JPH0368203A - Voltage controlled oscillating circuit using piezoelectric oscillator - Google Patents

Abstract

PURPOSE:To vary the oscillation frequency over a wide range by providing a variable capacitance part on each of the input side and the output side of a piezoelectric oscillator. CONSTITUTION:Capacitance of variable capacitance parts 3 and 4 at the input side and the output side of a piezoelectric oscillator 1 are changed by an applied voltage, and the oscillator 1 oscillates at a prescribed frequency. The oscillation output is amplified by an amplifier part 2 connected in parallel to the oscillator 1, and the variable part 3 changes the voltage applied to the oscillator 1. The variable part 4 changes the voltage applied to the oscillator 1 together with the variable part 3 to change the oscillation frequency. Since the oscillation frequency of the piezoelectric oscillator is varied by variable capacitance parts 3 and 4, a fixed capacitor is not included in the overall capacitance which sets the frequency of the piezoelectric oscillator, and the capacity is varied over a wide range without an influence of the fixed capacitor to change the applied voltage, and the oscillation frequency is changed over a wide range.

Description

[Detailed Description of the Invention] [Summary] The purpose of the present invention is to provide a voltage υ controlled oscillation circuit with a wide frequency variable range, regarding a voltage controlled oscillator circuit using a piezoelectric vibrator used in equipment etc. that requires a wide frequency variable range. a piezoelectric vibrator that oscillates at a predetermined frequency by changing the capacitance value of a variable capacitance section depending on an applied voltage; and an amplifier section that is connected in parallel with the piezoelectric vibrator and feeds back and amplifies the oscillation output of the piezoelectric vibrator. a first capacitance variable section that is connected to the input stage side of the amplifier section of the piezoelectric vibrator and that changes the oscillation frequency by varying the voltage applied to the piezoelectric vibrator; and the amplifier of the piezoelectric vibrator. and a second variable capacitance section that is connected to the output stage side of the piezoelectric vibrator and changes the oscillation frequency by varying the voltage applied to the piezoelectric vibrator together with the first variable capacitance section.

[Industrial application field]

The present invention relates to a voltage-controlled oscillator circuit using a transducer, and more particularly to a voltage control circuit using a transducer for use in equipment that requires a wide frequency range.

In recent years, voltage υ1' @ oscillators (hereinafter abbreviated as rVcOJ) have been widely used for PLL circuits and motor control, and depending on the equipment used, vC with a wide variable frequency range
O is required.

[Prior Art] Conventionally, as a frequency oscillation circuit, an oscillation circuit using a gate as shown in FIG. 4 is common. In Figure 4,
An inverter circuit (0M
O8>12 and a resistor Rn are connected in parallel, and both ends thereof are grounded via a capacitor Cn and CI2. The inverter circuit 12 feeds back and amplifies the oscillation of the piezoelectric vibrator 11.

However, the oscillation frequency of the piezoelectric vibrator 11 is
2 and CI2, and is fixed.

Therefore, as a method of varying the output oscillation frequency,
There is CO as shown in FIG. In FIG. 5, a capacitor CI3 is interposed on the input side of the inverter circuit 11 between the connection between the inverter circuit 12 and the piezoelectric vibrator 11 in FIG. 4, and a resistor R12 is interposed on the output side. Also,
The capacitor Cn in FIG. 4 is replaced with a variable capacitance diode Do, and a resistor Ru is interposed at its input stage. In this case, the capacitance of the capacitor CI3 is set to several thousand pF to cut the DC component, while the resistor R12 adjusts the gain of the inverter circuit 12. Further, the variable visitor diode D++ changes its capacitance and is synonymous with a variable capacitor. And tlHi! LR+
3 is for applying a voltage to the variable capacitance diode Da. Therefore, by changing the capacitance of the variable capacitance diode D11, the oscillation frequency is changed.

[Problem to be solved by the invention]

By the way, the capacitors CI2 and CI2 in FIG. 4 are connected in series from the viewpoint of the piezoelectric vibrator 11. Therefore, as shown in FIG.
When a variable capacitance diode D u is used instead, the combined capacitance cannot be changed by the change in the variable capacitance diode Dn due to the influence of the fixed capacitor CI2.

For example, the capacitor CI2 is 10 [11F], and the capacitance of the variable capacitance diode D n is 10 [pF] to 100
[pF], the combined capacitance is 5 [pF] to 55 [p
"] has a variable width.

