This paper analyzes the reason that the common thyristor trigger is unable to fulfill power supply in wide range changes of frequency. The high precise frequency/voltage converter is used to monitor and track frequency changes of the simultaneous power supply. The simultaneous signal and charge current source are provided by the converter for saw tooth wave trigger. The frequency of saw tooth wave changes as the same time the frequency of power supply changes in wide range. However, the amplitude of the saw tooth wave can be kept constant. This can achieve the controlled angle of the thyristor trigger does not change with the large-scale voltage frequency changes of the simultaneous power supply when the same Phase-shifted control voltage was used.