JPS6241508Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a hue variable circuit for PAL color signals.

Conventionally, the hue variable circuit of the circuit for obtaining a single color signal in the PAL system uses two adjusters to adjust the hue to the required hue, and it has been difficult to change the hue continuously. First, FIG. 1 shows an example of a conventional hue variable circuit, in which a subcarrier signal is supplied to an input terminal 1. In FIG. The 180° modulation circuit 3 receives the PAL signal supplied to the input terminal 2.
(PALIdent) Sends a signal whose phase is switched between +90 degrees and -90 degrees every horizontal synchronization according to the pulse. This is because in the PAL system, the subcarrier phase differs for each line.
The V-axis balance modulation circuit 4 receives the signal from the 180° modulation circuit 3 and performs balance modulation in accordance with control from the hue adjustment volume X10. The U-axis balance modulation circuit 5 receives the input subcarrier signal and performs balance modulation in accordance with control from the hue adjustment volume Y11. The output signals of the V-axis balanced modulation circuit 4 and the U-axis balanced modulation circuit 5 are vectorially combined in a combining (mixing) circuit 6 to obtain a subcarrier having a desired phase. The output of the mixing circuit 6 is sent to an output terminal 9 via a limiter circuit 7 and a filter circuit 8. The limiter circuit 7 is provided to keep the amplitude of the output constant. The filter circuit 8
is provided to remove harmonic distortion.

In order to continuously vary the hue in Figure 1, it is necessary to change the output of the volume X10 in a sine manner and the output of the volume Y11 in a cosine manner, and this is done artificially. That was actually difficult.

Therefore, the object of the present invention is to obtain continuous hue changes with only one volume change.
An object of the present invention is to provide a hue variable circuit for PAL color signals.

According to the present invention, a hue variable circuit for PAL color signals is provided with a signal generator that receives a signal from one hue adjustment volume and generates a control signal that changes in an approximately sine-like manner and a control signal that changes in an approximately cosine-like manner. is obtained.

Next, the present invention will be described in detail with reference to the drawings of an embodiment of the present invention. FIG. 2 shows an embodiment of the present invention, and in particular shows a signal generator that generates sin and cosine control signals. - Can be replaced with Y11. Figure 3 shows the second
The voltage changes at each point in the figure are shown.

First, FIG. 2 will be explained. The clip circuit 14 and the clip circuit 15 are connected to the buffer amplifier 13 in FIG. 3A.
It receives a control signal from the hue adjustment volume 12 whose voltage changes as shown in FIG. 3, and outputs the signals shown in FIGS. 3B and 3C. The amplifier circuit 16 adds and inverts and amplifies the signals from the two clip circuits. The amplifier 17 adds the signal from the amplifier 16 and the signal from the buffer amplifier 13 and performs inversion amplification. Then, at the output terminal 18, a signal that changes approximately in a SIN shape is obtained as shown in FIG. 3D.

The output of the clip circuit 19 is then the signal shown in FIG. 3E. The amplifier 21 is connected to the clip circuit 19.
A signal obtained by inverting and amplifying the output of
The signal from the input signal and the bias voltage are added together and inverted and amplified. At the output terminal 22, a signal varying in a cosine manner is obtained. Expressing this situation using the formula, (F)={(E)×2×(−
1)+(A)+V/2}×(-1), where (-1) is inversion.
Further, this situation will be explained with reference to FIG.

Here, the output of the output terminal 18 in Fig. 2 is sent to the V-axis balanced modulation circuit 4 (Fig. 1), and the output of the output terminal 22 is
If the signal is sent to the axis-balanced modulation circuit 5 (FIG. 1), a PAL color signal with continuous hue changes in response to changes in the only volume 12 can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a conventional PAL color signal hue variable circuit, Fig. 2 is a diagram showing an embodiment of the present invention,
Figure 3 is a diagram showing signal changes in the main parts of Figure 2, Figure 4
The figure shows the process of creating a signal that changes in a cos-like manner.

Claims (1)

[Scope of utility model registration request] Distinguish between input subcarrier signals and lines
a 180-degree phase modulation circuit that receives a PAL ident signal and outputs a signal with a 180-degree phase difference;
a first balanced modulation circuit that receives a signal from the degree-phase modulation circuit and a first control signal for balanced modulation; a second balanced modulation circuit that receives the subcarrier signal and a second control signal and performs balanced modulation; a combining circuit that combines signals from the first and second balanced modulation circuits;
a phase adjuster; and a control signal generator that receives an output from the phase adjuster that has linear input/output characteristics and generates signals that have sinusoidal and cosoidal output characteristics as the first and second control signals. and
PAL color signal hue variable circuit.