JP2957867B2 - Control device for analog circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control apparatus for an analog circuit which can be achieved with a small number of signal paths and a small number of elements when controlling the analog circuit.

[0002]

2. Description of the Related Art In a TV receiver or audio equipment, an IC for processing an analog signal may be controlled by a control signal from a microcomputer. For example, in the case of a TV receiver, commands such as television signal taint and color density are temporarily fetched by a microcomputer from a viewer and applied from the microcomputer to an analog IC.
FIG. 2 shows an apparatus for performing such control. In FIG. 2, a plurality of PWMs are provided inside the microcomputer (1).
(Pulse wave modulation) circuits (2) to (4) are arranged, and pulse width-modulated pulse signals from each PWM circuit are converted into analog signals by integration circuits (5) to (7), and the analog IC ( 8) is applied to the controlled circuits (9) to (11). However, in the method of FIG. 2, one control line is required for each control, and the number of pins of the microcomputer and the IC increases, and the wiring becomes complicated.

FIG. 3 shows a method of transmitting a digital signal by time division and using a clock line and a data line to transmit the signal. In FIG. 3, digital data synchronized with the clock signal is applied from the microcomputer (1) to the analog IC (8). Analog IC
The address control circuit (12) in (8) decodes the incoming digital data, selects to which controlled circuit data is being transmitted, and distributes the digital data to the selected controlled circuit. doing. The digital data is converted into an analog signal by D / A conversion circuits (13) to (15), and then the controlled circuits (9) to (11)
Is applied to

In the method shown in FIG. 3, a plurality of types of control signals can be transmitted by two signal lines.

[0005]

However, the method of FIG. 3 requires a plurality of D / A conversion circuits (13) to (15) inside the analog IC (8). Having many D / A conversion circuits leads to an increase in chip area, which is a problem.

On the other hand, since the microcomputer (1) is made of MOSIC, there is no problem even if a D / A converter having a large number of elements is present. For this reason, there has been a demand for a transmission method in which the number of signal lines is small and the microcomputer performs D / A conversion processing.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is an analog circuit control device for controlling a plurality of controlled circuits in an analog IC by an external control voltage. A first input terminal to which a control voltage that changes to a plurality of levels is applied in a time-sharing manner, and a switching signal that arrives at the same timing as the time-sharing timing of the control voltage, the level indicating the type of the control voltage A second input terminal to which a control voltage is applied from the first input terminal, a plurality of DC hold circuits for applying a DC voltage held by the plurality of controlled circuits, and a plurality of comparators. A comparison and switching control circuit for determining a level of a switching signal from the second input terminal and operating a desired DC holding circuit among the plurality of DC holding circuits ; A deflection circuit for generating vertical pulses.
The first and second signals are generated during the generation of the vertical pulse.
It is characterized by taking in a signal from an input terminal.

[0008]

According to the present invention, the control voltage is transmitted in a time-division manner and the switching signal indicating the type of the time-division-divided control voltage is divided according to the level. Signal transmission is possible.
Further, according to the present invention, since the control voltage and the switching signal are transmitted during a vertical pulse period that is not displayed on a TV screen, the transmission does not affect the screen.

[0009]

FIG. 1 shows a control device according to the present invention.
(16) a first D / A converter that generates a control voltage for a TV signal that changes to a plurality of levels in a time-division manner; (17)
Are generated at the same timing as the time division timing of the control voltage, and the level of the second D / A converter generates a switching signal indicating the type of the control voltage. A control voltage of the A converter (16) is applied, and first to third D applying a DC voltage held in the first to third controlled circuits (9) to (11).
The C hold circuit (21) has a plurality of comparators, determines a level of a switching signal from the second D / A converter (17), and selects a desired DC hold circuit from the plurality of DC hold circuits. And (22) and (23) are the first and second D
A filter for removing noise in the output signals of the / A converters (16) and (17); (24) a deflection circuit for applying a vertical pulse of a TV signal to the vertical output IC (25) and the microcomputer (1); ) Is a deflection coil of a cathode ray tube (27) to which a vertical deflection pulse from the vertical output IC (25) is applied, (38) is a first input terminal, and (39) is a second input terminal.

