JP2001345644A - Oscillation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure stabilized oscillation while reducing power consumption, the size and the weight. SOLUTION: When a control signal S11 from a switch control circuit 11 is 'L', a PMOS 14a and an NMOS 14b are turned on and power is supplied to a PMOS 13a and an NMOS 13b for exciting a quartz oscillator 15. Consequently, an input voltage Vin on an input node Nin is inverted by the PMOS 13a and NMOS 13b and Vout is outputted from an output node Nout. The Vout is subjected to phase inversion by the quartz oscillator 15, a resistor 16 and capacitors 17, 18 before being fed back to the input voltage Vin. When the signal S11 is 'H', the PMOS 14a the NMOS 14b are turned off and power supply to the PMOS 13a and NMOS 13b is interrupted. The quartz oscillator 15 oscillates freely and the oscillation circuit keeps oscillation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillation circuit provided in a portable electronic device or the like and using a piezoelectric vibrator such as a crystal vibrator.

[0002]

2. Description of the Related Art Conventionally, various proposals have been made in the following documents for reducing the power consumption and prolonging the life of a battery in an oscillation circuit provided in, for example, a portable electronic device. I have. Reference: JP-A-10-325886

FIG. 2 is a circuit diagram of a conventional oscillation circuit described in the above document. This oscillation circuit is a circuit using a crystal oscillator and a complementary MOS transistor (hereinafter referred to as “CMOS”) inverter, and has an output voltage Vou.
It has a switch control circuit 1 that generates a control signal S1 synchronized with t. The output terminal of the switch control circuit 1
An inverter 2 for inverting the control signal S1 is connected, and a gate of a P-channel MOS transistor (hereinafter referred to as “PMOS”) 3a that is turned on / off by the control signal S1 is connected. The source of the PMOS 3a is connected to the ground potential VSS, and the drain is connected to the node N1. An output terminal of the inverter 2 has an N-channel MOS transistor (hereinafter referred to as “NMO”).
S ". 3) The gate of 3b is connected. NMO
The drain of S3b is connected to the node N2, and the source is connected to the negative power supply potential Vreg.

A CMOS inverter 4 is connected between nodes N1 and N2. Inverter 4 is a PMOS
4a and the NMOS 4b, the source of the PMOS 4a is connected to the node N1, and the drain of the PMOS 4a and the drain of the NMOS 4b are connected to the output node Nout. The source of the NMOS 4b is connected to the node N2, and the gate of the PMOS 4a and the gate of the NMOS 4b are connected to the input node Nin. A feedback circuit is connected between the input node Nin and the output node Nout. The feedback circuit consists of a crystal unit 5, a resistor 6,
And a capacitor 7, 8, and a circuit that inverts the phase of the output voltage Vout of the inverter 4 and feeds it back to the input node Nin. The inverter 4 is connected to the input node Nin
It has a function of driving the crystal resonator 5 by performing on / off operations by the above input voltage Vin.

FIG. 3 is a voltage waveform diagram showing the operation of the oscillation circuit of FIG. In FIG. 3, in the cycle T of the control signal S1, the period Ta is at the “L” level, and the period Tb is at the “H” level. In the input voltage Vin and the output voltage Vout, Vtp is the threshold voltage of the PMOS 4a, and Vtn is NMO.
The threshold voltage FT of S4b and the FT are in a floating state.
In the voltage waveform of the PMOS 4a, the “H” level is PM
During the ON period of the OS 4a, Cp is the capacitance of the PMOS 4a, Cp
gd is the gate-drain capacitance of the PMOS 4a.
In the voltage waveform of the NMOS 4b, the “H” level is NM
During the ON period of the OS 4b, Cn is the capacitance of the NMOS 4b, Cn
gd is the gate-drain capacitance of the NMOS 4b.
NS is noise. The waveform of the capacitance viewed from the output node Nout is a waveform obtained by superposing the voltage waveforms of the PMOS 4a and the NMOS 4b. Cd is the output node Nout
From the viewpoint of the drain capacitance of the PMOS 4a and the NMOS 4b.

Hereinafter, the operation of the oscillation circuit shown in FIG. 2 will be described with reference to FIG. The control signal S1 is output from the switch control circuit 1 in synchronization with the output voltage Vout output from the output node Nout. In the control signal S1, the period Ta of the cycle T is at the “L” level, and the period Tb is at the “H” level. When the control signal S1 is in the “L” level period Ta, the PMOS 3a is turned on, the control signal S1 is inverted by the inverter 2, and the NMOS 3b is turned on by the “H” level signal. PMOS3
a and the NMOS 3b are turned on, the inverter 4
Is supplied with power. When the control signal S1 becomes “H” level in the period Tb, the PMOS 3a and the NMOS 3b
Is turned off, and the power supply to the inverter 4 is stopped.

When power is supplied to the inverter 4 during the period Ta of the control signal S1, when the input voltage Vin of the input node Nin becomes higher than the threshold voltage Vtn of the NMOS 4b, the NMOS 4b is turned on, and the NMOS 3b,
4b, the output node Nout becomes negative power supply potential Vre
g. When the input voltage Vin of the input node Nin becomes lower than the threshold voltage Vtp of the PMOS 4a, the PMOS 4a is turned on, and the PMOS 3
a, 4a output node Nout is connected to ground potential VSS.
It is raised to. The crystal oscillator 5 is driven to be excited by the output voltage Vout of the output node Nout. The output voltage Vout is inverted in phase by the feedback circuit including the crystal oscillator 5, the resistor 6, and the capacitors 7, 8, and is fed back to the input node Nin.

When the power supply to the inverter 4 is stopped during the period Tb of the control signal S1, the oscillation circuit continues to oscillate due to the inertia (free vibration) of the crystal oscillator 5. Therefore, the input voltage Vin having the waveform as shown in FIG. 3 and the output voltage Vout having the inverted waveform appear at the input node Nin and the output node Nout. Input voltage Vin is NMOS
When the voltage exceeds the threshold voltage Vtn of 4b, the NMOS 4b is turned on, and the crystal resonator 5 is driven to be excited. When the input voltage Vin falls below the threshold voltage Vtp of the PMOS 4a, the PMOS 4a is turned on, and the crystal oscillator 5
Is driven for excitation. Thus, the control signal S1 is output from the switch control circuit 1 in synchronization with the output voltage Vout,
The control signal S1 causes the PMOS 3a and the NMOS 3
By turning on / off b, and intermittently supplying power to the inverter 4, power consumption during oscillation can be reduced.

[0009]

However, the conventional oscillator circuit shown in FIG. 2 requires a PMO to reduce power consumption.
Since the S3a and the NMOS 3b are turned on / off, when the PMOS 3a and the NMOS 3b are off, the PMOS 4a and the NMOS 4b are disconnected from the ground potential VSS and the negative power supply potential Vreg.
When the source-side nodes N1 and N2 of the NMOS 4b are in a floating state, for example, as shown in FIG.
Since the load capacitance as viewed from the output node Nout side of the crystal unit 5 changes when the NMOS transistor a and the NMOS 3b are turned off, there is a problem that the oscillation frequency, phase or amplitude of the crystal unit 5 changes. An object of the present invention is to solve the problems of the prior art and to provide a small-sized oscillation circuit which consumes less power, has a stable oscillation operation, and has a small size.

[0010]

Means for Solving the Problems To solve the above problems, a first aspect of the present invention is an oscillation circuit, comprising:
A feedback circuit that has a piezoelectric vibrator connected between an input node and an output node that outputs an output signal, and that inverts a phase of an output signal output from the output node and feeds back the input signal to the input node; A first switching element that is connected between a power supply potential of the first node and a first node, and that is turned on / off by a signal on the input node to excite and drive the piezoelectric vibrator; Different second power supply potential and second
A second switching element which is connected between the first switching element and a second switching element which is turned on / off at a timing different from that of the first switching element by a signal on the input node to excite the piezoelectric vibrator.
And a first switch connected between the first node and the output node, and turned on / off by a first control signal to control power supply to the first switching element Means, connected between the output node and the second node, and turned on / off by a second control signal at a timing different from that of the first control signal to perform an on / off operation to the second switching element. Second switch means for controlling power supply.

Thus, the first control signal causes the first
Switch means performs an on / off operation to intermittently supply power to the first switching element. Further, the second control signal having a timing different from that of the first control signal allows the second control signal to be generated.
Switch means performs on / off operation, and supplies power intermittently to the second switching element. The first switching element is turned on / off by a signal on the input node to drive and drive the piezoelectric vibrator in the feedback circuit. Further, the second switching element is turned on / off at a timing different from that of the first switching element by a signal on the input node, and the piezoelectric vibrator is driven to be excited. The output signal output from the output node is inverted in phase by the feedback circuit including the piezoelectric vibrator and is fed back to the input node. As a result,
Even if the power supply to the first and second switching elements is intermittently performed, the oscillation circuit continues stable oscillation.

According to a second aspect of the present invention, there is provided an oscillation circuit having a piezoelectric vibrator connected between an input node and an output node for outputting an output signal, and inverting a phase of an output signal output from the output node. A feedback circuit that feeds back to the input node, and is connected between a first power supply potential and the input node, and is turned on / off by a control signal to supply a constant power supply current to the input node when in an on state. And a current supply circuit for stopping supply of the power supply current when the power supply circuit is in an off state, and connected between the input node and the drive node, and turned on / off at the same timing as the current supply circuit by the control signal.
Switch means for supplying the power supply current to the drive node when in an off state and in an on state, and stopping supply of the power supply current in an off state; a second power supply potential different from the first power supply potential And a switching element connected between the driving node and the driving node, the switching element being turned on / off by the output signal to excite and drive the piezoelectric vibrator.

Thus, the current supply circuit is turned on / off by the control signal, and the power supply current is intermittently supplied to the input node. The power supply current supplied to the input node is intermittently supplied to the drive node by switch means that performs on / off operation at the same timing as the current supply circuit by a control signal. The switching element connected to the drive node
An on / off operation is performed by an output signal to excite and drive the piezoelectric vibrator in the feedback circuit. As a result, the output signal output from the output node is inverted in phase by the feedback circuit and fed back to the input node, so that the oscillation circuit continues stable oscillation.

According to a third aspect of the present invention, there is provided an oscillation circuit having a piezoelectric vibrator connected between an input node and an output node for outputting an output signal, and inverting a phase of an output signal output from the output node. And a feedback circuit connected between the first node and the second node, the signal on the first node being inverted and amplified when a power supply potential is applied. 2 is connected between the input node and the first node, and is turned on / off by a first control signal. First switch means for connecting the input node to the first node when in an on state, and disconnecting the input node and the first node when in an off state; Connected to the output node, the first control A propagation delay time from when the first switch means is turned on to when the signal on the input node propagates to the second node after the second control signal is turned on / off by the second control signal synchronized with the signal After the lapse of the time, the second node is connected to the output node by turning on,
A second switch which is turned off before the first switch is turned off to cut off the second node and the output node;
And switch means.

Thus, the first control signal causes the first
Are turned on / off, and the second switch is turned on / off by a second control signal synchronized with the first control signal. At this time, after the input node and the first node are connected by the first switch,
The second switch connects the second node to the output node, and the signal inverting amplifier is activated. Further, after the second node cuts off the second node and the output node, the first switch node cuts off the input node and the first node, and the signal inverting amplifier circuit becomes inactive. As described above, even if the signal inverting amplifier circuit is intermittently operated, the oscillation circuit continues stable oscillation.

