JPH02188087A - Cr constant control circuit - Google Patents

Abstract

PURPOSE:To realize the CR constant control circuit which can set a CR constant with high accuracy by providing a CR constant circuit which receives a reference frequency signal, makes the phase by 45 deg., and sets the level to (2-1/2) time as high as the reference frequency signal. CONSTITUTION:The emitter output (reference frequency signal) of a transistor(TR) Q1 is inputted to the CR constant circuit composed of a resistance R3 and a capacitor C3. The element constant of the resistance R3 and capacitor C3 of this CR constant circuit is so determined as to generate an output signal V2 whose phase leads the reference frequency signal V1 by 45 deg. and whose level is (2-1/2) time as high as that of the reference frequency signal V1. The output signal V3 of a phase synthesizing circuit and a reference frequency signal V1' are supplied to a phase detecting circuit PC and a control voltage V0 is made into the control voltage of the capacitor C3 according to the phase difference between the V1' and V3. Consequently, the vector composite voltage of the resistance R3 and capacitor C3 of the CR constant circuit is equal to that of the reference frequency signal V1. Then the phase difference between the voltages of the resistance R3 and capacitor C3 is held at 90 deg..

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a CR constant control circuit, and relates to a technique that is effective for use in a CR constant circuit used in a color signal processing circuit in a video tape recorder, for example. It is.

[Conventional technology]

Manufacturing variations in the characteristics of elements formed in semiconductor integrated circuits are relatively large, and in order to obtain the desired oscillation frequency and frequency characteristics, the resistors and capacitors that make up the oscillation circuit and filters are constructed from external components and adjusted. We will adopt a method to do so. In this case, adjustment costs and component costs increase, so attempts have been made to eliminate the need for adjustment in these circuits. for example,
■The ``HA11856'' semiconductor integrated circuit device for color signal processing sold by Hitachi uses a PLL (phase locked loop) method. This method supplies a constant reference frequency formed by a crystal oscillation circuit and an oscillation signal to be controlled formed by a voltage-controlled oscillation circuit to a phase detection circuit, and generates a control voltage corresponding to the difference between them. and is supplied to a variable junction capacitance element (varicap) constituting the voltage controlled oscillation circuit.

This allows the reference frequency and the oscillation frequency to match accurately. The control voltage has the same structure as the varicap of the voltage-controlled oscillation circuit, and the varicap constituting the active filter or other voltage-controlled oscillation circuit can obtain sufficient bareness by being placed close to the varicap. It is also supplied to the semiconductor integrated circuit to absorb and control manufacturing variations in the CR constant formed by the semiconductor integrated circuit.

Regarding the CR constant control circuit, please refer to Japanese Patent Application No. 62-204.
There is No. 069.

[Problem that the invention seeks to solve]

The PLL system described above requires a voltage-controlled oscillator circuit, a phase detection circuit, and a loop filter, which constitute the PLL circuit, and has the disadvantage that it requires a large number of elements and has a complicated circuit configuration.

Furthermore, since the circuit configuration becomes complicated as described above, there is a problem in that the bareness of the element becomes insufficiently accurate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a C constant control circuit that can set the CR constant with high precision using a relatively simple configuration.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means for solving problems]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, when receiving a reference frequency signal, the phase is 45
° A CB consisting of a resistor and a variable capacitance element and a constant circuit are provided to form a first signal whose level is set to 2-1/2 of the reference frequency signal, and the reference frequency signal and the first signal are control to form a second signal according to the voltage generated in the resistor and the variable capacitance element by a phase synthesis circuit, phase detect the reference frequency signal and the second signal, and make the difference 906. A voltage is generated to control the variable capacitance element.

[Effect]

According to the above means, by providing relatively simple circuits such as a reference frequency oscillation circuit, a phase synthesis circuit, a phase detection circuit, etc. in the CR constant circuit to be controlled, the CR constant of the CR constant circuit can be adjusted to a desired value. It becomes possible to control it so that it has a value.

〔Example〕

FIG. 1 shows a circuit diagram of an embodiment of a CR constant control circuit according to the present invention. Each circuit element in the figure is formed on a single semiconductor substrate such as, but not limited to, single crystal silicon using known semiconductor integrated circuit manufacturing techniques. Note that capacitors CI, C2, C4 and resistor R1 are connected via external terminals P1 to P3.
In addition, the crystal resonator X is constituted by external parts.

