DC-DC converter and method for controlling a DC-DC converter

A method (30) for controlling a DC-DC converter (10;

• 20) comprising the following steps:
• determining a variable first sub-voltage (j·UinV) based on the input DC voltage (Ui);
• determining a constant second sub-voltage (k·UinK)
• converting (31) the first variable sub-voltage (j·UinV) of an input DC voltage (Ui) into an output DC voltage using a first converter device (1);
• converting (32) the second constant sub-voltage (k·UinK) of the input DC voltage (Ui) into an output DC voltage using a second converter device (2);
• operating (33) the first converter device (1) with the first variable sub-voltage (j·UinV);
• and
• operating (34) the second converter device (2) with the second constant sub-voltage (k·UinK);
• wherein the first and second converter devices (1 and 2) are connected in series and the input DC voltage (Ui) is applied across the series connected first and second converter devices (1 and 2);
• wherein a control device (9) is directly connected to the first converter device (1) by a first connection and directly connected to the second converter device (2) by a second connection, the control device (9) is configured to determine the variable first sub-voltage (j·UinV) as equal to the input DC voltage (Ui) minus the constant second sub-voltage (k·UinK), and to control the operation of the first converter device (1) via the first connection to use the variable first sub-voltage (j·UinV) and to control the operation of the second converter device (2) via the second connection to use the constant second sub-voltage (k·UinK).