Field of the Invention
The present invention relates to a load control system.
Background of the Invention
Conventionally, there has been provided a load control
system for operating only a preset load by supplying a power
from a backup power supply to the corresponding load during
a power failure (see, e.g., Japanese Patent Laid-open
Publication No. 2009-148009).
The load control system described in Patent Document 1
supplies a DC power from a main power supply to DC devices
connected to DC power supply lines and also supplies a
backup power from a backup power supply provided in addition
to the main power supply to the DC devices via the DC power
supply lines during a power failure in the main power
supply. Thus, the DC devices can operate for a
predetermined period of time even during the power failure
in the main power supply.
In the above-described load control system, when the
power is supplied from the backup power supply to all the DC
devices connected to the DC power supply lines during the
power failure, the backup power supply is used intensively.
Therefore, the power is backed up only for a short period of

time, which results in requirement of a large capacity
backup power supply. Hence, in the load control system
described in Patent Document 1, the DC devices are
configured to have communications functions, and operation
stop is instructed to the DC devices having low priority
through communications when a power failure occurs. As a
consequence, the power consumption is reduced, and the power
backup time is extended.
In such load control system, since the load devices
need to have the communications functions for instructing
the operation stop during the power failure, the cost of the
system increases and specific load devices having the
communications functions are required.
Summary of the Invention
In view of the above, the present invention provides a
low-cost load control system which can back up a power to a
required load device for a long period of time during a
power failure.
In accordance with an embodiment of the present
invention, there is provided a load control system,
including: a power supply control unit for controlling a
power feeding to multiple load devices; and a backup power
supply unit for supplying backup power during a power
failure, wherein, during a power failure, the power supply

control unit supplies the power only to a part of load
devices selected among the load devices, and the load
devices are devoid of communications function for
communicating with the power supply control unit.
Further, the load control system may further include:
a power supply unit for supplying an operation power of the
whole system; a load operation terminal connected to the
power supply control unit via a communications line; a power
failure notification unit for outputting, when a the power
failure is detected, a power failure notification signal to
the power supply control unit; and a number of load
circuits, each of which having one or more of the load
devices connected to the power supply control unit via power
lines, wherein the power supply control unit includes power
feeding on/off units, each of which being connected to one
of the load circuits, to independently turn on or off the
power feeding to corresponding load circuits, thereby
operating or stopping the load devices of the load circuits;
a first communications unit for receiving a load control
signal inputted via the communications line; and a control
circuit for switching on or off one or more power feeding
on/off units corresponding to the load control signal
received by the first communications unit, the load
operation terminal includes an operation unit for performing
on/off operation of one or more target load circuits; and a
second communications unit for receiving an operation input

from the operation unit and outputting to the communications
line the load control signal for controlling said one or
more the power feeding on/off units corresponding to the
target load circuits, and the control circuit of the power
supply control unit controls, when the power failure
notification signal is received from the power failure
notification unit, the power feeding on/off units to supply
the backup power from the backup power supply unit only to a
part of the load circuits.
In accordance with the configuration described above,
the backup power is supplied from the backup power supply
unit to only the selected load circuits during the power
failure without being supplied to other load circuits.
Thus, it is possible to achieve the load control system
which can back up the power to a required load device for a
longer period of time. Further, since the load devices do
not require the communications functions, general low-cost
devices having no communications function can be used as the
load devices. Accordingly, a low-cost load control system
can be achieved. Moreover, since a decision on whether or
not to supply the.backup power during the power failure is
set to every load circuit connected to one or more load
devices, the setting can be simplified compared to the case
of setting whether or not to supply the backup power to
every load device during the power failure.
Further, the power supply control unit may further

include a setting unit for setting one or more load circuits
to which the backup power is supplied during the power
failure; and when the power failure notification signal is
received, the control circuit may control the power feeding
on/off units to supply the backup power from the backup
power supply unit only to the load circuits set by the
setting unit.
In accordance with the configuration described above,
the setting for determining whether or not to supply the
backup power during the power failure can be easily changed
by using the setting unit.
Further, the backup power supply unit may include a
secondary battery, the power supply unit may supply a DC
power as the operation power, and the first and the second
communications unit may receive and transmit the load
control signal by superposing signals on DC voltage.
In accordance with the configuration described above,
the entire system is operated by the supplied DC power, and
the load devices do not require AC-DC converters for
converting an AC power to a DC power. Therefore, conversion
loss caused by the AC-DC conversion does not occur, and the
power can be saved. When the load devices are operated by
the AC power, it is required to convert an output of a
secondary battery to an AC power and supply the AC power to
the load devices during the power failure. Hence, the
conversion loss is caused by the DC-AC conversion, and the