FIG. 4A shows a second D / A converter (1).
7) shows the output signal level, and FIG.
The output signal level of the A converter (16) is shown.
The horizontal axis in FIGS. 4A and 4B is time, and the control of the taint, color, and contrast, which are controls for the TV signal, is performed as time passes. First, the taint will be described. The level of the taint switching signal generated from the second D / A converter (17) is set between 0.5 V and 1.0 V in FIG. 4A, and can take any value within this range. In this case, it is 0.75V. During the period in which the 0.75 V taint switching signal is being generated, a 2 V control voltage is generated from the first D / A converter (16), and the first to third signals in the analog IC (8) are generated.
It is applied to DC hold circuits (18) to (20). On the other hand, the comparison and switching control circuit (21) determines, based on the level of the switching signal of 0.75 V, that the incoming control voltage is for tainting, and the first to third DC hold circuits (18) to (18). 1D of (20)
Only the C hold circuit (18) is operated. Then, the first DC hold circuit (18) holds the control voltage of 2V, and applies the held voltage to the first controlled circuit (9).

Therefore, according to the apparatus shown in FIG. 1, taint control can be performed. By the way, in the apparatus shown in FIG. 1, a plurality of controls are performed in a time series. Therefore, before the first DC hold circuit (18) holds the control voltage of 2V, another control (for example, brightness) is generally performed. Therefore, when the level of the previous control voltage greatly differs from the level of the next control voltage, it is conceivable that the transition from the previous control voltage to the next control voltage cannot be made immediately due to the influence of the time constant of the filter (22). Therefore, in the present invention, the period between two time-division controls is set to a period in which the first to third DC hold circuits (18) to (20) are all prohibited from holding the input voltage. During this period, since the next control voltage of the first D / A converter (16) is applied, the voltage of the pin of the analog IC (8) has completely shifted to the next control voltage, The control voltage can be stably taken in. In the example of the taint, as shown in FIG. 4A, 0.75 V is supplied from the second D / A converter (17).
The control voltage of 0.25 V is generated before the control voltage of. When the control voltage of 0.25 V is applied to the comparison and switching control circuit (21), the control circuit (21)
Are the first to third DC hold circuits (18) to (2)
0) The input fetch operation is prohibited.

FIG. 5 shows a specific circuit diagram of the comparison and switching control circuit (21) of FIG.
It is the taint period of (a), and it is assumed that a switching signal of 0.75 V is applied to the input terminal (24). First to fourth
Reference power supply (29) for comparators (25) to (28)
(32) are set to 0.5V, 1V, 1.5V and 2.0V. Therefore, only the output of the first comparator (25) becomes "H" level, and the outputs of all other comparators become "L" level. For this reason, the level of the output terminal (33) becomes “H” level,
Only during the level period, the first DC hold circuit (1
8) The switch (34) is closed. That is, the first and second
Comparators (25) and (26), inverter (3
5) and the AND gate (36) constitute a window comparator, and detect an input voltage between 0.5 V and 1.0 V as an “H” level.

If a switching signal of 0.25 V is applied to the input terminal (24), since it is not included in any of the ranges of the two window comparators in FIG. 5, the level of the output terminals (33) and (37) Are at the “L” level. Therefore, the first to third DC hold circuits (18) to (20) in FIG. 1 stop the capturing operation. Next, it is assumed that a transition is made to the color control period shown in FIG.
Then, the switching signal of 1.25 V is applied to the input terminal (2
4) and output terminals (33) and (37)
It becomes the “L” level. Next, when a switching signal of 1.75 V is applied to the input terminal (24), only the output terminal (37) becomes "H" level, and the second DC hold circuit (19) of FIG. ) Is taken in.

Therefore, a color control voltage can be applied to the second controlled circuit (10). Thereafter, FIG.
The contrast of (a) can also be applied to the third controlled circuit (11) of FIG. By the way, signal transmission from the microcomputer (1) to the analog IC (8) is not preferable during the period when the video signal is displayed on the TV screen. That is, since a pulse signal is transmitted through a pin of the IC, unnecessary radiation is generated from the pin, which adversely affects a video signal appearing on a screen. The first to third DC hold circuits (18) to (20) in the analog IC (8)
Even if the DC capturing period ends, the operation cannot be stopped immediately, and the charged capacitor is slightly discharged. Then, a DC signal having a DC offset appears at the output of the DC hold circuit.
The control amount for the controlled circuit in (8) changes. If the screen is being displayed, this offset directly affects the screen.

Therefore, in the present invention, a signal is transmitted using a period in which no image is displayed on the screen.
In such a period, there is no problem even if unnecessary radiation is generated from the pins of the IC or if the final value is constant even if the initial value of the DC voltage to be transmitted has an offset. In the embodiment of FIG. 1, signal transmission is performed using a vertical pulse period. A vertical pulse is generated from a deflection circuit (24) for processing a horizontal or vertical synchronization signal in the analog IC (8), and is applied to a vertical output IC (25) to become a vertical deflection pulse. Applied to the coil (26). The vertical pulse is taken into the microcomputer (1), and the switching signal and the control voltage shown in FIGS. 4A and 4B are generated by using the application of the vertical pulse as a trigger. During this vertical period, the first to third DC hold circuits (18) to (20) may be controlled once or, if necessary, two or more times.

