JP5311545B2 - Oscillator - Google Patents

Description

  The present invention relates to an oscillator.

  Conventionally, various oscillators have been developed, such as a temperature compensated crystal oscillator. This temperature-compensated crystal oscillator has a crystal oscillation circuit that uses a crystal resonator as a piezoelectric element and a temperature compensation circuit for compensating the frequency temperature characteristics of the crystal oscillation circuit. The

  FIG. 4 shows a configuration of an oscillator 10 as an example of such a temperature compensation crystal oscillator. The crystal oscillation circuit 20 forming the oscillator 10 includes a crystal resonator X10 as a piezoelectric element, and generates an output signal having a desired oscillation frequency.

  One end of the crystal unit X10 is connected to one end of a resistor R10 as a feedback resistor and to the input terminal of the inverter INV10. A variable capacitor C10 is connected between one end of the crystal unit X10 and the ground GND.

  On the other hand, the other end of the crystal unit X10 is connected to the other end of the resistor R10 and to the output terminal of the inverter INV10. A variable capacitor C20 is connected between the other end of the crystal unit X10 and the ground GND.

  The output terminal of the inverter INV10 is connected to the input terminal of the inverter INV20 as a buffer, and an output signal Fout having a desired oscillation frequency is output from the output terminal of the inverter INV20.

  The temperature compensation circuit 30 is a circuit for compensating the frequency temperature characteristic of the crystal oscillation circuit 20 in order to output the output signal Fout having a constant oscillation frequency from the oscillator 10 regardless of the change in temperature.

  Specifically, the temperature compensation circuit 30 has a temperature sensor for measuring the ambient temperature of the crystal oscillation circuit 20, and generates a desired compensation voltage based on the temperature obtained by the temperature sensor.

  The temperature compensation circuit 30 applies the compensation voltage to the variable capacitors C10 and C20, and changes the capacitance of the variable capacitors C10 and C20, thereby adjusting the oscillation frequency of the output signal Fout to perform temperature compensation.

  Further, the oscillator 10 applies a control voltage input from another signal processing circuit in the mobile phone in which the oscillator 10 is mounted via the control voltage input terminal Vc to the variable capacitors C10 and C20. The capacitances of the variable capacitors C10 and C20 are changed to adjust the oscillation frequency of the output signal Fout.

  Thereby, the secular change of the characteristics of the crystal unit X10, the deviation of temperature compensation by the temperature compensation circuit 30, and the like are adjusted, and the oscillation frequency of the output signal Fout is finely adjusted.

  In this way, a voltage obtained by adding the compensation voltage supplied from the temperature compensation circuit 30 and the control voltage input from the control voltage input terminal Vc is applied to the variable capacitors C10 and C20.

  On the other hand, the power supply voltage Vdd is supplied to the reference voltage generation circuit 50. The reference voltage generation circuit 50 generates a reference voltage based on the power supply voltage Vdd, and the generated reference voltage is used as the power supply terminals of the inverters INV10 and INV20. In addition, it is applied to the temperature compensation circuit 30.

  As a result, the inverters INV10 and INV20 and the temperature compensation circuit 30 are all in an operating state, so that the inverter INV20 outputs an output signal Fout having a desired oscillation frequency.

  Here, FIG. 5 shows how the oscillation frequency of the output signal Fout changes after the power supply voltage Vdd is supplied to the oscillator 10.

  As shown in FIG. 5, the output signal Fout output from the oscillator 10 has a constant voltage value at the timing t10 when the power supply voltage Vdd is supplied to the oscillator 10, but the amplitude varies with time. Gradually increases and when a predetermined time elapses, the amplitude becomes constant and the oscillation frequency shifts to a stable state. Thereafter, the oscillator 10 continues to output the output signal Fout in which the oscillation frequency is changed to the stable state.

  In the case of the oscillator 10, since the power supply voltage Vdd is always supplied to the reference voltage generation circuit 50, current consumption increases.

  By the way, in general, a mobile phone on which the oscillator 10 is mounted is configured to communicate with a base station at regular time intervals and operates intermittently. Therefore, current consumption can be reduced by switching the operating state of the oscillator 10 in response to intermittent operation of the mobile phone.

