DE102019208207A1 - DC / DC converter for converting a direct voltage in the medium voltage range into a direct voltage in the low voltage range - Google Patents

Abstract

DC / DC converter for converting a direct voltage in the medium voltage range into a direct voltage in the low voltage range, comprising - a series connection of a plurality of first voltage divider modules, the voltage divider modules being constructed identically, - an end module that is connected in series with the voltage divider modules, the A series of voltage divider modules and an end module is connected between the poles of the DC voltage in the medium voltage range, - a transformer circuit whose input connections are connected to the output connections of the end module, - a rectifier whose input contacts are connected to the output connections of the transformer circuit, - a step-down converter that is connected to the output contacts on the input side of the rectifier is connected, wherein the voltage divider modules and the end module are designed such that there is a reduced DC voltage at the output connections of the end module, which is at most half as large as wi e is the DC voltage in the medium voltage range.

Description

The invention relates to a DC voltage converter designed for converting a DC voltage in the medium voltage range, i.e. in an approximate range of 10 kV to 150 kV into a DC voltage for supplying devices in the low voltage range of approx. 1 V to 50 V.

In power supply systems that are based on a high DC voltage in the range of around 10 kV to 150 kV, internationally known as MVDC, it is necessary to operate a number of electronic monitoring, control and safety circuits. These circuits, which are now digitally implemented, have to be supplied with low supply voltages, but with currents in the single and multi-digit ampere range. This supply, whose DC voltage values are mostly between 1.8 V and 48 V, is called auxiliary power supply. auxiliary power supply.

Since the electrical source for the auxiliary power supply is the high DC voltage, familiar solutions with transformers are ruled out. The big difference between the DC voltages, for example U _Netz = 40 kV and U _auxiliary = 12 V, are useful for DC voltage converters, also called DC / DC converters or DC / DC converters, only in several stages, i.e. in the form of a cascade, to bridge. Several stages are also necessary for reasons of the limited dielectric strength of the available switching transistors. These stages must be able to convert over a very wide range of current values, from very small currents at the high-voltage input to medium currents at the output, with satisfactory efficiency. For example, assuming 100W auxiliary power, the input current (@ 10kV =) of the converter cascade is only about 10mA, but at the end (@ 12V =) it is 8.3A.

The large difference between the DC voltages, for example U _Netz = 40 kV and U _aux = 12 V, poses a challenge for auxiliary power supplies because the switching transistors available have a limited dielectric strength. Furthermore, the DC / DC converter must be able to convert from the resulting very small currents at the high voltage input to medium currents at the output with a satisfactory degree of efficiency, for example with 100 W auxiliary power the input current at 10 kV is only about 10 mA, at the end of 12 V but already 8.3 A.

Another difficulty is the start-up of the DC-DC converter. referred to as "black start capability". It is disadvantageous if the converter requires its own energy source, for example a battery. If one assumes that there is no other energy source apart from the medium direct voltage (MVDC), then the driver and control power in the low watt range must be made available autonomously. A separate high-voltage switch and power losses in the kW range should be avoided by using a simple voltage divider.

It is the object of the present invention to specify a DC voltage converter which solves the problems mentioned at the beginning. This object is achieved by a DC voltage converter with the features of claim 1.

The DC / DC converter according to the invention is designed to convert a direct voltage in the medium voltage range into a direct voltage in the low voltage range. It comprises a series circuit made up of a plurality of first voltage divider modules, the voltage divider modules being constructed in particular in the same way, and an end module which is connected in series with the voltage divider modules. The series of voltage divider modules and end module is connected between the poles of the DC voltage in the medium voltage range.

The DC / DC converter further comprises a transformer and a rectifier connected downstream of the transformer. Finally, there is a step-down converter or step-up converter, which is connected on the input side to the output contacts of the rectifier.

The voltage divider modules and the end module are designed in such a way that a reduced DC voltage applied to the end module is at most half as large as the DC voltage in the medium voltage range.

This advantageously provides a modular structure in which an adaptation to the level of the direct voltage in the medium voltage range is possible by adapting the number of voltage divider modules used. Furthermore, the conversion of the direct voltage takes place efficiently, i.e. with low power dissipation, although the ratio of input voltage to output voltage is at least 150, in many cases even 1000 and more.

The voltage divider modules can also be referred to as charge pump modules because their function is based on that of a charge pump.

What is particularly advantageous about the solution according to the invention is that it can be used without high or medium voltage transformers with, for example, UmaxTr = 10kV, without high-voltage capacitors and switching transistors in the low kV range (for example UmaxS = 1, 7kV) in component procurement, production and design is much easier.

