AUXILIARY VOLTAGE SUPPLY FOR POWER CONVERTER AND USE THEREOF IN VEHICLES

Abstract

The invention relates to a circuit arrangement (1) for generating an auxiliary DC voltage (VLV), having:—a half bridge circuit (2) which outputs a load current (IL) and which converts a DC voltage (V1) into an AC voltage, and—wherein the half bridge circuit (2) has, in each of the two branches (A1, A2), at least two switch elements (S1, S2 and S3, S4) arranged in series and—wherein a flying capacitor (3) is connected in parallel to corresponding switch elements (S2, S3) in each of the two branches (A1, A2), characterized by:—an auxiliary voltage generating unit (5) which is supplied with electrical energy by the flying capacitor (3) and which is designed to generate an auxiliary DC voltage (VLV) which is less than or equal to 48 V. The invention also relates to an associated method for generating an auxiliary DC voltage and to a power converter and a vehicle having such a circuit arrangement.

Claims

1. A circuit arrangement for generating an auxiliary direct current (DC) voltage, the circuit arrangement comprising: a half-bridge circuit configured to output a load current and convert a DC voltage into an alternating current (AC) voltage, wherein the half-bridge circuit includes, in each of two branches, at least two switching elements arranged in series; a flying capacitor that is connected in parallel with respectively corresponding switching elements of the two branches; and an auxiliary voltage generating unit supplied with electrical energy by the flying capacitor and configured to generate the auxiliary DC voltage of less than or equal to 48 V.

2. The circuit arrangement of claim 1, wherein a voltage at the flying capacitor is controllable by a choice of switching times of the switching elements.

3. The circuit arrangement of claim 1, further comprising at least two link circuit capacitors arranged in series on an input side in parallel with the half-bridge circuit.

4. The circuit arrangement of claim 1, wherein the auxiliary voltage generating unit comprises: a full-bridge circuit; a transformer supplied by the full-bridge circuit; and a rectifier circuit supplied by the transformer.

5. A power converter comprising: a circuit arrangement for generating an auxiliary direct current (DC) voltage, the circuit arrangement comprising: a half-bridge circuit configured to output a load current and convert a DC voltage into an alternating current (AC) voltage, wherein the half-bridge circuit includes, in each of two branches, at least two switching elements arranged in series; a flying capacitor that is connected in parallel with respectively corresponding switching elements of the two branches; and an auxiliary voltage generating unit supplied with electrical energy by the flying capacitor and configured to generate an auxiliary DC voltage of less than or equal to 48 V.

6. The power converter of claim 5, wherein the power converter is an inverter.

7. A vehicle comprising: a power converter comprising: a circuit arrangement for generating an auxiliary direct current (DC) voltage, the circuit arrangement comprising: a half-bridge circuit configured to output a load current and convert a DC voltage into an alternating current (AC) voltage, wherein the half-bridge circuit includes, in each of two branches, at least two switching elements arranged in series; a flying capacitor that is connected in parallel with respectively corresponding switching elements of the two branches; and an auxiliary voltage generating unit supplied with electrical energy by the flying capacitor and configured to generate an auxiliary DC voltage of less than or equal to 48 V.

8. The vehicle claim 7, wherein the vehicle is an aircraft.

9. The vehicle of claim 8, further comprising: an electric motor supplied with electrical energy by the power converter; and a propeller that is settable in rotation by the electric motor.

10. A method for generating an auxiliary direct current (DC) voltage, the method comprising: outputting, by a half-bridge circuit, a load current; converting, by the half-bridge circuit, a DC voltage into an AC voltage, wherein the half-bridge circuit includes, in each of two branches, at least two switching elements arranged in series, and wherein a flying capacitor is connected in parallel with respectively corresponding switching elements of the two branches; and supplying an auxiliary voltage generating unit with electrical energy from the flying capacitor, such that the auxiliary DC voltage is generated, the auxiliary DC voltage being less than or equal to 48 V.

11. The power converter of claim 5, wherein a voltage at the flying capacitor is controllable by a choice of switching times of the switching elements.

12. The power converter of claim 5, wherein the circuit arrangement further comprises at least two link circuit capacitors arranged in series on an input side in parallel with the half-bridge circuit.

13. The power converter of claim 5, wherein the auxiliary voltage generating unit comprises: a full-bridge circuit; a transformer supplied by the full-bridge circuit; and a rectifier circuit supplied by the transformer.

14. The vehicle of claim 7, wherein a voltage at the flying capacitor is controllable by a choice of switching times of the switching elements.

15. The vehicle of claim 7, wherein the circuit arrangement further comprises at least two link circuit capacitors arranged in series on an input side in parallel with the half-bridge circuit.

