Dc / dc converters with combined current and voltage regulation

Abstract

The invention relates to a DC-DC converter arrangement comprising at least one DC-DC converter, wherein the DC-DC converter comprises a current control and a voltage control. According to the invention, for the current control, a first component is provided for control based on the primary-side current at the DC / DC converter, and a second component is provided for control based on the secondary-side current at the DC / DC converter.

Description

[0001] Description

[0002] title

[0003] DC / DC CONVERTER WITH COMBINED CURRENT AND VOLTAGE CONTROL

[0004] Technical area

[0005] The present invention relates to a DC-DC converter device and a method for operating a DC-DC converter device.

[0006] State of the art

[0007] Vehicles that are fully or at least partially electrically powered usually have an electrical energy storage device, such as a traction battery. This traction battery provides the electrical energy required to drive the electric vehicle. The traction battery usually delivers an output voltage of several hundred volts and feeds what is known as a high-voltage network of the vehicle. In addition, such a vehicle usually comprises several electrical consumers that are supplied with a lower electrical voltage via a low-voltage network. To couple the high-voltage network and the low-voltage network, and in particular to transfer electrical energy from the high-voltage network to the low-voltage network, so-called DC-DC converters can be provided, which convert an electrical DC voltage from the high-voltage network into a DC voltage for the low-voltage network.

[0008] The publication DE 2009 028 147 A1 describes a circuit arrangement for an on-board power supply of an electric vehicle, wherein a DC / DC converter is provided for coupling between two on-board power supplies.

[0009] Disclosure of the invention

[0010] The present invention discloses a DC-DC converter device and a method for operating a DC-DC converter device having the features of the independent patent claims. Further advantageous embodiments are the subject of the dependent patent claims.

[0011] Accordingly, it is provided:

[0012] A DC-DC converter device comprising at least one DC-DC converter and a control device. The at least one DC-DC converter is configured to convert an input DC voltage into an output DC voltage. The control device comprises a voltage regulator and a current regulator. The voltage regulator is configured to determine a first controlled variable for the DC-DC converter using a setpoint for the output voltage of the DC-DC converter and a measured value for the output voltage of the DC-DC converter. The current regulator comprises a first control device and a second control device. The first control device is configured to determine a first current controlled variable using an electrical current at the input of the DC-DC converter.The second control device is configured to determine a second current control variable using an electrical current at the output of the DC-DC converter. The current controller is configured to determine a second control variable using the first current control variable and the second current control variable. Finally, the control device is configured to control the DC-DC converter using a combination of the first control variable and the second control variable.

[0013] Furthermore, it is planned:

[0014] A method for operating a DC-DC converter device having at least one DC-DC converter. The method comprises a step of determining a first controlled variable using a setpoint for the output voltage of the DC-DC converter and a measured value for the output voltage of the DC-DC converter. The method further comprises a step of determining a first current controlled variable using an electrical current at the input of the DC-DC converter.Furthermore, the method comprises a step of determining a second current control variable using an electrical current at the output of the DC-DC converter, a step of determining a second control variable for the DC-DC converter using the first current control variable and the second current control variable, and a step of controlling the at least one DC-DC converter using a combination of the first control variable and the second control variable.

[0015] Advantages of the invention

[0016] The present invention is based on the finding that the electrical current on the output or secondary side can also be taken into account for the control of a DC-DC converter. Particularly if a transformer is included in the DC-DC converter, a conversion must be performed to calculate the output current limit, taking into account the transformer's transformation ratio. However, such a conversion requires a certain amount of computing time, which can lead to delays in the control process. Such delays can potentially lead to oscillations in the system.

[0017] Therefore, one idea of ​​the present invention is to take this finding into account and create a controller structure for a DC-DC converter arrangement that exhibits robust control behavior. To this end, the invention provides for two separate parts for current control within the control structure. In particular, a separate current control is provided for the input or primary-side current and the output or secondary-side current. In this way, the detected current values ​​can be fed directly to the respective control structures without the need for a computationally intensive conversion.

[0018] In particular, the electrical currents on the primary or input side and the secondary or output side can be considered independently for current control. Such a control structure with separate current controllers for the primary or input side and the secondary or output side makes it easier to implement hardware protection requirements, such as the necessary current limits. In particular, sensor and component tolerances have less influence on system behavior.

[0019] According to one embodiment, the current controller is designed to select the smaller of the first current control variable and the second current control variable as the second control variable. In other words, the current controller selects the minimum of the two current control variables, each determined with respect to the primary and secondary sides of the DC-DC converter, as the control variable. This ensures that the DC-DC converter is always operated below the maximum permissible current.

[0020] According to one embodiment, the first control device is designed to determine the first current control variable using a comparison of the electrical current at the input of the DC-DC converter with a predetermined setpoint for the electrical current at the input of the DC-DC converter. Accordingly, the second control device can be designed to determine the second current control variable using a comparison of the electrical current at the output of the DC-DC converter with a predetermined setpoint for the electrical current at the output of the DC-DC converter. Furthermore, in this case, the current controller can be designed to determine the second control variable using the minimum of the first current control variable and the second current control variable. In this way, the current controller can be implemented particularly simply and efficiently.

[0021] According to one embodiment, the first control device and the second control device of the power converter are each designed to output a control signal if the corresponding control device is active in an operating mode in which a maximum current in the DC-DC converter is limited. The voltage regulator is designed to adjust the first controlled variable using the control signal from the current regulator. This makes it possible to limit or suspend voltage regulation in the voltage regulator if the current regulation in the current regulator limits the DC-DC converter.

[0022] According to one embodiment, the DC-DC converter device comprises a plurality of DC-DC converters. A separate current regulator is provided for each DC-DC converter of the DC-DC converter device. Furthermore, a common voltage regulator is provided for all DC-DC converters of the DC-DC converter device. In this way, the power of the DC-DC converter device can be increased by connecting a plurality of DC-DC converters in parallel. The separate current regulation for each DC-DC converter allows the total power to be easily distributed between the individual voltage regulators.

[0023] According to one embodiment, the DC-DC converter comprises a flyback DC-DC converter. Since such flyback DC voltages incorporate a transformer in their power supply, the separate current regulation for the primary or input side and the secondary or output side allows the transformation ratio of the transformers used to be easily and efficiently incorporated into the current regulation.

[0024] According to one embodiment, the control device is designed to output a duty cycle for pulse width modulation as a controlled variable for controlling the DC-DC converter. This enables pulse width modulation (PWM) control of the DC-DC converter in a simple manner.

[0025] The above embodiments and further developments can be combined with one another as desired, where appropriate. Further embodiments, further developments, and implementations of the invention also include combinations of features of the invention not explicitly mentioned above or described below with respect to the exemplary embodiments. In particular, those skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

[0026] Short description of the drawings

[0027] Further features and advantages of the invention are explained below with reference to the figures. These show:

[0028] Fig. 1: a schematic representation of a DC-DC converter device with a control device according to an embodiment;

[0029] Fig. 2 is a schematic representation of a DC-DC converter device with a control device according to a further embodiment, and

[0030] Fig. 3: a flowchart underlying a method according to an embodiment.

[0031] In the figures, the same reference symbols denote identical or functionally identical components, unless otherwise stated.

[0032] Description of embodiments

[0033] Figure 1 shows a schematic block diagram of a DC-DC converter device comprising a control device 1 and a DC-DC converter 2 according to one embodiment. The DC-DC converter 2 converts a DC voltage U_n provided on the input side into an output DC voltage U_out.

[0034] In this case, a controlled variable R can be provided to the DC-DC converter 2, for example in the form of a duty cycle for pulse-width modulated (PWM) control. The basic principle of a DC-DC converter with pulse-width modulated control is assumed to be known and will not be explained in detail. The controlled variable R for the DC-DC converter 2 can be provided, for example, by means of the control device 1. For this purpose, the control device 1 can comprise a voltage regulator 11 and a current regulator 12.

[0035] The voltage regulator 11 generates a first controlled variable RI. To do this, the voltage regulator 11 compares a value of the output DC voltage U_out with a predetermined setpoint U_setpoint. This setpoint U_setpoint can, for example, be a value for the target voltage to which the intermediate circuit capacitor 4 is to be charged. In addition to the actual voltage regulator 11a, the voltage regulator 11 can also comprise a further pre-regulator 11b. This pre-regulator 11b can, for example, determine a control component based on the input DC voltage U Jn, the setpoint voltage U_setpoint, and optionally also based on electrical currents at the input and / or output of the DC-DC converter 2. This control component can, as shown in Figure 1, be combined with the control component of the actual voltage regulator 11a to obtain the first controlled variable RI.

[0036] The current controller 12 generates a second controlled variable R2, which is determined, for example, based on the electrical current in the DC-DC converter 2. Both the primary-side current l_p at the input of the DC-DC converter 2 and the secondary-side current l_s at the output of the DC-DC converter 2 can be considered for current control. For such current control, two separate control devices 12a and 12b are provided in the current controller 12.

