Electrical transmission or interconnection systems – Plural supply circuits or sources – Load current control
Reexamination Certificate
2000-03-31
2001-03-20
Riley, Shawn (Department: 2838)
Electrical transmission or interconnection systems
Plural supply circuits or sources
Load current control
C307S082000
Reexamination Certificate
active
06204571
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention generally relates to a multiple power supply unit comprising a plurality of DC stabilized power supplies that provides a constant voltage in parallel to a single common load.
More particularly, the present invention relates to a multiple power supply unit comprising a plurality of DC stabilized power supplies, each power supply having improved sensitivity to an overcurrent state of output current to the single common load during operation.
II. Background and Material Information
FIG. 3
is a block diagram depicting the configuration of a conventional DC stabilized power supply unit, namely, a DC/DC converter
300
.
DC/DC converter
300
comprises a DC voltage supply
1
, a switching element
2
, a transformer
3
, diodes
4
,
5
, and
6
, an inductor
7
, an electrolytic capacitor
8
, a sense resistor
9
, and a load
10
. Sense resistor
9
is connected between a negative electrode of transformer
3
and load
10
. An overcurrent detection circuit
11
is connected to both ends of sense resistor
9
. Overcurrent detection circuit
11
comprises an amplification circuit
12
, a resistor
13
, a comparator
14
, and a Zener diode
15
, and detects excess current based on a voltage across sense resistor
9
. Amplification circuit
12
comprises an amplifier
16
, and resistors
17
and
18
. An output from overcurrent detection circuit
11
(hereinafter referred to as an “overcurrent signal”) is inputted to an alarm latch circuit
19
. When receiving an output from alarm latch circuit
19
(hereinafter referred to as an “alarm signal”), a voltage control circuit
20
controls switching element
2
to stop generating pulses.
Next, the operation of overcurrent detection circuit
11
will be described. An amplified voltage across sense resistor
9
, which corresponds to an output current to load
10
, is compared with a reference voltage V
Z
, by comparator
14
. The reference voltage V
Z
is a value used to determine whether the output current is in a state of overcurrent. That is, when the voltage across sense resistor
9
exceeds the reference voltage V
Z
, the output current is determined to be in a state of overcurrent.
When detecting the state of overcurrent, overcurrent detection circuit
11
outputs the overcurrent signal to alarm latch circuit
19
. Alarm latch circuit
19
holds the overcurrent state and releases the state when it receives a release signal from another circuit (not shown in FIG.
3
). While alarm latch circuit
19
holds the overcurrent state, voltage control circuit
20
outputs the alarm signal which causes switching element
2
to switch off. When the input is cut off in this way, DC/DC converter
300
shifts to a state in which it provides no output.
Recently, an electronic device in which two DC/DC converters are connected in parallel to a single common load to achieve improved reliability, has been provided. In this device, even when one of the DC/DC converters fails, the other continues to provide a load with a constant voltage. Therefore, this device can be used in a computer system which requires continuous operation, such as a non-stop server computer.
FIG. 4
is an exemplary graph depicting the volt-ampere characteristic of two DC/DC converters. In this device, while both DC/DC converters provide power to the load (hereinafter referred to as “two converter operation”) in parallel, the output current from each DC/DC converter is one-half of the value output when a single DC/DC converter provides power to the load (hereinafter referred as to “single converter operation”). However, in this case of both converters being provided as DC/DC converter
300
, even if the output current is one-half during two converter operation, the reference voltage V
Z
is the same as during single converter operation. As a result, the sensitivity of each of the two DC/DC converters to an overcurrent state of output is deteriorated during double operation.
Therefore, there is a need for a high-reliability multiple power supply unit, which maintains its sensitivity to an overcurrent state of output even when two DC stabilized power supply units are connected in parallel to a single common load.
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention solves the problem in the art related to the sensitivity to an overcurrent by providing a multiple power supply unit. The multiple power supply unit comprises a plurality of individual power supplies, including first and second power supplies, which provide electrical power in parallel to a load. Each individual power supply includes: an overcurrent detection circuit for detecting excess output current to the load relative to a reference value, means for providing an operation indication of the individual power supply, each of the first and second power supplies coupled to receive the operation indication of the second and first power supplies, respectively, and a reference value circuit for changing the reference value when the operation indication is received.
Also in accordance with the present invention, there is provided a multiple power supply unit. The multiple power supply unit comprises a plurality of individual power supplies, including first and second power supplies, which provide electrical power in parallel to a load. Each individual power supply includes: means for detecting excess output current to the load relative to a reference value, means for providing an operation indication of the individual power supply, each of the first and second power supplies coupled to receive the operation indication of the second and first power supplies, respectively, and means for changing the reference value when the operation indication is received.
Further in accordance with the present invention, there is provided a multiple power supply unit. The multiple power supply unit comprises first and second power supplies which provide electrical power in parallel to a load. Each power supply includes: a transformer including a primary circuit and a secondary circuit, the primary circuit connecting to a power source, and the secondary circuit connecting to the load, means for extracting a voltage generated across a resistor in the secondary circuit, means for detecting excess output current to the load by comparing the generated voltage to a reference voltage, means for controlling an input to the primary circuit from the power source, based on whether the excess current is detected, means for providing an operation indication of the power supply, each of the first and second power supplies coupled to receive the operation indication of the second and first power supplies, respectively, and means for changing the reference voltage when the operation indication is received.
Additionally in accordance with the present invention, there is provided a power supply. The power supply for use in a multiple power supply unit that includes a plurality of the power supplies which provide electrical power in parallel to a load. The power supply comprises: an overcurrent detection circuit for detecting excess output current to the load relative to a reference value, means for providing an operation indication of the power supply to another one of the power supplies, means for receiving the operation indication from another one of the power supplies, and a reference value circuit for changing the reference value when the operation indication is received.
Also in accordance with the present invention, there is provided a power supply. The power supply for use in a multiple power supply unit that includes a plurality of the power supplies which provide electrical power in parallel to a load. The power supply comprises: means for detecting excess output current to the load relative to a reference value, means for providing an operation indication of the power supply to another one of the power supplies, means for receiving the operation indication from another one of the power supplies, and means for changing the reference value when the operation i
Higashi Shinya
Ito Kazuhiro
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Riley Shawn
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