JP2009284045A - Piezoelectric oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric oscillator the frequency fluctuations of which are reduced. <P>SOLUTION: The piezoelectric oscillator comprises: a temperature sensor 3; a temperature compensation voltage generation unit 4, which generates a low temperature compensation voltage for compensating temperature characteristics on a low temperature side based upon a room temperature and a high temperature compensation voltage for compensating temperature characteristics on a high temperature side, on the basis of the detection output of the temperature sensor 3; a temperature sensor phase switching unit 9 which changes the phase of the detection output of the temperature sensor 3 when the detection output of the temperature sensor 3 decreases below a predetermined voltage and outputs the detection output; an HPF 10, which inputs the output voltage output from the temperature sensor phase switching unit 9, passes only a high-pass component included in the detection output of the temperature sensor 3, and superposes it on a reference voltage to output the reference voltage with the high-pass component superimposed on it, and an oscillation circuit unit 7 constituted by connecting an oscillation circuit 21, a piezoelectric vibrator 22, and a frequency temperature compensating circuit 23 in series. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a temperature-compensated piezoelectric oscillator using a piezoelectric vibrator such as a crystal vibrator, and is particularly suitable for suppressing temperature fluctuation of a temperature sensor of a MOS-type temperature-compensated piezoelectric oscillator.

In recent years, piezoelectric oscillators are used in many fields from communication devices such as mobile phones to consumer devices such as quartz watches because of their frequency stability, small size and light weight, and low price. In particular, a temperature compensated piezoelectric oscillator (TCXO) that compensates for the frequency temperature characteristics of a piezoelectric vibrator is widely used in mobile phones and the like that require frequency stability.
Patent Document 1 discloses a temperature compensated piezoelectric oscillator using a MOS varactor.
Patent Document 2 discloses a temperature compensated piezoelectric oscillator in which voltage noise is canceled and phase noise is reduced by putting in-phase signals at both ends of a varactor.
JP 2005-167510 A JP 2004-320239 A

However, in the temperature compensated piezoelectric oscillator using the conventional MOS type varactor disclosed in Patent Document 1, when the temperature of the fan fluctuates, the temperature detected by the temperature sensor fluctuates when the temperature fluctuates instantaneously. As a result, the oscillation frequency fluctuates and the short-term stability deteriorates.
Further, even if the technique disclosed in Patent Document 2 is simply applied to a temperature compensated oscillator using a conventional MOS type varactor, the temperature sensitivity of the temperature compensated voltage applied to the varactor and the other are considered because of temperature compensation. Since the temperature sensitivity of the reference voltage cannot be made equal, it is difficult to stabilize the frequency against temperature fluctuation.
Further, if the temperature sensitivity of the voltage across the varactor is different, there is a problem that the frequency cannot be stabilized against temperature fluctuation.
The present invention has been made in order to solve the above-mentioned problem, and has reduced the frequency fluctuation.
Another object of the present invention is to provide a temperature compensated piezoelectric oscillator using a type varactor.

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 piezoelectric oscillator according to the present invention includes a temperature sensor for detecting temperature, a low-temperature compensation voltage for compensating temperature characteristics on the low temperature side centered on normal temperature based on the detection output of the temperature sensor, and a high temperature A temperature compensation voltage generator for generating a high temperature compensation voltage for compensating the temperature characteristic of the side, and a temperature sensor that switches and outputs the phase of the detection output of the temperature sensor when the detection output of the temperature sensor falls below a predetermined voltage A high-pass filter that outputs only the high-frequency component included in the detection output of the temperature sensor and superimposes it on the reference voltage, with the output voltage output from the temperature sensor phase switching unit as an input, and a phase switching unit; An oscillation circuit, a piezoelectric vibrator, and a frequency temperature compensation circuit are connected in series. The frequency temperature compensation circuit is connected to a circuit in which a first variable capacitance element and a capacitor are connected in series. A circuit in which a first variable capacitance element and a second variable capacitance element having a polarity opposite to each other are connected in parallel, and a low-temperature compensation voltage is supplied to a connection point between a back gate of the first variable capacitance element and the capacitance, and the capacitance A high temperature compensation voltage is supplied to the connection point between the first variable capacitance element and the gate of the second variable capacitance element, and the output voltage from the high-pass filter is connected to the connection point between the gate of the first variable capacitance element and the back gate of the second variable capacitance element. And an oscillation circuit unit to which the signal is supplied.

