US 6,636,079 B2 · Phase comparing circuit, PLL circuit, televisions broadcasting receiver, and method of comparing phase

Abstract

An object of the present invention is to provide a phase comparing circuit capable of outputting a signal in accordance with phase difference with a high degree of accuracy, even if the phase difference is small. The phase comparing circuit according to the present invention has a feed forward circuit connected between a frequency phase comparator and a charge pump. The feed forward circuit has a capacitor connected between each Q output terminal of flip-flops in the frequency phase comparator and the current path of the charge pump circuit. The capacitor couples capacitively the Q output terminals of the D flip-flops with the current path of the charge pump circuit, in order to quickly provide the Q output voltages of the D flip-flops to the charge pump circuit. Accordingly, even when the phase difference of the input signals FS and FR is small, the voltage in accordance with the phase difference is provided to a collector terminal of a transistor in the charge pump circuit, thereby controlling the current passing through the charge pump circuit with a high degree of accuracy in accordance with the phase difference.

Claims19

Dependent claims

A phase comparing circuit, comprising:

a phase comparator configured to detect phase difference between first and second input signals;
a charge pump circuit configured to output a signal in accordance with said detected phase difference;
and
a feed forward circuit connected between said phase comparator and a first signal transmission path in said charge pump circuit, said feed forward circuit being configured to provide the signal in accordance with said phase difference to said charge pump circuit;
wherein said phase comparator includes:
a second signal transmission path which outputs a signal in sync with said first input signal;
and
a third signal transmission path which outputs a signal in sync with said second input signal,
wherein said feed forward circuit includes:
a first capacitor having a first end connected to said second signal transmission path, and a second end connected to said first signal transmission path;
and
a second capacitor having a first end connected to said third signal transmission path, and a second end connected to said first signal transmission path.

9 more elements

A phase comparing circuit, comprising:

a phase comparator configured to detect phase difference between first and second input signals;
a charge pump circuit configured to output a signal in accordance with said detected phase difference;
and
a feed forward circuit connected between said phase comparator and a signal transmission path in said charge pump circuit, said feed forward circuit being configured to provide the signal in accordance with said phase difference to said charge pump circuit;
wherein said feed forward circuit provides the signal in accordance with said phase difference to said charge pump circuit by capacity coupling between a node in said phase comparator and the signal transmission path in said charge pump circuit, and
wherein said phase comparator includes:
a first flip-flop configured to output a signal in sync with a rising edge or a falling edge of said first input signal, and
a second flip-flop configured to output a signal in sync with a rising edge or a falling edge of said second input signal, and
wherein said feed forward circuit includes:
a first capacitor connected between an output terminal of said first flip-flop and the signal transmission path in said charge pump circuit, and
a second capacitor connected between an output terminal of said second flip-flop and the signal transmission path in said charge pump circuit.

8 more elements

A PLL circuit, comprising:

a phase comparing circuit includes:
a phase comparator configured to detect phase difference between first and second input signals, a charge pump circuit configured to output a signal in accordance with said detected phase difference, and a feed forward circuit connected between said phase comparator and a signal transmission path in said charge pump circuit, said feed forward circuit being configured to provide a signal in accordance with said phase difference to said charge pump circuit;
a voltage control oscillator configured to control oscillating frequency based on the output of said phase comparing circuit;
and
a divider configured to provide a signal obtained by dividing the output frequency of said voltage control oscillator to said phase comparing circuit,
wherein said feed forward circuit provides the signal in accordance with said phase difference to said charge pump circuit by capacity coupling between a node in said phase comparator and the signal transmission path in said charge pump circuit, and
wherein said phase comparator includes:
a first flip-flop configured to output a signal in sync with a rising edge or a falling edge of said first input signal, and
a second flip-flop configured to output a signal in sync with a rising edge or a falling edge of said second input signal,
and wherein said feed forward circuit includes:
a first capacitor connected between an output terminal of said first flip-flop and the signal transmission path in said charge pump circuit, and
a second capacitor connected between an output terminal of said second flip-flop and the signal transmission path in said charge pump circuit.

9 more elements

Dependencies are inferred from the claim text.

Phase comparing circuit, PLL circuit, televisions broadcasting receiver, and method of comparing phase

Life of this patent

Phase comparing circuit, PLL circuit, televisions broadcasting receiver, and method of comparing phase

Life of this patent

Abstract

Claims19