JP2005079875A - Oscillation circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oscillation circuit which includes an oscillator performing oscillation by applying a voltage, capacitive element that constitute a resonance circuit with the oscillator and decide oscillation frequencies, and amplification circuits amplifying oscillation outputs generated by the oscillator and the capacitive element; and which can be started at high speed. <P>SOLUTION: The oscillation circuit includes the oscillator (X1) performing oscillation by applying a voltage, the capacitive element (C1 and C2) which constitute the resonance circuit with the oscillator (X1) and decide the oscillation frequencies and the amplification circuits (Q1, Q2, R1 to R4 and C3) amplifying oscillation outputs generated by the oscillator (X1) and the capacitive element (C1 and C2). The circuit has starting circuits (111 and 112) supplying starting currents to input ends to which oscillation outputs generated by the oscillator (X1) and the capacitive element (C1 and C2) of the amplification circuits (Q1, Q2, R1 to R4 and C3) are inputted, when a power voltage (Vcc) driving the oscillator (X1) and the amplification circuits (Q1, Q2, R1 to R4 and C3) is supplied at the time of supplying power. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an oscillation circuit, and in particular, includes an oscillator that oscillates by applying a voltage, a resonance circuit that forms a resonance circuit together with the oscillator, and a resonator and a capacitance element that determine an oscillation frequency. The present invention relates to an oscillation circuit including an amplification circuit that amplifies generated oscillation output.

  In recent years, with the increase in battery-driven devices such as mobile phones, low power consumption is desired for integrated circuits mounted on devices. At this time, an oscillation circuit among the circuits on which the device is mounted is caused to intermittently oscillate to reduce power consumption. For this reason, it is desired for the oscillation circuit to shorten the time from the activation to the steady state.

  FIG. 5 shows a circuit configuration diagram of a conventional example.

  The conventional oscillation circuit 1 includes an oscillator X1, capacitors C1 to C3, transistors Q1 and Q2, and resistors R1 to R4, and constitutes a so-called Colpitts type oscillation circuit. The oscillator X1 is composed of a crystal resonator, for example. Capacitors C1 and C2 that form a resonance circuit together with the oscillator X1 are connected in parallel to the oscillator X1.

  The oscillation output oscillated by the oscillator X1 and the capacitors C1 and C2 is supplied to an amplifier circuit including transistors Q1 and Q2, resistors R1 to R4, and a capacitor C3.

  The amplifier circuit composed of transistors Q1 and Q2, resistors R1 to R4, and capacitor C3 has a configuration in which two-stage amplifiers, an amplifier composed of transistor Q1 and an amplifier composed of transistor Q2, are connected in series. The oscillation output oscillated by the oscillator X1 and the capacitors C1 and C2 is amplified and output from the collector of the transistor Q1. The oscillation output amplified by the amplifier circuit composed of the transistors Q1 and Q2, resistors R1 to R4, and the capacitor C3 is supplied to the load 11 including the capacitance C0 and the resistor R0 via the coupling capacitor Cc.

  6 and 7 are diagrams for explaining the operation of a conventional example. FIG. 6 shows the waveform of each part immediately after the rising of the power supply voltage Vcc, and FIG. 7 shows the waveform of the oscillation output. In FIG. 6, the thin broken line is the waveform of the power supply voltage Vcc, the solid line is the base voltage waveform of the transistor Q1, the thick broken line is the base voltage waveform of the transistor Q2, the one-dot chain line is the collector voltage waveform of the transistor Q1, and the two-dot chain line is the emitter of the transistor Q2. A voltage waveform is shown.

  In the conventional oscillation circuit 1, when the power supply voltage Vcc rises at time t0 as shown in FIG. 6, the base potential of the transistor Q2 gradually increases during time T0 and reaches a steady state at time t1. Thereafter, the circuit gradually rises, and the oscillation output reaches about 90% of the steady state at time T10, which is about 7.4 msec from time t0, as shown in FIG. For example, the oscillation output can be used at time t10 when it reaches approximately 90% of the steady state. At this time, when the oscillation circuit is intermittently oscillated with a mobile phone or the like, a startup time of about 4.0 msec is desired, and the conventional oscillation circuit 1 cannot satisfy this requirement.