When configured as described above, even if the ambient temperature fluctuates instantaneously, the high or low temperature compensation voltage of the temperature compensation voltage generator and the reference voltage on which the temperature fluctuation component is superimposed both fluctuate in the same phase. In the frequency temperature compensation circuit of the oscillation circuit section, the temperature fluctuation component included in the temperature compensation voltage can be canceled, and a piezoelectric oscillator in which the oscillation frequency is not affected by the temperature fluctuation can be realized.
Therefore, if the piezoelectric oscillator of the present invention is applied to an application in which a heat source such as a fan or a heater is disposed, the degree of freedom of the heat source arrangement can be expanded.
Further, by making the sensitivity of the temperature sensor even higher than before, the response of the frequency temperature correction to the change in the ambient temperature can be improved. That is, it is possible to achieve both improvement in the response speed of frequency temperature correction and suppression of frequency correction noise caused by minute fluctuations in temperature.

[Application Example 2] A clip circuit that clips the low temperature compensation voltage and the high temperature compensation voltage to a predetermined voltage when the low temperature compensation voltage and the high temperature compensation voltage are equal to or lower than a predetermined voltage,
A filter control unit that outputs a high-level voltage when the low-temperature compensation voltage or the high-temperature compensation voltage is clipped to a predetermined voltage, and the high-pass filter has a high input voltage from the filter control unit. When it is level, only the reference voltage is supplied to the oscillation circuit unit, and when the input voltage from the filter control unit is other than high level, the high frequency component included in the detection output of the temperature sensor is added to the reference voltage. Application example 1 of superimposing and supplying the oscillation circuit unit
The piezoelectric oscillator described in the above item is characterized.

With the above configuration, the high-temperature compensation voltage or the low-temperature compensation voltage output from the temperature compensation voltage generator is input to the frequency temperature compensation circuit of the oscillation circuit during the period when the clipping circuit is clipped to a constant voltage level. Since the high temperature compensation voltage and the low temperature compensation voltage are not affected by the fluctuation component of the temperature sensor, the temperature fluctuation component is directly supplied to the oscillation circuit unit without being superimposed on the reference voltage. Accordingly, it is possible to realize a piezoelectric oscillator in which the oscillation frequency is not affected by fluctuation even when the clip circuit is provided.

Application Example 3 The temperature sensor phase switching unit outputs a detection voltage in phase with the detection output of the temperature sensor when the detection output of the temperature sensor is equal to or higher than a predetermined voltage, and the detection output of the temperature sensor is equal to or lower than the predetermined voltage. In this case, the piezoelectric oscillator according to Application Example 1 or 2 that outputs a detection voltage having a phase opposite to that of the detection output of the temperature sensor is characterized.

When configured as described above, the temperature compensation voltage generating unit high temperature or low temperature compensation voltage and the reference voltage on which the temperature fluctuation component is superimposed both fluctuate in the same phase. A temperature fluctuation component included in the voltage can be canceled, and a piezoelectric oscillator in which the oscillation frequency is not affected by the temperature fluctuation can be realized.

[Application Example 4] The piezoelectric element according to any one of Application Examples 1 to 5, in which the variable capacitance element is a MOS variable capacitance element, a varactor, a variable capacitance diode, or a semiconductor device whose capacitance is changed by an applied voltage. Featuring an oscillator.

When configured as described above, it is possible to select a suitable variable capacitance element and to eliminate noise due to temperature fluctuations when configuring a temperature compensated piezoelectric oscillator or making an oscillation circuit into an IC. There is.

Hereinafter, embodiments of the piezoelectric oscillator of the present invention will be described.
FIG. 1 is a block diagram showing a configuration of a temperature compensated piezoelectric oscillator according to the first embodiment of the present invention.
A temperature compensated piezoelectric oscillator (hereinafter simply referred to as “piezoelectric oscillator”) 1 shown in FIG. 1 includes a constant voltage generator 2, a temperature sensor 3, a temperature compensated voltage generator 4, clip circuits 5 and 6, and an oscillation circuit unit. 7, switching control unit 8, temperature sensor phase switching unit 9, and high-pass filter (hereinafter "HPF")
10).
The constant voltage generator 2 generates a predetermined voltage from a power supply voltage input from a voltage source circuit (not shown), and outputs it to the temperature sensor 3, the temperature compensation voltage generator 4, and the like.
The temperature sensor 3 is composed of, for example, a thermistor or a diode, and detects the ambient temperature or the internal temperature of the piezoelectric oscillator 1 and outputs a detection voltage VT. The detection voltage VT output from the temperature sensor 3 has a negative slope characteristic in which the voltage decreases as the temperature rises.
The temperature compensation voltage generator 4 is based on the detection voltage VT from the temperature sensor 3 at room temperature (25 ° C.
), A low temperature compensation voltage VL for compensating the low temperature side temperature characteristic and a high temperature compensation voltage VH for compensating the high temperature side temperature characteristic are generated.
The clip circuit 5 clips when the low temperature compensation voltage VL output from the temperature compensation voltage generator 4 reaches a predetermined clip voltage Vcl1. The clip circuit 6 clips when the high temperature compensation voltage VH output from the temperature compensation voltage generator 4 reaches a predetermined clip voltage Vcl2.

