DC-DC converter

Abstract

A method for operating a DC-DC converter (300) comprising a step-down / step-up converter (10) with an inductance (L) and a plurality of switching elements (S1-S4), comprising measuring a current (I) flowing through the inductance (L) and performing the following method steps: a) comparing the current with a first threshold current value (Ival), b) placing the buck-boost converter into a first switching state (BOOST ON) at the beginning of a switching cycle if the current is below the first threshold current value, or placing the buck-boost converter into a second switching state (BOOST OFF, BUCK ON) at the beginning of the switching cycle if the current is not below the first threshold current value, c) when the buck-boost converter is operated in the first switching state, comparing the current with the first threshold current value (Ival) and switching the buck-boost converter to the second switching state as soon as the current reaches the first threshold current value, d) when the buck-boost converter is operated in the second switching state, comparing the current with a second threshold current value (Ipk) which is greater than the first threshold current value, and setting the buck-boost converter to the third switching state (BUCK OFF) as soon as the current reaches the second threshold current value, and Repeat steps a) to d) after the specified period (Tc) has elapsed.

Description

[0001] The present invention relates to a DC-DC converter, in particular a DC-DC converter designed as a step-down converter (buck-boost converter), and to a method for controlling such a DC-DC converter.

[0002] Buck-boost converters can convert an input DC voltage into both a lower output voltage (buck operation) and a higher output voltage (boost operation).

[0003] In the prior art, buck-boost converters are known which contain an inductance and a plurality of switching elements which, by alternately switching, achieve the step-up or step-down of the input voltage.

[0004] Two methods are known in the art for controlling such buck-boost converters. In pulse width modulation (PWM), the switches are controlled with switching signals that have a predetermined duty cycle, i.e., a predetermined ratio between the on-time of a switching element and the period of a switching cycle. In peak current control, the current coil current is compared with a threshold value, and switching occurs when the coil current reaches the threshold value. The duty cycle can therefore change depending on the coil current.

[0005] In both cases, the control circuit of the switching elements must distinguish whether the converter is currently in boost or buck mode. Depending on the current operating state, the switching transistors contained in the buck-boost converter must be controlled differently.

[0006] In addition, the transition zone between buck-boost and step-down modes is difficult to control. The control circuit must cyclically switch between the two operating modes. Controlling the switching transistors, for example, via software, is therefore complex and time-consuming, but also time-critical.

[0007] US 2023 223 852 A1 describes such a DC-DC converter, its control in different operating modes and the switching between these operating modes.

[0008] It is an object of the present invention to provide a DC-DC converter and a method for controlling it which are improved over the prior art.

[0009] The problem is solved by the subject matter of the independent claims. Further developments of the invention are specified in the subclaims. The subject matter of an independent claim can also be further developed by features of the subclaims of another independent claim.

[0010] The method according to the invention is used to operate a DC-DC converter that includes a step-down / step-up converter with an inductor and a plurality of switching elements. A step-up operation is achieved by alternately switching the switching elements between a first switching state (BOOST ON) and a second switching state (BOOST OFF, BUCK ON), and a step-down operation is achieved by alternately switching between the second switching state (BOOST OFF, BUCK ON) and a third switching state (BUCK -OFF), wherein the switching between the switching states occurs periodically in switching cycles with a predetermined period duration. The method comprises measuring a current flowing through the inductor and performing the following method steps: a) comparing the current with a first threshold current value, b) placing the buck-boost converter into the first switching state at the beginning of a switching cycle if the current is below the first threshold current value, or placing the buck-boost converter into the second switching state at the beginning of the switching cycle if the current is not below the first threshold current value, c) when the buck-boost converter is operated in the first switching state, comparing the current with the first threshold current value and setting the buck-boost converter to the second switching state as soon as the current reaches the first threshold current value, d) when the buck-boost converter is operated in the second switching state, comparing the current with a second threshold current value which is greater than the first threshold current value and setting the buck-boost converter into the third switching state as soon as the current reaches the second threshold current value, and repeating steps a) to d) after the expiration of the predetermined period.