Therefore, in digital audio equipment and the like, there is a problem that the lock range (for example, the input error or variable width of the VCO of the PL1 circuit) cannot be followed by the variable width of the VCO oscillation circuit such as the Listal.

Therefore, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a voltage-controlled oscillation circuit using a piezoelectric vibrator having a wide variable frequency range.

(Means for solving problems) FIG. 1 shows a block diagram of the principle of the present invention.

In FIG. 1, numeral 1 denotes a piezoelectric vibrator, which changes the capacitance value of the capacitance variable section 3.4 depending on the applied voltage and oscillates at a predetermined frequency. Reference numeral 2 denotes an amplifier section, which is connected in parallel with the piezoelectric vibrator 1. This amplifier section 2 feeds back and amplifies the oscillation output of the piezoelectric vibrator 1.

Reference numeral 3 denotes a first variable capacitance section, which is connected to the input stage side of the amplifier section 2 of the piezoelectric vibrator 1. This first capacitance variable section 3 varies the voltage applied to the piezoelectric vibrator 1 to change the oscillation frequency. 4 is a second variable capacitance section, and piezoelectric vibrator 1
is connected to the output stage side of the amplifier section 2. This second variable capacitance section 4 is connected to the piezoelectric vibrator 1 together with the first variable capacitance rA3.
The oscillation frequency is changed by varying the voltage applied to the oscillation frequency.

(Function) As shown in FIG. 1, in the present invention, the oscillation by the piezoelectric vibrator 1 is varied by the first variable capacitance section 3 and the second variable capacitance section 4. That is, since a fixed capacitance element is not included in the total capacitance that sets the frequency of the piezoelectric vibrator 1, the capacitance can be varied over a wide range without being affected by the fixed capacitance. As a result, the voltage applied to the variable capacitance section is changed, and the oscillation frequency is varied over a wide range. Further, the second variable capacitance section 4 is controlled by the same input voltage as the first variable capacitance section 3.

Therefore, a wide frequency variable range can be easily obtained, and it is possible to follow the lock range of digital audio equipment and the like.

〔Example〕

FIG. 2 is a principle circuit diagram showing an embodiment of the present invention.

In FIG. 2(A), the amplifier section 2 and inverter circuit 5 in FIG. 1 are replaced, and the first capacitance variable section 3 is replaced with
is replaced with a variable capacitance diode D1, and the second variable capacitance section 4 is replaced with a variable capacitance diode D2. That is, the input stage side of the inverter circuit 5 of the piezoelectric vibrator 1 is grounded (anode grounded) via the variable capacitance diode D1, and the output stage side is grounded (anode grounded) via the variable capacitance diode D2. The combined capacitance of these variable capacitance diodes D1 and D2 has a wider variable range than when the capacitance is fixed.
The voltage applied to the piezoelectric vibrator 1 also varies over a wide range, widening the variable range of the oscillation frequency of the circuit.

Further, in FIG. 2(B), a variable capacitance diode D3 is further interposed between the connection point between the inverter circuit 5 and the variable capacitance diode D1 and the piezoelectric vibrator 1 (the piezoelectric vibrator 1 side is the anode), and the inverter circuit A variable capacitance diode D4 is interposed between the connection point between the piezoelectric vibrator 1 and the variable capacitance diode D2 (7 nodes on the piezoelectric vibrator 1 side). Then, since the variable capacitance diodes D1 to D4 are changed, the variable range of the combined capacitance becomes wider, and the variable range of the oscillation frequency of the circuit becomes wider.

Next, FIG. 3 shows a circuit diagram of an embodiment of the principle circuit diagram of FIG. 2(B). In FIG. 3, a piezoelectric element such as crystal, lithium tantalate, lithium niobate, etc. is used for the piezoelectric vibrator 1.

The amplifier section 2 includes a wI ring resistor R in the inverter circuit section 5.
1 are connected in parallel, and a capacitor C2 (several thousand [
t) F]) is connected, and a gain adjustment resistor R2 is connected to the output stage side. And the oscillation output is the output electron 6
taken from.

The first variable capacity section 3 is connected to the piezoelectric vibrator 1 from the input terminal 7 via the resistor R3 and the variable capacitance diode 02.
connected to. The aforementioned capacitor C3 is connected to the connection point between the resistor R3 and the variable capacitance diode D3, and
Grounding via variable capacitance diode D1 (anode grounding)
be done.