[0037] A first control device 12a can determine a first current control variable R_i_l. This first current control variable R_i_l is determined based on the primary-side current l_p at the DC-DC converter 2. For example, this first current control variable R_i_l can be used to limit an electrical current at the input of the DC-DC converter 2 to a predetermined maximum value. This limiting value can be adjusted, if necessary, taking into account other parameters, such as the temperature in or at the DC-DC converter 2. A second control device 12b can also determine a second current control variable R_i_2. This second current control variable R_i_2 is determined based on the secondary-side current l_s at the output of the DC-DC converter 2.For example, this second current control variable R_i_2 can be used to limit an electrical current at the output of DC-DC converter 2 to a specified maximum value. This limiting value can also be adjusted, if necessary, taking into account other parameters, such as the temperature at DC-DC converter 2.

[0038] The current controller 12 can then determine the second controlled variable R2 from the determined current controlled variables R_i_l and R_i_2. For example, the second controlled variable R2 can be formed from the minimum of the first current controlled variable R_i_l and the second current controlled variable R_i_2. This ensures that the electrical currents in the DC-DC converter 2 do not exceed the limits set by the current controlled variables R_i_l and R_i_2.

[0039] If the current regulator 2 limits the electrical current in the DC-DC converter 2, this can be signaled to the current regulator 11 by a corresponding signal C_1 from the first control device 12a and a signal C_2 from the second control device 12b. In this case, the control of the current regulator 11 can be adjusted or deactivated as appropriate. This ensures that the control of the current regulator 11 does not counteract the current control of the current regulator 12.

[0040] The first controlled variable RI from the voltage regulator 11 and the second controlled variable R2 from the current regulator 12 can be combined with each other, for example added, and the result can be provided as controlled variable R to the DC-DC converter 2.

[0041] DC-DC converter 2 can, for example, be a so-called flyback DC-DC converter. Since the basic design of such DC-DC converters, especially flyback DC-DC converters, is known, it will not be discussed in detail here.

[0042] Furthermore, it is also possible to arrange several DC-DC converters 2 in parallel in the DC-DC converter arrangement. In such a case, a separate current regulator 12 can be provided for each of the DC-DC converters 2, as described above. Furthermore, a common current regulator 11 can be provided for the entire DC-DC converter arrangement.

[0043] Figure 2 shows a schematic block diagram of a DC-DC converter device with a control device 1 and a DC-DC converter 2 according to another embodiment. The above statements regarding the DC-DC converter device, as already described in connection with Figure 1, also apply in principle, where appropriate.

[0044] The DC-DC converter device according to Figure 2 differs from the previously described DC-DC converter device in particular in that, in the first control device 12a, the primary-side current l_p is first compared with a predetermined setpoint l_p_soll. For this purpose, for example, a difference between the primary-side current l_p and the predetermined setpoint l_p_soll can be calculated. If necessary, the result of this comparison can be further weighted with a weighting factor gl. The first control device 12a can provide the first current control variable R_i_l as an output value.

[0045] Analogously, in the second control device 12b, the secondary-side current l_s can be compared with a predefined setpoint l_s_soll. For this purpose, a difference can also be formed between the secondary-side current l_s and the corresponding predefined setpoint l_s_soll.

[0046] If necessary, the result of this comparison can also be weighted with a weighting factor g2. The second control device 12b can provide the second current control variable R_i_2 as an output value. One of the two current control variables R_i_l or R_i_2 can then be selected from the first current control variable R_i_l and the second current control variable R_i_2. For example, the smaller of the two, R_i_l or R_i_2, can be selected and provided to the common controller logic 12c. The controller logic then determines the second control variable R2. This second control variable R2 can be combined with the first control variable RI, as already described in connection with Figure 1.

[0047] Figure 3 shows a flowchart underlying a method for operating a DC-DC converter device according to one embodiment. The method can, in principle, comprise any steps as previously described in connection with the DC-DC converter devices according to Figures 1 and 2. Similarly, the DC-DC converter device described above can also comprise any suitable components as required to implement the method described below.

[0048] In a first step S1, a first controlled variable RI is determined. This first controlled variable R2 can be determined using a setpoint U_setpoint for the output voltage of DC-DC converter 2 and a measured value U_out for the output voltage of DC-DC converter 2.

[0049] In step S2, a first current control variable R_i_l is determined using an electrical current l_p at the input of the DC-DC converter 2.

[0050] In step S3, a second current control variable R_i_2 is determined using an electrical current l_s at the output of the DC-DC converter 2.

