Variable input voltage regulator circuit

Claim 1

A power supply comprising: a source of unregulated AC voltage having an amplitude between a first and a second level; means for providing a voltage level representative of the amplitude of said unregulated AC voltage; means responsive to said representative voltage level for producing an output signal when said representative voltage level is above a predetermined level corresponding to an unregulated AC voltage amplitude intermediate said first and second levels; first rectifying means coupled to said unregulated AC voltage source for producing a first DC voltage from said AC voltage; circuit means for forming a second rectifying means for producing a second DC voltage from said AC voltage when said circuit means is coupled to said first rectifying means; switch means responsive to said output signal for coupling said circuit means to said first rectifying means when said unregulated AC voltage level is above said intermediate level comprising: a bidirectional switch coupled to said first rectifying means and to said circuit means; a first transistor coupled to said output signal producing means; and a second transistor, regeneratively coupled to said first transistor and to said bidirectional switch, said first and second transistors cooperating to provide rapid switching of said bidirectional switch; and regulator means responsive to said first or second DC voltage for providing a DC output voltage having a fixed regulated level with respect to variations in the level of said unregulated AC voltage between said first and second levels.