JPH0611655Y2 - Signal switching circuit - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application The present invention relates to an input / output signal switching circuit of an electronic device,
In particular, the present invention relates to a signal switching circuit suitable for switching an input signal of an amplifier used in audio equipment.

(B) Conventional Technology Conventionally, in many cases, input signal switching circuits of amplifiers of electronic devices, particularly audio devices, switch many input signals by controlling them with a microcomputer.

FIG. 5 is a connection diagram of an input signal switching circuit of a general amplifier. The input signal switching circuit having a built-in equalizer / amplifier switches between the input of audio signals such as CD and TAPE and the video input signal of VIDEO to select.

FIG. 1 is a block diagram in which the microcomputer 1 controls the input signal switching circuit 11 to select various input signals and output a sound signal from a speaker 14 via an audio amplifier 13.

The microcomputer 1 is a CPU 2 that performs calculation and judgment
A ROM 3 for storing a program, a RAM 4 for storing calculation data and external information, and a clock generator 5 for generating a reference signal. Further, there are an input port 6 for receiving an input signal from the outside and an output port 7 for outputting an output signal to the outside.

The microcomputer 1 is supplied with power from the microcomputer power supply 9 to operate the microcomputer.

A key operation unit 8 having a keyboard is connected to the input port 6, and various information from the outside is sent from the key operation unit 8 to the input port 6 of the microcomputer 1.

The output port 7 has a switching circuit power source 10 and an input signal switching circuit.
11 is connected.

The input signal is applied to the input terminal 12, and the input signal switching circuit 11
It is selected and switched with.

The switching timing of the signal switched by the input signal switching circuit 11 is the timing of the power supply control signal shown in FIG.

The power supply control signal (a) is controlled by the microcomputer 1 and supplied to the switching circuit power supply 10 via the output port 7. The switching circuit power supply 10 operates from the time when the power supply control signal (a) is applied, and gradually rises to the rated voltage as shown in FIG. 4 (b). This rise time depends on the switching circuit power supply 10
Circuit constant (time constant) and power capacity.

On the other hand, the microcomputer 1 transfers the data for the switch selector to the input signal switching circuit 11 via the output port 7.

During the transitional period in which the switching circuit power supply 10 does not reach the rated voltage sufficiently, the input signal switching circuit 11 does not operate normally even when the switch selector data is transferred. Therefore, in consideration of circuit variations, the switch / selector data is transferred to the input signal switching circuit 11 after the switching circuit power supply 10 reaches the rated voltage sufficiently. That is, about 500 ms after the power supply control signal (a) is sent to the switching circuit power supply 10, the switch selector data is transferred to the input signal switching circuit 11. FIG. 4 (c) shows that the switch / selector data is transferred with a delay of about 500 ms. At this point, the operation of the switching circuit power supply 10 has a sufficiently stable rated voltage value as shown in FIG. 4 (b), so that the switching operation of the input signal switching circuit 11 operates properly and a correct input signal is obtained. Is selected and the desired audio signal is output from the speaker 14.

(C) Problems to be solved by the device However, the conventional signal switching circuit described above has a delay of about 500 ms until the switching circuit power supply reaches the rated voltage value sufficiently, and the data for the switch selector is Is supplied to the input signal switching circuit, the switching operation of the input signal switching circuit operates randomly between the time when the power source for the switching circuit actually reaches the rated voltage and the time when the data for the switch selector is transferred. Becomes unstable.

A switch circuit that is complicatedly combined as shown in FIG.
When connected in a loop through the EQ amplifier, there is a problem that oscillation occurs in the input signal switching circuit.

For example, when S7 and S8 of the EQ switch unit of FIG. 5 are turned on at the same time, a loop circuit is formed via the EQ amplifier and abnormal oscillation occurs.

Further, there is a drawback that this oscillation signal may be applied to the amplifier of the next stage from the output terminal of "LINE ONT" to cause destruction of the circuit element.

The present invention has been made in view of the above point, and at the same time that the power supply control signal is supplied to the power supply for the switching circuit, the data for the switch selector is repeatedly transferred to the input signal switching circuit. The purpose is to ensure proper switch selector operation.

(D) Means for Solving the Problem A signal switching circuit according to the present invention is a signal switching circuit in which a power circuit for supplying power to the signal switching circuit and a plurality of electronic switches are combined. ,
It is configured to repeatedly transfer the switch / selector data to the signal switching circuit until the switching circuit power supply reaches the rated voltage sufficiently in consideration of circuit variations.

