JPH0440920B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a driving device that directly drives a speaker using a digital signal. Speakers driven directly by digital signals (digital speakers)
Conventionally, the one shown in FIG. 1 or 2 has been considered. This speaker is roughly the same as a conventional speaker driven by a so-called analog signal. To explain this below, 1
is a magnet, 2 is a pole piece, 3 is a magnetic yoke, 4
5 is a ring-shaped magnetic body, 5 is a diaphragm (cone), and 6 is a coil winding portion of the diaphragm 5, so-called a bobbin. In FIG. 1, the magnet 1 and yoke 3 are omitted. In the example shown in FIG. 1, n (four in this example) mutually independent drive coils 7a to 7d (usually called voice bobbins) are wound around the coil bobbin 6. In the example shown in FIG. 2, the shot ring 8 is attached to the coil winding portion 6, and the drive coils 7a to 7d are wound around the magnetic yoke 3. This digital speaker is designated by reference numeral 9. FIG. 3 shows a circuit for driving such a speaker 9, in which 10 is an analog signal input terminal;
11 is an A-D converter, and 12 is a digital signal amplifier, whereby an n-bit (4-bit in this example) signal is amplified in parallel, and a digital signal is obtained at each output terminal 12a to 12b. shall be. Incidentally, a digital signal is usually expressed as a binary value of 1 or 0, but since the signal generally changes positive and negative with respect to the 0 level as shown in Figure 4, such an analog When converting a signal into a digital signal to drive the digital speaker 9, a three-value signal, ie, 1, 0, -1, is required as the digital signal. However,
Each output terminal 12a to 12d of the amplifier 12 described above
In this method, a binary digital signal of 0 and +1 is obtained depending on the magnitude of the analog signal, regardless of the polarity of the analog signal, so a signal corresponding to the polarity of the analog signal, that is, a polarity discrimination signal of 1 and 0, is obtained. Therefore, it is necessary to switch the polarity of each output from each output terminal 12a to 12d of the circuit 11 at once and supply it to each drive coil 7a to 7d of the digital speaker 9. In this case, the direction of the current supplied to each coil 7a to 7d when the output is 1 is such that the direction of the current is superimposed (added) to the movement of the voice coil 6, that is, the direction of the current is adjusted to the direction of the signal. Of course, they should be selected so that they have the same polarity. In FIG. 3, 13 is this changeover switch (electronic switch), and 14a to 14d are each output terminal 12a to 12d and each speaker coil 7a to 7.
The switching circuits (multipliers) 15a and 15b for polarity switching inserted between the output terminals 12a and d are for converting the digital signals obtained at the respective output terminals 12a to 12d into three values, In the figure, a DC power supply is shown. Table 1 shows that the signals shown in FIG.
2a to 12d represent the states obtained. In this case, each output terminal 12a to 12d
When an output of 1 is obtained, each of these coils 7a~
The magnitude of the current supplied to 7d is 2 ⁰ : 2 ¹ : 2 ² :
The winding ratio of each drive coil 7a to ^7d is selected to be ²⁰ : ²¹ : ²² : ²³ if the magnitude of the supplied current is the same. I try to choose.

【table】

[Table] Then, the changeover switch 13 is changed according to 1 and 0 of the polarity discrimination signal. For example, if it is 1, it is switched to the position shown in the solid line, and if it is 0, it is switched to the position shown in the dotted line, thereby corresponding to the polarity of the analog signal. The direction (polarity) of the current supplied to each of the coils 7a to 7d is switched. By doing so, the speaker 9 is directly driven by the digital signal. According to the conventional digital speaker driving device described above, as is clear from FIG.
, power supplies 15a, 15b, etc. are required, and an additional 1-bit signal is required for polarity determination. The present invention provides such switching circuits 14a to 14a.
The digital speaker 9 can be driven without using the signal generator 14d and without requiring a signal for determining polarity. In the following, a digital speaker driving device according to the present invention will be described. FIG. 5 shows a circuit according to the present invention, and corresponding parts to those in FIG. That is, in the present invention, when converting an analog signal into an n-bit digital signal in the A/D converter 11, the conversion is performed according to the 2'S complement binary system.
Table 2 shows decimal values (quantized values) from -8 to +7
is converted according to the 2'S complement binary system.

