Power supply unit for use in motor vehicle-electrical system, has switching converter operated as step up converter when input voltage falls below threshold value, and linear voltage controller connected with output voltage of converter

摘要

The unit (1) has a switching converter (2) with an inductor and switches, with which the inductor is alternatively switched against a supply potential (V2) or a reference potential (GND). The converter is operated as a down converter during normal operation and as a step up converter in an operating mode when an input voltage (VB) falls below a threshold value. A linear voltage controller (4) is connected with an output voltage (V1) of the converter, where the voltage (V1) changes into a lower voltage (U3V).