Patent ID: 9093910
Filing Date: 2015-07-28
Classification: H02M

Abstract:
1. A system comprising: a switch connected to an input voltage via a primary winding of a transformer; a pulse width modulator that generates a control signal including pulse width modulated pulses having a first frequency and a first duty cycle, that controls the switch based on the control signal, and that regulates an output voltage across a secondary winding of the transformer by turning the switch on and off at the first frequency, wherein the output voltage is supplied to a load connected across the secondary winding through a component connected in series with the secondary winding; a voltage sensing circuit that senses a first voltage across the primary winding during a demagnetization period represented by an off-time of the switch, wherein the first voltage represents the output voltage across the secondary winding; a pulse generator that generates a single pulse at a sampling time during each cycle of the control signal, wherein the sampling time during a first cycle of the control signal is determined based on the input voltage, a voltage drop across the switch, an on-time of the switch, and a value of the first voltage sensed during the first cycle of the control signal; a sampling circuit that samples the first voltage based on the single pulse at the sampling time during the first cycle of the control signal, wherein a sampled value of the first voltage reflects the output voltage with minimized voltage drops across the component and parasitic elements of the secondary winding during the first cycle of the control signal; and an error amplifier that compares the sampled value of the first voltage to a reference voltage and that outputs an error signal to the pulse width modulator during the first cycle of the control signal, wherein the pulse width modulator controls the first duty cycle of the control signal during the first cycle of the control signal based on the error signal generated by the error amplifier.