The oscillation circuit unit 7 is configured by connecting an oscillation circuit 21, a piezoelectric vibrator 22, a frequency temperature compensation circuit 23, and a capacitor (capacitance) C1 in series.
The oscillation circuit 21 is a Colpitts type oscillation circuit, and a self-bias circuit is configured in which the collector of the transistor Tr is connected to the power supply VDD via the resistor R1, and the resistor R2 is connected between the base and the collector. A capacitor C2 is provided between the base and emitter of the transistor Tr1.
The emitter resistor R3 and the capacitor C3 are connected in parallel between the emitter and the ground.
The frequency temperature compensation circuit 23 is a first variable capacitance element (first MOS varactor) for low temperature compensation.
This is a circuit in which a first variable varactor ML (second MOS type varactor) MH having a polarity opposite to that of the first MOS type varactor ML is connected in parallel to a circuit in which ML and a capacitor C4 are connected in series. The connection point between the back gate of the first MOS type varactor ML and the capacitor C4 has a resistance R
4 is applied with a low temperature compensation voltage VL, and a connection point between the capacitor C4 and the gate of the second MOS type varactor MH is applied with a high temperature compensation voltage VH through a resistor R5. A reference voltage Vref is applied from the HPF 10 to the connection point between the gate of the first MOS varactor ML and the back gate of the second MOS varactor MH via the resistor R6.
The switching control unit 8 is configured to detect the detection voltage VT of the temperature sensor 3 and the reference temperature voltage VT shown in FIG.
When the detected voltage VT is equal to or lower than the reference temperature voltage VTref, the switching control signal SV1 that switches from the high level (H level) to the low level (L level) as shown in FIG. Output to the temperature sensor phase switching unit 9. The sensor reference voltage VTref is normal temperature (25
The detected voltage VT output from the temperature sensor 3 at the time of (° C.).

The temperature sensor phase switching unit 9 includes a non-inverting amplifier 31a and an inverting amplifier 31b, and a switch 3
And a switch circuit 32 having 2a and 32b.
The detection voltage VT of the temperature sensor 3 is input to the non-inverting amplifier 31a and the inverting amplifier 31b, and the output of either the non-inverting amplifier 31a or the inverting amplifier 31b is the switch circuit 3.
2 is output. The switch circuit 32 is subjected to on / off switching control by the switching control signal SV1 from the switching control unit 8. When the switching control signal SV1 is at the H level, the switch 32a on the non-inverting amplifier 31a side is turned on and inverted. The switch 32b of the amplifier 31b is turned off. Conversely, when the switching control signal SV1 is at the L level, the switch 3 on the non-inverting amplifier 31a side.
2a is turned off, and the switch 32b of the inverting amplifier 31b is turned on.
Therefore, the output voltage VT2 of the temperature sensor phase switching unit 9 has a waveform as shown in FIG.
That is, the detection voltage VT2 having the same phase as the detection voltage VT of the temperature sensor 3 is output in a low temperature region of room temperature (25 ° C.) or less, and the detection voltage VT opposite to the detection voltage VT of the temperature sensor 3 is output in a high temperature region of room temperature or more. VT2 is output.
The HPF 10 is composed of, for example, a passive filter composed of a resistor R7 and a capacitor C5. The detection voltage VT2 output from the temperature sensor phase switching unit 9 is used as an input, and a high frequency component, that is, a temperature fluctuation component included in the detection voltage VT2. Only the high frequency component that has passed is superimposed on the reference voltage Vref and output to the oscillation circuit unit 7.
Here, the constant of the passive filter by RC is R7 = 1 MΩ, C5 = 0.01u.
Assuming F, the reference voltage V passes through the filter when the temperature fluctuation component exceeds about 16 Hz.
It will be superimposed on ref.

Here, the temperature compensation principle of the piezoelectric oscillator of the present embodiment will be described with reference to FIGS.
FIG. 4A is a diagram showing the CV characteristics of a MOS varactor.
The temperature compensation principle using the S-type varactor will be schematically described. Using the rising region (B region) and the falling region (A region) of the CV characteristic 70 of the MOS varactor, the low temperature and the high temperature respectively. This is a configuration for performing compensation. FIG. 4B is a diagram showing the relationship between the load capacity and temperature (compensation capacity curve) when the MOS varactor having the characteristics shown in FIG. 4A is used.
The low temperature region C of the compensation capacitance curve shown in FIG. 4B is generated by the above-described first MOS varactor ML for low temperature compensation. Further, the high temperature region D of the compensation capacitance curve is generated by the above-described second MOS varactor MH for high temperature compensation. That is, the frequency temperature compensation circuit 23 provided in the oscillation circuit section 7 of the piezoelectric oscillator 1 of the present embodiment is provided with low-temperature and high-temperature MOS type varactors, and thereby the frequency of the piezoelectric vibrator 22. The characteristic of the capacity curve 71 for temperature compensation can be obtained.

FIG. 5A shows the relationship between the high temperature compensation voltage and the temperature.
For the high temperature compensation, as shown in FIG. 5 (b), the left side region (use region) in the rising curve of the CV characteristic of the MOS varactor is used. In the region, the high temperature compensation voltage VH is applied to the clip circuit 6 as shown in FIG.
Thus, the clip control is performed to obtain a constant voltage, and the voltage is controlled to rise linearly as the temperature rises only in a high temperature region that requires temperature compensation. At this time, the reference voltage Vref and the high temperature compensation voltage VH become equal (potential difference = 0), and the temperature at the point P becomes the high temperature portion of the compensation temperature.
FIG. 6A is a diagram showing the relationship between the low temperature compensation voltage and the temperature.
For the low temperature compensation, as shown in FIG. 6B, the right region (use region) in the rising curve of the C-V characteristic of the MOS varactor is used. In the region, the low temperature compensation voltage VL is applied to the clip circuit 5 as shown in FIG.
Thus, the clip control is performed so that the voltage is constant, and the voltage is controlled to rise linearly as the temperature decreases only in a low temperature region that requires temperature compensation. At this time, the reference voltage Vref and the low temperature compensation voltage VL become equal (potential difference = 0), and the temperature at the point Q becomes the low temperature portion of the compensation temperature.

FIG. 7 is a diagram showing temperature characteristics of the compensation voltage of the piezoelectric oscillator according to the present embodiment, where the vertical axis shows the compensation voltage and the horizontal axis shows the ambient temperature. The reference voltage Vref from the HPF 10 is, for example, a constant positive voltage, and the first MOS varactor ML of the oscillation circuit unit 7 is connected via the resistor R6.
Is supplied to a connection point between the first gate and the back gate of the second MOS type varactor MH. In this case, a reverse bias is applied to the first MOS varactor ML, and a forward bias is applied to the second MOS varactor MH. In this state, the operation of the low temperature compensation voltage VL is first performed at a low temperature (−4
A case where the temperature continuously changes from 0 ° C. to a high temperature (+ 90 ° C.) will be described.
The low temperature compensation voltage VL is at the intersection with the reference voltage Vref at −40 ° C., and the first M at that time
The capacity of the OS type varactor ML is a predetermined capacity when the voltage between the terminals of the first MOS type varactor ML is 0V. As the temperature rises, the low-temperature compensation voltage VL decreases linearly, and accordingly, the potential difference of the first MOS varactor ML increases and the capacitance increases. When the low-temperature compensation voltage VL decreases to the clip voltage Vcl1 of the clip circuit 5, the clip circuit 5
The low temperature compensation voltage VL is clipped by the clip voltage Vcl1 and becomes constant.

Next, the case where the operation of the high temperature compensation voltage VH continuously changes from a high temperature (+ 90 ° C.) to a low temperature (−40 ° C.) will be described.
The high temperature compensation voltage VH is at the intersection with the reference voltage Vref at + 90 ° C., and the second M at that time
The capacity of the OS type varactor MH is a predetermined capacity when the voltage between the terminals of the second MOS type varactor MH is 0V. When the temperature decreases, the high temperature compensation voltage VH decreases linearly, and accordingly, the potential difference of the second MOS varactor MH increases and the capacitance decreases. When the high temperature compensation voltage VH decreases to the clip voltage Vcl2 of the clip circuit 6, the clip circuit 6
The high temperature compensation voltage VH is clipped by the clip voltage Vcl2 and becomes constant.
With this configuration, in the indirect temperature compensation type piezoelectric oscillator using the MOS type varactor, the low temperature compensation voltage VL and the high temperature compensation voltage VH can be linearly changed, and the configuration of the temperature compensation circuit is facilitated.
Further, in the piezoelectric oscillator of this embodiment, the low-temperature compensation voltage VL and the high-temperature compensation voltage VH that change linearly with temperature are clipped around the normal temperature, so that the capacitance values of the first and second MOS type varactors ML and MH are clipped. The frequency stability can be increased by avoiding the region where the frequency becomes unstable.