FIG. 6 shows the details of the waveform of FIG. 4 and the vertical pulse. FIG. 6A shows the switching signal in FIG.
(B) shows the control voltage. In the fall of the vertical pulse at time t _1, the microcomputer (1) FIG. 1 recognizes the arrival of the vertical pulse. Then, first, the control voltage is generated at time t ₂ after a predetermined time, the control voltage for transmitting switching signals from time t ₃ when the expected that it would be stable. As a result, a stable voltage (2 V) can be obtained.
Then, at time t ₄ , the switching signal is in the taint range (0.
Once in 1.0 V) from 5V, the voltage (2V) is taken until the time t ₅ exceeding the range. Then begins after the lapse of the time t ₅ a predetermined time the control voltage beginning (time t ₆₎ is changed to the next control voltage (3V). This time is also calculated in advance and programmed in the microcomputer (1). As a result, a stable control voltage of 2 V can always be transferred. This transmission method can be applied regardless of whether or not vertical pulses are used. However, when performing transmission using vertical pulses, it does not matter what the initial value is if the final value to be held is correct. since there is no need to consider the order of the time t ₃ and time t ₄ in FIG. Therefore, there is an advantage that the program of the microcomputer (1) can be omitted.

[0017]

As described above, according to the present invention, a plurality of controlled circuits can be controlled by two signal paths.
Further, according to the present invention, since the D / A converter is provided on the microcomputer side and the comparison and switching control circuit is provided on the analog IC side, the device can be configured with a small number of elements.
Further, according to the present invention, since the control voltage is transmitted during the vertical pulse period, there is an advantage that the adverse effect on the TV screen can be prevented.

[Brief description of the drawings]

FIG. 1 is a control device of an analog circuit using a microcomputer of the present invention.

FIG. 2 is a control device of an analog circuit using a conventional microcomputer.

FIG. 3 shows a control device for an analog circuit using a conventional microcomputer.

FIG. 4 is a waveform chart for explaining FIG. 1;

FIG. 5 is a specific circuit diagram of the comparison and switching control circuit (21) of FIG. 1;

FIG. 6 is a detailed waveform diagram of FIG.

[Explanation of symbols]

 (1) Microcomputer (8) Analog IC (16) First D / A converter (17) Second D / A converter (18) First DC hold circuit (19) Second DC hold circuit (20) Third DC hold circuit (21) Comparison and switching control circuit

Claims (2)

(57) [Claims] 1. An analog IC according to an external control voltage.
A control device for an analog circuit for controlling a plurality of controlled circuits, wherein a first input terminal to which a control voltage that changes to a plurality of levels is applied in a time-sharing manner is the same as a time-sharing timing of the control voltage A second input terminal to which a switching signal whose level indicates the type of the control voltage is applied; and a control voltage from the first input terminal is applied to the plurality of controlled circuits. A plurality of Ds for applying a held DC voltage
A comparison and switching control circuit, comprising: a C hold circuit; and a plurality of comparators, wherein the level of a switching signal from the second input terminal is determined to operate a desired DC hold circuit among the plurality of DC hold circuits. And a deflection circuit for generating a vertical pulse of the TV signal.
The first and second input terminals during the generation of the vertical pulse.
Analog circuit characterized by taking in signals from a child
Control device. 2. The control voltage from a microcomputer.
To control a plurality of controlled circuits in an analog IC.
A control device for a log circuit, wherein a control voltage that changes to a plurality of levels is generated in a time-division manner.
1D / A converter , at the same timing as the time division timing of the control voltage
Switching that occurs and whose level indicates the type of control voltage
Microphone having second D / A converter for generating signal
Computer and a control voltage of the first D / A converter
A plurality of Ds for applying a DC voltage held in a number of controlled circuits
A second D / A converter having a C hold circuit and a plurality of comparators;
From the plurality of DC signals.
Activate the desired DC hold circuit among the hold circuits
A comparison and switching control circuit, and a deflection circuit for generating a vertical pulse of the TV signal.
It includes a analog IC, a, the My vertical pulses from the analog IC
And applied to the microcomputer during the vertical pulse period.
The control voltage and the switching signal are transmitted.
A control device for an analog circuit, characterized in that: