DE102013005070A1 - Boost converter - Google Patents

Abstract

A step-up converter, for example for use in a solar inverter circuit, has several inputs (10a, 10b) and one output (24). The output (24) is connected to each of the several inputs via a positive lead and a negative lead. At least one throttle (12a, 12b) is arranged in the positive feed line and / or the negative feed line of each input. At least one rectifying element (16a, 16b) is arranged in the positive feed line and / or the negative feed line of each input. The inputs (10a, 10b) can be connected in series by means of at least one series switching element (14, 14a, 14b) and each can be short-circuited by means of at least one boost switching element (18a-18c) via the chokes (12a, 12b) connected to them.

Description

The present invention relates to a boost converter with a plurality of inputs, a circuit arrangement with such a boost converter, an inverter circuit with such a boost converter or such a circuit arrangement and a method for operating such a boost converter.

Step-up converters are often used in power supplies of various kinds to boost DC voltages to a higher potential, whereby the transmission ratio can be varied.

Such power supplies may include at least one inverter. Inverters usually require a relatively constant intermediate circuit voltage for good efficiency. To adapt to highly variable input voltages, as they often occur, for example, in solar generators, therefore, often a boost converter is used.

1 shows the basic form of a conventional boost converter. It consists of the switching element 18 and the freewheeling diode 16 , which in the form of a half-bridge parallel to the output 24 are switched, and a throttle 12 with the center of the half bridge 16 . 18 and a pole of the entrance 10 connected is. The capacities 20 and 22 parallel to the connections 10 and 24 serve for buffering ripple currents.

To increase the DC voltage at the input 10 becomes the switching element 18 switched on and off in rapid succession (timed). When the switching element is switched on 18 is the entrance 10 over the throttle 12 shorted. Energy flows into the throttle 12 , which in the subsequent freewheeling phase via the diode 16 directly to the exit 24 is delivered. As long as the switching element 18 is switched on, no energy flows from the input to the output. The mode of operation of this boost converter is referred to below as "boost mode".

The conventional boost converter after 1 can also be built in a complementary manner. In this case, positive pole and negative pole are at input 10 and exit 24 reversed and the freewheeling diode 16 is connected inverted.

2 shows a boost converter with dual input, as it is for example in the DE 10 2008 050 402 A1 is disclosed. He has two entrances 10a . 10b and an exit 24 , Both inputs 10a . 10b each have a throttle 12a . 12b and a rectifying element 16a . 16b parallel to the output 24 connected. In addition, both inputs are above the chokes 12a . 12b by means of a switching element (hereinafter referred to as series switching element) 14 in series switchable. The capacities 20a . 20b and 22 parallel to the connections 10a . 10b and 24 serve for buffering ripple currents.

The operation of this dual boost converter is hereinafter referred to as "dual-mode".

Is the voltage at the inputs 10a . 10b between 50% and 100% of the voltage at the output 24 so becomes the series switching element 14 clocked. With closed series switching element 14 are the inputs 10a . 10b in series with the exit 24 connected, with electricity in the chokes 12a . 12b and the exit 24 flows. With the series switching element open 14 are the inputs 10a . 10b parallel, with the throttles 12a . 12b the previously stored energy via the rectification elements 16a . 16b to the exit 24 submit. Characteristic of the dual mode is the series connection of at least two inputs 10a . 10b which is not given in the above boost mode.

If the input voltage is 100% of the output voltage, then the series switching element 14 open so the two entrances 10a . 10b static parallel. If the input voltage is 50% of the output voltage, then the series switching element 14 closed, the two entrances 10a . 10b are static in series. In both cases, no switching losses occur.

In contrast to the boost converter after 1 Energy flows from the input side at all times 10a . 10b to the exit 24 , The in the chokes 12a . 12b energy to be stored and the ripple currents in the capacitor 22 are therefore significantly reduced. In addition, the voltage swings on the throttles 12a . 12b halved, reducing the switching losses per translated power in the switching element 14 be reduced. As a result, the efficiency increases sharply. In addition, the construction volume, weight and costs for components and cooling are significantly reduced.

3 shows another conventional dual boost converter, such as in the DE 10 2010 006 124 A1 is disclosed. Construction and operation are similar to the boost converter 2 , However, the series switching element is 14 by two series switching elements in series 14a . 14b replaced, which at their common connection point with a center MP of a divided output capacitor 22a . 22b are connected. Since the shared output capacitor causes a decoupling, both can be switching elements 14a . 14b if necessary, clock asynchronously, which may result in an additional degree of freedom in the scheme.

4 shows a still further conventional dual boost converter, as for example in the DE 10 2011 011 329 A1 is disclosed. Construction and operation are similar to the boost converter 3 , However, here are the series switching elements 14a respectively. 14b each with a pole of an input 10b respectively. 10a instead of being connected to a midpoint MP of a divided output capacitor. The series connection of the inputs 10a . 10b can therefore have both throttles 12a . 12b be done in parallel, which halves the current per throttle, so that the losses can be reduced.

In the 2 to 4 shown dual boost converter are distinguished from the basic circuit of 1 by a better efficiency with low component costs. However, the maximum output voltage can be as high as the sum of the voltages at the inputs 10a . 10b , which corresponds to a voltage increase by a factor of two for symmetrical operation. For solar panels, an input voltage range of 1: 2 at full load is usually sufficient. This requirement is offset by the conventional dual boost converters 2 to 4 usually well covered. In some cases, for example partial shading of solar generators, however, boosting by more than a factor of two may be desired.

In addition, current and / or voltage imbalances of the feeding sources in these conventional boost converter limited compensation. In the case of solar systems, there is the danger, in particular in the case of an unfavorable design of the solar generators, that it is no longer possible, starting from a certain degree of asymmetry, at the inputs 10a . 10b connected generators in their respective point maximum power point (MPP) to operate.

It is the object of the invention to provide an improved boost converter, which allows a voltage boosting by more than a factor of two and / or can be operated with asymmetry of the solar generators with good efficiency.

This object is achieved by the teaching of the independent claims. Particularly preferred embodiments and further developments of the invention are the subject of the dependent claims.

The boost converter according to the invention has a plurality of inputs, to each of which at least one DC voltage source can be connected, and a common output for providing a DC voltage. The common output is connected to each of the plurality of inputs via a positive lead and a negative lead, wherein in the positive lead and / or the negative lead from each input at least one throttle is arranged and in the positive lead and / or the negative lead at least one rectifying element is arranged from each input. The multiple inputs are thus operable in parallel with respect to the common output. In addition, at least two of the plurality of inputs can be connected in series by means of at least one series switching element. Preferably, all inputs by means of at least one series switching element in series can be switched.

