Isolating wide-range DC-DC converter

Abstract

The invention relates to a wide-range DC-DC converter (1) with a primary side (2) and a secondary side (3), the primary side (2) comprising a plurality of inverters (4) which are electrically connected to a plurality of primary windings (5), wherein the primary windings (5) either couple to a plurality of magnetic cores (6) and the secondary side (3) comprises a plurality of secondary windings (7), which also couple to the plurality of magnetic cores (6) and are each electrically connected to a rectifier (8), wherein the rectifiers (8) are connected in series, or wherein the primary windings (5) couple to a common magnetic core (6) and the secondary side (3) comprises a secondary winding (7), which also couples to the common magnetic core (6) and is electrically connected to a rectifier (8), or wherein the primary windings (5) couple to a plurality of magnetic cores (6) and the secondary side (3) comprises a plurality of secondary windings (7),which also couple to the plurality of magnetic cores (6) and which are connected in series and electrically connected to a rectifier (8), wherein either the primary winding numbers (9) differ from one another or, if appropriate, the secondary winding numbers (10) differ from one another, resulting in different transmission ratios. The invention further relates to a corresponding method.

Description

[0001] The invention relates to a DC-DC converter for comparatively wide control ranges and a method for converting a DC voltage over a comparatively wide control range.

[0002] All DC / DC converters in use today, whether isolating or non-isolating, designed to generate a fixed or only a limited variable output voltage, can only operate within a limited input voltage range. This is determined by the technically feasible modulation range of the converter. This also roughly corresponds to the range within which the input voltage may vary while still generating a fixed output voltage. Due to the transformation ratio of the isolating transformer in the intermediate circuit, the output voltage can be considerably higher or lower than the input voltage, but the control range remains roughly the same.

[0003] The problem is particularly pronounced when both the input voltage and the output voltage are to be variable. In this case, the converter must be designed so that, for example, the highest required output voltage can be generated at the lowest input voltage and the lowest required output voltage at the highest input voltage.

[0004] This problem is particularly prevalent today, for example, in the use of fuel cells, whose output voltage can drop by more than a third between idle and full load. However, other soft voltage sources, such as batteries, also have a wide output voltage range, which places corresponding demands on the coupling DC / DC converter. A soft voltage source, also known as a soft voltage source, is an electrical voltage source that has limited power supply capability and whose output voltage drops significantly under load. In contrast to an ideal voltage source, which supplies a constant voltage value regardless of the load, a soft voltage source has a higher internal resistance, which means the voltage decreases with increasing load.

[0005] Previously, the input voltage range of the DC / DC converter always had to be matched to the voltage range of the source. The transformer in the intermediate circuit then had to be dimensioned based on the ratio between the input voltage and the output voltage at full load. While some adjustment was possible in the output circuit using step-down (buck), step-up (boost), or buck-boost (inverse) converters, this also had its limitations in the converter's modulation range. Wide control ranges cannot be achieved this way. SUMMARY OF THE INVENTION

[0006] The object of the invention is to provide a wide-range DC-DC converter that overcomes the described disadvantages. A further object of the invention is to provide a corresponding method.

[0007] The object directed to a wide-range DC-DC converter is achieved by a wide-range DC-DC converter with a primary side and a secondary side, the primary side comprising a plurality of inverters that are electrically connected to a plurality of primary windings, wherein the primary windings either couple to a plurality of magnetic cores and the secondary side comprises a plurality of secondary windings that also couple to the plurality of magnetic cores and are each electrically connected to a rectifier, wherein the rectifiers are connected in series, or wherein the primary windings couple to a common magnetic core and the secondary side comprises a secondary winding that also couples to the common magnetic core and is electrically connected to a rectifier, or wherein the primary windings couple to a plurality of magnetic cores and the secondary side comprises a plurality of secondary windings,which also couple to the plurality of magnetic cores and which are connected in series and electrically connected to a rectifier, wherein the wide-range DC-DC converter comprises a controller connected to the inverters via control signals, and wherein primary winding numbers are different from one another and / or, if appropriate, secondary winding numbers are different from one another, resulting in different transmission ratios.

[0008] In contrast to previously used converters, which, for technical reasons, can only cover a limited voltage range, the wide-range DC-DC converter according to the invention can cover a voltage range several times larger. For example, several voltage sources (fuel cells, batteries, etc.) can be connected in series and, depending on the power requirement, either one or several voltage sources (fuel cells, batteries, etc.) can be operated. This simultaneously leads to an optimization of, for example, fuel consumption or an improvement in efficiency.

