Digital amplifier

• US 6,919,771 B2
• Filed: 09/25/2003
• Issued: 07/19/2005
• Est. Priority Date: 01/06/2003
• Status: Expired due to Fees

• Current Assignee: D&M Holdings Incorporated (Masimo Corporation)
• Original Assignee: Denon Electronics (Masimo Corporation)
• Inventors: Nakajima, Kouji
• Primary Examiner(s): MIS, DAVID C
• Application Number:
  US10/669,374
• Publication Number:
  US 20040130389A1
• Time in Patent Office: 663 Days
• Field of Search: 332/106, 332/107, 332109-111, 332/156, 330/10, 360/29, 375/238
• US Class Current: 332/109
• CPC Class Codes: H03F 2200/03 the amplifier being designed for audio applications
• CPC Class Codes: H03F 2200/351 Pulse width modulation being used in an amplifying circuit
• CPC Class Codes: H03F 3/217 Class D power amplifiers; Switching amplifiers
• CPC Class Codes: H03G 3/3021 by varying the duty cycle
• CPC Class Codes: H03G 3/341 Muting when no signals or only weak signals are present H03G3/344, H03G3/345 take precedence

Abstract

An object of the present invention is to provide a digital amplifier which is capable of preventing a reproduction of an analogue audio signal from a loud speaker, when an output sound volume from the loud speaker is set to zero and when inputting of a digital audio signal or an input signal is stopped. In order to achieve the object, in the digital amplifier of the present invention, a silent PWM signal output section 7 outputs a PWM signal having a duty ratio of 50%, instead of a PWM signal generated by the PWM signal generating section 6, in the following cases: the factor detecting section 3 detects that the digital audio signal is multiplied by the factor “0” in the gain regulation section 2, the silent signal determining section 4 determines that the signal input from the reproducing unit 13 is stopped, and the silent signal determining section 4 determines that the digital audio signal is a signal at a silent level.

Claims

1. A digital amplifier comprising,

a gain regulation means which regulates an gain for a digital audio signal,

a PWM signal generating means which generates a PWM signal from said digital audio signal, said gain which has been regulated by said gain regulation means,

a switching means which switches a switching power supply in response to said PWM signal generated by said PWM signal generating means,

a detecting means which detects said gain which has been regulated by said gain regulation means, and

a silent PWM signal outputting means which outputs to said switching means a PWM signal having a duty ratio of 50%, instead of said PWM signal which has been generated by said PWM signal generating means, when said detecting means detects that said gain is zero.

2. A digital amplifier comprising,

a determining means which determines a digital audio signal as a silent signal, when the digital audio signal has a bit value within a predetermined range and is inputted for a predetermined period of time,

a PWM signal generating means which generates a PWM signal from said digital audio signal,

a switching means which switches a switching power supply in response to said PWM signal generated by said PWM signal generating means, and

a silent PWM signal outputting means which outputs to said switching means a PWM signal having a duty ratio of 50%, instead of said PWM signal which has been generated by said PWM signal generating means, when said determining means determines that said digital audio signal is the silent signal.

3. An digital amplifier comprising,

an input signal determining means which determines whether or not an input signal from a reproducing unit exists,

a PWM signal generating means which generates a PWM signal from a digital audio signal included in said input signal,

a switching means which switches a switching power supply in response to said PWM signal generated by said PWM signal generating means, and

a silent PWM signal outputting means which outputs to said switching means a PWM signal having a duty ratio of 50%, instead of said PWM signal which has been generated by said PWM signal generating means, when said input signal determining means determines that said input signal from said reproducing unit is stopped.