Switching power amplifier and method of controlling the same
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.
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.