[0009] Previously, connecting multiple soft voltage sources in series was not possible, as this would have resulted in a very wide input voltage spread for the converter. A wider output voltage spread is also easily achieved with the present invention.

[0010] Furthermore, this interconnection of both the voltage sources (fuel cells, batteries, etc.) and the internal design of the wide-range DC-DC converter results in greater redundancy. If one source fails, the input voltage at the wide-range DC-DC converter drops, but the converter can compensate for this by varying the transmission units, i.e., the internal converters, over a wide range.

[0011] If one of the transmission units fails, the remaining transmission units can, depending on the type of fault, also compensate for this without the entire system having to be shut down.

[0012] If the primary windings have the same number of turns and the secondary windings have different numbers of turns, the full bridge that feeds the primary windings of a transformer can always be dimensioned the same and constructed with the same components.

[0013] In contrast, if the primary windings have different numbers of turns and feed into a common secondary winding via a common magnetic core, the individual voltages of the primary windings can be summed in the secondary winding. By varying the number of turns of the primary windings, different input voltages can be matched to a desired output voltage of the secondary winding. This allows the wide-range DC-DC converter to be used in applications with different voltage requirements.

[0014] If the individual voltages of the primary windings are summed in the secondary winding, a higher output voltage can be achieved. This can be useful in situations where a higher voltage is required than a single primary winding can provide. The use of multiple primary windings with different numbers of turns also allows greater flexibility in adapting the wide-range DC-DC converter's performance to the application requirements. This can, for example, help optimize the efficiency and performance of the wide-range DC-DC converter under different operating conditions. In some cases, the use of multiple primary windings with different numbers of turns can also help create a degree of redundancy in the system.If one of the primary windings fails, the wide-range DC-DC converter can still transfer energy through the remaining primary windings, minimizing the impact of a single failure. Finally, by splitting the input power across multiple primary windings, the overall performance of the wide-range DC-DC converter can be optimized. This can help improve the overall efficiency and performance of the wide-range DC-DC converter, especially in high-power or variable-load applications.

[0015] It is useful if the controller is connected to a measuring device for an input voltage and a measuring device for an output voltage, so that the wide-range DC-DC converter can be controlled depending on the measured input voltage level and a setpoint for the output voltage. Furthermore, the controller regulates the modulation, such as the pulse width and / or phase position, of the individual transmission units depending on the measured output voltage and, if applicable, a measured output current.

[0016] In an advantageous embodiment of the invention, the inverters each comprise a full bridge with four switching elements. A full bridge enables precise control of the output voltage because it has the ability to generate both positive and negative voltages. Full-bridge inverters generally produce lower harmonic distortion in the output signal than half-bridge inverters. This results in a cleaner output voltage and better power quality for connected devices. Full-bridge inverters are more efficient than other topologies because they can utilize the voltage across the entire input voltage, rather than using only half of the input voltage, as is the case with half-bridge inverters. Because four switching elements are used, the heat load on each switching element is lower, resulting in improved thermal performance and a longer switching element lifetime.

[0017] It is advantageous for the switching devices to be power semiconductors, particularly IGBTs (Insulated Gate Bipolar Transistors), GTOs (Gate Turn-Off Thyristors), or SiCs (Silicon Carbide Semiconductors). The choice of the correct switching device depends on the specific requirements and objectives of the application, such as the desired switching speed, dielectric strength, current carrying capacity, and thermal performance. IGBTs, GTOs, and SiC semiconductor devices each offer different advantages that make them suitable for different applications and power requirements.

[0018] It is advantageous if the inverters are electrically connected to a common DC bus. Using a common DC bus allows multiple inverters to operate in parallel and scale their power as needed. This makes it easier to adapt system power to different load requirements and allows for easier system expansion if additional inverters need to be added. Furthermore, with a common DC bus, multiple inverters can share the load in the event of a single inverter failure. This increases the overall reliability of the system and ensures that the connected loads continue to be supplied with power in the event of an inverter failure.Using a common DC bus can simplify installation and maintenance by requiring fewer separate components and wiring. This can also help reduce installation and maintenance costs. Finally, in systems with multiple energy sources, such as solar arrays or battery storage, a common DC bus enables the optimization of energy generation and distribution.

