JP2544999Y2 - Voltage controlled oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a voltage controlled oscillator (VCO), and more particularly to a voltage controlled oscillator configured using a voltage comparator.

(Prior Art) A conventional voltage controlled oscillator using a voltage comparator is configured as shown in FIG.

In the voltage controlled oscillator shown in FIG.
Resistor R ₃₁ to the input side of the variable capacitance diode (VCP) C ₃₁
There are connected, the voltage input to the input terminal IN, is intended for varying the oscillation frequency the capacitance of the variable capacitance diode C ₃₁ adjusted to.

(Problem devised to be Solved) above in the third voltage controlled oscillator as shown in FIG, since the resistor R ₃₁ and a variable capacitance diode C ₃₁ on the input side of the voltage comparator is inserted, the output terminal OUT at high speed However, there is a disadvantage that the frequency of the output signal cannot be varied.

Therefore, an object of the present invention is to provide a voltage controlled oscillator that enables the frequency of an output signal to quickly follow a change in the voltage of an input signal.

(Means for Solving the Problems) In order to solve the above-mentioned problems, a voltage controlled oscillator according to the present invention includes a voltage comparator having a positive input terminal and a negative input terminal, an output of the voltage comparator and a negative input. A resistor connected between the output terminal of the voltage comparator and a capacitor connected to a negative input terminal of the voltage comparator and charged and discharged by an output signal of the voltage comparator; A non-inverting circuit for transmitting an external control signal in a positive phase, and an output of the non-inverting circuit when the output of the voltage comparator is at a first predetermined level. A first control signal application circuit composed of switching means connected to a terminal, an inversion circuit for transmitting an external control signal in a reverse phase, and an output of the inversion circuit being a second predetermined output. And a second control signal applying circuit composed of a switching means for connecting to the positive input terminal of the voltage comparator when the bell.

(Example) Next, this invention is demonstrated, referring drawings.

FIG. 1 is a circuit diagram showing an embodiment of the voltage controlled oscillator according to the present invention.

In the embodiment shown in FIG. 1, the oscillation frequency is changed by changing the voltage applied to the plus input, instead of changing the capacitance of the capacitor connected to the minus input of the voltage comparator as shown in FIG. Variable.

In the figure, COMP2 and COMP3 is the voltage comparator are each non-inverting and inverting circuit ,, D ₁₁ to D ₁₄ diodes, R ₁₁ to R
₁₅ indicates a resistance.

Diode D ₁₁ to D ₁₄ is to define the voltage V _x4 applied to the point X _4. That is, when the voltage V _x2 of the point X ₂ is a first predetermined level or the embodiment of positive current
Due to the flow of D ₁₃ → D ₁₂ → R ₁₁ → D ₁₁ and when the voltage V _{x2 at} the point X ₂ is at the second predetermined level, that is, in the present embodiment, the current is D ₁₂ → R ₁₁ → R ₁₁ voltage applied to the point X ₄ is defined by flowing ₁₂ → D _14.

V _Be of these diodes are the generally affect the voltage at the point X ₄ but setting the resistance value of the resistor R _11, R ₁₂ as follows, this effect can be eliminated.

That is, when the output voltage at the point X ₄ is positive, the current I
Flows from D ₁₃ → R ₁₂ → R ₁₁ → D ₁₁ and the voltage V _{x4 at} point X ₄ is Becomes Here, if R ₁₁ = R ₁₂ is set, Therefore, it is possible to eliminate the influence of V _Be. This is the same when the output voltage V _x2 is negative.

The operation of the circuit shown in FIG. 1 will be described below with reference to FIG.

First, when the input voltage V _x1 is 0V, points X ₅ and voltage X ₆
Both V _x5 and V _x6 become 0V. Therefore, the voltage V _x2 is −V
When that rises from + V, the capacitor C ₁₁ is the voltage V
Is charged towards.

When the charging voltage of the capacitor C ₁₁ is higher than V _x4, inverts the output voltage V _x2, changes to -V from + V. Then, the capacitor C ₁₁ is, in turn, is discharged toward voltage -V, it becomes lower than the voltage V _x4, also the output voltage V _x2 reversed, the operation is repeated hereinafter.

The repetition frequency, that is, the oscillation frequency, is the voltage V _{x 4}
The oscillation frequency can be varied by varying the voltage _Vx4 .

When the input voltage V _x1 is V _i , the voltage V _x5 is V _i and V _x6 is −V _i . At this time, the voltage V _x4 is (V−V _i ) / 2 when the output voltage V _x2 is positive, and (−V + V) when the output of V _x2 is negative.
_i ) / 2, and when V _i is positive, | V _x4 |
By decreases, the oscillation frequency becomes high, V _i is when negative than when the 0 | V _x4 | it is found that the lower the oscillation frequency by increases.

In addition, since the absolute value of the voltage _Vx4 becomes the same between the positive side cycle and the negative side cycle, the duty ratio of the output signal can always be maintained at 50% regardless of the input voltage.

As described above, in the present invention, since the voltage-controlled oscillator itself does not have a circuit having a time constant, for example, when used as a voltage-controlled oscillator of a PLL FM demodulator, the system operates stably,
The frequency characteristics of the demodulated output can be extended to near the voltage controlled oscillation frequency. For example, a modulation signal of 6 to 7 MHz can be demodulated for an oscillation frequency of 10 MHz.

(Effects of the Invention) As described above, according to the voltage controlled oscillator of the invention, the frequency response characteristic indicating the change in the oscillation frequency of the output signal with respect to the change in the input voltage signal can be significantly improved. Also, since the duty ratio of the output signal does not change with respect to the input voltage, an oscillation output with a small even-order harmonic component can be obtained by setting the duty ratio to 50%. Furthermore, unlike a conventional circuit, a voltage-controlled oscillator can be constituted only by a diode without using a variable capacitance diode (VCP), which is advantageous in terms of cost.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a voltage controlled oscillator according to the present invention, FIG. 2 is a signal waveform diagram of each part of the circuit of FIG. 1, and FIG. 3 is a circuit diagram of a conventional voltage controlled oscillator. . COMP1～COMP4 ... voltage comparator, R ₁₁ ~R ₁₅ ... resistors, D ₁ ~D ₄ ...
diode.

Claims (1)

(57) [Scope of request for utility model registration] A voltage comparator having a positive input terminal and a negative input terminal; a resistor connected between an output of the voltage comparator and a negative input terminal; and a resistor connected to a negative input terminal of the voltage comparator. A capacitor that is charged and discharged by an output signal of the voltage comparator, a feedback circuit inserted between the output of the voltage comparator and a positive input terminal, and a non-inverting circuit that transmits an external control signal in positive phase. A first control signal application circuit comprising switching means for connecting an output of the non-inverting circuit to a positive input terminal of the voltage comparator when an output of the voltage comparator is at a first predetermined level; An inverting circuit for transmitting the control signal in the opposite phase, and switching means for connecting the output of the inverting circuit to the plus input terminal of the voltage comparator when the output of the voltage comparator is at a second predetermined level. The second control signal applying circuit and a voltage controlled oscillator, characterized in that it comprises an be made.