control circuit may control the power feeding on/off units
to return to the power feeding state immediately before the
power failure occurs based on the power feeding state stored
in the storage unit.
In accordance with the configuration described above,
when the power failure is recovered, the power feeding
states of the load circuits immediately before the power
failure can be recreated.
Brief Description of the Drawings
The objects and features of the present invention will
become apparent from the following description of
embodiments, given in conjunction with the accompanying
drawings, in which:
Fig. 1 shows a schematic system configuration of a load
control system in accordance with an embodiment of the
present invention;
Fig. 2A describes a block diagram of a power supply
control unit used in the load control system;
Fig. 2B depicts a block diagram of principal parts of
a modification of the power supply control unit; and
Fig. 3 provides a block diagram of a load operation
terminal used in the load control system.

Detailed Description of the Embodiments
The embodiments of the present invention will be
described with reference to the accompanying drawings which
form a part hereof. Throughout this specification and the
drawings, like reference numerals designate like parts
having substantially identical functions, and redundant
description thereof will be omitted.
Hereinafter, the embodiments of the present invention
will be described with reference to the drawings which form
a part hereof. Although an example in which a load control
system of the present invention is applied to a detached
house will be described in the following embodiments, the
load control system can be applied to an apartment, a
business building or the like.
As shown in Fig. 1, a house H has therein DC devices 4
(e.g., an LED lighting device, a ventilation fan, an air
conditioner, audio/video equipments and the like) as load
devices which are operated by a DC power supplied thereto,
and a load control system 1 for turning on/off the DC power
feeding to the DC devices 4 connected to a plurality of load
circuits.
In the load control system 1, a DC power supply unit
for supplying a DC power for operating the entire system
includes an AC-DC converter (not shown) for converting an AC
power supplied from a commercial AC power supply AC for

domestic use to a DC power, a fuel cell FC for generating a
power by chemical reaction of materials, a solar cell 8 for
generating a power from sunlight, and a storage battery 9
which is charged during a normal state other than power
failure and discharges during the power failure. The DC
power is supplied from the DC power supply unit to the load
circuits.
The storage battery 9 includes a secondary battery
such as a lithium battery or the like, and is charged during
the power feeding period and discharges during the power
failure. The fuel cell FC generates a power by
electrochemical reaction between hydrogen and oxygen as
source materials. The storage battery 9 and the fuel cell
FC can supply the DC power during the power failure in the
commercial AC power supply AC and thus form a backup power
supply unit 50 for supplying a backup power during the power
failure in the commercial AC power supply AC.
In addition, an AC power distribution unit 7 for
distributing the AC power supplied from the commercial AC
power supply AC to branch circuits is installed in the house
H, so that the AC power is supplied from the AC power
distribution unit 7 to an AC device 6 driven by the AC
power.
In this system, a control unit 10 and a DC power
distribution unit 11 having therein a DC breaker (not shown)
serve as a power distribution unit for distributing the DC

power supplied from the DC power supply unit to a plurality
of load circuits. Further, one or more (e.g., two in this
embodiment) relay units 2 (2a and 2b) serving as power
supply control units are connected between the DC power
distribution unit 11 and the load circuits. When the relay
units are separately described, reference numerals 2a and 2b
are used, whereas when common features of the relay units 2a
and 2b are described, reference numeral 2 is used.
The DC power is supplied from the DC power
distribution unit 11 to the relay units 2 via DC power lines
17. Moreover, a plurality of DC power lines 20 are
connected to the relay units 2. Accordingly, the DC devices
4 of the respective circuits can be operated or stop
operation by independently turning on/off the power feeding
to the DC power lines 20 of the respective circuits, as will
be described later.
The AC power is supplied from the AC power
distribution unit 7 to the control unit 10 via an AC power
line 13, wherein the control unit 10 has therein an AC-DC
converter (not shown) for converting the AC power to a DC
power of a predetermined voltage. Further, the DC powers
are supplied from the fuel cell FC and the solar cell 8 to
the control unit 10 via DC power lines 5 and 14 to be
converted into a DC power having a predetermined voltage by
a DC-DC converter (not shown) installed in the control unit
10. The converted DC power is outputted to the DC power