  Specifically, as a method of reducing current consumption, when a mobile phone is communicating with a base station, the power supply voltage Vdd is supplied to the oscillator 10 to turn on the oscillator 10 so that the mobile phone When not communicating with the station, there is a method of turning off the oscillator 10 by stopping supplying the power supply voltage Vdd to the oscillator 10.

  Here, in FIG. 6, when the mobile phone is communicating with the base station, the oscillator 10 is turned on. When the mobile phone is not communicating with the base station, the oscillator 10 is turned off. The state in which the current Idd flowing through the oscillator 10 changes is shown.

  In this case, when the oscillator 10 is in the off state, the current Idd is substantially “0”, and the current Idd having a predetermined value flows at the timing t40 when the oscillator 10 is switched to the on state. In this on state, the current Idd becomes substantially “0” at the timing t50 when the oscillator 10 is switched to the off state. Thereafter, the above operation is repeated alternately.

The literature names related to the temperature compensated crystal oscillator will be described below.
JP 2003-163542 A

  Incidentally, as shown in FIG. 5, in the case of such an oscillator 10, the power supply voltage Vdd is supplied to the oscillator 10, and the oscillation frequency of the output signal Fout transitions to a stable state from timing t10 when the oscillator 10 is switched to the on state. There is a problem that a certain time is required until the timing t20.

  The present invention reduces the time required for the transition of the oscillation frequency of the output signal to a stable state from the timing at which the output request signal that requests output of the output signal having a desired oscillation frequency is given, An object is to provide an oscillator capable of reducing current consumption.

An oscillator according to an aspect of the present invention includes a piezoelectric element, a resistor having at least one end connected to one end of the piezoelectric element, a first inverter having at least an input terminal connected to one end of the piezoelectric element, and the piezoelectric element. A variable capacitance element connected between the first inverter and the ground; a second inverter connected to the output terminal of the first inverter; and a power supply terminal of the first inverter having a desired oscillation frequency. The timing at which the output stop signal for stopping the output of the output signal by increasing the current supplied to the first inverter at the timing at which the output request signal for requesting the output of the output signal is given. The variable current source for reducing the current supplied to the first inverter and the power supply terminal of the second inverter are connected to the output request signal. The predetermined voltage is applied to the power supply terminal of the second inverter by switching to the ON state at the timing that is turned on, and the predetermined voltage is changed by switching to the OFF state at the timing when the output stop signal is given. A first switch that restricts application to the power supply terminal of the second inverter, and the variable current source supplies a current to be supplied to the first inverter at a timing when the output stop signal is given. The oscillation frequency of the output signal output from the first inverter is reduced to a current that maintains a stable state.

  The oscillator according to one aspect of the present invention generates a compensation voltage for changing the capacitance of the variable capacitance element, and applies the compensation voltage to the variable capacitance element, and is connected to the temperature compensation unit. By switching to the ON state at the timing when the output request signal is given, the predetermined voltage is applied to the temperature compensator, and by switching to the OFF state at the timing when the output stop signal is given And a second switch for restricting application of the predetermined voltage to the temperature compensation unit.

  According to the oscillator of the present invention, the time required for the transition of the oscillation frequency of the output signal to the stable state from the timing at which the output request signal that requests output of the output signal having the desired oscillation frequency is given. Current consumption can be reduced while shortening.

  Further, according to the oscillator of the present invention, the current supplied to the first inverter is maintained at the timing when the output stop signal is given, and the oscillation frequency of the output signal output from the first inverter maintains a stable state. The current consumption can be further reduced by reducing the current to a certain level.

  Further, according to the oscillator of the present invention, at the timing when the output stop signal is given, the second switch is turned off and the application of a predetermined voltage to the temperature compensation unit is restricted, thereby reducing the current consumption. Can be reduced.

  FIG. 1 shows a configuration of an oscillator 100 according to the embodiment of the present invention. The oscillator 100 is mounted on an electronic device such as a mobile phone, for example, and generates and outputs an output signal Fout having an oscillation frequency required for the mobile phone. Such a cellular phone uses the output signal Fout output from the oscillator 100 as a reference signal, thereby controlling the operation of various built-in circuits.