According to a fourth aspect of the present invention, there is provided an oscillation circuit having a piezoelectric vibrator connected between an input node and an output node for outputting an output signal, and inverting a phase of an output signal output from the output node. A feedback circuit that returns to the input node, and is connected between the first power supply potential and the first node;
A current supply circuit for supplying a constant power supply current to the first node; a current supply circuit connected between a second power supply potential different from the first power supply potential and the first node; A switching element that is turned on / off by a signal to excite the piezoelectric vibrator and is connected between the input node and the second node, and is turned on / off by a first control signal;
The input node and the second
A first switch means for connecting the input node and the second node when in an off state, and a first switch means connected between the first node and the output node; The second switch is turned on / off by a second control signal synchronized with the first control signal, and from when the first switch is turned on until the signal on the input node propagates to the first node. After the propagation delay time elapses, it is turned on to connect the first node and the output node,
And a second switch for turning off the first node and turning off the output node before the first switch turns off.

Thus, after the input node and the second node are connected by the first switch, the first node and the output node are connected by the second switch, and the power supplied from the current supply circuit is supplied. The switching element is activated by the current. Further, after the first node and the output node are cut off by the second switch, the input node and the second node are cut off by the first switch, and the switching element becomes inactive. As described above, even when the switching element is operated intermittently, the oscillation circuit continues stable oscillation.

According to a fifth aspect, in the oscillation circuit, the piezoelectric vibrator and the first capacitor connected between the input node and the second power supply potential of the first and second power supply potentials different in potential. And second and third capacitors connected between the input node and the second power supply potential for dividing a signal between both ends of the piezoelectric vibrator and the first capacitor; and an output node and a first capacitor. Connected to a second node
A feedback amplifier that amplifies a signal on the second node with an amplification factor corresponding to a potential difference between the node and the first node and outputs an output signal from the output node; Connected between the input node and the second node in an on state, and connected to the input node and the second node in an off state. A first switch for disconnecting from a second node; a connection point between the second and third capacitors;
And a signal on the input node which is turned on / off by a second control signal synchronized with the first control signal to turn on the first switch means. Is turned on after a delay time until the output signal is output from the output node after being amplified by the feedback amplifier, and connects the connection point to the first node; And a second switch for turning off the switch before the switch is turned off to cut off the connection point and the first node.

Thus, after the input node and the second node are connected by the first switch, the connection point of the first and second capacitors and the first node are connected by the second switch. , The feedback amplifier is activated. Further, after the connection point and the first node are cut off by the second switch means, the input node and the second node are cut off by the first switch means, and the feedback amplifier becomes inactive. Thus, even if the feedback amplifier is operated intermittently, the oscillation circuit keeps oscillating stably due to the free vibration of the piezoelectric vibrator.

A sixth invention is connected to the output node according to any one of the first to fifth inventions, and divides an output signal output from the output node by a predetermined dividing ratio. A frequency dividing circuit is provided. Accordingly, for example, when a high-frequency vibrator having a small external shape is used as the piezoelectric vibrator, if a high-frequency output signal output from the piezoelectric vibrator is divided into a low-frequency signal by a frequency dividing circuit, the piezoelectric vibrator can be obtained. The oscillation circuit including the above can be downsized.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a circuit diagram of an oscillation circuit using a CMOS inverter according to a first embodiment of the present invention. This oscillation circuit outputs an output signal (eg, an output voltage) from an output node Nout.
It has a switch control circuit 11 that generates a first control signal S11 synchronized with Vout. Switch control circuit 1
The first output terminal is connected to an inverter 12 that inverts the first control signal S11 and outputs a second control signal S12. First power supply potential (eg, positive power supply potential) V
DD has a first switching element (for example, PMOS)
The source of 13a is connected, the drain is connected to the first node N11, and the gate is connected to the input node Nin. Input node Ni for inputting input voltage Vin
n is a second switching element (for example, NMOS)
The gate of 13b is connected, the drain is connected to the second node N12, and the source is connected to a second power supply potential (for example, ground potential) VSS. This PMOS
A signal inverting amplifier circuit (for example, a CMOS inverter) is composed of the NMOS 13b and the NMOS 13b.

The source of a first switch means (for example, a PMOS) 14a is connected to the node N11, the drain is connected to the output node Nout, and the gate is connected to the output terminal of the switch control circuit 11. The output node Nout is connected to a second switch means (for example, NMO).
S) The drain of 14b is connected, the source is connected to the node N12, and the gate is connected to the output terminal of the inverter 12. Input node Nin and output node No
Between ut, a feedback circuit is connected. The feedback circuit includes a piezoelectric vibrator (for example, a crystal vibrator) 15 and a resistor 1
6 and capacitors 17 and 18, and is a circuit that inverts the phase of the output voltage Vout and feeds it back to the input node Nin.

A frequency dividing circuit 19 is connected to the output node Nout as required. The frequency dividing circuit 19 is, for example, a high-frequency vibrator (for example, 20 MHz) having a small external shape as the crystal vibrator 15 for reducing the size and weight of the oscillation circuit.
In the case of using a low frequency output voltage (for example, 10 to 20 MHz), the frequency is divided at a desired frequency division ratio.
Used to get the band). When a low-frequency quartz oscillator 15 is used, the frequency dividing circuit 19 is unnecessary.

Next, the operation of the oscillation circuit shown in FIG. 1 will be described.
The control signal S11 is output from the switch control circuit 11 in synchronization with the output voltage Vout output from the output node Nout. The control signal S11 is “L” level in the period Ta in the cycle T,
It goes to the “H” level at b. In the “L” level period Ta of the control signal S11, the PMOS 14a is turned on, and the control signal S11 is inverted by the inverter 12, and
This inverted signal turns on the NMOS 14b. When the PMOS 14a and the NMOS 14b are turned on, the PMOS 13a and the N
Power is supplied to the MOS 13b.

When the input voltage Vin on the input node Nin is at "L" level, the PMOS 13a is turned on,
The NMOS 13b is turned off. When the PMOS 13a is turned on, the output node Nout is pulled up to the power supply potential VDD through the PMOSs 13a and 14a, and the crystal oscillator 15 is driven to be excited. When the input voltage Vin on the input node Nin is at "H" level, the PMOS 13a is turned off and the NMOS 13b is turned on. The output node Nout is pulled down to the ground potential VSS through the NMOSs 13b and 14b, and the crystal oscillator 15 is driven for excitation. As a result, the output voltage Vout output from the output node Nout is inverted in phase by the feedback circuit including the crystal oscillator 15, the resistor 16, and the capacitors 17, 18, and is fed back to the input node Nin.

Next, during the "H" level period Tb of the control signal S11, the PMOS 14a is turned off,
The control signal S11 is inverted by the inverter 12, and the NMOS 14b is turned off by the inverted signal. PM
When the OS 14a and the NMOS 14b are turned off, the PMOS 13a and the NMOS 1 that drive the crystal unit 15
The power supply to 3b is stopped.

Even when the power supply is stopped, the crystal oscillator 15 oscillates due to free oscillation.
A voltage waveform as shown in FIG. 3 appears at the in and output nodes Nout. When the input voltage Vin on the input node Nin becomes higher than the threshold voltage Vtn of the NMOS 13b, this N
MOS 13b is turned on, and node N12 is pulled down to ground potential VSS. When the input voltage Vin on the input node Nin becomes lower than the threshold voltage Vtp of the PMOS 13a, the PMOS 13a is turned on, and the node N11 is raised to the power supply potential VDD. As described above, even when the PMOS 14a and the NMOS 14b are turned off and the power supply to the PMOS 13a and the NMOS 13b is stopped, the oscillation circuit continues to oscillate due to the free oscillation of the crystal oscillator 15. When the frequency dividing circuit 19 is connected to the output node Nout, the output node Nout
Is divided by the frequency dividing circuit 19 to output a low-frequency oscillation output voltage.

In the first embodiment, the following (a) to (a)
There is an effect as shown in FIG. (A) When the power supply is stopped, the PMOS 14a and the NMOS 14b are turned off, and are not affected by external noise. Therefore, the output node N of the crystal unit 15
The load capacity seen from the out side does not change. As a result, the oscillation frequency, phase and amplitude do not change. Therefore, a stable oscillation operation is performed with a small power consumption.

(B) For example, a high-frequency vibrator having a small external shape is used as the crystal vibrator 15 and the output node Nou
When the frequency dividing circuit 19 is connected to t, the output node Nou
The high-frequency output voltage Vout output from t can be divided by the frequency dividing circuit 19 to output a desired low-frequency output voltage. Thus, the size and weight of the oscillation circuit can be reduced.

(C) The control signal S11 is the output voltage Vou
Although output from the switch control circuit 11 is synchronized with t, even if the control signal S11 is asynchronous with the output voltage Vout, substantially the same effects as in the above (a) and (b) can be obtained. Further, the switch control circuit 11 is omitted, and the control signal S1 generated from a clock signal or the like externally is provided.
If 1 (this is a signal synchronized with the output voltage Vout or an asynchronous signal), the circuit configuration can be simplified.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention.
FIG. 2 is a circuit diagram of an oscillation circuit using an NMOS inverter according to the first embodiment, in which components common to those in FIG. 1 according to the first embodiment are denoted by common reference numerals. In this oscillating circuit, instead of the PMOS 14a and the NMOS 14b in FIG.
S) 25 are provided, and the PMOS 13a and the NMOS 1 of FIG.
Instead of 3b, a switching element (for example, NMOS) 26 for driving the crystal resonator 15 is provided, and a current supply circuit is connected between the power supply potential VDD and the input node Nin.

The current supply circuit controls the control signal S output from the switch control circuit 11A in synchronization with the output voltage Vout.
11A is a circuit that performs on / off operation by 11a, supplies a constant power supply current to the input node Nin when in the on state, and stops supplying the power supply current when in the off state.
S21, S23, S24 and the constant current source 22. The source of the PMOS 21 is connected to the power supply potential VDD, and its drain and gate are connected to the ground potential VSS via the constant current source 22. The gate of the PMOS 21 is connected to the gate of the load PMOS 23,
The source of the MOS 23 is connected to the power supply potential VDD, and the drain is connected to the input node Nin. PMOS2
1 and 23 and the power supply potential VDD
The source and the drain of the OS 24 are connected, and this PMO
The gate of S24 is connected to the output terminal of the switch control circuit 11A.

Between the input node Nin and the output node Nout, a crystal oscillator 15, a resistor 16 and a capacitor 1
A feedback circuit composed of 7 and 18 is connected. Between the input node Nin and the drive node N21, a source and a drain of a switch means (for example, NMOS) 25 for controlling power supply are connected, and the gate is connected to an output terminal of the switch control circuit 11A. Drive node N21
A source and a drain of a switching element (for example, NMOS) 26 for driving the crystal resonator 15 for excitation are connected between the ground potential VSS and the ground potential VSS, and the gate is connected to the output node Nout. Further, the output node Nou
A driving inverter 27 is connected to t.

Next, the operation of the oscillation circuit shown in FIG. 4 will be described.
The control signal S11 is output from the switch control circuit 11A in synchronization with the output voltage Vout output from the output node Nout.
a is output. When the control signal S11a is at "H" level, the PMOS 24 is turned off and the PMOS 24 is turned off.
The gates of 21 and 23 are pulled down to "L" level,
The PMOSs 21 and 23 are turned on. PMOS2
Since 1 and 23 constitute a current mirror circuit,
When a constant power supply current flows through the source and the drain of the PMOS 21 by the constant current source 22, a corresponding power supply current flows through the source and the drain of the PMOS 23. Since the control signal S11a is at the “H” level, the NMOS 25 is in the ON state, the power supply current supplied to the input node Nin is supplied to the NMOS 26, and the power supply state is set.

Output voltage Vout on output node Nout
Is at “H” level, the NMOS 26 is in an on state,
When the signal is at “L” level, the NMOS transistor is turned off, and this NMOS
26 drives the crystal resonator 15 to be excited. The output voltage Vout on the output node Nout is
The phase is inverted by a feedback circuit consisting of 5, a resistor 16, and capacitors 17 and 18, and is fed back to the input node Nin.