[0019] It is also advantageous if the rectifier(s) is / are connected to an output stage, where the output stage comprises a smoother, a buck converter, a boost converter, an inverting converter, or a combination thereof. After rectification, the output signal still contains residual ripple, which can have undesirable effects on connected devices. A smoothing stage, usually in the form of a capacitor, reduces these voltage fluctuations, providing a more stable DC voltage at the output. This improves power quality and protects sensitive devices from voltage fluctuations. The use of these converters improves the flexibility and efficiency of the system. They enable the voltage to be adapted to the requirements of the connected devices and contribute to improving overall system performance and reliability.

[0020] It is also advantageous if the rectifier is a bridge rectifier. A bridge rectifier offers several advantages over other rectifier types such as half-wave rectifiers. Bridge rectifiers enable full-wave rectification, in which both the positive and negative half-waves of the AC voltage are converted to DC voltage. This results in more efficient energy conversion and a higher average DC voltage at the output compared to half-wave rectification. The transformer power is also better utilized, resulting in higher power density and improved efficiency. Voltage ripple (voltage fluctuations) at the output of a bridge rectifier are also lower than with half-wave rectifiers. This results in a more stable DC voltage at the output and better power quality for connected devices.

[0021] The object directed to a method is achieved by a method for converting a direct voltage, wherein a first direct voltage is converted into a first alternating voltage, the first alternating voltage is transformed into a second alternating voltage and the second alternating voltage is converted into a second direct voltage, wherein the second direct voltage is set by selecting from a group of transmission units, each comprising an inverter, a primary winding, a magnetic core, a secondary winding and a rectifier, wherein the magnetic core, the secondary winding and the rectifier can belong to different transmission units, with different transformation ratios between the primary winding and the secondary winding,a transmission unit or a combination of several transmission units is selected and, if there is more than one secondary winding, these secondary windings themselves or rectifiers connected downstream of them are connected in series.

[0022] It is useful if the second DC voltage is controlled depending on measured values ​​of the first DC voltage and the second DC voltage.

[0023] It is advantageous to adjust the second DC voltage by controlling individual inverters with different pulse patterns and / or pulse widths. Using different pulse patterns and pulse widths allows inverters to operate more efficiently, as they can better adapt energy transfer and voltage conversion to the load requirements. This leads to lower energy loss and higher overall system efficiency. By individually controlling the inverters with different pulse patterns and pulse widths, the power and voltage of each inverter can also be precisely adjusted. This allows the system to be flexibly adapted to different operating conditions and load requirements without having to add additional hardware or components. Furthermore, this can help to optimize load distribution within the system.By individually adjusting the power and voltage of each inverter, this leads to better utilization of available resources. Furthermore, harmonics and electromagnetic interference can be reduced. This improves the overall performance of the system and minimizes interference with other electronic devices.

[0024] The same advantages arise when primary windings are controlled out of phase.

[0025] Advantageously, the second DC voltage is smoothed, for example, with a simple filter or a rectifier. It is useful if the second DC voltage is further adjusted to a target value during smoothing using a rectifier. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a first embodiment of the wide-range DC-DC converter according to the invention with equal numbers of turns on the primary side, Fig. Figure 2 shows a second embodiment of the wide-range DC-DC converter according to the invention with different numbers of turns on the primary side and a common secondary winding and Fig. 3 shows a third embodiment of the wide-range DC-DC converter according to the invention. DESCRIPTION OF THE EMBODIMENTS

[0026] Fig. 1 shows a first embodiment of the wide-range DC-DC converter 1 according to the invention, which solves the problem of wide control ranges by interconnecting several transmission units 16 with different transmission ratios.

[0027] All transmission units 16 each comprise an inverter 4, a transformer 17 and a rectifier 8.

[0028] The inverter 4 comprises a full bridge 12 with four switching elements 13 and is supplied with DC voltage from a common DC voltage rail 14. IGBTs (Insulated Gate Bipolar Transistors), GTOs (Gate Turn-Off Thyristors), SiCs (Silicon Carbide), or any other type of power semiconductor can be used as switching elements 13.

[0029] The transformer 17 comprises a primary winding 5 and a secondary winding 7, which are arranged on a common magnetic core 6.

[0030] The inverter 4 feeds the primary winding 5 of the transformer 17 and the secondary winding 7 of the transformer 17 feeds a rectifier 8, e.g. a bridge rectifier, which are then all connected in series.

[0031] The number of transmission units 16 can vary; it lies between two and an upper limit, which depends on the spread of the input voltage, the output voltage and the dimensioning of the transmission units 16.

