This report describes a universal input, 5 V, 1.6 A flyback power supply using a LinkZero-LP family of ICs. It contains the complete specification of the power supply, a detailed circuit diagram, the entire bill of materials required to build the supply, extensive documentation of the power transformer along with test data and oscillographs of important electrical waveforms.
The LinkZero-LP device integrates an oscillator, an ON/OFF controller, start-up and protection circuitry and a power MOSFET all on one monolithic IC. One side of the power transformer primary is connected to the positive leg of C1 and the other side is connected to the DRAIN (D) pin of U5. At the start of a switching cycle, the controller turns the MOSFET ON, and current ramps up in the primary winding, which stores energy in the core of the transformer. When that current reaches the limit threshold, the controller turns the MOSFET OFF. Due to the phasing of the transformer windings and the orientation of the output diode, the stored energy then induces a voltage across the secondary winding, which forward biases the output diode, and the stored energy is delivered to the output capacitor.