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# Obtaining Multiple Outputs From a Buck Converter

IP.com Disclosure Number: IPCOM000048835D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 44K

IBM

## Related People

Conner, DE: AUTHOR [+2]

## Abstract

This article describes a modified buck converter circuit capable of producing multiple voltages of either polarity. A secondary winding is added to the inductor in the basic buck converter circuit to provide a second voltage.

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Obtaining Multiple Outputs From a Buck Converter

This article describes a modified buck converter circuit capable of producing multiple voltages of either polarity. A secondary winding is added to the inductor in the basic buck converter circuit to provide a second voltage.

A buck converter is a preferred DC-to-DC converter because of its simple topology and good performance. Conventional buck converters are capable of producing a single voltage only. Considerably more complex circuits have been used whenever multiple voltages had to be generated from a single source.

The drawings illustrate two embodiments of a buck converter circuit which is capable of producing two output voltages with only minimal modification of the basic buck converter circuit.

Referring to Fig. 1, a winding is added to the inductor L1 to produce voltage V(2). Only a small fraction of the total output power need normally be handled by the additional winding. The polarity of this winding is such that diode D2 conducts only when transistor Q1 is off and diode D1 is conducting. During this time the following equations apply: V(1) equals V(01) plus V(D1 FWD)

V(2) equals V(02) plus V(D2 FWD)

V(2) equals N2 divided by N1 V(1)

The polarity of V(02) can be made either positive or negative since the additional winding is floating. For the case where N1=N2: V(02) equals V(01) plus (V(D1 FWD minus V(D2 FWD)) If the two forward diode drops are made equal, V(02) and V(01) will be equal. Since V(01) is r...