[0032] In the embodiment of the Fig. 1, the primary windings 5 ​​of the transformers 17 all have the same number of turns. This ensures that the full bridge 12, which feeds the primary winding 5 of a transformer 17, can always be dimensioned the same and constructed with the same components.

[0033] The secondary windings 7 of the transformers 17 have different numbers of turns, allowing for different transformation ratios from the primary side 2 to the secondary side 3. For example, for one transformer 17, the winding ratio can be less than "1," which means the output voltage of the transformer 17 is lower than the input voltage. For one transformer 17, it is equal to "1," and for the other transformers 17, it is greater than "1," which means the voltage at the output of the transformer 17 is higher than at the input. However, other variations in the winding ratios can also be advantageous, depending on the requirements that the wide-range DC-DC converter 1 must meet.

[0034] A further advantage of the wide-range DC-DC converter 1 according to the invention is that not all transmission units 16 always have to be in operation simultaneously. Depending on the level of the input voltage and the required output voltage at the wide-range DC-DC converter 1, only one of the transmission units 16 can transmit the power, leaving the other transmission units 16 inactive, or two or more transmission units 16 can be used for transmission.

[0035] For example, with a high input voltage at the wide-range DC-DC converter 1, only one transmission unit 16 with a transformer 17 with a low transformation ratio can be active; with a lower input voltage, another transmission unit 16 is active; and if the input voltage drops even further, e.g., two or more transmission units 16 are active together. All variations of the transmission units 16 can be active until, for example, all transmission units 16 are active for transmission. The individual transmission units 16 can be controlled with different pulse patterns and / or pulse widths, and the transformers 17 can therefore supply different voltages. The output voltages of the rectifiers 8 are then added to form the total output voltage. The individual transmission units 16 can operate either out of phase or synchronously.

[0036] All series-connected rectifiers 8 feed an output stage 15, which can consist of either a simple smoothing circuit, a buck converter, a boost converter, a buck-boost converter, a combination thereof, or any other type of circuit for the transmission and smoothing of DC voltage. By using a converter 18 in the output stage 15, the output voltage can be further varied and, if necessary, more finely adjusted to the setpoint, or load changes can be more precisely compensated. In the exemplary embodiment of the Fig. 1, the converter 18 in the output stage 15 is a step-down converter.

[0037] According to the invention, the individual transmission units 16 and, if appropriate, also a converter 18 incorporated in the output stage 15 are controlled by a central controller 9. This controller 9 regulates the wide-range DC-DC converter 1 based on the measured values ​​of the input and output voltages (see measuring device 10 for an input voltage and measuring device 11 for the output voltage).

[0038] Based on the measured input voltage and the target output voltage, the controller 9 determines how many transmission units 16 and which transmission unit(s) 16 are used for power transmission. Furthermore, the controller 9 regulates the modulation, such as the pulse width and / or phase position, of the individual transmission units 16 and, if applicable, the converter 18 in the output stage 15, depending on the measured output voltage and the output current.

[0039] The controller 9 can, for example, consist of a processor that directly controls all switching elements 13. However, this processor can also control an FPGA (Field Programmable Gate Array), a GAL (Generic Array Logic), or another type of hard-coded logic, which then, via appropriate control units, controls the individual control elements according to the processor's specifications.

[0040] The control 9 can also be carried out by several processors which communicate internally and then take over different functions of the wide-range DC-DC converter 1 separately, so that, for example, each transmission unit 16 and the output stage 15 is controlled by its own processor.

[0041] Combinations or variations of these control options are also conceivable.

[0042] Fig. Figure 2 shows a further embodiment of the wide-range DC-DC converter 1 according to the invention. Here, all transmission units 16 each feed their own primary winding 5 of a transformer 17 with a common magnetic core 6 and a common secondary winding 7. All primary windings 5 ​​have different numbers of turns, so that different transformation ratios can be realized from the primary side 2 to the secondary side 3. The individual voltages of the primary windings 5 ​​are summed in the secondary winding 7.

[0043] In addition, the primary windings 5 ​​can also be controlled with a phase shift, allowing the voltage on the secondary side 3 to be further varied. The secondary winding 7 feeds a rectifier 8, which supplies the output stage 15. The individual transmission units 16 can operate either with a phase shift or with a clock synchronization.

