JPH0232840B2 - DEJITARUSHINGONYORIKUDOSARERUSUPIIKA - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speaker driven by a digital signal.

Conventionally, even in digital signal transmission systems, when driving a speaker, an expensive D-A converter as an electric circuit is required to convert the digital signal into an analog signal at its output stage and supply it to the speaker. In addition, an operating power source was also required for this purpose.

For this reason, recently, speakers (digital speakers) that can be driven by directly supplying digital signals themselves have been proposed. An example of this is explained with reference to FIG. 1. 1 is a diaphragm called a cone, 2 is a coil bobbin, and 3a to 3d are drive coils (usually called voice coils) wound on the bobbin 2. n (four in this example) coils are provided independently. 4 is a pole piece, 5 is an annular magnetic pole provided opposite to the pole piece 4, and forms a cylindrical air gap with the pole piece 4. In this figure, the magnet and the magnetic circuit based thereon are omitted.

For such a speaker 6, an n-bit (4-bit signal for the speaker 6 in this example) signal is supplied to each of the corresponding coils 3a to 3d.
This allows it to be driven directly.
Of course, in this case, the ratio of the currents supplied to each coil 3a to 3d is selected to be 2 ⁰ : 2 ¹ : 2 ² : 2 ³ , or if the current values are the same, each coil 3a to 3d is A turns ratio of ~3d is chosen as described above.

In a speaker with this type of configuration, the total number of voice coils is enormous, which means that a digital signal of about 16 bits is normally required even when reproducing an audio signal, so 16 independent voices are required. A coil is required, which inevitably increases the air gap mentioned above and reduces the efficiency of the speaker. Also, depending on the winding position of the coil,
There are drawbacks such as different characteristics, and furthermore, there is a drawback that the structure as a whole becomes complicated.

The present invention avoids these drawbacks and makes it possible to provide a speaker that can achieve its purpose with a simple configuration without using a complicated and expensive electronic D-A conversion circuit. .

The speaker driven by the digital signal according to the present invention will be explained with reference to FIG. 2 and below.
7 is an analog signal input terminal, 8 is an A-D converter, and 9 is an amplifier thereof, in which an n-bit (4-bit in this example) signal is amplified in parallel. 9a to 9d are its output terminals. Sho 1
0 is a speaker used as a normal electric-acoustic converter for analog signals, and hereinafter this will be referred to as the speaker body. 11 is its voice coil.

In the present invention, a transformer 12 is provided, primary coils 13a to 13d corresponding to the number of bits n (in this example, 4 bits) are wound around the transformer 12, and the secondary coil 14 is connected to the transformer 12 of the speaker body 10. voice coil 1
4. In this case, each coil 13a-13d has a respective output terminal 9a-9.
The output signal is supplied from d, but the current is proportional to the weight of each bit (2 ⁰ , 2 ¹ , 2 ² , 2 ³ ), or when the same current is supplied. In this case, the winding ratio of each of the windings 9a to 9d is selected to be inversely proportional to the bit weight mentioned above. That is, ^the winding ratio is selected to be ^{23 : 22} : ²¹ :20 for each bit of 20: ²¹ : ²² : ²³ .

FIG. 3 shows another embodiment, and parts corresponding to those in FIG. 2 are denoted by the same reference numerals and their explanation will be omitted.
In this example, a so-called capacitor type speaker (in the figure, a push-pull type speaker) is used, and 15 indicates a DC power supply in this case. And 2
The next coil is connected to electrodes (diaphragms) 16a and 16b serving as a driving section of the capacitor speaker 10.

According to the present invention described above, depending on the length of the transformer 12 used, it is possible to easily convert an n-bit digital signal into an analog signal, and therefore, it is possible to easily convert an n-bit digital signal into an analog signal. The present invention has the feature that the purpose can be easily achieved by using a relatively inexpensive transformer 12 without requiring any A-D converter.

The digital signals used in this example are:
It will be clear that in addition to binary signals, ternary signals (+1, 0, -1) can also be used.

Further, the transformer 12 may be directly attached to the back of the speaker body 10, or may be used separately.

[Brief explanation of drawings]

FIG. 1 is an enlarged cross-sectional view of a portion of an example of a conventional speaker driven by a digital signal, FIG. 2 is a connection diagram of the speaker according to the present invention in use, and FIG. 3 is a connection diagram showing another embodiment. It is a diagram. 8 is an A-D converter, 12 is a transformer, 13a to 1
3d is the primary coil, 14 is the secondary coil, 10
is the speaker body.

Claims (1)

[Claims] 1. It has a transformer wound with n coils as a primary coil, each corresponding to an n-bit digital signal, and the secondary coil is driven by a digital signal connected to a drive unit such as a speaker drive coil. speaker.