• - Die Spannungsteilermodule und das Endmodul können jeweils eine Halbbrücke mit zwei steuerbaren Leistungshalbleitern aufweisen, wobei die Außenanschlüsse der Halbbrücke einen ersten und zweiten Pol des Moduls bilden. Des Weiteren umfassen sie dann eine Serienschaltung zweier Dioden, die zwischen ersten und zweiten Pol geschaltet ist, eine zwischen den ersten und zweiten Pol geschaltete Widerstandsschaltung mit einem Widerstand oder zwei seriellen Widerständen und eine zwischen den ersten und zweiten Pol geschaltete Kondensatorschaltung mit einem Kondensator oder zwei seriellen Kondensatoren. Die Kondensatorschaltung, die Serienschaltung der Dioden, die Widerstandsschaltung und die Halbbrücke sind also mit anderen Worten parallel geschaltet. Dadurch ist dem Grundsatz nach ein Ladungspumpenaufbau gegeben, der im einzelnen noch anpassbar ist und das Stapeln der Spannungsteilermodule zulässt.
• - Der Gleichrichter kann ein Dioden-Brückengleichrichter mit vier Dioden sein. Dadurch ist ein einfacher, verlustarmer Aufbau gegeben.
• - Die verringerte Gleichspannung kann kleiner sein als die Gleichspannung im Mittelspannungsbereich geteilt durch die Anzahl der Spannungsteilermodule. Werden beispielsweise 7 Spannungsteilermodule bei einer Mittelspannung von 10 kV verwendet, ist die verringerte Gleichspannung, die an den Ausgängen des Endmoduls anliegt, kleiner als 10 kV / 7, also kleiner als etwa 1400 V. Bevorzugt teilt sich der Spannungsabfall gleichmäßig auf die Spannungsteilermodule und das Endmodul auf, so dass die verringerte Gleichspannung in etwa gleich der Mittelspannung geteilt durch die Anzahl der Spannungsteilermodule plus eins ist. Im gegebenen Beispiel wäre dann die verringerte Gleichspannung 10 kV / (7+1) = 1250 V. Die Kaskade aus den Spannungsteilermodulen und dem Endmodul transformiert die Mittelspannung also bevorzugt entsprechend der Anzahl der Spannungsteilermodule herunter. Eine größere Mittelspannung kann also ohne bauliche Änderung der Spanteilermodulen in dieselbe verringerte Gleichspannung transformiert werden. Beträgt die Gleichspannung im Mittelspannungsbereich beispielsweise 20 kV, kann eine verringerte Gleichspannung also erreicht werden, indem 15 Spannungsteilermodule verwendet werden.

Advantageous refinements of the DC / DC converter according to the invention emerge from the claims dependent on claim 1. The embodiment according to claim 1 can be combined with the features of one of the subclaims or with those from several subclaims. Accordingly, the following features can also be provided:

• The voltage divider modules and the end module can each have a half bridge with two controllable power semiconductors, the external connections of the half bridge forming a first and second pole of the module. Furthermore, they then comprise a series circuit of two diodes connected between the first and second pole, a resistor circuit connected between the first and second pole with one resistor or two series resistors and one capacitor circuit connected between the first and second pole with one capacitor or two serial capacitors. In other words, the capacitor circuit, the series circuit of the diodes, the resistor circuit and the half bridge are connected in parallel. In principle, this results in a charge pump structure which can still be individually adapted and which allows the voltage divider modules to be stacked.
• - The rectifier can be a diode bridge rectifier with four diodes. This results in a simple, low-loss structure.
• - The reduced DC voltage can be less than the DC voltage in the medium voltage range divided by the number of voltage divider modules. For example, if 7 voltage divider modules are used at a medium voltage of 10 kV, the reduced DC voltage that is applied to the outputs of the end module is less than 10 kV / 7, i.e. less than about 1400 V. The voltage drop is preferably divided equally between the voltage divider modules and the End module so that the reduced DC voltage is roughly equal to the mean voltage divided by the number of voltage divider modules plus one. In the example given, the reduced DC voltage would then be 10 kV / (7 + 1) = 1250 V. The cascade of the voltage divider modules and the end module thus preferably down-transforms the medium voltage according to the number of voltage divider modules. A higher mean voltage can therefore be transformed into the same reduced DC voltage without structural changes to the chip splitter modules. If the DC voltage in the medium voltage range is 20 kV, for example, a reduced DC voltage can be achieved by using 15 voltage divider modules.

