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JPH0846437

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DESCRIPTION JPH0846437
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
amplifier circuit, and more specifically, by supplying a power supply voltage which fluctuates
according to the magnitude of a signal, it is possible to achieve high efficiency of the amplifier. It
relates to an amplification circuit.
[0002]
2. Description of the Related Art An audio amplifier according to a conventional example will be
described below with reference to FIG. In the audio amplifier according to the conventional
example, as shown in FIG. 3, a power supply circuit including an absolute value circuit (1), a
PWM circuit (2) and a chopper power supply (3) amplifies an input signal (SI) and amplifies it. By
supplying a power supply voltage (± Vc) that fluctuates according to the magnitude of the
amplified signal (ZS) to the amplifier (4) that outputs (ZS), the power loss of the amplifier is
reduced to increase the efficiency of the amplifier. It is a circuit that
[0003]
According to this circuit, first, the amplified signal (ZS) is converted into an absolute value by the
absolute value circuit (1) and output to the PWM circuit (2). Then, based on that, the chopper
power supply (3) is switching-driven, and as shown in FIG. 4, positive and negative symmetrical
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power supply voltages (± Vc) varying according to the magnitude of the input signal (SI) are
generated. Was supposed to be supplied to
[0004]
However, in practice, the operation shown in the graph of FIG. 4 is not performed. For example,
when the input signal (SI) swings positively, the amplified signal (ZS) also swings positively as a
matter of course, but all the current flowing to the load at this time is supplied from the positive
power supply voltage (+ Vc) And there is almost no load on the negative power supply voltage (Vc). Then, while the capacitor on the side generating the negative power supply voltage (-Vc) of
the chopper power supply (3) is charged even if the duty of PMW is sufficiently small, the
negative power supply voltage (- Vc) reaches the maximum voltage in a very short time as shown
in FIG. 5 regardless of the input signal (SI).
[0005]
When the input signal (SI) swings negative, the positive side power supply voltage (+ Vc)
similarly reaches the maximum voltage as shown in the graph of FIG. There is a problem that the
power loss due to the amplifier becomes extremely large because the power supply voltage (. ±
.Vc) is supplied with a very high power supply voltage (. ± .Vc) almost independent of SI).
[0006]
In order to solve this problem, using the absolute value circuit (1), the PWM circuit (2) and the
chopper power supply (3) shown in FIG. 3 as the power supply circuit, the amplifier is BTL
(balanced) as shown in FIG. Circuits have been proposed to replace Transformer-less circuits.
This circuit is a circuit in which a load such as a speaker is connected between the outputs of the
first amplifier (5) and the second amplifier (6) as shown in FIG.
[0007]
According to this circuit, since the inverter (7) is connected to the input side of the second
amplifier (6), the inversion of the input signal (SI) input to the first amplifier (5) is achieved. By
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inputting the signal (SI1) to the second amplifier (6), the first and second amplified signals (ZS1
and ZS2) whose phases are mutually inverted are always output. For example, as shown in the
graph of FIG. 7, while the input signal (SI) swings in the positive direction, the first amplification
signal (ZS1) swinging in the positive direction is output from the first amplifier (5), At the same
time, the second amplified signal (ZS2) swinging to the negative is output from the second
amplifier (6).
[0008]
Therefore, since the load current by the amplified signal (ZS1, ZS2) serving as the load of the
chopper power supply (not shown) is always the same value on the positive side and the negative
side, it corresponds correctly to the input signal (SI) Since the power supply voltage (± Vc) is
supplied as shown in FIG. 7, the power consumption of the amplifier can be reduced to the
minimum, and the efficiency of the amplifier can be increased.
[0009]
However, when the above BTL type circuit is used in the case of an audio amplifier, it is
necessary to provide a BTL circuit as shown in FIG. 6 in each of the left channel and the right
channel. there were.
In the case of the BTL circuit, as shown in FIG. 6, two amplifiers are required for one channel, so
2 × 2 = 4 amplifiers are required for the two left and right channels. Accordingly, the number of
elements has increased, causing problems such as hindering high integration, particularly when
the circuit is mounted on a hybrid IC.
