternative monitoring is provided. Specifically, an electric voltage between the primary winding of a transformer and a switching element connected to the primary winding is detected and analyzed, allowing to draw conclusions about the secondary-side voltage ratios.

Description

[0001] Description

[0002] title

[0003] DC-DC converter and method for operating a DC-DC converter

[0004] Technical area

[0005] The present invention relates to a DC-DC converter and a method for operating a DC-DC converter.

[0006] background

[0007] DC-DC converters are used to convert one electrical direct voltage into another. A DC-DC converter can convert a DC voltage supplied at one input into another DC voltage whose magnitude is greater or less than the voltage at the input.

[0008] In addition, so-called galvanic isolating DC-DC converters are known, which can realize a galvanic isolation between electrical voltage at the input and electrical voltage at the output, for example by means of a transformer.

[0009] The document DE 20 2012 009 919 Ul, for example, describes a DC-DC converter in the form of a flyback DC-DC converter with a transformer for galvanic isolation between the input terminal and the output terminal.

[0010] Disclosure of the invention

[0011] The present invention provides a DC-DC converter and a method for operating a DC-DC converter having the features of the independent patent claims. Further advantageous embodiments are the subject of the dependent patent claims. Accordingly, it is provided:

[0012] A DC-DC converter with an input terminal, an output terminal, a transformer, a switching element, a first rectifier circuit, a control device, and a monitoring device. The input terminal is designed to be coupled to a DC voltage source. An electrical load or a DC-DC converter, for example, can be connected to the output terminal. The transformer comprises a primary main winding and a secondary main winding. The primary main winding is assigned, for example, to the input terminal, and the secondary main winding can be assigned to the output terminal. The switching element is arranged between a connection point of the input terminal and a connection point of the primary main winding. The first rectifier circuit is arranged between the secondary main winding and the output terminal.The control device is designed to control the switching element. In particular, the control device can control the switching element on the primary-side main winding of the transformer in a clocked manner. The monitoring device is designed to detect an electrical voltage at a node between the switching element and the connection point of the primary-side main winding. Furthermore, the monitoring device is designed to monitor a function of the DC-DC converter using the detected voltage.

[0013] Furthermore, it is planned:

[0014] A method for operating a DC-DC converter in which a switching element is arranged between an input terminal and a primary side of a transformer. For example, the DC-DC converter can be the DC-DC converter according to the invention described above. The method comprises a step for periodically opening and closing the switching element. The method further comprises a step for detecting an electrical voltage at a node between the switching element and the primary side of the transformer. In addition, the method comprises a step for detecting a malfunction of the DC-DC converter. The malfunction can occur in particular using the electrical voltage at a node between the switching element and the primary side of the transformer.

[0015] Advantages of the invention

[0016] DC-DC converters can, for example, be operated in such a way that, using a DC voltage provided on the input side, a DC voltage with specified properties, such as a predetermined output voltage, is provided on the output side. If galvanic isolation is required between the input and output of the DC-DC converter, complex galvanic isolation is also required between the measured values ​​acquired on the output side and an input-side control system.

[0017] Alternatively, a secondary-side transformer voltage can be estimated using an additional primary-side auxiliary winding on the transformer. However, if a fault occurs in this primary-side auxiliary winding or a downstream circuit, the output voltage cannot be correctly estimated. In particular, a short circuit in the area of ​​this primary-side auxiliary winding could result in the output voltage being estimated as too low. This creates the risk that a control system will increase the output voltage to a maximum value. Therefore, it is desirable to avoid such faults or at least detect them early.

[0018] It is therefore an idea of ​​the present invention to create an alternative or additional possibility for drawing conclusions about the output-side properties of a galvanically isolated DC-DC converter, such as a flyback DC-DC converter, by evaluating an input-side measured variable. In particular, an electrical voltage on a secondary side of the transformer in the DC-DC converter can be estimated.

[0019] If such an evaluation or monitoring of the secondary-side voltage conditions is used in addition to a primary-side auxiliary winding, redundant monitoring is available. This allows potential faults such as a short circuit in the primary-side auxiliary winding to be detected. Appropriate measures, such as shutting down the DC-DC converter, can then be initiated. In particular, this prevents the DC-DC converter's control system from further increasing the output voltage in the event of a fault in the primary-side auxiliary winding.

[0020] The present invention takes advantage of the fact that, during clocked operation of the primary-side switching element on the primary-side main winding of the transformer, a feedback of the secondary-side voltage conditions occurs when the switching element is open on the primary side of the main winding. This feedback voltage can be tapped and evaluated at the node between the transformer winding and the switching element.

