JPS6022556B2 - Electrostatic electroacoustic transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrostatic electroacoustic transducers such as so-called capacitor headphones and capacitor speakers.

Generally, electroacoustic transducers are driven by a large amount of electrical signals supplied from a power amplifier.
If an electrical signal with a power higher than the allowable input level is supplied, it will be damaged, so it is necessary to provide protection against this.

In particular, in an electrostatic electroacoustic transducer, for example, a capacitor headphone 1 having a configuration as shown in FIG.
When a high voltage higher than the allowable voltage is applied between the electrodes 3a and 3b, the vibrating membrane 4 located between the electrodes 3a and 3b may be damaged due to the discharge generated between the electrodes 3a and 3b. In addition, since it has the drawback of easily causing adverse effects such as the generation of noise, it is necessary to ensure protection against overpower input.

In addition, in FIG. 1, 5 is a voltage of 100V applied to the vibration membrane 4.
It is a DC power supply for applying a DC bias voltage of about ~300V, and 6 boosts the electrical signal supplied to the primary coil 6a connected between input terminals 7a and 7b by about 50 times. This is a boosting transformer for applying voltage between the electrodes 3a and 3b of the electrostatic electroacoustic transducer 2 from the secondary coil 6b. Therefore, in the conventional electrostatic electroacoustic transducer as described above, as shown in FIG. , the operation of the relay drive circuit 10 is controlled by the rectified output from the full-wave rectifier circuit 9 connected in parallel to the primary coil 6a, and when the rectified output exceeds a predetermined level, the relay drive circuit 10
A protection circuit 12 is additionally used, which supplies an exciting current to the relay coil 11 and connects the override race switch 8.

The conventional example shown in FIG. 2 is a stereo condenser type headphone, and includes one electrostatic electroacoustic transducer element 2 for the left channel and one for the right channel.
Equipped with step-up transformers 6, 6, relay switches 8, 8 and full-wave rectifier circuits 9, 9.

``In the above-mentioned capacitor type headphones 1, each input terminal 7a, 7b, 7c, Td is connected to a cable 13a, respectively.
, i3b, 13c, and 3d to the respective output terminals 15a, 15b, 15c, and turtle 5d of the power amplifier 14. The Rch signal is amplified by the power amplifier 14 and sent to each voltage source 14a and 1b.
Each primary coil 6a of each step-up transformer 6, 6? 6
It is designed to be inherited by a.

By the way, in the conventional example with the above-mentioned configuration, a protection circuit 12 is used which detects the voltage of an electric signal with a double-wave rectifier circuit 9 connected in parallel to the primary coil 6a' of the step-up transformer 6 and performs a protective operation. Therefore, the protection circuit 12 acts as a load in parallel to the primary coil 6a of the step-up transformer 6, and deteriorates the sound quality of the acoustic signal output from the electrostatic electroacoustic transducer 2. It has the disadvantage of being

Also, for example, if the cables 13a and 13b are connected incorrectly, the first output terminal 5a between the power amplifier 14 and the capacitor type headphones may also be connected as shown by the broken line in FIG.
When the second input terminal 7b and the second output terminal 15b and the first input terminal 7a are connected, the first voltage source 14a of the power amplifier turtle 4 is connected to each terminal quantity 5a, ? b, 7d, turtle 5
There is a drawback that damage may occur due to a short circuit via d.

SUMMARY OF THE INVENTION Therefore, the present invention provides a highly durable electrostatic electroacoustic transducer that eliminates the above-mentioned conventional drawbacks by providing a detection coil for obtaining an overpower prevention signal. .

Hereinafter, the present invention will be described in detail with reference to the drawings showing one embodiment.

FIG. 3 shows a circuit diagram of an embodiment in which the present invention is applied to stereo headphones configured as the capacitor type headphones shown in FIG. 1 above.

In this embodiment, the same parts as those of the conventional example described above are designated by the same numbers in the drawings, and detailed explanation thereof will be omitted.

In the embodiment shown in FIG. 3, a relay switch 2
8 and the primary coil 26a of the step-up transformer 26 are connected in series.

