Snubber for a DC voltage converter

Abstract

To provide a low-cost snubber that ensures reliable overvoltage protection in a bidirectional DC voltage converter.SOLUTION: A snubber (2) for a DC voltage converter, comprising a storage unit (6) and a discharge element (8), wherein the storage unit (6) comprises a first capacitor (10), a second capacitor (12), a controllable switch (14) and a switching means (16), wherein the controllable switch (14) is connected in series to the first capacitor (10) and the second capacitor (12) is connected in series to the switching means (16), the first capacitor (10) or the first capacitor (10) and the controllable switch (14) are connected in parallel to the second capacitor (12) and the switching means (16), and the discharge element (8) is configured to discharge the second capacitor (12).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a snubber for a DC voltage converter and to a DC voltage converter including a snubber according to the invention. [Background technology]

[0002] DC voltage converters are used to convert a DC voltage supplied to an input side into a DC voltage having a higher, lower or inverted voltage level, and electrical switches are used to switch and control the DC voltage converters.

[0003] In this case, there is a problem that overvoltages can occur in the DC voltage converter when switching off the electrical switch. For example, in the case of a galvanically isolated DC voltage converter, the transformer current is rectified in the output choke. In this case, overvoltages occur due to the current flowing through the stray inductance of the transformer. The transformer must quickly adapt to the current value of the output choke due to the new current path created by the switch-off. When converting voltage in the other direction, overvoltages occur due to the current flowing through the intermediate circuit choke.

[0004] Due to the overvoltage, switches with higher voltage resistance must be used, which leads to poor electromagnetic compatibility, which increases costs.

[0005] An alternative solution is snubbers. Snubbers can be used to reduce overvoltages. In this case, snubbers are used to damp undesired oscillations and overvoltage peaks in DC voltage converters. The simplest form of snubber is a series connection of a capacitor and a resistor. However, this snubber is passive and generates very high additional losses. Furthermore, lossless passive snubbers exist that transfer the energy of overvoltages at the moment of freewheeling to the output side of the converter. However, these snubbers cannot be used in bidirectional DC voltage converters.

[0006] In the case of a bidirectional DC-DC converter, an active snubber can be used, which includes an electronic switch and a capacitor. U.S. Pat. No. 6,038,142 discloses a currently popular circuit. In this case, the capacitor absorbs the overvoltage energy at the switching moment. After current matching is achieved in the two connected inductances, the electronic switch can be switched on to redischarge the capacitor. However, if the electronic switch is switched off, for example, due to an emergency shutdown, the snubber cannot reduce the overvoltage as specified. In such cases, significantly higher overvoltages occur due to unfavorable switching times or overcurrents, which require a significantly larger capacitance in the snubber than is required for effective normal operation. In particular, a larger capacitance results in a lower natural resonant frequency of the snubber, which in turn causes undesirable oscillations in the snubber due to the switching process of the DC-DC converter. This can reduce the effectiveness of the snubber to the point where it becomes unusable. A straightforward solution would be to realize the capacitance by connecting capacitors in parallel, each with a small capacitance and a small parasitic inductance, but this would increase the space required and the costs. Summary of the Invention [Problem to be solved by the invention]

[0007] Based on the above-mentioned prior art, it is an object of the present invention to provide a low-cost snubber which ensures reliable overvoltage protection even in bidirectional DC voltage converters during emergency switch-off. [Means for solving the problem]

[0008] According to a first aspect of the present invention, the above object is achieved by a snubber for a DC voltage converter, in particular a bidirectional DC voltage converter, the snubber for a DC voltage converter comprising a storage unit and a discharge element, the storage unit comprising a first capacitor, a second capacitor, a controllable switch and switching means, the controllable switch being connected in series with the first capacitor and the second capacitor being connected in series with the switching means, the first capacitor or the first capacitor and the controllable switch being connected in parallel with the second capacitor and the switching means, and the discharge element being configured to discharge the second capacitor.

[0009] The snubber according to the invention offers the advantage that the snubber is low in cost. Furthermore, the snubber can be used in bidirectional DC voltage converters. In the event of an emergency switch-off, and thus also in the event of an emergency switch-off of the switch, energy is directed to the second capacitor. The second capacitor has a sufficient capacity to absorb the energy and reliably reduce the overvoltage. The stored energy can then be dissipated via a discharge element.

