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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
digital signal reproducing apparatus configured to reproduce a plurality of Pm, Pc PCM digital
signals by a speaker. Configuration of the prior art and its problems In general, in high fidelity
music reproduction by PCM digital signal, as a means for power amplification of the signal and
sounding by the speaker, the speaker is made to sound by the class AB turtle power amplifier
after ID / A conversion . 2 PWM convert the PCM signal and make the speaker sound with Class
D power amplifier. 3 Switch the PCM signal directly and let the digital speaker produce sound.
Each method is known. The above-mentioned method 1 is the method most commonly used at
present, and the method 2 is used as a method to improve the power efficiency in the method 1.
However, if the number of quantization bits of the PCM digital signal increases, there are no
usable elements. For example, when the number of quantization bits is 16 bits at a 40 KHz
sampling frequency, the clock frequency Fc of the PCM-PWM converter is Fc ? 40 KHz О
65536 О 2.6 О 10 (H7), and conversion elements and switching elements are difficult to obtain
in practice The Also, method 3 directly drives a speaker provided with a voice coil corresponding
to the number of bits, and each weighting is 2D, 21 ░ 22 ... 2n, but as a real problem It was very
difficult to wind many voice coils on the same bobbin, and even if realized, it would extremely
degrade the efficiency of the speaker. OBJECTS OF THE INVENTION The object of the present
invention is to PWM convert PCM digital signals. It is an object of the present invention to
provide a digital signal regenerating apparatus capable of setting a low clock frequency of a
PCM-PWM converter when driving a speaker by a class D power amplifier. The digital signal
reproducing apparatus according to the present invention divides a plurality of PCM digital
signals into predetermined bit block units, and passes each of the divided PCM digital signals
through the same number of PCM-PWM converter units as the above-described number of
divisions. It is configured to be added to the same number of voice coils as the number of
divisions provided in the same speaker popin. Description of the Embodiment FIG. 1 shows an
embodiment of the present invention. In FIG. 1, a PCM digital signal 1 of a plurality of bits is
applied to the PCM-PWM converters 2 and 3 for PWM conversion. The PWM signals pulsewidth-modulated by the PCM-PWM converters 2 and 3 are power-switched by the switch 4 and 5
and supplied to the two voice coils 7.8 of the speaker 6, respectively. The PCM-PWM converters
2, 3 are configured as shown in FIG. 2 in which the speaker 6 is driven corresponding to the PCM
digital signal of a plurality of bits.
In FIG. 2, 11.12 is a counter, 13 is a JK flip flop, and 6-bit PCM digital signals are input to the
four data input terminals of the counter 11 and the two data input terminals of the counter 12.
And a clock signal of 2.6 MI-Iz is input to the clock input terminal CK of the counter 11, the carry
end CA of the counter 11 is connected to the clock input terminal CK of the counter 12, and the
load terminal LD starts. A pulse is input. The data from the carry end CA of the counter 12 is
input to the JK flip-flop, the clock input end CKK of the knob 13, and the start pulse is input to
the clear end CL '. In addition, as shown in FIG. 3, the P2 type transistor 21 and the N type
transistor 22 are connected in series as shown in FIG. 3, and when data is input to their common
base, data is output from the common emitter. It consists of a transfer gate configured to When
the transfer gate is used as the switching unit 4 of the upper bit PWM signal, a switching voltage
of 64 V is applied. When the transfer gate is used as the lower bit I) WM multiplication signal
switching unit 5, the 1 v switching voltage is used. Let me give it. With this configuration, the LCM digital signal is divided into two (for example, upper 6 bt L lower ebit in the case of 12 bits),
and the signal is PWM-converted by the PCM-PWM converter. In this case, the clock frequency
F1 in the case of not dividing and the clock frequency F2 in the case of dividing by 2 in
comparison with the case of 12 bits are extremely low frequency such as Fl-40 KHz x 4096 #
163 MHz F2-40 KH3 x 64 increased to 2.6 MH2. It is possible to extremely reduce the problems
that occur during PCM-PWM conversion and water notching. On the other hand, although the
PWM signals that have been width-117 modulated by the PCM-PWM converters 2 and 3 are
power-switched by the switching units 4 and 5, when the winding ratio of the voice coil 7.8 of
the speaker 6 is the same, The switching voltage is switched and weighted at a voltage ratio of
64: 1 on the upper bit side and the lower bit side, and bit division correction can be added. In the
above description, an example of division into two is shown, but if the number of divisions is
increased, the effect becomes more dog-friendly. Indeed, correction by bit division is possible by
changing the voice coil turns ratio.
As described above in detail, according to the present invention, in the case of PCM-PWM
conversion of a PCM digital signal, a plurality of PCM digital signals are divided into bit blocks,
and thus PCM, -PWM. The clock frequency of the conversion failure may not have to be high
enough, and can be configured with a general purpose TTL or the like, and has the advantage of
being able to perform power amplification with high efficiency using the linear region and re-
sharpen-1. It is possessed.
Brief description of the drawings
FIG. 1 is a block diagram showing an embodiment of the digital signal reproducing apparatus
according to the present invention, FIG. 2 is a concrete circuit diagram of the PCM1) WM
conversion unit of the same apparatus, and FIG. 3 is a concrete circuit of a switching unit of the
same apparatus. FIG.
1 ...... PCM digital Lee saying No. implication, 3 ...... P CM-PWM converter, 4,5 ...... switching
section, 6 ...... speaker, = 7, 8 ииииииии Voice coil. Name of Agent Attorney Nakao Toshio Other 1
person 1st rl! J Fig. 3
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description, jps5934796
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