Dc-to-dc regulated converter current foldback power

Claim 1

An improved dc-to-dc converter of the type including an input oscillator, an output rectifier, a transformer coupling said input oscillator and said output rectifier, and a control means coupled between said rectifier output and said oscillator for sampling the rectifier output voltage, comparing said output voltage to a preselected standard voltage, and generating a signal to control the output of said oscillator, and wherein said improvement comprises an oscillator output sampling means including an auxiliary secondary winding incorporated in said coupling transformer, one side of said secondary winding coupled to the positive polarity output of said rectifier, a current foldback means including a voltage divider coupled to the other side of said secondary winding, and across the output of said rectifier, an npn transistor having an emitter coupled to said voltage divider, a base coupled in parallel to said secondary winding and to the negative polarity output of said rectifier, and a collector coupled to said control means, a resistance element coupled in said negative polarity output of said rectifier between said voltage divider and said transistor base, and a first diode having an anode coupled to said transistor base and a cathode coupled to said negative polarity output of said rectifier, and the voltage drop across said resistance element exceeding that between said transistor emitter and said negativE polarity output of said rectifier when said converter is overloaded such that said transistor is biased into conduction to thereby limit the output of said converter.