In addition to the above configuration, the piezoelectric oscillator 1 according to the present embodiment includes the switching control unit 8, the temperature sensor phase switching unit 9, and the HPF 10. Then, in order to extract only the temperature fluctuation component that occurs when the temperature fluctuates instantaneously, the detection voltage VT of the temperature sensor 3 is input to the HPF 10 via the temperature sensor phase switching unit 9, and the HPF 10 detects the temperature sensor 3. The high-frequency component (fluctuation component) included in the detection voltage VT is allowed to pass. HPF
The high frequency component that has passed through 10 is superimposed on the reference voltage Vref in the HPF 10 and supplied to the oscillation circuit unit 7. At this time, the temperature sensor phase switching unit 9 performs temperature sensor 3 for each temperature region.
The phase of the temperature fluctuation component included in the output voltage VT is inverted to the in-phase output at the low temperature and the reverse phase output at the high temperature, and input to the HPF 10.
With this configuration, even when the ambient temperature fluctuates instantaneously, the temperature compensation voltage generator 4
Since the temperature compensation voltage and the reference voltage Vref on which the temperature fluctuation component is superimposed both fluctuate in the same phase, the frequency temperature compensation circuit 23 of the oscillation circuit unit 7 cancels the fluctuation component (high frequency component) included in the temperature compensation voltage. Thus, a piezoelectric oscillator whose oscillation frequency is not affected by temperature fluctuations can be realized.
If the piezoelectric oscillator of this embodiment is configured in this way, the degree of freedom of heat source arrangement can be expanded even when applied to an application in which a heat source such as a fan or a heater is arranged.
Further, by making the sensitivity of the temperature sensor even higher than before, the response of the frequency temperature correction to the change in the ambient temperature can be improved. That is, it is possible to achieve both improvement in the response speed of frequency temperature correction and suppression of frequency correction noise caused by minute fluctuations in temperature.
When the ambient temperature changes gently, the temperature fluctuation component included in the temperature sensor 3 is cut by the HPF 10, and the reference voltage Vref is kept stable at the DC level, so that the compensation voltage follows the temperature change. Thus, temperature compensation can be performed.

Next, a second embodiment of the present invention will be described.
FIG. 8 is a block diagram showing a configuration of a temperature compensated piezoelectric oscillator according to the second embodiment of the present invention. The same parts as those of the piezoelectric oscillator shown in FIG.
The piezoelectric oscillator 40 shown in FIG. 8 includes a filter control unit 41 and an HPF.
The configuration of 42 is different from the piezoelectric oscillator 1 shown in FIG.
The filter control unit 41 receives a predetermined voltage from the constant voltage generation unit 2 and receives a high temperature compensation voltage VH and a low temperature compensation voltage VL from the temperature compensation voltage generation unit 4. Based on the high temperature compensation voltage VH and the low temperature compensation voltage VL, an H level control signal SV2 is output to the HPF 42 within a predetermined temperature range including normal temperature (25 ° C.).
Here, the predetermined temperature range in which the control signal SV2 becomes H level is a constant level when the voltage level of the high temperature compensation voltage VH or the low temperature compensation voltage VL output from the temperature compensation voltage generator 4 is clipped to the clip circuits 5 and 6. The temperature range becomes.

The HPF 42 includes a switch circuit 43 having a resistor R7, a capacitor C5, and switches 43a and 43b. One end of the switch 43a of the switch circuit 43 is a capacitor C.
The other end is connected to the output line of the temperature sensor phase switching unit 9. On the other hand, one end of the switch 43b is connected to the capacitor C5, and the other end is grounded.
The switch circuit 43 is on / off controlled by the control signal SV2 from the filter control unit 41. When the control signal SV2 is at the H level, the switch 43b is turned on and the switch 43a is turned off. Conversely, when the control signal SV2 is at the L level, the switch 43a is on,
The switch 43b is turned off.
That is, during the period when the control signal SV2 from the filter control unit 41 is at L level, that is, the period during which the high temperature compensation voltage VH or the low temperature compensation voltage VL varies linearly with temperature, the output voltage VT2 of the temperature sensor phase switching unit 9 Is input to the HPF 42, and the HPF 42 extracts a high frequency component (fluctuation generation) included in the detection voltage VT of the temperature sensor 3. The extracted high-frequency component is superimposed on the reference voltage Vref and supplied to the oscillation circuit unit 7.
Further, the period during which the control signal SV2 from the filter control unit 41 is at the H level, that is, the period during which the high temperature compensation voltage VH or the low temperature compensation voltage VL is clipped to the constant voltage level by the clip circuits 5 and 6, By turning on the switch 43b and grounding the other end of the capacitor C5, the output voltage VT2 of the temperature sensor phase switching unit 9 is not input to the HPF 42. That is, in the vicinity of room temperature where the high temperature compensation voltage VH or the low temperature compensation voltage VL is clipped to a constant voltage level, the temperature fluctuation component is directly supplied to the oscillation circuit unit 7 without being superimposed on the reference voltage Vref.

