JPS59200528A - Detection system for phase-unlocked state of phase-locked loop - Google Patents

Abstract

PURPOSE:To remove unstableness from phase-unlocked state detecting operation by generating pulse signals from an original signal and a feedback signal respectively, and detecting the crossing of those two pulse signals. CONSTITUTION:An input signal [original signal (a)] and the feedback signal (b) to the phase comparing circuit 1 of a phase-locked loop are inputted to a pulse generating circuit 6 respectively. The circuit 6 generates pulse signals (f) and (g) from the original signal (a) and feedback signal (b). The signals (f) and (g) are controlled in relative phase relation while the phase-locked loop is in a phase- locked state, so a pulse crossing detecting circuit 7 detects no crossing of the signals (f) and (g). When the phase-locked loop enters the phase-unlocked state, the relative phase relation between the signals (f) and (g) is not maintained any more and varies continuously in either direction, and the circuit 7 detects the crossing of the signals (f) and (g) synchronously to send a pulse crossing detection signal (h) to an unlocked-state detection output circuit 8, which outputs a phase-unlocked state detection output signal (e).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an asynchronous state detection method in a phase-locked loop.

The configuration of a conventional method for detecting an asynchronous state of a phase-locked loop is shown in FIG. In FIG. 1, ■ indicates a phase comparison circuit, 2 indicates a loop filter circuit, 3 indicates a voltage controlled oscillation circuit, 4 indicates an asynchronous state detection comparison circuit, and 5 indicates an asynchronous state detection output circuit.

Conventionally, in order to detect an asynchronous state in a phase-locked loop, the output of the phase comparison circuit in the phase-locked loop is passed through the next-stage loop filter circuit, and the DC output level of the loop filter circuit is determined beforehand by the comparison circuit. This has been implemented by determining whether the phase-locked loop is in a synchronous state or an asynchronous state based on whether the darkness value is within a set range.

In such an asynchronous state detection method, since the DC output level of the loop filter circuit and the set threshold of the comparison circuit provided in the subsequent stage are used as the judgment criteria, deviations in the components of the loop filter circuit and the comparison circuit in the subsequent stage are used as the determination criteria. ,
Due to characteristics, etc., the DC output level and the threshold value set in the comparator circuit deviate from each other, making it impossible to obtain a stable detection operation and requiring readjustment.

An object of the present invention is to eliminate the above-mentioned drawbacks by eliminating the use of the DC output level of the loop filter circuit and the judgment level of the threshold value set by the comparator circuit, and instead of using the signal input to the phase-locked loop (hereinafter referred to as the original signal). By generating pulse signals from the signal (hereinafter referred to as the feedback signal) and the signal fed back to the phase-locked circuit of the phase-locked loop (hereinafter referred to as the feedback signal), and detecting the intersection of these two pulse signals using a logic circuit, It is an object of the present invention to provide a simple asynchronous state detection method for a phase-locked loop that makes it possible to eliminate instability in the asynchronous state detection operation caused by deviations and characteristics of circuit components.

To achieve the above object, the present invention provides a pulse generation circuit for generating pulse signals from an original signal and a feedback signal, respectively, and a pulse crossing circuit for detecting the intersection of two pulse signals generated by the pulse generation circuit. An output circuit configured to output a detection signal of an asynchronous state of the phase-locked loop using an output signal outputted from the detection circuit and the pulse crossing detection circuit by detecting the crossing of the two pulse signals. be done.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of a basic phase-locked loop and a conventional asynchronous detection method, and FIG. 2 is a configuration diagram of a -w-based phase-locked loop and an asynchronous detection method according to the present invention. This is an example. Further, FIGS. 3 and 4 show signal waveforms for explaining the principle of asynchronous detection in the present invention, with FIG. 3 showing a synchronous state and FIG. 4 showing an asynchronous state.

In FIG. 2, the input signal (original signal A) to the phase comparison circuit 1 of the phase-locked loop and the feedback signal port are respectively input to the pulse generation circuit 6. The pulse generation circuit 6 includes the above-mentioned
Pulse signals G and H are generated from the original signal A and the feedback signal port, respectively. These two pulse signals G and H are
When the phase-locked loop is in a synchronous state, as shown in FIG. The intersection of G and G is not detected.

On the other hand, when the phase-locked loop becomes asynchronous, the stability of the relative phase relationship between the pulse signals T and C from the pulse generation circuit 6 as shown in FIG. As shown in the figure, the relative phase relationship changes continuously in either direction indicated by the arrow. Therefore, the pulse crossing detection circuit 7 provided at the subsequent stage periodically detects the crossing of the pulse signals G and Q derived from the input signals (original signal A and the feedback signal port), and the asynchronous state detection output circuit 8 Then, upon receiving the pulse crossing detection signal,
It outputs an asynchronous state detection output signal indicating that the phase synchronization loose is in an asynchronous state, or displays the detected state.

FIG. 3 shows that in the embodiment of FIG. 2, the relative phase relationship of the pulse signals T and T in the synchronous state is maintained as shown in FIG. 3, and FIG. indicates that in the embodiment of FIG. 2, when in an asynchronous state, the relative phase relationship of the pulse signals G and C continuously deviates in either direction shown by the arrow in FIG. It is something that

As explained above, the present invention is based on the original signal and feedback signal input to the phase comparison circuit of phase locked loop = 5-.
The method of generating pulse signals individually and detecting and processing the intersection of both pulse signals using a logic circuit eliminates the instability of detection operation caused by deviations and characteristics of circuit components inherent in conventional asynchronous detection methods. This has the effect of eliminating the need for readjustment of the device for improving the instability.

[Brief explanation of the drawing]

Fig. m1 is a block diagram of a basic phase-locked loop and a conventional asynchronous state detection method, Fig. 2 is a block diagram showing an embodiment of the present invention, and Figs. 3 and 4 show the embodiment of Fig. 2. This is a diagram for illustration purposes only. DESCRIPTION OF SYMBOLS 1... Phase comparison (b) path, 2... Loop filter circuit, 3... Voltage controlled oscillation circuit, 4
...Comparison circuit for detecting asynchronous state, 5...
- Asynchronous state detection output circuit 6...Pulse generation circuit, 7...Pulse crossing detection circuit, 8...
・Asynchronous state detection output circuit, A: Phase-locked loop input signal (original signal), A: Phase-locked loop output signal (feedback signal), No: Phase error signal 6 No. 1, 2... Voltage controlled oscillation circuit control signal, E...
...Asynchronous state detection signal, G...Asynchronous state detection output signal, T...Pulse signal generated from the original signal A, CH...Generated from the feedback signal port Pulse signal,...Pulse crossing detection signal,...
...Asynchronous state detection output signal. Kanl Senryo Ward 3

Claims (1)

[Claims] In detecting an asynchronous state in a phase-locked loop, pulse signals are generated from the input signal to the phase-locked loop and the feedback signal to the phase comparison circuit, respectively, and the asynchronous state of the phase-locked loop is detected by detecting the intersection of both pulses. A phase-locked loop asynchronous state detection method characterized by: