JP6576503B2 - Oscillator - Google Patents

Description

  The present invention relates to an oscillator capable of controlling an ambient temperature.

  Conventionally, an oven controlled crystal oscillator (hereinafter referred to as OCXO) having a temperature control circuit composed of a heater and a temperature sensor is known in order to keep the temperature of a crystal oscillation circuit using a crystal resonator constant (for example, OCXO) (for example, , See Patent Document 1).

JP 2005-92302 A

  By the way, OCXO can output an oscillation signal having higher frequency accuracy and stability than a temperature compensated crystal oscillator (hereinafter referred to as TCXO). However, in OCXO, an appropriate high temperature state is maintained by the heat generated in the heater, so it takes several minutes for the frequency to reach a stable state after the OCXO power supply is activated.

  The temperature control circuit includes a P control circuit, a PI control circuit, or a PID control circuit. In order to shorten the time until the frequency stabilizes, it is effective to increase the ratio of the heater output to the difference between the control target temperature and the actual temperature by increasing the gain value in the P control.

  However, when the gain value is increased, the feedback circuit operation becomes unstable in a stable state, and a vibration phenomenon occurs. Since the circuit becomes unstable when the vibration phenomenon occurs, it is necessary to use a gain value that is so small that the vibration phenomenon does not occur. Therefore, there is a restriction on the size of the heater output, and it takes a long time until the temperature reaches a stable state after the OCXO power supply is activated.

  Therefore, the present invention has been made in view of these points, and an object thereof is to shorten the time from when the power supply of the OCXO is started until the temperature reaches a stable state.

  An oscillator according to the present invention includes an oscillation unit that outputs an oscillation signal, a heat generation unit that heats the oscillation unit, a temperature detection unit that detects an ambient temperature of the oscillation unit, and a switching in which the ambient temperature is lower than a target temperature. A control unit that controls a heat generation amount of the heat generating unit by switching a gain of an amplifier that generates a heat generation control voltage applied to the heat generating unit at a temperature.

  The oscillator further includes an adjustment voltage generation unit that generates an adjustment voltage corresponding to the switching temperature, the temperature detection unit outputs a temperature detection voltage corresponding to the ambient temperature, and the control unit The gain may be determined based on a difference between a temperature detection voltage and the adjustment voltage.

  The control unit may make the gain at a temperature higher than the switching temperature larger than the gain at a temperature equal to or lower than the switching temperature. The control unit may switch the gain at the switching temperature closer to the target temperature than 25 ° C.

  The control unit includes the amplifier that amplifies a comparison voltage indicating a difference between the temperature detection voltage and a reference voltage with the gain, and the control unit is configured such that the comparison voltage is the adjustment voltage. When the voltage is higher than the first voltage, the gain of the amplifier is set to the first gain by not short-circuiting the resistor that determines the gain of the amplifier, the comparison voltage is the adjustment voltage, and the temperature detection voltage is the adjustment voltage. When the second voltage indicates the following state, the heat generation amount of the heat generating unit may be controlled by short-circuiting the resistor so that the gain of the amplifier is a second gain smaller than the first gain. .

  According to the present invention, there is an effect that it is possible to shorten the time from when the power supply of the OCXO is activated until the temperature reaches a stable state.

It is a figure which shows the structure of the oscillator which concerns on 1st Embodiment. It is a figure which shows the structure of the control part which concerns on 1st Embodiment. It is a figure which shows the relationship between the temperature detection voltage after power-on of an oscillator, and a heat generation control voltage when the gain of a control part is set to 4 times. It is a figure which shows the relationship between the temperature detection voltage after power activation of an oscillator, and a heat generation control voltage when the gain of a control part is set to 60 times. It is a figure which shows the relationship between the temperature detection voltage after power-on of an oscillator, and a heat generation control voltage at the time of switching temperature, when the gain of a control part is switched from 60 times to 4 times.

<First Embodiment>
FIG. 1 is a diagram illustrating a configuration of an oscillator 100 according to the first embodiment. The oscillator 100 includes an oscillation unit 1, a heat generation unit 2, a temperature detection unit 3, a reference voltage generation unit 4, an adjustment voltage generation unit 5, a comparison unit 6, and a control unit 7.