  In addition, although the publicly known literature was investigated about the technique which speeds up starting of an oscillation circuit, the publicly known literature corresponding to this was not discovered.

  However, the conventional oscillation circuit has a problem that the start-up time is as long as 7.4 msec, and a start-up time of about 4.0 msec cannot be obtained.

  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 started at high speed.

In the present invention, an oscillator (X1) that oscillates by applying a voltage, a resonance circuit together with the oscillator (X1), a capacitive element (C1, C2) for determining an oscillation frequency, an oscillator ( X1) and an oscillation circuit including an amplification circuit (Q1, Q2, R1 to R5, C3) for amplifying an oscillation output generated by the capacitive elements (C1, C2),
When power supply voltage (Vcc) for driving the oscillator (X1) and the amplifier circuits (Q1, Q2, R1 to R5, C3) is turned on when the power is turned on, the amplifier circuits (Q1, Q2, R1 to R5, C3) It has a starting circuit (111, 112) for supplying a starting current to an input terminal to which an oscillation output generated by the oscillator (X1) and the capacitive elements (C1, C2) is input.

  The starter circuit (111, 112) of the present invention includes a current generator circuit (111) that generates a starter current from the power supply voltage (Vcc) when the power is turned on, and a current generator when the power supply voltage (Vcc) is lower than a predetermined voltage. When the starting current generated by the circuit (111) is supplied to the input terminal of the amplifier circuit (Q1, Q2, R1 to R4, C3) and the power supply voltage (Vcc) becomes a predetermined voltage, the current generating circuit (111 And a switch circuit (112) for stopping supply to the input terminal of the amplifying circuit (Q1, Q2, R1 to R5, C3) of the starting current generated in (1).

  Furthermore, the present invention is characterized in that the oscillator (X1), the capacitive elements (C1, C2), and the amplifier circuits (Q1, Q2, R1 to R5, C3) constitute a Colpitts oscillation circuit.

  Further, the amplifier circuit (Q1, Q2, R1 to R5, C3) of the present invention is constituted by a plurality of cascode-connected amplifiers.

  Further, the starting circuit (111, 112) supplies a starting current to the input terminal of the first stage amplifier (Q2, R2, R4) among the plurality of cascode-connected amplifiers.

  The above reference numerals are only for reference, and the present invention is not limited thereby.

  According to the present invention, when the power supply voltage (Vcc) for driving the oscillator (X1) and the amplifier circuits (Q1, Q2, R1 to R5, C3) is turned on by the starting circuit (111, 112) when the power is turned on. In addition, by supplying a starting current to the input terminal to which the oscillation output generated by the oscillator (X1) and the capacitive element (C1, C2) of the amplifier circuit (Q1, Q2, R1 to R5, C3) is input, Since the amplifier circuits (Q1, Q2, R1 to R5, C3) can be started at high speed, the oscillation output can reach a desired level at high speed.

[First embodiment]
FIG. 1 shows a circuit configuration diagram of a first embodiment of an oscillation circuit according to the present invention. In the figure, the same components as those in FIG.

  The oscillation circuit 100 of the present embodiment is configured by providing a current generation circuit 111 and a switch circuit 112 in the conventional oscillation circuit 1 shown in FIG.

  The current generation circuit 111 is composed of PNP transistors Q11 and Q12 and resistors R11 to R13, and constitutes a constant current circuit. The current generation circuit 111 is connected between the power supply terminal Tvcc and the ground, and is applied with the power supply voltage Vcc applied to the power supply terminal Tvcc. To generate a starting current. The starting current generated by the current generation circuit 111 is supplied to the switch circuit 112.