distribution unit 11 via a DC power line 16. The control
unit 10 charges the storage battery 9 via a DC power line 15
with the power generated from the solar cell 8.
Further, the control unit 10, for example, when the
power feeding from the commercial AC power supply AC is
stopped due to a power failure or the like and the power
generated by the solar cell 8 is smaller than the
consumption power of the DC devices 4, discharges the
storage battery 9. Also in this case, the DC powers
supplied to the control unit 10 from the solar cell 8 and
the fuel cell FC as well as from the storage battery 9 are
supplied to the DC power distribution unit 11. Furthermore,
the control unit 10 has a function of delivering data with
respect to the DC power distribution unit 11 via a signal
line 18. Thus, the control unit 10 outputs, when detecting
an abnormal state such as a power failure in the commercial
AC power supply AC, an abnormal notification signal
indicating the occurrence of the abnormal state to the DC
distribution unit 11.
The DC power distribution unit 11 serves as a DC
breaker for blocking a DC power, and distributes the DC
power supplied from the control unit 10 to the relay units 2
via the power lines 17. In addition, the DC power
distribution unit 11 is connected to the control unit 10 via
the signal line 18 and also connected to the relay units 2
via signal lines 19, so that the data can be transmitted

between the control unit 10 and the relay units 2.
For example, when the control unit 10 detects a power
failure in the commercial AC power supply AC, a power
failure notification signal is transmitted to the DC power
distribution unit 11 and then to the relay units 2a and 2b.
Further, the DC power distribution unit 11 supplies the DC
power via DC power line 22 to a DC socket 12 installed in
the house H in the form of, e.g., a wall socket or a bottom
socket. When a plug of a DC device (not shown) is inserted
into the DC socket 12, the DC power is directly supplied to
the DC device.
The relay units 2 are connected to the DC power lines
20, and the respective DC power lines 20 are connected to
one or more DC devices 4, forming a plurality of, e.g.,
four, load circuits. The relay units 2 can independently
turn on/off the supply of the DC power to the respective
load circuits. Further, only one of the relay units 2a and
2b, i.e., the relay unit 2a (main body), is connected to
load operation terminals 3 for operating turn-on/off of the
power feeding to their corresponding load circuits via the
power line 21 (communications line) . The relay unit 2a is
connected to the other relay unit 2b via a communications
line 23, and the communications line 23 and the power line
21 are electrically connected to each other inside the relay
unit 2a. Accordingly, signals can be transmitted between
the relay units 2 and the load operation terminals 3 via the

communications line 23 and the power line 21.
The load operation terminals 3 are operated by the DC
power supplied from the relay unit 2a and receive/transmit
data from/to the relay units 2a through power line carrier
communications using DBPSK (Differential Binary Phase Shift
Keying) in which a communications signal for transmitting
data by using a carrier wave of a high frequency is
superposed on a DC voltage (e.g., DC 24V) supplied from the
relay unit 2a to the power line 21. The relay units 2a and
2b supply the DC power (e.g., DC 48V) from the DC power
distribution unit 11 to the power lines 20 and convert the
operation states of the DC devices connected to load
circuits as control targets by turning on/off the power
feeding to the load circuits based on load control signals
inputted from the load operation terminals 3.
Hereinafter, configurations of the relay units 2 and
the load operation terminals 3 will be described in detail
with reference to Figs. 2A and 3.
As depicted in Fig. 2A, each relay unit 2 includes: a
control unit 30 including, e.g., a microcomputer, for
performing overall control of the relay unit 2; a power
receiving unit 31 for receiving the DC power from the DC
power distribution unit 11 via the DC power line 17 and
supplying an operation power to the control unit 30 and the
like; circuit opening/closing control units 32a to 32d
(power feeding on/off units), provided between the power