  The oscillation unit 1 is an oscillation circuit that outputs an oscillation signal. The oscillation unit 1 includes, for example, a crystal resonator or a MEMS resonator, and an amplifier circuit for causing the resonator to oscillate. The oscillation unit 1 is heated by the heat generation unit 2.

  The heat generating unit 2 is a heater that heats the oscillation unit 1. The heat generating unit 2 heats the periphery of the oscillating unit 1 by generating a heat amount corresponding to the heat generation control voltage output from the control unit 7. The heat generating unit 2 generates heat so as to maintain the ambient temperature of the oscillation unit 1 at 80 ° C., for example.

  The temperature detection unit 3 is a temperature sensor that detects the ambient temperature of the oscillation unit 1 and outputs a temperature detection voltage corresponding to the detected ambient temperature. A temperature detection voltage signal output from the temperature detection unit 3 is input to the control unit 7 and the comparison unit 6.

  The reference voltage generator 4 generates a reference voltage associated with the target temperature of the ambient temperature. Specifically, the reference voltage generation unit 4 generates the temperature detection voltage output from the temperature detection unit 3 as the reference voltage when the ambient temperature is equal to the target temperature. The reference voltage generation unit 4 may have a table in which the target temperature and the reference voltage are associated with each other, and may generate a reference voltage corresponding to the target temperature acquired from the outside.

  The adjustment voltage generator 5 is a level shift circuit that adjusts the voltage level of the reference voltage to generate an adjustment voltage. The adjustment voltage generator 5 is configured by, for example, an operational amplifier or a transistor. The adjustment voltage generator 5 generates an adjustment voltage corresponding to a temperature lower than the target temperature of the ambient temperature. Specifically, when the temperature detection voltage output from the temperature detection unit 3 decreases as the ambient temperature increases, the adjustment voltage generation unit 5 generates an adjustment voltage whose voltage is higher than the reference voltage. For example, when the target temperature is 80 ° C. and the room temperature when the oscillator 100 is turned on is 25 ° C., the adjustment voltage is a voltage corresponding to a temperature 60 ° C. that is higher than the room temperature and lower than the target temperature. In the present specification, the temperature corresponding to the adjustment voltage is referred to as a switching temperature.

  The comparison unit 6 is a comparator that compares the temperature detection voltage with the adjustment voltage. The comparison unit 6 receives the temperature detection voltage output from the temperature detection unit 3 and the adjustment voltage output from the adjustment voltage generation unit 5 and outputs a comparison voltage corresponding to the comparison result between the temperature detection voltage and the adjustment voltage. For example, when the temperature detection voltage is higher than the adjustment voltage, the comparison unit 6 outputs a voltage corresponding to a low level logic value (hereinafter referred to as a low level voltage), and when the temperature detection voltage is equal to or less than the adjustment voltage. , A voltage corresponding to a high level logic value (hereinafter referred to as a high level voltage) is output.

  The control unit 7 controls the heat generating unit 2 based on the comparison voltage. The control unit 7 keeps the ambient temperature of the oscillation unit 1 at a constant temperature by inputting the heat generation control voltage generated based on the comparison voltage to the heat generation unit 2 to control the heat generation unit 2. The control unit 7 controls the heat generating unit 2 based on a heat generation control voltage obtained by amplifying the differential voltage between the temperature detection voltage and the reference voltage with a gain determined based on the comparison voltage output from the comparison unit 6. .

  Specifically, when the comparison voltage is a low level voltage, the control unit 7 amplifies a differential voltage between the temperature detection voltage and the reference voltage by a first gain (for example, 60 times), thereby generating a heat generation control voltage. Is generated. When the comparison voltage is a high level voltage, the control unit 7 amplifies the differential voltage between the temperature detection voltage and the reference voltage with a second gain (for example, four times) smaller than the first gain. , Generate heat generation control voltage.

  For example, when the target temperature is 80 ° C. and the switching temperature is 60 ° C., the control unit 7 amplifies the differential voltage with a gain of 60 times when the ambient temperature detected by the temperature detection unit 3 is 60 ° C. or less. When the ambient temperature is higher than 60 ° C., the differential voltage is amplified with a gain of 4 times. By doing in this way, when the ambient temperature is lower than the switching temperature, the heat generation amount of the heat generating unit 2 is maximized, so that the ambient temperature rises rapidly, and when the ambient temperature exceeds the switching temperature, the heat generating unit 2 Since the amount of heat generated is suppressed, the rate of increase in ambient temperature decreases. As a result, the ambient temperature is prevented from oscillating unstable.