• - Bei jedem der Spannungsteilermodule kann der Potentialpunkt zwischen den Leistungshalbleitern der Halbbrücke mit dem Potentialpunkt zwischen den Dioden verbunden sein und einen dritten Pol des jeweiligen Spannungsteilermoduls bilden. Weiterhin kann bei jedem der Spannungsteilermodule der dritte Pol mit dem ersten Anschluss eines Kondensators verbunden sein und dessen zweiter Anschluss einen vierten Pol des jeweiligen Spannungsteilermoduls bilden. Die Serienschaltung oder Stapelung der Spannungsteilermodule wird dann dadurch realisiert, dass der erste Pol eines Spannungsteilermoduls mit dem zweiten des folgenden Spannungsteilermoduls verbunden ist und ebenso der dritte Pol der Spannungsteilermoduls mit dem vierten Pol des folgenden Spannungsteilermoduls.
• - Zwischen dem dritten und ersten Pol der Spannungsteilermodule kann ein Widerstand vorhanden sein.
• - Die in den Spannungsteilermodulen verwendeten Dioden können Schottky-Dioden sein.
• - Der erste und zweite Pol des Endmoduls sind bevorzugt die Ausgangsanschlüsse des Endmoduls, die mit der Transformatorschaltung verbunden sind. Da an diesen Ausgangsanschlüssen eine Gleichspannung anliegt, umfasst die Transformatorschaltung bevorzugt einen Wechselrichter, der eingangsseitig mit den Ausgangsanschlüssen des Endmoduls verbunden ist.
• - Es ist in einer besonderen Ausgestaltung möglich, dass jedes der Spannungsteilermodule eine erste, zweite und dritte Wicklung umfasst, wobei die Anschlüsse der ersten Wicklung einen dritten und vierten Pol des jeweiligen Spannungsteilermoduls bilden, die Anschlüsse der dritten Wicklung einen fünften und sechsten Pol des jeweiligen Spannungsteilermoduls bilden, die Kondensatorschaltung zwei serielle Kondensatoren umfasst und ein erster Anschluss der zweiten Wicklung mit dem Potentialpunkt zwischen den Leistungshalbleitern der Halbbrücke verbunden ist und der zweite Anschluss der zweiten Wicklung mit dem Potentialpunkt zwischen den seriellen Kondensatoren verbunden ist. Die Wicklungszahlen der Wicklungen sind dabei so gewählt, dass eine Wechselspannung, die durch die Leistungshalbleiter der Halbbrücken der Spannungsteilermodule erzeugt wird, stufenweise herabtransformiert wird.
• - Das Endmodul kann eine Kondensatorschaltung mit zwei seriellen Kondensatoren umfassen. Dann bildet der Potentialpunkt zwischen den Kondensatoren der Kondensatorschaltung den ersten Ausgangsanschluss des Endmoduls und der Potentialpunkt zwischen den Leistungshalbleitern bildet den zweiten Ausgangsanschluss des Endmoduls. Da das Endmodul durch die Ansteuerung der Leistungshalbleiter der Halbbrücke im Endmodul eine Wechselspannung zwischen den Ausgangsanschlüssen erzeugt, kann der Wechselrichter in der Transformatorschaltung bei dieser Ausgestaltung entfallen.
• - Die Spannungsteilermodule und das Endmodul können jeweils eine Ansteuerschaltung für die Leistungshalbleiter umfassen, die zur elektrischen Versorgung mit dem ersten und zweiten Pol des Moduls verbunden ist. Die elektrische Versorgung erfolgt also aus dem jeweiligen auf das Modul entfallenden Teil der Gleichspannung im Mittelspannungsbereich. Eine weitere, externe Versorgung und entsprechende Isolierung und Sicherstellung der Verfügbarkeit sind vorteilhaft nicht erforderlich. Besonders vorteilhaft ist dabei, dass die Funktion der Ladungspumpen keine Regelung erfordert, sondern lediglich eine Ansteuerung der Leistungshalbleiter mit einer rechteckartigen Steuerspannung, mit der die beiden Leistungshalbleiter eines Moduls mit 180° Phasenversetzung angeschaltet werden. Es ist daher keine Verbindung mit einer übergeordneten Steuerung nötig, die wieder geeignete Isoliermaßnahmen erfordert.
• - Die Ansteuerschaltung der Module kann einen selbstanlaufenden Oszillator umfassen, ausgestaltet, über einen Transformator und einen nachgeschalteten Gleichrichter eine Ansteuerspannung für die Steueranschlüsse der Leistungshalbleiter bereitzustellen. Der Oszillator kann beispielsweise als Gate-Schaltung aufgebaut sein. Vorteilhaft wird dadurch vermieden, dass für das Anlaufen, also den „black start“ des Gleichspannungswandlers eine besondere Ansteuerung nötig ist oder eigene Energie vorgehalten werden muss, beispielsweise in Form einer Batterie.
• - Die Highside-Leistungshalbleiter der Spannungsteilermodule und des Endmoduls schalten bevorzugt gleichzeitig ein und aus. Ebenso schalten die Lowside-Leistungshalbleiter der Spannungsteilermodule und des Endmoduls bevorzugt gleichzeitig ein und aus. Dafür können die Gate-Treiber transformatorisch gekoppelt sein.

The current term MVDC encompasses a wide voltage range, since the new networks are only being planned or set up, so that the necessary cascade height, i.e. the number of stages, may vary greatly depending on the application. Not only are DC island networks to be dimensioned in large buildings and remote settlements, but also mobile DC networks, for example in ships, aircraft and land vehicles. The voltage can advantageously be transformed for all networks of the applications mentioned by using an adapted number of voltage divider modules without these having to be structurally changed.