When the control signal S11a output from the switch control circuit 11A goes low, the PMO
S24 is turned on, and the gates of the PMOSs 21 and 23 are pulled up to the “H” level.
1 and 23 are turned off. Further, the control signal S11a
The "L" level also causes the NMOS 25 to be turned off, and the power supply to the NMOS 26 is stopped. Even when the power supply is stopped, the crystal oscillator 15 freely vibrates, so that the oscillation circuit continues stable oscillation. This causes the output node Nout to output the oscillation output voltage Vout, which is driven by the inverter 27 and output. The second embodiment has substantially the same effects as the effects (a) and (b) of the first embodiment. Further, the control signal S11a may be asynchronous with the output voltage Vout, or may be configured to be externally supplied by omitting the switch control circuit 11A.
The same effect as the effect (c) of the embodiment can be obtained.

(Third Embodiment) FIG. 5 shows a third embodiment of the present invention.
FIG. 2 is a circuit diagram of an oscillation circuit using a CMOS inverter according to the first embodiment, in which components common to those in FIG. 1 according to the first embodiment are denoted by common reference numerals. In the oscillation circuit of FIG. 1 showing the first embodiment, a C composed of a PMOS 13a and an NMOS 13b for exciting and driving the quartz oscillator 15 is used.
PMOS 14a and NMOS for MOS inverter
The power consumption is reduced by intermittently supplying power to the CMOS inverter by turning on / off the 14b. On the other hand, in the third embodiment, the PMOS 13a and the NMO
The power supply to the CMOS inverter 13 in S13b is not controlled, and the input / output side of the CMOS inverter is turned on / off to intermittently operate the CMOS inverter 13 to reduce the power consumption.

In this oscillation circuit, the quartz oscillator 15 and the resistor 16 are connected between the input node Nin and the output node Nout.
And a feedback circuit composed of capacitors 17 and 18. Between the input node Nin and the first node N31, a first switch means 31 such as a field effect transistor (hereinafter referred to as "FET") is connected.
The switch means 31 is a circuit for switching and connecting between the contacts 31a and 31c and between the contacts 31b and 31c based on a first control signal S21 synchronized or asynchronous with the output voltage Vout output from the output node Nout. The contact 31b has a fixed potential (for example, a positive power supply potential V
DD or the ground potential VSS).

A first node N31 and a second node N32
And a signal inverting amplifier circuit (for example, a PMOS 13
CMOS inverter 1 comprising a and NMOS 13b
3) is connected, and the source of the PMOS 13a is connected to a first power supply potential (for example, a positive power supply potential) VDD,
The source of the NMOS 13b is connected to a second power supply potential (for example, ground potential) VSS. Second node N32
A second switch means 32 such as an FET is connected between the output node Nout and the output node Nout. Switch means 32
Are synchronized with or asynchronous with the output voltage Vout.
Circuit that is turned on / off by the control signal S22.

A third switch means 33 such as an FET and a capacitor 34 are connected in series between the input node Nin and the ground potential VSS. The switch means 33 is
This circuit is turned on / off by a third control signal S23 synchronized or asynchronous with the output voltage Vout. Further, an inverter 35 for driving the output voltage Vout is connected to the output node Nout.

FIG. 6 is a voltage waveform diagram showing the operation of the oscillation circuit of FIG. Hereinafter, the operation of FIG. 5 will be described with reference to FIG. When the inverter 13 is operated,
At time t1, the control signal S21 turns off the contacts 31b and 31c of the switch means 31 and disconnects them from the fixed potential (for example, the power supply potential VDD). Next, at a time t2, the switch means 3
While turning on between the 1 contact points 31a and 31c,
The switch means 33 is also turned on by the control signal S23. After the point between the contacts 31a and 31c of the switch means 31 is turned on, the input voltage Vi on the input node Nin
At time t3 after a lapse of a propagation delay time Δt until n propagates to the second node N32, the control means S22 turns on the switch means 32. Thus, the inverter 13 is electrically connected between the input node Nin and the output node Nout, and the input node Nin
Is connected to the capacitor.

When the input voltage Vin on the input node Nin is at "H" level, the NMOS 13b is turned on, and the output node Nout is lowered to the ground potential VSS. When the input voltage Vin is at the “L” level, the PMOS 13a is turned on, and the output node No.
ut is raised to the power supply potential VDD. This allows
The quartz oscillator 15 is driven to be excited, and this quartz oscillator 15
The output voltage Vout on the output node Nout is inverted in phase by the feedback circuit including the resistor 16 and the capacitors 17 and 18, and is fed back to the input node Nin.

When the inverter 13 is set to the non-operation state,
At time t4, the switch means 32 is turned off by the control signal S22, and at time t5, the contacts 31a and 31c of the switch means 31 are controlled by the control signal S21.
The switch 33 is turned off by the control signal S23 while the interval is turned off. Thereafter, at time t6, the control signal S21 causes the contact 3
1b and 31c are turned on, and the node N31 is fixed at the power supply potential VDD. As a result, the inverter 13 stops operating, but the oscillation circuit continues to oscillate due to the free oscillation of the crystal oscillator 15. The output voltage Vout output from the output node Nout is driven by the buffer 35 and output.

In the third embodiment, the following (i):
It has the effect (ii). (I) The switch means 31, 32 on the input side and the output side of the inverter 13 are turned on / off, and
3, the power consumption can be reduced. In particular, when the inverter 13 is operated, the input-side switch means 31 is turned on and then the output-side switch means 32 is turned on. When the inverter 13 is deactivated, the output-side switch means 32 is turned on. Is turned off, the input-side switch means 31 is turned off. Also, the switch means 31
And the switch means 33 are simultaneously turned on / off. Thus, when the operation state and the non-operation state of the inverter 13 are switched, the fluctuation of the load capacitance viewed from the output node Nout side of the crystal resonator 15 is suppressed, and the free vibration of the crystal resonator 15 is not suppressed. The stable oscillation operation is performed without stopping the oscillation of the crystal unit 15 or changing the oscillation frequency, phase and amplitude. (Ii) In substantially the same manner as the effect (b) of the first embodiment, for example, a high-frequency vibrator having a small external shape is used as the crystal vibrator 15, and the high-frequency output voltage Vout is divided by the frequency dividing circuit 19 to reduce the frequency. If the frequency output voltage is used, the size and weight of the oscillation circuit can be reduced.

