JPH0559606B2 - - Google Patents

Description

[Detailed Description of the Invention] Purpose of the Invention (Field of Industrial Application) This invention is a fader VR that adjusts the output balance of each amplifier in a multi-channel amplifier that can be connected to BTL and is used in car stereos, etc.
This is related to the connection structure of.

(Prior Art) Conventionally, the first example of a car stereo amplifier is one with a built-in 4-channel power amplifier. The speakers are now driven by separate power amplifiers. and,
In such an amplifier, the preamplifier section of the circuit configuration is equipped with a master VR that adjusts the output of all speakers simultaneously, and the power amplifier section is equipped with a fader VR that adjusts the output balance of the front and rear speakers as appropriate. .

On the other hand, some of the above amplifiers can increase the output by converting a 4-channel power amplifier into a 2-channel power amplifier through BTL connection, but in this case, the fader VR installed in the power amplifier section is Since it is unnecessary and may interfere with normal amplification operation, it is necessary to disconnect the fader VR from the circuit configuration.
It was pre-installed with auto-detection circuitry that detects BTL connections and disables the fader VR.
And, for the power amplifier which has been converted into 2 channels by BTL connection, AUX installed in advance
A 4-channel power amplifier was constructed by connecting an external 2-channel power amplifier to the output terminal.

In addition, as a second example, in a power amplifier that can drive a total of four speakers by connecting two speakers each to a two-channel power amplifier, it is necessary to connect each power amplifier to adjust the output balance of the front and rear speakers. A high-power fader VR is connected between the speaker and the speaker. and,
Such power amplifiers have an AUX output terminal that allows connection of an external 4-channel power amplifier. A separate small-signal fader VR was provided to adjust the output balance of the speakers.

(Problem to be solved by the invention) However, in the power amplifier of the first example above,
Space is required to house the automatic detection circuit that detects the BLT connection and disables the fader VR, but it is not easy to secure such space for car stereo amplifiers that require miniaturization, so There was a problem in that when a built-in power amplifier was connected, the fader function was omitted.

In addition, in the power amplifier of the second example, it is necessary to provide a large power fader VR for the built-in amplifier and a small signal fader VR for the external power amplifier, so it is necessary to secure installation space as well. This was not easy and became a factor in rising costs.

Structure of the Invention (Means for Solving the Problems) In order to solve the above problems, the present invention amplifies the signal of one channel with first and second power amplifiers, and also amplifies the speaker with each power amplifier. The first and second power amplifiers can drive one speaker with BTL connection, and can drive multiple speakers by connecting an external power amplifier, and can drive connected speakers. In a power amplifier equipped with a fader VR for adjusting the output balance of the connected speakers, a fader VR2 is connected between the input signal paths of the first and second power amplifiers 3 and 7, and the fader VR2 is connected between the input signal paths of the first and second power amplifiers 3 and 7.
A switching means 5 is provided between the VR2 and the second power amplifier 7 to connect the input terminal of the second power amplifier 7 to the input terminal of the first power amplifier 3, and connects both terminals of the fader VR2. The configuration allows connection of external power amplifiers 14 and 15, respectively.

(Function) When the first and second power amplifiers 3 and 7 drive speakers respectively by appropriately switching the switching means 5 using the above means, and when both amplifiers are connected BTL and an external power amplifier is used. The output balance of each speaker is adjusted using the same fader VR2.

(Embodiment) An embodiment embodying the present invention will be described below with reference to the drawings.The speaker drive circuit shown in Fig. 1 drives the left channel (CH/LEFT) and the right channel (CH/RIGHT). Since the circuits have the same configuration, only the circuit for the left channel will be explained, and the circuit for the right channel will be given the same reference numerals and the explanation thereof will be omitted.

Input resistors R1 and R2 are connected in parallel to an input terminal T1 of the speaker drive circuit 1, and a left channel signal voltage is inputted to the input terminal T1 from a preamplifier (not shown). Input resistance R1, R
The output side of the input resistor 2 is connected to the fader VR2, and the output side terminal voltage of the input resistors R1 and R2 can be adjusted by operating the fader VR2. In other words, if the output terminal voltage of one input resistor is increased, the output terminal voltage of the other input resistor is decreased.
The sum of the output side terminal voltages of both input resistors R1 and R2 is adjusted so as to always be constant. Note that this fader VR2 is designed to work in conjunction with the right channel drive circuit.

A first power amplifier 3 composed of an SEPP circuit is connected to the output side of the input resistor R1 via resistors R3 and R4, and the output terminal of the first power amplifier 3 is connected to the left channel front speaker 4 (hereinafter referred to as LF
(referred to as a speaker) and is grounded via a capacitor C1. When the left channel signal voltage is input to the input terminal T1, the signal voltage is amplified by the first power amplifier 3, and based on the output of the first power amplifier 3, the left channel signal is output from the LF speaker 4. Audio is output.

One input terminal T2 of the switch circuit 5 is connected to the output side of the input resistor R2 via resistors R5 and R6, and the other input terminal T3 of the switch circuit 5 is connected to the output side of the input resistor R2.
is connected to the input terminal of the first power amplifier 3. The switch circuit 5 has an input terminal T.
This constitutes a switching means for electrically switching and outputting either one of the input signals T2 and T3. The output terminal of the switch circuit 5 is connected to the output terminal of the switch circuit 5 via a phase inversion circuit 6.
A second power amplifier 7 configured with an SEPP circuit is connected, and the output terminal of the second power amplifier 7 is grounded via a left channel rear speaker 8 (hereinafter referred to as LR speaker) and a capacitor C2, and the LR speaker 8 are connected in reverse phase.
Then, when the left channel signal voltage is input to the input terminal T1 and the switch circuit 5 selects the input terminal T2, the signal voltage whose phase is inverted by the phase inverting circuit 6 is amplified by the second power amplifier 7. Based on the output of the second power amplifier 7
Left channel audio is output from the LR speaker 8.