Further, the second capacitance variable section 4 connects the piezoelectric vibrator 1 to a resistor R2.
From the connection point, capacitor C2, variable capacitance diode 0
41 is connected to input terminal 7 via resistor R5. The connection point between capacitor C2 and variable capacitance diode D4 is resistor R6.
grounded via.

Further, the connection point between the variable capacitance diode D4 and the resistor R5 is grounded (anode grounded) via the variable capacitance diode Dz.

In the above oscillation circuit, capacitor C2 is several thousand [Dr]
is set to cut the DC component. Resistor R3 is for applying input voltage to variable capacitance diode D1.
Similarly, resistor R4 connects variable capacitance diode D3 to resistor R4.
s is for applying a voltage to the variable capacitance diode 02, and the resistor R6 is for applying a voltage to the variable diode D4.

The combined capacitance is changed by changing the variable capacitance diodes D1 to D4, thereby changing the voltage applied to the variable capacitance diodes connected to the piezoelectric vibrator 1, thereby changing the oscillation frequency. That is, on the input stage side of the piezoelectric vibrator 1, the variable capacitance diodes D3 and Dl are in series when viewed from the piezoelectric vibrator 1, as shown in FIG. 2(A).
The capacitance can be changed over a wider range. On the other hand, on the output stage side, the variable capacitance diodes D4 and Dl similarly vary the tolerance in a wider range than in FIG. 2(A).

Therefore, the variable capacitance diode D1 is connected to the input stage side and the output stage side.
~The combined capacitance changes over a wider range throughout D4.

For example, if lithium tantalate is used for the piezoelectric vibrator 1, and the variable capacitance diodes D1 to D4 can be varied up to 100[p''], and the input voltage is changed from O to 5[v], 5[v] The frequency change rate when
．． It becomes 75%, which means that a variable width of about twice as much can be obtained. Note that the rate of frequency change varies depending on the type of piezoelectric Ti element 1 and the capacitance of the metal alloy.

On the other hand, by using a piezoelectric vibrator as in the present invention, the influence of noise and temperature can be reduced, and jitter can be eliminated, so errors can also be reduced in the PLL circuit.

In this way, since the variable range of the oscillation frequency can be widened, it is possible to follow the lock range of digital audio equipment, etc. Further, even if the number of variable capacitance diodes is increased, the circuit does not become complicated because there is only one control l voltage terminal.

Although the above embodiment shows the case where the inverter circuit 5 is used in the amplifier section 2, the same effect can be obtained even if a Colpitts type circuit using transistors is used.

(Effects of the Invention) As described above, according to the present invention, by providing variable capacitance sections on the input stage side and the output stage side of the piezoelectric vibrator,
The capacitance can be easily varied over a wide range, and thereby the oscillation frequency can be varied over a wide range, making it possible to use it in a wide range of devices.

[Brief explanation of drawings]

Fig. 1 is a principle block diagram of the present invention, Fig. 2 is a principle circuit diagram of an embodiment of the invention, Fig. 3 is a circuit diagram of an embodiment of the invention, Fig. 4 is a conventional oscillation circuit diagram, FIG. 5 is a circuit diagram of a conventional ■CO. In the figure, 1.11 is a piezoelectric vibration f, 2 is an amplifier section, 3 is a first capacitance variable section, 4u is a second capacitance variable section, 5.12 is an inverter circuit, and D1 to D4 are variable acceptance diodes. Tei Invention/) R Reason 92 Figure 1 (A) (8) Asu R Tsume r
Principle of yJ#JPl 1. Figure 2

Claims (1)

[Scope of Claims] A piezoelectric vibrator (1) that oscillates at a predetermined frequency by changing the capacitance value of a capacitance variable portion (3) depending on an applied voltage; The piezoelectric vibrator (
an amplifier section (2) that feeds back and amplifies the oscillation output of 1); and an amplifier section (2) that is connected to the input stage side of the amplifier section (2) of the piezoelectric vibrator (1) and applies an electric current to the piezoelectric vibrator (1). a first variable capacitance section (3) that changes the oscillation frequency by varying the voltage; and a first variable capacitance section that is connected to the output stage side of the amplifier section (2) of the piezoelectric vibrator (1). (3) and a second capacitance variable section (4) that changes the oscillation frequency by varying the voltage applied to the piezoelectric vibrator (1); and a voltage controlled oscillation circuit using a piezoelectric vibrator. .