Patent ID: 6069805
Filing Date: 2000-05-30
Classification: H02M

Abstract:
A power supply start-up circuit comprising:a pulse width modulator controller with a voltage reference terminal;a first capacitor, C1, coupled by a first switch means, S1, to said power source;at least two resistors, R1 and R2, coupled in series to form a resistive divider from said first capacitor, C1, to ground;a second capacitor, C2, coupled to the interconnection of said resistors, R1 and R2;a second switch means, S2, coupled in series between said first capacitor, C1, and said second capacitor, C2;a power conversion transformer with an auxiliary winding coupled to said first capacitor, C1;a first zener diode, DZ1, coupled in series between S1 and said power source, with anode towards S1 and cathode towards said power source;a second zener diode, DZ2, coupled in series between S1 and C1, with anode towards S1 and cathode towards C1;a first diode, D1, coupled in series between said auxiliary winding and C1, with anode towards said auxiliary winding and cathode towards C1;a second diode, D2, coupled in series between S2 and C2, with anode towards S2 and cathode towards C2; anda third diode, D3, coupled in series between the interconnection of R1 and R2 and C2, with anode towards R1 and R2 and cathode towards C2;wherein when S1 is closed with S2 open, C1 and C2 charge, when C2 charges to a predetermined voltage, C2 supplies power to the pulse width modulator controller; andfurther wherein when S1 is open with S3 closed, C1 supplies power to the pulse width modulator controller.