[0011] In an advantageous further development, the step-down / step-up converter is set to the first switching state before step a) or b).

[0012] In an advantageous further development, the step-down / step-up converter is placed into a fourth switching state at the end of the switching cycle before the expiration of the predetermined period duration, which fourth switching state is designed to regenerate internal supply voltages of driver circuits for the switching elements (S1, S3) connected to an input terminal or an output terminal of the step-down / step-up converter.

[0013] In an advantageous further development, the first threshold current value and / or the second threshold current value and / or the predetermined period duration are obtained from operating data of a system in which the DC-DC converter is used.

[0014] In an advantageous further development, the operating data of the system include maximum power point tracking data of a power generator and / or the maximum current for charging a power storage device and / or the maximum voltage for charging the power storage device.

[0015] The DC-DC converter according to the invention contains a step-down / step-up converter with an inductor and a plurality of switching elements, wherein a step-up operation is achieved by alternately switching the switching elements between a first switching state BOOST ON and a second switching state BOOST OFF, BUCK ON, and a step-down operation is achieved by alternately switching between the second switching state BOOST OFF, BUCK ON and a third switching state BUCK OFF, and a control device for controlling the DC-DC converter. The control device is configured or programmed to operate the DC-DC converter using the method according to the invention.

[0016] In an advantageous development, the step-down / step-up converter includes an input terminal for applying an input voltage, an output terminal for outputting an output voltage, and a common ground, wherein a first end of the inductance is connected to the input terminal via a first switching element and to ground via a second switching element, and a second end of the inductance is connected to the output terminal OUT via a third switching element and to ground GND via a fourth switching element.

[0017] In an advantageous development, in the first switching state the second and the third switching element are open and the first and the fourth switching element are closed and / or in the second switching state the second and the fourth switching element are open and the first and the third switching element are closed and / or in the third switching state the first and the fourth switching element are open and the second and the third switching element are closed and / or in the fourth switching state the first and the third switching element are open and the second and the fourth switching element are closed.

[0018] In an advantageous further development, the control device contains a microcontroller.

[0019] In an advantageous further development, the current is compared with the first threshold current value and / or with the second threshold current value by means of comparators integrated in the hardware of the microcontroller.

[0020] The power generation plant according to the invention contains a power generator for generating electrical energy at a first voltage, a power storage device for storing the electrical energy generated by the power generator at a second voltage and a DC-DC converter according to the invention.

[0021] The computer program according to the invention contains instructions which cause a control unit to generate control signals for carrying out a method according to the invention when the computer program is executed in the control unit.

[0022] Further features and advantages of the invention will become apparent from the description of an embodiment with reference to the accompanying drawings. Fig. Figure 1 shows a circuit diagram of a buck-boost converter suitable for carrying out the present invention. Fig. 2 shows a simplified circuit diagram of the buck-boost converter in boost mode, where Fig. 2a a switching state in BOOST-ON mode and Fig. 2b shows a switching state in BOOST-OFF mode. Fig. 3 shows a simplified circuit diagram of the buck-boost converter in buck mode, where Fig. 3a a switching state in BUCK-ON mode and Fig. 3b shows a switching state in BUCK-OFF mode. Fig. Figure 4 shows a simplified circuit diagram of the buck-boost converter in REFRESH mode. Fig. Figure 5 shows timing diagrams for operation of the buck-boost converter, where Fig. 5a Timing diagrams for boost operation and Fig. 5b shows timing diagrams for buck operation. Fig. 6 shows timing diagrams for operation of the buck-boost converter according to a method of the present invention. Fig. 7 shows an example of a current waveform during operation of the buck-boost converter according to the method of the present invention. Fig. Figure 8 shows a block diagram of a power generation plant incorporating a DC-DC converter according to the present invention.