• - In each of the voltage divider modules, the potential point between the power semiconductors of the half bridge can be connected to the potential point between the diodes and form a third pole of the respective voltage divider module. Furthermore, the third pole of each of the voltage divider modules can be connected to the first connection of a capacitor and its second connection can form a fourth pole of the respective voltage divider module. The series connection or stacking of the voltage divider modules is then implemented in that the first pole of a voltage divider module is connected to the second of the following voltage divider module and likewise the third pole of the voltage divider module to the fourth pole of the following voltage divider module.
• - A resistor can be present between the third and first pole of the voltage divider modules.
• - The diodes used in the voltage divider modules can be Schottky diodes.
• - The first and second pole of the end module are preferably the output connections of the end module, which are connected to the transformer circuit. Since a DC voltage is applied to these output connections, the transformer circuit preferably comprises an inverter which is connected on the input side to the output connections of the end module.
• - It is possible in a special embodiment that each of the voltage divider modules comprises a first, second and third winding, the connections of the first winding forming a third and fourth pole of the respective voltage divider module, the connections of the third winding a fifth and sixth pole of the respective Voltage divider module form the capacitor circuit two in series Comprises capacitors and a first connection of the second winding is connected to the potential point between the power semiconductors of the half bridge and the second connection of the second winding is connected to the potential point between the series capacitors. The number of turns of the windings is selected so that an alternating voltage that is generated by the power semiconductors of the half-bridges of the voltage divider modules is stepped down.
• - The end module can comprise a capacitor circuit with two capacitors in series. Then the potential point between the capacitors of the capacitor circuit forms the first output connection of the end module and the potential point between the power semiconductors forms the second output connection of the end module. Since the end module generates an alternating voltage between the output connections by controlling the power semiconductors of the half bridge in the end module, the inverter in the transformer circuit can be omitted in this embodiment.
• The voltage divider modules and the end module can each include a control circuit for the power semiconductors, which is connected to the first and second pole of the module for the electrical supply. The electrical supply therefore comes from the respective part of the DC voltage in the medium voltage range that is allotted to the module. A further, external supply and corresponding insulation and ensuring availability are advantageously not required. It is particularly advantageous that the function of the charge pumps does not require any regulation, but only activation of the power semiconductors with a square-wave control voltage with which the two power semiconductors of a module are switched on with a 180 ° phase shift. There is therefore no need to connect to a higher-level control system that again requires suitable insulation measures.
• The control circuit of the modules can comprise a self-starting oscillator configured to provide a control voltage for the control connections of the power semiconductors via a transformer and a downstream rectifier. The oscillator can for example be constructed as a gate circuit. This advantageously avoids the need for a special control or own energy, for example in the form of a battery, for the start-up, ie the “black start” of the DC voltage converter.
• - The high-side power semiconductors of the voltage divider modules and the end module preferably switch on and off at the same time. Likewise, the lowside power semiconductors of the voltage divider modules and the end module preferably switch on and off at the same time. For this purpose, the gate drivers can be coupled in a transformer.

Further advantages and features can be found in the following description of exemplary embodiments with reference to the figures. In the figures, the same reference symbols denote the same components and functions.

• 1 ein Blockschaltbild einer ersten Ausführungsform für einen Gleichspannungswandler von Mittelspannung zu Niederspannung,
• 2 ein elektrisches Schaltbild eines Ausschnitts der ersten Ausführungsform für den Gleichspannungswandler,
• 3 ein Blockschaltbild einer zweiten Ausführungsform für einen Gleichspannungswandler von Mittelspannung zu Niederspannung,
• 4 ein elektrisches Schaltbild eines Ausschnitts der zweiten Ausführungsform für den Gleichspannungswandler,
• 5 ein Schaltbild einer dritten Ausführungsform für einen Gleichspannungswandler von Mittelspannung zu Niederspannung,
• 6 ein elektrisches Schaltbild für einen selbstanlaufenden Oszillator zur Versorgung von Leistungshalbleitern in den Gleichspannungswandlern,
• 7 Spannungs- und Leistungsverläufe für die zweite Ausführungsform des Gleichspannungswandlers,
• 8 simulierte Verläufe von Spannung, Leistung und Strom im Zuge des Anlaufens des Oszillators.

Show it:

• 1 a block diagram of a first embodiment for a DC voltage converter from medium voltage to low voltage,
• 2 an electrical circuit diagram of a section of the first embodiment for the DC voltage converter,
• 3 a block diagram of a second embodiment for a DC voltage converter from medium voltage to low voltage,
• 4th an electrical circuit diagram of a section of the second embodiment for the DC voltage converter,
• 5 a circuit diagram of a third embodiment for a DC voltage converter from medium voltage to low voltage,
• 6th an electrical circuit diagram for a self-starting oscillator for supplying power semiconductors in the DC voltage converters,
• 7th Voltage and power curves for the second embodiment of the DC voltage converter,
• 8th simulated curves of voltage, power and current in the course of starting the oscillator.