(Fourth Embodiment) FIG. 7 shows a fourth embodiment of the present invention.
FIG. 13 is a circuit diagram of an oscillation circuit using an NMOS inverter according to the third embodiment, and components common to those in FIG. 5 according to the third embodiment are denoted by the same reference numerals. In this oscillation circuit, a switching element (for example, NMOS) 44 is provided instead of the CMOS inverter 13 in FIG. 5, and a current supply circuit for supplying a power supply current to the NMOS 44 is provided.

That is, this oscillation circuit is connected to the input node Nin
A feedback circuit including a crystal oscillator 15, a resistor 16, and capacitors 17 and 18 is connected between the output node Nout and the output node Nout. The capacitor 34 is connected to the input node Nin via the third switch means 33 to the ground potential VSS. Further, the first switch means 31 is connected between the input node Nin and the second node N42. The switch means 31 is a circuit for switching between the contacts 31a and 31c and between the contacts 31b and 31c. The contact 31a is connected to the input node Nin, and the contact 31b is connected to a fixed potential (for example, ground potential VSS). The contact 31c is connected to the second node N42.

First power supply potential (eg, positive power supply potential)
A current supply circuit is connected between VDD and the first node N41. The current supply circuit includes a first node N4
1 is a circuit for supplying a constant power supply current to
1 and 43 and a constant current source 42. PMO
The sources of S41 and S43 are connected to the power supply potential VDD. The gates of the PMOSs 41 and 43 are commonly connected, and further connected to the drain of the PMOS 41. The drain of the PMOS 41 is connected to the ground potential VSS via the constant current source 42. First node N41
The source and the drain of a switching element (for example, NMOS) 44 are connected between the second power supply potential (for example, ground potential VSS) and the second power supply potential (for example, ground potential VSS), and the gate thereof is connected to the second node N42.

In the oscillation circuit shown in FIG.
3 forms a current mirror circuit, and a constant current source 4
When a constant power supply current flows through the source and the drain of the PMOS 41 due to 2, the power supply current corresponding to the power supply current flows through the source and the drain of the PMOS 43 and is supplied to the first node N41. This causes the NMOS 44 to be in an operating state, and the switching operation of the NMOS 44 drives and drives the crystal resonator 15.

This oscillation circuit operates almost in the same manner as the oscillation circuit of the third embodiment shown in FIG. That is, the switch means 31, 33 on the input node Nin side and the output node No.
ut side switching means 32 is turned on / off and N
The power consumption is reduced by intermittently operating the MOS 44. In particular, when the NMOS 44 is set to the operating state, the switch means 31 and 33 on the input node Nin side are used.
Is turned on, the switch means 32 on the output node Nout side is turned on, and when the NMOS 44 is turned off, the switch means 32 on the output node Nout side is turned off, and then the input node Nin side is turned off. The switch means 31 and 33 are turned off. As a result, the third
Almost the same effect as the effect (i) of the embodiment can be obtained.
Further, for example, by using a high-frequency vibrator having a small external shape as the crystal vibrator 15 and connecting a frequency dividing circuit to the output node Nout, an effect similar to the effect (ii) of the third embodiment can be obtained.

(Fifth Embodiment) FIGS. 8A and 8B are circuit diagrams of a Colpitts oscillation circuit showing a fifth embodiment of the present invention, and FIG. 8A is an overall circuit diagram. And (b) is an equivalent circuit diagram immediately after the power is turned on and before the transistor (hereinafter, referred to as “Tr”) operates. This oscillating circuit is a circuit based on the same principle as the oscillating circuit of FIG. 5 showing the third embodiment, and includes a piezoelectric vibrator between an input node Nin and a second power supply potential (for example, ground potential) VSS. (For example, a quartz oscillator) 51 and a variable first capacitor 52 are connected in series. The connection node N5 is connected to the input node Nin via a second capacitor 53 for voltage division.
1 is connected, and this connection point N51 is connected to the ground potential VSS via the third capacitor 54 for voltage division.

The oscillation circuit includes a feedback amplifier (for example, NP
An N-type Tr) 55 is provided, and a first node N52 on the emitter side of the Tr 55 is connected to the ground potential V
Connected to SS. The output node Nout on the collector side of the Tr 55 is connected to a first power supply potential (for example, a positive power supply potential) VDD via a resistor 57, and is also connected to a DC blocking capacitor 58. First switch means 59 such as a Tr is connected between the base of the Tr 55 and the input node Nin. Switch means 59
Is a contact 59a connected to the input node Nin, a contact 59 connected to a fixed potential (for example, the ground potential VSS).
b, and a contact 59c connected to the second node N53 on the base side of the Tr55, and a contact between the contacts 59a and 59c by a control signal synchronized or asynchronous with the output voltage Vout output from the output node Nout. 59b
And 59c. A second switch, such as a Tr, which is turned on / off by a control signal synchronized or asynchronous with the output voltage Vout is provided between a connection point N51 between the voltage dividing capacitors 53 and 54 and the first node N52. Means 60 is connected.

A switch means 61 such as a Tr and a resistor 62 are connected in series between the input node Nin and the ground potential VSS. Between the input node Nin and a fixed potential (for example, the positive power supply potential VDD or the ground potential VSS), a series circuit of a switch means 63 such as a Tr and a resistor 64, a third switch means 65 such as a Tr and a capacitor 6
6 series circuits. Switch means 61,
63 and 65 are circuits that perform on / off operations in response to control signals that are synchronized or asynchronous with the output voltage Vout.