  The switch circuit 112 is composed of a PNP transistor Q21. A starting current is supplied from the current generation circuit 111 to the emitter of the transistor Q21. The base of the transistor Q2 constituting the amplifier circuit is connected to the collector of the transistor Q21, and the connection point of the resistors R1 and R5 constituting the bias circuit of the amplifier circuit is connected to the base.

  The switch circuit 112 is turned on when the potential at the connection point between the resistor R1 and the resistor R5 is smaller than a predetermined potential, and supplies the starting current generated by the current generation circuit 111 to the base of the transistor Q2, which is larger than the predetermined potential. Then, it is turned off, and the supply of the starting current generated by the current generation circuit 111 to the base of the transistor Q2 is cut off. That is, the switch circuit 112 supplies the starting current generated by the current generation circuit 111 to the base of the transistor Q2 when the power supply voltage Vcc rises.

  2 and 3 are diagrams for explaining the operation of the first embodiment of the oscillation circuit of the present invention. 2 shows the waveforms of the respective parts immediately after the rising of the power supply voltage Vcc, and FIG. 3 shows the waveform of the oscillation output. In FIG. 2, the thin broken line is the waveform of the power supply voltage Vcc, the solid line is the base voltage waveform of the transistor Q1, the thick broken line is the base voltage waveform of the transistor Q2, the one-dot chain line is the collector voltage waveform of the transistor Q1, and the two-dot chain line is the transistor Q2. The emitter voltage waveform of is shown.

  In the oscillation circuit 100 of the present embodiment, when the power supply voltage Vcc rises at time t0, the current generation circuit 111 generates a starting current accordingly. At this time, since the potential at the connection point between the resistor R1 and the resistor R5 is delayed by the capacitors C1 and C2 at the beginning of the rise of the power supply voltage Vcc, the base potential of the transistor Q21 constituting the switch circuit 112 becomes low level. The switch circuit 112 is turned on.

  Therefore, the starting current generated by the current generation circuit 111 is supplied to the base of the transistor Q2. Due to the starting current from the current generation circuit 111, the base potential of the transistor Q2 rises steeply as shown by a thick broken line in FIG.

  As a result, a voltage is suddenly applied to the oscillator X1. Further, charging of the capacitors C1 and C2 is accelerated by the starting current. That is, in this embodiment, the oscillation circuit 100 can be shocked by a pulse voltage having a large harmonic component when the power supply voltage Vcc rises. When the oscillation circuit 100 is shocked by the pulse voltage, the rise of the oscillation output can be accelerated later.

  When the power supply voltage Vcc rises to a predetermined voltage at time t21 when time T20 has elapsed from time t0, the potential at the connection point between the resistors R1 and R5 becomes the off potential of the transistor Q21. When the potential at the connection point between the resistor R1 and the resistor R5 becomes the off-potential of the transistor Q21, the transistor Q21 constituting the switch circuit 112 is turned off, and the starting current generated by the current generation circuit 111 is applied to the base of the transistor Q2. Supply is stopped.

  When the supply of the starting current to the base of the transistor Q2 is stopped, the base potential of the transistor Q2 is slightly lowered once, but the power supply voltage Vcc has already risen. Reaches a substantially steady state potential at time t22 at which time T21 has elapsed.

  As described above, according to the present embodiment, the oscillation circuit 100 causes the base potential of the transistor Q2 and the applied voltage of the oscillator X1 to rise steeply (in the form of a pulse) as the power supply voltage Vcc rises at startup. It is potentially activated at a high speed in several μsec. Thus, since the oscillation circuit 100 rises at a high speed when the power supply voltage Vcc rises, as shown in FIG. 7, the time T30 from time t0 to time t30 when the oscillation output becomes about 90% of the steady state. Can be shortened to approximately 4.0 msec. Therefore, it is possible to satisfy the requirement of 4.0 msec for the start-up time required for intermittent oscillation in a mobile phone or the like.