[0010] The first capacitor may be connected in parallel with the second capacitor and the switching means. This allows for a particularly simple circuit, and therefore a particularly low-cost snubber. In this case, a current may flow through a controllable switch. For example, the controllable switch may be a MOSFET, which allows the controllable switch to be constantly conductive with respect to the current coming from the second capacitor. Alternatively, the first capacitor and the controllable switch may be connected in parallel with the second capacitor and the switching means. Advantageously, this prevents a current from flowing through the controllable switch. Therefore, an additional resistance due to the controllable switch is prevented.

[0011] Snubbers can reduce overvoltages, in which case they can damp undesirable oscillations and / or overvoltage peaks in a DC voltage converter.

[0012] A DC voltage converter can convert a DC voltage supplied to its input side into a DC voltage having a higher, lower or inverted voltage level.

[0013] The first and second capacitors may be passive electrical components capable of statically storing charge and associated energy in a direct current circuit in an electric field.

[0014] "Connected in parallel" can mean that in the case of bipolar electronic components of a snubber, their like poles are connected together. "Connected in series" can mean that the electronic components of a converter are connected one after the other, so that they form only one current path. Two electronic components can therefore be said to be connected in series if their connection has no branches.

[0015] The storage unit may be configured to store the overvoltage and dissipate it over time. The first capacitor may be configured to store the overvoltage during normal operation. The second capacitor may be configured to store the overvoltage during an emergency switch-off. For example, the storage unit, and thus the snubber, can compensate for the overvoltage in all situations.

[0016] The discharge element is configured to discharge the second capacitor. For discharging, the charge stored in the second capacitor can be dissipated through the discharge element. For example, the discharge element can be electrically connected to the second capacitor. In particular, a current can flow from the second capacitor to the discharge element.

[0017] The controllable switch may be an electronic switch configured to control the flow of current between two electrical terminals via a control voltage.

[0018] The switching means may be configured to control the current. The switching means may be a passive electronic component. For example, the passive electronic component may be configured such that the control of the current by the switching means may be invariable. For example, the passive electronic component may be configured such that the control of the current cannot be changed, for example, by a user or software. The switching means may be an active electronic component. For example, the active electronic component may be configured such that the control of the current by the switching means is variable. For example, the active electronic component may be configured such that the control of the current can be changed, for example, by a user or software. For example, the control may include regulating, amplifying, and / or blocking the current. The switching means may have, for example, a conducting direction and a blocking direction.

[0019] In one embodiment, the discharge element (8) may be connected in parallel with the second capacitor (12) and the switching means (16) may be a diode (18).

[0020] In this way, periodic discharges due to the diode are not possible, but passive discharge is performed via the discharge element. This makes it possible to avoid oscillations due to the capacitor's inherent resonance. Since the equipment may be switched off for some time after an emergency switch-off, the discharge element can be selected so that it does not generate significant losses during normal operation. Furthermore, this allows the second capacitor to be discharged independently, eliminating the need for further control. This makes it particularly simple to design the snubber, which can discharge the second capacitor self-sufficiently, i.e., without external drive, for example.

[0021] A diode may be a semiconductor-based electronic component that can pass current in one direction and block it in the other direction. A diode can have a conducting direction and a blocking direction.

[0022] In one embodiment, a series circuit consisting of a controllable switch and a first capacitor may be connected to a first node at a first end of the series circuit and to another node at the other end of the series circuit, a discharge element may be connected to the first node and the other node such that the discharge element can discharge the second capacitor, and the switching means may be a further controllable switch.

[0023] In this way, the discharge of the second capacitor can be particularly well controlled by the further controllable switch. Furthermore, existing discharge elements, such as resistors in the DC voltage converter, can be utilized. This makes it possible to dispense with additional discharge elements, making the snubber particularly simple and inexpensive to construct.

[0024] The controllable switch can be connected in series with the first capacitor, thereby forming a series circuit consisting of the controllable switch and the first capacitor.

[0025] The first node and / or the other node may be a connection point for an electronic component. The first node and / or the other node may be a junction of a network. The first node and / or the other node may be a location where a current branch can be formed. The electrical connection from the first node to the other node may be formed by a series connection consisting of a controllable switch and a first capacitor. Only the controllable switch and the first capacitor may be arranged along the electrical connection between the first node and the other node. For example, only the controllable switch and the first capacitor may be arranged along the electrical connection, but no additional electronic components may be arranged along the electrical connection.

[0026] The further controllable switch may be directly connected to the first node or the other node. For example, no further electronic components may be disposed between the further controllable switch and the first node or the other node. A further controllable switch and a second capacitor may be disposed along a further electrical connection between the first node and the other node.

