JP4296982B2 - Oscillator circuit - Google Patents

Description

  The present invention relates to an oscillation circuit, and more particularly to an oscillation circuit that controls an oscillation frequency according to a voltage.

  FIG. 4 shows a circuit configuration diagram of an example of the prior art.

  The voltage-controlled oscillation circuit 1 is structured as a unit on a circuit board, and includes a compensation voltage generation circuit 11, a low-pass filter 12, a vibrator 13, an oscillation circuit 14, resistors R11 and R12, a variable capacitance diode D1, D2 is included.

  The compensation voltage generation circuit 11 is a so-called temperature compensation circuit, which includes a thermistor, a diode for a temperature sensor, and the like, and corresponds to the temperature of the frequency of the oscillation output of the voltage controlled oscillation circuit 14 output from the output terminal Tout. Generate a voltage to compensate for the variation. The compensation voltage generated by the compensation voltage generation circuit 11 is supplied to the low-pass filter 12.

  The low pass filter 12 includes a resistor R1 and a capacitor C1. The low pass filter 12 removes the high frequency component of the compensation voltage. The compensation voltage from which the high-frequency component has been removed by the low-pass filter 12 is applied to the cathode of the variable capacitance diode D1 through the resistor R11 and to the cathode of the variable capacitance diode D2 through the resistor R12.

  The variable capacitance diode D <b> 1 has an anode connected to the ground terminal TGND and a cathode connected to one end of the vibrator 13 and the oscillation circuit 14. In the variable capacitance diode D1, the depletion layer is varied by the compensation voltage, and the capacitance changes.

  The variable capacitance diode D2 has an anode connected to the ground terminal TGND and a cathode connected to the other end of the vibrator 13 and the voltage-controlled oscillation circuit 14. The capacitance of the variable capacitance diode D2 changes due to the depletion layer being changed by the compensation voltage.

  When the capacitance components of the variable capacitance diodes D1 and D2 change, the capacitance component of the resonance circuit changes, and the oscillation frequency of the oscillation output output from the output terminal Tout changes. Therefore, the oscillation frequency of the oscillation output output from the output terminal Tout can be controlled by the compensation voltage.

  The voltage controlled oscillator circuit 1 has a control terminal Tcnt. A power supply voltage Vcc for driving the voltage controlled oscillation circuit 1 is supplied to the control terminal Tcnt. The voltage controlled oscillation circuit 1 is controlled to be driven according to the power supply voltage Vcc supplied to the control terminal Tcnt.

  At this time, when the voltage-controlled oscillation circuit 1 is mounted on a battery-powered device such as a cellular phone, the power supply voltage Vcc is intermittently supplied to the control terminal Tcnt to cause the oscillation to occur intermittently. Power is being reduced.

  FIG. 5 is a diagram for explaining the operation of a conventional example. FIG. 5A shows the voltage applied to the control terminal Tcnt, and FIG. 5B shows the oscillation output from the output terminal Tout.

  As shown in FIG. 5A, the power supply voltage Vcc is intermittently applied to the control terminal Tcnt. The voltage controlled oscillation circuit 1 performs an oscillation operation when the power supply voltage Vcc is applied to the control terminal Tcnt, outputs an oscillation signal from the output terminal Tout, and outputs when the power supply voltage Vcc is not applied to the control terminal Tcnt. The output of the oscillation signal from the terminal Tout is stopped.

  In the voltage controlled oscillation circuit 1 in which the intermittent operation is performed, it is necessary to speed up the start-up. However, in the voltage controlled oscillation circuit 1, it takes time until the oscillation output reaches a predetermined frequency because the compensation voltage is delayed by the capacitor C1 of the low-pass filter 12.

  FIG. 6 shows an operation waveform diagram at the time of starting of an example of the prior art.

  Assuming that the power supply voltage Vcc rises at time t0, the oscillation frequency once drops below the center frequency f0 and gradually approaches the center frequency f0 as shown in FIG. 6 due to the delay of the compensation voltage by the capacitor C1 constituting the low-pass filter 12. It shows such characteristics as

  At this time, for example, when the compensation voltage is 0.4 to 2.0 [V], the resistance value of the resistor R1 constituting the low-pass filter 12 is 100 k [Ω], and the capacitance of the capacitor C1 is about 0.1 μ [F]. A delay of about 5 msec occurs until the oscillation frequency stabilizes within 0.5 ppm from the center frequency f0. There has been a demand for a mobile phone or the like to be suppressed to about 1 msec.