  In this embodiment, the switch circuit 112 is turned off when the power supply voltage Vcc reaches a substantially steady state potential, and the supply of the starting current is stopped, so that power consumption in the steady state can be reduced. Therefore, the startup time can be increased while realizing low power consumption.

[Second Embodiment]
FIG. 4 is a circuit diagram showing a second embodiment of the oscillation circuit according to the present invention. In the figure, the same components as in FIG.

  The oscillation circuit 200 of the present embodiment is different from the oscillation circuit 100 of the first embodiment in the configuration of the switch circuit 212.

  The switch circuit 212 of this embodiment is composed of a PNP transistor Q31 having a multi-collector structure, with one collector connected to the base of the transistor Q2 and the other collector connected to the base of the transistor Q1. .

  According to this embodiment, the transistor Q31 constituting the switch circuit 212 is constituted by a multi-collector transistor, and in addition to the transistor Q2 constituting the first stage amplifier of the amplifier circuit, the base of the transistor Q1 constituting the next stage amplifier. By raising the potential with the starting current generated by the current generation circuit 111, the transistor Q1 can be started up in the same manner as the transistor Q2, so that further increase in the starting time can be expected.

  Note that the oscillator X1 is not limited to a crystal resonator, but may be other vibrations such as a ceramic resonator.

  Further, although the amplifier circuit of the present embodiment has a configuration in which amplifiers are connected in two stages in the column, the amplifier circuit may be one stage. Further, a configuration in which a plurality of amplifiers are connected in cascade in a plurality of stages may be employed. At this time, it is possible to easily supply the starting current to the base potentials of the amplifiers in a plurality of stages simply by configuring the switch circuit with a transistor having a multi-collector structure.

1 is a circuit configuration diagram of a first embodiment of an oscillation circuit according to the present invention. It is an operation | movement waveform diagram of 1st Example of the oscillation circuit of this invention. It is an operation | movement waveform diagram of 1st Example of the oscillation circuit of this invention. It is a circuit block diagram of 2nd Example of the oscillation circuit of this invention. It is a circuit block diagram of an example of the conventional oscillation circuit. It is an operation | movement waveform diagram of an example of the conventional oscillation circuit. It is an operation | movement waveform diagram of an example of the conventional oscillation circuit.

Explanation of symbols

100, 200 Oscillator circuit 111 Current supply circuit, 112, 212 Switch circuit X1 Oscillator, C1-C3, Cc, C0 capacitors R1-R5, R11-R13, R0 resistors Q1, Q2, Q11, Q12, Q21 transistors

Claims (5)

An oscillator that oscillates by applying a voltage, a resonance circuit together with the oscillator, a capacitance element for determining an oscillation frequency, and an oscillation output generated by the oscillator and the capacitance element are amplified In an oscillation circuit including an amplifier circuit,
When a power supply voltage for driving the oscillator and the amplifier circuit is turned on when the power is turned on, a starting current is supplied to an input terminal to which an oscillation output generated by the oscillator and the capacitive element of the amplifier circuit is input An oscillation circuit comprising a starting circuit that The startup circuit includes a current generation circuit that generates a startup current by a power supply voltage when the power is turned on, and
When the power supply voltage is equal to or lower than a predetermined voltage, the starting current generated by the current generation circuit is supplied to the input terminal of the amplifier circuit, and when the power supply voltage becomes a predetermined voltage, the current generation circuit generates The oscillation circuit according to claim 1, further comprising: a switch circuit that stops supply of the startup current to the input terminal of the amplifier circuit.   3. The oscillation circuit according to claim 1, wherein the oscillator, the capacitive element, and the amplifier circuit constitute a Colpitts oscillation circuit.   4. The oscillation circuit according to claim 1, wherein the amplification circuit includes a plurality of cascode-connected amplifiers. 5.   5. The oscillation circuit according to claim 4, wherein the starting circuit supplies the starting current to an input terminal of a first-stage amplifier among a plurality of cascode-connected amplifiers.

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