JPH0538440Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a switching circuit for an amplifier equipped with a recording output terminal.

[Conventional technology]

In conventional circuits, when the signal input to the digital audio interface demodulation circuit is converted to analog and recorded as an analog signal, in order to prevent oscillation due to signal loops, the digital input selector is switched to select a specific mode (such as DAT). ) analog recording terminal output was blocked by a switching circuit.

[Problem that the invention attempts to solve]

However, in conventional circuits, even if digital audio interface data is not input to the digital input, switching the digital input selector switches the switch control power supply and switches the switching circuit of the recording output terminal, which causes switching noise. Since noise may jump into the power supply or signal line, circuits with a high-amplification audio amplifier at the rear stage have had significant restrictions on noise prevention.

[Means for solving problems]

The circuit of the present invention is a circuit constructed to solve the above-mentioned problems, and includes a detection means that integrates and detects the presence or absence of digital audio interface data input, and a detection means that cuts off the power when there is no data, and If there is a switching circuit that turns on the power and a switching circuit that cuts off the signal at the output of the switching circuit, it is a recording prohibition circuit.

〔Example〕

FIG. 1 shows a block diagram of an embodiment of the present invention. Input from CD, DAT which is the input of CD player to input terminal 1 of digital signal,
A DBS signal input, which is a DBS input, is connected, selected with the selector 2 of the digital input, demodulated with the demodulation circuit 5, and converted to D/A with the digital/analog converter 6.
A conversion is performed to obtain analog output 7. On the other hand, the analog output 7 is selected by an input from an analog input terminal 8 and an analog input selector 9, and is amplified by an audio amplifier 10.
A digital signal is input to the input terminal 1, selected by the selector 2, integrated by the integrating circuit 3, the serial data is smoothed, and the output voltage A becomes "H" and SW1
becomes conductive, and +B voltage appears at the DAT position of SW3.

Conversely, when no data is input to the input terminal selected by the selector 2 of the digital input, the output of the integrating circuit 3 becomes "L", the switch circuit SW1 is cut off, and the +B voltage does not appear at SW3.

The recording inhibit circuit SW2 is cut off when the +B voltage is applied, and becomes conductive when no voltage is applied.

In other words, with Digital Input Selector 2
The recording prohibition circuit SW2 cuts off the recording output signal only when the DAT is selected and data is input from the digital audio interface to the digital input terminal of the DAT.

FIG. 2 shows a specific embodiment of the recording prohibition circuit. The digital data output of the selector 2 of the digital input is integrated by the resistor R ₁ and the capacitor C ₁ , passes through the resistor R ₂ , makes the transistor T ₁ of the switch circuit SW ₁ conductive, passes through the resistor R3, makes the transistor T ₂ conductive, and connects the power supply +B. Turn ON and OFF. The power +B that passes through switch circuit SW ₁ is linked to selector 2 of the digital input, and is connected to the recording prohibition circuit through switch SW ₃ , which is connected in the case of DAT.
Turn on SW ₂ . Transistor T ₃ conducts and resistor
Transistor _{T4 is turned on through an integrating circuit consisting of a parallel circuit of R4, capacitor C2, and resistor R5, and the collector voltage of transistor T4 is completely inverted .} Therefore, the transistor _T5 is turned off by the resistor _R7 through the integrating circuit of the resistor _R6 and the capacitor _C3 , and the recording output to the selector 4 is prohibited.

On the other hand, when there is no signal input from the DAT input of input terminal 1, the charge of the integrating circuit C ₁ is transferred to the resistor R ₂ ,
Discharge through _R8 . The base charge of the transistor _T1 becomes 0, transistors _T1 and _T2 are turned off, and the +B voltage is no longer applied to the switch _S3 .
Transistor _T3 is turned off, the charge in capacitor _C2 is discharged through resistor _R5 , and transistor _T4 is turned off.
The capacitor _C3 is charged through the resistors _R9 and _R6 , and the transistor _T5 becomes conductive. Therefore, the output signal is connected to the recording output selector 4, and recording becomes possible.

Conventionally, it was turned on and off with a switch, so when the digital simple selector 2 was switched, the voltage change was amplified by the audio amplifier 10 and became noise. However, as shown in the above embodiment, when the digital input selector 2 is switched, no charge is applied to the switch _S3 , so no noise is generated, and the presence of the digital input signal is detected and delayed by the integrating circuit to turn it on.・Since it is automatically turned off, noise generation can be prevented.

[Effect of idea]

As mentioned above, when switching the digital input selector switch, the probability that a digital input signal is being input is small, and even if there is an input signal, it is delayed by the integrating circuit and recording output is prohibited, thereby preventing switching noise from occurring. The effect is great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram of the main parts. 1...Input terminal, 2...Selector, 3...Integrator circuit, 4...Selector, 5...Demodulation circuit, 6
...Digital-to-analog converter, 7...Analog output, 8...Analog input terminal, 9...Analog input selector, 10...Audio amplifier.

Claims (1)

[Scope of utility model registration request] In an amplifier equipped with a digital audio interface demodulation circuit that switches the digital input selector and converts the input digital signal to an analog signal for analog playback, it integrates the digital data to the amplifier input interface and detects the presence or absence of the signal. and a switching circuit for opening and closing the digital recording output. A switching circuit characterized by: