JP2009284196A - Oscillation circuit, electronic device provided with oscillation circuit and control method of oscillation circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption by turning phase synchronization between high precision oscillators to an intermittent operation. <P>SOLUTION: The oscillation circuit 1 includes: the high precision oscillator 100 of high frequency accuracy for outputting the reference signals Fref of a frequency to be a reference; a voltage controlled oscillator 110 for controlling the frequency of output signals Fout by a control voltage Vc; a phase comparison part 120 for detecting a phase difference between the phase of the reference signals Fref and the phase of the output signals Fout and outputting phase difference signals Po; a control voltage generation part 130 for generating the control voltage Vc on the basis of the phase difference signals Po; a switch circuit 140 for switching the connection of a power source VDD to the phase comparison part 120 to a connection state or a non-connection state; and a timer circuit 150 for outputting control signals Sw for turning the switch circuit 140 to the connection state in a period until prescribed time elapses from the point of time at which there is no more phase difference on the basis of the phase difference signals Po and turning the switch circuit 140 to the non-connection state at the time other than the period. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an oscillation circuit that outputs a highly accurate signal, an electronic device including the oscillation circuit, and a method for controlling the oscillation circuit.

  In general, phase-locked control is performed by phase-locking a highly accurate reference oscillator and a relatively unstable oscillator that is dependent on the accuracy, so that the output of the latter oscillator prepared at an arbitrary frequency is a highly accurate reference. This is a technique for obtaining the same level of stability as an oscillator. The former uses an atomic oscillator, an oven controlled oscillator (OCXO) or a reference signal supplied by wire or wireless, and the latter uses a voltage controlled crystal oscillator (VCXO) or LC. An oscillator or the like is used.

  On the other hand, phase synchronization control of atomic oscillators is sometimes performed in wide-area infrastructure such as communication networks and broadcasting systems, but phase synchronization control detects and corrects the phase difference between the output signals of atomic oscillators. Therefore, when the stability of both is extremely high, a certain time elapses to generate a detectable phase difference.

  In order to solve this problem, for example, Patent Document 1 describes a method of ensuring frequency accuracy during non-operation by performing synchronization control corresponding to wireless intermittent reception.

Special table 2007-528642 gazette

  However, the conventional method is useful for ensuring constant signal synchronization between devices in high-speed digital communications, etc., but the frequency accuracy of the reference oscillator can be kept constant, or a high-accuracy clock can be used on a monthly or yearly basis. However, in order to maintain a certain frequency accuracy, excessive control is required, and there is a problem that it is not suitable for small devices that require low power consumption. In other words, if the conventional method is used, the instantaneous frequency and phase accuracy can be maintained, and a frequency signal with little change in the long term can be obtained as an extension, but for the frequency after one year, for example, it is represented by frequency fluctuation. Even if there is a short-term fluctuation, the fluctuation on the positive side and the fluctuation on the negative side are offset, so it can be said that it is over-controlled when considered in the long term.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
A high-precision oscillator that outputs a reference signal of a reference frequency with high frequency accuracy, a voltage-controlled oscillator that controls the frequency of the output signal with a control voltage, and a phase difference between the phase of the reference signal and the phase of the output signal A phase comparison unit that detects and outputs a phase difference signal; a control voltage generation unit that generates the control voltage based on the phase difference signal; and a switch that switches connection of a power source to the phase comparison unit between a connected state and a disconnected state The switch circuit is set in the connected state during a period until a predetermined time elapses after the phase difference disappears based on the circuit and the phase difference signal, and the switch circuit is set in the non-connected state during other periods. An oscillation circuit comprising: a timer circuit that outputs a control signal;

  According to this configuration, since the phase of the reference signal and the phase of the output signal are synchronized until the predetermined time elapses, the power supply to the phase comparison unit can be disconnected. Power consumption can be reduced.

[Application Example 2]
In the oscillation circuit described above, the predetermined time is set to be equal to or less than a time obtained by dividing a half cycle of the voltage controlled oscillator by a phase difference generated every cycle of the voltage controlled oscillator. Oscillator circuit to perform.

