Method and device for the plausibility check of safety-relevant variables

1. A method for raising plausibility of interdependent safety-relevant electrical variables of an electrical DC-DC converter, the safety-relevant variables being selected from the group consisting of DC current and DC voltage from a high voltage side and a low voltage side of the electrical converter, the method comprising:

providing a first safety-relevant variable and at least one further safety-relevant variable measured on the electrical DC-DC converter to an input of a data processing unit controlling the electrical DC-DC converter and are each and configured to raise the first safety-relevant variable and at least one further safety-relevant variable from a lower safety-level to a higher safety level;

performing with the data processing unit a first plausibility check of the first safety-relevant variable in a first time interval of a cycle of a clock by implementing a first plausibility rule, wherein the first safety-relevant variable is raised from the lower safety level to the higher safety level for the first safety-relevant variable upon a successful first plausibility check during the first time interval of the cycle of the clock;

performing with the data processing unit a second plausibility check of the further safety-relevant variable in a second time interval of a cycle of a clock by implementing a further plausibility rule, wherein the further safety-relevant variable is raised from the lower safety level to the higher safety level for the further safety-relevant variable upon a successful second plausibility check during the second time interval of the cycle of the clock; and

with the data processing unit controlling electrical variables of the electrical DC-DC converter commensurate with the safety-relevant variable and the further safety-relevant variable being raised from the lower safety level to the higher safety level.

2. The method of claim 1 , wherein the plausibility rules each have a calculation function configured to perform the plausibility checks of the safety-relevant variables at the higher safety level.

3. The method of claim 2 , wherein in addition to the safety-relevant variables, at least one additional calculation variable is included in the calculation function of the plausibility rules.

4. The method of claim 1 , wherein a cycle duration of the cycle of the clock, within which the plausibility checks of the first safety-relevant variable and the further safety-relevant variable and the raising from the lower safety level to the higher safety level is performed, does not exceed a latency time for a safety event to be monitored, wherein the latency time is that time required to monitor an exceeding of the variable.

5. The method of claim 4 , wherein the first time interval of the cycle of the clock and the second time interval of the cycle of the clock have a same duration.

6. The method of claim 4 , wherein the first time interval of the cycle of the clock and the second time interval of the cycle of the clock do not have a same duration.

7. The method of claim 1 , wherein the first plausibility rule and/or the further plausibility rule includes a comparison operation for determining success of the plausibility check, configured to compare the safety-relevant variables, which are to be raised from the lower safety level to the higher safety level, with the safety-relevant variables which are provided but not yet plausibility checked by the plausibility rules.

8. The method of claim 1 , wherein the method is repeatedly performed by repeating the clock cycle.

9. A data processing unit controlling an electrical DC-DC converter, comprising:

a first input for receiving a first safety-relevant variable measured on the DC-DC converter;

at least one further input for receiving at least one further safety-relevant variable, the first safety-relevant variable and the further safety-relevant variable being selected from the group consisting of DC current and DC voltage from a high voltage side and a low voltage side of an electric converter, wherein the first safety-relevant variable and the further safety-relevant variable are dependent on one another;

at least one additional input for receiving at least one additional calculation variable;

a first output for outputting the first safety-relevant variable, said first output being plausibility checked with a first plausibility rule during a first part of a clock cycle and raised to a higher safety level when a deviation between the first safety-relevant variable and the plausibility-raised first safety-relevant variable is acceptable within previously defined tolerances; and

at least one further output for outputting the further safety-relevant variable, said at least one further output being plausibility checked with a second plausibility rule during a second part of a clock cycle and raised to the higher safety level when the deviation between the further safety-relevant variable and the plausibility-raised further safety-relevant variable is acceptable within previously defined tolerances,

said data processing unit configured to control electrical variables of the electrical DC-DC converter commensurate with the safety-relevant variable and the further safety-relevant variable being raised from the lower safety level to the higher safety level.

10. An electrical DC-DC converter for an electric or hybrid vehicle, said electrical DC-DC converter comprising a a data processing unit which controls the electrical DC-DC converter and includes a first input for receiving a first safety-relevant variable, at least one further input for receiving at least one further safety-relevant variable, the first safety-relevant variable and the further safety-relevant variable being selected from the group consisting of DC current and DC voltage from a high voltage side and a low voltage side of an electric converter, wherein the first safety-relevant variable and the further safety-relevant variable are dependent on one another, at least one additional input for receiving at least one additional calculation variable, a first output for outputting the first safety-relevant variable, said first output being plausibility checked with a first plausibility rule during a first part of a clock cycle and raised to a higher safety level when a deviation between the first safety-relevant variable and the plausibility-raised first safety-relevant variable is acceptable within previously defined tolerances; and

at least one further output for outputting the further safety-relevant variable, said at least one further output being plausibility checked with a second plausibility rule during a second part of a clock cycle and raised to the higher safety level when the deviation between the further safety-relevant variable and the plausibility-raised further safety-relevant variable is acceptable within previously defined tolerances,

said electrical DC-DC converter configured to convert high-voltage DC current to low-voltage DC current commensurate with the safety-relevant variable and the further safety-relevant variable received from the data processing unit that have been raised from the lower safety level to the higher safety level.

11. The electrical converter of claim 10 , wherein the electrical converter comprises a traction converter for operating an electrical machine.