  A crystal oscillation circuit 200 forming the oscillator 100 includes a crystal resonator X100 as a piezoelectric element, and generates an output signal having a desired oscillation frequency. In the present embodiment, the crystal resonator X100 is used as the piezoelectric element, but various other piezoelectric elements such as a piezoelectric ceramic can be used.

  One end of the crystal unit X100 is connected to one end of a resistor R100 as a feedback resistor, and is also connected to an input terminal of an inverter INV100 corresponding to the first inverter. A variable capacitor C100 is connected between one end of the crystal unit X100 and the ground GND.

  On the other hand, the other end of the crystal unit X100 is connected to the other end of the resistor R100 and to the output terminal of the inverter INV100. Further, a variable capacitor C200 is connected between the other end of the crystal unit X100 and the ground GND.

  The variable capacitors C100 and C200 operate as a variable capacitance element for adjusting the oscillation frequency of the output signal Fout according to the applied voltage. In this case, a variable capacitance diode may be used instead of the variable capacitors C100 and C200.

  The output terminal of the inverter INV100 is connected to the input terminal of an inverter INV200 corresponding to the second inverter as a buffer, and an output signal Fout having a desired oscillation frequency is output from the output terminal of the inverter INV200.

  The temperature compensation circuit 300 corresponds to the temperature compensation unit, and outputs the output signal Fout having a constant oscillation frequency from the oscillator 100 regardless of a change in temperature, so that the frequency temperature characteristic of the crystal oscillation circuit 200 is compensated. Circuit.

  Specifically, the temperature compensation circuit 300 includes a temperature sensor for measuring the temperature around the crystal oscillation circuit 200, and generates a desired compensation voltage based on the temperature obtained by the temperature sensor.

  The temperature compensation circuit 300 applies the compensation voltage to the variable capacitors C100 and C200, and changes the capacitance of the variable capacitors C100 and C200, thereby adjusting the oscillation frequency of the output signal Fout to perform temperature compensation.

  Further, the oscillator 100 applies a control voltage input from another signal processing circuit in the mobile phone in which the oscillator 100 is mounted via the control voltage input terminal Vc to the variable capacitors C100 and C200. The capacitances of the variable capacitors C100 and C200 are changed to adjust the oscillation frequency of the output signal Fout. The control voltage is always input from the control voltage input terminal Vc and applied to the variable capacitors C100 and C200.

  Thus, the secular change of the characteristics of the crystal unit X100, the temperature compensation shift by the temperature compensation circuit 300, and the like are adjusted, and the oscillation frequency of the output signal Fout is finely adjusted.

  In this way, a voltage obtained by adding the compensation voltage supplied from the temperature compensation circuit 300 and the control voltage input from the control voltage input terminal Vc is applied to the variable capacitors C100 and C200.

  In this case, another variable capacitor is connected between the other end of the crystal unit X100 and the ground GND, and a compensation voltage supplied from the temperature compensation circuit 300 is applied to the variable capacitors C100 and C200. The control voltage input from the control voltage input terminal Vc may be applied to the newly connected variable capacitor.

  On the other hand, the power supply voltage Vdd is supplied to the reference voltage generation circuit 500, and the reference voltage generation circuit 500 generates a reference voltage based on the power supply voltage Vdd and outputs it to the control circuit 400. The control circuit 400 is a circuit for controlling the operation states of the crystal oscillation circuit 200, the inverter INV200, and the temperature compensation circuit 300 based on a control signal supplied from the outside (another signal processing circuit mounted on the mobile phone). And includes switches SW10 and SW20 and a variable current source VI.

  Specifically, the switch SW10 corresponding to the first switch is connected between the reference voltage generation circuit 500 and the power supply terminal of the inverter INV200, and the switch SW20 corresponding to the second switch is the reference voltage generation circuit. 500 and the temperature compensation circuit 300, and the variable current source VI is connected between the reference voltage generation circuit 500 and the power supply terminal of the inverter INV100.

  The variable current source VI changes the current supplied to the inverter INV100, that is, the operating current for operating the inverter INV100, based on the given control signal. That is, the variable current source VI increases the operating current for operating the inverter INV100 when an output request signal that requests output of an output signal having a desired oscillation frequency is given as a control signal.

  On the other hand, the variable current source VI reduces the operating current for operating the inverter INV100 when an output stop signal for stopping outputting an output signal having a desired oscillation frequency is given as a control signal. Let As a result, the oscillation frequency of the output signal output from the crystal oscillation circuit 200 is reduced to the minimum required operating current to maintain a stable state.

  The switch SW10 switches its connection state based on the given control signal. That is, the switch SW10 is turned on when an output request signal is given as a control signal, and applies the reference voltage to the power supply terminal of the inverter INV200. In this case, the inverter INV200 enters an operating state and outputs an output signal Fout having a desired oscillation frequency.

  On the other hand, when the output stop signal is given as the control signal, the switch SW10 is turned off and restricts application of the reference voltage to the power supply terminal of the inverter INV200. In this case, the inverter INV200 enters a non-operating state and stops outputting the output signal Fout having a desired oscillation frequency.

  Similarly, the switch SW20 switches the connection state based on the given control signal. That is, the switch SW20 is turned on when an output request signal is given as a control signal, and applies the reference voltage to the temperature compensation circuit 300. In this case, the temperature compensation circuit 300 enters an operating state and performs temperature compensation.

  On the other hand, when the output stop signal is given as the control signal, the switch SW20 is turned off and restricts the application of the reference voltage to the temperature compensation circuit 300. In this case, the temperature compensation circuit 300 is not operated and does not perform temperature compensation.

  By the way, in general, a mobile phone communicates with a base station at regular time intervals and operates intermittently. Thereby, when the mobile phone is not communicating with the base station, an output stop signal is given as a control signal, and the variable current source VI reduces the operating current for operating the inverter INV100 to the minimum necessary current. Both the switches SW10 and SW20 are turned off, and the inverter INV200 and the temperature compensation circuit 300 are deactivated. Hereinafter, this state is referred to as a standby state in the oscillator 100.

  In this case, the crystal oscillation circuit 200 generates an output signal whose oscillation frequency is maintained in a stable state. However, since the inverter INV200 is in a non-operation state, the oscillator 100 has a desired oscillation frequency required by the mobile phone. Stops outputting the output signal Fout having

  In this standby state, when the mobile phone attempts to start communication with the base station and an output request signal is given as a control signal, the variable current source VI increases the operating current for operating the inverter INV100 and switches SW10 and SW20. Is turned on, and the inverter INV200 and the temperature compensation circuit 300 are in an operating state. Hereinafter, this state is referred to as an operation state in the oscillator 100.

  As a result, the oscillator 100 immediately outputs the output signal Fout whose oscillation frequency is already maintained in a stable state to the outside at the timing when the output request signal is given, and the output request signal is output while the output request signal is given. Continue to output the signal Fout.

  In this operation state, when the mobile phone ends communication with the base station and an output stop signal is given as a control signal, the oscillator 100 transitions to the standby state again. In this standby state, the crystal oscillation circuit 200 continues to generate an output signal whose oscillation frequency is maintained in a stable state in preparation for the output request signal being given at a predetermined timing.

  As described above, according to the present embodiment, when the oscillator 100 is in the standby state, the minimum necessary operating current is sufficient to maintain the oscillation frequency of the output signal output from the crystal oscillation circuit 200 in a stable state. Only the crystal oscillation circuit 200 is selectively operated, and the output signal Fout whose oscillation frequency is maintained in a stable state is immediately output at the timing when the output request signal is given.

  As a result, current consumption can be reduced while shortening the time required from the timing when the output request signal is given until the oscillation frequency of the output signal Fout output from the oscillator 100 transitions to a stable state.

  Here, FIG. 2 shows how the oscillation frequency of the output signal Fout changes when the oscillator 100 of the present embodiment transitions from the standby state to the operating state.

  As shown in FIG. 2, according to the present embodiment, the output signal Fout whose oscillation frequency is already maintained in a stable state can be immediately output at the timing t30 when the output request signal is given. Therefore, the time required from the timing when the output request signal is given to the timing when the oscillation frequency transitions to the stable state can be shortened.

