Patent ID: 7348871
Filing Date: 2008-03-25
Classification: H01F,H01L

Abstract:
1. An inductance variable device comprising: a first inductor; a second inductor magnetically coupled to the first inductor; a current source whose current is variable, electrically connected to the first inductor; and a current control unit which controls a current flowing from the current source to the first inductor according to a feedback signal having frequency information in a current flowing in the second inductor to vary a combined inductance of the second inductor, wherein the current control unit comprises: a frequency divider for dividing a frequency of the feedback signal to a predetermined frequency; a phase detector for comparing a phase of the frequency divided signal with a phase of a reference signal having predetermined frequency information; and a charge pump for outputting a voltage to the current source according to an input from the phase detector, and wherein the current control unit adjusts a current value to be applied to the first inductor according to an input signal from the charge pump.