Switching power amplifier and method of controlling the same

• US 8,410,845 B2
• Filed: 07/16/2009
• Issued: 04/02/2013
• Est. Priority Date: 07/16/2008
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Park, Hae-kwang
• Primary Examiner(s): SHINGLETON, MICHAEL B
• Application Number:
  US12/503,978
• Publication Number:
  US 20100013554A1
• Time in Patent Office: 1,356 Days
• Field of Search: 330/10
• US Class Current: 330/10
• CPC Class Codes: H03F 1/26 Modifications of amplifiers to reduce influence of noise generated by amplifying elements
• CPC Class Codes: H03F 2200/348 Pulse frequency modulation being used in an amplifying circuit
• 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: H03F 3/2173 of the bridge type

Abstract

A switching power amplifier having a pulse width modulation (PWM) signal generation unit that converts an input audio signal into a PWM signal with a predetermined carrier frequency, a correction unit that corrects the difference between an audio signal included in the PWM signal and a negative feedback output audio signal to generate a corrected PWM signal, a low pass filter that removes a high-frequency component from the corrected PWM signal, a frequency modulation unit that modulates the corrected PWM signal so that the corrected PWM signal has a switching frequency different from the carrier frequency of the input PWM signal to generate a modulated PWM signal, and a power amplification unit that amplifies a power of the modulated PWM signal.

Claims

1. A switching power amplifier, comprising:

a pulse width modulation (PWM) signal generation unit to convert an input audio signal into a PWM signal having a predetermined carrier frequency;

an error correction and frequency modulation unit, comprising;

an operational amplifier to generate a corrected PWM signal by calculating a difference between the PWM signal and a power-amplified PWM signal received from a gain-control negative feedback path, and

a self-oscillating negative feedback path to act together with the operational amplifier to first remove a high-frequency component from the corrected PWM signal to generate a corrected audio signal and then add a new switching frequency component to the corrected audio signal different from the predetermined carrier frequency, thereby generating a modulated PWM signal; and

a power amplification unit to amplify a power of the modulated PWM signal to be output to the gain-control negative feedback path.

2. The switching power amplifier of claim 1, wherein the frequency modulation unit modulates the corrected PWM signal according to a sigma delta modulation method.

3. The switching power amplifier of claim 1, wherein the frequency modulation unit modulates the corrected PWM signal by using a self-oscillation.

4. The switching power amplifier of claim 3, wherein an output terminal of the frequency modulation unit is connected to an input terminal of the frequency modulation unit through negative feedback.

5. The switching power amplifier of claim 1, wherein the PWM signal is a digital signal.

6. The switching power amplifier of claim 1, wherein the PWM signal generation unit comprises:

a digital-to-analog converter (DAC) to convert an input digital pulse code modulation (PCM) signal into an analog PCM signal;

a triangle-wave generation unit to generate a triangle-wave signal having the carrier frequency; and

a comparator to compare the triangle-wave signal having the carrier frequency with the analog PCM signal to generate an analog PWM signal having the carrier frequency.

7. The switching power amplifier of claim 1, further comprising:

a gain control unit installed on a negative feedback path for the output audio signal, the gain control unit controlling a gain value of the output audio signal.

8. The switching power amplifier of claim 1, wherein the frequency modulation unit modulates the corrected PWM signal so that the corrected PWM signal has a switching frequency smaller than the carrier frequency of the input PWM signal, thereby increasing amplification efficiency of the power amplification unit.

9. The switching power amplifier of claim 1, wherein the frequency modulation unit modulates the corrected PWM signal so that the corrected PWM signal has a switching frequency greater than the carrier frequency of the input PWM signal, thereby amplifying a PWM signal within a wide-band frequency range.

10. A method of controlling a switching power amplifier, comprising:

converting an input audio signal into a PWM signal having a predetermined carrier frequency;

correcting a difference between an audio signal included in the PWM signal and a negative feedback output audio signal to generate a corrected PWM signal;

removing a high-frequency component from the corrected PWM signal;

modulating the corrected PWM signal so that the corrected PWM signal has a switching frequency different from the carrier frequency of the input PWM signal to generate a modulated PWM signal; and

amplifying a power of the modulated PWM signal.

11. The method of claim 10, wherein the modulating modulates the corrected PWM signal according to a sigma delta modulation method.

12. The method of claim 10, wherein the modulating modulates the corrected PWM signal by using self-oscillation.

13. The method of claim 10, wherein the correcting comprises:

comparing the input PWM signal with the output PWM signal through negative feedback from a power amplification unit; and

subtracting the difference between the input PWM signal and the negative feedback output PWM signal from the input PWM signal.

14. The method of claim 10, wherein the correcting comprises:

comparing the input PWM signal with the output PWM signal through negative feedback from a power amplification unit; and

adding the difference between the input PWM signal and the negative feedback output PWM signal to the input PWM signal.

15. The method of claim 10, wherein the modulating modulates the corrected PWM signal so that the corrected PWM signal has a switching frequency smaller than the carrier frequency of the input PWM signal, thereby increasing amplification efficiency of the power amplification unit.

16. The method of claim 10, wherein the modulating modulates the corrected PWM signal so that the corrected PWM signal has a switching frequency greater than the carrier frequency of the input PWM signal, thereby amplifying the PWM signal within a wide-band frequency range.