  According to this configuration, the output signal is output with respect to the reference signal by setting the phase difference that can occur in the voltage controlled oscillator within a predetermined period during the predetermined time when the power supply to the phase comparison unit is disconnected. Since it can be determined that there is a delay, the voltage controlled oscillator can be reliably controlled.

[Application Example 3]
In the oscillation circuit described above, the timer circuit measures an elapsed time from the time when the phase difference disappears to the next time when the phase difference is detected based on the phase difference signal, and based on the elapsed time. An oscillation circuit characterized in that the predetermined time is set.

  According to this configuration, it is possible to determine the predetermined time by measuring the elapsed time from when the phase difference disappears until the phase difference is detected again. realizable.

[Application Example 4]
In the oscillation circuit described above, the oscillation circuit sets the predetermined time short when operating with high accuracy, and sets the predetermined time long when operating with low accuracy. circuit.

  According to this configuration, the phase difference detection capability can be enhanced by setting the predetermined time short when operating with high accuracy, and the time can be reduced by setting the predetermined time long when operating with low accuracy. Power consumption can be reduced.

[Application Example 5]
An electronic device comprising the oscillation circuit described above.

  According to this configuration, since the phase of the reference signal and the phase of the output signal are synchronized until the predetermined time elapses, the power supply to the phase comparison unit can be disconnected. An electronic device capable of reducing power consumption can be provided.

[Application Example 6]
A high-precision oscillator that outputs a reference signal of a reference frequency with high frequency accuracy, a voltage-controlled oscillator that controls the frequency of the output signal with a control voltage, and a phase difference between the phase of the reference signal and the phase of the output signal A method for controlling an oscillation circuit, comprising: a phase comparison unit that detects and outputs a phase difference signal; and a control voltage generation unit that generates the control voltage based on the phase difference signal. Switch for connecting the power supply to the phase comparison unit during the period from when the phase difference disappears until a predetermined time elapses, and for disconnecting the power supply connection to the phase comparison unit during the period other than the period A method of controlling an oscillation circuit, comprising a step.

  According to this configuration, since the phase of the reference signal and the phase of the output signal are synchronized until the predetermined time elapses, the power supply to the phase comparison unit can be disconnected. Power consumption can be reduced.

  Hereinafter, embodiments of the oscillation circuit will be described with reference to the drawings.

(First embodiment)
<Configuration of oscillation circuit>
First, the configuration of the oscillation circuit according to the first embodiment will be described with reference to FIG. FIG. 1 is a circuit diagram showing a configuration of an oscillation circuit according to the first embodiment.

  As shown in FIG. 1, an oscillation circuit 1 includes an atomic oscillator 100 that is a high-precision oscillator, a voltage controlled oscillator (VCO) 110, a phase comparison unit 120, a control voltage generation unit 130, and a switch circuit. 140 and a timer circuit 150. Note that the VCO 110 includes a highly accurate and voltage-controllable atomic oscillator, a crystal oscillator (VCXO), and the like.

  The phase comparison unit 120 outputs a frequency division signal Fr obtained by dividing the frequency of the reference signal Fref output from the atomic oscillator 100 by 1 / R (R is an arbitrary integer), and the VCO 110 outputs The 1 / N frequency divider 122 that outputs a frequency-divided signal Fn obtained by dividing the frequency of the output signal Fout to be 1 / N (N is an arbitrary integer), and the phase difference between the frequency-divided signal Fr and the frequency-divided signal Fn. And a phase comparator 123 that compares and outputs a phase difference signal Po. For example, if the frequency of the reference signal Fref is 10 MHz and the frequency of the output signal Fout is 500 MHz, the 1 / R divider 121 is not necessary if the frequency division of the 1 / N divider 122 is set to N = 50.

  The control voltage generator 130 includes a digital-analog converter (DAC) 131 for converting to analog data Pa when the phase difference signal Po output from the phase comparator 123 is digital data, and analog data Pa. And a low pass filter (LPF) 132 that outputs a control voltage Vc through which only a low frequency is passed.

  The switch circuit 140 switches the connection of the power supply VDD to the phase comparison unit 120 between a connected state and a disconnected state.