[0010]
SUMMARY OF THE INVENTION The present invention has been made in view of the abovementioned conventional drawbacks, and as shown in FIG. 1, the input signal (SL) of the left
channel is amplified to obtain the first speaker. The first amplifier (11L) that outputs the
amplified signal (ZL) of the left channel to (12L) and the phase of the input signal (SR) of the
right channel are inverted and then amplified, and the second speaker (12R) A second amplifier
(11R) for outputting an amplified signal (ZL) of the right channel, a first absolute value circuit
(13L) for absoluteizing an input signal (SL) of the left channel, and an input signal of the right
channel A second absolute value conversion circuit (13R) for converting (SR) into an absolute
value, an input signal (SL) of the left channel obtained by the absolute value conversion and an
input signal (SR) of the right channel obtained by the absolute value conversion OR circuit to
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select one of 14), a PWM circuit (15) for PWM-modulating the input signal converted into an
absolute value selected by the OR circuit (14) and driving a chopper power supply (16), and
driving the PWM circuit (15) And a chopper power supply (16) for supplying the first and second
amplifiers (11L and 11R) with a power supply voltage (. ± .Vc) that fluctuates according to the
fluctuation of the input signal (SL.SR). The present invention provides an amplifier circuit capable
of achieving high efficiency of the amplifier circuit while reducing the number of elements as
compared with the conventional BTL circuit.
[0011]
[Operation] According to the amplification circuit of the present invention, as shown in FIG. 1, a
first amplifier (11L), a second amplifier (11R), and a first speaker (12L); Second speaker (12R),
first absolute value conversion circuit (13L), second absolute value conversion circuit (13R), OR
circuit (14), PWM circuit (15), chopper power supply And 16).
[0012]
That is, the left channel amplified signal (ZL) obtained by amplifying the left channel input signal
(SL) by the first amplifier (11L) is output to the first speaker (12L), and the second amplifier
(12L) Second speaker in which the amplified signal (ZL) of the right channel amplified after the
phase of the input signal (SR) of the right channel is inverted by 11R) is in reverse phase to the
first speaker (12L) The signal is output to (12R) and the input signal (SL) of the left channel is
converted to an absolute value by the first absolute value conversion circuit (13L), and at the
same time, the input signal to the right channel (13R) is input to the right channel. SR) is
converted to the absolute value and the absolute value of the left channel input signal (SL) or the
absolute value of the right channel input signal (SR), whichever is greater, is the OR circuit (14
The absolute input signal selected by the OR circuit (14) is PWM-modulated by the PWM circuit
(15) to drive the chopper power supply (16), and the chopper power supply (16) A power supply
voltage (± Vc) that fluctuates according to the fluctuation of SL.SR) is supplied to the first and
second amplifiers (11L and 11R).
[0013]
Generally, in the case of an audio signal, the input signal (SL) of the left channel and the input
signal (SR) of the right channel have a certain degree of correlation, though they do not match
completely.
Therefore, when the left channel input signal (SL) swings to the positive side, the right channel
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input signal (SR) also swings to the positive side, so the left channel amplified signal (ZL) swings
to the positive side, the right channel The amplified signal (ZR) swings to negative because the
signal (SR1) inverted by the inverter (17) is amplified.
[0014]
Conversely, when the left channel input signal (SL) swings to the negative side, the left channel
amplified signal (ZL) swings negative and the right channel amplified signal (ZR) swings positive.
.
Therefore, as in the BTL circuit, the voltage of the amplified signal (ZL, ZR) serving as the load of
the chopper power supply is always almost the same on the positive side and the negative side.
Thus, the maximum voltage can be suppressed from being supplied as shown in FIG.
[0015]
Thus, since the power supply voltage (± Vc) corresponding to the input signal (SI) is supplied as
shown in FIG. 2, the power consumption of the amplifier can be reduced to achieve high
efficiency of the amplifier. It will be possible.
Moreover, by using two amplifiers for each of the left channel and the right channel, the number
of elements is not increased by using the BTL circuit, so the number of elements can be
significantly reduced, and the circuit is a hybrid. In the case of being mounted on an IC, the
degree of integration can be improved and the cost can be reduced, which is particularly
effective.