  FIG. 2 is a diagram illustrating a configuration of the control unit 7. The control unit 7 includes an amplifier 71 that outputs a differential voltage between the temperature detection voltage input from the temperature detection unit 3 and the reference voltage input from the reference voltage generation unit 4. A resistor 72 is provided between the first input terminal of the amplifier 71 and the temperature detection unit 3, and a resistor 73 is provided between the second input terminal of the amplifier 71 and the reference voltage generation unit 4. .

  The control unit 7 has a circuit for switching the gain of the amplifier 71. Specifically, a resistor 74 and a resistor 75 connected in series with each other are provided between the first input terminal and the output terminal of the amplifier 71. Further, a gain switching switch 76 is provided in parallel with the resistor 75. The switch 76 is, for example, a CMOS analog switch. The switch 76 switches between a conduction state and a non-conduction state according to the comparison voltage output from the comparison unit 6. For example, the switch 76 becomes non-conductive when the comparison voltage is a low-level voltage, and becomes conductive when the comparison voltage is a high-level voltage.

  A resistor 77 and a resistor 78 connected in series with each other are provided between the second input terminal of the amplifier 71 and the ground. A gain switching switch 79 is provided in parallel with the resistor 78. Similarly to the switch 76, the switch 79 switches between a conduction state and a non-conduction state according to the comparison voltage output from the comparison unit 6.

  When the comparison voltage is a low level voltage, the resistor 75 and the resistor 78 are not short-circuited, and when the comparison voltage is a high-level voltage, the resistor 75 and the resistor 78 are short-circuited. Therefore, the gain of the amplifier 71 is large while the ambient temperature is lower than the switching temperature, and the gain of the amplifier 71 is small while the ambient temperature is higher than the switching temperature. As a result, the control unit 7 generates the maximum amount of heat in the heat generating unit 2 while the ambient temperature is lower than the switching temperature, and suppresses the amount of heat generated by the heat generating unit 2 when the ambient temperature becomes higher than the switching temperature. Can do.

  FIG. 3 is a diagram illustrating a relationship between the temperature detection voltage and the heat generation control voltage after the power of the oscillator 100 is turned on when the gain of the control unit 7 is set to four times. FIG. 4 is a diagram illustrating a relationship between the temperature detection voltage and the heat generation control voltage after the oscillator 100 is turned on when the gain of the control unit 7 is set to 60 times. FIG. 5 is a diagram illustrating the relationship between the temperature detection voltage and the heat generation control voltage after the oscillator 100 is turned on when the gain of the control unit 7 is switched from 60 times to 4 times at the switching temperature.

  3, 4, and 5, the horizontal axis indicates the elapsed time since the power of the oscillator 100 is turned on, and the vertical axis indicates the voltage. Further, the broken lines in FIGS. 3, 4 and 5 indicate the temperature detection voltage, and the solid line indicates the heat generation control voltage.

  In FIG. 3, the heat generation control voltage is saturated until 400 seconds after the power is turned on, and is equal to the power supply voltage of 3.3V. Thereafter, the heat generation control voltage decreases, and the temperature detection voltage and the heat generation control voltage become constant about 750 seconds after the power is turned on. That is, it can be considered that the detected temperature is stabilized at the target temperature.

  In FIG. 4, the heat generation control voltage is 3.3 V until about 500 seconds elapse after the power is turned on, and thereafter, the heat generation control voltage is sharply decreased. When about 550 seconds have elapsed since the power was turned on, the heat generation control voltage oscillates. When the heat generation control voltage vibrates, the heat generation amount of the heat generating unit 2 becomes unstable, and the ambient temperature of the oscillation unit 1 becomes unstable. The temperature detection voltage becomes constant about 550 seconds after the power is turned on. Although the detected temperature seems to be constant near the target temperature, it is not preferable because the control system is unstable.

  When acquiring the data shown in FIG. 5 according to the present embodiment, the gain is switched from 60 times to 4 times when the ambient temperature reaches 80 ° C. which is the same as the target temperature (time A in FIG. 5). Yes. As a result, the temperature detection voltage is stable about 550 seconds after the power is turned on, and is stabilized about 150 seconds earlier than in FIG. Moreover, the heat generation control voltage is stabilized about 650 seconds after the power is turned on after sharply decreasing. Thus, according to the present embodiment, the ambient temperature can reach the target temperature in a short time, and the ambient temperature can be stabilized.