A resistor R1, capacitors CI and C2, and a crystal resonator X connected through external terminals P1 and P2 constitute a crystal oscillation circuit together with an amplifier circuit configured in a semiconductor integrated circuit. The reference frequency signal formed by this oscillation circuit is
It is obtained from terminal P2 and supplied to an emitter follower circuit consisting of transistor Q1 and a constant current source provided at its emitter. This emitter follower circuit operates as a buffer amplifier (impedance conversion).

The emitter output (reference frequency signal) Vl of the transistor Q1 is connected to a resistor It3 and a capacitor C3 on the one hand.
This is input to the CR constant circuit.

In this CR constant circuit, the element constants of the resistor R3 and the capacitor C3 are such that the output signal ■2 has a phase lead of 45 degrees with respect to the reference frequency signal v1 and a level of 2'''172, as shown in FIG. The capacitor C3 is formed by
It is composed of the varicap.

In FIG. 1, the signal v2 is output (V2'') through an emitter follower circuit consisting of a transistor Q3 and a constant current source.The reference frequency signal 1 obtained from the emitter of the transistor Q1 is It is output (v1') through an emitter follower circuit composed of Q2 and a constant current source.

The phase is delayed by 45 degrees with respect to the reference frequency signal ■1° (=V1) and the level is the signal V I I) as shown above.
2-I/2 Kshuri (N No. V 2' (=V 2
) C. Input to the next phase synthesis circuit.

Differential amplifier circuits 1, 2.3 (AMPl, AMP2゜AMP3) that operate linearly with respect to the above signals v1'', ■2'
In, ■2'' is input so as to have an opposite phase with the output of AMPI, v1' is inputted to the same phase input with respect to the output of 1viP2, V2' is inputted to the opposite phase input of AMP2,
AMP1 for AMP3.

The output of AMP2 is input for addition operation.

As a result, the output of AMP3 is V2' for ■1'.
When Vl' is delayed by 45 degrees, the signal v3 is delayed by 90 degrees with respect to Vl'.

Note that from the collector of the transistor Q5, a signal having an opposite phase to the signal V2' supplied to its base and the above signal v1 are sent.
A signal C (third
) is formed. This signal C is the signal v3
It becomes a signal with equal level and opposite phase. This signal C is supplied to the common emitters of differential transistors Q8 and Q9 that constitute the phase synthesis circuit. Since the bias voltage VBI is supplied from the collector of the transistor Q6 to the base of the transistor Q7 which constitutes a differential amplifier with the transistor Q6, a signal d having an opposite phase to the above signal 2'' is formed.This signal d is supplied to the common emitter of the differential transistors QI O and Ql 1 that constitute the phase synthesis circuit. By making the collectors of the transistors Q8 and QIO common, a vector composite signal of the above signals C and d is obtained. Then, it is fed back to the terminal P1 through an emitter follower circuit consisting of a transistor Q12 and a constant current source.

``In addition, the bases of transistors Q8, Q, and 11 are shared and bias voltage VB2 is supplied, and transistor Q
9 and QIO bases are shared and bias voltage VB3
is supplied. In order to give a constant gain to the above feedback signal, the collectors of the upper a pito2/transistors Q8 and Q9 are
A resistor R4 is provided.

This causes the crystal oscillation circuit to perform an oscillation operation.

Output signal ■3 of the above phase synthesis circuit and reference frequency signal Vl
' is supplied to the phase detection circuit PC.

A capacitor C4 having a relatively large capacitance value is externally connected to the output of the phase detection circuit PC via an external terminal P3. This control voltage (20) is made into the control voltage of the capacitor C3 according to the phase difference of Vl' (30).

