JP3446602B2 - Piezoelectric oscillator, oscillator adjustment system, and oscillator adjustment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric oscillator used for a radio communication device, a measuring instrument, and the like, and more particularly, to a piezoelectric oscillator suitable for shortening an oscillation start time at power-on, an oscillation frequency adjusting system, The present invention relates to a frequency adjustment method.

[0002]

2. Description of the Related Art Hitherto, a Colpitts type piezoelectric oscillation circuit using bipolar transistors as shown in FIG. 13 has been used as a piezoelectric oscillator used in a wireless communication device, a measuring instrument or the like. The piezoelectric oscillation circuit 13 is adapted to the oscillation frequency is determined by the piezoelectric resonator X and trimmer capacitor C _T and the like, the lower transistor Q1 is in oscillation, the upper transistor Q2 is used in the base-grounded amplifier.

This piezoelectric oscillation circuit is configured in the form of a cascode amplifier. Since the collector of the transistor Q1 has low impedance, the capacitance on the collector side is multiplied by the current amplification factor h _fe and the Miller capacitance appears on the base side. Can be reduced. Therefore, it is suitable for high-frequency oscillation. Further, since the current amplification factor h _fe of the transistors are varied, in the piezoelectric oscillator that does not use transistors Q2, to absorb the variation of the Miller capacitance increase the variable range of the trimmer capacitor C _T to obtain the desired oscillation frequency it was necessary to, in the piezoelectric oscillation circuit, there is an advantage that it is possible to use a narrow variable range as trimmer capacitor C _T.

[0004]

By the way, in the conventional piezoelectric oscillation circuit, in order to take advantage of the cascode amplification, it is necessary that the emitter side of the transistor Q2 has a low impedance in a desired frequency band. . The capacitor C is provided for this purpose, and forms a low-pass filter on the base side of the transistor Q2 together with the bias resistor R1 and the like. Here, considering the case where the power is supplied to the conventional piezoelectric oscillation circuit,
The base voltage of the transistor Q2 does not immediately reach a steady state, but rather a bias resistor R1 and a capacitor C2.
It gradually increases according to the time constant determined by the above. Therefore, it takes time before the transistors Q1 and Q2 are normally biased and can operate as an oscillation circuit. Therefore, immediately after the power is turned on, the initial current flowing through the piezoelectric vibrator X becomes small, and the oscillation starting time becomes long. For this reason, the conventional piezoelectric oscillation circuit has disadvantages such as a delay in amplitude growth and frequency stabilization after power-on, and a delay in the start of oscillation.

The present invention has been made in view of the above circumstances, and has as its object to provide a piezoelectric oscillation circuit that has a simple configuration and reduces the oscillation start-up time. Also,
An object of the present invention is to provide a piezoelectric oscillation circuit capable of accurately determining a center frequency. It is another object of the present invention to provide a piezoelectric oscillation circuit in which the oscillation start-up time is further reduced by absorbing the variation of the elements.

[0006]

According to the first aspect of the present invention, there is provided an oscillation circuit having a piezoelectric vibrator in an oscillation loop, and detecting the start of power supply to the oscillation circuit. Te, a pulse generating circuit for injecting a pulse after a predetermined time has elapsed from the start of power supply to the oscillation loop, said Pal
Write and read data that controls the timing of
The pulse generation circuit, comprising:
Is based on the data read from the data storage circuit.
Then, the pulse is generated .

Further, in the invention according to claim 2,
An oscillation circuit having a piezoelectric vibrator in an oscillation loop;
Detects the start of power supply to the vibration circuit
Pulse generation for injecting a pulse into the oscillation loop after elapse
A circuit having a predetermined capacitance and the piezoelectric vibration
Fixed connection capacitance element connected to the
A plurality of selective connection capacitance elements having a capacitance;
Of the selected connection capacitance elements, the specific selection connection capacitance element
Connected in parallel to the fixed connection capacitance element
And the fixed connection capacitance element of the selection connection capacitance element
Frequency control data for controlling connection / disconnection to be performed,
And a pulse system for controlling the generation timing of the pulse
Data storage circuit for storing control data and external adjustment
To the data storage circuit based on the frequency control data.
To store the frequency control data,
Frequency control data or the frequency control data
While controlling the capacitance connection circuit based on the
The data storage circuit based on the adjustment pulse control data;
The pulse control data is stored in advance in
Adjustment pulse control data or the pulse control data
Connection control circuit for controlling the pulse generation circuit based on the
And a road .

[0008]

[0009]

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

Further, in the invention according to claim 3 , the contract
3. An oscillator adjustment system for adjusting the generation timing of the pulse in the piezoelectric oscillator according to claim 2 , wherein power supply means for supplying power to the oscillation circuit, oscillation state detection means for detecting an oscillation state of the oscillation circuit, and power supply Measuring means for measuring an oscillation start time from when power is supplied by the means to when the oscillation state is detected by the oscillation state detecting means, and the adjusting means for shortening the oscillation start time measured by the measuring means. outputs a pulse control data, the de the adjustment pulse control data when the most the oscillation start time becomes shorter as the pulse control data
And an adjustment data output means for controlling the connection control circuit so as to store the data in the data storage circuit .