receiving unit 31 and the DC power lines 20, for turning
on/off the power feeding to the DC power lines 20 by turning
on/off relays installed therein (not shown) based on
opening/closing control signals inputted from the control
unit 30; a communications unit 33 (first communications
unit) for supplying a DC voltage (DC 24V) obtained by
decreasing the DC voltage supplied from the power receiving
unit 31 to the power line 21 and delivering a communications
signal between the load operation terminals 3 and the DC
power distribution unit 11 by superposing the communications
signal on the DC voltage by using DBPSK; a storage unit 34
including an electrically rewritable nonvolatile memory
(e.g., EEPROM (Electrically Erasable Programmable Read-Only
Memory), flash memory or the like), for storing the power
feeding states of the load circuits, identification
information of the relay unit 2, a multicast address to be
described later and the like; multiple on/off switches 35a
(though Fig. 2A depicts just one on/off switch) provided for
respective load circuits, each for setting whether to adopt
a corresponding load circuit as a control target; a
registration completion switch 35b for completing a
registration mode to be described later; setting switches
35c for setting whether or not to supply the power on a load
circuit basis during a power failure; an operation input
receiving unit 35 for receiving operation inputs from the
on/off switches 35a, the registration completion switch 35b,

and the setting switches 35c; and an operation display unit
36 including, e.g., a display lamp such as a light emitting
diode or the like, for displaying the power feeding states
of the load circuits or the operation state of the relay
unit 2 by changes in the light output state (light on, light
off and light blink).
Meanwhile, as shown in Fig. 3, each load operation
terminal 3 includes: a control unit 40 including, e.g., a
microcomputer, for performing overall control of the load
operation terminal 3; a power receiving unit 41 for
receiving the DC power from the relay unit 2 via the power
line 21; a power circuit unit 42 for generating an operation
voltage of the control unit 40 or the like from the DC power
received by the power receiving unit 41; a communications
unit 43 (second communications unit) for receiving and
transmitting a communications signal from and to. the relay
unit 2 by superposing the communications signal on the DC
voltage (DC 24V) supplied from the relay unit 2 by using
DBPSK; a storage unit 44 including an electrically
rewritable nonvolatile memory (e.g., EEPROM, flash memory or
the like), for storing information indicating correspondence
between the on/off switches and the load circuits as control
targets, identification information of the load operation
terminal 3, a multicast address and the like; an on/off
switch 45a serving as an operation device, for performing
operation for turning on/off the power feeding to the load

circuits as control targets independently; a registration
switch 45b for starting the registration mode to be
described later; an operation input receiving unit 45 for
receiving an operation input from the on/off switch 45a and
the registration switch 45b; and an operation display unit
4 6 including, e.g., a display lamp such as a light emitting
diode or the like, for displaying the power feeding states
of the load circuits as control targets or the operation
mode of the load operation terminal 3 by changes in the
light output state (light on, light off and light blink).
Here, the identification information assigned to the
relay units 2 and the load operation terminals 3 may be
unique physical addresses such as MAC (Media Access Control)
addresses assigned by a hardware manufacturer, or addresses
randomly assigned by a user. Preferably, the same
identification information (address) is not assigned to the
relay units 2 and the load operation terminals 3 of the same
system.
The following is description of the operation of the
system.
First, an operation for matching the load circuits as
control targets with one or more on/off switches 45a of the
load operation terminals 3 will be described.
When a user operates the registration switch 45b on
one of the load operation terminals 3, the operation input
of the registration switch 45b is inputted to the control

unit 40 via the operation input receiving unit 45. The
control unit 40 that has received the operation input of the
registration switch 45b converts the operation mode from a
normal mode, for performing on/off operation with regard to
the power feeding to the load circuits, to a registration
mode .
When the on/off switch 45a as a setting target
operates in the registration mode, the operation input of
the on/off switch 45a is inputted to the control unit 40 via
the operation input receiving unit 45. The control unit 40
makes a display lamp corresponding to the operated on/off
switch 45a, e.g., flicker to thereby indicate that a load
circuit as a control target of the on/off switch 45a is
being set. Further, the control unit 40 generates a
communications signal including a control command for
converting the operation mode of the relay unit 2 to the
registration mode and multicast-transmits the communications
signal from the communications unit 43. At this time, a
multicast address is used as a destination address, and
identification information of the load operation terminal 3
is used as a source address.
Since all of the relay units 2 and the load operation•
terminals 3 are assigned with multicast addresses and the
signal is multicast-transmitted between the relay units 2
and the load operation terminals 3, it is possible to avoid
a mistaken operation that may occur when the relay unit 2 or