<Second Embodiment>
In the first embodiment, the comparison unit 6 switches the comparison voltage when the temperature detection voltage is equal to the adjustment voltage. For example, the comparison unit 6 switches the comparison voltage from the low level voltage to the high level voltage when the ambient temperature reaches 80 ° C.

  The comparison unit 6 according to the second embodiment is different from the first embodiment in that it has hysteresis. Specifically, the comparison unit 6 changes the comparison voltage from the first value to the second value when the temperature detection voltage changes to be greater than the adjustment voltage and the temperature detection voltage becomes equal to the first reference voltage. When the temperature detection voltage changes to be smaller than the adjustment voltage and the temperature detection voltage becomes equal to a second reference voltage different from the first reference voltage, the comparison voltage is changed from the second value to the first value. Switch to the value of.

  For example, the first reference voltage is a voltage corresponding to an ambient temperature of 80 ° C., and the second reference voltage is a voltage corresponding to an ambient temperature of 75 ° C. In this case, the comparison unit 6 switches the comparison voltage from the low level voltage to the high level voltage when the ambient temperature rises and reaches 80 ° C., and the control unit 7 switches the gain from 60 times to 4 times. Thereafter, when the ambient temperature exceeds 80 ° C. and then temporarily changes to a temperature lower than 80 ° C., the comparison unit 6 switches the comparison voltage from the high level voltage to the low level voltage when the ambient temperature is 80 ° C. Without maintaining a high level voltage. When the ambient temperature further decreases and reaches 75 ° C., the comparison unit 6 switches the comparison voltage from the high level voltage to the low level voltage.

  Thus, by providing hysteresis to the operation of the comparison unit 6, when the temperature fluctuates in the vicinity of the switching temperature for switching the gain, it is possible to prevent the gain from being switched frequently and falling into an unstable state. .

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  For example, in the above embodiment, the adjustment voltage output from the adjustment voltage generator 5 is input to the second input terminal of the comparison unit 6, but the adjustment voltage is input to the second input terminal from the outside. May be. Moreover, the adjustment voltage generation part 5 may switch adjustment voltage by control from the outside.

DESCRIPTION OF SYMBOLS 1 ... Oscillation part, 2 ... Heat generation part, 3 ... Temperature detection part, 4 ... Reference voltage generation part, 5 ... Adjustment voltage generation part, 6 ... Comparison part, ... Control unit 71 ... Amplifier 72, 73, 74, 75, 77, 78 ... Resistor 76, 79 ... Switch, 100 ... Oscillator

Claims (4)

An oscillation unit for outputting an oscillation signal;
A heat generating unit for heating the oscillation unit;
A temperature detection unit for detecting an ambient temperature of the oscillation unit;
A control unit that controls a heat generation amount of the heat generating unit by switching a gain of an amplifier that generates a heat generation control voltage applied to the heat generating unit at a switching temperature at which the ambient temperature is lower than a target temperature;
Have
The said control part is an oscillator which makes the gain of the said amplifier in the temperature higher than the said switching temperature smaller than the said gain in the temperature below the said switching temperature. An adjustment voltage generator for generating an adjustment voltage corresponding to the switching temperature;
The temperature detection unit outputs a temperature detection voltage corresponding to the ambient temperature,
The control unit determines the gain based on a difference between the temperature detection voltage and the adjustment voltage.
The oscillator according to claim 1. The control unit switches the gain at the switching temperature closer to the target temperature than 25 ° C.
The oscillator according to claim 1 or 2 . The control unit includes the amplifier that amplifies a comparison voltage indicating a difference between the temperature detection voltage and a reference voltage with the gain, and the control unit is configured such that the comparison voltage is the adjustment voltage. When the voltage is higher than the first voltage, the gain of the amplifier is set to the first gain by not short-circuiting the resistor that determines the gain of the amplifier, and the comparison voltage is the adjustment voltage. When the second voltage indicates the following state, the heating value of the heating unit is controlled by setting the gain of the amplifier to a second gain smaller than the first gain by short-circuiting the resistor.
The oscillator according to claim 2.

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