JPH07131739A - Controller for analog circuit using microcomputer - Google Patents

Abstract

PURPOSE:To control plural controlled circuits through two signal paths by sending a control voltage in a time division way and dividing a switching signal representing a kind of the control voltage subject to time division depending on a level. CONSTITUTION:A level of a tint switching signal generated from a 2nd D/A converter 17 of a microcomputer 1 is set between, e.g., 0.5 and 1.0V and set to 0.75V in this embodiment. A 1st D/A converter 16 generates a control voltage of 2V for this period and the control voltage is applied to 1st-3rd DC hold circuits 18-20 in an analog IC 8. On the other hand, a comparison and changeover control circuit 21 activates only the circuit 18. The circuit 18 holds the control voltage of 2V and the control voltage is applied to a 1st controlled circuit 9. Through the constitution above, the circuits 18-20 are inhibited for holding an input voltage for the time division control period. Since a succeeding control voltage is received for this period, the control voltage is stably received.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In a TV receiver or an audio device, an IC for processing an analog signal may be controlled by a control signal from a microcomputer (microcomputer). For example, in the case of a TV receiver, commands such as the taint of a television signal and the color density are once taken in by the viewer and applied to the analog IC from the microcomputer.
An apparatus for performing such control is shown in FIG. In FIG. 2, a plurality of PWM (pulse wave modulation) circuits (2) to (4) are arranged inside the microcomputer (1) and each PW
The pulse width-modulated pulse signal from the M circuit is converted into an analog signal by the integrating circuits (5) to (7) and applied to the controlled circuits (9) to (11) in the analog IC (8). . However, in the method of FIG. 2, one control line is required every time one control is performed, and the number of pins of the microcomputer or IC increases and the wiring becomes complicated.

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

According to the method of 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 there is a D / A converter having a large number of elements. Therefore, there has been a demand for a transmission method in which the number of signal lines is small and D / A conversion processing is performed on the microcomputer side.

[0007]

The present invention has been made in view of the above points, and an analog circuit using a microcomputer for controlling a plurality of controlled circuits in an analog IC by a control voltage from the microcomputer. A first D / A converter that time-divisionally generates a control voltage that changes to a plurality of levels, and the control voltage is generated at the same timing as the time-division timing of the control voltage. Second generation of switching signal indicating type
A second D / A converter, a plurality of DC hold circuits to which the control voltage of the first D / A converter is applied, and a DC voltage held in the plurality of controlled circuits, and a plurality of comparators; It has a comparison and switching control circuit that determines the level of the switching signal from the / A converter and operates a desired DC holding circuit among the plurality of DC holding circuits.

[0008]

According to the present invention, the control voltage is transmitted in a time division manner, and the switching signal indicating the type of each time division control voltage is divided according to the level. Signals can be transmitted to the IC.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a controller of the present invention.
(16) is a first D / A converter for time-divisionally generating a control voltage for a TV signal that changes to a plurality of levels, (17)
Is a second D / A converter that is generated at the same timing as the time division timing of the control voltage and the level of which generates a switching signal indicating the type of the control voltage. (18) to (20) are the first D / A converters. First to third D to which the control voltage of the A converter (16) is applied and to which the DC voltage held in the first to third controlled circuits (9) to (11) is applied
The C hold circuit (21) has a plurality of comparators, determines the level of the switching signal from the second D / A converter (17), and selects a desired DC hold circuit among the plurality of DC hold circuits. And (22) and (23) are for controlling the first and second D
A / A converters (16) and (17) are filters for removing noise in output signals.