[0021] According to one embodiment, the switching element comprises a semiconductor switching element. In particular, the semiconductor switching element can be, for example, a MOSFET, a bipolar transistor, or an IGBT. Such semiconductor switching elements enable fast, wear-free switching, as required for clocking in the DC-DC converter.

[0022] According to one embodiment, the monitoring device is designed to detect the electrical voltage at the node between the switching element and the connection point of the primary-side main winding when the switching element is open. This detected voltage at the node can then be evaluated in a suitable manner. In particular, by detecting and evaluating the primary-side voltage at the node when the switching element is open, conclusions can be drawn about the secondary-side voltage conditions.

[0023] According to one embodiment, the control circuit is designed to detect a malfunction in the DC-DC converter if the electrical voltage and / or a voltage curve at the node between the switching element and the connection point of the primary-side main winding deviates from an expected value or an expected voltage curve. This allows easy-to-implement monitoring and fault detection to be implemented. In particular, additional, redundant monitoring can be created in this way. This can increase operational reliability. According to one embodiment, the monitoring device is designed to determine a value for an output voltage at the output terminal of the DC-DC converter using the electrical voltage at the node between the switching element and the connection point of the primary-side main winding.In particular, the output voltage can be determined when the switching element is open. The voltage at the node can be easily used to draw conclusions about the secondary voltage conditions due to the feedback from the secondary side of the transformer to the primary side.

[0024] According to one embodiment, the transformer comprises a primary-side auxiliary winding. This primary-side auxiliary winding can be coupled to the monitoring device via a second rectifier circuit. This, together with the monitoring of the electrical voltage at the node between the switching element and the transformer, provides two redundant paths for monitoring the DC-DC converter.

[0025] According to one embodiment, the monitoring device is designed to detect a malfunction in the DC-DC converter by comparing the electrical voltage from the second DC-DC converter with the electrical voltage at the node between the switching element and the connection point of the primary-side main winding. By combining or comparing the electrical voltage at the primary-side auxiliary winding and the electrical voltage at a node between the switching element and the primary-side main winding, the two detected values ​​can be checked for plausibility. This redundant monitoring thus enables an additional safety gain.

[0026] According to one embodiment, the monitoring device is designed to control the control circuit using a voltage level of an electrical voltage from the second rectifier circuit. Thus, the control of the control circuit and the resulting output voltage of the DC-DC converter can be achieved using the electrical voltage at the primary-side auxiliary winding, while simultaneously monitoring and verifying the plausibility of the electrical voltage and the circuit components involved using the electrical voltage at the node between the primary-side main winding and the switching element. Such redundancy can increase the safety and reliability of the voltage converter, and malfunctions in the event of a fault in the primary-side auxiliary winding can be quickly detected.

[0027] According to one embodiment, the DC-DC converter comprises a plurality of secondary-side main windings. A separate first rectifier circuit is provided for each of the secondary-side main windings, which can rectify the electrical voltage from a secondary side of the main winding and provide it to a respective output terminal. In this way, a DC-DC converter can be realized that generates and provides a plurality of electrically isolated output DC voltages from an input-side DC voltage.

[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] Short description of the drawings

[0030] Further features and advantages of the invention are explained below with reference to the figures.

[0031] Fig. 1: a schematic representation of a DC-DC converter according to a

[0032] embodiment;

[0033] Fig. 2: a schematic representation of a DC-DC converter according to a further embodiment; and

[0034] Fig. 3: a flow chart of a method for operating a

[0035] DC-DC converter according to one embodiment. Description of embodiments

[0036] Figure 1 shows a schematic representation of a DC-DC converter 1 according to one embodiment. The DC-DC converter 1 can, for example, be a DC-DC converter implemented in the form of a so-called flyback DC-DC converter, in particular an isolating or galvanically isolating flyback DC-DC converter.

[0037] The DC-DC converter 1 comprises an input terminal 11 and an output terminal 12. For example, any DC voltage source (not shown) can be connected to the input terminal 11. On the output side, a DC voltage network or any DC voltage consumer can be connected. For example, the DC-DC converter 1 can convert an electrical DC voltage U_in provided at the input terminal 11 into another, for example, higher DC voltage U_out and provide this at the output terminal 12.

[0038] The DC-DC converter 1 further comprises a transformer 20. The transformer 20 has at least one primary-side main winding 21 and one secondary-side main winding 22. Furthermore, the transformer 20 can have a primary-side auxiliary winding 23. In addition to compact windings with two external terminals each, one or more of these windings 21, 22, 23 can also be realized from several partial windings that are connected to one another (externally).