  For this reason, in this type of oscillation circuit, in order to stabilize the oscillation frequency at a high speed, a capacitor is provided in the low-pass filter by providing a switch in parallel with the resistance of the low-pass filter and turning on the switch for a predetermined time at startup. Has been proposed (Patent Document 1).

JP 2000-196356 A

  However, an oscillation circuit configured to shorten the startup time by providing a switch in parallel with the resistance of the conventional low-pass filter and turning on the switch for a predetermined time at startup to quickly charge the capacitor constituting the low-pass filter. Since the time is determined in advance, there is a problem in that the capacitor C1 cannot be sufficiently charged due to variations in elements or the like, and a delay occurs due to generation of phase noise due to the charging time being too long. .

  Further, the capacitor C1 is charged by the compensation voltage itself. For this reason, when sufficient current supply capability cannot be secured for the voltage source on the compensation voltage side, there is a problem that the effect cannot be exhibited.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an oscillation circuit capable of high-speed startup while having sufficient phase noise removal capability.

The present invention relates to a control voltage generating means (11) for generating a control voltage, a filter means (12) for filtering the control voltage generated by the control voltage generating means (11), and an output voltage of the filter means (12). When the output voltage of the filter means (12) is lower than the output voltage of the control voltage generation means (11) in the oscillation circuit having the oscillation means (13, 14, D1, D2) whose oscillation frequency is controlled by capacitive component of the filter unit (12) and (C1) possess substantially charging means for fast charging until it equals the (111) the output voltage of the output voltage of the filter means (12) is a control voltage generating means (11), further, The charging means (111) includes a comparator (121) for comparing the output voltage of the filter means (12) and the output voltage of the control voltage generating means (11), and the output of the comparator (121) is a gate. And when the output of the comparator (121) indicates that the output voltage of the filter means (12) is smaller than the output voltage of the control voltage generating means (11), the capacitance of the filter means (12) is turned on. When the component (C1) is charged by the power supply (Vcnt) and the output of the comparator (121) indicates that the output voltage of the filter means (12) is greater than the output voltage of the control voltage generating means (11), it is turned off. characterized Rukoto to have a field effect transistor to be stopped (M1) to charge the capacitive component of the filter unit (12) and.

The charging means (111) is characterized by charging the capacitance component (C1) of the filter means (12) with a power supply voltage. The charging unit (111) includes a charging voltage generation unit (222) that generates a charging voltage based on the power supply voltage, and the capacitance component of the filter unit (12) is generated by the charging voltage generated by the charging voltage generation unit (222). (C1) is charged.

  In addition, the said reference code is a reference to the last, This does not limit a claim.

According to the present invention, when the output voltage of the filter means and the output voltage of the control voltage generation means are compared by the comparator, and the output voltage of the filter means indicates a state smaller than the output voltage of the control voltage generation means, the field effect When the transistor is turned on and the capacitive component of the filter means is charged by the power supply by the power supply, and the output voltage of the filter means indicates a state larger than the output voltage of the control voltage generating means, the field effect transistor is turned off, With the configuration in which charging to the capacitive component is stopped , the capacitive component can be reliably charged even if the capacitive component of the filter means is set large. In addition, since the control voltage can be reliably charged, the oscillation frequency can be stabilized at a high speed according to the control voltage. As described above, according to the present invention, there is a feature that high-speed startup can be performed while sufficient phase noise and removal capability are provided.

[First embodiment]
FIG. 1 shows a circuit configuration diagram of a first embodiment of the present invention. In the figure, the same components as those in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted.

  The voltage control type oscillation circuit 100 of this embodiment includes a compensation voltage generation circuit 11, a low-pass filter 12, a vibrator 13, a voltage control type oscillation circuit 14, resistors R11 and R12, variable capacitance diodes D1 and D2, and a charging circuit. 111 is provided.

