High efficiency multiple input voltage sources power supply

Details High efficiency multiple input voltage sources power supply High efficiency multiple input voltage sources power supply

2001-10-31

2003-02-18

Callahan, Timothy P. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Gating

Converging with plural inputs and single output

C327S063000, C307S064000

Reexamination Certificate

active

06522190

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to power supplies, and more particularly to power supplies with multiple input voltage sources.
BACKGROUND OF THE INVENTION
The use of power supplies with multiple input voltage sources, in industries such as the telecommunications industry, is well known in the art. Power supplies with multiple input voltage sources provide redundancy in the system to ensure that power continues to be provided to the system, even when one of the voltage sources fail.
FIG. 1
illustrates a conventional multiple input voltage sources power supply circuit. The circuit
100
comprises a first voltage source
102
coupled in series to a first diode
106
, a second voltage source
104
coupled in series to a second diode
108
. The cathodes of the diodes
106
and
108
are coupled directly to the voltage sources
102
and
104
, respectively, and the anodes of the diodes
106
and
108
are connected to the load
110
, which is generally a DC-DC regulator.
When the first voltage source
102
is “on”, i.e., supplying a voltage, such as −48V, and the second voltage source
104
is “off”, i.e., either supplying less than −48V or not connected, then −48V is supplied to the load
110
by the first voltage source
102
because the second diode
108
is back biased. The second diode
108
prevents current from back flowing to the second voltage source
104
, and thus prevents the second voltage source
104
from becoming a sink and overheating the power supply.
When the first voltage source
102
is “off”, i.e., either supplying a voltage less than −48V or not connected, and the second voltage source
104
is “on”, i.e., supplying −48V, then −48V is supplied to the load
110
by the second voltage source
104
. The first diode
106
prevents current from back flowing to the first voltage source
102
because the first diode
106
is back biased, and thus preventing the first voltage source
102
from becoming a sink. Other voltage sources may be coupled to the load
110
and function in the same manner.
However, the loss of power in each diode
106
and
108
is significant for high powered loads. For example, for voltage sources which supply −48V, the loss per diode
106
or
108
could be as high as 10W for a 1 kW load. The conventional multiple input voltage sources power supply is thus inefficient.
Accordingly, there exists a need for a high efficiency multiple input voltage sources power supply. The power supply should provide higher efficiency than a conventional power supply and at the same time, provide a means for preventing current flow among different voltage sources connected to a common load. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The present invention provides a highly efficient power supply with redundant multiple input voltage sources. The power supply uses switching transistors, specifically MOSFET's, to create paths for current from one of the voltage sources to the load. The switching transistors are switched either “on” or “off” by comparators which compare the output from the voltage sources. These comparators allow the highest voltage source to provide power to the load, and keep the other switching transistors “off” that connect the common load to other voltage sources. Because the switching transistors have lower conduction losses than diodes in conventional power supplies, the power supply in accordance with the present invention is more efficient.


REFERENCES:
patent: 4754160 (1988-06-01), Ely
patent: 4788450 (1988-11-01), Wagner
patent: 5598041 (1997-01-01), Willis
patent: 5608273 (1997-03-01), Barlett
patent: 5811895 (1998-09-01), Suzuki et al.
patent: 5886561 (1999-03-01), Eitan et al.
patent: 6060789 (2000-05-01), Yamaguchi
M. Ferry et al., “Low Voltage Drop, Redundant Power Circuit,” IBM Technical Disclosure Bulletin, vol. 34, No. 1, Jun. 1991, pp. 227-228.

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