With such a configuration, even when the ambient temperature fluctuates instantaneously during the period in which the high temperature compensation voltage VH or the low temperature compensation voltage VL output from the temperature compensation voltage generator 4 varies linearly with temperature, Since the temperature compensation voltage of the compensation voltage generation unit 4 and the reference voltage on which the temperature fluctuation component is superimposed fluctuate in the same phase, the frequency temperature compensation circuit 23 of the oscillation circuit unit 7
The fluctuation component (high frequency component) included in the temperature compensation voltage can be canceled. As a result, a piezoelectric oscillator whose oscillation frequency is not affected by fluctuations can be realized.
Further, the high temperature compensation voltage VH or the low temperature compensation voltage VL output from the temperature compensation voltage generator 4 is used.
During the period when the clipping circuits 5 and 6 are clipped to a constant voltage level.
The high temperature compensation voltage VH and the low temperature compensation voltage VL input to the frequency temperature compensation circuit 23 are not affected by the fluctuation component of the temperature sensor 3, and thus directly oscillate without superimposing the temperature fluctuation component on the reference voltage Vref. By supplying to the circuit unit 7, it is possible to realize a piezoelectric oscillator whose oscillation frequency is not affected by fluctuations.
Therefore, if the piezoelectric oscillator of this embodiment is configured as described above, the degree of freedom of the heat source arrangement, even when applied to an application in which a heat source such as a fan or a heater is arranged, as in the piezoelectric oscillator of the first embodiment. Can be spread.
Further, by making the sensitivity of the temperature sensor even higher than before, the response of the frequency temperature correction to the change in the ambient temperature can be improved. That is, it is possible to achieve both improvement in the response speed of frequency temperature correction and suppression of frequency correction noise caused by minute fluctuations in temperature.

FIG. 9 is a diagram showing a configuration example of the filter control unit, (a) is a circuit diagram, (b) is a diagram showing an operation mode, and FIG. 10 is each part of the filter control unit shown in FIG. 9 (a). FIG.
The filter control unit 41 shown in FIG. 9A includes three comparators 51, 52, 53 and 4
It is composed of two switches SW1, SW2, SW3, SW4.
The non-inverting input terminal (+) of the comparators 51 and 52 is applied with a voltage Vreg obtained by dropping the predetermined voltage from the constant voltage generator 2 by the diode D1. The low temperature compensation voltage VL is applied to the inverting input terminal (−) of the comparator 51. The inverting input terminal (−) of the comparator 52 is connected to the output terminal of the comparator 52 through the switch SW2.
The non-inverting input terminal (+) of the comparator 53 is connected to one end of the switch SW4 and is connected to one end of the switches SW1 and SW3 via the resistors R21 and R22, respectively. A high temperature compensation voltage VH is applied to the inverting input terminal (−) of the comparator 53.
The other end of the switch SW1 is connected to the cathode of the diode D1, and the other end of the switch SW3 is grounded. The other end of the switch SW4 is connected to the output terminal of the comparator 52.
Each switch SW1 to SW4 is ON / OFF controlled as shown in FIG. 9B by the voltage level of the output voltage CPout of the comparator 51.

