JPH10256899A - Non-adjusted voltage controlled oscillator circuit - Google Patents

Abstract

(57) [Problem] To provide a non-adjustable voltage controlled oscillator circuit which is not affected by temperature characteristics and variations even when an external high-precision resistor is built in an IC. A PLL circuit having a negative feedback loop is formed from a crystal oscillator, a phase comparison circuit, a low-pass filter, an adjustment amplifier, and a first voltage control circuit. After V / I conversion of the signal in the voltage control circuit 15, a signal having a phase difference of 90 ° from the crystal oscillator 11 is output by the current control oscillator 17, and the output of the PLL circuit 18 is input to the voltage control circuit 20. The current is converted into a current by a second V / I conversion circuit composed of the same elements as the V / I conversion circuit, and the current signal adjusted by the current mirror circuit 22 is converted into a desired oscillation signal by a current control oscillator 23. Is done. By using the same first and second V / I conversion elements, element variations and changes in temperature characteristics can be compensated, and a stable oscillation frequency signal can be obtained with an inexpensive element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage controlled oscillator for outputting a constant reference frequency.

[0002]

2. Description of the Related Art In recent years, video tape recorders (hereinafter referred to as VT) have been developed.
With the reduction in prices of home electric appliances such as R), there is a need for a system for reducing the number of external components and for eliminating the need for adjustment.
In a device such as a VTR, a voltage controlled oscillation circuit (hereinafter abbreviated as a VCO circuit) is used to supply a stable reference frequency.

[0003] A conventional voltage controlled oscillation circuit will be described below. FIG. 2 shows a system configuration of a conventional voltage controlled oscillation circuit. 1 is a digital-to-analog converter circuit (hereinafter abbreviated as a DAC circuit) using a programmable ROM (hereinafter abbreviated as a PROM), 2 is a reference amplifier for voltage / current conversion (hereinafter abbreviated as V / I conversion), 3 is a high precision resistor Reference numeral 4 denotes a voltage controlled oscillator, and reference numeral 5 denotes an output terminal.

[0004] The operation of the system of the voltage controlled oscillation circuit configured as described above will be described below.

In order to adjust the output of the VCO circuit, the PROM-DAC circuit is adjusted while measuring the oscillation frequency, and bit data of a desired reference frequency is written to the PROM.
The adjusted voltage is V / I-converted into a current of a reference frequency by the amplifier 2 and the high-precision resistor 3, and a current control type oscillator oscillates a set reference frequency from the output 5. Here, when used as an FM modulator, an input signal is input to the input terminal 6 to perform V / I conversion in the VCO circuit and perform FM modulation by an oscillator.

[0006]

However, in the above-described conventional system configuration, an external high-precision resistor 3 is required in order to suppress the influence on the circuit due to variations in element characteristics and changes in ambient temperature, and the IC is built into the IC. It was difficult.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a VCO circuit having a built-in high-precision resistor 3.

[0008]

In order to achieve this object, a non-adjustable VCO circuit according to the present invention comprises a crystal oscillator, a phase comparator, a low-pass filter, an adjustment amplifier, and a first voltage-controlled oscillator. PLL with feedback loop
An unregulated voltage-controlled oscillation circuit comprising a circuit and a second voltage-controlled oscillation circuit that receives the output signal of the PLL circuit, wherein the first voltage-controlled oscillation circuit converts the input voltage signal into a current signal. A first V / I conversion circuit for converting and a first current control oscillator oscillating by the converted current signal;
A second V / I conversion circuit that converts the input voltage signal into a current signal, a current adjustment circuit that adjusts the converted current signal, and a second current control that oscillates with the adjustment current signal An oscillator and the first and second V
The / I conversion circuit is composed of the same element.

With this configuration, since the first and second V / I conversion circuits work differentially and in a buffered manner, it is sufficient that the relative values of both elements are the same, and a high-precision resistor is externally provided. Thus, a VOC circuit that stably oscillates a set reference frequency with a built-in element in a chip such as a diffusion resistor can be obtained.