[0016]
Embodiments of the present invention will be described below with reference to the drawings. As
shown in FIG. 1, the amplifier circuit according to the embodiment of the present invention
includes first and second amplifiers (11L and 11R), first and second speakers (12L and 12R), and
first and second amplifiers. It consists of an absolute value conversion circuit (13L, 13R), an OR
circuit (14), a PWM circuit (15) and a chopper power supply (16), and the left channel audio
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input signal is the left channel input signal (SL) and the right channel The left channel amplified
signal (ZL) corresponding to the left channel and the right channel amplified signal (ZR)
corresponding to the right channel are generated by amplifying the right channel input signal
(SR) which is the audio input signal respectively This is an audio amplifier that causes the first
and second speakers (12L, 12R) to output.
[0017]
The first amplifier (11L) is a circuit that amplifies an input signal (SL) of the left channel to
generate an amplified signal (ZL) of the left channel and outputs the amplified signal (ZL) to the
first speaker (12L). The second amplifier (11R) amplifies an input signal (SR) of the right channel
to generate an amplified signal (ZR) of the right channel, and the second amplifier (11R) is in
reverse phase with the first speaker (12L). It is a circuit which outputs to a speaker (12R).
[0018]
The first absolute value conversion circuit (13L) is a circuit which takes the absolute value of the
input signal (SL) of the left channel and outputs it to the OR circuit (14). The second absolute
value conversion circuit (13R) is a circuit that takes the absolute value of the input signal (SR) of
the right channel and outputs the absolute value to the OR circuit (14). The OR circuit (14) is a
circuit which selects the larger one of the input signal (SL) of the left channel and the input signal
(SR) of the right channel which are converted into absolute values and outputs the selected signal
to the PWM circuit (15) It is.
[0019]
The PWM circuit (15) is a circuit that applies PWM modulation to the absolute valued input
signals (SL, SR) from the OR circuit (14) and supplies the signals to the chopper power supply
(16). The chopper power supply (16) has a switching element (SW11), a transformer (TR11) and
a rectifier circuit (SC), and based on the output of the PWM circuit (15), according to the
magnitude of the input signal (SL, SR) It is a circuit that supplies the fluctuating power supply
voltage (± Vc) to the first and second amplifiers (11L, 11R).
[0020]
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The operation of the circuit is described below. First, the amplification signal (ZL) of the left
channel and the amplification signal (ZR) of the right channel are converted into absolute values
by the first absolute value conversion circuit (13L) and the second absolute value conversion
circuit (13R), respectively. It is output to the circuit (14). Next, the larger one of the first and
right channel amplified signals (ZL and ZR) converted into absolute values is selected by the OR
circuit (14) and output to the PWM circuit (15).
[0021]
Thereafter, the output signal of the OR circuit (14) is PWM-modulated by the PWM circuit (15)
and output to the chopper power supply (16). Next, the switching element (SW11) performs
switching operation by the chopper power supply (16), current is supplied / non-supplied to the
transformer (TR11), and is rectified by the rectifier circuit (SC), according to the amplified signal.
A fluctuating power supply voltage (± Vc) is generated and supplied to the first and second
amplifiers (11L and 11R).
[0022]
On the other hand, the input signal (SL) of the left channel is input to the first amplifier (11L) and
amplified by the first amplifier (11L) to generate an amplified signal (ZL) of the left channel. At
the same time, the input signal (SR) of the right channel is inverted by the inverter (17), and the
inverted input signal (SR1) of the right channel is input to the second amplifier (11R), and the
second amplifier (11R) To amplify the right channel amplified signal (ZR).
[0023]
Next, the amplified signal (ZL) of the left channel is output to the first speaker (12L), and the
amplified signal (ZR) of the right channel is output to the second speaker (12R) to correspond to
each channel. The output voice signal is output. Note that although the amplified signal (ZR) of
the right channel is inverted in phase as described above, the phase of the second speaker (12R)
is inverted as described above, so the second speaker (12R) is eventually obtained. The phase of
the audio signal output from is returned to the original.
