DE102022115765A1 - Technology for stable DC voltage supply - Google Patents

Abstract

According to a first aspect, a device (200-1) for stable DC voltage supply (220) is provided. The device (200-1) comprises a matching converter (206), which is or can be connected in an electrically conductive manner to a DC voltage source (202, 204) or an AC voltage source (202) on an input side of the matching converter (206), and an LLC converter ( 100), which is electrically conductively connected or connectable on an input side to an output side of the matching converter (206). The LLC converter (100) is designed to provide a stable DC voltage supply (220) on an output side, wherein a DC voltage of the output-side stable DC voltage supply (220) is a function of a switching frequency of the LLC converter (100). The matching converter (206) comprises a control unit (208) which is designed to superimpose an alternating voltage (218) on an output DC voltage of the matching converter (206). An amplitude of the superimposed alternating voltage (218) is smaller than the output direct voltage. A frequency of the superimposed alternating voltage (218) is lower than the switching frequency of the LLC converter (100).

Description

The invention relates to a technology for stable DC voltage supply using an LLC converter (in English and technical terms also: “LLC converter”). The invention particularly includes a device and a method in which a temporal clock jitter (in technical terms: jitter) of an LLC converter is generated in order to avoid narrow-band peaks in the spectrum of the LLC converter.

LLC converters are being used more and more frequently in modern energy supply devices (also known as “power supplies”) because they enable very high efficiency and a small size. In the converter type of LLC converter, the change in the output voltage occurs by changing the switching frequency of the LLC converter. If the LLC converter is fed with a stable, fixed input voltage (especially with low voltage ripple), this results in a defined switching frequency of the LLC converter.

For LLC converters that are powered by a direct voltage (technically also: “direct current” voltage; short: DC voltage) or a three-phase (also: 3-phase) alternating voltage (technically also: “alternating current” voltage, short: AC voltage) are fed (possibly with an additional step-up or step-down matching converter between the DC or 3-phase input voltage and the LLC converter), the voltage at the LLC converter is conventionally so stable that the switching frequency of the LLC converter fluctuates only a little. There is practically a fixed frequency.

With regard to the conducted interference emissions at the input and output of such an LLC converter, this leads to the switching frequency of the LLC converter and its harmonics appearing as narrow-band peaks in the spectrum. Since the frequency varies so little, the average value (technically also: average value) of these peaks is almost as high as their quasi-peak value (technically also: quasi-peak value). Although there is a significantly higher limit value for the quasi-peak value than for the average value, e.g. a limit value that is approximately 10 decibels (10 dB) higher or even higher, strict measures for electromagnetic compatibility (EMC) must be taken as a result of this even the quasi-peak value is reduced below the limit for the average value. The effort required for this is high and is reflected in the device costs and device size.

The conventional behavior described above can be found particularly with DC or 3-phase device input voltage. With a single-phase (1-phase) input voltage, the input voltage at the LLC converter is typically less stable, for example with a large voltage ripple, and therefore the switching frequency of the LLC converter is also more variable, which is why the problem does not occur here or occurs to a lesser extent.

If the frequency of the LLC converter varied more, a lower quasi-peak and average value would result because the energy would be distributed over a larger frequency range. Furthermore, the average value would then be significantly below the quasi-peak value, and as a result less effort would be required for the EMC measures. With other conventional converter types (e.g. flyback converters), this is achieved through a targeted temporal jitter of the switching frequency in order to generate a broader spectrum. Since the switching frequency is the manipulated variable for the output voltage in an LLC converter, this cannot be implemented analogously in a stable DC voltage supply. Changing the switching frequency of the LLC converter would disturb the output voltage.

The invention is therefore based on the object of specifying a technology for stable DC voltage supply by means of an LLC converter, which is fed by a low-ripple input voltage, in particular a DC voltage or three-phase AC voltage with subsequent rectification. Alternatively or additionally, the task is to avoid narrow-band peaks in the spectrum of an LLC converter with a low-ripple input voltage. Furthermore, alternatively or additionally, there is the task of generating a temporal clock jitter (in technical terms: jitter) of the switching frequency of an LLC converter without disturbing an output voltage of the LLC converter.

The task or tasks are solved with the features of the independent claims. Appropriate refinements and advantageous developments of the invention are specified in the dependent claims.

Embodiments of the invention are described below with partial reference to the figures.

According to a first aspect, a device for stable DC voltage supply is provided. The device comprises a matching converter, which is electrically conductively connected or connectable to a DC voltage source or to an AC voltage source on an input side of the matching converter. The device further comprises an LLC converter which is based on an input side is electrically conductively connected or connectable to an output side of the matching converter. The LLC converter is designed to provide a stable DC voltage supply on an output side. A DC voltage of the output-side stable DC voltage supply is a function of a switching frequency of the LLC converter. The matching converter comprises a control unit (in English and technical terms: controller), which is designed to superimpose an alternating voltage on a (for example low-voltage ripple) DC output voltage of the matching converter. An amplitude of the superimposed alternating voltage is smaller than the output direct voltage of the matching converter. A frequency of the superimposed alternating voltage is lower than the switching frequency of the LLC converter.

The LLC converter can be a resonant converter. Alternatively or additionally, the LLC converter can include a transformer on the output side. A primary side of the transformer may be a primary inductance ( _LP , i.e. the larger output inductance) of the LLC converter. A leakage inductance (L _S ) of the transformer may be the coupling inductance of the LLC converter.

Alternatively or additionally, the LLC converter can include a rectifier on the output side. The DC voltage of the output-side stable DC voltage supply (which is a function of a switching frequency of the LLC converter) can be this rectified (and optionally capacitively smoothed) DC voltage.

The LLC converter can include a circuit unit (also: regulator). The circuit unit of the LLC converter can generate the switching frequency of the LLC converter.

The stable DC voltage supply at the output side of the LLC converter can depend on the switching frequency of the circuit unit of the LLC converter.

The matching converter can have a boost converter (also: boost converter; English: boost converter; also: step-up converter), a buck converter (also: buck converter; English: buck converter; also: step-down converter) and/or a boost/low converter ( also: up/down converter; English: Buck Boost Converter).

Alternatively or additionally, the matching converter can include a flyback converter, a SEPIC converter (SEPIC short for: Single Ended Primary Inductance Converter), a flux converter and/or a bridge converter. Furthermore, alternatively or additionally, the flyback converter and/or the SEPIC converter can be classified as a boost/boost converter. Furthermore, alternatively or additionally, the flux converter and/or the bridge converter can be designed and/or classified as a step-down converter or step-up converter. For example, an output voltage can be higher than an input voltage due to a transformer in a circuit of the forward converter and/or the bridge converter.

