JP4852969B2 - Oscillator circuit - Google Patents

Description

  The present invention relates to an oscillation circuit, and more particularly to an oscillation circuit including a compensation circuit that generates a compensation signal and an oscillation unit that can control an oscillation frequency in accordance with the compensation signal from the compensation circuit.

  A reference oscillation source such as a cellular phone is required to oscillate with high accuracy. For this reason, a temperature compensated oscillator is used as a reference oscillation source (see Patent Document 1). Further, in a cellular phone or the like, the temperature compensated oscillator is operated intermittently to reduce power consumption and efficiency. It is desired that an oscillator that operates intermittently in this way be stabilized at a desired frequency at high speed.

The temperature compensated oscillator stabilizes the compensation operation by supplying a compensation signal to the oscillation unit through an integration circuit. At this time, in order to improve the starting characteristics and phase characteristics of the oscillation circuit, an oscillation circuit has been proposed in which the resistance of the integration circuit is short-circuited and a compensation signal is directly supplied to the capacitance (Patent Document 1).
JP 2000-196356 A

  However, the conventional temperature-compensated oscillation circuit cannot sufficiently start up.

  The present invention has been made in view of the above points, and an object thereof is to provide an oscillation circuit that can be stabilized at a desired frequency at high speed.

The present invention is an oscillation circuit having a compensation circuit (122) for generating a compensation signal and an oscillation unit (121) whose oscillation frequency can be controlled in accordance with the compensation signal from the compensation circuit (122). An integration circuit (R1, C2) that includes a resistor (R1) and a capacitor (C2) and supplies an integrated waveform of the compensation signal to the oscillation unit (121), and a comparison circuit (141) that compares the voltages across the resistor (R1). ) And when the power supply voltage is applied, charging of the capacitor (C2) is started. When the comparison result by the comparison circuit (141) shows that the voltages at both ends of the resistor (R1) match, charging of the capacitor (C2) is started. A charging circuit (123) to be stopped ;
The switch circuit (124) for short-circuiting both ends of the resistor (R1) included in the integrating circuit (R1, C2), and after the charging of the capacitor (C2) by the charging circuit (123) is stopped , the switch circuit (124) And a control circuit (125) for short-circuiting a resistor (R1) included in the integration circuit (R1, C2) for a predetermined time .

  The charging circuit (123) compares the charging voltage of the capacitor (C2) with the compensation signal, and ends the charging of the capacitor (C2) when the charging voltage of the capacitor (C2) reaches the level of the compensation signal. It is characterized by that.

  The control circuit (125) is characterized by short-circuiting the resistor (R1) by the switch circuit (124) for a predetermined time after the charging of the capacitor (C2) by the charging circuit (123) is completed.

  The control circuit (125) sets the charging circuit (123) and the switch circuit (124) so that the charging period of the capacitor (C2) by the charging circuit (123) and the short circuit period of the resistor by the switch circuit (124) do not overlap. It is characterized by controlling.

  The control circuit (125) charges the capacitor (C2) at the start of the oscillation operation, and after the charging of the capacitor (C2) by the charging circuit (123) is completed, the switch circuit (124) sets the resistor (R1) for a predetermined time. It is short-circuited.

  In addition, the said reference code is a reference to the last, and description of a claim is not limited by this.

According to the present invention, an oscillation circuit having a compensation circuit that generates a compensation signal, and an oscillation unit whose oscillation frequency can be controlled in accordance with the compensation signal from the compensation circuit, including a resistor and a capacitor, an integrating circuit for supplying the integrated waveform to the oscillation portion of the compensation signal, and a comparator circuit for comparing the voltage across the resistor, to begin charging the pre-crisis Yapashita when the power supply voltage is applied, the comparator circuit As a result of the comparison, a charging circuit that stops charging of the capacitor when the voltages at both ends of the resistor match, a switch circuit that short-circuits both ends of the resistor included in the integrating circuit, and the capacitor of the capacitor by the charging circuit after the charging is stopped, with the structure and a control circuit for a predetermined time shorting the resistors included in the integrating circuit by the switching circuit, of the oscillator oscillation output Speed, it is possible to stabilize.

[Oscillation circuit]
FIG. 1 shows a block diagram of an embodiment of the present invention.

