| 摘要 |
PURPOSE:To enable the trigger with phase angles 90 deg.-180 deg. of the input voltage for the thyristor trigger circuit by giving no trigger at the passing time of the turn-on voltage at the positive rise of the sine wave but giving the trigger at the time point of the trailing for the first time. CONSTITUTION:Anode A of P-gate type thyristor TH, gate GF of P-channel type FET and one terminal of resistance R are connected in common to the power source. When voltage VC of capacitor C becomes identical to the sum of Zener voltage VZ of Zener diode DZ, source-drain voltage VSD of FET and forward voltage VGK between the gate and the cathode of TH respectively, gate current IG is set smaller than the minimum turn-on current. Thus, no trigger is secured at the time of positive rise. When the voltage phase exceeds 90 deg., the pinch-off of the FET is released to increase IG sufficiently and thus to secure the trigger. |
