Phase adjustment circuit including a ring oscillator in a phase locked loop
First Claim
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1. A phase adjustment circuit, comprising:
- a voltage controlled oscillation circuit provided with serially connected n number of stages (n is a positive integer) of variable delay circuits and performing negative feedback of the output of the final stage variable delay circuit to the input of the initial stage variable delay circuit;
a phase locked loop means for comparing phases of the output of the voltage controlled oscillation circuit and a clock supplied from an external unit, outputting a delay control signal to control the delay time in each stage of variable delay circuit of the voltage controlled oscillation circuit, and locking the phase;
a control signal generation circuit which outputs k (k is an integer of at least
3) number of weighting coefficient signals based on a phase control signal supplied from an external unit and interpolates the middle section so that the maximum number of weighting coefficient signals are given at substantially equal intervals with respect to the phase control signal and so that the sum of the weighting coefficients is substantially constant; and
a weighting means for weighting each of k number of signals of substantially equal phase differences taken out from the stages of the variable delay circuits in the voltage controlled oscillation circuit with a respective one of the k number of weighting coefficient signals output by the control signal generation circuit and outputting the result as the output signal of the phase adjustment circuit.
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Abstract
A phase adjustment circuit includes a ring oscillator which is phase locked to an external pixel clock by a phase locked loop. The ring oscillator is formed of n number of stages of variable delay circuits providing n+1 outputs of substantially equal phase differences. A control signal generation circuit is responsive to a phase control signal to generate n+1 weighting coefficients for weighting the n+1 outputs from the ring oscillator in a weighting circuit which produces a phase adjusted output signal.
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5 Claims
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1. A phase adjustment circuit, comprising:
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a voltage controlled oscillation circuit provided with serially connected n number of stages (n is a positive integer) of variable delay circuits and performing negative feedback of the output of the final stage variable delay circuit to the input of the initial stage variable delay circuit; a phase locked loop means for comparing phases of the output of the voltage controlled oscillation circuit and a clock supplied from an external unit, outputting a delay control signal to control the delay time in each stage of variable delay circuit of the voltage controlled oscillation circuit, and locking the phase; a control signal generation circuit which outputs k (k is an integer of at least
3) number of weighting coefficient signals based on a phase control signal supplied from an external unit and interpolates the middle section so that the maximum number of weighting coefficient signals are given at substantially equal intervals with respect to the phase control signal and so that the sum of the weighting coefficients is substantially constant; anda weighting means for weighting each of k number of signals of substantially equal phase differences taken out from the stages of the variable delay circuits in the voltage controlled oscillation circuit with a respective one of the k number of weighting coefficient signals output by the control signal generation circuit and outputting the result as the output signal of the phase adjustment circuit. - View Dependent Claims (2, 3, 4, 5)
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Specification