  FIG. 3 shows how the current Idd flowing in the oscillator 100 changes when the oscillator 100 of the present embodiment alternately repeats the standby state or the operating state. The same elements as those shown in FIG. 6 are denoted by the same reference numerals.

  As shown in FIG. 3, according to the present embodiment, when the oscillator 100 is in the standby state, a minimum necessary current Idd that maintains the oscillation frequency in a stable state flows (time 0 to t80). , T50 to t90), from the timing t40 when the output request signal is given to the timing t80 at which the oscillation frequency transitions to the stable state, as compared with FIG. 6 showing how the current Idd flowing in the oscillator 10 changes. The current Idd flowing therebetween can be greatly reduced, and as a result, the current consumption can be reduced as a whole.

  The above-described embodiment is an example and does not limit the present invention. For example, a resistor may be connected between the connection point of the crystal unit X100 and the variable capacitor C200 and the other end of the crystal unit X100. Of the connection lines for connecting the other end of the crystal unit X100, one end of the variable capacitor C200, the other end of the resistor R100, and the output terminal of the inverter INV100, the connection line and the connection point of the crystal unit X100, A resistor may be connected between the connection line and the connection point of the resistor R100.

  In the above-described embodiment, the case where the oscillator 100 is mounted on the mobile phone has been described. However, the oscillator 100 may be mounted on various other electronic devices such as a navigation device having a GPS function.

  In addition, without providing the temperature compensation circuit 300, only the control voltage input via the control voltage input terminal Vc may be applied to the variable capacitors C100 and C200 to adjust the oscillation frequency of the output signal Fout. .

It is a circuit diagram which shows the structure of the oscillator by embodiment of this invention. In the case of this Embodiment, it is a graph which shows a mode that the oscillation frequency of an output signal changes. 6 is a timing chart showing how the current flowing in the oscillator changes in the case of the present embodiment. It is a circuit diagram which shows the structure of the conventional oscillator. It is a graph which shows a mode that the oscillation frequency of an output signal changes after a power supply voltage is supplied to an oscillator. 6 is a timing chart showing how the current flowing in the oscillator changes when the operating state of the oscillator is switched.

Explanation of symbols

10, 100 Oscillator 20, 200 Crystal oscillation circuit 30, 300 Temperature compensation circuit 400 Control circuit 50, 500 Reference voltage generation circuit X10, X100 Crystal resonator R10, R100 Resistors C10, C20, C100, C200 Variable capacitors INV10, INV20, INV100 INV200 Inverter SW10, SW20 Switch VI Variable current source

Claims (2)

A piezoelectric element;
A resistor having at least one end connected to one end of the piezoelectric element;
A first inverter having at least an input terminal connected to one end of the piezoelectric element;
A variable capacitance element connected between the piezoelectric element and the ground;
A second inverter connected to the output terminal of the first inverter;
The current supplied to the first inverter is increased at a timing when an output request signal that is connected to the power supply terminal of the first inverter and requests to output an output signal having a desired oscillation frequency is given, A variable current source that reduces a current supplied to the first inverter at a timing when an output stop signal for stopping outputting the output signal is given;
A predetermined voltage is applied to the power supply terminal of the second inverter by switching to the ON state at the timing when the output request signal is given and connected to the power supply terminal of the second inverter, and the output stop signal A first switch that restricts application of the predetermined voltage to the power supply terminal of the second inverter by switching to an off state at a given timing ;
The variable current source is:
Reducing the current supplied to the first inverter to a current at which the oscillation frequency of the output signal output from the first inverter maintains a stable state at the timing when the output stop signal is given. Features an oscillator. A temperature compensation unit that generates a compensation voltage for changing the capacitance of the variable capacitance element, and applies the compensation voltage to the variable capacitance element;
The predetermined voltage is applied to the temperature compensator by switching to the ON state at the timing when the output request signal is given, connected to the temperature compensator, and at the timing when the output stop signal is given, A second switch that limits application of the predetermined voltage to the temperature compensation unit by switching to an off state;
The oscillator according to claim 1, further comprising:

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