Refrigerator having variable speed compressor and control method thereof

A refrigerator comprising:

• a brushless direct current (BLDC) compressor comprising a motor;
• a thermostat configured to transmit an electrical signal according to an internal temperature of a storage chamber;
• an inverter controller comprising a plurality of switching elements and configured to operate the BLDC compressor at a specified speed according to the electrical signal transmitted from the thermostat, wherein the specified speed is less than a maximum speed;
• and
• a speed controller configured to transmit an output voltage to the inverter controller and control a duty ratio of the output voltage,
• wherein the inverter controller is configured to calculate power consumption of the BLDC compressor using a voltage applied to a winding of the motor in the BLDC compressor and a current flowing in the winding of the motor during operation of the BLDC compressor at the specified speed, and control an operation speed of the BLDC compressor by estimating the internal temperature based on the calculated power consumption,
• wherein the inverter controller is configured to control the operation speed by operating the switching elements to operate the motor,
• wherein the inverter controller is configured to operate the switching elements based on the duty ratio, so that the switching elements operate at a switching frequency period corresponding to the duty ratio, and
• wherein the speed controller is configured to execute a speed control at an execution period, which is the same as the switching frequency period, so that the speed control and operation of the switching elements are synchronized.

A method of controlling a refrigerator including a housing having a storage chamber formed therein, a thermostat configured to operate according to an internal temperature of the storage chamber, a compressor comprising a motor and configured to be operated according to operation of the thermostat, and an inverter controller comprising a plurality of switching elements, the method comprising:

• calculating power consumption of the compressor by detecting a voltage applied to a winding of the motor in the compressor and a current flowing in the winding of the motor;
• comparing the calculated power consumption with reference power, and increasing an operation speed of the compressor when the power consumption is equal to or higher than the reference power;
• operating the compressor at a specified speed that is less than a maximum speed when the power consumption is less than the reference power;
• and
• performing speed control according to an output voltage, to control the switching elements to operate at a switching frequency period corresponding to a duty ratio of the output voltage so as to operate the motor, thereby changing the operation speed of the compressor,
• wherein the speed control is executed at an execution period, which is the same as the switching frequency period, so that the speed control and operation of the switching elements are synchronized.