[0023] An embodiment of the present invention will be described below with reference to the accompanying drawings.

[0024] An example of a buck-boost converter on which the present invention is based is shown in Fig. 1 shown.

[0025] The buck-boost converter 10 has an input terminal IN, an output terminal OUT, and a common ground GND. An input voltage U1 is applied between the input terminal IN and ground GND, and an output voltage U2 is output between the output terminal OUT and ground GND. A first capacitor C1 (input capacitor) is connected between the input terminal IN and ground GND, and a second capacitor C2 (output capacitor) is connected between the output terminal OUT and ground GND.

[0026] The buck-boost converter 10 contains an inductor L as a power storage element. A first end of the inductor L is connected to the input terminal IN via a first transistor T1 and a first diode D1, and to ground GND via a second transistor T2 and a second diode D2. A second end of the inductor L is connected to the output terminal OUT via a third transistor T3 and a third diode D3, and to ground GND via a fourth transistor T4 and a fourth diode D4. The transistors T1-T4 serve as switching elements of the buck-boost converter 10, and the diodes D1-4 serve as freewheeling diodes for the switching transistors.

[0027] With reference to Fig. 2-4, the different operating modes of the buck-boost converter 10 are explained below. Instead of the Fig. The switching transistors T1-T4 shown in Figure 1 with their antiparallel-connected freewheeling diodes D1-D4 generally represent switching elements S1-S4. The current path formed according to the switching states of the switching elements S1-S4 is represented in the figures by a line with an arrow.

[0028] A boost operation of the buck-boost converter 10 is achieved by alternately switching between a BOOST-ON mode and a BOOST-OFF mode. Fig. Figure 2 shows a simplified circuit diagram of the buck-boost converter 10 in boost mode, where Fig. 2a a switching state in BOOST-ON mode and Fig. 2b shows a switching state in BOOST-OFF mode.

[0029] In boost mode, switching element S1 is permanently closed (on), and switching element S2 is permanently open (off). The input voltage is boosted by alternately opening and closing switching elements S3 and S4.

[0030] In BOOST-ON mode, switching element S3 is open and switching element S4 is closed. In BOOST-OFF mode, switching element S3 is closed and switching element S4 is open.

[0031] A buck operation of the step-down-boost converter 10 is achieved by alternately switching between a buck-on mode and a buck-off mode. Fig. 3 shows a simplified circuit diagram of the buck-boost converter 10 in buck mode, where Fig. 3a a switching state in BUCK-ON mode and Fig. 3b shows a switching state in BUCK-OFF mode.

[0032] In buck mode, switching element S3 is permanently closed, and switching element S4 is permanently open. The input voltage is stepped down by alternately opening and closing switching elements S1 and S2.

[0033] In BUCK-ON mode, switching element S1 is closed and switching element S2 is open. In terms of the switching states of the individual switching elements S1-S4, BUCK-ON mode corresponds to BOOST-OFF mode. In BUCK-OFF mode, switching element S1 is open and switching element S2 is closed.

[0034] Since the switching states of the switching elements S1-S4 in BUCK-ON mode correspond to those in BOOST-OFF mode, only three of the four possible switching states are covered by the four modes described above. Fig. 4 shows a simplified circuit diagram of the buck-boost converter 10 in the fourth switching state.

[0035] The switching elements S1 and S3 are open, and the switching elements S2 and S4 are closed. This connects both ends of the inductor L to ground.

[0036] This state can be used to allow the driver circuits for the high-side switching elements S1 and S3 to regenerate their internal supply voltage using an internal boost circuit. It is therefore referred to as REFRESH mode and can be used additionally at the end of a switching cycle before the start of the next switching cycle.

[0037] Fig. 5 shows timing diagrams for an operation of the buck-boost converter (10) where Fig. 5a Timing diagrams for boost operation and Fig. Figure 5b shows timing diagrams for a buck mode. The switching elements S1-S4 are switched periodically in switching cycles with a period duration Tc.