Further, it is preferable that the non-adjusted voltage controlled oscillation circuit of the present invention includes a plurality of the second voltage controlled oscillation circuits in parallel.

With this configuration, the output system of the VOC circuit can be pluralized, and a VOC circuit that stably oscillates a plurality of set reference frequencies can be obtained.

[0012]

DETAILED DESCRIPTION OF THE INVENTION

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an unadjusted VCO circuit according to Embodiment 1 of the present invention.

Reference numeral 11 denotes a crystal oscillator having an oscillation frequency of 3.58 MHz used for chroma signal processing.
Reference numeral 2 denotes a phase comparator, which compares the phases of two input signals, converts the phase difference into a voltage, and outputs the voltage. 13 is a low-pass filter, 14 is a first amplifier, and 15 is a first VCO circuit. A first reference amplifier 16a, a first reference resistor 16b built as a diffusion resistor, a first transistor 16c, and a first oscillator 17.
Here, a first V / I conversion circuit is configured by the reference amplifier 16a, the reference resistor 16b, and the transistor 16c. Further, the first oscillator 17 is a current-controlled oscillator. Reference numeral 18 denotes a PLL circuit which is constituted by a portion surrounded by a dotted line. 19 is a DAC circuit by PROM, 20
Denotes a second VCO circuit, and a second reference amplifier 21a,
A second reference resistor 21b built in as a diffused resistor, a second transistor 21c, a current mirror circuit 2
2. It comprises a second oscillator 23. Here, a second V / I conversion circuit is constituted by the second reference amplifier 21a, the second reference resistor 21b, and the second transistor 21c. Further, the second oscillator 23 is a current-controlled oscillator. 24 is an output terminal.

In the above configuration, the first V / V
The components of the I-conversion circuit and the components of the second V / I conversion circuit are configured by the same component. That is, the first reference amplifier 16a, the second reference amplifier 21a, and the first reference resistor 16a
b, the second reference resistor 21b, and the second transistor 16c
And the second transistor 21c are the same.

The operation of the system of the non-adjusted voltage controlled oscillation circuit configured as described above will be described below.

The oscillation frequency of the crystal oscillator 11 is 3.58.
The reference signal of MHz is input to the phase comparison circuit 12 of the PLL circuit 18. The phase comparison circuit 12 has a first VCO
The output of the circuit 15 is also input, and the phases of the two signals are compared. The phase comparison circuit 12 outputs the phase difference as a DC voltage signal, and the output signal of which the high-frequency component is removed by the low-pass filter 13, amplified by the first amplifier 14, and input to the first VCO circuit 15. First VCO
The circuit 15 has a V / I conversion circuit, and an input DC voltage signal is converted into a current signal by a first reference amplifier 16a, a first reference resistor 16b, and a first transistor 16c.
The converted current signal is input to the first oscillator 17, where the input current value is 3.58M
It is controlled in the V / I conversion so that the current signal value oscillates at Hz. Thereby, the current control type oscillator 17
Can stably output an oscillation signal at 3.58 MHz, and the phase advances by 90 ° from the capacitor characteristics. Therefore, in the above-mentioned PLL loop circuit, the phase comparator 12 is stably at 90 ° at the same frequency. Two signals having a phase difference are supplied, and the output value of the PLL circuit 16 also becomes a stable output.

Next, the output from the PLL circuit 18 is changed to the second V
Input to the CO circuit 19. The input voltage signal is applied to V by a reference amplifier 21a, a reference resistor 21b, and a transistor 21c.
/ I conversion. The V / I-converted current output value is adjusted by the current mirror circuit 22 to a desired output current signal value to be input to the oscillator 23. The adjusted current signal is input to the oscillator 23, converted into a desired oscillation frequency signal, and output from the output terminal 24.