Furthermore, alternatively or additionally, the matching converter can comprise a, in particular bridgeless, rectifier (English: Bridgeless Recitifier), for example a Vienna rectifier (English: Vienna Rectifier). For example, the, in particular bridgeless, rectifier can be connected or connectable on the input side to the AC voltage source. The matching converter comprising a, in particular bridgeless, rectifier can provide a, for example, controllable, DC output voltage.

For example, a matching converter can include a, in particular bridgeless, rectifier for AC voltage sources and/or output voltages of the matching converter and/or the device comprising the LLC converter in the high power range, in particular greater than or equal to one kilowatt (1 kW). Alternatively or additionally, a power factor correction (PFC for short) can be important and/or applied at high power levels. For example, conventional rectifiers that can be switched or switched in series between the AC voltage source and the input side of the matching converter are unsuitable for PFC at high powers.

The DC voltage source on the input side of the matching converter may include rectification of a three-phase AC voltage.

The frequency of the superimposed alternating voltage can be a low-frequency alternating voltage. Alternatively or additionally, the frequency of the superimposed alternating voltage (in particular much or many times, for example by at least an integer multiple) can be lower than the switching frequency of the LLC converter and / or (in particular much, for example by an integer multiple) lower than a bandwidth of the circuit unit ( also: the regulator) of the LLC converter. If the frequency of the superimposed alternating voltage (in particular much or many times, for example by at least an integer multiple) is lower than the switching frequency of the LLC converter and (in particular much or many times, for example by at least an integer multiple). ges multiples) lower than the bandwidth of the circuit unit of the LLC converter, in particular the output voltage can be kept stable.

The amplitude of the (for example superimposed) alternating voltage can be a maximum absolute value of the (for example superimposed) alternating voltage.

Using the superimposed alternating voltage, a temporal clock jitter (also: frequency jitter) can be generated in the LLC converter.

The input voltage of the LLC converter can be changed (also: manipulated) using the (particularly small) superimposed alternating voltage. Alternatively or additionally, the frequency of the LLC converter and its jitter must not only be visible on the input voltage. The clock frequency of the LLC converter can be observed and/or found in the input current and/or output current (and for example in the voltage ripple generated thereby on the input side and output side of the LLC converter), and/or in a transformer voltage of the LLC converter.

Due to the changing input voltage, the LLC converter can, or must, adjust its frequency (for example by means of the circuit unit; also: regulator). The jitter can therefore be generated and/or arise directly in the LLC converter.

For example, an LLC converter may have an input DC voltage of 800 V (also: Vdc for DC voltage), an output DC voltage of 24 V (also: Vdc), and a switching frequency of 95 kHz. The input voltage can be increased to, for example, 815 V (also: Vdc) using the superimposed alternating voltage (for example in a positive phase of the alternating voltage). In order to maintain the output voltage at 24 V (also: Vdc), the circuit unit (also: regulator) of the LLC converter in this exemplary embodiment increases the switching frequency to, for example, 100 kHz. The input voltage can then be reduced to 785 V (also: Vdc) (for example in a negative phase of the alternating voltage). In order to maintain the output voltage at 24 V (also: Vdc), the circuit unit (also: regulator) in this exemplary embodiment of the LLC converter reduces the switching frequency to, for example, 90 kHz.

The switching frequency of the LLC converter may be visible in the input current and/or output current of the LLC converter. Alternatively or additionally, the switching frequency of the LLC converter may be visible in the voltage at the LLC converter's transformer.

With regard to electromagnetic compatibility (EMC), the switching frequency of the LLC converter can be observable (also: detectable or visible) in the (for example entire) device comprising the LLC converter. The switching frequency of the LLC converter can, for example, be transmitted to (e.g. all possible) locations by parasitic couplings, so that the switching frequency of the LLC converter can be detected both on the input side and on the output side of the device.

The circuit unit of the LLC converter can be designed to change the switching frequency in response to the alternating voltage superimposed on the input direct voltage.

The DC output voltage of the matching converter can correspond to the DC input voltage of the LLC converter.

Due to the temporal clock jitter of the LLC converter, high peak values can be avoided, suppressed and/or broadened in the frequency range of the LLC converter. Alternatively or additionally, high peak values in the frequency range of the LLC converter can be distributed and/or blurred over a frequency range broadened by the frequency of the superimposed alternating voltage instead of in a narrow frequency range of the switching frequency.

Due to the superimposed alternating voltage, a change in the level of the input-side DC voltage at the LLC converter and the change in the switching frequency can be compensated for in the circuit unit of the LLC converter in such a way that the output-side DC voltage supply of the LLC converter is stable.

Using the device, an improved EMC of the LLC converter can be achieved with simple components and/or a small size.

The DC voltage source may comprise a (e.g. three-phase) AC voltage source and a rectifier arranged between the (e.g. three-phase) AC voltage source and the input side of the matching converter.

• - Die überlagernde Wechselspannung, beispielsweise die Dreiecksspannung und/oder die Sinusspannung, kann einen stetigen Verlauf umfassen. Der stetige Verlauf der überlagernden Wechselspannung kann eine zeitnahe Reaktion der Schaltungseinheit des LLC-Wandlers ermöglichen und/oder verbessern.

The superimposed alternating voltage can include, for example, a triangular voltage (also: triangular voltage), a sinusoidal voltage (also: sinusoidal voltage), a sawtooth voltage (also: sawtooth-shaped voltage) and/or a square-wave voltage (also: rectangular voltage). Alternatively or additionally, the superimposed alternating voltage can comprise a trapezoidal voltage (also: trapezoidal voltage).

• - The superimposed alternating voltage, for example the triangular voltage and/or the sine voltage, can have a continuous course. The steady course of the superimposed alternating voltage can enable and/or improve a timely response of the circuit unit of the LLC converter.

The device can further comprise two resistors which, connected in series, form a voltage divider. The voltage divider can be connected between both poles of the output side of the matching converter and/or between both poles of the input side of the LLC converter. The control unit can be designed to regulate the DC output voltage of the matching converter depending on a voltage tapped at a node between the first resistor and the second resistor of the voltage divider.

The voltage tapped between the first resistor and the second resistor of the voltage divider can include an actual voltage (also: an actual value of the voltage).

The device can further comprise a signal generator which couples a control signal of the superimposed alternating voltage into the tapped voltage. The coupling optionally takes place via a third resistor, which is connected in an electrically conductive manner with a first connection to the node between the first resistor and the second resistor of the voltage divider. The third resistor can be electrically connected to the signal generator at a second connection.

The superimposed alternating voltage can be coupled to the control unit of the matching converter via the voltage divider for an actual value detection of the voltage on the input side of the LLC converter.