Further, in the invention according to claim 4, the contract
In the oscillator adjusting method for adjusting the generation timing of the pulse in the piezoelectric oscillator according to claim 2, a step of supplying power to the oscillation circuit, a step of detecting an oscillation state of the oscillation circuit, and after the power supply is started. Measuring an oscillation start time until an oscillation state is detected, and outputting the adjustment pulse control data so as to shorten the oscillation start time; and adjusting the adjustment pulse when the oscillation start time is the shortest. Controlling the connection control circuit such that control data is stored as the pulse control data in the data storage circuit .

[0020]

DETAILED DESCRIPTION OF THE INVENTION First Embodiment Hereinafter, a piezoelectric oscillation circuit according to an embodiment of the present invention will be described with reference to the drawings. 1. Configuration of First Embodiment FIG. 1 is a circuit diagram of a piezoelectric oscillation circuit according to the first embodiment. In the figure, a piezoelectric oscillation circuit 1 includes an oscillation unit 10 and a pulse generation unit 20. The oscillating unit 10 has the same configuration as the conventional piezoelectric oscillating circuit shown in FIG. 13, and thus the description thereof is omitted here and the pulse generating unit 20 will be described.

The pulse generator 20 comprises a first monostable multivibrator MM1 and a second monostable multivibrator MM2. The first monostable multivibrator MM1 includes a capacitor Ca and a resistor Ra.
The delay time t1 of the second monostable multivibrator MM2 is set by the capacitor Cb and the resistor Rb.

First monostable multivibrator MM1
Detects the rise of the power supply voltage Vcc, rises from the low level to the high level, maintains the high level for a certain period of time, falls to the low level, and thereafter generates an output pulse P that maintains the low level. Further, the second monostable multivibrator MM2 detects the falling edge of the output pulse P, rises from a low level to a high level, keeps the high level for a certain period of time, falls to a low level, and then falls to a low level. A trigger pulse TP for maintaining the level is generated. In this case, the delay time t of the first and second monostable multivibrators MM1 and MM2
1, t2 are given as high-level periods of the output pulse P and the trigger pulse TP, respectively.

Here, the delay time t1 is selected by an experiment so that the oscillation can be reliably started and the start-up time can be minimized. On the other hand, the delay time t2 is set to a very short time so as to excite the oscillation. Is done. Thus, the trigger pulse TP produced is adapted to be injected into the connection point of the trimmer capacitor C _T and the piezoelectric vibrator X. For this reason, when the bias voltages of the transistors Q1 and Q2 are stabilized to some extent, the trigger pulse TP can be given into the oscillation loop, and thereby a large initial current can flow through the piezoelectric vibrator X, and the oscillation starts. It is possible to reduce the time and settling time until the oscillation is stabilized.

2. 2. Operation of First Embodiment FIG. 2 is a timing chart of the piezoelectric oscillation circuit according to the first embodiment. The operation of the piezoelectric oscillation circuit 1 will be described with reference to FIG. First, assuming that power is supplied to the piezoelectric oscillation circuit 1 at time T1, the power supply voltage Vcc rises at time T1, as shown in FIG.
Then, the rising edge e1 is detected by the first monostable multivibrator MM1, and an output pulse P delayed by the time t1 is generated as shown in FIG. 2B.
This is followed by a second monostable multivibrator MM2
Detects a falling edge e2 of the output pulse P and generates a trigger pulse TP having a pulse width t2 (see FIG. 2C), the trigger pulse TP is supplied to one end of the piezoelectric vibrator X.

In this case, the delay time t1 is set so that the oscillation can be started reliably and the start-up time can be minimized as described above. Therefore, the oscillation unit 10 starts the oscillation by the trigger pulse TP. , An oscillation signal SOSC as shown in FIG. Here, for comparison, FIG. 2E shows an oscillation signal SOSC ^′ when the trigger pulse TP is not injected. A comparison between FIG. 2D and FIG. 2E shows that the injection of the trigger pulse TP starts the oscillation earlier by the time t3. In addition, FIG.
As shown in (e), the amplitudes of the oscillation signals SOSC _and SOSC ^′ gradually increase, and the oscillation frequency stabilizes. However, the time from when the power is turned on until the stable oscillation signals SOSC _and SOSC ^′ are generated also has the trigger pulse TP. It can be seen that the shorter the time, the shorter the injection time.

For example, t1 = 50 μsec, t2 = 5 μsec
The time required for the frequency deviation to converge within 0.1 ppm is 5.89 ms without the trigger pulse TP.
The present inventor has confirmed by experiment that the time becomes 2.45 msec with ec and a trigger pulse TP. That is, by injecting the trigger pulse TP, the stable oscillation signal S
The time to obtain OSC can be reduced by about 60%.

As described above, according to the present embodiment, the trigger pulse TP is injected into the oscillation loop after a predetermined time has elapsed since the power was turned on, so that the time until the start of oscillation can be shortened, and The time until the oscillation signal SOSC becomes stable can be shortened. Therefore, if the piezoelectric oscillation circuit 1 is applied to a wireless communication device or a measuring device, the time required for stabilizing the device can be reduced.

B. Second embodiment 1. Second Embodiment Configuration 1-1: Overall Configuration The second embodiment relates to a voltage-controlled piezoelectric oscillation circuit suitable for shortening the time until the oscillation frequency stabilizes and the oscillation startup time. FIG. 3 is a circuit diagram of a voltage-controlled piezoelectric oscillation circuit according to the second embodiment.

