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Single Ended Converter with Transformer Core Reset by Energy Stored in Filter Inductor

IP.com Disclosure Number: IPCOM000087125D
Original Publication Date: 1976-Dec-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Hart, BE: AUTHOR

Abstract

In a single-ended converter, unidirectional current in the transformer primary has a tendency to "walk" the core into the first quadrant of the B-H curve as shown at 10 (Fig. 1). To counteract this, circuitry can be added to reset the core into the third quadrant. The amount of energy required to drive the transformer core into the third quadrant is small compared with the energy stored in the usual output filter inductor of such a converter. Therefore, this energy can be taken from the inductor without seriously impacting the useful output.

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Single Ended Converter with Transformer Core Reset by Energy Stored in Filter Inductor

In a single-ended converter, unidirectional current in the transformer primary has a tendency to "walk" the core into the first quadrant of the B-H curve as shown at 10 (Fig. 1). To counteract this, circuitry can be added to reset the core into the third quadrant. The amount of energy required to drive the transformer core into the third quadrant is small compared with the energy stored in the usual output filter inductor of such a converter. Therefore, this energy can be taken from the inductor without seriously impacting the useful output.

Fig. 2 shows a typical converter having a DC source 11, a cyclically operated switch 12 (which may be a transistor driven by a suitable pulse-width modulation control, not shown), a transformer T, a rectifier 14, a filter having an inductor 16, a capacitor 18 and a freewheeling diode 20, and an output load 22.

Inductor 16 has a main winding N5 and an auxiliary winding N6. N6 has about ten times as many turns as N5 but conducts about 1/100 as much current; hence, it is quite small.

When switch 12 is closed, the dotted output of T secondary N2 is positive and the current builds up in N5 of filter 16 in the usual fashion. Current also flows in N6, in parallel with N5, through added rectifier diode 24.

When switch 12 opens, the current continues through filter 16. Most of the total ampere turns continue in N5, with the bulk of the current flowi...