Electric heating – Heating devices – With power supply and voltage or current regulation or...
Reexamination Certificate
2002-05-31
2004-01-20
Jeffery, John A. (Department: 3742)
Electric heating
Heating devices
With power supply and voltage or current regulation or...
C219S494000, C219S702000, C219S723000, C323S371000
Reexamination Certificate
active
06680463
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power supply control circuit whose electric power consumption can be decreased by cutting off the power supply to a controller in a stand-by state, and to a cooking device having the power supply control circuit.
2. Description of Related Art
FIG. 1
, which is a circuit diagram of the first example of prior art, shows a power supply control circuit provided in a cooking device which has a door. In
FIG. 1
, a commercial AC power source
1
is connected with power lines
1
a
and
1
b
for supplying electric power to a load
6
of the cooking device. Used as the load
6
is, for example, a high-frequency generating circuit when the cooking device is a microwave oven, or a heater when the cooking device is a thermal heating oven.
Connected in series to the power line
1
a
are a filter coil
9
a
, a starting power supplying switch
3
and a power supply holding switch
4
constituted of a relay switch, which is controlled to be in an on-state in response to power supply to a controller
8
for use of the cooking device and controlled to be in an off-state when the cooking device is in a nonuse state. The starting power supplying switch
3
is connected to a terminal of the load
6
. The starting power supplying switch
3
, which is a door switch operating in response to the opening/closure of a door (not shown) of the cooking device, has a common terminal
3
a
connected to the power line
1
a
, a closure terminal
3
b
which is connected to the common terminal
3
a
when the door is in a closed state, and an opening terminal
3
c
which is connected to the common terminal
3
a
when the door is in an open state. The closure terminal
3
b
is connected to the load
6
. The opening terminal
3
c
is connected to the AC power source
1
via an auxiliary power line
1
c.
Connected in series to the power line
1
b
are a filter coil
9
b
and a load exciting control relay switch
5
for controlling on/off of power supply from the AC power source
1
to the load
6
. The load exciting control relay switch
5
is connected to the other terminal of the load
6
.
Connected between the power lines
1
a
and
1
b
are a radio interference suppression capacitor
2
for suppressing radio interference and primary side terminals
7
a
and
7
b
of a stepdown transformer
7
which constitutes a control power supply unit. Moreover, radio interference suppression capacitors
12
and
13
(respectively having a capacity of 3,000 to 4,000 picofarad, for example) are respectively connected between the power line
1
a
and a grounded contact and between the power line
1
b
and the grounded contact.
Secondary side terminals
7
c
and
7
d
of the stepdown transformer
7
are connected via a rectification smoothing circuit (omitted in the figure) to a controller
8
which generates various kinds of control signals used for various kinds of control operations in the cooking device. A power supply holding control signal
4
s
outputted from the controller
8
controls the power supply holding switch
4
to be in an on-state. The power supply holding switch
4
is held in the on-state as long as the power supply holding control signal
4
s
is outputted. A load exciting control signal
5
s
outputted from the controller
8
controls on/off of a load exciting control relay switch
5
.
The following description will explain the operations of the power supply control circuit. When the door is opened to place a material to be cooked in a cooking chamber for use of the cooking device, the common terminal
3
a
of the starting power supplying switch
3
constituted of a door switch is connected to the opening terminal
3
c
, and electric power is supplied from the AC power source
1
via the auxiliary power line
1
c
to the stepdown transformer
7
. Upon the power supply to the stepdown transformer
7
, the controller
8
is put into an operative state and outputs a power supply holding control signal
4
s
. The power supply holding control signal
4
s
turns on the power supply holding switch
4
, and the power line
1
a
is connected to the AC power source
1
via the power supply holding switch
4
. Since the power supply holding control signal
4
s
holds the power supply holding switch
4
in the on-state, power supply to the stepdown transformer
7
via the power lines
1
a
and
1
b
is maintained and thereby the controller
8
is kept in an operative state even when the door of the cooking device is closed again, the common terminal
3
a
of the starting power supplying switch
3
is connected to the closure terminal
3
b
again and power supply from the AC power source
1
via the opening terminal
3
c
is cut off.
Next, in response to an operator guidance through an operator control panel (not shown), the controller
8
outputs a load exciting control signal
5
s
. The load exciting control signal
5
s
turns on the load exciting control relay switch
5
, electric power is supplied from the AC power source
1
to the load
6
via the power lines
1
a
and
1
b
, and a predetermined cooking operation is performed.
When the cooked material is taken out of the cooking chamber after the cooking operation finishes and it is judged that the cooking device is in a nonuse state (the judgment is performed based on, for example, whether opening/closure of the door is detected within a predetermined time after the detection of the opening/closure of the door at the end of the cooking operation), the output of the power supply holding control signal
4
s
stops, the power supply holding switch
4
is turned off, and thereby the electric power consumed while the controller
8
is in a stand-by state, i.e. since the controller
8
is put into a non-operative state until the cooking device is used next, is reduced.
FIG. 2
, which is a circuit diagram of the second example of the prior art, shows a power supply control circuit provided in a cooking device which has a door. It should be noted that like codes are used to refer to like parts in this figure and
FIG. 1
, and detailed explanation thereof is omitted here. In
FIG. 2
, a door switch
31
is of a single junction type, and does not have the opening terminal
3
c
and the auxiliary power line
1
c
shown in
FIG. 1. A
push switch
11
as a starting power supplying switch is connected in parallel to the power supply holding switch
4
. When the door of the cooking device is in a closed state, the door switch
31
is in an on-state, i.e., the terminal
31
a
connected to the power line
1
a
is connected with the terminal
31
b
connected to the load
6
.
By pushing the push switch
11
for use of the cooking device, the push switch
11
is put into an on-state only while being pushed. When the push switch
11
is put into the on-state, the power line
1
a
is connected to the AC power source
1
and electric power is supplied to the stepdown transformer
7
via the power lines
1
a
and
1
b
. Upon the power supply to the stepdown transformer
7
, the controller
8
is put into an operative state and outputs a power supply holding control signal
4
s
. The power supply holding control signal
4
s
turns on the power supply holding switch
4
, and the power line
1
a
is connected to the AC power source
1
via the power supply holding switch
4
.
The power supply holding control signal
4
s
holds the power supply holding switch
4
in the on-state even when the pushing operation against the push switch
11
is released and the push switch
11
is turned off. Consequently, power supply to the stepdown transformer
7
via the power lines
1
a
and
1
b
is maintained and the controller
8
is kept in the operative state.
FIG. 3
, which is a circuit diagram of the third example of the prior art, shows a power supply control circuit provided in a cooking device which has a door. It should be noted that like codes are used to refer to like parts in this figure and
FIGS. 1 and 2
, and detailed explanation thereof is omitted here. In
FIG. 3
, the terminals of the power su
Jeffery John A.
Sharp Kabushiki Kaisha
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