  The charging circuit 111 includes a comparator 121 and a MOS transistor M1. In the comparator 121, the compensation voltage generated by the compensation voltage generation circuit 11 is applied to the non-inverting input terminal, and the output voltage of the low-pass filter 12 is applied to the inverting input terminal. In other words, the comparator 121 is configured to invert the output in accordance with the voltage difference between the both ends of the resistor R1 constituting the low-pass filter 12 as a detection resistor.

  The comparator 121 sets the output to a high level if the compensation voltage generated by the compensation voltage generation circuit 11 is greater than the output voltage of the low-pass filter 12, and the compensation voltage generated by the compensation voltage generation circuit 11 is the output voltage of the low-pass filter 12. If it is smaller, the output is set to low level.

  The output of the comparator 121 is supplied to the gate of the MOS transistor M1. The MOS transistor M1 constitutes a switch means, which is turned on when the output of the comparator 121 is at a high level and turned off when the output of the comparator 121 is at a low level. The source-drain of the MOS transistor M1 is connected between the control terminal Tcnt and a connection point between the resistor R1 and the capacitor C1 constituting the low-pass filter 12.

  Next, the operation at the time of starting up the charging circuit 111 will be described.

  When the control voltage Vcnt is applied to the control terminal Tcnt, the control voltage Vcnt is applied to the compensation voltage generation circuit 11, the oscillation circuit 14, the comparator 121, and the MOS transistor M1. The compensation voltage generation circuit 11, the oscillation circuit 14, the comparator 121, and the MOS transistor M1 are driven almost instantaneously by the control voltage Vcnt.

  The compensation voltage generation circuit 11 is driven by the control voltage Vcnt to generate a compensation voltage. The compensation voltage generated by the compensation voltage generation circuit 11 is supplied to the low-pass filter 12. At this time, the capacitor C1 and the variable capacitance diodes D1 and D2 of the low-pass filter 12 are in a discharged state, and the potential at the connection point between the resistor R1 and the capacitor C1 of the low-pass filter 12 is substantially the ground potential. For this reason, a potential difference is generated between both ends of the resistor R1. As a result, the output of the comparator 121 becomes high level. When the output of the comparator 121 becomes high level, the MOS transistor M1 is turned on. When the MOS transistor M1 is turned on, the control voltage Vcnt is directly applied to the capacitor C1, and the capacitor C1 is charged at high speed.

  At this time, the control voltage Vcnt is applied not only to the capacitor C1 of the low-pass filter 12 but also to the variable capacitance diodes D1 and D2 via the resistors R11 and R12. As a result, the variable capacitance diodes D1 and D2 are also charged at high speed. Further, the control voltage Vcnt is applied not only to the variable capacitance diodes D1 and D2, but also to the vibrator 13 and the oscillation circuit 14, and the capacitive components of the vibrator 13 and the oscillation circuit 14 can be charged at high speed. .

  When the capacitive component including the capacitor C1 and the variable capacitance diodes D1 and D2 is charged to the compensation voltage, the potential difference between both ends of the resistor R1 becomes zero. As a result, the output of the comparator 121 becomes low level. When the output of the comparator 121 becomes low level, the MOS transistor M1 is turned off. When the MOS transistor M1 is turned off, the compensation voltage generated by the compensation voltage generation circuit 11 is applied to the variable capacitance diodes D1 and D2, the capacitances of the variable capacitance diodes D1 and D2 are controlled, and the oscillation frequency of the output terminal Tout is controlled. Is done.

  As described above, at the time of start-up, initially, the rising of the capacitance component of the voltage-controlled oscillation circuit 100 can be speeded up by the control voltage Vcnt so that the rise time can be increased. , The high-speed charging operation of the capacitance component of the voltage controlled oscillation circuit 100 by the control voltage Vcnt is automatically stopped, and the voltage controlled oscillation circuit 100 can be stably operated according to the compensation voltage.

  At this time, according to this embodiment, since the charging voltage is obtained from the control voltage Vcnt supplied to the control terminal Tcnt, if the current supply capability of the external circuit that supplies the control voltage Vcnt is set high, the high speed Charging becomes possible. For this reason, it is not necessary to set the current supply capability of the compensation voltage generation circuit 11 high.

  FIG. 2 is a diagram for explaining the operation of the first embodiment of the present invention.

