Switching circuit for redundant automation system - has two switches operated by drive stage according to voltage drops across switches

摘要

The circuit receives a supply voltage at its input ports (E1,E2) which it switches to output ports (A1,A2) via a switching arrangement contg. two switches (T1,T2) subjected to a control voltage. A drive stage (R4,R5,K2;R5,R9,K1) detects the polarity of the voltage drop at the first switch and opens or closes the second switch accordingly. The drive stage also opens and closes the first switch according to the voltage drop across the second switch. Both switches are FETs. They can be temp. protected FETs connected in series so that their source or drain electrodes have a common junction. ADVANTAGE - Reliably transfers input voltage to its output ports and reliably prevents voltage at output ports from reaching input ports.