[0027] The discharge element may be connected to the first node and the other node so that the discharge element can discharge the second capacitor. For discharging, the charge stored in the second capacitor can be dissipated through the discharge element. For example, the discharge element may be electrically connected to the second capacitor and the first and second nodes. For example, the discharge element, the second capacitor, the first node, and the second node can be arranged in a current circuit. Specifically, a current can flow from the second capacitor to the discharge element.

[0028] The further controllable switch may be an electronic switch, which may be configured to control the flow of current between two electrical terminals via a control voltage.

[0029] In one embodiment, the further controllable switch may be a transistor, preferably a MOSFET or an IGBT.

[0030] In this way, overvoltages can be reduced particularly well by the snubber in the event of an emergency shutdown, since the second capacitor can be connected to the current circuit as required.

[0031] In one embodiment, the discharge element may be a resistor, a varistor, or a Zener diode.

[0032] In this way, the discharge element, and thus the snubber, can particularly reliably guarantee overvoltage protection, since excess energy can be easily dissipated. Furthermore, the snubber can be particularly inexpensive. The resistor has the additional advantage that the resistor, and thus the snubber, is also inexpensive.

[0033] A resistor may be an impediment to current flow. In a resistor, electrical energy can be converted into heat. A varistor may have a voltage-dependent resistance. A Zener diode may be a diode that can be configured to operate continuously in the blocking direction in the region of the breakdown voltage.

[0034] In one embodiment, the capacitance of the second capacitor may be at least 10 times, preferably at least 100 times, and particularly preferably at least 300 times larger than the capacitance of the first capacitor.

[0035] In this case, in the event of an emergency shutdown, the overvoltage can be reduced particularly well by the snubber.

[0036] In one embodiment, the first capacitor may have a capacitance of 1 to 10 nF.

[0037] In this case, overvoltages can be reduced particularly well by the snubber during normal operation.

[0038] In one embodiment, the second capacitor may have a capacitance of at least 1 μF.

[0039] In this case, in the event of an emergency shutdown, the overvoltage can be reduced particularly well by the snubber.

[0040] In one embodiment, the controllable switch may be a transistor, preferably a MOSFET or an IGBT.

[0041] In this way, overvoltages can be reduced particularly well by the snubber during normal operation, since the first capacitor can be connected to the current circuit as required.

[0042] A switch can make or break a conductive connection using semiconductor components. A transistor can be an electronic semiconductor component for controlling or amplifying voltage and current.

[0043] A MOSFET (metal oxide semiconductor field effect transistor) may be a transistor. The MOSFET may have an insulated gate made of oxide. The MOSFET may be a field effect transistor with an insulated gate.

[0044] According to a second aspect of the present invention, the above problem is solved by a DC voltage converter comprising a snubber according to the present invention.

[0045] The DC voltage converter according to the present invention offers the advantage of being low-cost. In the event of an emergency switch-off, and thus of all switches in the DC voltage converter, energy is directed to a second capacitor. This second capacitor has sufficient capacity to absorb energy and limit overvoltages. However, due to the diode, periodic discharge is not performed, but a passive discharge is performed via the discharge element. This avoids oscillations due to the capacitor's inherent resonance. Since the equipment is switched off for a while after the emergency switch-off, the discharge element can be selected so that it does not generate significant losses during normal operation.

[0046] In one embodiment, the DC voltage converter may be bidirectional.

[0047] In this way, the usability of the DC voltage converter can be improved. Bidirectional can mean that the output can be converted in both directions of the DC voltage converter.

[0048] In one embodiment, the DC voltage converter may be galvanically isolated.

[0049] In this case, the safety of the DC voltage converter can be improved at low cost by providing galvanic isolation.

[0050] Further objects, features, advantages, and aspects of the present invention will be apparent to those skilled in the art from the following description and the appended claims. However, it should be understood that the following description, the appended claims, and specific examples illustrating preferred embodiments of the application are provided for illustrative purposes only. Various changes and modifications within the spirit and scope of the disclosed invention will be readily apparent to those skilled in the art from reading the following embodiments.

[0051] definition The following expressions generally and preferably have the meanings set out below, unless the context in which the expressions are used dictates otherwise.

