Speaker driving device

A speaker driving device comprising:

• a pair of voice coils, said pair being formed by a first voice coil and a second voice coil, said first and second voice coils being fixed around a driving section of a speaker to generate a bi-directional driving force at said driving section when a current flows through said first and second voice coils in opposite directions;
• a voltage source for generating a substantially constant voltage having direct current and alternating current components;
• direct current blocking means for blocking a direct current component of the substantially constant voltage;
• delta sigma modulating means responsive to a multi-bit digital audio signal for producing a one-bit binary digital pulse density modulated (PDM) signal by high-speed sampling delta sigma modulation;
• and
• switching means for alternatively applying the direct current component of the substantially constant voltage to one of said first and second voice coils and the alternating current component from said direct current blocking means to the other voice coil directly responsive to said one-bit digital audio PDM signal so as to cause the current to flow through said first and second voice coils in opposite directions, said speaker functioning as an acoustic low-pass filter.

A speaker driving comprising:

• a constant voltage source for generating a voltage to be applied to a voice coil in a speaker;
• delta sigma modulating means responsive to a multi-bit digital audio signal for producing a one-bit binary digital audio pulse density modulated (PDM) signal by high-speed sampling delta sigma-modulation;
• ternary signal generating means for producing a ternary signal from said one-bit digital audio PDM signal;
• and
• switching means for switching the polarity of the constant voltage as applied to the speaker depending on whether the ternary signal is +1 or -1 and for controlling the application of the constant voltage to said voice coil by switching said constant voltage source between on and off according to an absolute value of said ternary signal, the absolute value being either 0 or 1, said speaker functioning as an acoustic low-pass filter.

The speaker driving device comprising:

• a constant voltage source for generating a constant voltage to be applied to a voice coil in a speaker;
• delta sigma modulating memos responsive to analog audio signals for separately producing a one-bit binary distal audio pulse density modulated (PDM) signal representing a positive portion of an original analog audio signal and a one-bit binary digital audio PDM signal representing a negative portion thereof by high-speed sampling delta sigma-modulation;
• ternary signal generating means for producing a ternary signal from said two one-bit digital audio PDM signals;
• and
• switching means for switching the polarity of the constant voltage as applied to the speaker depending on whether the ternary signal is +1 or -1 and for controlling the application of the constant voltage to said voice coil by switching said constant voltage source between on and off according to an absolute value of said ternary signal, the absolute value being either 0 or 1, said speaker functioning as an acoustic low-pass filter.