According to the invention, at least one boost switching element is connected in parallel with at least one of the plurality of inputs for short-circuiting this input via the throttle connected to it. Preferably, at least one boost switching element is connected in parallel to all inputs for short-circuiting the respective input via the throttle connected to it.

The additionally created possibility of short-circuiting one or more inputs by means of boost switching elements via the throttle connected to the respective input, the boost converter can optionally - depending on the current operating conditions - be operated in one of several operating modes. The boost converter according to the invention can therefore also be referred to as a hybrid boost converter.

These multiple operating modes, i. H. preferably a boost mode, a dual mode and a combined boost dual mode, are explained in more detail below. In this way it is possible, as needed, to achieve a voltage boost by more than a factor of two and / or to operate the boost converter even with significant asymmetries of the DC voltages provided at the inputs with good efficiency.

The boost converter has several, d. H. two, three, four or more inputs. At each of these inputs, at least one, i. H. one, two, three or more, connected in series or parallel DC voltage sources. In this context, a "DC voltage source" is to be understood as any type of device or circuit which provides a DC voltage. DC sources in this sense include, but are not limited to, solar generators, fuel cells, thermoelectric generators, batteries, supercapacitors, electromagnetic generators, AC / DC converters, DC / DC converters, and the like.

In this context, a switching element is to be understood as any type of device or electronic component which is suitable for optionally closing or disconnecting an electrical connection. The switching elements are preferably semiconductor switching elements or power semiconductor switches, preferably MOSFETs, IGBTs, JFETs, cascode circuits and the like. The terms "series switching element" and "boost switching element" are used only to distinguish the switching elements according to their positioning and task in the circuit arrangement, but not necessarily a distinction in terms of their nature, their structure, etc. The series switching elements and the boost Switching elements are preferably circuit breakers that can be clocked at fixed or variable frequency.

The switching elements are preferably controlled by control electronics. The control electronics are preferably constructed analog, digital or as a mixed digital-analog controller. The switching elements are preferably driven periodically, wherein the clock frequencies are selected so that adjusts a (e) desired (r) current or voltage at the output of the DC-DC converter. The timing of the switching elements is preferably carried out by means of pulse width modulation with a fixed or variable frequency. The current in the chokes can be regulated to a continuous or a lopsided course.

In a preferred embodiment of the invention, the plurality of inputs are each switchable via a single series switching element in series.

In another preferred embodiment of the invention, the boost converter has at least one auxiliary potential. In addition, at least two series-connected switching elements are provided for series connection of two inputs, wherein their common connection point is connected to the auxiliary potential.

The auxiliary potential allows an asynchronous operation of two interconnected series switching elements. This results in an additional degree of freedom in the control, which can be used with asymmetrical supply of the inputs. If an auxiliary potential with a subsequent module, for. B. an inverter is connected, asymmetries that occur in the inverter or in the boost converter, can be compensated by the other module.

In another preferred embodiment of the invention, when the inputs are connected in series, at least two of the chokes connected to the respective inputs can be connected in parallel.

In a preferred embodiment of the invention, a further rectifying element for decoupling is connected in series with a series switching element (hereinafter also referred to as decoupling element) in order to protect the series switching element from negative voltages. Alternatively, reverse blocking switching elements can be used, in which case the decoupling elements can then be omitted.

Semiconductor diodes are preferably used for the rectifying elements and / or the decoupling elements. However, active rectification elements can also be used to achieve lower flux losses. With active rectification elements it is also possible to reverse the flow of energy, i. H. a bidirectional operation is possible.

In a preferred embodiment of the invention, the negative pole of an input is connected to the negative pole of the output and the positive pole of another input is connected to the positive pole of the output. With this configuration, radio interference can be reduced because the inputs have no potential jumps with respect to the output. But there are also other circuit arrangements conceivable.

The chokes of the boost converter are preferably designed as separate reactors, so that an asynchronous operation of the series switching elements and the boost switching elements and thus an operation with unbalanced supply is fully possible. If only small asymmetries are expected, the chokes can also be coupled. The series switching elements are then preferably clocked synchronously. This also applies to the boost switching elements. It is also conceivable to use throttles with taps.

Parallel to the inputs and / or the common output, at least one buffer capacitor is preferably connected in each case in order to buffer the ripple currents.

In addition, measures or means for the currentless and / or de-energized switching of the series switching elements and / or the boost switching elements of the boost converter are preferably provided.

In a preferred embodiment of the invention, a device for carrying out a maximum power point (MPP) tracking of the DC voltage sources connected to the inputs of the boost converter is additionally provided. The Control electronics for driving the switching elements is preferably part of this device.

The hybrid boost converter of the present invention may be used as a combination of at least one conventional boost converter 1 , this also in modified, z. B. in complementary or symmetrical form, and at least one dual boost converter are considered, with throttles and rectifying elements are partially shared by the Teil-Hochsetzstellern and additionally preferably at least one decoupling element is provided.

The combination according to the invention of the various partial boost converters in a single hybrid boost converter first makes it possible to carry out each of the typical operating modes for the relevant sub boost converter.

In a first mode, the series switching elements are permanently switched off while at least one of the boost switching elements is clocked. The relevant boost switching element part boost converter then works in the known boost mode. However, the efficiency is relatively poor in boost mode. This mode of operation may, however, be necessary or advantageous in the case of extremely asymmetrical feeding of the inputs, eg. B. if only one input is supplied.

In a second operating mode, the boost switching elements are permanently switched off. The hybrid boost converter then works in dual mode. This is characterized by a very high efficiency and is therefore to be preferred in principle.

The dual-mode can be used in particular when supplied from predominantly symmetrical sources with voltages in the range between 50% and 100% of the output voltage. But it is also possible in asymmetrical operation. For example, sources with the same current and different input voltages can be connected in series or sources with different voltages below the output voltage and / or different currents can be boosted to the output voltage.

In dual mode, however, the output voltage can not be boosted by the sum of the input voltages. In addition, asymmetries in the sources supplying the inputs can only be compensated to a limited extent.

In the boost converter according to the invention, however, the series switching elements and the boost switching elements can also be operated in combination with one another, whereby the restrictions applicable to conventional and dual boost converters can be overcome.

A preferred type of clocking will first be described for symmetrical feed operation and for a two input hybrid pull-up converter.