In the figure, a voltage control type piezoelectric oscillation circuit 2
Is composed of a pulse generator 20 and an oscillator 30. The configuration of the pulse generator 20 is the same as that of the first embodiment described above, and the configuration of the oscillator 30 is different from that of the oscillator 10 of the first embodiment.

In the oscillation section 30, a control voltage VC is applied to the frequency control terminal VC to change the oscillation frequency fOSC of the oscillation signal SOSC output from the output terminal OUT. Further, the control voltage VC is supplied via an input resistor Ri having one end connected to the frequency control terminal VC, whereby an oscillation frequency control circuit (not shown) connected to the frequency control terminal VC is provided. Can be loosely coupled to the oscillation circuit 30.

Next, one end of a piezoelectric vibrator X is connected to the other end of the input resistor Ri so that a trigger pulse TP is supplied thereto via a coupling capacitor Cc for cutting a DC component. Has become. A cathode terminal of a variable capacitance diode (hereinafter, referred to as a varicap) Cv functioning as a variable reactance element is connected to an intermediate connection point between the input resistance Ri and the piezoelectric vibrator X. Between the anode terminal of the varicap Cv and the low-potential-side power supply GND, a capacitance array CARY having a function equivalent to one capacitor having a desired capacitance is connected. In addition,
The capacity array CARY functions as a capacity array unit,
The detailed configuration will be described later.

Next, the frequency control data DCTL is stored in the memory 21, and based on the frequency control data DCTL, the switches S1 to S1 of the capacitance array CARY during normal operation.
On / off control of n is performed.

Next, the control circuit 22 has adjustment data input terminals T1 to T3, and switches S1 to Sn and a memory 21.
And connected to. The control circuit 22 performs on / off control of the switches S1 to Sn forming the capacitance array CARY based on the adjustment frequency data DADJ input from the adjustment data input terminals T1 to T3 during the adjustment operation. The control data DCTL is stored in the memory 21 and, at the time of a normal operation, on / off control of the switches S1 to Sn is performed based on the frequency control data DCTL stored in the memory 21.

Next, the varicap Cv and the capacitance array CARY
A bias resistor RX is provided at the intermediate connection point between the power supply and the low-potential-side power supply GND, whereby the varicap Cv is reverse-biased, and the varicap Cv exhibits a capacitance value corresponding to the control voltage VC.

Next, the high potential power supply VCC and the low potential power supply G
Between ND, first to third bias resistors R1 to R3 are provided. The connection point between the first bias resistor R1 and the second bias resistor R2 is connected to the base terminal of the transistor Q2, and the connection point between the second bias resistor R2 and the third bias resistor R3 is connected to the base terminal of the transistor Q1. ing.

Next, the base terminal of the transistor Q2 is
It is grounded via a bypass capacitor C. For this reason, the transistor Q2 forms a common base amplifier, and its emitter terminal is connected to the collector terminal of the transistor Q1. The emitter terminal of the transistor Q1 is connected to the low potential power supply GND via the emitter resistor Re and the second oscillation capacitor C02, and the emitter voltage is positively fed back to the base terminal via the first oscillation capacitor C01. It is supposed to be.

In the above configuration, when the power Vcc is turned on, the pulse generator 20 detects the power-on and generates a trigger pulse TP. The DC component of the trigger pulse TP is cut by the coupling capacitor Cc, and the trigger pulse TP is supplied to the connection point between the piezoelectric vibrator X and the varicap Cv. As a result, as in the first embodiment, the oscillation starting time is shortened, and the time until stable oscillation is obtained is shortened.

1-2: Constitution of Capacitance Array CARY The capacitance array CARY has one end connected to the anode terminal of the varicap Cv, and the other end connected to the low potential side power supply GND, and functions as a fixed capacitance element. Base capacitor C0 to secure the minimum capacity of CARY
And n capacitors CX (X = 1) functioning as selective connection capacitance elements for making the capacitance of the capacitance array CARY variable.
.. N) and the corresponding capacitor is a base capacitor C0.
And a switch SX (X = 1 to n) for parallel connection to the power supply.

In this case, the capacitors C1 to Cn
May be the same or different from each other. If the further different from each other, it is possible to set a wide range of capacity is set such that the 2 ^X times the basic capacity to set the capacitance of each capacitor CX in advance.

When the voltage-controlled piezoelectric oscillation circuit is formed into an IC, the switches S1 to Sn may have, for example, the following configurations depending on the semiconductor manufacturing process to be used. When a bipolar process is used as a semiconductor manufacturing process, the switches S1 to Sn have a bipolar transistor configuration as shown in FIG. When a CMOS process is used as a semiconductor manufacturing process, the switches S1 to Sn are configured as MOS transistors as shown in FIG. Bipolar & CMOS mixed process which is actively used as a semiconductor manufacturing process for high frequency ICs
When the (Bi-CMOS process) is used, the switches S1 to Sn can adopt either the bipolar transistor configuration shown in FIG. 4 or the MOS transistor configuration shown in FIG. However, from the viewpoint of reducing current consumption, it is more advantageous to adopt a MOS transistor configuration that does not require a steady current flow to turn on the transistor. Because the MOS transistor is a voltage control element, it is sufficient to apply a voltage of a level sufficient to turn on the MOS transistor to the gate terminal, and there is no current constantly flowing from the gate terminal to the low potential side power supply GND. It is. On the other hand, if a bipolar transistor configuration is used, in order to reduce the on-resistance of the transistor in the selected state, the base terminal-
This is because it is necessary to supply a sufficient current between the low-potential-side power supply GND. Further, it is preferable that the piezoelectric vibrator X is a crystal vibrator that is physically and chemically stable and exhibits excellent stability particularly against temperature fluctuation. In this case, the memory 21 is an EEPROM, an EPR
It can be constituted by a nonvolatile semiconductor memory represented by an OM, a fuse type ROM and the like.

