Power Distribution Module: Description and Operation

DC/DC Converter (Start Stop)







The DC/DC converter is only installed in vehicles with Start Stop systems. The DC/DC converter is installed in the luggage compartment, underneath the luggage compartment cover and above the battery.







Situation:
- and various components are no longer supplied with the usual 12V voltage. This can result in a system failure.

Solution:
- starts and delivers this missing voltage to the vehicle electrical system.

During Start Stop operation, the Start Stop coordinator (DME) decides to switch off the engine. When the engine is off, the electrical loads are supplied with energy by the vehicle battery reserves. The battery voltage falls many times below the cell open-circuit voltage (2.1V/cell).

When the engine is started, voltage drops occur (when the starter engages and a second voltage drop when the main contacts of the starter are closed and the engine breaks away). Afterwards, the voltage recovers as a function of the starter speed when the starter is switched off and disengages, generator charging then commences and the charging voltage is reached. The size of the voltage drop depends on the temperature of all the relevant components in the current path, internal resistance and the age of the battery as well as the engine resisting torque when it is turned.