KR890003492Y1 - Muting circuit - Google Patents

Abstract

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Description

Clamping Complement Circuit of Muting Circuit

1 is a block diagram of a conventional audio muting circuit.

2 is a block diagram of an audio muting circuit having a clamping security circuit according to the present invention.

3 is a waveform diagram of a signal applied to an over-input signal, a tape output end, and a tone input in FIG.

4 is a waveform diagram of a signal applied to an over-input signal, a tape output end, and a tone input in FIG.

The present invention generally relates to an audio muting circuit. In particular, in an acoustic circuit, a clamping complement circuit of a muting circuit for compensating for clipping of a signal when an over input is applied during an AM / FM function selection switching. It is about.

In a typical acoustic circuit, by putting a muting transistor around the tone input, the muting terminal of the circuit is instantaneously muted when the AM / FM function selection is switched, and the volume is maximum (MAX). When over-input is applied through the input terminal in the state, the transistor is automatically conducted even when muting is not performed due to the potential difference of the muting transistor, and the signal is clipped at a voltage higher than the potential difference of the transistor. There was a drawback to the tape output and tone input.

The object of the present invention is to provide a clamping complement circuit for compensating for the disadvantages of the conventional muting circuit in which a signal is clipped by a potential difference of a transistor when an over input is applied as described above.

In the present design, the negative pulse wave passed through the rectifying diode and the condenser maintains a certain negative DC voltage through the constant term and the condenser by using the AC output waveform from the secondary side of the power transformer, and the base of the muting transistor By applying a negative DC voltage to the transistor, the potential difference of the transistor is increased to prevent the signal from being clipped even when any over-input is applied through the input terminal.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 shows a conventional audio muting circuit.

In FIG. 1, the diode D ₁ is a switching diode, and the anode (+) side of the diode D ₁ is connected to the muting terminal.

If a DC (+) voltage is applied during AM / FM function selection switching, a DC (+) voltage through diode (D ₁ ) is applied to the bases of transistors (Q ₁ ) and (Q ₁₀₁ ) via resistor (R ₆ ). Thus, transistors Q ₁ and Q ₁₀₁ are conducted, and emitters of transistors Q ₁ and Q ₁₀₁ are shorted to the selector, i.e., ground, thereby suppressing the signal from being applied to the tone input. To eliminate pop noise. Therefore, the base voltages of the transistors Q ₁ and Q ₁₀₁ always maintain OV except for the function switching.

However, in the state where the volume resistance (R ₂₀₁ ) is maximized, the overvoltage, that is, the base voltage of the transistors (Q ₁ ) and (Q ₁₀₁ ) through the input terminals (L) and (R) is OV, which is -0.7 or more above this potential. When a low potential is applied, transistors Q ₁ and Q ₁₀₁ are automatically conducting, and potentials below -0.7 V are clipped directly to ground, so that signals applied through input terminals L and R are applied. The bottom part of is cut off, and the signal applied to the tape output terminal is also applied in the same signal waveform as the bottom part is cut off.

FIG. 3 shows waveforms of signals applied through the input terminals L and R and signals applied to the tone input and the tape output terminals, respectively.

2 shows an audio muting circuit in which the clamping complement circuit according to the present invention is installed in the circuit of FIG.

The clamping complement circuit according to the present invention is a rectifying diode (D ₃ ) for rectifying the AC output waveform from the secondary side of the power transformer, the diode protection capacitor (C ₅ ) and the negative current through the current diode (D ₃ ) It consists of a capacitor (C ₄ ) and a resistor (R ₅ ) for maintaining a polarized pulse wave at a certain negative DC voltage.

The AC output from the secondary side of the power transformer is rectified into a negative pulse wave through the rectifying diode (D ₃ ) and the diode protection capacitor (C ₅ ), and the negative pulse wave is converted into a capacitor (C ₄ ) and a resistor ( R ₈ ) is maintained at a certain negative DC voltage. It is applied to the sub-base in a polar transistor (Q ₁₎ and (Q ₁₀₁₎ DC voltage via a resistor (R ₇₎ and (R _6), the transistor (Q ₁₎ and the base of (Q ₁₀₁₎ (-) By maintaining the potential, the potential difference of the transistor is increased.

Therefore, in the state where the volume resistance R ₂₀₁ is maximized, even when an over-input, i.e., a low potential of -0.7 V or less is applied through the input terminals L and R, transistors Q ₁ and ( Since the potential difference of Q ₁₀₁ is set large, it is possible to prevent the potential of 0.7 V or less from being clipped.

In addition, there is no fear that the signals applied to the tone input and tape output stages are also creeped by the over input.

In the case where the clapping complementing circuit according to the present invention is installed in the existing circuit, the waveforms of the signals applied through the input terminals L and R and the signals applied to the tone input and the tape output terminals at the time of over-input, respectively. It is as shown to 4th and b.

From the foregoing, the clamping complement circuit of the muting circuit according to the present invention sets the potential difference of the muting transistor to be large, so that over-input is made through the input terminal in a state where the volume is maximum when switching the AM / FM function of the yin-yang circuit. Even when applied, there is an effect that the signal applied to the tape output terminal and the tone input can always be maintained as an sine wave input signal.

Claims (1)

In the audio muting circuit for installing muting transistors around the tone input of the acoustic circuit and for instant muting using the muting terminal of the circuit when the AM / FM function is selected and switched, the AC from the secondary side of the power transformer The rectifying diode D ₃ for rectifying the output waveform, the rectifying diode protective capacitor C ₅ , and the negative pulse wave through the rectifying diode D ₃ and the protective capacitor C ₃ have a constant negative polarity. A cone sensor (C ₄ ) and a resistor (R ₅ ) for maintaining the DC voltage of the muting sensor is applied to the base of the muting transistors (Q ₁ ) and (Q ₁₀₁ ) for the muting By setting the potential difference between the transistors Q ₁ and Q ₁₀₁ to be large, when the over input is applied through the input terminals L and R, the signal applied to the input signal, the tone input and the tape output terminal is clipped. To be Clamping complement circuit of muting circuit specially designed to prevent