Hereinafter, the operation of the filter control unit shown in FIG. 9A will be described with reference to FIG.
First, as shown in FIG. 10A, the comparator 51 includes a voltage Vreg and a low temperature compensation voltage VL.
Compare with. In a period (temperature range) in which the low temperature compensation voltage VL is higher than the voltage Vreg, FIG.
As shown in (b), the output voltage CPout of the comparator 51 becomes L level.
When the output voltage CPout of the comparator 51 is L level, as shown in FIG.
Switch SW1 is on, switch SW2 is off, switch SW3 is on, switch SW4
Is turned off, and the input voltage of the non-inverting input terminal (+) of the comparator 53 becomes L level as shown in FIG. Therefore, the output voltage SV2 output from the comparator 53 becomes L level.
Next, when the low temperature compensation voltage VL input to the comparator 51 becomes lower than the voltage Vreg,
As shown in FIG. 10B, the output voltage CPout of the comparator 51 becomes H level.
When the output voltage CPout of the comparator 51 is H level, as shown in FIG.
Switch SW1 is off, switch SW2 is on, switch SW3 is off, switch SW4
Is turned on, and the input voltage V1 of the non-inverting input terminal (+) of the comparator 53 is shown in FIG.
As shown in FIG. At this time, the input voltage V1 of the non-inverting input terminal (+) of the comparator 53 is changed to the high temperature compensation voltage VH input to the inverting input terminal (−) of the comparator 53.
By setting the voltage level higher than the voltage level of the comparator 53, the output voltage S of the comparator 53 is set.
V2 becomes H level. Thereafter, as the ambient temperature rises, the voltage level of the high temperature compensation voltage VH inputted to the inverting input terminal (−) of the comparator 53 rises, and the high temperature compensation voltage VH becomes as shown in FIG. When the level of the input voltage V1 input to the non-inverting input terminal (+) of the comparator 53 becomes higher, the voltage level of the output voltage SV2 of the comparator 53 changes from H level to L level. As a result, the output voltage SV2 having a waveform as shown in FIG.
, That is, the filter control unit 41 that outputs the H-level output voltage SV2 only in a temperature range near room temperature where the voltage levels of the low-temperature compensation voltage VL and the high-temperature compensation voltage VH are constant clip voltage levels. Can be realized.

FIG. 11 is a cross-sectional view showing an example of the structure of a surface mount piezoelectric oscillator to which the piezoelectric oscillator of this embodiment is applied.
The piezoelectric oscillator shown in FIG. 11 includes an insulating container (package) 61 having a substantially H-shaped vertical cross-section having recesses 62 and 63 on the upper surface and the lower surface and four mounting terminals 65 on a rectangular annular bottom surface 64. And the piezoelectric vibration element 22 on the two upper surface side internal pads 66 provided in the upper surface side recess 62.
A metal lid 67 that hermetically seals the upper surface side recess 62 in a state where the upper two excitation electrodes are electrically connected to each other, and an upper surface side internal pad 66 disposed on the ceiling surface 63a of the lower surface side recess 63, And a lower surface side internal pad 68 electrically connected to each mounting terminal 65 by a predetermined wiring pattern, and an IC component 69 constituting an oscillation circuit mounted on the lower surface side internal pad 68.
The upper portion of the insulating container 61 having the upper surface side recess 62, the upper surface side internal pad 66, the crystal resonator element 22, and the metal lid 67 constitute a crystal resonator (piezoelectric resonator). In other words, the crystal resonator is electrically connected to the crystal resonator element X on the upper surface side inner pad 66 in the upper surface side recess 63 of the insulating container 61 made of an insulating material such as ceramic by using the conductive adhesive (conductive paste) 70. The metal lid 67 is electrically and mechanically connected to the conductor ring on the upper surface of the outer wall of the insulating container 61 by welding or the like, and the inside of the upper side recess 62 is hermetically sealed.
On the outer bottom surface of the insulating container 61, the temperature sensor 3, the temperature compensation voltage generator 4, the clip circuits 5, 6
, An oscillation circuit unit 7, a switching control unit 8, a temperature sensor phase switching unit 9, HPFs 10 and 42, a filter control unit 41, and other IC components 69 are mounted. When the piezoelectric oscillator is configured and miniaturized in this way, its heat capacity is reduced, and the temperature sensor 3 is sensitive to temperature fluctuations (fluctuations) due to ambient temperature changes and wind, and is a temperature compensated type. Although the output frequency of the piezoelectric oscillator fluctuates slightly (the frequency fluctuates), the piezoelectric oscillator 6 as in the present embodiment.
If the temperature fluctuation is canceled in 1, the temperature compensated piezoelectric oscillator can be reduced in size without causing the frequency fluctuation.
Note that the first and second variable capacitance elements ML and MH of the present embodiment have been described by taking MOS varactors as examples, but this is only an example, depending on the variable capacitance elements, variable capacitance diodes, or applied voltage. It is possible to use a semiconductor device whose capacitance is variable.
Considering the above-described various elements as the first and second variable capacitance elements ML and MH, it is possible to appropriately change the temperature compensation type piezoelectric oscillator or the oscillation circuit into an IC. Capacitance elements can be selected, and noise due to temperature fluctuation can be removed.