the load operation terminal 3 which is not assigned with
multicast addresses is additionally connected. If such
problems are negligible, the signal can be broadcast-
transmitted between the relay units 2 and the load operation
terminals 3.
When the communications signal transmitted from the
load operation terminals 3 is received by the communications
unit 33 of the relay unit 2, the control unit 30 of the
relay unit 2 converts the operation mode from the normal
mode to the registration mode based on the communications
signal received by the communications unit 33 and then
displays on the operation display unit 36 that the operation
mode has changed to the registration mode. Further, when a
user operates an on/off switch 35a corresponding to a
desired load circuit in the registration mode, the operation
input of the on/off switch 35a is inputted to the control
unit 30 via the operation input receiving unit 35.
The control unit 30 that has received the operation
input of the on/off switch 35a makes a display lamp
corresponding to the operated on/off switch 35a, e.g.,
flicker to thereby indicate that the load circuit
corresponding to the on/off switch 35a has been set as a
control target. Moreover, the control unit 30 generates a
communications signal including the load number of the
selected load circuit and unicast-transmits the
communications signal from the communications unit 33 to the

load operation terminal 3 that has requested the
registration. At this time, identification information of
the relay unit 2 is used as a destination address, and
identification information of the load operation terminal 3
that has requested the registration is used as a source
address.
In the load operation terminal 3 that has requested
the registration, the communications unit 43 receives the
communications signal transmitted from the relay unit 2, and
the control unit 40 creates a data table which matches the
on/off switch 45a as the setting target to the load circuit
as the control target based on the load number and the
identification information of the relay unit 2 which are
included in the communications signal. The created data
table is temporarily stored.
If multiple load circuits need to be set as the
control target of the on/off switch 45a, the user
continuously operates other on/off switches 35a of the relay
units 2a and 2b. Then, the load circuits corresponding to
the operated on/off switches 35a are set as the control
target, and communications signals for registering these
load circuits are transmitted to the load operation terminal
3. In the load operation terminal 3, the data table is
updated to match the on/off switch 45a as the setting target
to the multiple load circuits as the control target, and the
renewed data table is temporarily stored.

After one or more load circuits are selected as the
control target of the on/off switch 45a by the above-
described operation, a user operates the registration
completion switch 35b of one of the relay units 2a and 2b to
thereby input the operation input of the registration
completion switch 35b to the control unit 30 via the
operation input receiving unit 35.
The control unit 30 that has received the operation
input of the registration completion switch 35b generates a
communications signal including a control command for
converting the operation mode from the registration mode to
the normal mode and multicast-transmits the communications
signal from the communications unit 33. At this time, a
multicast address is used as a destination address.
Further, the control unit 30 converts the operation mode
from the registration mode to the normal mode and displays
on the operation display unit 36 that the operation mode has
been changed to the normal mode.
Meanwhile, in the load operation terminal 3 that has
requested the registration, when the communications unit 43
receives the communications signal transmitted from the
relay unit 2, the control unit 40 stores in the storage unit
44 the data table created by the aforementioned process, in
which the on/off switch 45a as the setting target
corresponds to one or more load circuits as the control
target.

Moreover, the control unit 40 of the load operation
terminal 3 converts the operation mode from the registration
mode to the normal mode and displays on the operation
display unit 4 6 that the operation mode has been changed to
the normal mode, thereby completing the registration mode.
In the above description, whenever the load circuits
corresponding to the on/off switch 45a of the load operation
terminal 3 are selected by the relay units 2a and 2b in the
registration mode, the load numbers of the selected load
circuits are notified to the load operation terminal 3.
However, it is also possible to temporarily store the load
numbers of the load circuits selected by the relay units 2a
and 2b and notify the load numbers of the selected load
circuits when the registration completion switch 35b in the
relay unit 2 is operated.
In the above-described manner, the operation of
matching the load circuits to the on/off switch 45a of the
load operation terminal 3 is carried out, and a user
performs the setting operation for all the load operation
terminals 3. Depending on the setting operation, one or
more load circuits as the control target can correspond to
the on/off switch 45a of one of the load operation terminals
3.
In this system, the operation of matching the on/off
switches 45a of the load operation terminals 3 to the load
circuits (circuit opening/closing control units 32a to 32d)