[0039] The primary-side main winding 21 is electrically coupled to the input terminal 11. A switching element 30 is provided between a connection point of the primary-side main winding 21 and a connection point of the input terminal 11. This switching element 30 can be controlled, for example, by a control device 50. In particular, the switching element 30 can be controlled in a clocked manner by the control device 50. The switching element 30 can, for example, be a semiconductor switching element such as a MOSFET or a bipolar transistor. The DC-DC converter 1 further comprises a first rectifier circuit 40 between the secondary-side main winding 22 and the output terminal 12. The rectifier circuit 40 can, for example, as shown in Figure 1, comprise a rectifier diode 41 between a connection point of the secondary-side main winding 22 and a connection point of the output terminal 12.Furthermore, a capacitor 42 can be provided, for example, between the two connection points of the output terminal 12 for stabilizing and, if necessary, filtering the output voltage.

[0040] A further rectifier circuit 60 can be provided between the control device 50 and the primary-side auxiliary winding 23. This rectifier circuit 60 can, for example, comprise a diode 61 between a connection point of the primary-side auxiliary winding 23 and the control device 50. Furthermore, further components, such as a capacitor 62, can also be provided if necessary.

[0041] In this way, the control device 50 can also draw conclusions about the secondary-side voltage conditions, in particular the electrical voltage at the secondary-side main winding 22 or the output voltage U_out at the output terminal 12, using the electrical voltage at the primary-side auxiliary winding 23 or the electrical voltage provided by the further rectifier circuit 60. Accordingly, the control device 50 can regulate the control of the switching element 30 in order to set a predetermined output voltage U_out at the output terminal 12.

[0042] A monitoring device 55 is also provided in the DC-DC converter 1. This monitoring device 55 is electrically coupled to a node between the switching element 30 and the connection point of the primary-side main winding 21 of the transformer 20. In this way, the monitoring device 55 can detect and evaluate the electrical voltage at this node. In particular, by evaluating this electrical voltage, the monitoring device 55 can draw conclusions about the secondary-side voltage conditions. For example, when the switching element 30 is open, the secondary-side voltage can feed back to the primary side of the transformer 20 and thereby induce an electrical voltage at the primary-side main winding 21. This can be detected and evaluated by the monitoring device 55. For example, this can be used to detect possible malfunctions in the DC-DC converter 1.Additionally or alternatively, it may also be possible to control or regulate the DC-DC converter 1 using the electrical voltage at the node point between the switching element 30 and the primary-side main winding 21.

[0043] The monitoring device 55 can, for example, also check or verify the plausibility of the electrical voltage at the primary-side auxiliary winding 23 or from the further rectifier circuit 30 using the electrical voltage at the node between the switching element 30 and the primary-side main winding 21. For this purpose, for example, the respective electrical voltages or voltage curves can be compared with one another. If both voltages provide at least approximately the same information regarding the secondary-side voltage conditions in the DC-DC converter 1, the corresponding signals, in particular the voltage values ​​from the primary-side auxiliary winding 23 or the further rectifier circuit 60, can be regarded as reliable. Accordingly, the control of the DC-DC converter 1, i.e. the clocking of the switching element 30, can be carried out on the basis of these voltage values.

[0044] If a fault occurs, for example, in which a short circuit or similar condition occurs in the primary-side auxiliary winding 23 or the additional rectifier circuit 60, this deviation can be detected by evaluating the electrical voltage at the junction point between the switching element 30 and the primary-side main winding 21. Appropriate measures, such as shutting down the DC-DC converter 1, can then be initiated if necessary.

[0045] Thus, by evaluating the electrical voltage at the node between switching element 30 and the primary-side main winding 21, a simple, additional possibility is available for implementing additional redundancy for monitoring the voltage conditions in the DC-DC converter 1. This can increase the operational reliability of the DC-DC converter 1.

[0046] In the embodiment shown in Figure 1, the monitoring device 55 is shown as a separate component outside the control device 50. With such a configuration, the monitoring or plausibility check of the electrical voltage from the auxiliary winding 23 can therefore be carried out separately and thus independently of the function of the control device 50. Alternatively, it is also possible to provide the monitoring device 55 within the control device 50.

[0047] Figure 2 shows a schematic representation of a DC-DC converter 1 according to another embodiment. The DC-DC converter according to Figure 2 differs from the previously described embodiment in particular in that multiple output terminals 12-i are provided. Accordingly, in such an embodiment, the DC-DC converter 1 can also comprise a secondary-side main winding 22-i and a corresponding rectifier circuit 40-i for each output terminal 12-i.

[0048] For such a configuration, the previously described concept of input-side monitoring by means of the electrical voltage at the node between the switching element 30 and the primary-side main winding 21 can also be applied in the same way.

