Electricity: motive power systems – Having plural – diverse or diversely controlled sources – Different voltages
Reexamination Certificate
2002-06-03
2003-12-02
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Having plural, diverse or diversely controlled sources
Different voltages
C318S139000, C318S433000, C318S436000, C062S228100, C062S244000, C320S118000, C320S166000, C323S288000, C323S908000
Reexamination Certificate
active
06657408
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an air conditioner including a motor-driven compressor operated with power supplied from a DC power source.
BACKGROUND OF THE INVENTION
A conventional air conditioner for vehicles including a motor-driven compressor operated with power supplied from a DC power source is shown in FIG.
14
. The air conditioner includes output unit
11
for DC/AC-converting a DC current for supply an AC current to motor-driven compressor
14
, and capacitor
7
for smoothing the DC current of rectangular waveform. While breaker
3
being closed, the capacitor
7
is charged by battery
1
via fuse
2
, breaker
3
, and reverse-connection-protecting diode
4
through a charge resistor
5
for preventing a charge inrush current. The reverse-connection-protecting diode
4
protects the circuit by cutting off the current if the battery
1
is connected in reverse polarity.
Control unit
10
, upon receiving a command to operate the motor-driven compressor
14
from air-conditioner controller
12
, detects the charge of capacitor
7
and closes relay
6
, for example, when the voltage of capacitor
7
detected by voltage detector
8
reaches a predetermined level. Then, the control unit
10
instructs the output unit
11
to drive the motor-driven compressor
14
. The control unit
10
is supplied with power from 12V power source
13
. Switching power supply
9
converts the voltage of battery
1
to supply the power to the output unit
11
and voltage detector
8
. Control unit
10
, upon receiving a command to stop the motor-driven compressor
14
from the air-conditioner controller
12
, stops the output of the output unit
11
and opens the relay
6
.
The control unit
10
is always in operation since receiving a power from 12V power source
13
. Accordingly, the unit is always possible to communicate with controller
12
, receive a signal from a sensor for air conditioning, and check the circuit with a circuit-checking device.
FIG. 15
is a circuit diagram of another conventional air conditioner. The control unit
10
receives a power from switching power supply
9
, and receives no power from 12V power source
13
. The conditioner has a simple structure in which a connection with 12V power source
13
is not needed, and a common ground can be used for the control unit
10
and other circuits. Constant current charging circuit
15
supplies a constant current obtained through subtracting a base-emitter voltage of a transistor from a zener voltage of a zener diode and dividing it by a resistance of an emitter resistor. For example, in cases that the zener voltage is 17V, that the base-emitter voltage 2V, and that the resistance is 50 ohm, the constant current is 0.3A.
If capacitor
7
is not charged for the case of being out of order, the voltage of capacitor
7
is 0V, and the supply voltage of switching power supply
9
connected in parallel with capacitor
7
is also 0V. In that case, switching power supply
9
is not in operation, and the control unit
10
receiving a power from switching power supply
9
is not in operation, either. Accordingly, control unit
10
cannot check the circuit, communicate with air controller
12
, or receive the signal from the sensor before capacitor
7
is charged. The conventional conditioner in
FIG. 14
involves no problems because the control unit
10
is always in operation. The conditioner in
FIG. 15
has a similar problem even in case charge resistor
5
is provided in place of constant-current charging circuit
15
.
While motor-driven compressor
14
is not in operation, capacitor
7
is preferably discharged for energy saving and operation time shortening in order to enhance the lifetime of the conditioner. However, if capacitor
7
is discharged, the control unit
10
does not operate as described above. In the conditioner shown in
FIG. 14
, the capacitor
7
is discharged with opening breaker
3
, but there arises no problem because the control unit
10
is always in operation.
If capacitor
7
is discharged while motor-driven compressor
14
is not in operation, the capacitor
7
needs to be charged before start operating the motor-driven compressor
14
, thus requiring time for motor-driven compressor
14
to start operating. This problem is common to the conditioner in FIG.
14
.
SUMMARY OF THE INVENTION
In an air conditioner having a control unit receiving a power from a switching power supply, a supplied voltage for the control unit is reduced to a possible lowest voltage for the unit to operate. This arrangement provides the conditioner with less electromagnetic wave noise of the switching power supply, with a quick check and repair, and with having a motor-driven compressor start quickly. The air conditioner includes: a power application device connected in series to a direct-current (DC) power source; a switch device connected in parallel with the power application device; a capacitor charged by the DC power source via the power application device; a voltage detector for detecting a voltage of the capacitor; an output unit for driving a motor-driven compressor for air conditioning, the output unit receiving a power from the DC power source via the switch device; a control unit for controlling the output unit; a power supply connected in parallel with the capacitor, for supplying a power to the control unit, the power supply receiving a power from the DC power source; and a voltage lowering device for, when the motor-driven compressor does not operate, setting the voltage of the capacitor to a voltage which is lower than a voltage of the DC power source and which allows the control unit to operate. The voltage lowering device being controlled by the controller.
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Goto Naomi
Kurahashi Yasufumi
Nishii Nobuyuki
Martin Edgardo San
Matsushita Electric - Industrial Co., Ltd.
Nappi Robert E.
RatnerPrestia
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