Proximity switch with power supply independent of switch state - provides stabilised DC voltage for internal components from mains supply and converts to new DC level

摘要

The proximity switch has a power supply (5) supplying its components with a stabilised voltage irrespective of whether it is on or off. The power supply has a series regulating transistor between its inputs (8, 9) and outputs (7, 9). When the input voltage falls, the regulating transistor acts as a constant regulator. When the input voltage increases the regulating transistor (10) acts as a switching regulator. The switching regulator mode is combined with a blocking oscillator mode. The switching regulator inductor is charged and discharged via a series constant regulator.