JPH0129853Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an audio device that displays the output level of an amplifier using a display having a plurality of light emitting diodes, and is intended to prevent erroneous display on the display when the power is cut off.

Conventionally, in one example of this type of audio device, as shown in FIG. The power is applied to an amplifier 2 via a power filter circuit 1 consisting of a filter coil La and a filter capacitor Ca, and the input signal at the signal input terminal In is amplified by the amplifier 2 and output to the signal output terminal Ot.

Further, the above-mentioned power supply voltage is applied to the anodes of the plurality of light emitting diodes Da, Db, ..., Dn through the plurality of resistors Ra, Rb, ..., Rn through the power supply filter circuit 1, and The cathodes of the light emitting diodes Da to Dn are connected to the light emitting diode drive circuit 3, and the respective resistors Ra to Rn
And each light emitting diode Da~Dn displays 4
is formed. Note that a power supply voltage is also applied to the drive circuit 3 via the power supply filter circuit 1 .

Then, the output signal of amplifier 2 is transmitted to the signal output terminal
Output to Ot and light emitting diode drive circuit 3,
By the operation of the drive circuit 3, the cathode potential of each light emitting diode Da to Dn selectively changes from high level to low level according to the output level of the amplifier 2, that is, the level of the output signal, and the level of the output signal of the amplifier 2 changes. According to each light emitting diode Da~Dn
selectively lights up, and the level of the output signal of the amplifier 2 is displayed on the display 4.

However, depending on the power supply voltage, the filter capacitor
Because Ca is charged, when the power switch SWa is opened and the power is cut off, even though the power supply voltage has been cut off, due to the charge in the capacitor Ca, when the power switch SWa is opened, the During this period, the amplifier 2 and the drive circuit 3 continue to be driven, and each light emitting diode Da~
Voltage continues to be applied to the anode of Dn.

When the power switch SWa is opened, the DC level of the amplifier 2 begins to gradually decrease, and the shock noise from the previous stage circuit is input to the signal input terminal In, causing the level of the output signal of the amplifier 2 to fluctuate, causing each light to emit light. There is a drawback that the diodes Da to Dn are erroneously lit and the display 4 displays an erroneous display.

This invention was made with the above points in mind, and includes a power filter circuit having a filter capacitor, an amplifier to which a DC power supply voltage is applied via the filter circuit, and a plurality of light emitting diodes. An acoustic device comprising: a display; and a light-emitting diode drive circuit that controls cathode potential of each of the light-emitting diodes according to the output level of the amplifier, wherein the display displays the output level of the amplifier; A power switch applies a first DC power supply voltage of a first power supply terminal to the anode of the diode, and the first power supply voltage is applied to the second power supply terminal in conjunction with opening and closing of the power switch. The acoustic device is provided with a relay that opens and closes a connected contact switch and applies a second DC power supply voltage of the second power supply terminal to the amplifier via the filter circuit.

Therefore, the first power supply voltage that does not go through the power filter circuit is applied to the anode of each light emitting diode of the display, so when the power switch is opened, no voltage is instantly applied to the anode of each light emitting diode. , even if the amplifier continues to be driven by the charged charge of the filter capacitor in the power filter circuit when the power switch is shut off due to an open circuit, each light emitting diode will not light up, preventing incorrect display on the display when the power is shut off. be done.

Next, a second embodiment of the acoustic device of this invention will be described.
This will be explained with reference to the drawings below.

First, one embodiment will be described with reference to FIG.

In Figure 2, the same symbols as in Figure 1 indicate the same things, and instead of the power supply terminal (+Ba) in Figure 1, there is a first power supply terminal (+Bb) to which the first DC power supply voltage is applied, and a DC A second power supply terminal (+Bc) to which a second power supply voltage of is applied is provided, a power switch SWa is connected to the first power supply terminal (+Bb), and by closing the power switch SWa,
A first power supply voltage via the power switch SWa is applied to the anodes of each of the light emitting diodes Da to Dn of the display 4, and is also applied to the series circuit of the relay coil Lb and current limiting resistor Rx of the relay 5, Relay coil Lb is driven by the first power supply voltage, a magnetic field is generated, and contact switch of relay 5 is activated.
SWb is closed in conjunction with the power switch SWa, and due to the closing of the contact switch SWb, the second power supply voltage of the second power supply terminal (+Bc) is applied to the contact switch SWb,
The power is applied to an amplifier 2 and a light emitting diode drive circuit 3 via a power filter circuit 1 . In addition, a surge absorption diode Dx is connected in parallel to the relay coil Lb.
is provided.

Therefore, each light emitting diode Da of the display 4
The first power supply voltage that does not pass through the power filter circuit 1 is applied to the anode of ~Dn, and the power switch is turned on.
When SWa is opened, the first power supply voltage applied to the anodes of the light emitting diodes Da to Dn and the relay coil Lb is instantaneously cut off, and no voltage is applied to the anodes of the light emitting diodes Da to Dn.

On the other hand, due to the interruption of the first power supply voltage, the relay coil
When the drive of Lb is stopped, the contact switch SWb is opened, the second power supply voltage applied to the amplifier 2 and the light emitting diode drive circuit 3 is cut off, and the voltage due to the charge in the filter capacitor Cb becomes
The voltage is applied to the amplifier 2 and the drive circuit 3, and the amplifier 2 and the drive circuit 3 are driven for a while after the contact switch SWb is opened.

However, as mentioned above, each light emitting diode Da~
Since no voltage is applied to the anode of Dn, even if the output signal level of amplifier 2 fluctuates due to fluctuations in the DC level of amplifier 2 or shock noise input from the previous circuit to the signal input terminal In, each light emission Diodes Da~Dn do not light up and the power switch does not turn on.
When the power is cut off by opening SWa, the display 4 will not display an incorrect display.

Next, another embodiment will be described with reference to FIG.

In FIG. 3, the same symbols as in FIG. 2 indicate the same things, and the difference is that the first power supply voltage is applied to the light emitting diode drive circuit 3 via the power switch SWa.

Therefore, when the power switch SWa is opened, the first power supply voltage applied to the anodes of the light emitting diodes Da to Dn, the relay coil Lb, and the drive circuit 3 is instantaneously cut off.
Similarly to the above, the display 4 will not display incorrect information when the power is cut off.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram of a part of a conventional audio device;
3 and 3 are partial wiring diagrams of one embodiment and another embodiment of the acoustic device of this invention, respectively. 1...Power filter circuit, 2...Amplifier, 3...
...Light emitting diode drive circuit, 4...Display device, 5...
...Relay, Da, Db, ..., Dn...Light emitting diode, SWa...Power switch, SWb...Contact switch, +Bb, +Bc...First and second power terminals.

Claims (1)

[Scope of utility model registration request] a power supply filter circuit having a filter capacitor, an amplifier to which a DC power supply voltage is applied via the filter circuit, a display having a plurality of light emitting diodes, and each of the light emitting diodes according to the output level of the amplifier. and a light emitting diode drive circuit that controls a cathode potential of the amplifier, and in which the output level of the amplifier is displayed by the display, a first direct current power supply voltage of a first power supply terminal is applied to the anode of each of the light emitting diodes. The first power supply voltage is applied through the power switch, and in conjunction with the opening and closing of the power switch, a contact switch connected to the second power terminal opens and closes, and the DC voltage of the second power terminal is applied. and a relay for applying a second power supply voltage to the amplifier via the filter circuit.