  When the control voltage Vcnt is applied to the control terminal Tcnt at time t10, the capacitive components including the variable capacitance diodes D1 and D2 including the capacitor C1 of the low-pass filter 12 are charged at high speed, and the oscillation signal output from the output terminal Tout Gradually approaches the center frequency f0. At time t11, Δf reaches 0.5 ppm from the center frequency f0. At this time, in the present embodiment, the oscillation frequency is reduced by rapidly charging the capacitance component including the variable capacitance diodes D1 and D2 including the capacitor C1 of the low-pass filter 12 with the control voltage Vcnt, thereby reaching the compensation voltage at a high speed. Since the frequency approximates the center frequency f0 without swinging up and down the center frequency f0, the oscillation frequency can be set to the center frequency f0 at high speed. For this reason, for example, the time T10 from the time t10 to the time t11 can be shortened from about 5 msec to about 1.6 msec.

[Second Embodiment]
FIG. 3 shows a circuit configuration diagram of a second embodiment of the present invention. In FIG. 3, the same components as those in FIG.

  The voltage controlled oscillation circuit 200 of this embodiment is different from the first embodiment in the configuration of the charging circuit 211. The charging circuit 211 according to the present embodiment includes a voltage generation circuit 222 that generates a charging voltage from the control voltage Vcnt, and is configured to charge a capacitance component with the charging voltage generated by the voltage generation circuit 222. The voltage generation circuit 222 includes a stabilized power supply circuit, and is configured to generate a stable charging voltage.

  According to the present embodiment, since the charging voltage can be stabilized by generating the charging voltage by the voltage generating circuit 222, it is possible to prevent the startup time from fluctuating due to variations in the control voltage Vcnt.

[Others]
In the first and second embodiments, the temperature compensation circuit is used as the compensation voltage generation circuit 11, but the compensation voltage generation circuit 11 is not limited to the temperature compensation circuit. The point is that the control voltage may be supplied to the oscillation circuit via the low-pass filter 12.

It is a circuit block diagram of 1st Example of this invention. It is operation | movement explanatory drawing of 1st Example of this invention. It is a circuit block diagram of 2nd Example of this invention. It is a circuit block diagram of a conventional example. It is operation | movement explanatory drawing of an example of the past. It is an operation | movement waveform diagram at the time of starting of an example of the past.

Explanation of symbols

100, 200 Voltage control type oscillation circuit 11 Compensation voltage generation circuit, 12 Low pass filter, 13 Oscillator, 14 Oscillation circuit D1, D2 Variable capacitance diode, R1, R11, R12 resistance, C1 Capacitor 111, 211 Charging circuit 121 Comparator, M1 MOS transistor 222 voltage generation circuit

Claims (4)

An oscillation circuit having control voltage generation means for generating a control voltage, filter means for filtering the control voltage generated by the control voltage generation means, and oscillation means whose oscillation frequency is controlled according to the output voltage of the filter means In
When the output voltage of the filter means is lower than the output voltage of the control voltage generating means, the capacitor component of the filter means is charged at high speed until the output voltage of the filter means becomes substantially equal to the output voltage of the control voltage generating means. the charging means to possess,
Further, the charging means, a comparator for comparing the output voltage of the filter means and the output voltage of the control voltage generating means,
When the output of the comparator is supplied to the gate and the output of the comparator indicates that the output voltage of the filter means is lower than the output voltage of the control voltage generating means, the capacitance component of the filter means is turned on. Is turned off when the output of the comparator indicates that the output voltage of the filter means is higher than the output voltage of the control voltage generating means, and charging to the capacitive component of the filter means is stopped. oscillator circuit according to claim Rukoto to have a field effect transistor. It said charging means, an oscillation circuit according to claim 1, wherein the the power supply voltage to charge the capacitive component of the filter means. The charging unit includes a charging voltage generating unit that generates a charging voltage by stabilizing a power supply voltage,
Oscillator circuit according to claim 1, characterized in that charging the capacitive component of the filter means by the charging voltage generated by the charge voltage generator. The control voltage generating means, an oscillation circuit of any one of claims 1 to 3 a voltage to compensate for variations in response to the temperature of the output frequency and generating as the control voltage of the oscillator means.

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