1-3: System for Automatically Adjusting Center Oscillation Frequency f0 FIG. 6 is a block diagram showing the schematic configuration of the system for automatically adjusting the center oscillation frequency f0 of a voltage-controlled piezoelectric oscillation circuit. The automatic adjustment system A includes a voltage-controlled piezoelectric oscillation circuit 2, a reference voltage application device 31, and a center oscillation frequency (f0) adjustment device 32. First, the reference voltage applying device 31
Is configured to output a calibrated reference control voltage VCREF corresponding to a predetermined reference center oscillation frequency f0REF, and the reference control voltage VCREF is supplied to a frequency control terminal VC.

Next, the center oscillation frequency adjusting device 32 is composed of a personal computer or the like, is connected to the output terminal OUT of the voltage control type piezoelectric oscillation circuit 2, and applies a calibrated reference control voltage VCREF to the frequency control terminal VC. In this state, the oscillation frequency fOSC (= corresponding to the center oscillation frequency f0) of the oscillation signal SOSC output from the output terminal OUT is detected and compared with a preset reference center oscillation frequency f0REF, thereby forming the capacitance array CARY. Adjustment frequency data DADJ for controlling on / off of the switch is generated, and the voltage control type piezoelectric oscillation circuit 2 is connected via adjustment terminals T1 to T3.
Is output.

2. Operation 2-1 of Second Embodiment Operation at Adjustment Next, the adjustment operation of the oscillation frequency fOSC of the oscillation signal SOSC using the automatic adjustment system A will be described. First, the reference voltage applying device 31 applies a calibrated reference control voltage VCREF corresponding to a predetermined reference center oscillation frequency f0REF to a frequency control terminal VREF.
Apply to C. In parallel with the application of the reference control voltage VCREF, the center oscillation frequency adjusting device 32 detects the oscillation frequency fOSC (= corresponding to the center oscillation frequency f0) of the oscillation signal SOSC output from the output terminal OUT. Then, it is compared with a preset reference center oscillation frequency f0REF corresponding to the reference control voltage VCREF.

In this case, the center oscillation frequency adjusting device 32
Is a switch that calculates the load capacitance CL on the oscillation circuit side so that the frequency difference between the reference center oscillation frequency f0REF and the oscillation frequency fOSC at the reference control voltage VCREF becomes substantially zero, and based on the calculation result, a switch that constitutes the capacitance array CARY , And generates adjustment frequency data DADJ for controlling the on / off operation of the piezoelectric oscillation circuit 2 via the adjustment terminals T1 to T3. As a result, the control circuit 22 of the voltage controlled piezoelectric oscillation circuit 2 adjusts the adjustment data input terminals T1 to T1.
On / off of the switches S1 to Sn constituting the capacitance array CARY based on the adjustment frequency data DADJ input from T3.
Performs off control.

Thus, the center oscillation frequency adjusting device 32 again detects the oscillation frequency fOSC (= corresponding to the center oscillation frequency f0) of the oscillation signal SOSC output from the output terminal OUT, and corresponds to the reference control voltage VCREF. The same processing is repeated with a reference center oscillation frequency f0REF set in advance and the frequency difference becomes substantially zero. Then, when the frequency difference becomes substantially zero, the adjustment frequency data DADJ is held for a predetermined period or more. As a result, the control circuit 22 detects that the automatic adjustment of the center oscillation frequency f0 has been completed, and stores the frequency control data DCTL corresponding to the adjustment frequency data DADJ at the end of the adjustment in the memory 21.

The memory 21 stores the frequency control data DCL stored by the control circuit 22 next to the frequency control data DCL.
Until the TL is updated, it will be kept. In the above description, the control circuit 22 independently detects the end of the automatic adjustment, and stores in the memory the frequency control data DCTL corresponding to the adjustment frequency data DADJ at the end of the adjustment.
However, the oscillation center frequency adjustment device 32 is configured to notify that the adjustment has been completed by including the adjustment in the adjustment data DADJ, and at the time of this notification, the control circuit 22 adjusts the adjustment. The frequency control data DCTL corresponding to the frequency data DADJ for use may be stored in the memory 21.

2-2: Normal Operation Next, the normal operation of the voltage controlled piezoelectric oscillation circuit 2 will be described with reference to FIG. When the power of the oscillation unit 30 is turned on, the pulse generation unit 20 detects the power-on timing by detecting the voltage of the high-potential-side power supply VCC. Further, the control circuit 22 reads out the frequency control data DCTL stored in the memory 21, turns on only the switch SX corresponding to the frequency control data DCTL, and turns off the other switches.