1 shows a block diagram for a first embodiment for a DC voltage converter 100 from a medium voltage of around 10 kV to a low voltage of 25 V, with the low voltage being used to supply electronic devices that are operated in the area of a power supply at medium voltage level.

The medium voltage of 10 kV is applied as input voltage to the DC voltage converter 100 at. The DC / DC converter 100 includes a first section 102 and a second section 104 .

The first paragraph 102 includes seven voltage divider modules 1061 ... 1067 and an end module 108 that are connected in the form of a cascade or a stack, i.e. in the form of a series circuit, between the poles of the input voltage. The voltage divider modules 1061 ... 1067 and the end module 108 are constructed in such a way that they divide the applied input voltage as evenly as possible. This is the voltage across the end module 108 drops, roughly equal to one eighth of the input voltage, ie 1.25 kV in this example. This tension becomes the second section 104 of the DC / DC converter 100 passed on and is further transformed there.

An excerpt from the first section 102 is in 2 shown more precisely as electrical circuit diagram. The voltage divider modules 1061 ... 1067 are constructed identically to each other and each include a half bridge made of a first and a second power semiconductor 10611 ... 10671 , 10612 ... 10672 , a series connection of two Schottky diodes 10613 ... 10673 , 10614 ... 10674 , a resistor 10615 ... 10675 and a voltage divider capacitor 10616 ... 10676 that are connected in parallel to each other. The two connection points of this parallel connection form a first and a second pole of the voltage divider modules 1061 ... 1067 over which the voltage divider modules 1061 ... 1067 are connected in series with one another.

The midpoint of the half bridge is with the midpoint of the series connection of the Schottky diodes 10613 ... 10673 connected and forms a third pole. About a second resistance 10617 ... 10677 is the third pole with the respective lower pole of the voltage divider modules 1061 ... 1067 connected. Furthermore, the third pole is connected to a second capacitor 10618 ... 10678 connected, the second connection of which is a fourth pole of the voltage divider modules 1061 ... 1067 forms. The voltage divider modules 1061 ... 1067 are also connected in series via the third and fourth pole. The first and third pole are associated with the higher voltage side.

The end module 108 is largely like the voltage divider modules 1061 ... 1067 constructed, so it comprises a half-bridge made of two power semiconductors connected in parallel 1081 , 1082 , a series of two Schottky diodes 1083 , 1084 , a resistance 1085 and a voltage divider capacitor 1086 . The end module 108 does not include the second resistor and not the second capacitor of the voltage divider modules 1061 ... 1067 . The first and second pole of the end module 108 form the output connections of the first section 102 .

The power semiconductors 1081 , 1082 are in all voltage divider modules 1061 ... 1067 controlled in such a way that they switch on alternately with a duty cycle of <= 50%, i.e. both switches are never conductive.

The second section 104 includes a transformer circuit 110 and a buck converter 112 . The transformer circuit 110 comprises an inverter circuit with a full bridge made of four power semiconductors, which convert the direct voltage of 1.25 kV into an alternating voltage. The power semiconductors of the full bridge are controlled in a simple manner so that the resulting alternating voltage has a rectangular shape without pulse width modulation. This alternating voltage is fed into a first winding of a transformer, which reduces the voltage to about 100 V on its second winding. There the AC voltage is converted into a DC voltage of around 100 V with a bridge rectifier, which is the case with the buck converter 112 on the input side.

In the buck converter 112 the DC voltage is reduced to a voltage level of, for example, 25 V. The resulting voltage serves as a supply voltage for downstream electronics such as monitoring, control and safety circuits for the voltage supply at medium voltage level.

The high DC voltage of 10 kV is reduced to 1.25 kV via modular half-bridge charge pumps and then reduced to around 100V via a galvanically isolated DC voltage converter. This is followed by a non-isolated step-down converter which, well regulated, outputs a stabilized voltage of + 25V.

3 shows a block diagram for a second embodiment for a DC voltage converter 200 from a medium voltage of 7.5 kV to a low voltage of 25 V. The medium voltage of 7.5 kV is the input voltage on the DC voltage converter 200 at.

Like the DC / DC converter 100 includes the DC-DC converter 200 a first section 102 and a second section 104 .

The first paragraph 102 includes five voltage divider modules 1061 ... 1065 and an end module 208 that are connected in the form of a cascade or a stack, i.e. in the form of a series circuit, between the poles of the input voltage. The voltage divider modules 1061 ... 1065 and the end module 108 are constructed in such a way that they divide the applied input voltage as evenly as possible. This is the voltage across the end module 108 drops, roughly equal to one sixth of the input voltage, ie 1.25 kV in this example. This tension becomes the second section 104 of DC-DC converter 200 passed on and is further transformed there.

The voltage divider modules 1061 ... 1065 of the DC / DC converter 200 correspond to those of the DC / DC converter 100 according to the 1 and 2 . The structure of the end module 208 but differs from the end module 108 out 2 . The end module 208 is in 4th shown more precisely as electrical circuit diagram.

