Patent ID: 7609535

Claim:
A power supply circuit comprising: an input terminal to be directly coupled to an AC source having a distributed source capacitance; an EMI filter coupled to the input terminal, wherein the EMI filter consists of an inductor and a capacitor, wherein a first terminal of the inductor is coupled to the input terminal such that a current flow through the inductor is substantially equal to a current flow through the input terminal, and wherein a second terminal of the inductor is coupled to the capacitor, wherein the EMI filter forms a pi filter with the distributed source capacitance of the AC source when the input terminal is coupled to the AC source such that a current flowing through the AC source is substantially equal to the current flow through the input terminal, and wherein the inductor is an input fuse that becomes an open circuit to limit an abnormal amount of current to all other components of the power supply circuit; and a power conversion circuit coupled to the EMI filter, wherein the capacitor is coupled between the inductor and the power conversion circuit to provide bulk storage for a direct current (DC) input of the power conversion circuit.