Thereafter, the pulse generator 20 generates a trigger pulse TP after a lapse of a predetermined time, and applies the trigger pulse TP to the piezoelectric vibrator X via the coupling capacitor Cc. Then
A large initial current flows through the piezoelectric vibrator X to excite oscillation. Here, the timing at which the trigger pulse TP is generated is set so as to minimize the oscillation start-up time, as described above, so that the time from power-on to the start of oscillation can be shortened. It is possible to shorten the time until the data becomes stable. The data storage circuit that can write and read data for controlling the pulse generation timing may be a memory that stores frequency control data.

Then, an oscillation signal SOSC having an oscillation frequency fOSC corresponding to the control voltage VC with the center oscillation frequency f0 adjusted by the adjustment operation as the center is output from the output terminal OUT.

In this case, the control circuit 22 of the voltage-controlled piezoelectric oscillation circuit 2 turns on all the switches S1 to Sn constituting the capacitance array CARY once (on) when power is turned on. Is also good. This is the capacity array CARY
Since the impedance of is minimized and oscillation becomes easy,
This is because the oscillation frequency fOSC of the oscillation signal SOSC output from the output terminal OUT of the voltage control type piezoelectric oscillation circuit 2 is quickly brought to a stable state. As a result, the oscillation start time can be further reduced. When a preset time has elapsed, the control circuit 22 reads the frequency control data D from the memory 21.
CTL is read, and the switch SX is controlled based on the frequency control data DCTL. As a result, the oscillation signal SOSC having the oscillation frequency fOSC corresponding to the control voltage Vc and centering on the center oscillation frequency f0 adjusted by the adjustment operation is output.
It will be output from OUT.

3. Effect of the Second Embodiment Even if the piezoelectric vibrator has variations, it is easy to match the oscillation frequency fOSC to the reference center frequency f0ref when assembled as a voltage-controlled piezoelectric oscillator. Therefore, the manufacturing standard of the piezoelectric vibrator can be relaxed, the cost of the piezoelectric vibrator can be reduced, and the manufacturing cost of the voltage controlled piezoelectric oscillator can be reduced.
Further, since the frequency variable amount by the varicap is easily ensured, the adjustment is facilitated. Further, since there is little difference in the variable range of the fosc-Vc characteristic depending on the capacitance set value of the capacitance array CARY, a desired voltage controlled piezoelectric oscillator can be easily configured.

By using the capacitance array CARY,
The voltage-controlled piezoelectric oscillator can be configured without a trimmer, one external component can be reduced, and the assembly cost can be reduced. By using a capacitor array that is cheaper than a trimmer, a low-cost voltage-controlled piezoelectric oscillator can be realized. Conventional piezoelectric oscillators using trimmers had a limit in miniaturization because the trimmers had mechanically operating parts. However, the capacitance array CARY can be built into ICs, and it has been necessary to reduce the size of voltage-controlled piezoelectric oscillators. This is advantageous.

Compared with a conventional piezoelectric oscillator using a trimmer, a voltage-controlled piezoelectric oscillator using a capacitance array CARY is stable in terms of aging and operating mechanism, and can stabilize the operation of a piezoelectric oscillation circuit. Becomes possible. The oscillation center frequency adjustment work can be performed only by electrical adjustment by the center oscillation frequency adjustment device 32 outputting the adjustment data DADJ which is digital data, and it is necessary to perform mechanical adjustment as in the related art. , The center oscillation frequency adjustment time can be shortened.
It is possible to reduce the manufacturing cost of the voltage controlled piezoelectric oscillator. Further, unlike the related art, a complicated and expensive servo mechanism for adjusting the trimmer is not required, so that it is possible to reduce investment in manufacturing equipment.

4. Modification of Second Embodiment In the above description, the piezoelectric vibrator X and the varicap Cv are handled as discrete components. However, the piezoelectric vibrator X and the varicap Cv are connected in series, and are molded or sealed. If it is configured to be housed in the package, the assembly process of the voltage controlled oscillator can be simplified.

Further, the base capacitor C0 is not configured as a capacitance array CARY, and only the capacitors C1 to Cn and the switches S1 to Sn are defined as a capacitance array BARY '.
The ARY ', the memory 21, and the control circuit 22 may be externally connected as an integrated IC. Furthermore, it is also possible to configure so that only the capacitance array CARY or the capacitance array BARY is externally attached as an IC. This makes it possible to construct a voltage controlled piezoelectric oscillation circuit having various fOSC-Vc characteristics simply by newly creating a capacitance array BARY. In the above description, the switches S1 to Sn forming the capacitance array CARY are configured by transistors. However, if high precision is not desired, the switches S1 to Sn may be configured by fuse elements, and when the adjustment is performed, It is also possible to adopt a configuration in which the switch is definitely cut off.

C. Third Embodiment In the first and second embodiments described above, the trigger pulse T
The generation timing of P is not adjusted for each individual piezoelectric oscillation circuit, but is set to a representative value obtained by an experiment. On the other hand, in the third embodiment, the time from when the power is turned on to when the trigger pulse TP is generated is adjusted for each piezoelectric oscillation circuit so that the oscillation start-up time can be minimized.