FIG. 4A shows a second D / A converter (1
7) shows the output signal level of FIG. 7B, and FIG.
The output signal level of the A converter (16) is shown.
The abscissas of FIGS. 4A and 4B represent time, and as time passes, control of the taint, color, and contrast, which is control for TV signals, is performed. First, the taint will be described. The level of the taint switching signal generated from the second D / A converter (17) is 0.5 in FIG.
It is set between V and 1.0V, and can take any value in this range. In this case, it is 0.75V. 0.75
During the period in which the V taint switching signal is generated, the first
A control voltage of 2V is generated from the D / A converter (16) and is applied to the first to third DC hold circuits (18) to (20) in the analog IC (8). On the other hand, the comparison and switching control circuit (21) determines from the level of the switching signal of 0.75 V that the incoming control voltage is for taint, and the first to third DC hold circuits (18) to Of (20), only the first DC 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, it is possible to control the taint. By the way, since the apparatus of FIG. 1 performs a plurality of controls in time series, the first DC hold circuit (1
Before 8) holds the control voltage of 2V, another control (for example, brightness) is generally performed. Therefore, it is conceivable that the previous control voltage cannot be immediately changed to the next control voltage due to the influence of the time constant of the filter (22), for example, when the level of the control voltage is greatly different from that of the previous control voltage. Therefore, in the present invention, the period between the two time-divided controls is set to the period during which the first to third DC hold circuits (18) to (20) are all prohibited from holding the input voltage. During this period, the first D /
Since the control voltage next to the A converter (16) is being applied, the voltage at the pin of the analog IC (8) has completely shifted to the next control voltage, and it is possible to take in the control voltage in a stable manner. Become. In the taint example, the control voltage of 0.25V is generated from the second D / A converter (17) before the control voltage of 0.75V is generated as shown in FIG. When the control voltage of 0.25V is applied to the comparison and switching control circuit (21), the control circuit (21) will
To inhibit the input capturing operation of the third DC hold circuits (18) to (20).

FIG. 5 shows a specific circuit diagram of the comparison and switching control circuit (21) shown in FIG. 1. For example, FIG.
In the taint period of (a), it is assumed that a switching signal of 0.75V is applied to the input terminal (24). 1st to 4th
Reference power source (29) for the comparators (25) to (28)
The values of (32) to (32) are set to 0.5V, 1V, 1.5V and 2.0V. Therefore, only the output of the first comparator (25) becomes the “H” level, and the outputs of the other comparators all become the “L” level. Therefore, the level of the output terminal (33) becomes "H" level, and the "H" level
Only during the level period, the first DC hold circuit (1
The switch (34) of 8) is closed. That is, the first and second
Comparators (25) and (26), inverter (3
5) and the AND gate (36) form a window comparator, and detect the input voltage between 0.5V and 1.0V as "H" level.

When a switching signal of 0.25 V is applied to the input terminal (24), it is not included in either range of the two window comparators of FIG. 5, so that the levels of the output terminals (33) and (37) are the same. Are both "L" level. Therefore, the first to third DC hold circuits (18) to (20) in FIG. 1 stop the fetch operation. Next, it is assumed that the color control period shown in FIG.
Then, the switching signal of 1.25V is input to the input terminal (2
4), the output terminals (33) and (37) are
It becomes the "L" level. Next, when the switching signal of 1.75V is applied to the input terminal (24), only the output terminal (37) becomes the “H” level, and the second DC hold circuit (19) of FIG. 3) The control voltage of 3V shown in FIG.

Therefore, the color control voltage can be applied to the second controlled circuit (10). Thereafter, similarly, FIG.
The contrast of (a) can also be applied to the third controlled circuit (11) of FIG.

[0015]

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 constructed with a small number of elements.

[Brief description of drawings]

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

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

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

FIG. 4 is a waveform diagram for use in explaining FIG.

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

[Description of Reference Signs] (1) Microcomputer (8) Analog IC (16) First D / A converter (17) Second D / A converter (18) First DC hold circuit (19) First DC hold circuit (20) First DC Hold circuit (21) Comparison and switching control circuit

Claims (2)

[Claims] 1. A control device for an analog circuit using a microcomputer for controlling a plurality of controlled circuits in an analog IC by a control voltage from a microcomputer, wherein the control voltage changing to a plurality of levels is time-divided. A first D / A converter generated at the same time, a second D / A converter generated at the same timing as the time division timing of the control voltage, and a level of which generates a switching signal indicating the type of the control voltage; / A converter control voltage is applied, a plurality of DC hold circuits for applying the DC voltage held in the plurality of controlled circuits, and a plurality of comparators, the level of the switching signal from the second D / A converter To determine the plurality of DC
A comparison and switching control circuit for operating a desired DC hold circuit among the hold circuits, the first and second D / A converters are built in the microcomputer, and the plurality of DC hold circuits and the comparison and The switching control circuit is the analog IC
An analog circuit control device using a microcomputer, which is characterized by being built into the. 2. Inserting a signal of a level that inhibits the DC hold circuit from holding an input voltage during a time division interval of a time division switching signal generated from a second D / A converter. An analog circuit control device using the microcomputer according to claim 1.