The positive terminals of capacitors C1 and C2 are connected to the switch circuit 5 via diodes D1 and D2 and resistor R7, and are also connected to resistors R8 and R9.
It is connected to the base of transistor TR1 via. Further, the collector of the transistor TR1 is connected to the switch circuit 5, and a power supply voltage of 12V is applied through a resistor R10. The transistor TR1 is turned on when at least one of the capacitors C1 and C2 reaches a predetermined voltage based on the operation of the LF speaker 4 and the LR speaker 8, and based on the decrease in the collector potential of the transistor TR1 in this state, The switch circuit 5 outputs the signal from the input terminal T2 as shown by the solid line in FIG.
When TR1 is turned off and the collector potential rises, the switch circuit 5 operates to output a signal from the input terminal T3 as shown by the broken line in the figure.

The output side terminals of the input resistors R1 and R2 are connected to an LF speaker or
LF and LR buffer amplifiers 9 and 10 for connecting LR speakers are connected, respectively, and each buffer amplifier 9 and 10 is connected to a connector 11 for connecting each external power amplifier.

Next, the operation of the speaker drive circuit 1 configured as described above will be explained.

Now, when using this speaker drive circuit 1 as a 4-channel amplifier, connect the LF speaker 4 and LR speaker 8 to the first and second power amplifiers 3 and 7 of the left channel, respectively.
Similarly, the right channel has a front speaker 12 (hereinafter referred to as RF speaker) and a rear speaker 1.
3 (hereinafter referred to as RR speaker). In this state, an audio signal is output from the preamplifier, and the audio signal is transmitted to the first and second power amplifiers 3 and 7.
When the signal is amplified and each speaker 4, 8, 12, 13 is driven, the transistor TR1 is turned on and the switch circuit 5 selects the input terminal T2. Then, as shown in Fig. 2, the fader VR2 becomes in a state where it connects the input signal paths of the first and second power amplifiers 3 and 7, and by its operation adjusts the input voltage to both power amplifiers 3 and 7. The output balance between the front speakers 4, 12 and the rear speakers 8, 13 can be adjusted.

On the other hand, both power amplifiers 3 and 7 are connected BTL,
When connecting an external 2-channel power amplifier to configure a 4-channel power amplifier with increased output, connect a speaker between the positive and negative output terminals of both power amplifiers 3 and 7, and the capacitor Since no current flows through C1 and C2, the bias voltage of the transistor TR1 becomes 0, and the transistor TR1 becomes OFF. Then, the switch circuit 5 selects the input terminal T3, resulting in the circuit state shown in FIG. In this state, LF is connected between both power amplifiers 3 and 7 connected BTL.
Connect speaker 4 and connect LR buffer amplifier 10 with external 2-channel power amplifier 1
If you connect one channel of 4, connect LR speaker 8 to the output terminal of that channel, and connect the right channel in the same way, the fader
VR2 is in a state of connecting the input signal path between the first and second power amplifiers 3 and 7 connected by BTL and one channel of the external two-channel power amplifier 14, and by this operation, both power amplifiers 3 and 7 are connected. By adjusting the input voltage to the two-channel power amplifier 14, the output balance between the front speakers 4, 12 and the rear speakers 8, 13 can be adjusted.

In addition, as shown in FIG. 4, the first and second power amplifiers 3 and 7 are not used in both the left and right channels, and an external 4-channel power amplifier 15 is connected to each buffer amplifier in both channels, resulting in four sets. Even when configured to drive each of the speakers 4, 8, 12, and 13, the fader VR2 drives the LF speaker 4, LR speaker 8, and RF speaker 1.
The input signal paths of the power amplifiers driving the PR speakers 2 and PR speakers 13 are connected, and the output balance between the front speakers 4, 12 and the rear speakers 8, 13 can be adjusted by this operation.

In the above embodiment, the switch circuit 5 is configured to detect the BTL connection of the first and second power amplifiers 3 and 7 and automatically switch, but this may be done manually.

Effects of the Invention As described in detail above, the present invention provides
Or, if both power amplifiers 3 and 7 are used in BTL connection and external power amplifiers 14 and 15 are connected, one common fader can be used.
VR2 has an excellent effect in that it allows you to adjust the output balance of the speakers driven by each power amplifier.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of a power amplifier embodying the present invention, Fig. 2 is a schematic circuit diagram when the power amplifier is used without BTL connection,
FIG. 3 is a schematic circuit diagram showing a case where a BTL connection and an external power amplifier are used together, and FIG. 4 is a schematic circuit diagram showing a case where only an external power amplifier is used. Fader...VR2, the first power amplifier...
...3. Switch circuit as switching means...5. Second power amplifier...7. Two-channel power amplifier as external power amplifier...14 and 4
Channel power amplifier...15.

Claims (1)

[Claims] 1 The signal of one channel is amplified by the first and second power amplifiers, and each power amplifier can drive a speaker, and the first and second power amplifiers can drive one speaker by BTL connection. , and a power amplifier capable of driving a plurality of speakers by connecting an external power amplifier, and equipped with a fader VR for adjusting the output balance of the connected speakers, the first and second power amplifiers 3, 7, and between the fader VR2 and the second power amplifier 7, the input terminal of the second power amplifier 7 is connected to the input terminal of the first power amplifier 3. A power amplifier equipped with a fader VR, characterized in that a switching means 5 is provided to enable connection of external power amplifiers 14 and 15 to both terminals of the fader VR2.