Alternatively or additionally, an analog coupling of the control signal (signal coupling) of the superimposed alternating voltage can be made possible by means of the third resistor.

The signal generator can also be electrically conductively connected to one of the two poles of the output side of the matching converter and/or one of the two poles of the input side of the LLC converter. Alternatively or additionally, the signal generator can be arranged outside the matching converter.

Alternatively or additionally, the control signal of the superimposed alternating voltage can be added to the voltage tapped via the voltage divider.

Adding up the voltages on the input side of the control unit can include analog and/or digital coupling of the control signal (in short: signal coupling).

The control unit can be designed to regulate the output DC voltage of the matching converter depending on an actual voltage. The signal generator can couple a control signal from the superimposed alternating voltage into the actual voltage. Optionally, the control signal can be added to an actual value in the control unit.

Alternatively or additionally, the control unit can be designed to regulate the output DC voltage of the matching converter depending on a target voltage. The signal generator can couple a control signal from the superimposed alternating voltage into the target voltage. Optionally, the control signal can be added to a constant setpoint in the control unit.

The device can comprise the signal generator coupling in at the target voltage and/or the signal generator coupling in at the actual voltage.

Adding the superimposed alternating voltage to the constant setpoint in the control unit can include analog and/or digital coupling of the control signal (short: signal coupling).

The superposition of the output voltage of the matching converter with the alternating voltage can include analog signal coupling and/or digital signal coupling in the control unit.

A frequency of the voltage at the input side of the matching converter may include zero Hertz (Hz) for a DC voltage source. Alternatively or additionally, a frequency of the voltage on the input side of the matching converter (before its rectification) can be between 50 Hz and 60 Hz for an input-side (e.g. three-phase) AC voltage source with a subsequent rectifier. Furthermore, alternatively or additionally, a frequency of the voltage on the input side of the matching converter (before its rectification) can be between 100 Hz and 1000 Hz, in particular 400 Hz, for an (e.g. aircraft) on-board electrical system.

The frequency of the superimposed alternating voltage can be between 0.5 Hz and 2 Hz, For example, in the case of an AC voltage source with a subsequent rectifier on the input side of and/or in the matching converter. In particular, the frequency of the superimposed alternating voltage can be 1 Hz.

Alternatively or additionally, the frequency of the superimposed alternating voltage can be (e.g. slightly or slightly) greater than 2 Hz, for example in the case of a direct voltage source on the input side of the matching converter.

An input-side (e.g. three-phase) AC voltage source can, for example, have an amplitude of the AC voltage of 400 volts (V) to 500 V. Alternatively or additionally, an input-side DC voltage of the matching converter can comprise, for example, between 12 V and 800 V. For example, the alternating voltage of an input-side (e.g. three-phase) alternating voltage source can be rectified before entering the matching converter.

The DC output voltage of the matching converter can be at least an integer multiple of the amplitude of the superimposed AC voltage, for example at least three times to at least 40 times.

Alternatively or additionally, the DC output voltage of the matching converter can be 800 V. Alternatively or additionally, the amplitude of the superimposed alternating voltage can be between 10 V and 20 V.

According to a second aspect, a method for providing a stable DC voltage supply is provided. The method includes a step of adjusting a DC voltage from a DC voltage source or adjusting an AC voltage from an AC voltage source using a matching converter. The method further comprises a step of superimposing an output DC voltage of the matching converter with an alternating voltage, wherein an amplitude of the superimposed AC voltage is smaller than a DC output voltage of the matching converter. The method further includes a step of converting (also: converting) the DC output voltage of the matching converter superimposed on the AC voltage by means of an LLC converter. The LLC converter is designed to provide a stable DC voltage supply on an output side, wherein a DC voltage of the output-side stable DC voltage supply is a function of a switching frequency of the LLC converter. According to the method, a frequency of the superimposed alternating voltage is lower than the switching frequency of the LLC converter. The method further includes the step of providing a stable DC voltage at the output side of the LLC converter.

The method may include a step of rectifying an (e.g. three-phase) alternating voltage of an alternating voltage source using a rectifier. Furthermore, the method may include a step of providing the rectified voltage as the DC voltage of the DC voltage source at an input side of the matching converter.

The method of the second aspect can also be referred to as a method for frequency jitter in an LLC converter, or for short as a method for LLC jitter, at a low ripple input voltage.

The method of the second aspect can be carried out using the device of the first aspect.

The invention is explained in more detail below with reference to the drawings using preferred exemplary embodiments.

• 1 ein schematisches Ausführungsbeispiel eines LLC-Wandlers;
• 2A und 2B ein schematisches erstes Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung zur stabilen Gleichspannungsversorgung umfassend einen LLC-Wandler, beispielsweise den LLC-Wandler der 1, mit einer Gleichspannungsquelle in 2A und einer Wechselspannungsquelle in 2B;
• 3 ein schematisches zweites Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung zur stabilen Gleichspannungsversorgung umfassend einen LLC-Wandler, beispielsweise den LLC-Wandler der 1;
• 4 ein schematisches drittes Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung zur stabilen Gleichspannungsversorgung umfassend einen LLC-Wandler, beispielsweise den LLC-Wandler der 1;
• 5 einen schematischen Spektrumsverlauf der Ausgangsspannung in Abhängigkeit der Schaltfrequenz eines herkömmlichen LLC-Wandlers; und
• 6 einen schematischen Spektrumsverlauf der Ausgangsspannung einer erfindungsgemäßen Vorrichtung zur stabilen Gleichspannungsversorgung, beispielsweise einer Vorrichtung gemäß 2A, 2B, 3 oder 4, in Abhängigkeit der Schaltfrequenz eines LLC-Wandlers, beispielsweise des LLC-Wandlers der 1.

Show it:

• 1 a schematic embodiment of an LLC converter;
• 2A and 2 B a schematic first exemplary embodiment of a device according to the invention for stable DC voltage supply comprising an LLC converter, for example the LLC converter of 1 , with a DC voltage source in 2A and an alternating voltage source in 2 B ;
• 3 a schematic second embodiment of a device according to the invention for stable DC voltage supply comprising an LLC converter, for example the LLC converter of 1 ;
• 4 a schematic third embodiment of a device according to the invention for stable DC voltage supply comprising an LLC converter, for example the LLC converter of 1 ;
• 5 a schematic spectrum profile of the output voltage depending on the switching frequency of a conventional LLC converter; and
• 6 a schematic spectrum profile of the output voltage of a device according to the invention for stable DC voltage supply, for example a device according to 2A , 2 B , 3 or 4 , depending on the switching frequency of an LLC Converter, for example the LLC converter 1 .