  The oscillation circuit 100 according to this embodiment includes an oscillation IC 111, a power source 112, an oscillator 113, and capacitors C1 and C2.

  The oscillation IC 111 is an oscillation IC with a temperature compensation function, and is configured to obtain an oscillation output of a desired frequency regardless of the temperature by controlling the capacitance according to the ambient temperature. A power source 112 is connected to a terminal T1 of the oscillation IC 111. The power source 112 supplies the DC voltage Vcc to the terminal T1 of the oscillation IC 111.

  Capacitance C1 is connected in parallel to power source 112 and absorbs fluctuations in DC voltage Vcc supplied from power source 112.

  An oscillator 113 is connected between the terminal T2 and the terminal T3 of the oscillation IC 111. The oscillator 113 is composed of a ceramic oscillator, a crystal oscillator, or the like, and vibrates according to the voltage applied to the terminals T2 and T3.

  The oscillation IC 111 outputs an oscillation output corresponding to the vibration of the oscillator 113 from the terminal T6. A terminal T4 of the oscillation IC 111 is grounded via the capacitor C2. The capacitor C2 is an external capacitor and constitutes an integration circuit together with a built-in resistor. A terminal T5 of the oscillation IC 111 is a ground terminal and is grounded.

[Oscillation IC 111]
The oscillation IC 111 is, for example, a one-chip semiconductor device, and includes an oscillation unit 121, a temperature compensation circuit 122, a charging circuit 123, a switch circuit 124, a timing control circuit 125, and a resistor R1.

[Oscillator 121]
The oscillating unit 121 includes an inverter 131, a buffer amplifier 132, resistors R11 to R14, capacitors C11 and C12, and variable capacitance diodes Cav1 and Cav2, and constitutes a so-called inverter type voltage controlled oscillation circuit. The inverter 131 has an input connected to the terminal T2 via the capacitor C11, and an output connected to the terminal T3 via the resistor R14 and the capacitor C12.

  The voltage is inverted between the terminal T2 and the terminal T3. The output of the inverter 131 is output from the terminal T6 via the buffer amplifier 132 as an oscillation output.

  The variable capacitance diode Cav1 is provided between the terminal T2 and the terminal T5. The variable capacitance diode Cav2 is provided between the terminal T3 and the terminal T5.

  The capacitance components of the variable capacitance diodes Cav1 and Cav2 change depending on the bias voltage. When the capacitance components of the variable capacitance diodes Cav1 and Cav2 change, the resonance frequency by the circuit including the oscillator 113 changes, and the oscillation frequency changes.

  A voltage corresponding to the compensation signal output from the compensation circuit 122 is applied to the variable capacitance diodes Cav1 and Cav2 via the resistors R11 and R12. The capacitances of the variable capacitance diodes Cav1 and Cav2 change according to the compensation signal. Thereby, the oscillation output of the oscillation unit 121 is controlled to a desired frequency.

  The resistor R13 constitutes a feedback resistor. The resistor R14 is a resistor for controlling the gain. Furthermore, the capacitors C11 and C12 prevent the DC voltage for bias of the variable capacitance diodes Cav1 and Cav2 from flowing into the inverter 131.

[Temperature compensation circuit 122]
The temperature compensation circuit 122 outputs a compensation signal whose level changes according to the temperature. The compensation signal output from the temperature compensation circuit 122 is supplied to one end of the resistor R1. The other end of the resistor R1 is connected to the terminal T4 and the oscillation unit 121.

[Charging circuit 123]
The charging circuit 123 includes a comparator 141, an inverter 142, and transistors M11 and M12.

  The non-inverting input terminal of the comparator 141 is connected to the terminal T4, and the charging voltage of the capacitor C2 is supplied. An inverting input terminal of the comparator 141 is connected to a connection point between the temperature compensation circuit 122 and the resistor R1, and a compensation signal output from the temperature compensation circuit 122 is supplied.

  The comparator 141 sets the output to a high level if the charging voltage of the capacitor C2 is smaller than the compensation signal, and sets the output to a low level if the charging voltage of the capacitor C2 is greater than the compensation signal. The output of the comparator 141 is supplied to the inverter 142 and the terminal T13 of the timing control circuit 124. The inverter 142 inverts the output of the comparator 141.

