Electrical transmission or interconnection systems – Plural load circuit systems – Common conductor or return type
Reexamination Certificate
2001-11-27
2004-01-13
Toatley, Jr., Gregory J. (Department: 2836)
Electrical transmission or interconnection systems
Plural load circuit systems
Common conductor or return type
C307S043000
Reexamination Certificate
active
06677686
ABSTRACT:
BRIEF DESCRIPTION OF THE INVENTION
This invention relates generally to power supplies used in electronic systems. More particularly, this invention relates to a redundant power supply system with improved reference voltage sampling during low loads.
BACKGROUND OF THE INVENTION
FIG. 1
illustrates an electronic system
20
with redundant power supplies. The system
20
includes a first power supply
22
and a second power supply
24
connected to a common power bus
25
that supplies power to a variable load
26
. By way of example, the electronic system
20
may be a motherboard with a set of slots that form the variable load
26
.
The first power supply
22
has a first power supply output node
28
connected to the common power bus
25
via a first power line
30
. A first power line diode
32
is positioned on the first power line
30
. The first power line diode
32
operates as an isolating diode so that the first power supply does not fight the second power supply
24
.
The first power supply
22
also has a first sense line node
36
connected to the common power bus
25
via a first sense line
38
. The first sense line
38
includes a first sense line diode
40
to create an isolated sense line.
The second power supply
24
has an identical configuration, including a second power supply output node
50
connected to the common power bus
25
via a second power line
52
. A second power line diode
54
is positioned on the second power line
52
. In addition, the second power supply
24
has a second sense line node
56
connected to the common power bus
25
via a second sense line
58
. A second sense line diode
60
is connected to the second sense line
58
.
The problems associated with the prior art electronic system
20
will be discussed in connection with the first power supply
22
with the understanding that the second power supply
22
has the same problems. When the first power supply
22
generates an output voltage at the first power supply output node
28
, the output voltage experience a small voltage drop as a result of the first power line diode
32
. The first sense line
38
has a high impedance. Therefore, at low loads the first sense line
38
does not draw any current. As a result, the first sense line diode
40
does not operate in its linear region, meaning that it does not measure small variations in voltage at low loads. This results in inaccurate output voltages from the first power supply
22
. In addition, the output voltages are unstable since they are not accurately responding to the actual conditions within the electronic system
20
. In order to measure small voltage variations at low loads, it is necessary to have the first sense line diode
40
operate in its linear region so that the sense node
36
of the power supply
22
can measure small voltage variations.
In view of the foregoing, it would be highly desirable to provide improved reference voltage sampling in electronic systems with redundant power supplies serving a small load. Improved reference voltage sampling would facilitate stabile and accurate output voltages at low loads.
SUMMARY OF THE INVENTION
An embodiment of the invention includes an electronic system with a common power bus and a load connected to the common power bus. A first power supply output node and a first sense line node of a first power supply are connected to the common power bus. A second power supply output node and a second sense line node of a second power supply are connected to the common power bus. A sense line load adjustment circuit is linked to the common power bus, the first sense line node, and the second sense line node. The sense line load adjustment circuit is configured to generate a mirror voltage that provides a corrected reference voltage at the first sense line node and the second sense line node in the presence of a relatively small load.
Another embodiment of the invention includes an electronic system with a common power bus and a load connected to the common power bus. A first power supply has a first power supply output node and a first sense line node. A first power line is connected between the first power supply output node and the common power bus. A first power line diode is positioned on the first power line. A first sense line is connected between the first sense line node and the common power bus. A first sense line diode is positioned on the first sense line. A second power supply has a second power supply output node and a second sense line node. A second power line is connected between the second power supply output node and the common power bus. A second power line diode is positioned on the second power line. A second sense line is connected between the second sense line node and the common power bus. A second sense line diode is positioned on the second sense line. A sense line load adjustment circuit is connected to the first sense line and the second sense line. The sense line load adjustment circuit generates a control current to place the first sense line diode and the second sense line diode in a linear region of operation in the presence of a relatively small load.
The invention provides improved reference voltage sampling in electronic systems with redundant power supplies serving low loads. Improved reference voltage sampling stabilizes the output voltages generated by the redundant power supplies. Thus, the redundant power supplies provide more accurate output voltages to isolated sense lines, particularly at low loads. Advantageously, the invention can be implemented using low cost components and simple manufacturing techniques.
REFERENCES:
patent: 4136286 (1979-01-01), O'Halloran et al.
patent: 4533836 (1985-08-01), Carpenter et al.
patent: 4644440 (1987-02-01), Kenny et al.
patent: 5686814 (1997-11-01), Wierzbicki
Allied Telesyn International Corp.
Cooley & Godward LLP
Polk Sharon A.
Toatley , Jr. Gregory J.
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