Apparatus with ultra high output power class D audio amplifier

• US 20030095000A1
• Filed: 09/09/2002
• Published: 05/22/2003
• Est. Priority Date: 11/16/2001
• Status: Abandoned Application

• Current Assignee: Acoustic Technologies Incorporated (Cirrus Logic Incorporated)
• Original Assignee: Acoustic Technologies Incorporated (Cirrus Logic Incorporated)
• Inventors: Tsui, Tak Ping, Ramage, Robert D.
• Application Number:
  US10/237,518
• Publication Number:
  US 20030095000A1
• Time in Patent Office: Days
• US Class Current: 330/10
• CPC Class Codes: H03F 1/3205 in field-effect transistor amplifiers
• CPC Class Codes: H03F 1/342 in field-effect transistor amplifiers
• CPC Class Codes: H03F 3/2171 with field-effect devices H03F3/2173 - H03F3/2178 take precedence
• CPC Class Codes: H03F 3/2173 of the bridge type

Abstract

An apparatus and electrical circuit utilizing a high power Class “D” type amplifier for delivering an audio signal to a acoustic transducer system. A PWM modulator, the output of which is inhibited during power fluctuations or in absence of an audio input, converts a suitably conditioned audio input signal into low power, high frequency positive and negative components 180 degrees out of phase. A PWM signal power amplifier stage and low pass filters amplify the signal components, remove the higher PWM switching carrier frequency and pass the results to a power audio transformer impedance matched to the output acoustic transducers. Feedback signals are taken from the power stage before the low pass filters, suitably conditioned and combined as negative feedback with the input analog audio signal to minimize output distortion and maintain correct audio output voltage with changing load impedance and power supply voltages.

Claims

1. A circuit for delivering an audio signal to an acoustic transducer system, comprising

a signal conditioner for applying a low frequency cutoff and a desired output voltage range to said audio signal,

a pulse width modulator connected to the output of said signal conditioner for converting said audio signal into positive and negative PWM signal components 180 degrees out of phase and having a PWM switching carrier frequency higher than the highest desired audio frequency of said audio signal,

power amplifiers for amplifying respective said PWM signal components,

a negative feedback loop off the output of each said power amplifier to said signal conditioner for minimizing output distortion and maintaining correct output voltage with changing load impedance and power supply voltages,

a low pass filter after each said power amplifier for removing said PWM switching carrier frequency from said PWM signal components thereby converting the PWM signal components into audio signal components,

a power audio transformer for receiving and combining said audio signal components into an output audio signal, said transformer being connected and impedance matched to said output acoustic transducer system.

2. A circuit for delivering an audio signal according to claim 1, said feedback loops comprising a filter and feedback buffer for removing said PWM switching carrier frequency.

3. A circuit for delivering an audio signal according to claim 1, said power audio transformer having a push pull configuration.

4. A circuit for delivering an audio signal according to claim 1, said PWM switching carrier frequency being at least 10 times said highest desired audio frequency.

5. A circuit for delivering an audio signal according to claim 1, each said low pass filter further comprising a power factor correction module.

6. A circuit for delivering an audio signal according to claim 1, said power amplifiers comprising MOSFET devices.

7. A circuit for delivering an audio signal according to claim 6, said power amplifiers further comprising pre-driver MOSFET devices.

8. An apparatus for delivering an audio signal to an acoustic transducer system, comprising

a signal conditioner for applying a low frequency cutoff and a desired output voltage range to said audio signal,

a pulse width modulator connected to the output of said signal conditioner for converting said audio signal into positive and negative PWM signal components 180 degrees out of phase and having a PWM switching carrier frequency at least 10 times higher than the highest desired audio frequency of said audio signal,

power amplifiers for amplifying respective said PWM signal components,

a negative feedback loop off the output of each said power amplifier to said signal conditioner for minimizing output distortion and maintaining correct output voltage with changing load impedance and power supply voltages,

a low pass filter after each said power amplifier for removing said PWM switching carrier frequency from said PWM signal components thereby converting the PWM signal components into audio signal components,

a power audio transformer for receiving and combining said audio signal components into an output audio signal, said transformer being connected and impedance matched to said output acoustic transducer system, said feedback loops comprising a filter and feedback buffer for removing said PWM switching carrier frequency, said power amplifiers comprising MOSFET devices.

9. An apparatus for delivering an audio signal according to claim 8, said power amplifiers further comprising pre-driver MOSFET devices.

10. An apparatus for delivering an audio signal according to claim 8, said power audio transformer having a push pull configuration.

11. An apparatus for delivering an audio signal according to claim 8, said power audio transformer having a half bridge configuration.

12. An apparatus for delivering an audio signal according to claim 8, said power audio transformer having a full bridge configuration.

13. An apparatus for delivering an audio signal according to claim 8, each said low pass filter further comprising a power factor correction module.

14. An apparatus for delivering an audio signal according to claim 8, said output acoustic transducer system comprising multiple audio speakers.

15. An apparatus for delivering an audio signal according to claim 8, said output audio signal comprising a continuous 2000 watts RMS power level.

16. An apparatus for delivering an audio signal according to claim 8, said apparatus being powered with a single supply voltage.

17. An apparatus for delivering an audio signal according to claim 8, said PWM modulator configured as enabled for output only when a said audio signal is present at its input.

18. An apparatus for delivering an audio signal according to claim 17, said PWM modulator configured as disabled for output during power fluctuations and switching events.

19. An apparatus for delivering an audio signal to an acoustic transducer system, comprising

a signal conditioner for conditioning an audio signal with a low frequency cutoff and a desired output voltage range,

a pulse width modulator connected to the output of said signal conditioner for converting said audio signal into positive and negative PWM signal components 180 degrees out of phase and having a PWM switching carrier frequency higher than the highest desired audio frequency of said audio signal, said PWM modulator configured as enabled for output only when a said audio signal is present at its input, said PWM modulator further configured as disabled for output during power fluctuations and switching events,

power amplifiers for amplifying respective said PWM signal components, said power amplifiers comprising MOSFET devices,

a negative feedback loop off the output of each said power amplifier to said signal conditioner for minimizing output distortion and maintaining said output voltage range with changing load impedance and power supply voltages, said feedback loops comprising a filter and feedback buffer circuit for removing said PWM switching carrier frequency,

a low pass filter after each said power amplifier for removing said PWM switching carrier frequency from said PWM signal components thereby converting said PWM signal components into audio signal components, and

a power audio transformer for receiving and combining said audio signal components into an output audio signal, said transformer being connected and impedance matched to said output acoustic transducer system.

20. An apparatus for delivering an audio signal to an acoustic transducer system according to claim 19, each said low pass filter further comprising a power factor correction module, said apparatus being powered with a single supply voltage.