  The output of the inverter 142 is supplied to the gate of the transistor M12. The transistor M12 is composed of a p-channel MOS transistor, and the source and drain are connected between the terminal T1 and the terminal T4. The transistor M12 is turned on when the output of the inverter 142 is at a low level, and supplies a current from the terminal T1 to the terminal T4 to charge the capacitor C2. The transistor M11 has a source-drain connected between the output of the comparator 141 and the ground, and a gate connected to the terminal T12 of the timing control circuit 124.

[Switch circuit 124]
The switch circuit 124 forms a so-called CMOS switch circuit called a transfer gate by the n-channel MOS transistor M21 and the p-channel MOS transistor M22, and shorts both ends of the resistor R1 when turned on. The gate of the n-channel MOS transistor M21 is connected to the terminal T14 of the timing control circuit 125, and the gate of the p-channel MOS transistor M22 is connected to the terminal T15 of the timing control circuit 125.

[Timing control circuit 125]
FIG. 2 shows a block configuration diagram of the timing control circuit 125.

  The timing control circuit 125 includes a reference power supply circuit 151, inverters 152 to 155, delay circuits 156 and 157, and NOR circuits 158 and 159.

  The reference power supply circuit 151 is connected between the terminal T11 and the ground. The terminal T11 is connected to the terminal T1, and the DC voltage Vcc is supplied from the power source 112. The reference power supply circuit 151 generates a reference voltage from the DC voltage Vcc. The reference voltage generated by the reference power supply circuit 151 is supplied to the inverter 152 as a high level signal.

  The inverter 152 inverts the high level signal supplied from the reference power supply circuit 151 and outputs a low level signal. In the state where the DC voltage Vcc is not supplied to the terminal T1, the output of the reference power supply circuit 151 is at a low level, and the output of the inverter 152 is at a high level. The output of the inverter 152 is supplied to the delay circuit 156.

  The delay circuit 156 includes a current source 161, a transistor M31, and a capacitor C11. The current source 161 is connected to the terminal T11 and generates a constant current from the DC voltage Vcc. The transistor M31 is composed of an n-channel MOS transistor, the source and drain are connected between the current source 161 and the ground, and the output of the inverter 152 is supplied to the gate. The capacitor C11 is connected in parallel between the source and drain of the transistor M31.

  In the delay circuit 156, when the output of the inverter 152 is at a high level, the transistor M31 is turned on to discharge the capacitor C11. When the DC voltage Vcc is applied to the terminal T1 and the output of the inverter 152 becomes low level, the transistor M31 is turned off and charging of the capacitor C11 is started.

  The charging voltage of the capacitor C11 is supplied to the inverter 153. The inverter 153 outputs a high level when the charging voltage of the capacitor C11 is below a predetermined level, and sets the output low when the charging voltage of the capacitor C11 exceeds a predetermined level.

  The output of the inverter 153 is supplied to the terminal T12 and the NOR circuit 158. The NOR circuit 158 outputs a NOR logic between the output of the inverter 153 and the input of the terminal T13. The output of the NOR circuit 158 is supplied to the inverter 154. The inverter 154 inverts the output of the NOR circuit 158 and outputs it. The output of the inverter 154 is supplied to the delay circuit 157 and the NOR circuit 159.

  Delay circuit 157 has the same configuration as delay circuit 156, and delays the output of inverter 154 for output. The output of the delay circuit 157 is supplied to the NOR circuit 159. The NOR circuit 159 outputs a NOR logic between the output of the inverter 154 and the output of the delay circuit 157.

  The output of the NOR circuit 159 is supplied to the terminal T14 and the inverter 155. The inverter 155 inverts the output of the NOR circuit 159 and supplies it to the terminal T15.

[Operation]
FIG. 3 shows an operation waveform diagram of the timing control circuit 125. 3A shows terminals T1 and T11, FIG. 3B shows the output of the reference power supply circuit 151, FIG. 3C shows the output of the inverter 152, FIG. 3D shows the output of the delay circuit 156, and FIG. E) is the output of the inverter 153, FIG. 3F is the terminal T13, FIG. 3G is the output of the NOR circuit 158, FIG. 3H is the output of the inverter 154, and FIG. FIG. 3J shows the output waveform of the NOR circuit 159.