If the input voltage is between 50% and 100% of the output voltage, the hybrid boost converter operates in the well-known dual mode. The duty cycle of the series switching elements increases from 0% with static parallel connection of the inputs to up to 100% with static series connection of the inputs.

If the input voltage is below 50% of the output voltage, according to the invention the series switching elements can remain permanently closed, while additionally the boost switching elements are clocked. The duty cycle of the boost switching elements is higher, the lower the input voltage.

Theoretically, an arbitrarily high boost of the input voltages is possible. In contrast to the boost mode of a conventional boost converter after 1 the voltage swing at the chokes is much smaller, because the freewheel is no longer against the high potential of the output. As a result, the switching losses are greatly reduced, the efficiency is increased. The dual mode can thus be extended to the range of input voltages below 50% of the output voltage.

If the unbalance of the supplying sources is too large, a power surplus may remain at one of the inputs.

In this case, both operating modes, boost mode and dual mode, can be combined. This can be done alternately in separate clock cycles within the same clock cycles or in rapid succession.

Because of the better efficiency preferably the highest possible proportion of the power is translated in dual mode. For this purpose, the series switching elements are turned on as often and / or as long as possible.

The remaining power surplus can then be translated in boost mode.

The boost switching element, which is connected to the input at which there is a power surplus, is turned on only as often as necessary to reduce the power surplus, respectively, to the source connected to that input in the MPP bring. The The series switching element connected to this boost switching element is only opened as often or as long as necessary to transfer the power surplus directly to the output.

The boost switching element, which is connected to the input at which there is no power surplus, is turned on as rarely and / or briefly. If the input voltage is high enough, it can be left completely off.

In this combined mode of operation, only the excess power component resulting from an imbalance is transmitted in boost mode, ie with poor efficiency. Since there is often a relatively high symmetry between the generators of a solar system, the efficiency of the hybrid boost converter according to the invention in most cases is higher than if only one or more conventional boost converter after 1 be used.

The invention also relates to a circuit arrangement which includes a boost converter of the invention described above in combination with a dual up-down converter.

This combination results in a hybrid up-down converter with an extremely wide input voltage range. For example, the circuit topologies suitable in the DE 10 2011 018 357 A1 are described, without the present invention being limited to these combinations.

The hybrid boost converter of the invention or the described circuit arrangements with such a hybrid boost converter are advantageously suitable for feeding DC consumers or DC networks and for use in inverter circuits, in particular in solar inverter circuits.

The invention therefore also relates to an inverter circuit having at least one step-up converter of the invention and / or at least one circuit arrangement of the invention, and at least one inverter for converting the DC voltage provided at the output of the step-up converter or the circuit arrangement into an AC voltage.

In a preferred embodiment of the invention, a DC link of the inverter is connected to at least one auxiliary potential of the boost converter, so that a balance of imbalances by the boost converter and / or the inverter is possible.

In a preferred embodiment of the invention, two or more hybrid boost converter or circuit arrangements according to the invention can also be connected in parallel, in series or in cascade.

Finally, the invention also relates to a method for operating a boost converter having at least two inputs, to each of which at least one DC voltage source can be connected, and a common output for providing a DC voltage, in particular a boost converter of the invention described above, wherein the common output with each of a plurality of inputs in each case via a positive supply line and a negative supply line is connected, wherein in the positive supply line and / or the negative supply line of each input at least one throttle is arranged, wherein in the positive supply line and / or the negative supply line of each input at least one Rectifying element is arranged, and wherein the at least two inputs are switchable by means of at least one series switching element in series. According to the invention, at least one input is short-circuited via the throttle connected to this input by means of at least one boost switching element.

With regard to the special features, advantages, definitions of terms and preferred embodiments of this method, reference is made to the above statements in connection with the boost converter according to the invention for the sake of simplicity.

In a preferred embodiment of the invention, the series switching elements are permanently closed and the boost switching elements clocked synchronously or asynchronously, if the input voltages at the inputs fall below a certain value.

In a preferred embodiment of the invention, the series switching elements are turned on as often and / or as long as possible in order to transmit the highest possible power component with high efficiency.

In a preferred embodiment of the invention, the at least one boost switching element, which is connected to an input at which there is a power surplus, is turned on only as often as necessary to reduce the power surplus, and becomes connected to this boost switching element at least one series switching element only as often or as long as it is necessary to transfer the power surplus directly into the output.

In a preferred embodiment of the invention, the clock frequency of the series Switching elements and / or the boost switching elements lowered when the input voltages are in the range of about 50% or about 100% of the output voltage.

The above and other features and advantages of the invention will become more apparent from the following description of preferred, non-limiting embodiments thereof with reference to the accompanying drawings. Show:

1 a schematic diagram of a conventional boost converter;

2 a schematic diagram of a first conventional dual boost converter;

3 a schematic diagram of a second conventional dual boost converter;

4 a schematic diagram of a third conventional dual boost converter;

5 a schematic diagram of a boost converter according to a first embodiment of the present invention, wherein the inputs via a single series switching element in series can be switched;

6 a schematic diagram of a boost converter according to a second embodiment of the present invention, in which an auxiliary potential is present;

7 a schematic diagram of a boost converter according to a third embodiment of the present invention, in which the inputs via two parallel switchable throttles are connected in series;

8th a simplified schematic diagram of a boost converter according to a fourth embodiment of the present invention with three inputs;

9 a simplified schematic diagram of a boost converter according to a fifth embodiment of the present invention;

10 a schematic diagram of an exemplary circuit combination of a boost converter according to the invention with a solar inverter;

11 a schematic diagram of a conventional dual up-down converter;

12 a schematic diagram of another conventional dual up-down converter;

13 a schematic diagram of a first combination of a boost converter according to the invention with a dual up-down converter; and

14 a schematic diagram of a second combination of a boost converter according to the invention with a dual up-down converter.

Basic configurations and modes of operation of the boost converter according to the invention are described below with reference to a in 5 illustrated first embodiment explained.

The boost converter has two inputs 10a . 10b and an exit 24 , to each of which a DC voltage is applied. The negative pole of the first input 10a is directly to the negative pole of the output 24 connected. The positive pole of the first input 10a is over a throttle 12a and a rectifying element 16a with the positive pole of the output 24 connected. The positive pole of the second input 10b is directly with the positive pole of the output 24 connected. The negative pole of the second input 10b is over a second throttle 12b and a second rectifying element 16b with the negative pole of the output 24 connected. Both inputs 10a . 10b are thus relative to the output 24 operated in parallel.