FIG. 9 is a voltage waveform diagram showing the operation of the oscillation circuit of FIG. Hereinafter, the operation of FIG. 8 will be described with reference to FIG. Contacts 59b and 59 of switch means 59
c, the node N53 is set to the ground potential VSS, and at time t1, the contacts 59b and 59c
And the switch means 61 and 63
To the off state. Next, at time t2, the portion between the contacts 59a and 59c of the switch device 59 is turned on, and the switch device 65 is turned on. After a lapse of a delay time Δt from when the contact point 59a and the contact point 59c of the switch means 59 are turned on to when the input voltage Vin on the input node Nin is amplified by the Tr 55 and the output voltage Vout is output from the output node Nout. At time t3, the switch means 60 is turned on. Then, the voltage between both ends of the crystal unit 51 and the capacitor 52 is divided by the capacitors 53 and 54.

The voltage across the capacitor 53 is applied between the base and the emitter of the Tr 55, and a current flows between the base and the emitter. Thereby, the input node Nin
The upper input voltage Vin is amplified by Tr55. The output voltage Vout on the output node Nout causes the crystal unit 5
1 is driven to excite, and the oscillation circuit oscillates. At time t4, the switch means 60 is turned off, and then at time t4.
5, the contacts 59a and 59c of the switch means 59
At the same time, the switch unit 65 is turned off. Thereafter, at time t6, the switch unit 5
9 between the contacts 59b and 59c, the node N53 is fixed to the ground potential VSS, and the switch means 61 and 63 are turned on, and the resistors 62 and 64 are turned on.
Are connected to the input node Nin. Thereby, Tr5
5 stops the amplification operation, but the oscillation circuit continues to oscillate due to the free oscillation of the crystal oscillator 51. Therefore, substantially the same effects as the effects (i) and (ii) of the third embodiment can be obtained.

(Sixth Embodiment) FIG. 10 is a circuit diagram of a Colpitts-type oscillation circuit using an FET according to a sixth embodiment of the present invention. Common elements are denoted by common reference numerals. In this oscillation circuit, a feedback amplifier 70 composed of an FET is provided instead of the Tr 55 in FIG. Feedback amplifier 70
Has NMOSs 71 and 72 and a resistor 73.
The drain of OS 71 is connected to power supply potential VDD, the gate is connected to switch means 59 via node N 53, and the source is connected to ground potential VS via constant current source 74.
Connected to S. The source of NMOS 71 is NMO
The drain of the NMOS 72 is connected to the power supply potential VDD via the output node Nout and the resistor 73, and the source is connected to the ground potential VSS via the constant current source 75. The switch means 61 and 63 and the resistors 62 and 64 of FIG. 8 are omitted.

The switch means 65 is connected to the input node Nin.
And a capacitor 66 are connected in series.
6 is connected to a fixed potential (for example, the ground potential VSS). The input node Nin is connected to the bias voltage Vba via the switch 77 and the resistor 76. In the oscillation circuit shown in FIG.
Operates almost in the same manner as the Tr55 of
7 and the resistor 76 operate in the same manner as the switch means 61 and 63 and the resistors 62 and 64 in FIG. Even when the Colpitts-type oscillation circuit is constituted by FETs, substantially the same operation and effect as those of the oscillation circuit of FIG. 8 can be obtained.

(Modifications) The present invention is not limited to the above embodiment, and various modifications are possible. For example, there are the following modifications (1) to (3). (1) The quartz-crystal vibrators 15 and 51 may be replaced with another piezoelectric vibrator. At this time, the peripheral circuit may be appropriately changed according to the piezoelectric vibrator to be replaced. (2) PMOS for exciting and driving the crystal units 15 and 51
The switching element 13a, NMOS 13b, 26, 44, 71, 72 and Tr55 may be replaced by a switching element of another transistor. At this time, the peripheral circuit may be appropriately changed according to the replaced switching element. (3) PMOS 14a and NMOS 14 for controlling power supply to the drive units of the quartz oscillators 15 and 51
b and 25 may be constituted by switch means using other transistors. At this time, the peripheral circuits may be appropriately changed according to other switch means.

[0058]

As described above in detail, according to the first aspect, the power supply to the first and second switching elements is controlled by the first and second switch means by the control signal. Therefore, the output node side of the piezoelectric vibrator does not enter a floating state, and is not affected by external noise. Further, at the time of switching of the first and second switch means, since the load capacitance viewed from the output node side of the piezoelectric vibrator does not change, the oscillation of the piezoelectric vibrator is stopped, or the oscillation frequency, phase and amplitude are changed. Does not fluctuate. This reduces power consumption,
A stable oscillation operation can be performed.

According to the second aspect of the invention, the switching means is turned on / off by the control signal to control the supply of the power supply current to the switching element, so that substantially the same effect as in the first aspect of the invention is obtained. Can be According to the third invention,
After the first switch is turned on, the second switch is turned on, the signal inverting amplifier circuit is turned on, the second switch is turned off, and the first switch is turned off. The signal inverting amplifier circuit is set to the non-operating state to suppress the fluctuation of the load capacitance seen from the output node side of the piezoelectric vibrator when switching between the operating state and the non-operating state of the signal inverting amplifier circuit. While you can
Free vibration of the piezoelectric vibrator is not suppressed. As a result, the oscillation of the piezoelectric vibrator does not stop, or the oscillation frequency, phase and amplitude do not change, and a stable oscillation operation can be performed while reducing power consumption.

According to the fourth aspect of the present invention, the first and second switch means switch the operating state and the non-operating state of the switching element according to the control signal. Is obtained. According to the fifth aspect, the first and second switch means switch between the operating state and the non-operating state of the feedback amplifier by the control signal, so that substantially the same effects as in the third aspect can be obtained. . According to the sixth aspect of the invention, since the frequency dividing circuit is connected to the output node, for example, when a high-frequency vibrator having a small external shape is used as the piezoelectric vibrator, the frequency is divided by the frequency dividing circuit and the low-frequency output is obtained. Since the voltage can be set, the size and weight of the oscillation circuit can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an oscillation circuit using a CMOS inverter according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of an oscillation circuit using a conventional CMOS inverter.