as control targets is performed by using various switches
provided at the load operation terminals 3 and the relay
units 2. Therefore, an additional setting device for
matching is not required. However, an additional setting
device (not shown) for matching may be provided to perform
the matching of the on/off switches 45a of the load
operation terminals 3 to the load circuits as control
targets.
Hereinafter, an operation for turning on/off the power
feeding to a desired load circuit by using the load
operation terminal 3 will be described.
If the user operates the on/off switch 45a of the load
operation terminal 3 while the relay units 2 are being
operated in a normal mode, the operation input of the on/off
switch 45a is inputted to the control unit 40 via the
operation input receiving unit 45. The control unit 40
reads a load number of a load circuit corresponding to the
operated on/off switch 45a from the data table stored in the
storage unit 44. Further, the control unit 40 generates a
communications signal including the load number and a
control command for turning on/off the power feeding to the
load circuit and transmits this communications signal to the
corresponding relay unit 2 via the communications unit 43.
In the relay unit 2 that has received the
communications signal, the control unit 30 turns on/off the
power feeding to the load circuit as a control target by

turning on/off the corresponding circuit opening/closing
control units 32a to 32d based on the control command and
the load number included in the communications signal
received by the communications unit 33. Subsequently, the
control unit 30 multicast-transmits, from the communications
unit 33 to all the load operation terminals 3, a state
notification signal (including the load number of the
control target) for notifying the on/off state of the power
feeding to the load circuit as the control target.
Then, in each of the load operation terminals 3, the
communications unit 43 receives the state notification
signal transmitted from the relay unit 2 and displays the
operation state of the DC device 4 by turning on/off a
display lamp corresponding to the on/off switch 45a in
accordance with the operation state of the DC device 4
corresponding to the on/off switch 45a. Thus, in the load
operation terminal 3, the on/off state of the load circuit
corresponding to the on/off switch 45a can be checked by the
light output state of the display lamp, which is preferable
in switching an on/off state of the DC device 4 installed in
a separate place.
Further, if one or more load circuits correspond to a
single on/off switch 45a, the control unit 40 may turn on
the display lamp corresponding to the on/off switch 45a when
the power feeding to all the load circuits corresponding to
the on/off switch 45a is stopped, and may turn off the

display lamp when the power is supplied to at least one load
circuit corresponding to the on/off switch 45a. Hence, the
power feeding state of one or more load circuits as control
targets can be checked by using the single display lamp. In
addition, since the control unit 40 turns off the display
lamp if the power is supplied to at least one load circuit,
a user can stop the power feeding to all the load circuits
by checking the display state of the display lamp.
The following is a description of an operation for
backing up an operation power of the load device during a
power failure. Each relay unit 2 has the setting switches
35c (e.g., slide switches) which are provided for each of
the circuit opening/closing control units 32a to 32d so as
to set whether or not to supply the power to the load
circuits corresponding to the circuit opening/closing
control units 32a to 32d during the power failure.
When the control unit 10 serving as a power failure
notification unit detects a power failure in the commercial
AC power supply AC, the control unit 10 makes the fuel cell
FC start power generation and makes the storage battery 9
start discharging. Moreover, the control unit 10 supplies
the power generated from the fuel cell FC, the power
discharged from the storage battery 9 and the power
generated, from the solar cell 8 to the power distribution
unit 11 and transmits a power failure notification signal
indicating occurrence of the power failure to the relay

units 2 via the DC power distribution unit 11.
When the communications unit 33 of the relay unit 2
receives the power failure notification signal, the control
unit 30 of the relay unit 2 starts the control operation
required during the power failure based on the power failure
notification signal received by the communications unit 33.
In detail, the control unit 30 stores in the storage unit 34
the power feeding states of the load circuits at that time
(immediately before the occurrence of the power failure)
and, then, turns on only the circuit opening/closing control
units 32a to 32d set by the setting switches 35c and turns
off the other circuit opening/closing control units 32a to
32d.
Hence, in the abnormal state such as the power failure
or the like, the DC power can be supplied to only load
circuits connected to desired DC devices 4 including, e.g.,
an LED lighting device, so as to operate only the desired DC
devices 4.
After the power failure is recovered and a power
failure recovery signal is transmitted from the control unit
10 to the relay units 2 via the DC power distribution unit
11 (after the power failure notification signal is
released), the control units 30 of the relay units 2 that
have received the power failure recovery signal read the
power feeding states immediately before the occurrence of
the power failure from the storage unit 34 and turn on/off

