Method for identifying a short-line fault or a line interruption for a switched inductive load
A method identifies a short-line fault or line interruption in a circuit configuration having a series circuit of inductive load and controllable switching element. The series circuit is connected between high and low potentials of a supply voltage source. A connecting point between load and switching element is connected through at least one zener element to the high or low potential of the voltage source or the control connection of the switching element so that upon interruption of current flow through the load due to switching off the switching element, magnetic energy stored in the load can be reduced by a zener element becoming conductive. After switching off the switching element, the voltage at the connecting point is ascertained and a voltage pulse duration is compared with a first prescribed duration. If the duration is shorter than the first prescribed duration, a line interruption or a short is inferred.
1. A method for identifying a short-line fault or a line interruption in a circuit configuration, the method comprising the following steps:
providing a supply voltage source having high and low potentials;
providing a series circuit connected between the high and low potentials of the supply voltage source, the series circuit having an inductive load, a first controllable switching element with a control connection and a second controllable switching element;
providing the inductive load with a first connection connected to the high potential of the supply voltage source through the first switching element and a second connection connected to the low potential of the supply voltage source through the second switching element;
providing a connecting point between the inductive load and the second switching element;
providing at least one zener element connected between the connecting point and the high or low potential of the supply voltage source or the control connection of the first switching element, permitting magnetic energy stored in the inductive load to be reduced by the zener element becoming conductive in the event of an interruption of a flow of current through the inductive load due to the first controllable switching element being switched off;
after the first switching element has been switched off, ascertaining a voltage at the connecting point and comparing a duration of a voltage pulse occurring to a first prescribed duration and, if the duration is shorter than the first prescribed duration, inferring a line interruption or a short, and inferring a line interruption only if no overcurrent condition has occurred; and which further comprises inferring a short through the inductive load if an overcurrent condition has occurred and, after the first or second switching element has been switched off, a duration of a voltage pulse occurring is longer than the second prescribed duration and shorter than a third prescribed duration, which is longer than the second prescribed duration and shorter than the first prescribed duration.
2. The method according to claim 1 , which further comprises inferring a short between the first connection of the inductive load and the high potential of the supply voltage source if an overcurrent condition has occurred and, after the second switching element has been switched off, a duration of a voltage pulse occurring is longer than the first prescribed duration.
3. The method according to claim 1 , which further comprises inferring a short between the second connection of the inductive load and the high potential of the supply voltage source if an overcurrent condition has occurred and, after the second switching element has been switched off, a duration of a voltage pulse occurring is shorter than a second prescribed duration, which is shorter than the first prescribed duration.