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Abstract

A transformer for switched mode power supplies and the like comprises an input stage transformer section which is designed for very good coupling and very low primary leakage inductance, without regard for insulation above 'working insulation' or for interwinding capacitance. One or more additional stage transformer sections are optimized for very low interwinding capacitance and very high dielectric isolation. The secondary of the input stage drives the primary of the next stage, so that the transformer stages are in series. Accordingly, the total interwinding capacitance from end to end is very low and the total dielectric isolation from end to end is very high. The secondary of the input stage transformer is isolated from both the input and the output, so it can be grounded as a safety ground. Because the input stage can be designed without regard for capacitance or isolation, it can be smaller, lighter, less expensive and have better thermal and high frequency characteristics, enough so that the transformer as a whole can be smaller, lighter, less expensive and have better thermal and high frequency characteristics than a single stage transformer of comparable rating.

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First Claim