The timer circuit 150 outputs a control signal Sw = H level that keeps the switch circuit 140 connected during a period from when the phase difference disappears based on the phase difference signal Po until a predetermined time elapses, and other periods. Outputs a control signal Sw = L level that switches the switch circuit 140 to a disconnected state. The predetermined time can be set as a time until the number of rising times of the output signal Fout is counted and the number of rising times becomes n (n is an arbitrary integer). The value of n can be rewritten from the outside in a register (not shown) of the timer circuit 150 and can be set in advance. For example, if the period from the rising edge of the output signal Fout to the next rising edge is Ck, the predetermined time is Ck × n. Note that the value of n is set to a value obtained by dividing the half cycle of the VCO 110 by the phase difference generated for each cycle of the VCO 110. For example, if the half cycle of the VCO 110 is 0.05 seconds and the phase difference generated every cycle of the VCO 110 is 1 × 10 ⁻⁶ seconds, then n = 0.05 ÷ 1 × 10 ⁻⁶ = 5000.

<Operation of oscillation circuit>
Next, the operation of the oscillation circuit will be described with reference to FIGS. FIG. 2 is a flowchart showing the operation of the oscillation circuit. FIG. 3 is a timing chart showing the operation of the oscillation circuit. Note that the timing diagram of FIG. 3 exemplifies a case where the frequency-divided signal Fn changes extremely to simplify the description. In the actual VCO 110, the frequency-divided signal Fn changes gently and monotonously.

  First, in step S100 of FIG. 2, the timer circuit 150 sets the control signal Sw to the H level. For example, since the control signal Sw is set to the H level at the time t1 in FIG. 3, the switch circuit 140 is connected, the power supply VDD is supplied to the phase comparison unit 120, and the phase comparison unit 120 is turned on. Since the phase comparator 120 is turned on, the phase comparator 123 outputs a phase difference signal Po obtained by comparing the phase difference between the frequency-divided signal Fr and the frequency-divided signal Fn to the timer circuit 150.

  Next, in step S102, the phase difference signal Po at the next time point is read, and the process proceeds to step S104.

  Next, in step S104, it is determined whether or not the read phase difference signal Po is at H level. If it is at H level, the process proceeds to step S106, and if not, the process proceeds to step S102. For example, in FIG. 3, since the phase difference signal Po read at time t2 is L level, the process proceeds to step S102, and since the phase difference signal Po read at time t3 is H level, the process proceeds to step S106.

  Next, in step S106, the phase difference signal Po at the next time point is read, and the process proceeds to step S108.

  Next, in step S108, it is determined whether or not the read phase difference signal Po is at the L level. If it is at the L level, the process proceeds to step S110, and if not, the process proceeds to step S106. For example, in FIG. 3, since the phase difference signal Po read at time t4 is at the H level, the process proceeds to step S106, and since the phase difference signal Po read at time t5 is at the L level, the process proceeds to step S110.

  Next, in step S110, the timer circuit 150 sets the control signal Sw to the L level. For example, since the control signal Sw is set to the L level at time t5 in FIG. 3, the switch circuit 140 is disconnected, the supply of the power supply VDD to the phase comparison unit 120 is cut off, and the phase comparison unit 120 is turned off. Become. Since the phase comparison unit 120 is in the OFF state, the phase difference signal Po maintains the L level.

  Next, in step S112, the timer circuit 150 sets the value Count of the internal counter to 0, and proceeds to step S114.

  Next, in step S114, the timer circuit 150 adds 1 to the value Count of the internal counter at the next time point, and proceeds to step S116.

  Next, in step S116, the timer circuit 150 determines whether the value Count of the internal counter is n times or more. If it is n times or more, the process proceeds to step S100. If it is less than n times, the process proceeds to step S114. To do. For example, in FIG. 3, since the internal counter value Count = 1 at time t6, the process proceeds to step S114. At time t7, the internal counter value Count = n is reached, so the process proceeds to step S100.

  According to the present embodiment described above, the following effects can be obtained.

  In this embodiment, the power supply to the phase comparison unit can be disconnected during a period from when the phase of the reference signal and the phase of the output signal are synchronized until a predetermined time elapses. Electricity can be achieved.