1. Configuration 1-1 of Third Embodiment: Overall Configuration FIG. 7 shows a circuit diagram of a voltage-controlled piezoelectric oscillation circuit according to the third embodiment. The voltage-controlled piezoelectric oscillation circuit 3 is different from the voltage-controlled piezoelectric oscillation circuit 3 in that the control circuit 22 controls the pulse generation unit 20 ′ and the memory 21 controls the generation timing of the trigger pulse TP in addition to the frequency control data DCTL for frequency adjustment. This is the same as the voltage-controlled piezoelectric oscillation circuit 2 of the second embodiment except that DCTL 'is stored.

1-2: Configuration of Pulse Generator Next, FIG. 8 shows a pulse generator 20 'according to the third embodiment.
FIG. This pulse generator 20 'uses a capacitance array CARY' instead of the capacitor Ca, as shown in FIG.
Is different from the pulse generator 20 of the first embodiment shown in FIG. Delay time t1 of first monostable multivibrator MM1
(See FIG. 2 (b)) is determined by the value of the capacitance array CARY 'and the resistance Ra determined according to the on / off of the switch SX'. Therefore, by controlling the on / off of the switch SX ', the trigger pulse TP Can be adjusted.

1-3: Automatic Adjustment System FIG. 9 is a schematic block diagram of an automatic adjustment system for a voltage-controlled piezoelectric oscillation circuit. The automatic adjustment system B includes a voltage-controlled piezoelectric oscillation circuit 3, a reference voltage application device 31, a power supply device 33, and an adjustment device 32 '.
First, the reference voltage applying device 31 is configured to output a calibrated reference control voltage VCREF corresponding to a predetermined reference center oscillation frequency f0REF, so that the reference control voltage VCREF is supplied to the frequency control terminal VC. Has become. The power supply device 33 is configured to perform power supply based on a control signal from the adjustment device 32 ′.

Next, the adjusting device 32 'has a function of adjusting the generation timing of the trigger pulse TP in addition to the function of the center oscillation frequency adjusting device 32 of the second embodiment.
Specifically, after adjusting the center frequency, a control signal is supplied to the power supply device 33 to supply power to the voltage controlled piezoelectric oscillation circuit 3. Then, by detecting the amplitude or frequency of the oscillation signal SOSC, the oscillation start-up time from power-on to the start of oscillation is detected, and the on / off of the switch SX 'constituting the capacitance array CARY' is minimized so as to minimize this. Is generated and output to the voltage-controlled piezoelectric oscillation circuit 3 via the adjustment terminals T1 to T3.

[0061] 2. Operation 2-1 of Third Embodiment Operation at Adjustment Next, an adjustment operation using the automatic adjustment system B will be described. First, the adjustment operation of the center oscillation frequency is performed as in the second embodiment. Next, an operation of adjusting the generation timing of the trigger pulse TP is performed. In this case, the reference voltage applying device 3
1 applies the reference control voltage VCREF to the frequency control terminal VC. Thereafter, the adjusting device 32 ′ supplies the initial value adjusting pulse data DADJ ′ to the adjusting terminals T 1 to T 3, controls the power supply device 33, and supplies power to the voltage-controlled piezoelectric oscillation circuit 3. Do. Next, the adjusting device 32 '
The oscillation signal SOSC output from the output terminal OUT is detected, and
Measure the oscillation start time.

Thereafter, the oscillation start time is repeatedly measured while shifting the value of the adjustment pulse data DADJ ', and the adjustment pulse data DADJ' that minimizes the oscillation start time is obtained. Thereafter, the voltage control type piezoelectric oscillation circuit 3 is notified of the final adjustment pulse data DADJ ', including the effect that the adjustment has been completed. Then, the control circuit 22 outputs the adjustment pulse data DAD
The pulse control data DCTL 'corresponding to J' is stored in the memory 21.

2-2: Normal Operation Next, the normal operation of the voltage-controlled piezoelectric oscillation circuit 3 will be described with reference to FIG. When the power of the oscillation unit 30 is turned on, the control circuit 22 reads out the pulse control data DCTL ′ stored in the memory 21 and
On / off of the switch SX 'of 0' is controlled. As a result, the generation timing of the trigger pulse TP unique to the voltage-controlled piezoelectric oscillation circuit 3 is set.

The control circuit 22 reads out the frequency control data DCTL stored in the memory 21 and sets a capacitance value specific to the voltage controlled piezoelectric oscillation circuit 3. This makes it possible to use an oscillation center frequency that has been adjusted.

Next, when the pulse generator 20 'detects the power-on timing by detecting the voltage of the high-potential power supply VCC, the trigger pulse TP
Is applied to the piezoelectric vibrator X via the coupling capacitor Cc. Then, a large initial current flows through the piezoelectric vibrator X, and oscillation is excited. Here, the trigger pulse T
The timing at which P is generated is set so as to minimize the oscillation start-up time as described above, so that the time from power-on to the start of oscillation can be shortened, and the time until oscillation stabilizes can be reduced. Time can be reduced.

Then, the oscillation signal SOSC having the oscillation frequency fOSC corresponding to the control voltage VC with the center oscillation frequency f0 adjusted by the adjustment operation as the center is output from the output terminal OUT.

As described above, in the third embodiment, the generation timing of the trigger pulse TP can be automatically adjusted.
Oscillation start-up time can be further reduced. Also,
Even if the resistance Ra and the capacitor Ca vary, it becomes easy to match the time constant when assembled as a voltage-controlled piezoelectric oscillator. Therefore, the manufacturing standard of the resistor Ra can be relaxed, the cost can be reduced, and the manufacturing cost of the voltage controlled piezoelectric oscillator can be reduced. Although the adjustment of the trigger pulse generation timing has been described by adjusting the capacitance value of the capacitance array CARY ′, the same applies when the capacitance array is Ca and Ra is the resistance array. In this case, even if Ca varies,
When assembled as a voltage-controlled piezoelectric oscillator, it is easy to match the time constant.

The frequency control data D for frequency adjustment
Since the pulse control data DCTL 'is stored in the memory 21 for storing the CTL, the storage means can be shared. In addition, the pulse generator 20 'is controlled by the control circuit 22 for controlling the capacitance array CARY of the oscillator 30, so that a special configuration is not added.
The generation timing of the trigger pulse TP can be automatically adjusted.

D. Modifications The present invention is not limited to the above-described embodiment, and for example, the following various modifications are possible. (1) In each of the embodiments described above, the oscillating units 10 and 30 are configured in a cascode format. However, the present invention is not limited to this, and the transistor Q2, the resistor R1, and the capacitor C are omitted. Is also good. In this case, for example, in FIG. 3, the collector resistor Rc may be connected to the collector of the transistor Q1, and one end of the resistor R2 may be connected to the power supply VCC.

(2) In each embodiment, as the configuration of the capacitance array CARY, n capacitors CX (X = 1 to n) functioning as selective connection capacitance elements for making the capacitance of the capacitance array CARY variable. Was provided, but
As shown in FIG. 10, a capacitor CX (= selection connection capacitance element) is composed of a plurality of sub-capacitors CX0 and CX1 to CXm (= subselection connection capacitance element, m = natural number) including a base sub-capacitor CX0. The capacitors CX1 to CXm may be configured to switch the corresponding sub-connection switches SX1 to SXm, and the sub-capacitors CX0 and CX1 to CXm may be connected or disconnected to adjust the capacitance of the capacitance array CARY. As a result, fine adjustment of the capacitance value can be performed.

(3) In each embodiment, the case where the varicap Cv and the capacitor array CARY are connected in series has been described. However, the configuration is such that the capacitor array CARY is connected in parallel to the varicap Cv. Is also possible.

(4) In each of the embodiments, the mounting state of the elements constituting the piezoelectric oscillator has not been described. For example, the piezoelectric oscillator may be configured as shown in FIG. In this case, the components other than the piezoelectric vibrator X and the varicap Cv are configured as a one-chip IC 51, and the one-chip IC 51, the piezoelectric vibrator X and the varicap Cv are molded and sealed. Such a configuration is feasible because the one-chip IC, the piezoelectric vibrator X, and the varicap Cv are molded and sealed because the adjustment range of the oscillation center frequency f0 by the capacitance array CARY can be widened. This is because, even in the state, it is possible to easily absorb variations in the piezoelectric vibrator X and the varicap Cv and obtain a desired oscillation center frequency f0. As a result, the number of parts can be reduced, and the number of assembly steps and the manufacturing cost can be reduced.

(5) In the above-described modification (4), the components other than the piezoelectric vibrator X and the varicap _CV are configured as a one-chip IC 51, and the one-chip IC 51,
Although the piezoelectric vibrator X and the varicap C _V are molded and sealed, in the embodiment shown in FIG. 12 , the components (including the varicap C _V ) except the piezoelectric vibrator X are used as the one-chip IC 52. And one-chip I
C and the piezoelectric vibrator X are molded and sealed. As a result, the number of parts can be further reduced, and the number of assembly steps and the manufacturing cost can be reduced.

(6) In each of the above-described embodiments, the pulse generators 20 and 20 ′ are configured using the monostable multivibrators MM1 and MM2. However, the present invention is not limited to this. The start of power supply to the oscillating unit is detected and the trigger pulse TP
May be injected into the oscillation loop. For example, the pulse generators 20 and 20 ′ may be configured using a counter circuit. In this case, the counter circuit measures an external clock from the start of power supply to the oscillation unit, and generates a ripple carry signal when the measurement result reaches a certain value. The ripple carry signal is used as a trigger pulse TP. It may be used. When a counter circuit is used, an external clock is required. However, many electronic devices operate with a plurality of clock signals. In such a device, an unnecessary clock generator may be turned off in order to reduce power consumption. In such a case, the pulse generators 20 and 20 'using a counter circuit are preferable.