The end module 208 comprises a half-bridge of two power semiconductors connected in parallel 1081 , 1082 , a series of two Schottky diodes 1083 , 1084 , a resistance 1085 and a series of two voltage divider capacitors 2081 , 2082 . The two connection points of this parallel connection form a first and a second pole of the end module 208 off, the top, first pole with the second pole of the next following voltage divider module 1061 ... 1065 connected is.

The midpoint of the half bridge is with the midpoint of the series connection of the Schottky diodes 1083 , 1084 connected and forms a third pole, which is connected to the fourth pole of the next following voltage divider module 1061 ... 1065 connected is.

Between the third pole and the midpoint between the two voltage divider capacitors 2081 , 2082 is a first winding of a galvanically isolating and stepping-down transformer 2083 switched. Its second winding provides the output connections of the end module 208 available through which the connection to the second section 104 he follows. The turns ratio of the turns of the transformer 2083 is selected in such a way that the applied square-wave alternating voltage is reduced from approx. 600 V _peak to approx. 100 V _peak .

The end module 208 So works here as an inverter that controls the transformer 2083 supplied with a square-wave alternating voltage.

4th also shows that the output connections of the end module 208 as the input of a diode bridge rectifier 210 are connected, the four Schottky diodes 2101 ... 2104 as well as a smoothing capacitor 2105 includes. The incoming AC voltage of 100 V is converted to a DC voltage of around 100 V here. The output terminals of the diode bridge rectifier 210 are with a buck converter 112 connected to that of the DC / DC converter 100 corresponds.

In the buck converter 112 the DC voltage is reduced to a voltage level of, for example, 25 V. The resulting voltage serves as a supply voltage for downstream electronics such as monitoring, control and safety circuits for the voltage supply at medium voltage level.

As with the DC / DC converter 100 the DC voltage of 7.5 kV is reduced to 1.25 kV via modular half-bridge charge pumps and already in the end module via the transformer 2083 with galvanic isolation reduced to about 100 V ~. The rectification is followed by a non-isolated buck converter 112 , which outputs a stabilized voltage of + 25V in a well-regulated manner.

It can be seen from the first two exemplary embodiments that the structure of the DC voltage converter 100 , 200 is modular in such a way that other input voltages can be transformed with simple changes to the structure. To adapt to the input voltage, only the number of voltage divider modules used has to be determined 1061 ... 1067 adjusted so that the voltage at the output of the end module 108 , 208 again around 1.25 kV in the case of the end module 108 and 100 V ~ in the case of the end module 208 corresponds. These voltages are only exemplary and the circuit can also be implemented with other intermediate voltage levels.

If a medium voltage of 25 kV is to be used as the input voltage and reduced to a voltage of 10 V, for example, then the intermediate voltage at the output of the end module 108 a voltage of 500 V can be used. There are 49 voltage divider modules for this 1061 ... 1067 required in addition to the end module 108 , reducing the voltage at the output of the end module 108 is reduced to 1/50 of the input voltage. The galvanically isolated DC voltage converter 110 reduces this voltage to approx. 40 V and the buck converter 112 to the desired 10 V. The structure of the end module 108 or the individual voltage divider module 1061 ... 1067 does not have to be changed for this. Also the DC converter 110 and the buck converter 112 stay unchanged. Only the number of voltage divider modules is advantageous 1061 ... 1067 changed.

5 shows a third embodiment for a DC-DC converter 300 from a medium voltage of 7.5 kV to a low voltage of 25 V. Like the DC voltage converter 200 includes the DC-DC converter 300 a first section 102 and a second section 104 , with the same as with the DC-DC converter 200 the second section 104 comprises a diode bridge rectifier and a downstream buck converter.

The first paragraph 102 includes five voltage divider modules 3061 ... 3065 and an end module 308 that are cascaded between the poles of the input voltage. The voltage divider modules 3061 ... 3065 and the end module 308 are constructed in such a way that they divide the applied input voltage as evenly as possible. This is the voltage across the end module 308 drops, again roughly equal to one sixth of the input voltage, ie 1.25 kV in this example. This tension becomes the second section 104 of the DC / DC converter 300 passed on and is further transformed there.

The voltage divider modules 3061 ... 3065 of the DC / DC converter 300 comprise a half bridge connected in parallel 30611 from two power semiconductors, one series 30612 from two Schottky diodes, one series 30613 from two resistors and a series 30614 from two voltage divider capacitors. The two connection points of this parallel connection form a first and a second pole, via which the voltage divider modules 3061 ... 3065 are connected in series.

Between the connected centers of the half bridge 30611 and the series 30612 of two Schottky diodes and the connected centers of the series 30613 from two resistors and the series 30614 A winding 3061A is connected from two voltage divider capacitors. Two further windings 3061B, C are coupled to these, the windings 3061A, B, C together forming a step-down isolating transformer with two coupling windings. The connections of the second winding 3061B form a third and fourth pole of the voltage divider module 3061 ... 3065 and the connections of the third winding 3061C a fifth and sixth pole of the voltage divider module 3061 ... 3065 . For the parallel connection of the voltage divider modules 3061 ... 3065 are the respective third and fifth pole as well as the fourth and sixth pole of two adjacent voltage divider modules 3061 ... 3065 connected.