  At time t1, when the power supply voltage Vcc is applied from the power supply 112 as shown in FIG. 3A, the output of the reference power supply circuit 151 gradually rises as shown in FIG. 3B. At this time, the output of the inverter 152 becomes a high level as shown in FIG.

  At this time, since the transistor M31 is turned on, the output of the delay circuit 156 becomes a low level as shown in FIG. Since the output of the delay circuit 156 is at a low level, the output of the inverter 153 is at a high level as shown in FIG. At this time, the output of the inverter 153 is supplied to the gate of the transistor M11 via the terminal T12. Since the transistor M11 is composed of an n-channel MOS transistor, the transistor M11 is turned on when the terminal T12 becomes high level.

  When the transistor M11 is turned on, the input of the inverter 142 becomes low level, and the output of the inverter 142 becomes high level. When the output of the inverter 142 becomes high level, the transistor M12 is turned off. Thereby, charging of the capacitor C2 is suppressed. At this time, since the compensation signal is supplied from the temperature compensation circuit 122 to the non-inverting input terminal of the comparator 141 and the inverting input terminal is at the ground level, its output is at the high level.

  Further, when the transistor M11 is turned on, the terminal T13 is set to the low level. When the terminal T13 is set to the low level, both inputs of the NOR circuit 158 are set to the low level, so that the output is set to the high level. As a result, the output of the inverter 154 becomes a high level as shown in FIG. When the output of the inverter 154 becomes high level, the transistor M31 of the delay circuit 157 is turned on, so that the output of the delay circuit 157 is low level as shown in FIG. Since the NOR circuit 159 has one input at a high level and the other input at a low level, its output is set to a low level as shown in FIG. When the output of the NOR circuit 159 is at a low level, the terminal T14 is at a low level and the terminal T15 is at a high level, so that the switch circuit 124 is turned off.

  When the output of the reference power supply circuit 151 reaches a predetermined voltage V1 as shown in FIG. 3A at time t2, the output of the inverter 153 becomes low level as shown in FIG. 3C. When the output of the inverter 153 becomes low level, the transistor M31 of the delay circuit 156 is turned off, and charging of the capacitor C11 is started. At this time, the switch circuit 124 is maintained in the off state, and the capacitor C2 is efficiently charged.

  When the charging voltage of the capacitor C11 reaches V2 at time t3 as shown in FIG. 3D, the output of the inverter 153 is inverted to low level. When the output of the inverter 153 is inverted to a low level, the transistor M11 of the charging circuit 123 is turned off.

  When the transistor M11 is turned off, the charging circuit 123 supplies the output of the comparator 141 to the inverter 142. At this time, since the output of the comparator 141 is at a high level, the output of the inverter 142 is at a low level, the transistor M12 is turned on, and the capacitor C2 is charged approximately by the power supply voltage Vcc. At this time, the transistor M11 is turned off, so that the terminal T13 becomes high level as shown in FIG.

  When the charging voltage of the capacitor C2 reaches the compensation signal level of the temperature compensation circuit 122 at time t4, the output of the comparator 123 is inverted to a low level. When the output of the comparator 123 is inverted to a low level, the transistor M12 is turned off, and charging of the capacitor C2 is stopped.

  When the output of the comparator 123 is inverted to a low level, the terminal T13 is inverted to a low level. When the terminal t13 is inverted to the low level, both inputs of the NOR circuit 158 become the low level, so that the output is inverted to the high level as shown in FIG. When the output of the NOR circuit 158 becomes high level, the output of the NOR circuit 159 is inverted to high level as shown in FIG. When the output of the NOR circuit 159 is inverted to a high level, the terminal T14 becomes a high level and the terminal T15 becomes a low level, so that the switch circuit 124 is turned on. When the switch circuit 124 is turned on, the temperature compensation circuit 122 and the capacitor C2 are directly connected. As a result, the charging voltage of the capacitor C2 is rapidly adjusted to match the compensation signal level of the temperature compensation circuit 122. Thereby, the capacitance of the oscillating unit 121 is rapidly adjusted to a frequency corresponding to the output compensation signal of the temperature compensation circuit 122, and the oscillation frequency can be stabilized at high speed.