the circuit opening/closing control units 32a to 32d in
accordance with the power feeding states immediately before
the power failure.
Accordingly, the DC devices 4 of the load circuits can
be operated or stop operation as in the state immediately
before the power failure, and the power feeding states of
the load circuits immediately before the power failure can
be recreated.
Further, in a state where the relay units 2 that have
received the power failure notification signal from the
control unit 10 are supplying the power to the corresponding
load circuits by turning on only the circuit opening/closing
control units 32a to 32d set by the setting switches 35c, a
user can operate the load operation terminal 3 to stop the
operations of the DC devices 4 to which the power is being
supplied.
In detail, when a user operates the on/off switch 45a
of the load operation terminal 3 corresponding to the DC
device 4 as a control target, the communications signal in
accordance with the operation of the on/off switch 45a is
transmitted from the load operation terminal 3 to the
corresponding relay unit 2. The relay unit 2 turns off the
corresponding circuit opening/closing control units 32a to
32d in accordance with the' control instruction included in
the communications signal, thereby stopping the power
feeding to the DC devices 4 which are not required to be

operated during the power failure. Hence, the consumption
of the storage battery 9 for backup can be suppressed, and
the power of the desired DC device 4 can be backed up for a
longer period of time.
This embodiment describes the power feeding to a
desired load circuit in regard to the occurrence of the
power failure. However, the relay units 2 may be connected
to an earthquake news receiving unit, a fire detector or a
sensor for sensing a trespasser into a house. When
detecting earthquake, fire, or entry of a trespasser into a
house, the DC power can be supplied to preset load circuits
to operate DC devices 4 corresponding to the preset load
circuits.
As described above, in this system, the backup power
is supplied from the backup power supply unit 50 to only a
preset load circuit during the power failure without being
supplied to other load circuits. Therefore, the power can
be backed up to a desired DC device 4 for a longer period of
time. Further, the DC devices 4 do not have to have
communications function, so that low-cost general devices
having no communications function can be used as the DC
devices 4. Accordingly, a low-cost load control system can
be achieved.
Moreover, whether or not to back up the power during
s the power failure can be easily set on a load circuit basis
by using the setting switches 35c. Thus, the setting time

can be reduced compared to the case of setting whether or
not to back up the power during the power failure on a load
device basis.
Further, in this system, the power supply unit
supplies the DC power as the operation power; the backup
power supply unit 50 includes a storage battery (secondary
battery) 9; and the communications units 33 and 43 (first
and second communications unit) of the relay units 2 and the
load operation terminals 3 deliver the load control signals
by superposing the signals on the DC voltage. Since the DC
power is supplied to the DC devices 4 as load devices, the
load devices do not require AC-DC converters for converting
an AC power to a DC power. Therefore, conversion loss
caused by the AC-DC conversion does not occur, and the power
can be saved.
Further, when the load device is driven by the AC
power, the output of the storage battery 9 forming the
backup power supply unit 50 needs to be converted to the AC
power and then supplied to the load device during the power
failure. Hence, the conversion loss is caused by the AC-DC
conversion and the power backup time of the storage battery
9 is reduced. However, in this system, the load devices are
driven by the DC power, so that the conversion loss caused
by converting the output of the storage battery 9 to AC
power does not occur, and the power backup time of the
storage battery 9 can be extended.

