| 摘要 |
PURPOSE:To reliably switch a signal source by generating a preclear signal with a control signal to start a counting operation, and generating a timing control signal with the output of a timer which stops the counting at the prescribed time and the input of a control signal. CONSTITUTION:A control signal A' is inputted to a preclear control circuit 101 which generates a preclear signal C', a counter 102 is cleared to start counting of a clock signal 103, and to stop counting at the time T. The output D' of the counter 102 and the control signal A' are inputted to a timing control circuit 104, which outputs signals E', F'. The signal E' rises with the fall of the initial pulse of the signal D', and falls with the rise of the next pulse of the output D'. The signal F' falls with the rise of the initial pulse of the output D' contrary to the signal E', and rises with the fall of the next pulse of the output D'. Thyristors 13, 14 are driven by the signal E', F' of drive circuits 5, 6. In this manner, the thyristors 13, 14 are prevented from being simultaneously conducted, thereby accurately switching signal sources 15, 16. |
