JPS5812409A - Amplifying circuit - Google Patents

Abstract

PURPOSE:To synthesize two input signals, and to amplify those two input signals independently, by adding a switching circuit to a BTL amplifying circuit which inputs two input signals directly. CONSTITUTION:A BTL amplifying circuit 20 equipped with two input terminals 22A and 22B consists of a phase inverter 24 and power amplifiers 32 and 26, and a switching circuit 26 is further provided. When the switching circuit 26 is set at a solid-line position, the amplifying circuit 20 forms a BTL amplifying circuit and two input signals supplied independently from the terminals 22A and 22B are synthesized to drive a load 38 connected between output terminals 34A and 34B. When the switching circuit 26 is placed at a dotted-line position, the two input signals are amplified independently to drive loads 42A and 42B. Thus, two input signals are synthesized and also amplified independently.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplification path, in which two input signals such as left and right stereo signals are directly applied to the BTL (Ba1ance).
d Trmaformer Less) relates to a device that enables the synthesis of signal components by amplification.

In the case of ultra-small portable tape recorders and radios, where stereo playback is performed only with stereo headphones and the built-in speaker is set to play only monaural signals, the amplifier circuit that provides the drive input to the speaker is BTLQ.
A signal synthesis circuit is installed at the front stage to convert the stereo signal to mono full. FIG. 1 shows a BTLI circuit and a signal synthesis circuit used in such a case. That is, since the conventional BTL circuit is set to be operated by a single person, it is necessary to synthesize the left and right stereo signals and the R signals in advance to convert them into monaural signals. Signal combiner (MIX) 2
A composite tie (/) signal is given from the switch circuit 4, and the signal composite output is amplified by the contact power amplifier 6 and supplied to the load 8 such as a speaker, while the phase is inverted by the phase inverter 1O. It is amplified by the power amplifier 12 and supplied to the other terminal of the load 8.In this way, in the case of the conventional circuit, the BT
It is necessary to synthesize the stereo signals before the L amplification, and the presence of the signal synthesizer 2 and the switch circuit 4 complicates the circuit configuration and increases the cost, while at the same time having the disadvantage of lowering reliability.

Further, the BTL circuit is installed for a monaural load 8 such as a speaker, and in the conventional system, a separate amplification circuit is installed for a stereo headphone. For this reason, in addition to the above-mentioned drawbacks, the circuit configuration has also become complicated, and it has been necessary to simplify the configuration in order to suppress battery consumption.

An object of the present invention is to simplify the circuit configuration by omitting the signal synthesizer and switch circuit of the conventional circuit, and to synthesize each component of two input signals such as left and right stereo signals, or to synthesize each component of two input signals. To provide an amplifier circuit which allows simple operations such as switching connections of loads without amplifying them individually.

The present invention provides a phase inverter that receives one of two individually given input values t and inverts its phase, and either the output of the phase inverter or the input signal before the phase inversion. a first amplifier that amplifies m of this amplifier;
* a switching circuit inserted into the first amplifier in response to a control input to select either the phase inverted output or the input signal before phase inversion and supply it to the first amplifier; a second amplifier that directly amplifies the other signal that is not input to the inverter, and a load is connected between the output terminals of the first and second amplifiers or for each output terminal, and the switching operation of the switching circuit ( Based on the load between the output terminals [a combined output of two signal components is applied, or the output of an amplifier is applied individually to the load of each output terminal.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 2 shows an embodiment of the amplifier circuit of the present invention. In the figure, this amplifier circuit 20 has two input terminals 22A.
, 22B are provided, and each input terminal 22A1228 has 2
Two input signals are provided individually. The terminal 23 is a reference level terminal (GND) that serves as a reference for each input signal.The input signal given to the input terminal 22AK is input to a phase inverter 24#C, and the phase inverted output obtained by this phase inverter 24 is It is input to the switching circuit 26 along with the input signal before inversion.The switching circuit 26 selects and outputs either the phase inverted output or the input signal based on the control signal input to the control input terminal 28. This switching circuit 26 can be configured with an analog switch composed of switching transistors, etc. The phase inverted output or input signal outputted from this switching circuit 26 is inputted to the first power amplifier 32#C, and its amplified output is output from the output terminal 34A. On the other hand, the input signal applied to the input terminal 228 is input to the second power amplifier 36, and its amplified output is taken out from the output terminal 34B. A load 38 such as a speaker is inserted and connected between each output terminal 34A or 34B and a terminal 40.
42 people were wearing headphones etc. between 0 and 0.

42B is inserted and connected. Each load 38 or 42A, 42
B is used by switching the connection, one point IIAII corresponds to the one-dot chain line of the equivalent contact 26F of the switching circuit i6, and when the switching circuit 26 is switched like the one-dot chain line, each load 42A, 42B is an output terminal. 34A and 34B, and at this time, the load 38 is connected to S.

In the above configuration [, 34 output terminals, 34BK loads
8 is inserted and connected, and when a control signal is applied from the control input terminal 28 to the switching circuit 26 and the equivalent contact 26F is switched to the state shown by the solid line, the amplifier circuit 20 is connected to the BTL.
When the circuit is configured, it becomes. In this case, input terminal 28A
It is assumed that an input signal shown in Part K, Figure 3, AK is applied, and an input signal shown in Figure 3, BK, is applied to the other input terminal 28B. Note that the maximum amplitudes of each signal waveform are assumed to be el and efi. The input signal applied to the input terminal 28AK has its phase inverted by the phase inverter 24 and is converted into the waveform shown in FIG. 3 OK. On the other hand, the input signal applied to the input terminal 28BK is directly amplified by the power amplifier 36, and the output shown in FIG. 3DK appears at the output terminal 34BK. The amplitude of this output waveform becomes *e due to the amplification gain KK of the power amplifier 36. Also,
The phase inverted output is amplified by the power amplifier 32 and output to the output terminal 3.
Figure 3 1 for 4A! An output shown in appears, the amplitude of which depends on the same amplification gain of the power amplifier 32 as described above.
−e=). These outputs appearing at each output terminal 34A, 34BK are applied to the load 38 from the terminals in the opposite direction, so the load 38 is given both outputs shown in FIG. Become.