16. The vehicle of claim 7, wherein the auxiliary voltage generating unit comprises: a full-bridge circuit; a transformer supplied by the full-bridge circuit; and a rectifier circuit supplied by the transformer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows a circuit diagram of a circuit arrangement in accordance with the prior art;

[0026] FIG. 2 shows a block diagram of one embodiment of a circuit arrangement with auxiliary voltage generating unit;

[0027] FIG. 3 shows a circuit diagram of one embodiment of a circuit arrangement with auxiliary voltage generating unit;

[0028] FIG. 4 shows a block diagram of one embodiment of a power converter; and5

[0029] FIG. 5 shows one embodiment of an aircraft including a power converter.

DETAILED DESCRIPTION

[0030] FIG. 2 shows auxiliary voltage architecture according to the present embodiments based on the example of a quasi-2L converter (only one phase is illustrated, however). In this case, a voltage at a flying capacitor 3 is controlled by the offset of the switching on times of the switching elements S.sub.1 to S.sub.4; the flying capacitor 3 is provided for stabilizing the switching transients and simultaneously forms an input capacitor of an auxiliary voltage generating unit 5.

[0031] FIG. 2 shows a circuit arrangement 1 in accordance with FIG. 1, including a half-bridge circuit 2 and a parallel flying capacitor 3. The auxiliary voltage generating unit 5 is arranged in parallel with the flying capacitor 3 and is supplied by the electrical energy stored in the flying capacitor 3. The auxiliary voltage generating unit 5 generates an auxiliary DC voltage VLV of less than or equal to 48 V.

[0032] FIG. 3 shows one example of a circuit of the auxiliary voltage generating unit 5. A full-bridge circuit 5.1 is situated on an input side and generates an AC voltage from an input DC voltage. The AC voltage is fed to a transformer 5.2 for the purpose of potential isolation. On an output side, a rectifier circuit 5.3 is connected to the transformer 5.2. The auxiliary DC voltage VLv is then available at the output of the rectifier circuit 5.3.

[0033] A topology of the auxiliary voltage generating unit 5 may be chosen and designed by the designer freely, in principle, but is to provide the transformer 5.2 for the purpose of voltage isolation on account of the potential at the flying capacitor 3.

[0034] An advantage of this architecture is that the switches of the full-bridge circuit are not loaded with the full link circuit voltage (e.g., >1 kV) but rather with the maximum voltage at the flying capacitor 3, which is significantly smaller depending on the number of levels. Switches with the same voltage requirement as in the power circuit (e.g., switching elements S.sub.1 to S.sub.4) may thus be incorporated (e.g., but with a lower current requirement).

[0035] In this context, however, it may also already be predicted that the flyback topology that is very popular for auxiliary voltage converters is not optimal here because the topology, with respect to the input voltage, additionally applies the transformed output voltage to the switches.

[0036] For the case of a redundant auxiliary voltage architecture, either the magnetic circuit of the transformer may be additionally tapped, or the energy is supplied via diodes to the capacitor at the output. With the architecture in any case, a supply path from high voltage to low voltage may have been produced in a suitable manner, which has been possible hitherto only using additional high-voltage auxiliary converters.

[0037] The concept presented here may be used either as a “stand-alone” auxiliary voltage supply for AC/DC, DC/AC and DC/DC multilevel power converters (e.g., quasi multilevel power converters), or as an additional auxiliary voltage branch for critical applications, such as in aviation, for example.

[0038] FIG. 4 shows a block diagram of one embodiment of a DC/AC power converter 7 (e.g., of an inverter) including a circuit arrangement for generating a three-phase AC voltage. For this purpose, a half-bridge circuit 2 together with flying capacitor 3 are embodied for each phase. The half-bridge circuit 2 is supplied with DC voltage by a link circuit capacitor 4. Each flying capacitor 3 supplies a respective auxiliary voltage generating unit 5.

[0039] FIG. 5 shows one embodiment of an electric or hybrid electric aircraft 8 (e.g., an airplane) including a power converter 7 in accordance with FIG. 4 that supplies an electric motor 9 with electrical energy. The electric motor 9 drives a propeller 10. The electric motor 9 and the propeller 10 are part of an electrical thrust-generating unit. A power converter 7 may also be part of an on-board electrical system.

[0040] Although the invention has been described and illustrated more specifically in detail using the exemplary embodiments, the invention is not restricted by the disclosed examples, and other variations may be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention.

[0041] The elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent. Such new combinations are to be understood as forming a part of the present specification.

[0042] While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications can be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.