Disclosed are a method and a system for feedback-controlling including controlling a current supply unit in a controller so that an output applied to a driving unit from the current supply unit is repeatedly turned on/off by predetermined period and duty. The method also includes feedback-controlling of an output value of the controller applied to the current supply unit from the controller so that the output of the current supply unit follows a target value. The feedback-controlling includes an integration control process and stops the integration control process in the period that the current supply unit turns off the output thereof.