Air conditioner with defrosting operation and method for controlling the same

A method of controlling an air conditioner including a first four-way valve arranged between a discharge port of a compressor and an upper inlet of an outdoor heat exchanger, and a second four-way valve arranged between the discharge port of the compressor and a lower inlet of the outdoor heat exchanger, the method comprising:

• controlling the first four-way valve and the second four-way valve to perform a first defrosting operation to defrost an upper portion of the outdoor heat exchanger and a lower portion of the outdoor heat exchanger during a heating operation;
• determining whether to perform a second defrosting operation to additionally defrost the lower portion of the outdoor heat exchanger based on termination of the first defrosting operation;
• and
• controlling the first four-way valve and the second four-way valve so that the upper portion of the outdoor heat exchanger operates as an evaporator, and the lower portion of the outdoor heat exchanger operates as a condenser, in the second defrosting operation,
• wherein determining whether to perform a second defrosting operation includes performing a second defrosting operation which defrosts the lower portion based on a need for additional defrosting of the lower portion being detected, and
• wherein detecting the need for additional defrosting of the lower portion includes detecting a preset compressor protection condition including at least one of inflow of a liquid refrigerant to the compressor, a current supplied to the compressor exceeding a reference current, or temperature at the discharge port of the compressor exceeding a reference temperature.

An air conditioner comprising:

• a compressor configured to compress a refrigerant, and including a discharge port;
• an outdoor heat exchanger configured to exchange heat with outside air, and including:
• an upper portion,
• an upper inlet,
• a lower portion, and
• a lower inlet;
• a first four-way valve arranged between the discharge port of the compressor and the upper inlet;
• a second four-way valve arranged between the discharge port of the compressor and the lower inlet;
• and
• a controller electrically connected to the compressor, the first four-way valve and the second four-way valve,
• wherein the controller is configured to:
• control the first four-way valve so that refrigerant from the first four-way valve flows to the upper inlet, and control the second four-way valve so that refrigerant from the second four-way valve flows to the lower inlet, to perform a first defrosting operation which defrosts the upper portion and the lower portion during a heating operation, and
• control the first four-way valve to discharge refrigerant from the upper inlet, and control the second four-way valve so that the refrigerant from the second four-way valve flows to the lower inlet, to perform a second defrosting operation which defrosts the lower portion, based on a need for additional defrosting of the lower portion,
• wherein detecting the need for additional defrosting of the lower portion includes detecting a preset compressor protection condition including at least one of inflow of a liquid refrigerant to the compressor, a current supplied to the compressor exceeding a reference current, or temperature at the discharge port of the compressor exceeding a reference temperature.