In addition, as shown in Fig. 2B, a variable resistor
VR may be connected to an output of each of the circuit
opening/closing control units 32a to 32d, and the control
unit 30 may change a resistance of the variable resistor VR
between when the power failure occurs and when the power is
normally supplied (the circuit opening/closing control unit
32a being representatively shown in Fig. 2B).
Specifically, when the power failure detection signal
is inputted, the control unit 30 changes the power supplied
to the load circuit during the power failure to a relatively
lower power by changing a resistance of the variable
resistor VR to a relatively higher resistance. Therefore,
the consumption of the backup power supply unit 50 can be
reduced compared to when the power supplied in a normal
state is supplied during the power failure and, also, the DC
devices 4 can operate for a longer period of time.
When an LED lighting device is used as the DC device
4, the control unit 30 reduces the light output of the
lighting device during the power failure compared to the
light output obtained in the normal state, in consideration
of the current supplied from the backup power supply unit 50
being limited during the power failure, to thereby turn on
the lighting device for a longer period of time.
In the circuit shown in Fig. 2B, the power supplied to
the load circuit during the power failure is reduced by
changing the resistance of the variable resistor VR

connected to the output of each of the circuit
opening/closing control units 32a to 32d. However, when DC-
DC converters are embedded in each of the circuit
opening/closing control units 32a to 32d to make a voltage,
supplied from the circuit opening/closing control units 32a
to 32d to the load circuit, variable, the control unit 30
can also reduce the power supplied from the backup power
supply unit 50 to the load circuit during the power failure
by decreasing the voltage supplied to the load circuit.
While the invention has been shown and described with
respect to the embodiments, it will be understood by those
skilled in the art that various changes and modification may
be made without departing from the scope of the invention as
defined in the following claims.

WE CLAIM:
1. A load control system, comprising:
a power supply control unit for controlling a power
feeding to multiple load devices; and
a backup power supply unit for supplying backup power
during a power failure,
wherein, during a power failure, the power supply
control unit supplies the power from the backup power supply
unit only to a part of load devices selected among the load
devices, and the load devices are devoid of communications
function for communicating with the power supply control
unit.
2. The load control system of claim 1, further comprising:
a power supply unit for supplying an operation power
of the whole system;
a load operation terminal connected to the power
supply control unit via a communications line;
a power failure notification unit for outputting, when
a the power failure is detected, a power failure
notification signal to the power supply control unit; and
a number of load circuits, each of which having one or
more of the load devices connected to the power supply
control unit via power lines,
wherein the power supply control unit includes power

feeding on/off units, each of which being connected to one
of the load circuits, to independently turn on or off the
power feeding to corresponding load circuits, thereby
operating or stopping the load devices of the load circuits;
a first communications unit for receiving a load control
signal inputted via the communications line; and a control
circuit for switching on or off one or more power feeding
on/off units corresponding to the load control signal
received by the first communications unit,
the load operation terminal includes an operation unit
for performing on/off operation of one or more target load
circuits; and a second communications unit for receiving an
operation input from the operation unit and outputting to
the communications line the load control signal for
controlling said one or more the power feeding on/off units
corresponding to the target load circuits, and
the control circuit of the power supply control unit
controls, when the power failure notification signal is
received from the power failure notification unit, the power
feeding on/off units to supply the backup power from the
Backup power supply unit only to a part of the load
circuits .
3. The load control system of claim 2, wherein the power
supply control unit further includes a setting unit for
setting one or more load circuits to which the backup power

is supplied during the power failure; and
when the power failure notification signal is received,
the control circuit controls the power feeding on/off units
to supply the backup power from the backup power supply unit
only to the load circuits set by the setting unit.
4. The load control system of any one of claims 2 to 3,
wherein the backup power supply unit includes a secondary
battery, the power supply unit supplies a DC power as the
operation power, and the first and the second communications
unit receive and transmit the load control signal by
superposing signals on DC voltage.
5. The load control system of any one of claims 2 to 4,
wherein a power level of the backup power supplied by the
backup power supply unit during the power failure is less
than that of the operation power supplied by the power
supply unit in a normal state other than the power failure.
6. The load control system of claim 5, wherein the load
devices are lighting devices.
7. The load control system of any one of claims 2 to 6,
wherein the power supply control unit further
includes a storage unit for storing a power feeding
state of the respective load circuits immediately

before the power failure occurs; and when the power
failure is recovered, the control circuit controls
the power feeding on/off units to return to the
power feeding state immediately before the power
failure occurs based on the power feeding state
stored in the storage unit.

ABSTRACT

A load control system includes: a power supply control
unit for controlling a power feeding to multiple load
devices; and a backup power supply unit for supplying backup
power during a power failure. During a power failure, the
power supply control unit supplies the power from the backup
power supply unit only to a part of load devices selected
among the load devices, and the load devices are devoid of
communications function for communicating with the power
supply control unit.