[0051] Subsequently, in step S4, a second controlled variable R2 is determined for the DC-DC converter 2 using the first current controlled variable R_i_l and the second current controlled variable R_i_2. Finally, in step S5, the DC-DC converter 2 can be controlled using a combination of the first controlled variable R1 and the second controlled variable R2.

[0052] In summary, the present invention relates to a DC-DC converter arrangement with at least one DC-DC converter, wherein the DC-DC converter has a current and a voltage control. For the current control, a first component is provided for a control based on the primary-side current at the

[0053] DC-DC converter, and a second component for control based on the secondary side current at the DC-DC converter.

Claims

Claims 1. DC-DC converter device, comprising: a DC-DC converter (2) designed to convert an input DC voltage into an output DC voltage; and a control device (1) comprising: a voltage regulator (11) designed to determine a first control variable (RI) for the DC-DC converter (2) using a setpoint (U_setpoint) for the output voltage of the DC-DC converter (2) and a measured value (U_out) for the output voltage of the DC-DC converter (2), and a current regulator (12) designed to determine a second control variable (R2) for the DC-DC converter (2);wherein the current controller (12) comprises a first control device (12a) and a second control device (12b), wherein the first control device (12a) is designed to determine a first current control variable (R_i_l) using an electric current (l_p) at the input of the DC-DC converter (2), the second control device (12b) is designed to determine a second current control variable (R_i_2) using an electric current (l_s) at the output of the DC-DC converter (2), and wherein the current controller (12) is designed to determine the second control variable (R2) using the first current control variable (R_i_l) and the second current control variable (R_i_2); and; wherein the control device (1) is designed to control the DC voltage converter (2) using a combination (R) of the first controlled variable (RI) and the second controlled variable (R2).

2. DC voltage converter device according to claim 1, wherein the current controller (12) is designed to select as the second controlled variable (R2) the smaller value of the first current controlled variable (R_i_l) and the second current controlled variable (R_i_2).

3. DC-DC converter device according to claim 1 or 2, wherein the first control device (12a) and the second control device (12b) of the current controller (12) are each configured to output a control signal (Cl, C2) if the corresponding control device (12a, 12b) is active in an operating mode in which a maximum current in the DC-DC converter (2) is limited, and wherein the voltage controller (11) is configured to adjust the first controlled variable (RI) using the control signal (Cl, C2) from the current controller (12).

4. DC-DC converter device according to claim 1, wherein the first control device (12a) is designed to determine the first current control variable (R_i_l) by comparing the electric current (l_p) at the input of the DC-DC converter (2) with a predetermined setpoint (l_p_setpoint) for the electric current at the input of the DC-DC converter (2), the second control device (12b) is designed to determine the second current control variable (R_i_2) by comparing the electric current (l_s) at the output of the DC-DC converter (2) with a predetermined setpoint (l_s_setpoint) for the electric current at the output of the DC-DC converter (2), and where current controller (12) is designed to determine the second controlled variable (R2) using the minimum of the first current controlled variable (R_i_l) and the second current controlled variable (R_i_2).

5. DC-DC converter device according to any one of claims 1 to 4, wherein the DC-DC converter device comprises several DC-DC converters (2), wherein a separate current regulator (12) is provided for each DC-DC converter (2) of the DC-DC converter device, and wherein a common voltage regulator (11) is provided for all DC-DC converters (2) of the DC-DC converter device.

6. DC voltage converter device according to any one of claims 1 to 5, wherein the DC voltage converter (2) comprises a flyback DC voltage converter.

7. DC voltage converter device according to one of claims 1 to 6, wherein the control device (1) is designed to output a duty cycle for pulse width modulation as a control variable (R) for controlling the DC voltage converter (2).

8. Method for operating a DC-DC converter device with at least one DC-DC converter (2), comprising the steps: Determining (Sl) a first controlled variable (RI) using a setpoint (U_setpoint) for the output voltage of the DC-DC converter (2) and a measured value (U_out) for the output voltage of the DC-DC converter; Determining (S2) a first current control variable (R_i_l) using an electric current (l_p) at the input of the DC-DC converter (2); Determine (S3) a second current control variable (R_i_2) using an electric current (l_s) at the output of the DC-DC converter (2); Determine (S4) a second control variable (R_2) for the DC-DC converter (2) using the first current control variable (R_i_l) and the second Current control variable (R_i_2) ; and Control (S5) of the at least one DC voltage converter (2) using a combination (R) of the first controlled variable (RI) and the second controlled variable (R2).

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