Patent ID: 7675328

Claim:
A phase detection apparatus comprising: a phase-difference detection unit that includes: a first variable delay device that delays a phase of a first clock by a variable amount, a first logic gate that detects a phase difference between the first clock delayed by the first variable delay device and a second clock, and outputs a first signal of a pulse width corresponding to the phase difference detected, a second variable delay device that delays a phase of the second clock by a variable amount, and a second logic gate that detects a phase difference between the second clock delayed by the second variable delay device and the first clock, and outputs a second signal of a pulse width corresponding to the phase difference detected; and a feedback circuit that includes: a third variable delay device that delays the phase of the first clock by a variable amount, a third logic gate that detects a phase difference between the first clock delayed by the third variable delay device and the first clock, and outputs a third signal of a pulse width corresponding to the phase difference detected, and a smoothing unit that outputs an integral of the pulse width of the third signal as a control signal indicative of an amount of delay, the control signal being fed back to the third variable delay device and input to the first and the second variable delay devices, wherein the feedback circuit is arranged independent of the phase-difference detection unit.