1 is a block diagram showing a configuration of a temperature compensated piezoelectric oscillator according to a first embodiment of the present invention. It is the figure which showed the characteristic of the switching control part. It is the figure which showed the characteristic of the temperature sensor phase switching part. It is a figure explaining the temperature compensation principle of the piezoelectric oscillator which concerns on embodiment of this invention. It is a figure explaining the temperature compensation principle of the piezoelectric oscillator which concerns on embodiment of this invention. It is a figure explaining the temperature compensation principle of the piezoelectric oscillator which concerns on embodiment of this invention. It is the figure which showed the temperature characteristic of the compensation voltage of the piezoelectric oscillator which concerns on embodiment of this invention. It is the block diagram which showed the structure of the temperature compensation type | mold piezoelectric oscillator which concerns on the 2nd Embodiment of this invention. It is the figure which showed the structural example of the filter control part. It is operation | movement explanatory drawing of the filter control part shown in FIG. It is sectional drawing which showed an example of the structure of the surface mount type piezoelectric oscillator to which the piezoelectric oscillator of this embodiment is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,40 ... Piezoelectric oscillator, 2 ... Constant voltage generation part, 3 ... Temperature sensor, 4 ... Temperature compensation voltage generation part, 5, 6 ... Clip circuit, 7 ... Oscillation circuit part, 8 ... Switching control part, 9 ... Temperature sensor Phase switching unit 10, 42 ... HPF, 21 ... oscillation circuit, 22 ... piezoelectric vibrator, 23 ... frequency temperature compensation circuit, 31a ... non-inverting amplifier, 31b ... inverting amplifier, 32, 43 ... switch circuit, 32a, 3
2b, 43a, 43b ... switch, 41 ... filter control unit, 51, 52, 53 ... comparator, 61 ... insulating container (package), 62, 63 ... recess, 64 ... bottom surface, 65 ... mounting terminal, 66 ... top surface side Internal pad, 67 ... Metal lid, 68 ... Lower surface side internal pad, 69 ... IC component, 70 ... Conductive adhesive

Claims (4)

A temperature sensor for detecting the temperature;
Based on the detection output of the temperature sensor, a low temperature compensation voltage that compensates for the temperature characteristics on the low temperature side centered on the normal temperature, and a temperature compensation voltage generator that generates a high temperature compensation voltage for compensating the temperature characteristics on the high temperature side,
A temperature sensor phase switching unit that switches and outputs the phase of the detection output of the temperature sensor when the detection output of the temperature sensor becomes a predetermined voltage or less;
A high-pass filter that receives the output voltage output from the temperature sensor phase switching unit as an input, passes only a high-frequency component included in the detection output of the temperature sensor, and superimposes it on a reference voltage;
An oscillation circuit, a piezoelectric vibrator, and a frequency temperature compensation circuit are connected in series. The frequency temperature compensation circuit is connected to a circuit in which a first variable capacitance element and a capacitor are connected in series with the first variable capacitance element. A circuit in which a second variable capacitance element having a reverse polarity is connected in parallel, and a low temperature compensation voltage is supplied to a connection point between the back gate of the first variable capacitance element and the capacitance, and the capacitance and the second variable capacitance element An oscillation circuit in which a high temperature compensation voltage is supplied to a connection point with the gate of the first variable capacitance element, and an output voltage from the high-pass filter is supplied to a connection point between the gate of the first variable capacitance element and the back gate of the second variable capacitance element. And
A piezoelectric oscillator comprising: A clip circuit that clips the low-temperature compensation voltage and the high-temperature compensation voltage to a predetermined voltage when the low-temperature compensation voltage and the high-temperature compensation voltage are less than or equal to a predetermined voltage;
A filter control unit that outputs a high level voltage when the low temperature compensation voltage or the high temperature compensation voltage is clipped to a predetermined voltage, and
When the input voltage from the filter control unit is at a high level, the high pass filter
Only the reference voltage is supplied to the oscillation circuit unit, and when the input voltage from the filter control unit is other than a high level, the oscillation is performed by superimposing a high-frequency component included in the detection output of the temperature sensor on the reference voltage. The piezoelectric oscillator according to claim 1, wherein the piezoelectric oscillator is supplied to a circuit unit. The temperature sensor phase switching unit outputs a detection voltage in phase with the detection output of the temperature sensor when the detection output of the temperature sensor is equal to or higher than a predetermined voltage, and the temperature when the detection output of the temperature sensor is equal to or lower than the predetermined voltage. The piezoelectric oscillator according to claim 1 or 2, wherein a detection voltage having a phase opposite to a detection output of the sensor is output. 4. The piezoelectric device according to claim 1, wherein the variable capacitance element is a MOS variable capacitance element, a varactor, a variable capacitance diode, or a semiconductor device whose capacitance is changed by an applied voltage. 5. Oscillator.

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