The inputs 10a . 10b are by means of a series switching element 14 switchable in series. In series with this series switching element 14 is a decoupling element 19 to protect the series switching element 14 provided against negative voltages. Alternatively, for the series switching element 14 a reverse blocking switching element can be used, in which case then on the decoupling element 19 can be waived.

Both the rectification elements 16a . 16b as well as the decoupling element 19 are for example semiconductor diodes. However, active rectification elements such as semiconductor switches can be used to achieve lower flux losses. With active rectification elements, it is also possible to reverse the flow of energy, ie to allow bidirectional operation.

Parallel to the entrances 10a . 10b and the exit 24 there is one buffer capacitor each 20a . 20b . 22 to buffer the ripple currents.

Furthermore, both inputs 10a . 10b in each case via the chokes connected to them 12a . 12b with the help of boost switching elements 18a . 18b short-circuited. The series switching element 14 and the boost switching elements 18a . 18b are circuit breakers that can be clocked at fixed or variable frequency, eg. As semiconductor switches such as IGBTs, MOSFETs, JFETs or semiconductor combinations such as Cascode circuits. They can have external or internal antiparallel freewheeling diodes.

The hybrid boost converter can take energy from the inputs 10a . 10b to the exit 24 transfer. Various types of direct current sources are conceivable as feeding sources, such as solar generators, fuel cells, thermoelectric generators, batteries, batteries, supercapacitors, electromagnetic generators, AC / DC converters, DC / DC converters and the like.

At the output consumers can be connected. As consumers and assemblies are possible, which pass the energy, z. As inverters or battery chargers.

Are the rectifying elements 16a . 16b and the decoupling element 19 designed as synchronous rectifying elements, so a reverse energy flow is possible. An example would be z. B. charging and discharging of batteries.

Furthermore, a control unit or control electronics (not shown) is present, which the current and / or the voltage at the inputs 10a . 10b and / or at the exit 24 controls or regulates by the series switching element 14 and the boost switching elements 18a . 18b , in the case of synchronous rectifiers also the rectifying elements 16a . 16b and the decoupling element 19 clocked drives. The control unit can also be used to perform an MPP tracking of the connected generators or to regulate the voltage at at least one auxiliary potential.

Control units for switched-mode power supplies can, for. B. analog, digital or mixed digital-analog hybrid controller be constructed. The timing of the power semiconductors z. B. by means of pulse width modulation with fixed or variable frequency. The current in the chokes can be regulated to a continuous or discontinuous course. Such control units are well known to the skilled person and are therefore not described further.

The hybrid boost converter from 5 represents a combination of a conventional boost converter 1 , a complement of the conventional boost converter 1 and a conventional dual boost converter 2 , where the throttles 12a . 12b and the rectifying elements 16a . 16b be shared and additionally a decoupling element 19 in series with the series switching element 14 is available.

The combination of the three different partial boost converters in a single hybrid boost converter makes it possible to carry out each of the typical operating modes for the boost converter in question:
In a first mode, the series switching element 14 permanently off while at least one of the boost switching elements 18a . 18b is clocked. The conventional boost converter included in the circuit 1 and / or its complement can then work independently of each other in the known boost mode. However, the efficiency is relatively poor in this boost mode. This mode of operation may be necessary for extremely unbalanced power supply, z. If only one of the inputs 10a . 10b is supplied.

In a second mode, the boost switching elements 18a . 18b permanently switched off. The hybrid boost converter then works like the well-known dual boost converter from 2 in dual mode. This is characterized by a very high efficiency and is therefore to be preferred in principle.

The dual-mode can be used in particular when supplied from predominantly symmetrical sources with voltages in the range between 50% and 100% of the output voltage. But it is also possible in asymmetrical operation.

For example, sources with the same current and different input voltages can be statically connected in series. Despite imbalance, both sources can be operated in their MPP, if those at the output 24 applied sum voltage from a subsequent module, for. As an inverter is regulated.

Also, a high voltage source may feed the output directly (ie without boosting) while the lower voltage of a second source is boosted to the output voltage. Both sources can be operated in their MPP if those at the output 24 voltage is controlled by a subsequent module and the voltage of the second source is controlled by the dual boost converter.

Furthermore, sources with different voltages below the output voltage and / or different currents can be boosted to the output voltage. Because only a single series switching element 14 but it is not possible to set the MPP separately for both sources. Instead, the dual boost converter can be controlled to set a common MPP for the entire circuitry. By introducing at least one further, separately clockable series switching element, as in the circuits of 3 . 4 . 6 and 7 , creates an additional degree of freedom for the Control, so that a separate MPP tracking of the sources is possible.

However, the output voltage in this mode can not be boosted by the sum of the input voltages. In addition, imbalances of the inputs 10a . 10b feeding sources are only partially compensated. The lower the voltages at the inputs 10a . 10b the more difficult it is to balance out asymmetries. Returns one of the sources 10a . 10b no electricity at all, so the voltage of the other source can not be increased. This extreme case occurs, for example, when snow is covered by two connected solar generators.

According to the invention, the series switching element 14 and the boost switching elements 18a . 18b but also operable in combination with each other, whereby the existing restrictions for conventional and dual boost converter can be overcome.

A preferred type of timing is initially for symmetrical feed operation 10a . 10b described.

If the input voltage is between 50% and 100% of the output voltage, the hybrid boost converter operates in the well-known dual mode. The duty cycle of the series switching element 14 increases from 0% with static parallel connection of the inputs 10a . 10b up to 100% with static series connection of the inputs.

If the input voltage is below 50% of the output voltage, the series switching element remains according to the invention 14 permanently closed while in addition the boost switching elements 18a . 18b preferably be clocked synchronously. The duty cycle of the boost switching elements 18a . 18b is higher, the lower the input voltage.

Theoretically, an arbitrarily high boost of the input voltages is possible. In contrast to the boost mode of a conventional boost converter after 1 is the voltage swing at the chokes 12a . 12b halved, since the freewheel is no longer against the high potential of the output 24 he follows. As a result, the switching losses are greatly reduced, which increases the efficiency. The dual mode is thus extended to the range of input voltages below 50% of the output voltage.

If the unbalance of the supplying sources is too large, the input at one of the inputs, for example at the input, may be too large 10b , source connected to their MPP while those at the other input 10a connected source does not yet deliver its maximum available power. At the entrance 10a then exists a surplus of power.