[0049] The embodiment shown in Figure 2, with only two secondary main windings 22-1 and 22-2 and two downstream rectifier circuits 40-1, 40-2 for the two output terminals 12-1, 12-2, serves merely to illustrate the basic principle of the invention. Furthermore, this principle can also be adapted for more than two outputs. The individual output voltages for the respective output terminals 12-i can be individually adjusted by a suitable selection of the corresponding secondary main windings 22-i.

[0050] Figure 3 shows a schematic representation of a flowchart underlying a method for operating a DC-DC converter 1 according to one embodiment. The method can be applied in particular to a previously described DC-DC converter 1. Therefore, all embodiments already described in connection with Figures 1 and 2 also apply to the method described below. Likewise, the previously described DC-DC converter 1 can comprise any components that may be required to implement the method described below. The method comprises a step S 1 for periodically opening and closing the switching element 30. Furthermore, the method comprises a step S 2 for detecting an electrical voltage at a node between the switching element 30 and the primary side 21 of the transformer 20.Furthermore, the method comprises a step S 3 for detecting a malfunction of the DC-DC converter 1. The detection of the.

[0051] Malfunction can occur, in particular, using the electrical voltage at a node between the switching element 30 and the primary side 21 of the transformer 20. In summary, the present invention relates to a DC-DC converter and a method for operating a galvanically isolating DC-DC converter, wherein additional or alternative monitoring is provided. In particular, it is proposed to detect and evaluate an electrical voltage between the primary winding of a transformer and a switching element connected to the primary winding. This allows conclusions to be drawn about the secondary-side voltage conditions.

Claims

Claims 1. A DC-DC converter (1), comprising: an input terminal (11) designed to be coupled to a DC voltage source; an output terminal (12); a transformer (20) having a primary-side main winding (21) and a secondary-side main winding (22); a switching element (30) arranged between a connection point of the input terminal (11) and a connection point of the primary-side main winding (21); a first rectifier circuit (40) arranged between the secondary-side main winding (22) and the output terminal (12); a control device (50) designed to control the switching element (30);and a monitoring device (55) designed to detect an electrical voltage at a node point between the switching element (30) and the connection point of the primary-side main winding (21) and to monitor a function of the DC-DC converter (1) using the detected voltage; 2. DC-DC converter (1) according to claim 1, wherein the switching element (30) comprises a semiconductor switching element.

3. DC-DC converter (1) according to claim 1 or 2, wherein the monitoring device (55) is designed to detect and evaluate the electrical voltage at the node point between the switching element (30) and the connection point of the primary-side main winding (21) when the switching element (30) is open.

4. DC-DC converter (1) according to one of claims 1 to 3, wherein the monitoring device (55) is designed to detect a malfunction in the DC-DC converter (1) if the electrical voltage and / or a voltage curve at the node between the switching element (30) and the connection point of the primary-side main winding (21) deviates from an expected value or an expected voltage curve.

5. DC-DC converter (1) according to one of claims 1 to 4, wherein the monitoring device (55) is designed to determine a value for an output voltage (U_out) at the output terminal (12) of the DC-DC converter (1) using the electrical voltage at the node point between the switching element (30) and the connection point of the primary-side main winding (21).

6. DC-DC converter (1) according to one of claims 1 to 5, wherein the transformer (20) further comprises a primary-side auxiliary winding (23) which is coupled to the control device (50) via a second rectifier circuit (60).

7. DC-DC converter (1) according to claim 6, wherein the monitoring device (55) is designed to detect a malfunction in the DC-DC converter (1) using a comparison between the electrical voltage from the second rectifier circuit (60) and the electrical voltage at the node point between the switching element (30) and the connection point of the primary-side main winding (21).

8. DC-DC converter (1) according to claim 6 or 7, wherein the control device (50) is designed to control the switching element (30) using a voltage level of an electrical voltage from the second rectifier circuit (60).

9. DC-DC converter (1) according to one of claims 1 to 8, with a plurality of secondary-side main windings (22-i), wherein for each secondary-side main winding (22-i) a separate first Rectifier circuit (40-i) and a separate output terminal (12-i) are provided.

10. Method for operating a DC-DC converter (1), in which a switching element (30) is arranged between an input terminal (11) and a primary side (21) of a transformer (20), comprising the steps of: periodically opening and closing (S 1) the switching element (30); Detecting (S 2) an electrical voltage at a node between the switching element (30) and the primary side (21) of the transformer (20); and Detecting (S 3) a malfunction of the DC-DC converter (1) using the electrical voltage at a node point between the switching element (30) and the primary side (21) of the transformer (20).

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