  Although the embodiments of the oscillation circuit have been described above, the present invention is not limited to these embodiments, and can be implemented in various forms without departing from the scope of the invention. Hereinafter, a modification will be described.

  (Modification 1) Modification 1 of the oscillation circuit will be described. In the first embodiment, it has been described that the value of n is set in advance in the register of the timer circuit 150 from the outside. However, the value may not be determined uniformly due to variations in the manufacturing process. Therefore, by measuring the elapsed time from when the phase difference of the phase difference signal Po actually disappears for each oscillation circuit 1 to when the phase difference is detected next, the value of n is written to the register. Also good.

  (Modification 2) Modification 2 of the oscillation circuit will be described. In the first embodiment, it has been described that the value of n is determined as one type. For example, the mode can be switched between a mode in which the oscillation circuit 1 is operated with high accuracy and a mode in which the oscillation circuit 1 is operated with low accuracy. The value of each n may be set.

  (Modification 3) Modification 3 of the oscillation circuit will be described. In the first embodiment, as illustrated in FIG. 2, the determination is made when the phase difference signal Po changes from the H level to the L level in step S108. However, at the next time after the change to the L level. Assuming that the level returns to the H level, step S106 and step S108 may be further inserted before shifting from step S108 to step S110. If comprised in this way, a synchronous determination precision can be improved.

  (Modification 4) Modification 4 of the oscillation circuit will be described. The oscillation circuit 1 can be mounted and used to oscillate a reference time of a wristwatch, a mobile phone, a notebook personal computer, or the like as an electronic device.

1 is a circuit diagram showing a configuration of an oscillation circuit according to a first embodiment. The flowchart which shows operation | movement of an oscillation circuit. FIG. 5 is a timing chart showing the operation of the oscillation circuit.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Oscillator circuit, 100 ... Atomic oscillator, 110 ... VCO, 120 ... Phase comparison part, 121 ... 1 / R frequency divider, 122 ... 1 / N frequency divider, 123 ... Phase comparator, 130 ... Control voltage generation part 131 ... DAC, 132 ... LPF, 140 ... switch circuit, 150 ... timer circuit.

Claims (6)

A high-precision oscillator with high frequency accuracy that outputs a reference signal of a reference frequency,
A voltage controlled oscillator that controls the frequency of the output signal with a control voltage; and
A phase comparator that detects a phase difference between the phase of the reference signal and the phase of the output signal and outputs a phase difference signal;
A control voltage generator for generating the control voltage based on the phase difference signal;
A switch circuit that switches the connection of the power source to the phase comparison unit to a connected state or a disconnected state;
Based on the phase difference signal, a control signal for setting the switch circuit in the connected state for a period from when the phase difference disappears until a predetermined time elapses, and for setting the switch circuit in the non-connected state for other periods. An output timer circuit;
including,
An oscillation circuit characterized by that.   2. The oscillation circuit according to claim 1, wherein the predetermined time is set to be equal to or less than a time obtained by dividing a half cycle of the voltage controlled oscillator by a phase difference generated for each cycle of the voltage controlled oscillator. Features an oscillation circuit.   2. The oscillation circuit according to claim 1, wherein the timer circuit measures an elapsed time from the time when the phase difference disappears to the next time when the phase difference is detected based on the phase difference signal, and the elapsed time. An oscillation circuit characterized in that the predetermined time is set based on   2. The oscillation circuit according to claim 1, wherein the oscillation circuit sets the predetermined time short when operating with high accuracy, and sets the predetermined time long when operating with low accuracy. Oscillator circuit to perform.   An electronic apparatus comprising the oscillation circuit according to claim 1. A high-precision oscillator with high frequency accuracy that outputs a reference signal of a reference frequency,
A voltage controlled oscillator that controls the frequency of the output signal with a control voltage; and
A phase comparator that detects a phase difference between the phase of the reference signal and the phase of the output signal and outputs a phase difference signal;
A control voltage generator for generating the control voltage based on the phase difference signal;
An oscillation circuit control method including:
Based on the phase difference signal, the power supply to the phase comparison unit is in a connected state during a period from when the phase difference disappears until a predetermined time elapses. Including a switch step of bringing the connection into a disconnected state,
And a method for controlling the oscillation circuit.

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