1 shows a schematic exemplary embodiment of an LLC converter 100. The LLC converter 100 includes a first inductor (“L” or Ls in) connected in series 1 ) 104-1, a second inductance (“L”) 104-2 and a capacitance (“C” or Cr in 1 ) 106-1.

The exemplary LLC converter 100 the 1 further includes a third inductor 104-3 inductively coupled to the second inductor 104-2. The second inductor 104-2 and third inductor 104-3 preferably form a transformer (T1) 102.

On the input side of the exemplary LLC converter 100 there is a smoothing capacitor (C1) 106-2 and two semiconductor switches (S1, S2) 108. The semiconductor switches (S1, S2) 108 can be switched using the schematically illustrated circuit unit 112 according to a switching frequency of the LLC Converter 100 can be switched. For example, the first semiconductor switch (S1) 108 can be switched on while the second semiconductor switch (S2) 108 is switched on and vice versa.

On the output side, the LLC converter 100 includes a rectifier, for example a plurality of diodes 110 (D1, D2, D3, D4), for rectifying the output voltage of the LLC converter 100. Furthermore, the output side of the exemplary LLC converter 100 includes a smoothing capacitor 106-3 ( C2).

The 2A and 2 B , 3 and 4 each show an exemplary embodiment of the device according to the invention for stable DC voltage supply. The device of the first embodiment is generally designated by reference numeral 200-1. The device of the second embodiment is generally designated by reference numeral 200-2. The device of the third embodiment is generally designated by reference numeral 200-3.

Same or equivalent components in the exemplary embodiments 2A , 2 B , 3 and 4 are each designated with the same reference numerals.

Examples of a DC voltage source are in the 2A , 3 and 4 each a three-phase AC voltage source 202 and a downstream rectifier 204 are shown, from which a DC voltage is fed to a matching converter 206.

The exemplary embodiment of the 2 B shows a three-phase AC voltage source 202 that is connected directly to an input side of a matching converter 206.

The device 200-1; 200-2; 200-3 each includes an LLC converter, which is in 2A , 2 B , 3 and 4 shown schematically and designated by reference number 100. The LLC converter 100 the 2A , 2 B , 3 and 4 can each be assigned to the LLC converter 100 1 accordingly. Alternatively or additionally, the LLC converter 100 can be in the 2A , 2 B , 3 and 4 also include other embodiments (not shown) of an LLC converter.

The device 200-1; 200-2; 200-3 further includes a matching converter 206 with a control unit 208. The control unit 208 is designed to receive both a setpoint 210 of the DC output voltage and an actual value 212 of the DC output voltage of the matching converter 206. The actual value 212 of the output DC voltage is in the exemplary embodiments 200-1; 200-2; 200-3 the 2A , 2 B 3 and 4 are each determined between a first resistor (R1) 214 and a second resistor (R2) 216 of a voltage bridge.

The device 200-1; 200-2; In each exemplary embodiment, 200-3 includes a signal generator 219 for a superimposed alternating voltage 218. The superimposed alternating voltage 218 is low frequency. Low frequency herein refers to a frequency that is so low that a circuit unit of the LLC converter 100, for example the circuit unit 112 in 1 , can react to the voltage change.

Furthermore, an amplitude of the superimposed alternating voltage 218 is, for example, many times smaller than an amplitude of the output direct voltage of the matching converter 206. For example, an amplitude of the superimposed alternating voltage can be at most 20 V, in particular between 10 V and 20 V.

The LLC converter 100 can have a response time of, for example, 0.5 ms to 1 ms, in which it can correct a disturbance in the output voltage (for example by means of the circuit unit 112). However, higher values of the response time of the LLC converter, 100 to approximately 5 ms, are also possible for large devices (for example the devices 200-1; 200-2; 200-3).
Another characteristic value that can in principle describe the same as the response time of the LLC converter is the bandwidth of the circuit unit (also: regulator) 112 in the LLC converter 100. One can also say that the circuit unit (also: Controller) 112 of the LLC converter 100 has a bandwidth of approximately 5 kHz to 8 kHz. However, values of only 1 kHz are also conceivable for larger devices (for example the devices 200-1; 200-2; 200-3).

Example switching frequencies of the LLC converter 100 may be between 80 kHz and 120 kHz. Alternatively or additionally, in (particularly larger) devices (for example the devices 200-1; 200-2; 200-3) the switching frequencies can tend to decrease (for example to only 30 kHz to 40 kHz). Furthermore, alternatively or additionally, in (particularly smaller) devices (for example the devices 200-1; 200-2; 200-3) the switching frequencies can also be higher (for example in the range of 150 kHz).

The switching frequency of the LLC converter 100 and the response time of the LLC converter 100 do not have to be directly and/or functionally dependent on one another. Alternatively or additionally, the switching frequency of the LLC converter 100 in exemplary embodiments is significantly higher than the bandwidth of the circuit unit (also: controller) 112 in order to prevent the switching frequency from interfering with the circuit (also: control).

Alternatively or additionally, the sizes of components used in the device (for example the device 200-1; 200-2; 200-3), for example of (in particular transformer) inductors, can be limiting for the bandwidth of the circuit unit (also: controller) 112 and/or output capacities. Furthermore, alternatively or additionally (for example in the vast majority of cases) the switching frequency of the LLC converter 100 is not the limiting factor for the response time of the circuit unit (also: controller) 112.

According to the invention, the superimposed (also: modulated) alternating voltage 218 changes to the input voltage of the LLC converter 100 (in particular much or many times, for example by at least an integer multiple) slower than the response time of the circuit unit (also: regulator) 112. Alternatively or additionally According to the invention, the frequency of the superimposed alternating voltage 218 (in particular significantly, for example by at least an integer multiple) must be smaller than the bandwidth of the circuit unit (also: regulator) 112 in order to prevent the superimposed alternating voltage 218 from also being on the output voltage of the LLC converter 100 is observable (also: visible).

