| 摘要 |
PURPOSE:To eliminate the unbalance of positive and negative firing angles of a phase control circuit by storing and producing a command signal during a half cycle, thereby generating a firing pulse that the firing angles of the respective thyristors become the same. CONSTITUTION:The outputs of reference signal generator 5 and current detector 6 are compared and calculated by a comparison arithmetic circuit 7 to obtain an output waveform 21. In the gate pulse generator 8, a gate pulse 23 is produced at the crossing point between the sawtooth wave 22 and the waveform 21 to fire an antiparallel thyristor 9, a gate pulse 23 is inputted to a logic circuit 10 to obtain an output waveform 27, and is temporarily inputted to a memory circuit 10. In this manner, a signal is outputted by the initial gate pulse, and a signal stopped by the next gate pulse is outputted every time gate pulses are inputted at every other one. While the output of the logic circuit 10 is produced, a temporary memory circuit 10 holds the output of the initial comparison arithmetic circuit 7 as shown by the output waveform 26, with the result that the positive and negative firing angles always become the same. |
