JPH0441336Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an automatic output switching device that compares two AC signals and automatically selects and outputs the larger signal.

FIG. 1 is a block diagram of a conventional automatic output switching device of this type. In FIG. 1, reference numeral 1 denotes a buffer amplifier to which a first channel or second channel signal is input.

The output of this buffer amplifier 1 is sent to an AC-DC converter 2 to obtain a DC voltage.
The output of the AC-DC converter 2 is applied to a comparator 3, and a reference voltage Vref from a reference voltage generator 4 is also applied to the comparator 3.
This reference voltage and the output voltage of the AC-DC converter 2 are compared by a comparator 3.

The output of the comparator 3 is applied to a drive circuit 5. This drive circuit 5 drives the switching element 6.

On the other hand, 7 is a contact portion of the switching element 6, which switches between the first channel signal and the second channel signal and inputs the signal to the buffer amplifier 1. It is connected to the output terminal 8 of this contact portion 7.

Next, the operation of the automatic output switching device shown in FIG. 1 will be explained.

Normally, when adjusting and measuring the distortion rate of a stereo signal from a tuner, etc., on a production line, the stereo signal is time-divided into an L channel signal and an R channel signal.

Therefore, since only one distortion meter is used, automatic switching is performed to input only the output signal to the distortion meter.

Here, in FIG. 1, the buffer amplifier 1 is a buffer amplifier with high input impedance so that the signal input to the buffer amplifier 1 is not affected, and the output of the buffer amplifier 1 is converted into a DC voltage by an AC-DC converter 2, and compared. output to device 3.

The comparator 3 compares this DC voltage with the reference voltage Vref from the reference voltage generator 4. At this time,
If the DC voltage of the first channel signal is less than this reference voltage Vref, a signal is output from the comparator 3 to the drive circuit 5.

As a result, the switching element 6 operates, the contact portion 7 switches, and the second channel signal is output from the output terminal 8.

Since the conventional automatic output switching circuit is configured as described above, a signal lower than the reference voltage Vref is automatically switched. For this reason, when receiving AM broadcasting with a small output signal, a malfunction or muting caused by a product with poor separation or external noise may result in switching to the second channel. Therefore, it is difficult to set the reference voltage, and the set value must be reset for each product.

This invention was made to eliminate the above-mentioned drawbacks of the conventional methods. By comparing one input signal and detecting and comparing the gain difference between two signals, automatic output switching can be performed safely without malfunction. The purpose is to provide equipment.

Hereinafter, embodiments of the automatic output switching device of this invention will be described based on the drawings.

FIG. 2 is a block diagram showing the configuration of one embodiment. In FIG. 2, T1 and T2 are input terminals, and the first channel signal is input to the input terminal T1, and the second channel signal is input to the input terminal T2.

Input terminals T1 and T2 are connected to input terminals of buffer amplifiers 9a and 9b, respectively, and
Contacts 191 and 192 of the contact portion 19 of the switching element 18
It is connected to the. Contact portion 19 is connected to output terminal 20 .

The output end of the buffer amplifier 9a is connected to the input end of the AC-DC converter 10a, and similarly, the output end of the buffer amplifier 9b is connected to the input end of the AC-DC converter 10b.

The output of the AC-DC converter 10a is supplied to one input terminal of the comparator 11 and the differential amplifier 12, and the output of the AC-DC converter 10b is supplied to the other input terminal of the differential amplifier 12. supply is becoming available.

The output of the differential amplifier 12 is supplied to a comparator 14 via an absolute value amplifier 13.
This absolute value amplifier 13 is for converting the gain difference (DC voltage) of the differential amplifier 12 into an absolute value.

On the other hand, 15 is a reference voltage generator, which generates two reference voltages Vref1 and Vref2. The reference voltage Vref1 is supplied to the comparator 11, and the reference voltage Vref2 is supplied to the comparator 14.

The output of comparator 11 and the output of comparator 14 are
The signal is sent to an AND circuit 16. The output of this AND circuit 16 is sent to a drive circuit 17. The drive circuit 17 is for driving the switching element 18.

Next, the operation of the automatic output switching device of this invention constructed as above will be explained.