FIG. 3 is a voltage waveform diagram of FIG.

FIG. 4 is a circuit diagram of an oscillation circuit using an NMOS inverter according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram of an oscillation circuit using a CMOS inverter according to a third embodiment of the present invention.

FIG. 6 is a voltage waveform diagram of FIG.

FIG. 7 is a circuit diagram of an oscillation circuit using an NMOS inverter according to a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram of a Colpitts oscillation circuit according to a fifth embodiment of the present invention.

FIG. 9 is a voltage waveform diagram of FIG.

FIG. 10 is a circuit diagram of a Colpitts oscillation circuit using FETs according to a sixth embodiment of the present invention.

[Explanation of symbols]

11, 11A switch control circuit 15, 51 crystal oscillator 13a, 14a PMOS 13b, 14b, 25, 26, 44, 71, 72N
MOS 19 frequency dividing circuit 31, 32, 33, 59, 60, 65 Switching means 55 Tr 70 Feedback amplifier

Claims (6)

[Claims] 1. A feedback circuit, comprising: a piezoelectric vibrator connected between an input node and an output node for outputting an output signal, wherein the feedback inverts the phase of the output signal output from the output node and returns the inverted signal to the input node. A first switching element that is connected between a first power supply potential and a first node and that is turned on / off by a signal on the input node to excite and drive the piezoelectric vibrator; The piezoelectric vibrator connected between a second power supply potential different from the first power supply potential and a second node, and turned on / off at a different timing from the first switching element by a signal on the input node; A second switching element for exciting and driving the first switching element, and connected between the first node and the output node;
First switch means for turning on / off by a first control signal to control power supply to the first switching element; connected between the output node and the second node;
And a second switch means for performing on / off operation by a second control signal at a timing different from the first control signal to control power supply to the second switching element. Oscillation circuit. 2. A feedback circuit, comprising: a piezoelectric vibrator connected between an input node and an output node for outputting an output signal, wherein the output signal output from the output node is inverted in phase and fed back to the input node. Circuit, connected between a first power supply potential and the input node, and turned on / off by a control signal to supply a constant power supply current to the input node when in an on state; A current supply circuit for stopping supply of the power supply current, connected between the input node and the drive node, and turned on / off at the same timing as the current supply circuit by the control signal to be in an on state; A switch for supplying a power supply current to the drive node and stopping the supply of the power supply current when the drive node is in an off state; and a switch connected between the drive node and a second power supply potential different from the first power supply potential. And said A switching element for turning on / off by an output signal to excite and drive the piezoelectric vibrator. 3. A feedback circuit comprising a piezoelectric vibrator connected between an input node and an output node for outputting an output signal, wherein the feedback inverts the phase of the output signal output from the output node and returns the output signal to the input node. A circuit connected between a first node and a second node, and when a power supply potential is applied, inverts and amplifies a signal on the first node and outputs the inverted signal to the second node; A signal inverting amplifier circuit for exciting and driving the piezoelectric vibrator, connected between the input node and the first node,
An on / off operation is performed by a first control signal to connect the input node to the first node when in an on state and to cut off the input node and the first node when in an off state. First switch means, connected between the second node and the output node,
On / off operation is performed by a second control signal synchronized with the first control signal, and the signal on the input node propagates to the second node after the first switch is turned on. After the elapse of the propagation delay time until the second switch is turned on, the second node is connected to the output node, and the first switch is turned off before the first switch is turned off. An oscillation circuit, comprising: a node and second switch means for cutting off the output node. 4. A feedback circuit having a piezoelectric vibrator connected between an input node and an output node for outputting an output signal, wherein the output signal output from the output node is inverted in phase and fed back to the input node. A current supply circuit connected between a first power supply potential and a first node, for supplying a constant power supply current to the first node; a second power supply different from the first power supply potential Potential and the first
A switching element that is turned on / off by a signal on a second node to excite and drive the piezoelectric vibrator, and that is connected between the input node and the second node. ,
An on / off operation is performed by a first control signal to connect the input node to the second node when in an on state, and to cut off the input node and the second node when in an off state. First switch means, connected between the first node and the output node,
On / off operation is performed by a second control signal synchronized with the first control signal, and the signal on the input node propagates to the first node after the first switch is turned on. After the elapse of the propagation delay time until the first node is turned on, the first node is connected to the output node, and the first switch is turned off before the first switch is turned off. An oscillation circuit, comprising: a node and second switch means for cutting off the output node. 5. A first and a second node having different potentials from an input node.
A piezoelectric vibrator and a first capacitor connected between the second power supply potential and the second power supply potential, and connected between the input node and the second power supply potential;
Second and third capacitors for dividing a signal between both ends of the piezoelectric vibrator and the first capacitor; a second node connected between the output node and the first node; A feedback amplifier that amplifies a signal on the second node with an amplification factor corresponding to a potential difference between the input node and the output node and outputs an output signal from the output node;
An on / off operation is performed by a first control signal to connect the input node to the second node when in an on state, and to cut off the input node and the second node when in an off state. First switch means, connected between the connection point of the second and third capacitors and the first node, and turned on / off by a second control signal synchronized with the first control signal; Then, after a delay time from when the first switch means is turned on to when the signal on the input node is amplified by the feedback amplifier and the output signal is output from the output node, the signal is turned on. A state in which the connection point is connected to the first node, and the first switch means is turned off before the first switch means is turned off to cut off the connection point and the first node. 2. Switch means, and Oscillation circuit. 6. A frequency divider circuit, which is connected to the output node according to claim 1 and divides an output signal output from the output node at a predetermined frequency division ratio. An oscillation circuit characterized by the above.