Here, the VCO circuit 1 and the VCO circuit 2 are V / I conversion circuits composed of the same elements, and perform buffering and compensating operations for the entire circuit. In other words, even if the reference resistances 16b and 21b have element variations and the actual resistance values are slightly different from the design values, the reference resistances 16b and 2b
Since the same circuit is used between 1b, the first VCO compensates for the deviation of the second VCO circuit in the entire circuit. Furthermore, even if the resistance value changes due to the temperature characteristic change, the same compensation effect can be obtained because the two temperature characteristic changes are the same.

The non-adjustable VCO circuit of the above embodiment is
The use of crystal oscillators for chroma signals widely used in TRs, etc., and the use of inexpensive and built-in elements due to the differential and buffering functions of the circuit, prevents changes in environmental conditions such as temperature and the effects of element variations. On the other hand, a stable output signal can be supplied.

(Embodiment 2) Hereinafter, Embodiment 2 of the present invention will be described.
Will be described.

The second embodiment is characterized in that a plurality of second VCO circuits and a plurality of output systems are provided as compared with the first embodiment. The configuration and operation of a plurality of second VCO circuits may be the same as those of the second VCO circuit of the second embodiment. Now, there are two outputs, and the current value of the current mirror is set so that the oscillator of one of the second VCO circuits oscillates at 1.3 MHz. As described in the first embodiment, the second VCO circuit stably outputs an oscillation frequency signal of 1.3 MHz. Similarly, the current value of the current mirror is set so that the oscillator of the other second VCO circuit oscillates at 1.7 MHz. This second VCO circuit stably outputs an oscillation frequency signal of 1.7 MHz. In the non-adjusted voltage controlled oscillation circuit according to the present embodiment, the oscillation frequency of one of the second VCO circuits is 1.3 MHz of the VHS standard, and the oscillation frequency of the other VCO circuit is Is 1.7 MHz of the VHS standard.

With this configuration, 1.3 MHZ, which is the reference frequency required by the VHS standard such as HiFi-VTR, is used.
An output having an oscillation frequency of z and 1.7 MHz can be supplied stably.

[0023]

According to the non-adjusted voltage controlled oscillation circuit of the present invention, the stable oscillation frequency from the chroma signal processing crystal oscillator widely used in VTRs and the like can be controlled by the VOC of the present invention.
The cost can be reduced by supplying the circuit.
Also, the first and second circuits are operated by the differential and buffering functions of the circuit.
As long as the relative values of the V / I conversion circuit elements are the same, an inexpensive and built-in element such as a diffusion resistor built into the chip can be used. Stable output signals can be supplied.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an unadjusted VCO circuit according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional non-adjustment circuit;

[Explanation of symbols]

 Reference Signs List 1,19 PROM-DAC circuit 2, 16a, 21a Reference amplifier 3 External high-precision resistor 4, 17, 23 Current-controlled oscillator 5, 24 Output terminal 11 Crystal oscillator 12 Phase comparison circuit 13 Low-pass filter 14 Adjustment amplifier 15 First VCO circuit 16b, 21b Reference resistor 16c, 21c Transistor 18 PLL circuit 20 Second VCO circuit 22 Current mirror circuit 25 V / I conversion circuit

Claims (2)

[Claims] 1. A PLL circuit in which a negative feedback loop is formed by a crystal oscillator, a phase comparison circuit, a low-pass filter, an amplifier, and a first voltage controlled oscillation circuit, and a second voltage to which an amplifier output signal of the PLL circuit is input. An unregulated voltage-controlled oscillation circuit comprising a control oscillation circuit, wherein the first voltage-controlled oscillation circuit converts an input voltage signal into a current signal by a first V / I conversion circuit and the converted current signal. A first current-controlled oscillator that oscillates, wherein the second voltage-controlled oscillator converts a second V / V to convert an input voltage signal into a current signal.
An I-conversion circuit, a current adjustment circuit for adjusting the converted current signal, and a second current-controlled oscillator oscillated by the adjustment current signal, wherein the first and second V / I conversion circuits are constituted by the same element A non-adjustable voltage controlled oscillator circuit characterized by the following. 2. The non-adjusted voltage controlled oscillation circuit according to claim 1, wherein a plurality of said second voltage controlled oscillation circuits are provided in parallel.