Method and apparatus for providing input EMI filtering in power supplies
AssigneePower Integrations, Inc.
InventorBalu Balakrishnan
Life of this patent
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Abstract
A power supply electromagnetic interference (EMI) filter circuit and technique. In one embodiment, a method of filtering EMI in a power supply includes rectifying an AC signal from an AC source, smoothing the rectified AC signal with a bulk storage capacitor to provide a DC output as an input to a power conversion circuit and filtering the EMI generated by the power conversion circuit from reaching the AC source by using the bulk capacitor and one or more inductors in combination with the AC source capacitance as an EMI filter. In one embodiment the method also includes the use of one or more of the inductors as a fusing element.
Claims16
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.
A power supply circuit, comprising:
- a rectifier circuit;
- and
- a single electromagnetic interference (EMI) filter circuit coupled to the rectifier circuit, the EMI filter circuit consisting of:
- an inductor having a first terminal to be coupled to an alternating current (AC) source having an AC source capacitance;
- and
- a bulk storage capacitor coupled across an output of the rectifier circuit, wherein an EMI pi filter is formed with the AC source capacitance, the inductor, and the bulk storage capacitor when the first terminal of the inductor is coupled to the AC source.
Dependencies are inferred from the claim text.