1. 1) Die Wechselspannung 218 kann auch für eine Modulation des Eingangsstromes des Anpasswandlers 206 sorgen. Wenn der Eingangsstrom des Anpasswandlers 206 mit einer 3-phasigen Wechselspannung (auch: Netzspannung) versorgt wird, hat die Wechselspannung (auch: Netzspannung) herkömmlicherweise eine Frequenz von 50 Hz. Die Steuereinheit (auch: Regler) 208 des Anpasswandlers 206 kann in einem Ausführungsbeispiel sehr langsam ausgelegt sein (z.B. entsprechend einer Bandbreite von ca. 10 Hz), um zu verhindern, dass die Steuereinheit (auch: Regler) 208 zu Asymmetrien im Netzstrom (beispielsweise an der Ausgangsseite des Anpasswandlers 206) führt (z.B. positive Halbwelle der Netzspannung größer als negative Halbwelle der Netzspannung). Die Frequenz der die Ausgangsspannung des Anpasswandlers 206 überlagernden (auch: aufmodulierten) Wechselspannung 218 ist gemäß diesem Ausführungsbeispiel (insbesondere) deutlich geringer als die Bandbreite der Steuereinheit 208 des Anpasswandlers 206 (und/oder der Schaltungseinheit 112 des LLC-Wandlers 100), um die Steuereinheit (auch: Regler) 208 (und/oder die Schaltungseinheit 112) nicht zu stören und/oder zu überfordern.
2. 2) Experimentell hat sich gezeigt, dass Modulationsfrequenzen (und/oder Frequenzen der überlagernden Wechselspannung 218) zwischen 1 Hz und 2 Hz zu einer guten Form abgeflachter Spitzen im Spektrum führen können. Je nach Modulationsfrequenz (und/oder Frequenz der überlagernden Wechselspannung 218) kann die Form auch anders aussehen, insbesondere von abgeflachten Spitzen abweichen (z.B. zwei große „Hörner-Spitzen“ rechts und links eines Plateaus umfassen). Die Modulationsfrequenz (und/oder Frequenz der überlagernden Wechselspannung 218) hat also gemäß einigen (oder allen) Ausführungsbeispielen eher einen Einfluss auf die Form der Spitzen als auf deren Breite.

The frequency of the alternating voltage 218 superimposed on the input voltage of the LLC converter 100 can be chosen to be low, for example in the range of 1 Hz, for the following reasons:

1. 1) The AC voltage 218 can also provide modulation of the input current of the matching converter 206. If the input current of the matching converter 206 is supplied with a 3-phase alternating voltage (also: mains voltage), the alternating voltage (also: mains voltage) conventionally has a frequency of 50 Hz. The control unit (also: regulator) 208 of the matching converter 206 can in one embodiment be designed to be very slow (e.g. corresponding to a bandwidth of approximately 10 Hz) in order to prevent the control unit (also: regulator) 208 from causing asymmetries in the mains current (e.g. on the output side of the matching converter 206) (e.g. positive half-wave of the mains voltage is larger as a negative half wave of the mains voltage). According to this exemplary embodiment, the frequency of the alternating voltage 218 superimposed (also: modulated) on the output voltage of the matching converter 206 is (in particular) significantly lower than the bandwidth of the control unit 208 of the matching converter 206 (and/or the circuit unit 112 of the LLC converter 100). Not to disturb and/or overtax the control unit (also: regulator) 208 (and/or the circuit unit 112).
2. 2) Experimentally it has been shown that modulation frequencies (and/or frequencies of the superimposed alternating voltage 218) between 1 Hz and 2 Hz can lead to a good form of flattened peaks in the spectrum. Depending on the modulation frequency (and/or frequency of the superimposed alternating voltage 218), the shape can also look different, in particular it can deviate from flattened peaks (e.g. include two large “horn peaks” on the right and left of a plateau). According to some (or all) embodiments, the modulation frequency (and/or frequency of the superimposed alternating voltage 218) has more of an influence on the shape of the peaks than on their width.

The width of the peaks in the spectrum of the LLC converter 100 can depend on the amplitude of the superimposed (also: modulated) alternating voltage 218. The higher the amplitude, the more the LLC converter 100 must adjust its frequency according to exemplary embodiments of the invention in order to keep the output voltage stable. The maximum and minimum switching frequencies of the LLC converter 100 can determine the width of the peaks.

In each embodiment of the device 200-1; 200-2; 200-3 in 2A and 2 B , 3 or. 4 Connections 220 for a stable DC voltage supply are also shown on the output side of the LLC converter 100, which can be connected in an electrically conductive manner, for example, to a load (not shown).

In the exemplary embodiments of the device 200-1 in 2A and 2 B is the AC voltage 218 via a third resistor (Rk) 222 into the voltage divider (R1; R2) 214; 216 coupled. The coupling takes place in the exemplary embodiments 2A and 2 B via the actual value detection 212 of the DC output voltage of the matching converter 206 and/or the DC input voltage (Vzk) of the LLC converter 100.

The DC input voltage (Vzk) of the LLC converter 100 may correspond to the DC output voltage of the matching converter 206.

In the exemplary embodiments of 2A and 2 B The signal coupling of the alternating voltage 218 takes place analogously (in short: analog signal coupling).

In the exemplary embodiment 2A the matching converter 206 is fed by a three-phase alternating voltage 202, which is converted into a direct voltage by means of a rectifier 204 before entering the matching converter 206.

In the exemplary embodiment 2 B the matching converter 206 is fed (in particular directly) by a three-phase alternating voltage 202.

The matching converter 206 in the exemplary embodiment 2 B can, for example, include a bridgeless rectifier (English: Bridgeless Rectifier), in particular a Vienna rectifier (English: Vienna Rectifier) and be connected (for example directly) to an alternating voltage 202 and deliver an, in particular controllable, direct output voltage.

In the following exemplary embodiments 3 and 4 A circuit with a rectifier 204 is shown between an AC voltage source 202 and the matching converter 206. Analogous to the exemplary embodiment of 2 B Further exemplary embodiments (not shown) may include integrating the rectifier 204 into the matching converter 206.

In the exemplary embodiment of the device 200-2 in 3 the superimposed alternating voltage 218 is coupled in between the voltage divider (R1; R2) 214; 216 and the control unit 208. Alternatively or additionally, the coupling of the superimposed alternating voltage 218 in the exemplary embodiment of 3 in the control unit 208. In 3 the coupling of the superimposed alternating voltage 218 is shown schematically as an addition (“+”) to the actual value 212. The signal coupling of the superimposed alternating voltage 218 into the output direct voltage of the matching converter 206 and/or into the input direct voltage (Vzk) of the LLC converter 100 in 3 can be analog and/or digital.

In the exemplary embodiment of the device 200-3 in 4 The superimposed alternating voltage 218 is coupled in via the setpoint detection 210 of the control unit 208 of the matching converter 206. As shown schematically in 4 shown, the superimposed alternating voltage 218 can be added (“+”) to a, in particular constant, target voltage 210. The signal coupling of the superimposed alternating voltage 218 in the exemplary embodiment of 4 can be analog and/or digital. Alternatively or additionally, the signal coupling in the exemplary embodiment 4 in the control unit 208.

In each of the embodiments of the device 200-1; 200-2; 200-3 in 2A , 2 B , 3 or. 4 A delta voltage is shown as an alternating voltage 218 as an example. However, other forms of alternating voltage 218, in particular as a sine wave voltage, sawtooth voltage and/or square wave voltage (also: rectangular voltage), are equally possible. A form of the output spectrum of the LLC converter depends on the respective form of the alternating voltage 218.