[Table] Such conversion means (conversion circuits) are conventionally well known, and therefore the details of such conversion circuits will not be explained. Convert the value in natural binary notation and convert the most significant bit ((8) in this case)
By inverting the phase of , the 2'S complement binary signal shown in Table 2 can be obtained. According to the present invention, the digital signal thus binarized is directly supplied to the speaker 9. That is, the signal is supplied without using a switching circuit or the like for polarity switching as shown in FIG.
Furthermore, in the present invention, when an output of 1 is obtained at the output terminal 7a, the current direction for the coil 7a is selected so that the coil bobbin 6 of the speaker 9 drives the cone 5, for example, in the direction of pushing. The current direction for the coils 7b to 7d is selected so that the coil bobbin 6 of the speaker 9 is driven in the direction in which the cone 5 is pulled when the output 1 is obtained in each of the coils 7b to 7d. That is, as for the signals supplied to the coils 7b to 7d, the respective signals have the same polarity, that is, they are added together in terms of signals, and as for the signal supplied to the coil 7a, the respective signals ( The current direction to the drive coil 7a or the winding direction of the coil 7a is selected so that the polarity is opposite to that of the signals to the coils 7b, 7c, and 7d, that is, it is subtracted from the other respective signals. That is, drive coils 7a to 7d
If the winding direction of the drive coil 7 is the same, the drive coil 7
The direction of the current flowing through a may be reversed to that of the other coils 7b to 7d, or the driving coil 7 may
The winding direction of only coil a may be reversed from that of the other coils 7b to 7d, and the current direction may be selected to be the same. Note that when the digital signal is 0, no current is supplied to any of the drive coils, as in the conventional case. According to such a configuration, as can be seen from Table 2, when the quantized value is of positive polarity (0 to 7 in this example), it is the same as before, but when the quantized value is of negative polarity (in this example Therefore, in the case of -1 to -8), the quantized value of the most significant bit is always -8 (the sign is negative because it has the opposite polarity to the other bit signals). , are subtracted from the quantized values of the other remaining bits, so that the desired quantized value is operated in the speaker 9 itself. FIG. 6 shows another embodiment, and in this example,
A transformer 16 is provided in which coils 7a to 7d corresponding to each bit are wound as a so-called primary coil,
This is a case where the secondary coil 17 is connected to the voice coil 18 of a speaker (in this case, a normally used analog signal speaker). Also in this case, the ratio of the magnitude of the current to each coil 7a to 7d,
Alternatively, the winding ratio of each coil is selected in the same manner as described at the beginning, and the signal supplied to the coil 7a is
The polarity is selected to be opposite to that of the signals supplied to the other coils 7b to 7d. According to the present invention explained above, FIGS.
As is clear from the figure, the changeover switch 13 and polarity changeover switch circuits 14a to 14 shown in FIG.
d etc. is not required at all, and the output terminals 12a to 12d
The output of the speaker 9 can be directly connected to the speaker 9, and no bit (signal) for polarity determination is required, so the circuit as a whole can be simplified. In addition to the digital speaker 9 described above, it is also possible to use a structure in which direct current is supplied to the coil 8 and the magnet 1 is omitted, as shown in the example in FIG. Applicable.

[Brief explanation of drawings]

1 and 2 are enlarged cross-sectional views showing respective parts of a speaker driven by a digital signal,
Fig. 3 is a connection diagram showing a conventional speaker driving system, Fig. 4 is a signal waveform diagram, Fig. 5 is a connection diagram showing a speaker driving device according to the present invention, and Fig. 6 is a connection diagram showing another embodiment. It is a diagram. 7a to 7d are drive coils, 10 is an analog signal input terminal, 11 is an AD converter, and 12 is a digital signal amplifier.

Claims (1)

[Claims] 1. An analog signal is converted into an n-bit digital signal in accordance with the Two's complement binary system, and these n-bit signals are transmitted to n-bit digital speakers provided corresponding to the respective bits. A specific drive coil among the n drive coils to which a signal corresponding to the most significant bit of the digital signal is supplied; and a signal corresponding to the most significant bit of the digital signal. n-1 drive coils other than the above-mentioned specific drive coil to which signals corresponding to bits other than The direction is reversed, and the operation of the quantized value is performed by subtracting the signal supplied to the specific drive coil and the signal supplied to n-1 drive coils excluding the specific drive coil. A digital speaker drive device designed to do this.