[0038] In boost mode, at the beginning of a switching cycle, switching element S3 is opened and switching element S4 is closed, placing the buck-boost converter (10) in BOOST-ON mode. A continuously increasing current I flows from the input terminal IN through the inductor L to ground GND. This current I is measured and compared with a first threshold current value Ival.

[0039] As soon as the current I reaches the first threshold current value Ival, switching element S3 is closed and switching element S4 is opened, putting the buck-boost converter (10) into BOOST-OFF mode. The current I flowing from the input terminal IN through the inductor L flows into the capacitor and charges it. The current I continuously decreases.

[0040] In buck mode, at the beginning of a switching cycle, switching element S1 is closed and switching element S2 is opened, putting the buck-boost converter (10) into BUCK-ON mode. A current I flows from the input terminal IN through the inductor L into the capacitor, charging it. The current I increases continuously. This current I is measured and compared with a second threshold current value Ipk, which is greater than the first threshold current value Ival.

[0041] Although the BUCK-ON mode corresponds to the BOOST-OFF mode in terms of the switching states of the switching elements S1-S4, it differs from the latter in that the current I flowing through the inductance L increases in the BUCK-ON mode because the input voltage U1 is greater than the output voltage U2 in buck mode, while it decreases in the BOOST-OFF mode because the input voltage U1 is smaller than the output voltage U2 in boost mode.

[0042] Once the current I reaches the second threshold current value Ipk, the switching element S1 opens and the switching element S2 closes, putting the buck-boost converter (10) into BUCK-OFF mode. The current I flowing from the input terminal IN through the inductor L continues to flow into the capacitor and further charges it. The current I continuously decreases.

[0043] In the prior art, information received externally about the ratio between the input voltage U1 and the output voltage U2 is used to decide whether the buck-boost converter (10) is to be controlled in boost mode or buck mode, and the control is adapted accordingly.

[0044] In order to eliminate this disadvantage of the prior art, according to the present invention, a control with a time characteristic is realized as shown in Fig. 6 is shown.

[0045] In the Fig. According to the current curve shown in Figure 6, the current I flowing through the inductor L at the beginning of the switching cycle is less than the first threshold current value Ival. At the beginning of the switching cycle, the buck-boost converter 10 is placed in a first switching state corresponding to the BOOST-ON mode (switching elements S1 and S4 closed, switching elements S2 and S3 open). A continuously increasing current I flows from the input terminal IN through the inductor L to ground GND. This current I is measured and compared with the first threshold current value Ival.

[0046] As soon as the current I reaches the first threshold current value Ival, the buck-boost converter 10 is switched to a second switching state corresponding to the BOOST-OFF mode (switching elements S1 and S3 closed, switching elements S2 and S4 open). The current I flowing through the inductor L flows into the capacitor and charges it. This current I is measured and compared with the second threshold current value Ipk.

[0047] Depending on whether the input voltage U1 is smaller or larger than the output voltage U2, the current I decreases again or it continues to increase. Fig. 6, the current continues to rise, meaning the input voltage is higher than the output voltage.

[0048] Once the current I reaches the second threshold current value Ipk, the buck-boost converter 10 is switched to a third switching state corresponding to the BUCK-OFF mode (switching elements S2 and S3 closed, switching elements S1 and S4 open). The current I flowing from the input terminal IN through the inductor L continues to flow into the capacitor and continues to charge it, but continuously decreases.

[0049] After the specified period Tc has elapsed, the next switching cycle begins and the buck-boost converter 10 is returned to the first switching state.

[0050] Because the switching state in BOOST-OFF mode corresponds to that in BUCK-ON mode, the switching cycle includes the BUCK ON / BUCK OFF sequence, which achieves a step-down of the input voltage U1. The preceding BOOST-ON mode merely supports the subsequent BUCK-ON mode in charging the inductor L.

