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# Circuit for Combining Power From Multiple Sources

IP.com Disclosure Number: IPCOM000100174D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 4 page(s) / 121K

IBM

## Related People

Driscoll, CD: AUTHOR [+2]

## Abstract

Disclosed is a circuit for combining available power from any number of different DC input voltages to produce regulated DC output voltages. The amount of power drawn from each input voltage can be precisely controlled.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Circuit for Combining Power From Multiple Sources

Disclosed is a circuit for combining available power from
any number of different DC input voltages to produce regulated DC
output voltages.  The amount of power drawn from each input voltage
can be precisely controlled.

When a new feature is added to an existing product, the
available DC voltages and currents may not match the needs of the
feature.  Sometimes the required total power is available, but not
from any one voltage level.  In this case a circuit is needed which
can combine the available power from multiple sources and convert it
to the required voltage and current.

Fig. 1 shows the basic circuit for combining power from two
different voltage levels into a single regulated output. The circuit
uses the forward converter topology.  Two separate transformers (T1
and T2) are used, one for each input voltage, V1 and V2.  The
secondary windings of the transformers are placed in series, so that
each winding generates a fraction of the total output voltage, +Vout.
These fractions may be expressed as follows:
(1)  V1S / Vout = 1 -V2S / Vout
(2)  V2S / Vout = 1 - V1S / Vout
where:  V1S and V2S are the secondary winding voltages
Vout is the total output voltage

Both secondary windings carry the same current, so they will
also generate these same fractions of the total output power:
(3)  V1S / Vout = P1 / Pout
(4)  V2S / Vout = P2 / Pout
where:  P1 is the power drawn from input voltage V1
P2 is the power drawn from input voltage V2
Pout is the power delivered by output voltage Vout

The two transformers are independent, so the designer may
choose any combination of secondary voltages which will produce the
desired output voltage.  Since power is proportional to the secondary
voltages, this allows precise control over the power delivered by
each input voltage V1 and V2.  The designer knows the required output
voltage and power (Vout and Pout).  The power available from the
input voltages (P1 and P2) is also known.  Equations 3 and 4 can be
solved for the required secondary voltages (V1S and V2S). These
voltages are realized by proper selection of the transformer turns
...