In this case, both operating modes, boost mode and dual mode, can be combined. So it is z. B. at excess power at the entrance 10a the boost switching element 18a more often and / or longer turned on to the current in the choke 12a increase and thereby reduce the surplus. The series switching element 14 can be opened more often and / or longer, allowing the series connection with the input 10b or the dual mode is temporarily interrupted in favor of the boost mode. Ie. the surplus is at the entrance 10b over to the exit 24 passed, so that at the entrance 10b connected source is not overloaded by a too high current or brought out of their MPP.

Boost mode and dual mode can be alternately executed in rapid succession in separate clock cycles. The input-side capacitors 20a . 20b can serve as a buffer for the fluctuating energy. The greater the power surplus at one of the inputs, the more frequently clock cycles can be executed in boost mode.

It is also possible to execute boost mode and dual mode within the same clock cycles. This is z. B. at excess power at the entrance 10a the boost switching element 18a Switched on longer within one clock cycle. The series switching element 14 can be opened longer in the same cycle to increase the direct free-wheeling of the throttle 12a to the exit 24 to allow, bypassing the series connection with the input 10b ,

Because of the better efficiency preferably the highest possible proportion of the power is translated in dual mode. This is the series switching element 14 as often as possible (in many clock cycles) and / or as long as possible (within one clock cycle) switched on.

Only the remaining power surplus is translated in boost mode: exists for example at the entrance 10a a surplus power, so is the boost switching element 18a turned on only as often or as long as necessary to reduce the excess power and bring the connected source in the MPP. That with the boost switching element 18a connected series switching element 14 is opened only as often or as long as it is necessary to transfer the excess power directly into the output 24 to guide and the entrance 10b not to overload.

The boost switching element 18b that with the entrance 10b on the other hand, it is switched on only rarely and / or briefly, as it is necessary to the energy from the entrance 10b dissipate. Often it can stay completely off.

When the series switching element is switched on 14 a part of the current flows out of the choke 12a into the throttle 12b so that the boost switching element 18a respectively. 18b when switching only charged with the differential current. Therefore, the switching losses decrease.

In this combined mode of operation, only the excess power component resulting from an imbalance is transmitted in boost mode, ie with poor efficiency. Since there is often a relatively high symmetry between the generators of a solar system, the efficiency of the hybrid boost converter according to the invention in most cases is higher than if only one or more conventional boost converter after 1 be used.

When with symmetrical supply of the inputs 10a . 10b the voltage ratio approaches 100% or 200%, the current ripple in the chokes drops - with the switching elements at constant switching frequency 12a . 12b more and more. The clock frequency can therefore be lowered more and more in order to minimize the switching losses. In extreme cases, ie with a voltage ratio of exactly 100% or 200%, the inputs 10a . 10b static parallel or in series. The timing can then be suspended, so that no more switching losses occur.

If the inductor current is regulated by means of a two-point regulator with constant hysteresis, that is to say with a constant ripple current, such a frequency reduction results automatically. By suitable design of the controller, z. B. by a variation of the hysteresis or limitation of the switching times for the clocking, too strong a decrease in the clock frequency, z. B. in the listening area, be avoided.

Also with asymmetrical feeding of the inputs 10a . 10b the clock frequency can be reduced in a similar way. In order to achieve optimum efficiency, it may then be useful to the chokes 12a . 12b operate at different frequencies. However, here are limitations, since only a single series switching element 14 to clock both throttles is present. This limitation can be eliminated by adding further series switching elements, which will be discussed below.

Since the DC component of the inductor current increases with decreasing input voltage and constant power, it is advantageous if the ripple current decreases in parallel thereto. The throttle can then be designed for a smaller maximum current. Therefore, it may be advantageous to lower the clock frequency only moderately at low input voltages.

At the boost converter of 5 is one pole of the inputs 10a . 10b directly to the exit 24 connected. In this way, potential jumps between the inputs and the output are prevented, which minimizes the radio interference. However, the hybrid boost converter of the invention is not limited to this arrangement. For example, the throttle 12a into the negative supply of the input 10a be inserted instead of in the positive. This arrangement is functional, but then has the entrance 10a in pulsed operation strong potential jumps compared to the output 24 on.

To reduce the switching losses may additionally be provided means which the switching of the series switching element 14 and / or the boost switching elements 18a . 18b allow in current and / or voltage zero crossing.

Additionally, means, e.g. As relays, be present to bridge static components in certain operating conditions to prevent the flow losses in these devices. For example, with a voltage ratio of 100%, the rectifier elements 16a . 16b and / or the throttles 12a . 12b be bridged. With static series connection of the inputs, the series switching element can 14 , the decoupling element 19 and / or the throttles 12a . 12b be bridged. If the boost switching elements are not clocked, the decoupling element can 19 be bridged. When the series switching element 14 permanently closed, it can also be bridged statically.

It can also be provided bypass elements, which is the positive pole of the input 10a directly to the positive pole of the output 24 and the negative pole of the input 10b directly to the negative pole of the output 24 connect. At high input voltage, they bridge the series connection from choke 12a and rectifying element 16a as well as the series connection of throttle 12b and rectifying element 16b , As bypass elements are, for example, semiconductor diodes with very low forward voltage. Since the bypass elements are not clocked, they need not have short switching times.

The throttles 12a . 12b of the hybrid boost converter are typically designed as separate reactors, thus an asynchronous operation of the boost switching elements 18a . 18b and thus the operation with unbalanced power supply is fully possible. If only small asymmetries occur, the chokes can 12a . 12b be coupled. The boost switching elements 18a . 18b are then preferably clocked synchronously.

It is also conceivable to use throttles with tapping. For example, the boost switching elements 18a respectively. 18b and the decoupling element 19 or the series switching element 14 each with a tap of the throttle 12a respectively. 12b be connected while the rectifying elements 16a respectively. 16b as in 5 shown at the output ends of the chokes 12a respectively. 12b are connected. As a result, inter alia, the current and / or voltage loads of the components move. There are other possibilities of interconnection for throttles with tap, analogous to the known circuits for boost or buck converter with tapped chokes, which are known in the art.

If an imbalance of the feeding sources is established from the outset, in some cases, the boost switching element can 18a or 18b be dispensed with, which with the entrance 10a respectively. 10b which is fed from the weaker source.

At high source voltage, it may, for. B. in case of defect of the series switching element 14 to an unwanted permanent series connection of the inputs 10a . 10b and thus an inadmissibly high voltage at the output 24 come. To prevent this, protective devices can be installed, as they are for. B. in the DE 10 2011 011 329 A1 are described.