[0052] As used herein, the term "comprising" encompasses and specifically relates to the terms "consisting essentially of" and "consisting of," in addition to its literal meaning. Thus, the term "comprising" relates to both embodiments in which the subject matter "comprising" of specifically listed elements does not include additional elements, and to embodiments in which the subject matter "comprising" of specifically listed elements can include and / or does include additional elements. The term "having" should also be understood as encompassing and specifically relating to the terms "consisting essentially of" and "consisting of." The term "consisting essentially of" particularly relates, whenever possible, to embodiments in which a subject matter contains no more than 20%, particularly no more than 15%, no more than 10%, or particularly no more than 5% of additional elements in addition to the specifically configured elements that substantially make up the subject matter. [Brief explanation of the drawings]

[0053] [Figure 1] FIG. 1 is a diagram showing a circuit diagram of a snubber; [Figure 2] FIG. 1 is a diagram showing a circuit diagram of a snubber; [Figure 3] FIG. 1 is a diagram showing a circuit diagram of a snubber; [Figure 4] FIG. 1 is a diagram showing a circuit diagram of a snubber; [Figure 5] FIG. 1 is a diagram showing a portion of a circuit diagram of a DC voltage converter. [Figure 6] FIG. 1 is a diagram showing a portion of a circuit diagram of a DC voltage converter. [Figure 7] FIG. 1 is a diagram showing a portion of a circuit diagram of a DC voltage converter. [Figure 8] FIG. 1 is a diagram showing a portion of a circuit diagram of a DC voltage converter. DETAILED DESCRIPTION OF THE INVENTION

[0054] FIG. 1 shows a circuit diagram of the snubber 2.

[0055] The snubber 2 for a DC voltage converter 4 includes a storage unit 6 and a discharge element 8. The storage unit 6 includes a first capacitor 10, a second capacitor 12, a controllable switch 14, and a switching means 16. The controllable switch 14 is connected in series with the first capacitor 10. The second capacitor 12 is connected in series with the switching means 16. The first capacitor 10 is connected in parallel with the second capacitor 12 and the switching means 16. The discharge element 8 is configured to discharge the second capacitor 12.

[0056] The discharge element 8 is connected in parallel with the second capacitor 12 and the switching means 16 is a diode 18 .

[0057] The discharge element 8 is a resistor. Alternatively, the discharge element 8 may be a varistor or a Zener diode. The capacitance of the second capacitor 12 is at least 300 times greater than the capacitance of the first capacitor 10.

[0058] The first capacitor 10 has a capacitance of 1 to 10 nF. The second capacitor 12 has a capacitance of at least 1 μF. The controllable switch 14 is a transistor, i.e., a MOSFET. Alternatively, the controllable switch 14 may be an IGBT.

[0059] FIG. 2 shows a circuit diagram of a further snubber 2 .

[0060] The snubber 2 for a DC voltage converter 4 includes a storage unit 6 and a discharge element 8. The storage unit 6 includes a first capacitor 10, a second capacitor 12, a controllable switch 14, and a switching means 16. The controllable switch 14 is connected in series with the first capacitor 10. The second capacitor 12 is connected in series with the switching means 16. The first capacitor 10 and the controllable switch 14 are connected in parallel with the second capacitor 12 and the switching means 16. The discharge element 8 is configured to discharge the second capacitor 12. The discharge element 8 is connected in parallel with the second capacitor 12, and the switching means 16 is a diode 18.

[0061] 3 shows a circuit diagram of a further snubber 2. The snubber 2 for a DC voltage converter 4 includes a storage unit 6 and a discharge element 8. The storage unit 6 includes a first capacitor 10, a second capacitor 12, a controllable switch 14, and a switching means 16. The controllable switch 14 is connected in series with the first capacitor 10. The second capacitor 12 is connected in series with the switching means 16. The first capacitor 10 is connected in parallel with the second capacitor 12 and the switching means 16. The discharge element 8 is configured to discharge the second capacitor 12.

[0062] A series circuit consisting of a controllable switch 14 and a first capacitor 10 is connected to a first node A at a first end of the series circuit and to a second node B at the other end of the series circuit. A discharge element 8 is connected to the first node A and to the second node B so that the discharge element 8 can discharge the second capacitor 12. The switching means 16 is a further controllable switch 20.

[0063] The further controllable switch 20 is a transistor. As can be seen from figure 3, the further controllable switch 20 is a MOSFET. Alternatively, the further controllable switch 20 may be an IGBT.

