Acoustic drive circuit

• US 20030219135A1
• Filed: 11/26/2002
• Published: 11/27/2003
• Est. Priority Date: 05/24/2002
• Status: Active Grant

• Current Assignee: LAPIS Semiconductor Co., Ltd. (ROHM Co., Ltd.)
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Morimoto, Masashi
• Granted Patent: US 7,171,011 B2
• Time in Patent Office: Days
• US Class Current: 381/117
• CPC Class Codes: H04R 5/033 Headphones for stereophonic communication details thereof, e.g. relating to batteries, cables or control elements H04R1/10
• CPC Class Codes: H04S 1/00 Two-channel systems H04S5/00, H04S7/00 take precedence

Abstract

An acoustic drive circuit for driving a headphone for converting variation of magnetic force, occurring to a voice coil, in sound, and outputting the sound, comprises a power amplifier for amplifying a signal at a frequency within the speech band, and outputting the signal after amplification, at a voltage with a given bias voltage superposed thereon, to one end of the voice coil of the headphone, and a pulse generation circuit for generating a pulse signal at a frequency higher than those in the speech band, having an average voltage equivalent to the bias voltage, and for outputting the pulse signal to the other end of the voice coil. The pulse generation circuit generates rectangular waves at a frequency higher than those in the speech band, having a duty ratio such that the average voltage is equivalent to the bias voltage.

Claims

1. An acoustic drive circuit for driving acoustic output means for converting variation of magnetic force, occurring to a voice coil, in sound, and outputting the sound, comprising:

power amplification means for amplifying a signal at a frequency within the speech band, and outputting the signal after amplification, at a voltage with a given bias voltage superposed thereon to one end of the voice coil of the acoustic output means; and

pulse generation means for generating a pulse signal at a frequency higher than those in the speech band, having an average voltage equivalent to the bias voltage, and outputting the pulse signal to the other end of the voice coil.

2. An acoustic drive circuit according to claim 1, wherein the pulse generation means generate rectangular waves at a frequency higher than those in the speech band, having a duty ratio such that the average voltage is equivalent to the bias voltage.

3. An acoustic drive circuit comprising;

a first power amplifier wherein a first resistor extends between a first input terminal for receiving a first acoustic signal and a negative input terminal of a first differential amplifier, a feedback resistor extends between an output terminal of the first differential amplifier and the negative input terminal, and a reference voltage (Vref) is connected to a positive input terminal of the first differential amplifier;

a second power amplifier wherein a second resistor extends between a second input terminal for receiving a second acoustic signal and a negative input terminal of a second differential amplifier, a feedback resistor extends between an output terminal of the second differential amplifier and the negative input terminal, and a reference voltage (Vref) is connected to a positive input terminal of the second differential amplifier; and

a pulse generator for generating a pulse signal at a frequency higher than those in the speech band, wherein an output of the first power amplifier is connected to one end of one voice coil of a headphone comprising voice coils for two channels, for the right and the left, while an output of the second power amplifier is connected to one end of the other voice coil, an output of the pulse generator being connected to a common terminal of the voice coils for the two channels.