The vector composite voltage of the resistor R3 and the capacitor Q3 in the CR constant circuit becomes equal to the reference frequency signal V1. The phase difference between the voltages of the resistor lmo3 and capacitor C3 is maintained at 90°. Therefore, if the element constants of resistor R3 and capacitor C3 change from the above set values due to manufacturing variations, the locus drawn by voltage v2 obtained across capacitor C3 will be a semicircle as shown by the dotted line in FIGS. 2 and 3. become. This is known as a circle diagram in a CR series circuit. For example, when the capacitance value of capacitor C3 is made smaller than the set value, as shown in FIG.
(=v2) has a small phase delay (for example, 35°) like b', and the level increases accordingly. Therefore, using this as a reference, the signal 3 formed by the phase synthesis circuit has a phase difference of less than 90° with respect to Vl'.

As a result, the phase detection circuit PC, depending on the phase difference,
Increase control voltage ■0. A constant DC bias voltage (
Since VB-VB,E) is supplied, the above control voltage V
As O becomes larger, the reverse bias voltage of the PN junction becomes relatively smaller, increasing the capacitance value. As a result, it is possible to obtain the signal 2 having the phase and level relationship shown by the solid lines in FIGS. 2 and 3. Conversely, when the capacitance (direction) of capacitor C3 increases, the above phase difference becomes 90' or more, and the above control voltage ■0
becomes smaller, so contrary to the above case, capacitor C3
The above signal (2) can be obtained by reducing the capacitance value of (2). The same holds true even if there is variation in the solder resistance value of the resistor R3. That is, the phase and level of the signal (2) are determined by the relative relationship between the impedances of the resistor R3 and capacitor C3. In other words, when a variation occurs such that the resistance value of the resistor R3 becomes small, the voltage generated at the resistor R3 becomes small, and the voltage 2 generated at the capacitor C3 becomes relatively large, which is similar to the case where the capacitance value becomes small. , the phase advances with respect to the above reference of 45°. Conversely, if the resistance value of resistor R3 increases, the voltage generated at resistor R3 increases, and the capacitor C
3 becomes smaller and its capacitance value becomes larger, so that the phase can be shifted relative to the above-mentioned standard of 45°.

In Figure M1, as in the circuit surrounded by the dotted line, a similar resistor R8 is installed near the resistor R3 and capacitor C3.
and a capacitor C5. To this capacitor C5,
By supplying the control voltage vO, the CR constant consisting of the resistor R8 and capacitor C5 has the same variation as that of the resistor R3 and capacitor C3. A highly accurate CR constant can be obtained similarly to the capacitor C3. Thereby, a CR constant circuit without adjustment can be obtained. When this CR constant circuit is used, for example, as a low-pass (Low Pa5s) filter LPF, the input signal Vin is supplied through a 7-emitter lower circuit consisting of a transistor Q13 and a constant current source similar to the above. In this case, the same bias voltage VB as described above is supplied to the transistor Q13.

Further, the CR constant circuit can be configured as an emitter capacitor heavily coupled multivibrator to configure an oscillation circuit.

Note that in FIG. 1, a voltage for correcting the reference frequency signal and its phase difference may be supplied to the bias terminal VB3. For example, in a color signal processing circuit for a VTR, in recording mode, a control voltage is supplied according to the phase difference between the color subcarrier and the oscillation frequency. As a result, the phase of the feedback signal supplied to the terminal P1 in the oscillation circuit by the phase synthesis circuit is controlled, and as a result, the oscillation frequency of the crystal oscillation circuit performs an oscillation operation in accordance with the color subcarrier. This oscillation frequency signal is converted into a carrier wave for forming a reduced converted color signal for recording by controlling its oscillation frequency. And when in playback mode,
Since the fluctuation of the control signal is made zero (bias voltage VB3), a highly stable oscillation operation is performed which is controlled to suppress variations in the CR element constants as described above. This allows inverse conversion of color signals in playback mode.

The effects obtained from the above examples are as follows. That is, (1) A CR constant consisting of a resistor and a variable capacitance element that receives a reference frequency signal and forms a first signal whose phase is 45'' different from that and whose level is set to 2-1/2 of the reference frequency signal. A circuit is provided to form a second signal according to the voltage generated in the resistor and the variable capacitance element from the reference frequency signal and the first signal, and phase-detect them so that there is a 90' difference between the two. A control voltage is formed to control the variable capacitance element.This allows relatively simple circuits such as a reference frequency oscillation circuit, a phase synthesis circuit, a phase detection circuit, etc. By simply adding a circuit, it is possible to control the above-mentioned CR constant to a desired constant, which provides five advantages.

