JPS61214607A - Control voltage generating circuit - Google Patents

Abstract

PURPOSE:To obtain a control output containing two signal components by obtaining a comparing signal by comparing the reference voltage and the first control signal voltage and obtaining a contro voltage by adding said signal to an output signal controlled by the second control signal. CONSTITUTION:A signal Vb supplied from a No.1 terminal corresponds to an AGC voltage of a video circuit in a video camera, becomes the first control signal and a signal Va supplied from a No.2 terminal determines a basic clip quantity of a chroma signal and becomes the control signal. Vref and Vb are compared and a current corresponding to its difference voltage flows through a resistance R3 and a transistor Q3 and since the transistors Q3, Q4 constitute a current mirror circuit, an output current Ic becomes that which corresponds to the difference voltage. On the other hand, by a voltage level of the voltage Va, a current I1 flowing through a transistor Q5 and an R5 is controlled, a current of I1+Ic flows to a resistance R6, a voltage drop corresponding to its current quantity is generated and it is generated as a control voltage Vc. In this way, an output of the control voltage can be made to have two kinds of control information.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a control voltage generation circuit suitable for use in electronic equipment such as a video camera.

[Background technology]

The image circuit system of a video camera uses various clip circuits to stabilize the image.

The above-mentioned clip circuit is described in "rVTR Related Basic Course" (September 16, 1981, Published by Radio Gijutsu Sha, pp. 160-165).

By the way, the inventor of the present invention, in developing a video camera,
The present invention was developed by examining whether the amount of clipping of the chroma signal could be controlled by the level of the video signal.

[Purpose of the invention]

An object of the present invention is to provide a control voltage generation circuit that can include 20 different control signal components in one control voltage.

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.

[Summary of the invention]

A brief summary of the invention disclosed in this application is as follows:
It is as follows.

That is, by comparing the reference voltage and the voltage vb, the comparison signal I
By obtaining the control voltage Vc and adding it to the output signal controlled by the control signal Va to obtain the control voltage Vc, the object of the present invention is to obtain a control output including two signal components.

[゛Example]

Hereinafter, one embodiment of a control voltage generation circuit to which the present invention is applied will be described with reference to FIGS. 1 and 2.

Note that FIG. 1 is a circuit diagram, and FIG. 2 is a characteristic diagram.

In terms of a video camera, the signal vb supplied from the No. 1 terminal corresponds to the AGC voltage of the Eirin circuit, and is the first control signal in the present invention.

In terms of a video camera, the signal Va supplied from the second terminal determines the basic base clip amount of the chroma signal, and is the second control signal in the present invention.

Note that the control signal Va is voltage-divided by a variable resistor VR.

Transistors Q+ and Qt constitute a comparison circuit, and perform a voltage comparison between the reference voltage and the control signal vb. In addition, the resistance R
,,R, are for gain control, and C8 is a constant current circuit.

Vref and vb are compared, and a current corresponding to the difference voltage flows through the resistor R1 and the transistor Q.

Since the transistors Qm-Q+ constitute a current mirror circuit, the output current Ic corresponds to the voltage difference.

On the other hand, depending on the voltage level of voltage Va, transistor Q
Current flowing through s, Rs1. is controlled.

Therefore, a current of I, +Ic flows through the resistor R6,
A voltage drop corresponding to the amount of current occurs, and this is generated as the control voltage VC. The control voltage Vc can be expressed by the following equation.

(1) The control voltage Vc includes two signal components, and the control voltage VcK of one can control two signals.

That is, as shown in FIG. 2, the voltage level of the control voltage Vc is as shown as the voltage characteristic XYZ.
Varies depending on a m V b.

〔effect〕

(1) By adding two pieces of independent control information, the control voltage output can have two types of control information.

(2) Since control signal processing can be performed using control voltages having two independent control information, functions can be diversified.

Although the invention made by the present inventor has been specifically explained above based on examples, it goes without saying that the present invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist thereof. stomach.

For example, the reference voltage Vref may be replaced with another signal.

[Application field]

In the above explanation, the invention made by the present inventor was mainly applied to video cameras, which is the field of application that formed the background of the invention, but the invention is not limited thereto (for example, video equipment such as display devices, etc.). It can be used for.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a control voltage generation circuit showing an embodiment of the present invention, and FIG. 2 is a voltage characteristic diagram for explaining circuit operation.
, Vb...control signal, It, Ic...current, Vc
...Control voltage, QI-Qs...Transistor, X,
Y, Z...Voltage bendability. No. IFI! J Figure 2

Claims (1)

[Claims] 1. A comparison circuit that outputs a comparison signal by comparing a reference voltage and a first control signal, a control circuit whose output signal is controlled by a second control signal, and adding the comparison signal and the output signal, 1. A control voltage generation circuit comprising: an adder circuit that obtains a control output including the signal in item 2 above.