Two or more of the hybrid boost converter according to the invention can be connected in parallel. In this case, the individual hybrid boost converters can be operated out of phase to reduce the ripple currents (multiphase operation). In addition, at partial load individual hybrid boost converter can be completely switched off to increase the partial load efficiency. It is also possible to connect or cascade two or more hybrid boost converters in series.

Various other embodiments of the hybrid boost converter of the invention will now be referred to 6 to 9 described. Essentially, only their special properties are emphasized. Nevertheless, of course, in these other embodiments - as readily apparent to one skilled in the art - the above in connection with 5 explained detail solutions implemented.

6 shows a second embodiment of the hybrid boost converter according to the invention. This embodiment provides a combination of a conventional boost converter 1 , a complement of the boost converter after 1 and a dual boost converter 3 , where the throttles 12a . 12b and the rectifying elements 16a . 16b be shared.

In contrast to 5 is at the exit 24 an auxiliary potential MP present, in this case by means of a divided output capacitor 22a . 22b is produced. The common series switching element 14 out 5 is also by two series series switching elements 14a . 14b replaced, with their connection point is connected to the auxiliary potential MP. In series with each of the series switching elements 14a . 14b is also a decoupling element 19a . 19b ,

With symmetrical supply, the voltage at this auxiliary potential MP preferably corresponds to half the output voltage. But it is also an unbalanced voltage distribution at the capacitors 22a . 22b possible, for. B. when the inputs 10a . 10b different voltages, but have the same currents and are statically connected in series. However, it may be useful to limit the voltage imbalance. The dielectric strength of the capacitors 22a . 22b , the series switching elements 14a . 14b and the decoupling elements 19a . 19b can then be chosen smaller.

By clamping on the auxiliary potential MP, the voltage swing at the chokes 12a . 12b and the stress of the components 14a . 14b and 19a . 19b reduced.

The auxiliary potential MP decouples with the throttle 12a connected components 16a . 19a . 14a . 18a of those with the throttle 12b connected components 16b . 19b . 14b . 18b , The switching elements 14a and 18a can therefore be asynchronous to the switching elements 14b and 18b operate. As a result, it is possible, for example, to operate the switching elements with different, respectively optimized clock frequencies and duty cycles and if necessary to perform a separate MPP tracking of the two sources. The voltages and currents at the inputs can be different. However, care should be taken that the average of the current flowing into the auxiliary potential MP is zero, so that its potential does not run away.

For example, if the auxiliary potential can no longer be kept stable due to asymmetrical feeding, there is the possibility to connect the auxiliary potential MP with a subsequent module, for example, the center of the intermediate circuit of a neutral-point-clamped inverter. In this way, asymmetries that occur in the inverter and / or in the hybrid boost converter, can be compensated by the other module.

Alternatively or additionally, there may be a power surplus at one of the inputs 10a . 10b as for the circuit in 5 described be degraded by the operation in boost mode. Unlike the circuit of 5 However, the opening of the series switching elements 14a respectively. 14b so controlled that excess power not into the auxiliary potential MP, but directly to the output 24 passed and the auxiliary potential MP is kept constant thereby.

7 shows a third embodiment of the hybrid boost converter according to the invention. This embodiment provides a combination of a conventional boost converter 1 , a complement of the boost converter after 1 and a conventional dual boost converter 4 , where the throttles 12a . 12b and the rectifying elements 16a . 16b be shared.

In contrast to 6 , is the series switching element 14a with the negative pole of the input 10b connected and is the series switching element 14b with the positive pole of the input 10a connected. Thus, when connecting the inputs in series 10a . 10b both throttles 12a . 12b in parallel, causing the currents and flux losses in the reactors to drop.

Again, the switching elements 14a and 18a asynchronous to the switching elements 14b and 18b operate.

The hybrid boost converter of the invention may have any number of inputs. 8th shows by way of example a fourth embodiment of the invention with three inputs.

The blocks 15a and 15b stand for the various possible circuits shown here for the series switching elements and their environment or supply lines, as is shown in detail 2 to 4 evident. They allow the serial connection of the inputs as before 10a . 10b and 10c ,

The middle entrance 10c preferably has both a throttle and a rectifying element in both the positive feed line and in the negative feed line ( 12c and 16c respectively. 12d and 16d ). Both throttles 12c and 12d are via the boost switching element 18c short-circuited.

The freewheel is via the rectifying elements 16a - 16d against the exit 24 , Thus, the inputs 10a - 10c each as before, both in series switchable as well as in parallel with the output 24 operated.

There are three inputs 10a - 10c can be switched in series, there is a voltage increase by a factor of three instead of the previously two factor with symmetrical power supply. Apart from that, the operation in a similar way as for the circuits of 5 respectively. 6 or 7 respectively.

9 shows a fifth embodiment of the hybrid boost converter according to the invention. This contains a dual boost converter. block 15 stands for the not shown here in detail series switching elements and their environment or supply lines, as z. B. off 2 to 4 evident.

In contrast to the previous embodiments, the boost switching elements 18a . 18b via separate throttles 12e . 12f with the entrances 10a . 10b connected. In addition, the freewheeling of these chokes via separate rectifying elements 16e . 16f , In this arrangement, the sharing of chokes and rectifying elements is dispensed with.

Preferably, the largest possible part of the input power with the help of the more efficient dual partial boost converter (components 12a . 12b . 16a . 16b and block 15 ) processed. The remaining power due to imbalances at one of the inputs 10a respectively. 10b is by clocking the respectively associated circuit branch 12e . 16e . 18a respectively. 12f . 16f . 18b on the exit 24 translated.

This embodiment of the hybrid boost converter has the disadvantage that as a rule a high component complexity is necessary. If, however, a relatively high symmetry of the inputs is given and the input voltages are above 50% of the output voltage, the complementary partial boost converters (components 12e . 16e . 18a and 12f . 16f . 18b ) transmitted only small services and can be manufactured inexpensively.

The dual partial boost converter 12a . 12b . 15 . 16a . 16b can be optimized for the transmission of purely symmetrical power, reducing the chokes 12a . 12b can be built smaller. In addition, decoupling elements for the series switching elements can be omitted. The efficiency increases as a result.

For a given asymmetry, in some cases one of the two partial boost converters can be used 12e . 16e . 18a respectively. 12f . 16f . 18b be waived from the outset.

In an advantageous embodiment of the invention, the hybrid boost converter according to the invention can be combined with a dual high-buck converter to a hybrid high-buck converter with extremely wide input voltage range.

For example, the circuit topologies suitable in the DE 10 2011 018 357 A1 are described, without the present invention being limited to these combinations. On the entire disclosure content of this aforementioned document is hereby incorporated by reference.