The first channel signal and the second channel signal are inputted to buffer amplifiers 9a and 9b with high input impedance through input terminals T1 and T2, respectively, and are further applied to AC-DC converters 10a and 10b to be converted to DC and DC A voltage appears at the output of the AC-DC converter 10a, 10b.

The DC voltage converted into DC by the AC-DC converter 10a is applied to the comparator 11 and the differential amplifier 12. Further, the DC voltage converted into DC by the AC-DC converter 10b is output to the differential amplifier 12.

In the comparator 11, an AC-DC converter 10a
i.e. the DC of the first channel signal
The converted DC voltage is compared with the reference voltage Vref1 from the reference voltage generator 15. As a result of this comparison, AC
- When the output voltage of the DC converter 10a is lower than the reference voltage Vref1, the output of the comparator 11 is
sent to.

On the other hand, in the differential amplifier 12, the AC-DC converter 1
The output voltages of 0a and 10b, that is, the DC converted DC of the first channel signal and the second channel signal
Detect voltage gain difference. Here, if the DC voltage of the first channel signal is greater than the DC voltage of the second channel signal, the output of the differential amplifier 12 will be positive.
However, in the opposite case to the above, the output of the differential amplifier 12 becomes a negative DC voltage.

The output voltage of this differential amplifier 12 is applied to an absolute value amplifier 13. As a result, even if the DC voltage of the second channel signal becomes larger than the DC voltage of the first channel signal and the output voltage of the differential amplifier 12 becomes a negative DC voltage, the absolute value amplifier 13 This results in a positive DC voltage (or negative DC voltage).

The output voltage of this absolute value amplifier 13 is
sent to. The comparator 14 uses the output voltage of this absolute value amplifier and the reference voltage from the reference voltage generator 15.
Compared with Vref2, the output voltage of the absolute value amplifier 13,
That is, when the DC voltage between the first channel signal and the second channel signal exceeds the set gain difference,
The signal is output from the comparator 14 and sent to the AND circuit 16.

In this AND circuit 16, comparators 11 and 1
4, and when the input level of the first channel signal is below the set level and the gain difference between the second channel signal and the second channel signal is above the set level, output from the AND circuit 16. is sent to the drive circuit 17. Based on this output, the drive circuit 17 drives the switching element 18, its contact portion 19 is switched, and the second channel signal is outputted to the output terminal 20.

In the above embodiment, a relay is used as the switching element 18 and the contact part 19, but if a semiconductor switch is used, the drive circuit 17 will be simpler and the space will be reduced.

Further, in the above embodiment, a large output is outputted, but by changing the input terminals and reference voltages of the comparators 11 and 14, it is possible to easily output a small output. I can do it.

As described above, according to the automatic output switching device of this invention, the first and second comparators determine that the input first channel signal is equal to or lower than the set level and is different from the first and second channel signals. Since the configuration is configured so that the output is switched only when the gain difference exceeds the set level, or vice versa, the first comparator operates even with an AM received signal with a low output level, but the second comparator The device does not operate and the output does not change.

Furthermore, even during the muting operation, it does not change due to the above reasons, and as for external noise, the same external noise is output from both the first channel and the second channel, so the second comparator does not operate, and in this case as well. The output does not change, and it can operate stably without malfunction.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional automatic output switching device, and FIG. 2 is a block diagram of an automatic output switching device of this invention. T1, T2...Input terminal, 9a, 9b...Buffer amplifier, 10a, 10b...AC-DC converter, 11, 14...Comparator, 12...Differential amplifier, 13...Absolute value amplifier, 15... ...Reference voltage generator, 16...AND circuit, 17...Drive circuit,
18...Switching element, 19...Contact portion, 20...Output terminal.

Claims (1)

[Scope of utility model registration request] first and second AC-DC converters that exchange first and second AC input signals to DC input signals, respectively;
a first comparator that compares the output voltage of the AC-DC converter with a first reference voltage;
- A differential amplifier that detects the difference in voltage between the outputs of the DC converter, an absolute value amplifier that converts the output of this differential amplifier into an absolute value, and the absolute value output from this absolute value amplifier and a second reference voltage. a second comparator for comparing the outputs of the first and second comparators; an AND circuit for taking the AND of the outputs of the first and second comparators; An automatic output switching device consisting of a switching element that switches and outputs an AC input signal.