[0064] 4 shows a circuit diagram of a further snubber 2. The snubber 2 for a DC voltage converter 4 includes a storage unit 6 and a discharge element 8. The storage unit 6 includes a first capacitor 10, a second capacitor 12, a controllable switch 14, and switching means 16. The controllable switch 14 is connected in series with the first capacitor 10. The second capacitor 12 is connected in series with the switching means 16. The first capacitor 10 and the controllable switch 14 are connected in parallel with the second capacitor 12 and the switching means 16. The discharge element 8 is configured to discharge the second capacitor 12.

[0065] A series circuit consisting of a controllable switch 14 and a first capacitor 10 is connected to a first node A at a first end of the series circuit and to a second node B at the other end of the series circuit. A discharge element 8 is connected to the first node A and to the second node B so that the discharge element 8 can discharge the second capacitor 12. The switching means 16 is a further controllable switch 20.

[0066] The further controllable switch 20 is a transistor. As can be seen from figure 4, the further controllable switch 20 is a MOSFET. Alternatively, the further controllable switch 20 may be an IGBT.

[0067] Fig. 5 shows a portion of a circuit diagram of a DC voltage converter 4. The DC voltage converter 4 includes a snubber 2. The snubber 2 in Fig. 5 corresponds to the snubber 2 in Fig. 1, so for details, please refer to the description of Fig. 1.

[0068] The DC voltage converter 4 is bidirectional and is galvanically isolated.

[0069] Fig. 6 shows a portion of a circuit diagram of the DC voltage converter 4. The DC voltage converter 4 includes a snubber 2. The snubber 2 in Fig. 6 corresponds to the snubber 2 in Fig. 2, so for details, refer to the description of Fig. 2. The DC voltage converter 4 is bidirectional.

[0070] Figure 7 shows a portion of the circuit diagram of a DC voltage converter. The DC voltage converter 4 includes a snubber 2. The snubber 2 in Figure 7 corresponds to the snubber 2 in Figure 3, so please refer to the description of Figure 3 for details. The DC voltage converter 4 is bidirectional.

[0071] Figure 8 shows a portion of a circuit diagram of a DC voltage converter. The DC voltage converter 4 includes a snubber 2. The snubber 2 in Figure 8 corresponds to the snubber 2 in Figure 4, so please refer to the description of Figure 4 for details. The DC voltage converter 4 is bidirectional.

Claims

1. A snubber (2) for a DC voltage converter (4), in particular for a bidirectional DC voltage converter, comprising: The snubber (2) for the DC voltage converter (4) comprises a storage unit (6) and a discharge element (8), The storage unit (6) comprises a first capacitor (10), a second capacitor (12), a controllable switch (14), and a switching means (16); The controllable switch (14) is connected in series with the first capacitor (10); The second capacitor (12) is connected in series with the switching means (16); the first capacitor (10) or the first capacitor (10) and the controllable switch (14) are connected in parallel with the second capacitor (12) and the switching means (16); The discharge element (8) is configured to discharge the second capacitor (12). Snubber (2).

2. The discharge element (8) is connected in parallel with the second capacitor (12), The switching means (16) is a diode (18). The snubber according to claim 1.

3. a series circuit consisting of the controllable switch (14) and the first capacitor (10) connected to a first node (A) at a first end of the series circuit and to another node (B) at the other end of the series circuit; the discharge element (8) is connected to the first node (A) and the other node (B) so that the discharge element (8) can discharge the second capacitor (12); said switching means (16) being a further controllable switch (20); The snubber according to claim 1.

4. said further controllable switch (20) being a transistor, preferably a MOSFET or an IGBT; The snubber according to claim 3.

5. The discharge element (8) is a resistor, a varistor or a Zener diode. A snubber according to any one of claims 1 to 4.

6. The capacitance of the second capacitor (12) is at least 10 times, preferably at least 100 times, particularly preferably at least 300 times, greater than the capacitance of the first capacitor (10). A snubber according to any one of claims 1 to 5.

7. The first capacitor (10) has a capacitance of 1 to 10 nF. A snubber according to any one of claims 1 to 6.

8. The second capacitor (12) has a capacitance of at least 1 μF. A snubber according to any one of claims 1 to 7.

9. the controllable switch (14) is a transistor, preferably a MOSFET or an IGBT; A snubber according to any one of claims 1 to 8.

10. A DC voltage converter (4) comprising a snubber (2) according to any one of claims 1 to 9.

11. The DC voltage converter (4) is bidirectional.

11. The DC voltage converter according to claim 10.

12. The DC voltage converter (4) is galvanically isolated.

12. The DC voltage converter according to claim 10 or 11.

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