| 摘要 |
PURPOSE:To perform accurate detection by starting to count a conduction interval under the condition that there is an ignition pulse of a power semiconductor and an electric current is existent, and by ending said counting at the point of time when said current is no longer existent. CONSTITUTION:A power converter 3 is controlled by a processor 1 such as microprocessor via a phase controller 2 to drive a load 4 such as motor. Said electric current is detected by a current detection sensor 5 and read by a data bus 12 via a binary circuit 6, an AND gate 7, a differentiating circuit 8, a flip-flop 9, a counter 10 and a latch circuit 11. Then, a value theta counted by said counter 10 shows a value proportional to a conduction interval of said current and the processor 1 inputs and evaluates the counted value theta latched by the latch circuit 11 via the data bus 12 to perform interruption and compensation of electric current and others. In this case, influences from a mixing noise can be avoided, because the flip-flop 9 is reset by a last transition differential signal Vd of current detection signal Vc.
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