System and method for controlling speed of motor

A method for controlling a speed of a motor by a system for controlling a speed of a motor including a speed measuring unit, a comparison unit, a speed control unit, a limiting unit, a duty control unit, a phase control unit, and a motor driving unit, the method comprising:

• a) receiving, by the speed measuring unit, a signal from a hall sensor mounted in the motor to measure a current speed of the motor;
• b) comparing, by a comparison unit, the current speed of the motor measured by the speed measurement unit with a reference speed to calculate errors;
• c) outputting, by the speed control unit, a speed control value of the motor based on the errors calculated by the comparison unit;
• d) limiting, by the limiting unit, the speed control value output from the speed control unit to values within a predetermined range;
• e) controlling, by the duty control unit, a duty of current applied to the motor according to the values within the predetermined range limited by the limiting unit;
• f) controlling, by the phase control unit, the phase of current applied to the motor according to the values within the predetermined range limited by the limiting unit;
• and
• g) generating, by a motor driving unit, a motor driving signal based on the duty control by the duty control unit and the phase control by the phase control unit and applying the generated motor driving signal to the motor.