US 4,894,648 AGranted

Information handling and control systems, and methods of testing the condition of electrical loads in such systems

AssigneeSalplex Limited

InventorKevin T. Talbot

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Abstract

In a multiplex system for automotive vehicles, battery (+V) current is supplied to each load (70, 71) connected to a non-intelligent slave unit (20) via a power switch (TR) in the slave controlled by a capacitor (CT) which is charged or discharged in an assigned time slot by high or low voltage (A,C) applied on a low current signal line from a remote intelligent unit (10). If a load (70, 71) goes open-circuit then a voltage source (TR1, Z1) in the slave provides low current via a resistor (R2, R3) and the forward direction of a zener diode Z to charge the capacitor CT to an intermediate voltage which is detected at the remote intelligent unit (10) during an assigned load driving time slot. If a load (70, 71) goes short circuit then a thyristor (TH) in thermal contact with its power switch (TR) turns on to turn off the power switch (TR) and provide a discharge path for the capacitor (CT) via the load (70, 71), this discharged condition being detected at the remote intelligent unit during an assigned load driving time slot. This dedicated extra channels (time slots) are not required at the slave unit for open-circuit or short-circuit load testing.

Claims25

Dependent claims

An information handling and control system comprising:

(a) at least one power switch provided in a local unit to control a high current each to a respective load;
(b) a low current signalling link provided between the local unit and a remote intelligent unit;
(c) at least one capacitor provided in the local unit each connected to the control electrode of a respective said power switch;
(d) means provided in the local unit for connecting each capacitor to the signalling link during a respective time slot assigned to the respective power switch in successive frame periods;
(e) drive voltage means provided in the intelligent unit for applying a first or a second drive voltage within a said respective assigned time slot respectively to charge or discharge said respective capacitor to a high or a low voltage value sufficient respectively to turn the respective power switch on or off, the respective capacitor maintaining the respective power switch continuously on or continuously off between successive frame periods when the respective load is in normal condition;
(f) charging means provided in the local unit effective to charge each said capacitor to an intermediate voltage value only when the respective load is in open-circuit condition following the respective capacitor being discharged to said low voltage value by said second drive voltage and while no drive voltage is applied to the respective capacitor from the drive voltage means;
and
(g) detection means provided in the intelligent unit which are operable to detect the condition of each said capacitor at a time in a selected said respective assigned time slot when the respective capacitor will be at said intermediate voltage value if the respective load is in open-circuit condition and hence to detect whether or not the respective load is in open-circuit condition.

5 more elements

Dependencies are inferred from the claim text.