[0044] Fig.Figure 3 shows a third embodiment of the wide-range DC-DC converter 1 according to the invention. Here, several individual transformers 17, whose secondary windings 7 are connected in series, feed a common rectifier 8. In this embodiment, the different transformation ratios of the transformers 17 fed by the transformation units 16 can be realized in different ways, either by different numbers of turns of the primary windings 5 ​​with the same number of turns of the secondary windings 7, by different numbers of turns of the secondary windings 7 with the same number of turns of the primary windings 5, or by different combinations of the numbers of turns of the primary windings 5 ​​and secondary windings 7. List of reference symbols 1 wide-range DC-DC converter 2 Primary side 3 Secondary side 4 inverters 5 Primary winding 6 magnetic core 7 Secondary winding 8 rectifiers 9 Control 10 Measuring device for an input voltage 11 Measuring device for an output voltage 12 full bridge 13 switching elements 14 DC rail 15 Output stage 16 transmission unit 17 Transformer 18 converters in the output stage

Claims

[1] Wide-range DC-DC converter (1) with a primary side (2) and a secondary side (3), the primary side (2) comprising several inverters (4) which are electrically connected to several primary windings (5), wherein the primary windings (5) either couple to a plurality of magnetic cores (6) and the secondary side (3) comprises a plurality of secondary windings (7) which also couple to the plurality of magnetic cores (6) and are each electrically connected to a rectifier (8), wherein the rectifiers (8) are connected in series, or wherein the primary windings (5) couple to a common magnetic core (6) and the secondary side (3) comprises a secondary winding (7) which also couples to the common magnetic core (6) and is electrically connected to a rectifier (8), or wherein the primary windings (5) couple to a plurality of magnetic cores (6) and the secondary side (3) comprises a plurality of secondary windings (7) which also couple to the plurality of magnetic cores (6) and which are connected in series and electrically connected to a rectifier (8), wherein the wide-range DC-DC converter (1) comprises a controller (9) connected to the inverters (4) via control signals, characterized by that the number of primary turns is different from one another and / or the number of secondary turns is different from one another, resulting in different transmission ratios. [2] The wide-range DC-DC converter (1) according to claim 1, wherein the controller (9) is connected to a measuring device (10) for an input voltage and to a measuring device (11) for an output voltage. [3] The wide-range DC-DC converter (1) according to one of claims 1 or 2, wherein the inverters (4) each have a full bridge (12) with four switching elements (13). [4] The wide-range DC-DC converter (1) according to claim 3, wherein the switching elements (13) are power semiconductors, in particular IGBTs, GTOs or SiCs. [5] The wide-range DC-DC converter (1) according to one of the preceding claims, wherein the inverters (4) are electrically connected to a common DC voltage rail (14). [6] The wide-range DC-DC converter (1) according to any one of the preceding claims, wherein the rectifier(s) (8) is / are connected to an output stage (15), wherein the output stage (15) comprises a smoother, a buck converter, a boost converter, an inverting converter or a combination thereof and is connected to the controller (9). [7] The wide-range DC-DC converter (1) according to one of the preceding claims, wherein the rectifier (8) is a bridge rectifier. [8] Method for converting a direct voltage, wherein a first direct voltage is converted into a first alternating voltage, the first alternating voltage is transformed into a second alternating voltage and the second alternating voltage is converted into a second direct voltage, characterized bythat the second direct voltage is set by selecting one transmission unit (16) or a combination of several transmission units (16) from a group of transmission units (16), each comprising an inverter (4), a primary winding (5), a magnetic core (6), a secondary winding (7) and a rectifier (8), wherein the magnetic core (6), the secondary winding (7) and the rectifier (8) can belong to different transmission units (16), with different transformation ratios between the primary winding (5) and the secondary winding (7), and in the case of more than one secondary winding (7), these secondary windings (7) themselves or rectifiers (8) connected downstream of them are connected in series. [9] Method according to claim 8, wherein the second DC voltage is controlled in dependence on measured values ​​of the first DC voltage and the second DC voltage. [10] Method according to one of claims 8 or 9, wherein the second DC voltage is adjusted by controlling individual inverters (4) with different pulse patterns and / or pulse widths. [11] Method according to one of claims 8 to 10, wherein primary windings (5) are controlled in a phase-shifted manner. [12] Method according to one of claims 8 to 11, wherein the second DC voltage is smoothed. [13] Method according to claim 12, wherein the second DC voltage is further adjusted to a desired value during smoothing by means of a rectifier (8).

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