The triangular voltage shown and a sine voltage (and/or a trapezoidal voltage, for example) have the advantage of a constant voltage curve.

If there is a sudden change in the input voltage of the LLC converter 100, the LLC converter 100 would also have to change its switching frequency suddenly if the output voltage is to remain stable. However, due to the response time of the circuit unit (also: controller) 112, the LLC converter 100 cannot usually adjust its frequency as quickly as desired. Therefore, a disturbance in the output voltage can become visible, particularly at high frequencies of the superimposed alternating voltage 218 and/or at discontinuous voltage curves of the superimposed alternating voltage 218. It is therefore advantageous if the alternating voltage 218 has a constant curve on the input voltage of the LLC converter 100. Alternatively or additionally, the circuit unit (also: regulator) 112 of the LLC converter 100 regulate constant voltage changes well.

Alternatively or additionally, superimposed alternating voltages (also: modulation signals) 218 with discontinuities (e.g., square wave, sawtooth) can be advantageous. The shape of the superimposed alternating voltage (also: modulation signal), for example, influences the shape of the peaks in the spectrum.

Furthermore, alternatively or additionally, depending on the application, small disturbances on the output voltage of the LLC converter 100 can also be tolerated, which is why an overlying alternating voltage (also: modulation signal) 218 with jumps would not be too big of a problem.

In principle, any form of superimposed alternating voltage 218 can be used with a suitable (and/or specific) amplitude and frequency.
Furthermore, in each of the embodiments of the device 200-1; 200-2; 200-3 in 2A , 2 B , 3 or. 4 the matching converter 206 is designed, for example, as a step-up converter. However, other forms of design of the matching converter 206, in particular as a step-down converter and/or step-up converter, are equally possible.

5 shows an example of a conventional output spectrum of an LLC converter, for example the LLC converter 100 of the 1 . The spectrum in 5 can also be referred to as an example spectrum without LLC jitter.

On the abscissa is at reference number 502 in 5 the respective frequency is plotted in units of Hertz (Hz). A logarithmic unit of the voltage measure in decibel-micro-volt (dBµV) is plotted on the ordinate at reference number 504. A quasi-peak limit value (also: quasi-peak limit or quasi-peak characteristic value) is plotted at reference number 506, and an average limit value (also: average limit or average characteristic value) is plotted at reference number 508. The quasi-peak limit and/or the average limit can be determined by an EMC of the LLC converter, for example the LLC converter 100 in 1 , be given.

A spectrum of quasi-peak measured values (also: quasi-peak measured values) of a conventional LLC converter with input voltage with low voltage ripple is plotted at reference number 510. How out 5 For example, as can be seen in the frequency range at 300 kHz and at 500 kHz, the conventional quasi-peak spectrum includes narrow-band peaks that may exceed one of the limit values, for example the average limit at reference numeral 508.

A spectrum of average measured values (also: average measured values) of a conventional LLC converter with input voltage with low voltage ripple is plotted at reference number 512. Narrow-band peaks are also visible in this conventional spectrum.

6 shows an exemplary output spectrum of the LLC converter 100 of the device 200-1 according to the invention; 200-2; 200-3 the 2A , 2 B , 3 or. 4 . The output spectrum is provided, for example, at the connections designated by reference numeral 220. The spectrum in 6 can also be referred to as an example spectrum with LLC jitter.

The same variables (e.g. coordinate axes, characteristic values and/or limit values) are in 5 and 6 designated with the same reference numerals.

At reference number 610 in 6 is the spectrum of the quasi-peak measured values (also: quasi-peak measured values) at the output (for example at the connections 220 of the stable DC voltage supply) of the LLC converter 100 of the device 200-1 according to the invention; 200-2; 200-3 applied. The spectrum of 6 compared to the conventional spectrum 5 broadened and flattened peaks, as seen, for example, in the frequency range at approximately 300 kHz and at approximately 500 kHz.

At reference number 612 is the spectrum of the average measured values (also: average measured values) at the output (for example at the connections 220 of the stable DC voltage supply) of the LLC converter 100 of the device 200-1 according to the invention; 200-2; 200-3 applied. Also in this spectrum 6 is the broadening and flattening of the tips compared to 5 visible.

As exemplified by the comparison of 5 and 6 As can be seen, a greater than the conventional variation in the switching frequency of the LLC converter 100 results in lower quasi-peak values (also: quasi-peak values) and average values (also: average values) in the spectrum, since the energy is distributed over a larger frequency range.

Alternatively or additionally, the average values (also: average values) of the device according to the invention (for example the device 200-1; 200-2; 200-3 in 3 , 4 or. 5 ) are well below the quasi-peak values (also: quasi-peak values).

Thus, when using the device according to the invention (for example the device 200-1; 200-2; 200-3 the 2A and 2 B , 3 or. 4 ) and/or feeding a superimposed alternating voltage 281 into the input direct voltage of the LLC converter 100 requires less effort than is conventionally required for EMC measures, in particular of the LLC converter 100.

Through the DC input voltage and DC output voltage of the LLC converter, for example the LLC converter 100 1 , its switching frequency is fixed. If you now change the input DC voltage of the LLC converter 100, then according to the invention its switching frequency must also change in order to generate an equally high output DC voltage (for example at the connections 220 of the stable DC voltage supply). If the input DC voltage change according to the invention occurs only slowly, then the circuit unit 112 (also: control) of the LLC converter 100 is able to readjust the output DC voltage quickly enough so that the disturbance (particularly in the frequency and amplitude of the input DC voltage) does not affect the output DC voltage .

The technical solution according to the invention is that a matching converter 206 is present between the input DC voltage and the LLC converter 100, which supplies the LLC converter 100 with its output DC voltage.

According to the invention, the technical solution also consists in changing (also: manipulating) the DC output voltage of the matching converter 206 in such a way that an AC voltage 218 is specifically superimposed on it. Due to the change in the DC output voltage of the matching converter 206, the switching frequency of the LLC converter 100 must also change (in particular if the DC output voltage of the LLC converter 100 is constant, for example at the connections 220 of the stable DC voltage supply).

According to one exemplary embodiment, a device according to the invention for stable direct voltage supply is fed by a three-phase (also: 3-phase) alternating voltage source (also: mains voltage) 202, which is then rectified 204. This is followed by a step-up converter (also: boost converter; English: boost converter) as a matching converter 206. An alternating voltage (for example a triangle voltage or a sawtooth voltage) 218 is superimposed on the actual value for the DC output voltage of the step-up converter 206, which causes the DC output voltage of the step-up converter 206 to fluctuate accordingly (e.g. by an amplitude of ±7 V with a frequency of 1.2 Hz at an average of 805 volts). The fluctuating input DC voltage leads to a temporal clock jitter (also: frequency jitter) of the LLC converter 100.