  At time t5, when the charging voltage of the capacitor C11 of the delay circuit 157 reaches V3 as shown in FIG. 3 (I), the output of the NOR circuit 159 is inverted to a low level as shown in FIG. 3 (J).

  When the output of the NOR circuit 159 becomes low level, the switch circuit 124 is turned off. When the switch circuit 124 is turned off, an integration circuit is configured by the resistor R1 and the capacitor C2, and the output compensation signal of the temperature compensation circuit 122 can be stably supplied to the oscillation unit 121.

  FIG. 4 shows a simulation waveform diagram of one embodiment of the present invention. 4A is a diagram illustrating a charging voltage of the capacitor C2, and FIG. 4B is a diagram illustrating a charging period of the capacitor C2 and a short circuit period of the resistor R1.

  According to the present embodiment, as shown in FIG. 4B, the capacitor C2 is charged in the period T1, and then the resistor R1 is short-circuited in the period T2 to thereby charge the capacitor C2 as shown in FIG. It can be seen that after the resistor R1 is short-circuited, the compensation signal level VTC is rapidly reached. As a result, the oscillator 121 can be compensated at high speed by the compensation signal VTC.

〔effect〕
According to the present embodiment, when the power supply voltage Vcc is turned on, the capacitor C2 constituting the integration circuit for stabilizing the temperature compensation signal by the charging circuit 123 can be charged to the temperature compensation signal at high speed. Further, after the charging of the capacitor C2 is completed, both ends of the resistor R1 constituting the integrating circuit are short-circuited, and the temperature compensation circuit 122 and the capacitor C2 are directly connected to each other. The shift generated between the capacitor C2 and the temperature compensation signal can be adjusted at high speed by the offset of the charging circuit 123 or the like. Thereby, the charging voltage of the capacitor C2 can be matched with the temperature compensation signal at high speed. This makes it possible to stabilize the oscillation frequency of the oscillating unit 121 at a high speed at the time of starting the power supply voltage Vcc.

[Application example]
The oscillation circuit 100 of the present embodiment is suitable for being mounted on a battery-driven device or the like. In a battery-powered device, when the power of the oscillation circuit 100 is intermittently supplied to wait for power saving or the like to provide intermittent oscillation output, the oscillation frequency of the oscillation circuit 100 is set to a desired oscillation frequency at high speed. It becomes possible to stabilize. Therefore, it is possible to perform processing quickly and to further save power.

[Others]
In the present embodiment, the configuration of the oscillation unit 121 is configured using the oscillator 113 and the inverter 131. However, the configuration of the oscillation unit 121 is not limited to this, and the main point is a voltage-controlled oscillation circuit. The configuration is not limited to this.

  In this embodiment, the case where the oscillation is stabilized by the temperature compensation signal has been described as an example. However, the present invention is not limited to the case where the temperature compensation signal is stabilized at a high speed.

It is a block block diagram of one Example of this invention. 2 is a block configuration diagram of a timing control circuit 125. FIG. 7 is an operation waveform diagram of the timing control circuit 125. FIG. It is a simulation waveform figure of one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Oscillator circuit 111 Oscillator IC, 112 Power supply, 113 Oscillator 121 Oscillator, 122 Temperature compensation circuit, 123 Charging circuit, 124 Switch circuit 125 Timing control circuit

Claims (2)

An oscillation circuit having a compensation circuit that generates a compensation signal, and an oscillation unit that can control an oscillation frequency in accordance with the compensation signal from the compensation circuit,
An integration circuit including a resistor and a capacitor, and supplying an integrated waveform of the compensation signal to the oscillation unit;
A comparison circuit for comparing voltages across the resistor;
Begins charging the pre-crisis Yapashita when the power supply voltage is applied, the comparison result of the comparison by the circuit, a charging circuit for stopping charging of the capacitor when the voltage across the resistor matches,
A switch circuit for short-circuiting both ends of the resistor included in the integrating circuit;
An oscillation circuit comprising: a control circuit for short-circuiting a resistor included in the integration circuit for a predetermined time by the switch circuit after charging of the capacitor by the charging circuit is stopped .   The control circuit controls the charging circuit and the switch circuit so that a charging period of the capacitor by the charging circuit and a short circuit period of the resistor by the switch circuit do not overlap each other. Oscillation circuit.

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