The invention relates to a time-shared control voltage regulating circuit which can periodically control a power supply. The voltage regulating circuit comprises a periodic and time-shared control execution circuit (1), a control driving circuit (2), an isolation coupling circuit (3), a phase-detecting circuit (4) and a main control circuit (7) and is characterized in that the input of the periodic time-shared control execution circuit (1) is connected with the input terminal of a power supply and a control input terminal is connected with the output of the control driving circuit (2) while the input of the control driving circuit (2) is connected with the periodically and time-shared controlled output terminal of the main control circuit (7) through the isolation coupling circuit (3), theinput terminal of the phase-detecting circuit (4) is connected with the input terminal of the power supply and the output terminal of the phase-detecting circuit (4) is connected with the phase signal detecting terminal of the main control circuit (7); at least two switching tubes each of which independently control the input circuit are arranged in each current direction of the periodic time-shared control execution circuit (1). The voltage regulating circuit can effectively reduce the temperature rising of power switching equipment to drop the temperature of the switching tube during work in the main circuit, and further enhance the reliability of the switching tube and reduce energy consumption and cost.