The device of, or each, exemplary embodiment can provide an adjustable DC output voltage of 22.5 V to 29.5 V, in particular 24 V (for example at the connections 220 of the stable DC voltage supply in 2A , 2 B , 3 or 4 ). The output currents can range between 2.5 amps (A) and 40 A. In particular, the output currents can include 2.5 A, 5 A, 10 A, 20 A and/or 40 A.

According to further exemplary embodiments, values of the output DC voltage of 12 V, 48 V, 120 V or 250 V are possible. Alternatively or additionally, the output currents can be in the range of several hundred amperes, e.g. 200 A or 1000 A.

The present invention is not limited to the voltage values or current values (also referred to collectively as characteristics) of the above-mentioned exemplary embodiments, but is also applicable to other combinations of characteristics.

According to further exemplary embodiments, the matching converter 206 includes a buck converter (also: buck converter), a buck-boost converter, a flyback converter, a SEPIC converter, a flux converter and /or a bridge converter.

In each exemplary embodiment, the LLC converter 100 may include its own control loop, for example integrated in (or comprising the) circuit unit 112. Alternatively or additionally, the superimposed alternating voltage 218 can influence the control unit 208 of the matching converter 206.

Furthermore, alternatively or additionally, the control loop of the LLC converter 100 is not intervened directly, but only indirectly, for example, by changing both the amplitude and frequency of the input DC voltage (in particular by superimposing the output DC voltage of the matching converter 206 with the AC voltage 218) at the input of the LLC converter 100.

Because of the change in the input DC voltage, the LLC converter 100 must change its switching frequency according to exemplary embodiments of the invention so that the output DC voltage (for example at the connections 220 of the stable DC voltage supply in 2A , 2 B , 3 or 4 ) remains stable. This is done by a (for example already existing) circuit unit 112 (also: control circuit) of the LLC converter 100.

According to the invention, the switching frequency change of the LLC converter 100 can therefore be forced indirectly by the matching converter 206 without having to intervene directly in the circuit unit 112 (also: the control loop) of the LLC converter 100.

According to an exemplary embodiment, the device according to the invention 200-1; 200-2; 200-3 is fed by a DC voltage source, i.e. an input DC voltage with a frequency of 0 Hz.

According to a further exemplary embodiment, the device 200-1 according to the invention; 200-2; 200-3 is fed by a (for example three-phase) alternating voltage 202 with a frequency of 50 Hz to 60 Hz and subsequent rectification 204.

According to a further exemplary embodiment, the device 200-1 according to the invention; 200-2; 200-3 is fed by an alternating voltage (for example from an on-board electrical system, in particular an aircraft) 202 with a frequency of 400 Hz and subsequent rectification 204.

According to further exemplary embodiments, frequencies of over 400 Hz of an alternating voltage source 202 with subsequent rectification 204 are possible.

Alternatively or additionally, a voltage ripple can be lower the higher the frequency of the voltage source 202 (for example with subsequent rectification 204) from which the matching converter 206 is fed.

According to one embodiment, a frequency of a superimposed alternating voltage 218, for example a triangular voltage or a sawtooth voltage, can be between 0.5 Hz and 2 Hz. Alternatively or additionally, further frequencies of the superimposed alternating voltage 218 are possible, which correspond to a significantly slower change in the output direct voltage of the matching converter 206 and/or the input direct voltage of the LLC converter 100 than the responsiveness of the circuit unit (also: the LLC controller) 112 of the LLC converter. So the circuit unit (also: the LLC controller) 112 of the LLC converter 112 can control the output DC voltage (for example at the connections 220 in 2A , 2 B , 3 or 4 ) keep stable.

According to further initial examples, an input DC voltage of a voltage source (also: network) can be between 12 V and 800 V. Alternatively or additionally, an input alternating voltage of a voltage source 202 (for example with subsequent rectification 204) can comprise between 100 V and 500 V, in particular between 400 V and 500 V. For example, the three-phase AC voltage source 202 can be in the 2A , 2 B , 3 and 4 each provide a voltage between 400 V and 500 V to the rectifier 204.

According to further exemplary embodiments, the input DC voltage Vzk of the LLC converter is 100 in 2A , 2 B , 3 or 4 800V, on which a low-frequency alternating voltage 218 with an amplitude of ± 10 V to ± 20V and a frequency of 1 Hz is superimposed.

The voltage values and/or amplitudes mentioned in the exemplary embodiments, in particular of the (e.g. input and/or output) DC voltages, are exemplary. According to the invention, other voltage values and/or amplitudes can be superimposed with a suitably selected alternating voltage.

If the frequency spectrum were completely unimportant, then one would normally keep the input voltage of the LLC converter 100 as stable as possible. The fact that an alternating voltage 218 is now superimposed (also: modulated) for the frequency jitter is intuitively the opposite of conventional requirements because it disturbs the circuit unit (also: controller) 112 of the LLC converter 100. Alternatively or additionally, components can be subjected to greater loads than conventionally. For example, an input capacitor according to the invention may be designed for a higher voltage (e.g. a DC voltage plus the amplitude of the AC voltage) than conventionally. These disadvantageous effects can in particular limit parameters of the superimposed alternating voltage 218 in relation to parameters of the output voltage of the matching converter 206.

For example, with a superimposed alternating voltage 218 of 20 V (also: ±20 V peak voltage; short: ±20 Vpk) related to a direct voltage of 800 V (also: Vdc), a strong broadening of the peaks in the spectrum can be achieved and the device ( for example that Device 200-1; 200-2; 200-3) will still operate well and the components will not be overloaded.

According to a further exemplary embodiment, a superimposed alternating voltage 218 of 10 V (also: ±10 V peak voltage; short: ±10 Vpk) related to a direct voltage of 400 V (also: Vdc) is suitable for a strong broadening of the peaks in the spectrum without overloading Components of the device (for example the device 200-1; 200-2; 200-3).

According to yet another exemplary embodiment, a superimposed alternating voltage 218 of 4 V (also: ±4 V peak voltage; short: ±4 Vpk) relative to a direct voltage of 160 V (also: Vdc) is suitable for a strong broadening of the peaks in the spectrum without overloading of components of the device (for example the device 200-1; 200-2; 200-3). For example, the ratio can be calculated based on the exemplary embodiment of a direct voltage of 800 V with an overlaying alternating voltage 218 of 20 V as: (value of direct voltage in V)/800 V × 20 V = (permissible and/or suitable value of overlaying alternating voltage in V).

Unless otherwise specified, all exemplary embodiments can be combined with one another.

Although the invention has been described with reference to exemplary embodiments, it will be apparent to those skilled in the art that various changes may be made and equivalents substituted. Furthermore, many modifications can be made to adapt a particular situation or electrical power requirement to the teachings of the invention. Accordingly, the invention is not limited to the disclosed embodiments, but includes all embodiments that fall within the scope of the appended claims.

Reference symbol list

100

LLC converter

102

transformer

104-1; 104-2; 104-3

inductance

106-1; 106-2; 106-3

capacity

108

Semiconductor switch

110

diode

112

Circuit unit

200-1; 200-2; 200-3

Device for stable direct voltage supply

202

voltage source

204

rectifier

206

Matching converter

208

Control unit

210

Setpoint voltage

212

Actual voltage value

214

First resistance of the resistance bridge

216

Second resistance of the resistance bridge

218

Superimposed alternating voltage

219

Signal generator of the superimposed alternating voltage

220

Connections for stable DC voltage supply

222

Resistance

502

Frequency (abscissa)

504

Voltage value (ordinate)

506

Quasi-peak characteristic value

508

Average characteristic value

510

Quasi-peak measurement value in the state of the art

512

Average measurement value in the prior art

610

Quasi-peak measurement value according to the exemplary embodiment of the invention

612

Average measured value according to the exemplary embodiment of the invention

Claims (15)

Device (200-1; 200-2; 200-3) for stable DC voltage supply (220) comprising: a matching converter (206) which is connected on an input side of the matching converter (206) with a DC voltage source (202, 204) or an alternating voltage source (202) is electrically conductively connected or connectable; and an LLC converter (100), which is electrically conductively connected or connectable on an input side to an output side of the matching converter (206), wherein the LLC converter (100) is designed to provide a stable DC voltage supply (220) on an output side , wherein a DC voltage of the output-side stable DC voltage supply (220) is a function of a switching frequency of the LLC converter (100); wherein the matching converter (206) comprises a control unit (208) which is designed to superimpose an alternating voltage (218) on an output DC voltage of the matching converter (206); wherein an amplitude of the superimposed alternating voltage (218) is smaller than the output direct voltage; and wherein a frequency of the superimposed alternating voltage (218) is lower than the switching frequency of the LLC converter (100). Device (200-1-; 200-2; 200-3). Claim 1 , wherein the DC voltage source (202, 204) comprises a three-phase AC voltage source (202) and a rectifier (204) arranged between the three-phase AC voltage source (204) and the input side of the matching converter (206). Device (200-1; 200-2; 200-3). Claim 1 or 2 , wherein the matching converter (206) comprises a step-up converter, a step-down converter, and / or a step-up converter. Device (200-1; 200-2; 200-3) according to one of Claims 1 until 3 , wherein the superimposed alternating voltage (218) comprises a triangular voltage, a sine voltage, a sawtooth voltage and / or a square wave voltage. Device (200-1; 200-2; 200-3) according to one of Claims 1 until 4 , further comprising two series-connected resistors (214; 216) forming a voltage divider, the voltage divider being connected between both poles of the output side of the matching converter (206) and/or between both poles of the input side of the LLC converter (100), and wherein the control unit (208) of the matching converter (206) is designed to regulate the DC output voltage of the matching converter (206) depending on a voltage tapped at a node between the first resistor (214) and the second resistor (216) of the voltage divider. Device (200-1; 200-2). Claim 5 , further comprising a signal generator (219), which couples a control signal of the superimposed alternating voltage (218) into the tapped voltage, optionally via a third resistor (222), which has a first connection to the node between the first resistor (214) and the second resistor (216) of the voltage divider is connected in an electrically conductive manner, the third resistor (222) being electrically conductively connected to the signal generator (219) at a second connection. Device (200-1). Claim 6 , wherein the signal generator (219) is further electrically connected to one of the two poles of the output side of the matching converter (206) and / or to one of the two poles of the input side of the LLC converter (100), and / or wherein the signal generator (219 ) is arranged outside the matching converter (206). Device (200-1; 200-2). Claim 6 or 7 , whereby the control signal of the superimposed alternating voltage (218) is added to the voltage tapped via the voltage divider. Device (200-1; 200-2) according to one of Claims 5 until 8th , wherein the control unit (208) is designed to regulate the DC output voltage of the matching converter (206) depending on an actual voltage, the signal generator (219) coupling a control signal of the superimposed AC voltage (218) into the actual voltage, optionally where the control signal is added to an actual value in the control unit (208). Device (200-3) according to one of the Claims 5 until 8th , wherein the control unit (208) is designed to regulate the DC output voltage of the matching converter (206) depending on a target voltage, the signal generator (219) coupling a control signal of the superimposed alternating voltage (218) into the target voltage, optionally where the control signal is added to a constant setpoint in the control unit (208). Device (200-1; 200-2; 200-3) according to one of Claims 1 until 10 , wherein the superposition of the output voltage of the matching converter (206) with the superimposed alternating voltage (218) comprises an analog signal coupling and/or a digital signal coupling in the control unit (208). Device (200-1; 200-2; 200-3) according to one of Claims 1 until 11 , wherein the frequency of the superimposed alternating voltage (218) is between 0.5 Hz and 2 Hz, optionally wherein the frequency of the superimposed alternating voltage (218) is 1 Hz. Device (200-1; 200-2; 200-3) according to one of Claims 1 until 12 , wherein the output DC voltage of the matching converter is at least an integer multiple of the amplitude of the superimposed AC voltage (218); and/or wherein the DC output voltage of the matching converter is between 400 V and 800 V; and/or wherein the amplitude of the superimposed alternating voltage (218) is between 10 V and 20 V. Method for providing a stable DC voltage supply (220), comprising the steps: Adjusting a direct voltage from a direct voltage source (202, 204) or an alternating voltage from an alternating voltage source (202) by means of an adapting converter (206); Superimposing an output DC voltage of the matching converter (206) with an AC voltage (218); wherein an amplitude of the superimposed alternating voltage (218) is smaller than the output direct voltage of the matching converter (206); Converting the DC output voltage of the matching converter (206) superimposed on the AC voltage (218) by means of an LLC converter (100), the LLC converter (100) being designed to provide a stable DC voltage supply (220) on an output side, wherein a DC voltage the output-side stable DC voltage supply is a function of a switching frequency of the LLC converter (100); wherein a frequency of the superimposed alternating voltage (218) is lower than the switching frequency of the LLC converter (100); and Providing a stable DC voltage at the output side of the LLC converter (100). Procedure according to Claim 14 , further comprising the steps: rectifying an alternating voltage of an alternating voltage source (202) by means of a rectifier (204); and providing the rectified voltage as the DC voltage of the DC voltage source at an input side of the matching converter (206).

Images