Overcurrent detecting method and apparatus
AssigneeKabushiki Kaisha Toyoda Jidoshokki Seisakusho
InventorToshikazu Kamiya
Life of this patent
Estimating the term…
Abstract
In order to detect with high accuracy a current which may adversely affect an electric circuit if continued for an extended time, an apparatus periodically samples an output of a current sensor connected to the circuit and includes a memory storing data of current values regarded as representing overcurrents in consideration of the respective durations thereof. The current values are stored in pairs with time values representing the durations. The sampled value is compared with the current values stored in the memory while duration of the sampled value is compared with the time value paired with that current value.
Claims9
A method of detecting occurrence of an overcurrent state in an electric circuit, comprising the steps of:
- providing an overcurrent detection memory having an area therein capable of being defined along a time axis and a current axis, said area storing sets of data representing combinations of current values regarded as indicating overcurrent states in view of durations thereof and time values representing said durations;
- periodically sampling an output of a current sensor adapted to detect the current flowing through said electric circuit at a selected time interval shorter than the duration represented by the time value paired with the maximum one of said current values stored in said memory area;
- comparing the sampled value of said sensor output sequentially with said current values stored in said memory in descending order of magnitude, starting from the maximum one of said current values;
- reading out from said memory the time value paired with the maximum one of the current values which are smaller than said sampled value;
- and
- comparing the time value read out from said memory with the sum of said selected time intervals during which said sampled value has remained substantially constant, to thereby determine that said sampled value represents an overcurrent state, when said sum of said selected time intervals is equal to or greater than the duration represented by said read out time value.
An apparatus for detecting occurrence of an overcurrent state in an electric circuit, comprising:
- an overcurrent detection memory having an area therein capable of being defined along a time axis and a current axis, said area storing sets of data representing combinations of current values regarded as indicating overcurrents in view of durations thereof and time values representing said durations;
- means for sampling an output of a current sensor adapted to periodically detect the current flowing through said electric circuit at a selected time interval shorter than the duration represented by the time value paired with the maximum one of said current values stored in said memory area;
- means for comparing the sampled value of said sensor output sequentially with said current values stored in said memory in descending order of magnitude, starting from the maximum one of said current values;
- means for reading out from said memory the time value paired with the maximum one of said current values which are smaller than said sampled value;
- and
- means for comparing the time value read out from said memory with the sum of said selected time intervals during which said sampled value has remained substantially constant, thereby determining that said sampled value represents an overcurrent state, when said sum of said selected time intervals is equal to or greater than the duration represented by said read out time value.
Dependencies are inferred from the claim text.