The structure of the end module 308 in this case corresponds to the structure of the voltage divider modules 3061 ... 3065 . The connections of the third winding 3061C form the output connections for the first section 102 . There is a galvanic separation already in the end module 308 is present, a diode bridge rectifier is sufficient in the second section 210 out.

The voltage divider modules 3061 ... 3065 So here they all work as inverters, so that the alternating voltage generated per step of about 600 V _peak (rectangular) can be applied to the respective neighboring isolating transformer via a galvanically isolating, step-down isolating transformer with about 100 V _peak . All transformers are therefore coupled to one another, the power of the higher half-bridge stages in the cascade is transferred down to the output.

6th shows a circuit diagram for a self-starting harmonic oscillator 60 in gate circuit with a 1700V SiC FET high-voltage switching transistor 61. Through rigid ohmic current limitation with the resistor 62 (170kOhm) the current can reach a maximum of only 7.4mA. In the dimensioning shown, the oscillation frequency is 550 kHz, the HV operating current is 3.8 mA, and the steady sine oscillation amplitude of the drain voltage of the linearly operated switching transistor 61 lies quite precisely, touching, between - 0 V (GND) and +1250 V, this is determined by the limiter diodes 63 ... 65 forced. The two generated auxiliary voltages U _outH and U _outL are 18.7V, the power is 850mW each. The efficiency of this oscillator 60 is 35% over a wide design range. The level of the generated direct power depends on the resistance 62 ; it can, assuming other transformer windings, be distributed to one, two or more outputs with any voltage. The connecting ferrite magnetic core 70 of all 4 windings 66 ... 69 is shown as a dashed line.

The oscillator 60 is in each of the voltage divider modules 1061 ... 1067 , 3061 ... 3065 and in each of the end modules 108 , 208 , 308 available. Due to their low current consumption of a few mA, with compensating ohmic characteristics, these oscillators carry 60 for voltage balancing of the series voltage divider capacitors of the voltage divider modules 1061 ... 1067 , 3061 ... 3065 at. Since they have a transformer in the power-generating oscillating circuit, two or more basic supply voltages, electrically isolated, can be generated. Since the oscillation voltage amplitude cannot exceed the voltage range of a cascade stage, all insulation requirements remain within the scope of this partial voltage, i.e. 1.25 kV in the example given here.

7th shows a simulated curve of voltages and powers in the first section of the DC / DC converter 200 according to 3 and 4th . The input voltage is 7.5 kV. The voltage curves 71 ... 76 are the phase voltages of the voltage divider modules 1061 ... 1065 and the end module 208 , i.e. the voltages at the connection of the drain connection of the lower power semiconductor and the source connection of the upper power semiconductor.
Voltage 77 is the output voltage of the first section 102 , shown exaggerated by a factor of 10. The output voltage is 101 V up to about 0.7 ms and then 131 V due to a simulated load change from 100 ohms to 600 ohms 79 is the voltage at the capacitive voltage divider of the end module 208 . Performance history 78 is the output power.

8th shows a simulation of the start-up of the high voltage 81 at 0.3 ms and the subsequent surge of the voltage 80 of the self-starting harmonic oscillator 60 from about 1.5 ms with SiC-FET high-voltage switching transistor. The oscillation amplitude fills the space of the operating voltage from 0 V to 1250 V, the average DC voltage regulates itself to 625 V. The supplying HV direct current is 3.74mA, the output direct power (galvanically isolated) 1.7W. The oscillator has two separate outputs for a half bridge, the first for the high potential, the second for the normal potential. The oscillation of voltage 80 is in 8th for better visibility shown with a much lower frequency (~ 5 kHz) than the oscillator 60 would really produce (550 kHz).

List of reference symbols

100, 200, 300

DC-DC converter

102

first section

104

second part

1061 ... 1067

Voltage divider modules

108, 208, 308

End module

110

Transformer circuit

112

Buck converter

60

oscillator

10631 ... 10671

Power semiconductors

10632 ... 10672

Power semiconductors

10633 ... 10673

Schottky diode

10634 ... 10674

Schottky diode

10635 ... 10675

resistance

10636 ... 10676

Voltage divider capacitor

10637 ... 10677

resistance

210

Bridge rectifier

1081, 1082

Power semiconductors

1083, 1084

Schottky diodes

1085

resistance

1086

Voltage divider capacitor

2083

transformer

2081, 2082

Voltage divider capacitor

2101 ... 2103

Diodes

62

resistance

61

High-voltage switching transistor

63 ... 65

Diodes

66 ... 69

Windings

70

Ferrite core

30611

Half bridge

30612

Series of diodes

30613

Series of resistances

30614

Series of capacitors

3061A ... C, 308C

Windings

3061 ... 3065

Voltage divider modules

71 ... 77, 79

Voltage curves

78

Performance history

Claims (14)