The step-up transformer 26 has the input terminals 7a and 7b.
The secondary coil 2 boosts the electrical signal coupled to the primary coil 26a by about 50 times and outputs the boosted electric signal.
6b and “voltage (or fin flow) according to the above electric signal
A detection coil 26c for outputting a detection signal is provided independently from each other. The electrostatic electroacoustic transducer 2 is connected to the secondary coil 26b of the step-up transformer 26, and converts the fin air signal boosted by the step-up transformer 26 into the electrostatic electroacoustic transducer described above. The element 2 converts it into an acoustic signal and outputs it.

Further, a full-wave rectifier circuit 29 is connected to the detection coil 26c of the step-up transformer 26, and the full-wave rectifier circuit 29 performs full-wave rectification on the voltage detection signal corresponding to the electric signal. Peak hold circuit 26 for the rectified output signal
'I'm supplying this.

This peak hold circuit 21 holds the peak level of the rectified output signal and supplies the obtained peak hold signal to the relay drive circuit 22. It is composed of a Schmitt trigger circuit having a threshold level corresponding to the allowable input level of the headphones 30,
When the peak value of the detection signal exceeds the threshold level, an exciting current is supplied to the relay coil 24,
The relay coil 24 is energized to open the relay switch 28. The above detection coil 26c "full wave rectifier circuit 29, peak hold circuit 21, relay drive circuit 2
2 and a protection circuit 32 consisting of a relay switch 28
In the embodiment as described above, the step-up transformer 2
6 is provided with a detection coil 26c independent of the primary coil 26a and the secondary coil 26b. The protection circuit 32 connected to the detection coil 26c does not act as a series load to the signal system, thereby degrading the sound quality of the acoustic signal output from the electrostatic electroacoustic transducer 2. There is no.

Also, in the above embodiment, similarly to the conventional example shown in FIG. As mentioned above, in this embodiment, the protection circuit 32 is provided in the step-up transformer 26 independently of its primary coil 26a and secondary coil 26b. Since it is connected to the detection coil 26c, each input/output terminal 7a, 7b, 7c, 7d, 15a of the capacitor type headphone 30 and the power amplifier quantity 4 is connected to the detection coil 26c.
, 15b, 15c, and 16d.
Even if the connections 13b, 13c, and 13d are incorrectly connected, the power amplifier 14 will not be damaged.As described above, according to the present invention, the step-up transformer in the electrostatic electroacoustic transducer is A detection coil independent of the side coil and the secondary coil is provided, and the detection coil outputs a voltage detection signal corresponding to the electrical signal supplied to the primary coil, so the protection circuit is activated by the detection signal. Not only is it possible to perform a protective operation reliably without degrading the sound quality of the acoustic signal, but also it can cause accidents such as short-circuiting and damage to the output end of the power amplifier due to connections between external wiring. This eliminates the problem and allows the intended purpose to be fully achieved.

It should be noted that the present invention is not limited to the above-mentioned embodiments. For example, the structure of an electrostatic electroacoustic transducer may include
In addition to those using fixed electrodes, movable electrodes may be used.Also, as a vibrating membrane, instead of applying a bias voltage, a charged electret film may be used without a bias power source.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a general electrostatic electroacoustic transducer. FIG. 2 is a circuit diagram showing a secondary electrostatic type electroacoustic transducer including a protection circuit. FIG. 3 is a circuit diagram showing an embodiment of the electrostatic electroacoustic transducer according to the present invention.2
...... Electrostatic electroacoustic transducer, 3a, 3b...
Electrode, 4... Vibration membrane, 14... Power amplifier, 2
6...Step-up transformer, 26a...Primary side coil, 26b...Secondary side coil★26c...Detection coil, 28...Relay switch, 29...Full wave rectifier circuit , 30... Capacitor type headphones " 32... Protection circuit. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. An electrostatic electroacoustic transducer that converts electrical signals into acoustic signals using a vibrating membrane that operates in response to changes in the electric field between electrodes that form a capacitor, and a primary coil, secondary coil, and voltage that are independent of each other. It consists of a step-up transformer equipped with a detection coil and a power amplifier that amplifies the electrical signal.
The electrical signal supplied from the power amplifier to the primary coil of the step-up transformer is boosted and applied from the secondary coil between the electrodes of the electrostatic electroacoustic transducer to obtain an acoustic signal, and the boosted voltage is An electrostatic electroacoustic device characterized in that an overpower prevention signal is obtained from a voltage detection coil of a transformer, and the connection between the power amplifier and the primary coil of the step-up transformer is cut off by this signal. conversion device.