resumeIn brief
The high-voltage battery and low-voltage users do not necessarily work on one voltage. The DC/DC converter connects these needs.
Useful to know
The DC/DC converter changes a constant voltage to another constant voltage. In the specific example, the Bosch generation 3evo powers the 12-volt on-board network from a high-voltage battery through galvanically isolated conversion. [1]
This is a different task from the inverter to the traction motor. The name "transformer" is general; it must be specified what is being converted and for whom the output is intended.
A practical scheme is a high-voltage battery → DC/DC → low-voltage network. It helps to understand why the presence of a large traction battery does not mean that every sensor and controller operates directly on its voltage.
The specified product is an example of a specific construction, not a proof that all cars have exactly 12 V or the same architecture. For real diagnostics and work on high-voltage components, the exact factory procedures are needed. Here the function is explained, without service instruction.
Sources
For further detail and to check the information: