Low cost redundant AC to DC power supply

Details Low cost redundant AC to DC power supply Low cost redundant AC to DC power supply

2001-10-29

2003-10-07

Sterrett, Jeffrey (Department: 2836)

Electrical transmission or interconnection systems

Plural supply circuits or sources

Substitute or emergency source

C307S080000, C307S086000, C363S070000

Reexamination Certificate

active

06630753

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to power supplies, and more particularly to redundancy in power supplies.
BACKGROUND OF THE INVENTION
Redundant AC to DC power supplies are well known in the art.
FIG. 1
illustrates a first conventional circuit for providing redundant AC to DC power. The circuit
100
comprises a first AC voltage source
102
coupled to a first power supply
106
in a first power train. The circuit
100
also comprises a second AC voltage source
104
coupled to a second power supply
108
in a second power train. The DC voltages from the first
106
and second
108
power supplies are combined and provided as DC outputs. However, this conventional circuit requires two independent power supplies
106
and
108
connected to two separate AC sources. This adds to the cost of the power system.
FIG. 2
illustrates a second conventional redundant AC power system. The system
200
comprises a first AC voltage source
202
and a second AC voltage source
204
. Both sources provide AC voltages to an AC transfer switch
206
. The transfer switch
206
supplies either the voltage from the first AC voltage source
202
or the voltage from the second AC voltage source
204
to a power supply
208
, which provides DC outputs. However, the transfer switch
206
is very expensive, adding significant cost to the circuit
200
.
Accordingly, there exists a need for a low cost redundant AC to DC power supply. This power supply should provide AC power redundancy in a cost effective manner. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The power supply in accordance with the present invention provides AC redundancy while also preventing voltages from multiple AC voltage sources from adding at a common node. The adding of voltages is avoided by ensuring that only one AC voltage source at a time is providing the voltage at the output. Even if the other AC voltage sources are connected afterwards, these later AC voltage source are prevented from providing power at the output. In addition, diodes prevent current from back flowing to the AC voltage sources which are not supplying power to the output. Because the power supply in accordance with the present invention neither uses redundant AC to DC power supplies from independent AC voltage sources, nor does it use a costly transfer switch, the power supply in accordance with the present invention is more cost effective than conventional redundant power supplies.


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