[0075]

As described above, according to the present invention, the pulse is injected into the oscillation loop after a lapse of a predetermined time from the start of the power supply to the oscillation section. Therefore, the oscillation start time and the time until the oscillation is stabilized are obtained. Can be greatly reduced. In addition, even when the piezoelectric vibrators vary, the center oscillation frequency f0 can be easily adjusted when assembled as an oscillation circuit. Therefore, the manufacturing standard of the piezoelectric vibrator is relaxed, the cost of the piezoelectric vibrator can be reduced, and the cost of the piezoelectric oscillator can be further reduced. By using the capacitor array, the voltage-controlled piezoelectric oscillator can be configured without a trimmer, one external component can be reduced, and the assembly cost can be reduced. In addition, the oscillation center frequency adjustment work can be performed only by electrical adjustment, and it is not necessary to perform mechanical adjustment as in the related art, so that the center oscillation frequency adjustment time can be shortened, and consequently, the voltage control can be performed. It is possible to reduce the manufacturing cost of the piezoelectric oscillator. Further, since the timing of supplying the pulse can be automatically adjusted, the variation of the element can be absorbed, and the oscillation start time and the time until the oscillation is stabilized can be further reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a piezoelectric oscillation circuit according to a first embodiment of the present invention.

FIG. 2 is a timing chart of the piezoelectric oscillation circuit according to the embodiment.

FIG. 3 is a circuit diagram of a voltage-controlled piezoelectric oscillation circuit according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram in the case where switches constituting a capacitance array are constituted by bipolar transistors.

FIG. 5 is an explanatory diagram in the case where switches constituting a capacitance array are constituted by MOS transistors.

FIG. 6 is a configuration diagram of a center oscillation frequency adjustment system according to the embodiment.

FIG. 7 is a configuration diagram of a voltage-controlled piezoelectric oscillation circuit according to a third embodiment.

FIG. 8 is a circuit diagram of a pulse generator of the embodiment.

FIG. 9 is a configuration diagram of an adjustment system according to the embodiment.

FIG. 10 is a diagram showing a configuration example of a capacitance array according to a modification.

FIG. 11 is a perspective view of a voltage-controlled piezoelectric oscillation circuit according to a modification.

FIG. 12 is a perspective view of a voltage-controlled piezoelectric oscillation circuit according to a modification.

FIG. 13 is a circuit diagram of a conventional piezoelectric oscillation circuit.

[Explanation of symbols]

1: Piezoelectric oscillation circuit 2,3 ... Voltage-controlled piezoelectric oscillation circuit 20 pulse generator 21 ... Memory 22 ... Control circuit 31 ... Reference voltage applying device 32: oscillation center frequency adjustment device 32 '... Adjustment device CARY ... Capacitance array C1 to Cn: Capacitor (selective connection capacitance element) C0: Base capacitor (fixed connection capacitance element) DADJ, DADJ ': Adjustment data DCTL, DCTL ': Control data SOSC: oscillation signal

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03B 5/30-5/36

Claims (4)

(57) [Claims] An oscillation circuit having a piezoelectric vibrator in an oscillation loop; a pulse generation circuit for detecting a start of power supply to the oscillation circuit and injecting a pulse into the oscillation loop after a lapse of a predetermined time from the start of power supply ; Write data to control the timing of the pulse generation.
And a readable data storage circuit, wherein the pulse generation circuit reads data from the data storage circuit.
The piezoelectric oscillator generates the pulse based on the obtained data . 2. An oscillation circuit having a piezoelectric vibrator in an oscillation loop, a pulse generation circuit detecting a start of power supply to the oscillation circuit, and injecting a pulse into the oscillation loop after a lapse of a predetermined time from the start of power supply, Has a predetermined capacitance and is connected to the piezoelectric vibrator
Fixed connection capacitance element and a plurality of selection connection capacitance elements having a predetermined capacitance.
And a specific one of the plurality of selective connection capacitive elements.
A capacitor connected in parallel with the fixed connection capacitance element.
Quantity connection circuit and the fixed connection capacitance element of the selected connection capacitance element.
Frequency control data for controlling connection / disconnection, and
And pulse control data for controlling the generation timing of the pulse.
A data storage circuit for storing data, and the data based on externally-adjusted frequency control data.
When the frequency control data is stored in advance in the data storage circuit,
In both cases, the frequency control data for adjustment or the frequency
Controlling the capacitance connection circuit based on the number control data;
On the basis of externally-adjusted pulse control data,
The pulse control data is stored in a data storage circuit in advance.
And the adjustment pulse control data or the
Controlling the pulse generation circuit based on pulse control data
A piezoelectric oscillator , comprising: 3. An oscillator adjustment system for adjusting a timing of generating the pulse in the piezoelectric oscillator according to claim 2 , wherein a power supply unit that supplies power to the oscillation circuit, and an oscillation state detection that detects an oscillation state of the oscillation circuit. Means, measuring means for measuring an oscillation start time from when power supply by the power supply means is started to when an oscillation state is detected by the oscillation state detecting means, and oscillation start time measured by the measuring means is reduced. The adjustment pulse control data is output as described above, and when the oscillation start time is the shortest, the adjustment pulse control data is used as the pulse control data in the data storage circuit.
An oscillator data adjusting means for controlling the connection control circuit so as to store the data in a path . 4. The oscillator adjusting method for adjusting the generation timing of the pulse in the piezoelectric oscillator according to claim 2 , wherein power is supplied to the oscillation circuit, and an oscillation state of the oscillation circuit is detected. Measuring the oscillation start time from the start of the oscillation until the oscillation state is detected, and outputting the adjustment pulse control data so that the oscillation start time is short, and the oscillation start time is the shortest. Controlling the connection control circuit so that the adjustment pulse control data is sometimes stored in the data storage circuit as the pulse control data.