Patent ID: 7974109

Claim:
A switch-mode power supply control system for regulating an output voltage at the output of a delivery cable of a power supply over multiple switching cycles said power supply having a primary side and a secondary side that includes said delivery cable, the system comprising: a transformer having a primary magnetizing inductance that electrically separates said primary and secondary sides; a sense voltage unit having a winding on the primary side, to generate a sense voltage on the primary side that is proportional to an output voltage signal on the secondary side; a cable offset voltage unit positioned on the primary side, for determining an offset voltage signal representing a drop in voltage caused by load current passing through the delivery cable positioned on the secondary side; and a feedback unit, for generating a digital feedback voltage signal on the primary side that is used to maintain a substantially constant voltage at the output of the delivery cable over multiple switching cycles, said digital feedback voltage signal determined based upon at least said sense voltage signal, said offset voltage signal and a reference voltage signal representing a target voltage for the voltage regulation wherein the feedback unit generates a control voltage; and wherein the cable offset voltage unit determines the offset voltage signal, the cable offset voltage unit including: a current converter that receives the control voltage and converts the control voltage to an offset current signal using an offset process; an offset voltage generator that receives the offset current, for converting the offset current signal to the offset voltage signal using a scaling factor based on the value of the resistance of the output cable.