(2) According to the above (1), since the CR constant circuit can be built into the semiconductor integrated circuit, it is possible to achieve the effect that no adjustment of the CR constant circuit can be realized.

(3) The above (1) provides the effect that the number of external components and terminals of a semiconductor integrated circuit that requires a C constant circuit can be reduced.

(4) With the simplification of the above circuit, when configuring another CR constant circuit to be controlled by utilizing the bare nature of the semiconductor integrated circuit, the other CR constant circuit can be provided in close proximity. This has the effect of increasing accuracy.

(5) Sensitivity to waveform distortion, which was the case with the level detection method, is reduced, and Vcc dependence and temperature dependence are reduced.

Although the invention made by the present inventor has been specifically explained based on Examples above, the present invention is not limited to the above-mentioned Examples, and it goes without saying that various changes can be made without departing from the gist thereof. Nor. For example, the two signals taken out by the phase synthesis circuit and subjected to phase detection may be any signal as long as they are in accordance with the voltages respectively generated by the resistor and capacitor in the CR constant circuit.

For example, in FIG. 3, instead of the signal 3, a signal C having the opposite phase may be used.

The specific circuit may be of any type.

Note that when a phase synthesis circuit is used to add a feedback amplification function and a frequency control function to perform the oscillation operation of the crystal oscillation circuit, the combination of the embodiment shown in FIG. 1 is optimal.

Furthermore, the specific configuration of the circuit that converts the voltage generated in the resistor and capacitor forming the OR circuit into a direct current can be modified in various embodiments. Further, the capacitor constituting the C) L constant circuit may be any capacitor whose capacitance value changes depending on the voltage signal.

The present invention can be widely used in various Ch constant circuits built into semiconductor integrated circuits.

〔Effect of the invention〕

A simple explanation of the effects obtained by typical inventions disclosed in this application is as follows. That is, when a reference frequency signal is received, the phase is 45 degrees different from that, and the level is 2-1/2 of the reference frequency signal.
Resistance and variable capacity forming the first 100 installed in 2: l
A C It constant circuit consisting of a t-coupler is provided to form a second signal according to the voltage generated in the resistor and the variable capacitance element from the reference frequency signal and the first signal, and phase-detect them. , a control voltage for controlling the oJ variable capacitance element is formed so that both are equal. As a result, CI- configured by a semiconductor integrated circuit can be compared to a constant circuit.
By simply adding relatively simple circuits such as a reference frequency oscillation circuit, a phase synthesis circuit, a phase detection circuit, etc., it becomes possible to control the C constant to have a desired constant.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a circuit diagram showing an embodiment of C) constant control circuit maintained in the present invention; Fig. 2 is a vector diagram showing signals passing through the CR constant circuit; FIG. 3 is a vector diagram for explaining the control operation. AMPI, AM)'2, AMP3...Linear amplifier, PC...Phase am circuit, LPF...Low pass filter Fig. 2 Fig. 3

Claims (1)

[Claims] 1. An oscillation circuit that generates a reference frequency signal, which receives the reference frequency signal, has a phase difference of 45 degrees from the reference frequency signal, and has a level 2^-^1^/^2 of the reference frequency signal. C consisting of a resistor and a variable capacitance element that forms the first signal to be set.
an R constant circuit; a phase synthesis circuit that receives the reference frequency signal and the first signal and forms a second signal according to the voltage generated in the resistor and the variable capacitance element; and the reference frequency signal and the first signal. A phase detection circuit that receives the second signal, a control voltage generation circuit that generates a control voltage corresponding to the phase difference, and a negative feedback loop that uses the control voltage as a control voltage of the variable capacitance element. Characteristic CR constant control circuit. 2. The resistor and the variable capacitance element are formed in a semiconductor integrated circuit, and the semiconductor integrated circuit includes a resistor that is provided in close proximity to the resistor and the variable capacitance element, and the control voltage is supplied to the variable capacitance element. Claim 1, characterized in that a CR constant circuit comprising a variable capacitance element and receiving an input signal different from the reference frequency is provided.
The CR constant control circuit described in .