Two examples of such a conventional dual buck-boost converter are in 11 and 12 shown. Both buck-boost converters can lower voltages as much as they like, but can only boost voltages up to a factor of two. The buck converter function is via the switching elements 44a . 44b and the rectifying elements 46 respectively. 46a . 46b reached. The rectifying elements 46 . 46a . 46b can be designed as a synchronous rectifier to reduce losses or to allow bidirectional operation. They effect a series connection of the chokes 12a . 12b , whereby the voltage swings on these chokes and on the associated switching elements 44a . 44b be lowered. This increases the efficiency.

By combining such dual buck-boost converters with the hybrid boost converter of the present invention, hybrid buck-boost converters as in FIG 13 and 14 which are now additionally able to control the voltage at the inputs 10a . 10b to increase more than a factor of two - theoretically arbitrarily strong.

The combination arises from the fact that at the output poles of the chokes 12a . 12b additional boost switching elements 18a . 18b be connected, through which the inputs 10a . 10b over the throttles 12a . 12b and the switching elements 44a . 44b are short-circuited. The boost switching elements 18a respectively. 18b are with the entrances 10a respectively. 10b connected. In addition, decoupling elements 19 . 19a . 19b in series with the series switching elements 14 . 14a . 14b be inserted if they are not reverse blocking.

In addition, on the input side of the chokes the rectifying elements 46 . 46a . 46b additional decoupling elements 49 . 49a . 49b connected in series. These can be z. B. semiconductor switches such as IGBTs, MOSFETs, etc. be. They are opened when the sum of the input voltages is lower than the output voltage, with closed switching elements 44a . 44b a short circuit across the rectifier elements 46 respectively. 46a . 46b to prevent. Are the decoupling elements 49 . 49a . 49b reverse blocking, so can on the rectifying elements 46 . 46a . 46b be waived.

The function of the thus constructed hybrid up-down converter is with symmetrical supply as follows.

Is the voltage at the inputs 10a . 10b at least 50% of the voltage at the output 24 , the hybrid up-down converter works preferably as in DE 10 2011 018 357 A1 described. The boost switching elements 18a . 18b are open, the decoupling elements 49 . 49a . 49b are closed.

Is the voltage at the inputs 10a . 10b less than 50% of the voltage at the output 24 , so are the switching elements 44a . 44b as well as the series switching elements 14 respectively. 14a . 14b permanently closed while the decoupling elements 49 . 49a . 49b be opened. The boost switching elements 18a . 18b are clocked. The higher the duty cycle, the stronger the voltage boost.

It can additionally rectifier elements 48a . 48b be present as exemplified in 13 shown. The rectifying element 48a is with the input side pole of the choke 12a and the negative pole of the input 10a connected. The rectifying element is analogous to this 48b with the input side pole of the throttle 12b and the positive pole of the input 10b connected. The rectifying elements can, for. B. semiconductor diodes or active rectifier.

By adding these rectifying elements 48a . 48b The hybrid buck-boost converter is fully capable of having single-ended sources at the inputs 10a . 10b to work.

As an extreme case of an asymmetry, a case will be described below, if only at the input 10a a feeding source is present.

Is the voltage at the input 10a more than 100% of the output voltage, so will the switching element 44a clocked, which in conjunction with the rectifying element 48a works in the manner of a conventional buck converter. The decoupling element 49 , the series switching element 14 and the boost switching element 18a preferably remain open.

Is the voltage at the input 10a less than 100% of the output voltage, so does the switching element 44a permanently closed. The boost switching element 18a is clocked and works in Connection to the rectifier element 16a in the manner of a conventional boost converter after 1 , The decoupling element 49 and the series switching element 14 preferably remain open.

Thus, the buck-boost converter operates in the manner of a classic buck-boost converter without using the rectifying element 46 and the series switching element 14 , which is a series connection of the chokes 12a . 12b or the inputs 10a . 10b enable. The efficiency is relatively poor.

However, once at least a partial symmetry at the entrances 10a . 10b is given, the efficiency of the hybrid up-buck converter can be increased. For this purpose, the operation is preferably carried out in a comparable manner, as has already been described for the operation of the hybrid boost converter of the invention. The decoupling element 49 and the switching element 14 are turned on as often as possible or as often as possible, since then the voltage strokes to the chokes 12a . 12b are small, whereby the efficiency increases.

The intended in particular for the processing of one-sided power surges boost switching elements 18a . 18b and the rectifying elements 48a . 48b are switched on or energized only infrequently or for as short a time as is necessary to transmit unilateral power surpluses.

The hybrid boost converter from 14 unlike that of 13 via an auxiliary potential MP, which with the decoupling elements 49a . 49b and the series switching elements 14a . 14b connected is. This auxiliary potential MP allows the asynchronous operation of the two chokes 12a . 12b by asynchronous timing of each associated with the chokes switching elements.

As will be readily apparent to those skilled in the art, other combinations are possible for such hybrid up-down converters, including based on the circuit of 7 , Here, too, in predominantly symmetrical operation, the chokes 12a . 12b be coupled. Furthermore, it is conceivable to use throttles with taps. So z. B. the rectifying elements 46a respectively. 46b with one tap each of the throttles 12a respectively. 12b be connected while the switching elements 44a respectively. 44b as in 14 shown with the input-side connections of the throttles 12a . 12b are connected. Again, there are other possibilities of interconnection for throttles with tap, analogous to the known circuits for boost or buck converter with tapped chokes.

The hybrid boost converter of the invention and the above-described circuit arrangements with this hybrid boost converter can be used, for example, for direct supply of DC consumers or DC networks or for charging and discharging energy storage. Since no conversion takes place in alternating current and back into direct current, the efficiency of such systems is particularly high. They are therefore increasingly used, especially in connection with renewable energy sources.

The hybrid boost converter of the invention and its combinations with dual buck-boost converters can also be used to power DC bus in other devices such. B. inverters. An inverter usually needs an intermediate circuit voltage of a certain height to generate an alternating voltage. Optimum efficiency is achieved when the intermediate circuit voltage is precisely matched to the alternating voltage to be generated.

Inverters are often used for solar power. However, depending on the amount of light, temperature and number of modules connected, solar generators deliver a strongly fluctuating DC voltage. The wider the range of DC input voltage that an inverter can handle, the more options the installer will have to find matching solar panel combinations.

The hybrid step-up converter according to the invention and the described circuit arrangements with this hybrid step-up converter can convert the varying DC voltage of solar generators to an approximately constant DC link voltage. It is also possible to modulate the intermediate circuit voltage with a superimposed alternating component, which can be advantageous for the optimum adaptation of the inverter.