(E) Action The power supply for the switching circuit starts operating in response to the power supply control signal transferred from the microcomputer. Since the power supply voltage is low at the start of this operation and gradually rises to the rated power supply voltage, the signal switching circuit operated by the supply of this power supply operates with a delay.

When the signal switching circuit starts operation with a delay, the switch selector data is transferred, and the microcomputer repeats this switch selector data after the power supply control signal is output so that the normal signal switching circuit operates. Forward.

By repeating the transfer in this manner, it is possible to properly switch the signal switching circuit even if there are variations in the circuit and the like, and it is possible to prevent problems such as abnormal oscillation.

(F) Embodiment An embodiment of the signal switching circuit according to the present invention is shown in FIGS.
It will be described with reference to the drawings.

Since the operation of the input signal switching circuit 11 controlled by the microcomputer 1 shown in FIG. 1 is the same as that of the conventional example, the operation of this signal switching circuit will be described based on the flowchart of FIG.

The POWER key is operated from the key operation unit 8 shown in FIG. 1, and the key is turned from OFF to ON (Y in step S2).
ES), the CPU 2 of the microcomputer 1 sets the POWER flag stored in the RAM 4 to "0".
To "1". (Step S3).

Now, this POWER flag is "1", that is, step
Since S4 is ON, set the required parameters for the data output timer for the switch / selector (step S
Five). And the output port 7 of the microcomputer 1
Then, the power supply control signal for controlling the switching circuit power supply 10 is set to Hi, and the switching circuit power supply 10 is turned on (step S6).

On the other hand, if the POWER flag in step S4 is "0", that is, if step S4 is off, the power supply control signal is set to Lo and the switching circuit power supply 10 is turned off (step S7).

Since the parameter is set in the timer in this state (YES in step S8), the CPU 2 creates data to be supplied to the input signal switching circuit 11 from the data stored in the RAM 4 of the microcomputer 1, and the output port 7 The switch selector data is output to the input signal switching circuit 11 via (step S9).

Simultaneously with the above data transfer, the count of the switch / selector data output timer starts (step S1).
0).

When the timer does not reach the preset 500 ms in step S11, the execution of steps S9, S10, and S11 is further repeated.
Then, the timer stops (step S12).

FIG. 3 shows the control timing of the transitional state after the switching circuit power supply 10 is started. Figure 3 (a), (b)
Is the same as in FIGS. 4A and 4B, but the switch / selector data transfer signal in FIG. 3C is controlled by the output timer and repeatedly transferred.

In the example of FIG. 3 (c), the switching circuit power supply 10 reaches almost the rated voltage value at the time of S, the input signal switching circuit 11 operates, and the switch selector data from the microcomputer 1 is transferred. The normal switching operation is performed and the stable state is reached. That is, the input signal switching circuit 11 does not operate and the unstable state of the input signal switching circuit 11 does not occur because it operates with the shortest rise time and the power supply voltage is low before the operation. Therefore, normal switching can be performed without a problem such as abnormal oscillation.

(G) Effect of the Invention The signal switching circuit according to the invention has an effect that there is no unstable state when the power is turned on, and stable operation can always be performed. That is, even if the signal switching circuit of the switch circuits connected in a complicated manner is formed, there is an effect that a defect such as abnormal oscillation does not occur.

Moreover, it has excellent features such as easy implementation because it can be constructed at low cost.

[Brief description of drawings]

1 to 3 show an embodiment of a signal switching circuit according to the present invention. FIG. 1 is a block diagram, FIG. 2 is a flow chart diagram, and FIG. 3 is a control timing diagram at power-on.
FIG. 4 is a control timing chart at the time of starting the power supply of the conventional example, and FIG.
The figure is a connection diagram of a conventional input signal switching circuit. Explanation of main numbers 1: Microcomputer 2: CPU 6: Input port 7: Output port 8: Key operation device 10: Switching circuit power supply 11: Input signal switching circuit

Claims (1)

[Scope of utility model registration request] 1. A signal switching circuit comprising a combination of a power supply circuit for supplying power to a signal switching circuit and a plurality of electronic switches, wherein the switching circuit power supply takes into consideration circuit variations after the operation of the power supply circuit. Time to fully reach the rated voltage,
A signal switching circuit characterized in that the switch selector data is repeatedly transferred to the switching circuit.