DC voltage converter (100, 200, 300) for converting a DC voltage in the medium voltage range into a DC voltage in the low voltage range, comprising - a series circuit comprising a plurality of first voltage divider modules (1061 ... 1067, 3061, 3065), - an end module (108, 208, 308) which is connected in series to the voltage divider modules (1061 ... 1067, 3061, 3065), the series of voltage divider modules (1061 ... 1067, 3061, 3065) and end module ( 108, 208, 308) is connected between the poles of the DC voltage in the medium voltage range, - a transformer (2083), - A rectifier (210) following the transformer, - A buck converter (112) which is connected on the input side to the output contacts of the rectifier (210), wherein the voltage divider modules (1061 ... 1067, 3061, 3065) and the end module (108, 208, 308) are designed such that a the reduced DC voltage applied to the end module (108, 208, 308) is at most half as great as the DC voltage in the medium-voltage range. DC voltage converters (100, 200, 300) according to Claim 1 , in which the voltage divider modules (1061 ... 1067, 3061, 3065) are constructed in the same way. DC voltage converters (100, 200, 300) according to Claim 1 or 2 where the Voltage divider modules (1061 ... 1067, 3061, 3065) and the end module (108, 208, 308) each include: - a half bridge (30611) with two controllable power semiconductors (10631 ... 10671, 10632 ... 10672), where the external connections of the half bridge (30611) form a first and second pole of the voltage divider module (1061 ... 1067, 3061, 3065), - a series circuit (30612) of two diodes (10633 ... 10673, 10634 ... 10674), the is connected between the first and second pole, - a resistor circuit connected between the first and second pole with a resistor (10635 ... 10675) or two series resistors, - a capacitor circuit connected between the first and second pole with a capacitor (10636 .. .10676) or two serial capacitors. DC voltage converter (100, 200, 300) according to one of the preceding claims, in which the rectifier (210) is a diode bridge rectifier (210) or a synchronous rectifier. DC voltage converter (100, 200, 300) according to one of the preceding claims, in which the reduced DC voltage is smaller than the DC voltage in the medium voltage range divided by the number of voltage divider modules (1061 ... 1067, 3061, 3065). DC voltage converter (100, 200, 300) according to one of the preceding claims, in which the reduced DC voltage is at most 3 kV, in particular at most 1.5 kV. DC voltage converter (100, 200, 300) according to one of the preceding claims, in which in each of the voltage divider modules (1061 ... 1067, 3061, 3065) the potential point between the power semiconductors (10611 ... 10671, 10612 ... 10672) of the Half bridge (30611) is connected to the potential point between the diodes and forms a third pole of the respective voltage divider module (1061 ... 1067, 3061, 3065). DC voltage converters (100, 200, 300) according to Claim 7 , in which the third pole of each of the voltage divider modules (1061 ... 1067, 3061, 3065) is connected to the first connection of a further capacitor and the second connection of which is connected to a fourth pole of the respective voltage divider module (1061 ... 1067, 3061, 3065 ) forms. DC / DC converter (100, 200, 300) according to one of the preceding claims, in which the first and second pole form the output connections of the end module (108, 208, 308). DC voltage converter (100, 200, 300) according to one of the Claims 1 to 6th , in which each of the voltage divider modules (1061 ... 1067, 3061, 3065) comprises a first, second and third winding, wherein - the connections of the first winding have a third and fourth pole of the respective voltage divider module (1061 ... 1067, 3061, 3065), - the connections of the third winding form a fifth and sixth pole of the respective voltage divider module (1061 ... 1067, 3061, 3065), - the capacitor circuit comprises two series capacitors, - a first connection of the second winding with the potential point between the power semiconductors of the half bridge (30611) is connected and the second connection of the second winding is connected to the potential point between the series capacitors. DC voltage converter (100, 200, 300) according to one of the preceding claims, in which the end module (108, 208, 308) comprises a capacitor circuit with two series capacitors (2081, 2082), the potential point between the capacitors (2081, 2082) of the Capacitor circuit forms a first output connection of the end module (108, 208, 308) and the potential point between the power semiconductors forms a second output connection of the end module (108, 208, 308). DC / DC converter (100, 200, 300) according to one of the preceding claims, in which the voltage divider modules (1061 ... 1067, 3061, 3065) and the end module (108, 208, 308) each comprise a control circuit for the power semiconductors which are used for electrical Supply is connected to the first and second pole of the voltage divider module (1061 ... 1067, 3061, 3065). DC voltage converters (100, 200, 300) according to Claim 12 , in which the control circuit comprises a self-starting oscillator (60), designed to provide a control voltage for the control terminals of the power semiconductors via a transformer and a downstream rectifier. DC voltage converters (100, 200, 300) according to Claim 11 , in which the oscillator (60) is constructed as a gate circuit.

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