Compared to the state of the art 1 the efficiency is increased. Compared to the state of the art 2 to 4 higher gear ratios and unbalanced operation are possible without restrictions. The potentials at the inputs can be kept constant. This is important because the potential of a solar generator for electro-magnetic compatibility should not be high-frequency jumps.

Various inverter topologies can be used in conjunction with the hybrid boost converter according to the invention. Both single-phase and multi-phase inverters can be used. Inverters can be used to feed isolated networks or to feed into a power grid. The hybrid boost converter can perform an MPP tracking of the feeding solar generators.

10 shows a possible inverter arrangement with a hybrid step-up converter according to the invention 5 ,

With the entrances 10a . 10b of the hybrid boost converter are solar generators 30a . 30b connected. Their variable voltage is using the hybrid boost converter to a relatively constant voltage at the output 24 or at the DC link of the inverter 32 set high.

LIST OF REFERENCE NUMBERS

10, 10a, 10b, 10c

inputs

12, 12a-12f

throttle

14, 14a, 14b

Serial switching elements

15, 15a, 15b

circuit blocks

16, 16a-16f

Rectifying members

18, 18a-18c

Boost switching elements

19, 19a, 19b

decoupling elements

20, 20a-20c

Buffer capacitors at the input

22, 22a, 22b

Buffer capacitors at the output

24

output

30a, 30b

solar generators

32

inverter

44a, 44b

switching elements

46, 46a, 46b

Rectifying members

48a, 48b

Rectifying members

49, 49a, 49b

decoupling elements

MP

Focus

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008050402 A1 [0007]
• DE 102010006124 A1 [0012]
• DE 102011011329 A1 [0013, 0125]
• DE 102011018357 A1 [0055, 0150, 0156]

Claims (14)

Boost converter, with several inputs ( 10a - 10c ), to each of which at least one DC voltage source can be connected, and a common output ( 24 ) for providing a DC voltage, the common output ( 24 ) with each of the multiple inputs ( 10a - 10c ) is connected in each case via a positive feed line and a negative feed line, wherein in the positive feed line and / or the negative feed line from each input at least one throttle ( 12a - 12d ) is arranged, wherein in the positive feed line and / or the negative feed line from each input at least one rectifying element ( 16a - 16d ) and at least two of the inputs ( 10a - 10c ) by means of at least one series switching element ( 14 . 14a . 14b ) are switchable in series, characterized in that parallel to at least one of the plurality of inputs ( 10a - 10c ) at least one boost switching element ( 18a - 18c ) for shorting this input ( 10a - 10c ) via the throttle connected to it ( 12a - 12d ) is switched. A boost converter according to claim 1, wherein at least two of the inputs ( 10a - 10c ) by means of a series connection of at least two series switching elements ( 14a . 14b ) are connected in series whose common connection point is connected to an auxiliary potential (MP). A boost converter according to claim 1, wherein in the case of series connection of two inputs ( 10a - 10c ) at least two of these inputs ( 10a - 10c ) connected chokes ( 12a - 12d ) are switchable in parallel. Step-up converter according to one of the preceding claims, in which in series with the series switching element ( 14 . 14a . 14b ) another rectifying element ( 19 . 19a . 19b ) connected for decoupling and / or the series switching element ( 14 . 14a . 14b ) is configured as a reverse blocking switching element. Step-up converter according to one of the preceding claims, in which the inputs ( 10a - 10c ) rectifying elements ( 16a - 16d ) and / or in series with the series switching elements ( 14 . 14a . 14b ) connected further rectifying elements ( 19 . 19a . 19b ) Are synchronous rectifiers and an inverse flow of energy is possible. Step-up converter according to one of the preceding claims, in which a negative pole of an input ( 10a ) with a negative pole of the output ( 24 ) and a plus pole of another input ( 10 . 10c ) with a positive pole of the output ( 24 ) connected is. Circuit arrangement, comprising a step-up converter according to one of claims 1 to 6 in combination with a dual up-down converter. Inverter circuit comprising at least one step-up converter according to one of Claims 1 to 6 and / or at least one circuit arrangement according to Claim 7, and at least one inverter ( 32 ) for converting the at the output ( 24 ) of the boost converter or the circuit arrangement provided DC voltage in an AC voltage. An inverter circuit according to claim 8, wherein a DC link of the inverter ( 32 ) is connected to at least one auxiliary potential (MP) of the boost converter and compensation of imbalances by the boost converter and / or the inverter is possible. Method for operating a boost converter with at least two inputs ( 10a - 10c ), to each of which at least one DC voltage source can be connected, and a common output ( 24 ) for providing a DC voltage, in particular a boost converter according to one of claims 1 to 5, wherein the common output ( 24 ) with each of the multiple inputs ( 10a - 10c ) is connected in each case via a positive feed line and a negative feed line, wherein in the positive feed line and / or the negative feed line of each input at least one throttle ( 12a - 12d ) is arranged, wherein in the positive feed line and / or the negative feed line from each input at least one rectifying element ( 16a - 16d ), and wherein the at least two inputs ( 10a - 10c ) by means of at least one series switching element ( 14 . 14a . 14b ) are switchable in series, characterized in that at least one input ( 10a - 10c ) by means of at least one boost switching element ( 18a - 18c ) via the throttle connected to this input ( 12a - 12d ) is short-circuited. Method according to Claim 10, in which the series switching elements ( 14 . 14a . 14b ) permanently closed and the boost switching elements ( 18a - 18c ) can be clocked synchronously or asynchronously if the input voltages at the inputs ( 10a - 10c ) fall below a certain value. Method according to Claim 10 or 11, in which the series switching elements ( 14 . 14a . 14b ) As often as possible and / or as long as possible to transfer the highest possible power share with high efficiency. Method according to one of claims 10 to 12, wherein the at least one boost switching element ( 18a - 18c ), with an entrance ( 10a - 10c ), where there is a power surplus, is only turned on as often as necessary to reduce the power surplus and with this boost switching element ( 18a - 18c ) connected at least one series switching element ( 14 . 14a . 14b ) is opened only as often or as long as necessary to bring the excess power directly into the output ( 24 ) transferred to. Method according to one of Claims 10 to 13, in which the clock frequency of the series switching elements ( 14 . 14a . 14b ) and / or the boost switching elements ( 18a - 18c ) is lowered when the input voltages are in the range of about 50% or about 100% of the output voltage.

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