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[0024]
As described above, according to the amplifier circuit of this embodiment, as shown in FIG. 1, the
first amplifier (11L), the second amplifier (11R), and the first speaker (12L) are used. , The
second speaker (12R), the first absolute value circuit (13L), the second absolute value circuit
(13R), the OR circuit (14), and the PWM circuit (15); And a chopper power supply (16).
[0025]
Generally, in the case of an audio signal, the input signal (SL) of the left channel and the input
signal (SR) of the right channel have some correlation even if they do not completely match, as
shown in the graph of FIG. ing.
Therefore, when the input signal (SL) of the left channel swings to the positive side, the input
signal (SR) of the right channel also swings to the positive side. Therefore, when looking at the
amplification signal, the amplification signal (ZL) of the left channel is Swinging in the positive
direction, the amplified signal (ZR) of the right channel swings in the negative direction since it is
inverted by the inverter (17).
[0026]
Conversely, when the left channel input signal (SL) swings negative, the left channel amplified
signal (ZL) swings negative and the right channel amplified signal (ZR) swings positive.
Therefore, as in the BTL circuit, the voltage of the amplified signal (ZL, ZR) serving as the load of
the chopper power supply (16) is always substantially the same on the positive side and the
negative side, so Becomes zero, as shown in FIG. 5, it is possible to prevent the maximum voltage
from being supplied.
[0027]
Thus, since the power supply voltage (± Vc) corresponding to the input signal (SI) is supplied as
shown in FIG. 2, the power consumption of the amplifier can be reduced to achieve high
efficiency of the amplifier. It will be possible. Moreover, by using two amplifiers for each of the
left channel and the right channel, since the BTL circuit whose number of elements has been
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increased is not used, the number of elements can be significantly reduced, and the circuit is a
hybrid. In the case of being mounted on an IC, the degree of integration can be improved and the
cost can be reduced, which is particularly effective.
[0028]
As described above, according to the amplifier circuit of the present invention, the first amplifier
(11L), the second amplifier (11R), and the first speaker (12L) are used. , Second speaker (12R),
first absolute value circuit (13L), second absolute value circuit (13R), OR circuit (14), PWM
circuit (15), chopper power supply And (16).
[0029]
For this reason, since the load of the chopper power supply is always the same between positive
and negative as in the BTL circuit, the power supply voltage (± Vc) corresponding to the
amplified signal (SI) is supplied. The power consumption of the amplifier can be reduced to a
minimum, which makes it possible to improve the efficiency of the amplifier.
Moreover, by using two amplifiers for each of the left channel and the right channel, the number
of elements is not increased by using the BTL circuit, so the number of elements can be
significantly reduced, and the circuit is a hybrid. In the case of being mounted on an IC, the
degree of integration can be improved and the cost can be reduced, which is particularly
effective.
[0030]
Brief description of the drawings
[0031]
1 is a circuit diagram of an amplifier circuit according to an embodiment of the present
invention.
[0032]
2 is a graph illustrating the operation of the amplifier circuit according to an embodiment of the
present invention.
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[0033]
3 is a circuit diagram of an amplification circuit according to the conventional example.
[0034]
4 is a first graph illustrating the operation of the amplifier circuit according to the conventional
example.
[0035]
5 is a second graph illustrating the operation of the amplification circuit according to the
conventional example.
[0036]
6 is a circuit diagram of a BTL type amplifier circuit according to the conventional example.
[0037]
7 is a graph for explaining the operation of the circuit of the BTL type amplifier circuit according
to the conventional example.
[0038]
Explanation of sign
[0039]
(11L) First amplifier (11R) Second amplifier (12L) First speaker (12R) Second speaker (13L) First
absolute value circuit (13R) Second absolute value circuit (14) ) OR circuit (15) PWM circuit (16)
chopper power supply (17) inverter (SC) rectifier circuit (SW11) switching element (TR11)
transformer (SL) left channel input signal (SR) right channel input signal (ZL) Left channel
amplified signal (ZR) Right channel amplified signal
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