JPH0357646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a speaker drive system, more specifically, in a keyboard-operated PLL synthesizer receiver, etc., the audio speaker provides a confirmation sound for keyboard operations or various switch operations. Regarding the method for

FIGS. 1 and 2 show typical conventional systems of this type. In FIG. 1, a sine wave or square wave operation check signal is given to the audio signal path, and 10
12 is an audio signal input, 12 is an operation confirmation signal input, 14 is an audio amplifier, 16 is a DC blocking capacitor, and 18 is a speaker. In the system shown in FIG. 2, a positive feedback network 20 and a switch 22 are connected between the input and output of the audio amplifier 14.
In this method, the switch 22 is controlled by an operation confirmation signal.

In any of these conventional methods, the operation confirmation sound is only given when the audio amplifier 14 is operating, and therefore, it is necessary to save power consumption when muting or squelching the receiver, for example. If the audio amplifier stops operating, the speaker will no longer be able to provide operation confirmation sound.

The present invention solves these drawbacks of the conventional system, and even when the audio amplifier is in a non-operational state, it is possible to generate an operation confirmation audio signal from the speaker, and it can do so with high efficiency in terms of power consumption. The purpose is to make it possible.

FIG. 3 shows an embodiment of the invention, in which numeral 30 is an audio amplifier having an audio signal input 32, which input is adapted to receive the detection output of, for example, a keyboard-operated radio receiver. Amplifier 30 is also provided with an amplifier operation stop signal via input 34. This is a signal from, for example, a mute circuit or a squelch circuit, and when this signal is applied, the bias of the amplifier 30 and, for example, a transistor in a power amplifier stage is cut off, or the power supply to the amplifier itself is stopped. . Amplifier 30 is provided with a positive supply voltage at 36 and grounded at 38.

According to the present invention, even if the amplifier 30 is inactive due to the input 34 receiving an amplifier operation stop signal, the speaker 40 can provide operation sounds from, for example, a keyboard or a switch. For this purpose, in FIG.
is provided, its emitter is connected to the positive power supply 36, its base is connected to receive the operation confirmation signal of the input 46 via a resistor 44, and its collector is connected via a protection diode 48 and a second resistor 50. It is connected to a speaker 40 whose one end is grounded.

The audio signal at input 32 of amplifier 30 is typically amplified by amplifier 30 and drives speaker 40 via capacitor 52 . For example, when a rectangular wave or sine wave operation confirmation signal is given by a keyboard operation, the transistor 42 is energized in switching mode, thereby causing an intermittent current to flow through the speaker 40, thereby giving an operation confirmation sound from the speaker 40. . This field transistor 42
The transistor 42 is intermittently turned on at the ground level or region of the operation confirmation signal of the input 46 applied to the base of the transistor 42 . Since the transistor 42 operates in such an intermittent mode, it has good power efficiency. The operation confirmation signal tone is generated even if the amplifier is not operating. Diode 48 is not necessarily required in this circuit.

FIG. 4 shows that the transistor 42 of the embodiment of FIG.
In contrast to the PNP type, an example is shown in which the NPN type is used. Corresponding elements are indicated by the same numbers. Since the transistor 42 is intermittently turned on in the region of the operation confirmation signal, a current flows from the B+ line 36 to the speaker 40, the resistor 50, the diode 48, and the transistor 42 to provide the operation confirmation signal sound.

[Brief explanation of drawings]

1 and 2 are circuit diagrams of a conventional speaker driving system, and FIGS. 3 and 4 are circuit diagrams of an embodiment of the present invention.

Claims (1)

[Claims] 1 It has a speaker driven by the output of an audio amplifier that can be rendered inactive by an operation stop signal, and the signal output from the audio amplifier is controlled by keyboard operation.
In the PLL synthesizer receiver, the emitter-collector path of the transistor is connected between the power supply and ground via the drive coil of the speaker, and an operation confirmation signal generated by the operation of the keyboard or switches is connected to the base of the transistor. A speaker driving method characterized in that the transistor is operated in a switching mode by applying an electric current to the speaker, and an intermittent current corresponding to the operation confirmation signal is caused to flow through the speaker, so that an operation confirmation sound is given from the speaker.