[0051] If, in an alternative time characteristic, the current I flowing through the inductor L drops again after switching to the second switching state, or at least does not rise to the second threshold current value Ipk, the second switching state is maintained until the specified period Tc expires. The switching cycle thus contains the sequence BOOST ON / BOOST OFF, which increases the input voltage U1.

[0052] If the current I flowing through the inductance L has already exceeded the first threshold current value Ival at the beginning of the switching cycle, the buck-boost converter 10 is immediately switched to the second switching state after being switched to the first switching state, according to the control described above. Alternatively, the buck-boost converter 10 can also be switched directly to the second switching state without first being switched to the first switching state.

[0053] Thanks to the switching state sequence described above, the control circuit of the switching elements no longer needs to distinguish whether the converter is currently in buck or boost mode, and it also no longer needs to perform the switching state sequence differently accordingly. Depending on how the current I flowing through the inductor L changes after switching to the second state, the correct operating mode is automatically selected: boost mode is selected via the BOOST ON / BOOST OFF sequence, and buck mode is selected via the BOOST ON / BUCK ON / BUCK OFF sequence, or simply BUCK ON / BUCK OFF.

[0054] Fig. Figure 7 shows an example of a time characteristic of the current I flowing through the inductance L. For simplicity, seven switching cycles 1-7 are shown, during which the ratio between input voltage U1 and output voltage U2 changes several times. In practice, such changes will extend over considerably more switching cycles because the voltage ratio changes only slightly during a period Tc.

[0055] In the first two switching cycles 1 and 2, the input voltage U1 is lower than the output voltage U2, and the buck-boost converter 10 operates in boost mode with the BOOST ON / BOOST OFF sequence. In switching cycle 3, the input voltage U1 has risen above the output voltage U2, and the buck-boost converter 10 goes into buck mode with the BOOST ON / BUCK ON / BUCK OFF sequence. In switching cycles 4 and 5, the buck-boost converter 10 continues to operate in buck mode with the BUCK ON / BUCK OFF sequence, with the current I in switching cycle 5 falling below the first current threshold value Ival due to the input voltage U1 falling below the output voltage U2. In switching cycles 6 and 7, the buck-boost converter 10 operates again in boost mode with the BOOST ON / BOOST OFF sequence.

[0056] The method described above greatly simplifies the control of the buck-boost converter. The switching states are activated in a sequence that depends on the measured coil current I. By initializing the converter in BOOST-ON mode, reliable and appropriate operation is achieved without the need to compare the input voltage U1 and the output voltage U2. External information as to whether the input voltage U1 is greater than the output voltage U2 or vice versa, and a change in the control of the switching states in response to this information, is therefore not required. This enables flexible and rapid switching between the two operating modes, particularly in the transition region between boost and buck operation.

[0057] The parameters required for the process, such as the first threshold current value Ival, the second threshold current value Ipk, or the period duration Tc, can be obtained, for example, with the help of an external control system (not shown) from the operating data of a system in which the DC-DC converter is used, such as a power generation system. This can include, for example, MPPT (Maximum Power Point Tracking) data from a solar power system or the maximum current or voltage for charging a battery.

[0058] Fig. Figure 8 shows a block diagram of a power generation plant 100. The power generation plant 100 includes a power generator 200, a DC-DC converter 300, and a power storage device 400.

[0059] The power generator 200 supplies electrical energy with a variable DC voltage U1. It can be configured, for example, as a solar panel, in which the DC voltage U1 depends on the current solar radiation and is therefore subject to strong fluctuations.

[0060] The power storage device 400 serves to store the electrical energy supplied by the power generator 200. It can be configured, for example, as a rechargeable battery. The charging voltages suitable for charging the battery are generally within a relatively narrow voltage range.

[0061] The DC-DC converter 300 is used to convert the DC voltage U1 supplied by the power generator 200 into a charging voltage U2 suitable for charging the battery. Depending on the magnitude of the DC voltage U1 currently supplied by the power generator 200, it must operate in boost mode or buck mode.

[0062] The DC-DC converter 300 includes a buck-boost converter 10 as described above and a controller 20 configured or programmed to control the DC-DC converter 300 by means of the method described above with reference to Fig. 6 described procedure.

[0063] The control device can be embodied, for example, as a microcontroller. It includes a first digital-to-analog converter 31 for generating an analog value of the first threshold current value Ival and a second digital-to-analog converter 32 for generating an analog value of the second threshold current value Ipk. As described above, these values ​​can be obtained, for example, via a digital control system from the operating data of the power generation plant 100 and subsequently provided to the analog comparators by means of the digital-to-analog converters 31, 32.

[0064] The control device further includes a first comparator 41 for comparing a measured value of the measured coil current I with the first threshold current value Ival and a second comparator 42 for comparing a measured value of the measured coil current I with the second threshold current value Ipk. Depending on the comparison results, the central processing unit (CPU) 50 of the microcontroller generates the control signals for switching the switching elements S1-S4 with the timing characteristics described above.

[0065] Hardware comparators of the microcontroller 20 are preferably used as comparators 41, 42, and the digital values ​​of the threshold currents are written into the registers of these comparators 41, 42. Compared to a software comparison, the speed is significantly increased, which is particularly important for the time-critical switching of the switching elements.

[0066] The circuit is short-circuit-proof on the output side because the coil current I is maintained at a set value by the hardware. Since the hardware maintains the coil current I at the set value until the software specifies new reference values, the timing requirements and the speed of the controller are uncritical. The external controller can therefore run significantly slower and operate at a frequency lower than that resulting from the period Tc of the switching cycles. LIST OF REFERENCE SYMBOLS 1-7 switching cycles 10 buck-boost converters 20 Control device 50 CPU 31, 32 Digital / analog converter 41, 42 Comparators 100 power generation plants 200 power generator 300 DC-DC converters 400 power storage units BOOST ON, BOOST OFF, BUCK ON, BUCK OFF, REFRESH switching states C1, C2 capacitors D1-D4 freewheeling diodes GND Ground I coil current IN input connector Ipk second threshold current value Ival first threshold current value L Inductance OUT output connector S1-S4 switching elements T1-T4 switching transistors Tc cycle duration, period duration U1 input voltage U2 output voltage QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This 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

[0000] US 2023 223 852 A1

[0007]

Claims

[1] A method for operating a DC-DC converter (300) comprising a step-down / step-up converter (10) having an inductance (L) and a plurality of switching elements (S1-S4), wherein a step-up operation is achieved by alternately switching the switching elements between a first switching state (BOOST ON) and a second switching state (BOOST OFF, BUCK ON) and a step-down operation is achieved by alternately switching between the second switching state (BOOST OFF, BUCK ON) and a third switching state (BUCK -OFF), wherein the switching between the switching states takes place periodically in switching cycles with a predetermined period (Tc), the method comprising: Measuring a current (I) flowing through the inductance (L), Carry out the following procedural steps: a) comparing the current (I) with a first threshold current value (Ival), b) setting the buck-boost converter (10) to the first switching state (BOOST ON) at the beginning of a switching cycle if the current (I) is below the first threshold current value (Ival), or setting the buck-boost converter (10) to the second switching state (BOOST OFF, BUCK ON) at the beginning of the switching cycle if the current (I) is not below the first threshold current value (Ival), c) when the buck-boost converter (10) is operated in the first switching state (BOOST ON), comparing the current (I) with the first threshold current value (Ival) and setting the buck-boost converter (10) to the second switching state (BOOST OFF, BUCK ON) as soon as the current (I) reaches the first threshold current value (Ival), d) when the buck-boost converter (10) is operated in the second switching state (BOOST OFF, BUCK ON), comparing the current (I) with a second threshold current value (Ipk) which is greater than the first threshold current value (Ival), and setting the buck-boost converter into the third switching state (BUCK OFF) as soon as the current (I) reaches the second threshold current value (Ipk), and repeating steps a) to d) after the expiry of the predetermined period (Tc). [2] Method for operating a DC-DC converter (300) according to claim 1, wherein the step-down / step-up converter (10) is placed in the first switching state (BOOST ON) before step a). [3] Method for operating a DC-DC converter (300) according to claim 1 or 2, wherein the step-down / step-up converter (10) is placed into a fourth switching state (REFRESH) at the end of the switching cycle before the expiration of the predetermined period (Tc), which is designed to regenerate internal supply voltages of driver circuits for the switching elements (S1, S3) connected to an input terminal (IN) or an output terminal (OUT) of the step-down / step-up converter (10). [4] Method for operating a DC-DC converter (300) according to one of claims 1 to 3, wherein the first threshold current value (Ival) and / or the second threshold current value (Ipk) and / or the predetermined period duration (Tc) are obtained from operating data of a system (100) in which the DC-DC converter (300) is used. [5] Method for operating a DC-DC converter (300) according to claim 4, wherein the operating data of the system (100) comprise maximum power point tracking data of a power generator (200) and / or the maximum current for charging a power storage device (400) and / or the maximum voltage for charging the power storage device (400). [6] DC-DC converter (300) comprising a step-down / step-up converter (10) having an inductance (L) and a plurality of switching elements (S1-S4), wherein a step-up operation is achieved by alternately switching the switching elements between a first switching state (BOOST ON) and a second switching state (BOOST OFF, BUCK ON) and a step-down operation is achieved by alternately switching between the second switching state (BOOST OFF, BUCK ON) and a third switching state (BUCK OFF), and a control device (20) for controlling the DC-DC converter, wherein the control device (20) is configured or programmed to operate the DC-DC converter (100) by means of a method according to one of claims 1 to 5. [7] DC-DC converter (300) according to claim 6, wherein the step-down converter (10) includes an input terminal (IN) for applying an input voltage (U1), an output terminal (OUT) for outputting an output voltage (U2) and a common ground (GND), a first end of the inductance (L) is connected to the input terminal (IN) via a first switching element (S1) and to ground (GND) via a second switching element (S2), and a second end of the inductance (L) is connected to the output terminal OUT via a third switching element (S3) and to the ground GND via a fourth switching element (S4). [8] DC-DC converter (300) according to claim 7, wherein in the first switching state (BOOST ON) the second and third switching elements (S2, S3) are open and the first and fourth switching elements (S1, S4) are closed and / or in the second switching state (BOOST OFF, BUCK ON) the second and fourth switching elements (S2, S4) are open and the first and third switching elements (S1, S3) are closed and / or in the third switching state (BUCK OFF) the first and fourth switching elements (S1, S4) are open and the second and third switching elements (S2, S3) are closed and / or in the fourth switching state (REFRESH) the first and third switching elements (S1, S3) are open and the second and fourth switching elements (S2, S4) are closed. [9] DC-DC converter (300) according to one of claims 6 to 8, wherein the control device (20) includes a microcontroller. [10] DC-DC converter (300) according to claim 9, wherein the comparison of the current (I) with the first threshold current value (Ival) and / or with the second threshold current value (Ipk) is carried out by means of comparators integrated in the hardware of the microcontroller. [11] Power generation plant (100) comprising a current generator (200) for generating electrical energy with a first voltage (U1), a power storage device (400) for storing the electrical energy generated by the power generator (200) at a second voltage (U2) and a DC-DC converter (300) according to one of claims 6 to 10. [12] A computer program comprising instructions which cause a control unit (20) to generate control signals for carrying out a method according to any one of claims 1 to 5 when the computer program is executed in the control unit (20).

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