We Claim:
1. A driving device to drive a motor having coils, the driving
device comprising:
a connection switching unit to switch a connection state of
the coils;
a temperature sensor to detect a room temperature; and
a controller to switch a connection state of the coils based
on a detected temperature by the temperature sensor.
2. The driving device according to claim 1, wherein the controller stops rotation of the motor before the connection state of the coils is switched.
3. The driving device according to claim 1 or 2, wherein the connection state of the coils has a first connection state and a second connection state in which a line voltage is lower than a line voltage in the first connection state.
4. The driving device according to claim 3, wherein if an absolute value of a difference between a detected temperature by the temperature sensor and a set temperature is larger than a threshold, the controller switches the connection state of the coils to the second connection state.
5. The driving device according to claim 3 or 4, wherein if an absolute value of a difference between a detected temperature by the temperature sensor and a set temperature is less than or equal to a threshold, the controller switches the connection state of the coils to the first connection state.
6. The driving device according to any one of claims 3 to 5, wherein the coils are three-phase coils, and
wherein the first connection state is a state where the

three-phase coils are connected in a Y connection, and the second connection state is a state where the three-phase coils are connected in a delta connection.
7. The driving device according to any one of claims 3 to 5,
wherein the coils are three-phase coils connected in a Y
connection or a delta connection,
wherein the first connection state is a state where the three-phase coils are connected in series for each phase, and
wherein the second connection state is a state where the three-phase coils are connected in parallel for each phase.
8. The driving device according to any one of claims 1 to 7, wherein if an absolute value of a difference between a detected temperature by the temperature sensor and a set temperature is less than or equal to a threshold, the controller compares a rotation speed of the motor to a reference value, and the controller switches the connection state of the coils based on a result of comparison.
9. The driving device according to any one of claims 1 to 8, further comprising a converter to generate a bus voltage, and an inverter to convert the bus voltage to an AC voltage and supply the AC voltage to the coils,
wherein the converter changes a level of the bus voltage in accordance with switching of the connection state of the coils by the connection switching unit.
10. The driving device according to claim 9, wherein if an
absolute value of a difference between a detected temperature by
the temperature sensor and a set temperature is less than or equal
to a threshold, the controller compares an output voltage of the
inverter to a reference value, and the controller switches the
connection state of the coils based on a result of comparison.

11. The driving device according to claim 9 or 10, wherein the inverter performs field-weakening control in accordance with a rotation speed of the motor.
12. The driving device according to any one of claims 1 to 11, wherein the controller stops the motor to avoid overcooling or overheating based on a difference between a detected temperature by the temperature sensor and a set temperature, and then causes the connection switching unit to switch the connection state of the coils.
13. The driving device according to any one of claims 1 to 12, wherein the controller switches the connection state of the coils based on a load calculated from a difference between a detected temperature by the temperature sensor and a set temperature.
14. The driving device according to any one of claims 1 to 13, wherein the connection switching unit has a relay contact.
15. An air conditioner comprising:
a motor having coils;
a compressor driven by the motor; and
a driving device to drive the motor,
wherein the driving device comprises:
a connection switching unit to switch a connection state of the coils,
a temperature sensor to detect a temperature of a target space, and
a controller to switch a connection state of the coils based on a detected temperature by the temperature sensor.
16. A method for driving a motor having coils, the method
comprising:

a temperature detection step of detecting a room temperature; and
a connection switching step of switching a connection state of the coils based on a detected temperature detected in the temperature detection step.