DC/DC converter

Due to the considerably more frequent occurrence of starting operations, the electrical load that occurs often leads to voltage dips in the vehicle electrical system. To stabilize the supply voltage for certain voltage-sensitive electrical components and protect them, a DC/DC converter is used together with the automatic engine start-stop. The DC/DC converter supplies the terminal 30 relay with constant voltage, also during the starting operation.

The graphic below shows the DC/DC converter using the example of E90.

Fig 1: DC/DC Converter And Plug Connection

Courtesy of BMW OF NORTH AMERICA, INC.

The DC/DC converter needs the following signals:

• Terminal 50
• Terminal 15
• Terminal 30 (possibly model-specific variants).

The DC/DC converter transmits the following encoded information for the diagnosis (pulse-width modulated signal):

• DC/DC converter OK
• DC/DC converter faulty
• DC/DC converter overheated.