In addition, in this BTL circuit, when the right stereo signal component (+ΔL) is supplied to the input terminal 22A and the left stereo signal component (L+ΔB) is supplied to the other input terminal 228, the phase inverter 24 The above symbol (R+Δ
Since an inverted signal -(R+ΔL) of L) is obtained, if the gain K of each power amplifier 32.36 is set to 1 for convenience, the output (2) applied to the load 38. is the inverted output -(R+ΔL) and (
It becomes a composite value of L+ΔR). That is, ■. is L+ΔR−(
-B-ΔL), the signal component becomes (L+ΔL+ΔR), and a sum signal of stereo signals can be formed. Therefore, it is possible to synthesize stereo signals, that is, convert them into monaural signals, by using BTL amplification without using the signal synthesizer and switch circuit that were required in conventional circuits. be able to. In addition, when a monaural signal A is given to each input terminal 22 and 228, the output v0 is (A-(-A)), as is clear from Figure 3 to F.
Therefore, there are two people and the load 3B is driven by the normal BTL output.

Also, load 38 to load 4! A, 42BII connections are switched, and at the same time the control signal input to the control input terminal 28 causes the equivalent contact 26F of the switching circuit 26 to switch to I, which is indicated by a dashed line.
When the IK is switched, the amplifier circuit 20 is switched to the power amplifier 32.
．． Signal amplification occurs at 36. That is, input terminal 22A&
The right stereo signal component (R+ΔL) given to C is directly amplified by the power amplifier 32 and then applied to the load 42AK, and the left stereo signal component (L+ΔR) given to the input terminal 228 is directly amplified by the power amplifier 36. After being amplified with
A load of 42 BK is added. Therefore, loads 42A, 42B
are driven by separate signal components, and if the loads 42A and 42B are stereo headphones, stereo reproduction can be achieved.

According to this amplifier circuit, the load is 38 or 42A.
, 42B and the switching operation of the switching circuit 26, it is possible to form the form of the signal component according to the load. Moreover, by simply inserting the switching circuit 26 in addition to omitting the signal combiner etc., the power amplifier 32. 36 is shared, the circuit configuration can be simplified and is economical. Furthermore, since the signal components are synthesized by BTL amplification while omitting the signal synthesizer and switch circuit, it is possible to combine signal components with high reliability.In addition, the generation of the control signal applied to the control input terminal 28 is If control is performed by switching the connections of the loads 3B, 42A, and 42B, a signal mode depending on the load can be effectively formed.

FIG. 4 shows an FM stereo broadcast receiver using the amplifier circuit 20. That is, the FM front end 42, the intermediate frequency amplification and FM detection circuit 44, and the multiplexer t461-
The stereo signals separated left and right are sent to an amplifier circuit 20.
0 Å force is applied to terminals 28A and 28B individually. A speaker 48 corresponds to the load 38, and represents a single speaker built into the set. speaker 50A
, 50B correspond to the loads 42A and 42BK and are externally connected to the set, and can be replaced with stereo headphones. Therefore, by switching the connection of these speakers 48, 50, 50B and switching the switching circuit 26 by the control signal applied to the control input terminal 28, the speaker 4
8#C can give a monaural signal, and speakers 50A and 50BK can give stereo signals.

Note that the present invention can be used not only for radio but also for synthesizing various signal components, such as monaural playback of stereo recordings of cheap recorders, and it is possible to extract signal component output according to the load.

As explained above, according to this invention, BTL amplification allows
High reliability as it is possible to synthesize two input signal components
- Signal synthesis is possible, different signal forms can be changed depending on the load, and the circuit configuration can be simplified by omitting a signal synthesizer, etc.

[Brief explanation of the drawing]

FIG. 1 is a pull diagram showing a conventional BTL circuit, FIG. 2 is a block diagram showing an embodiment of the amplifier circuit of the present invention, FIG. The figure is a block diagram showing a stereo receiver which is an application example of the present invention. 20... Amplifier circuit, 24... Phase inverter, 26-...
-Switching circuit, 32...first amplifier, 34A, 34B
...Output terminal, 36...Second amplifier, 38.42
A, 42B--Load. Figure 1 Figure 2 028 Figure 3

Claims (1)

[Claims] A phase inverter that receives one of the two input signals seen individually and inverts its phase, and a phase inverter that amplifies the output of the phase inverter or the input signal before phase inversion. 1 amplifier, and select either the phase inverted output or the non-phase inverted input signal based on the control input inserted from the outside and provided to the first amplifier. a switching circuit, and a second amplifier that directly amplifies the other signal of the two human input signals that is not input to the phase inverter, and between the output terminals of the first and second amplifiers or for each output terminal. A load is connected to the output terminal, and the combined output of two input signal components is applied to the load between the output terminals based on the switching operation of the switching circuit, or the output of each amplifier is applied to the load of each output terminal. Amplification circuit.