Highly efficient class-G amplifier and control method thereof

• US 8,310,313 B2
• Filed: 10/06/2010
• Issued: 11/13/2012
• Est. Priority Date: 10/09/2009
• Status: Expired due to Fees

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Guo, Jwin-Yen, Wu, Tsung-Nan
• Primary Examiner(s): Nguyen, Hieu
• Application Number:
  US12/898,962
• Publication Number:
  US 20110084760A1
• Time in Patent Office: 769 Days
• Field of Search: 330/297, 330/251, 330/207.A, 330/136, 330/131, 330/207.P
• US Class Current: 330/297
• CPC Class Codes: H03F 1/0244 Stepped control
• CPC Class Codes: H03F 2203/45522 the FBC comprising one or more potentiometers
• CPC Class Codes: H03F 2203/45528 the FBC comprising one or more passive resistors and being coupled between the LC and the IC
• CPC Class Codes: H03F 2203/45591 the IC comprising one or more potentiometers
• CPC Class Codes: H03F 2203/45594 the IC comprising one or more resistors, which are not biasing resistor
• CPC Class Codes: H03F 3/45475 using IC blocks as the active amplifying circuit

Abstract

A highly efficient class-G amplifier includes an amplifier circuit coupled between a positive power rail and a negative power rail to amplify an audio input signal of the class-G amplifier, and a boost inverting power converter to convert a supply voltage to a positive rail voltage and a negative rail voltage on the positive and negative power rails. The boost inverting power converter includes a boost inverting power stage coupled to the positive and negative power rails, and a controller to switch the boost inverting power stage between a boost mode and an inverting mode. An audio level detector detects the audio input signal for the controller to adjust the positive and negative rail voltages. The class-G amplifier has higher efficiency and requires lower cost because it does not need a charge pump.

Claims

1. A highly efficient class-G amplifier comprising:

an amplifier circuit coupled between a positive power rail and a negative power rail for amplifying an audio input signal;

a boost inverting power converter coupled to the positive and negative power rails for converting a supply voltage to a positive rail voltage and a negative rail voltage on the positive and negative power rails respectively; and

an audio level detector coupled to the boost inverting power converter for detecting the audio input signal for the boost inverting power converter to adjust the positive and negative rail voltages;

the boost inverting power converter comprising;

a boost inverting power stage coupled to the positive and negative power rails and a power input terminal receiving the supply voltage; and

a controller coupled to the boost inverting power stage for switching the boost inverting power stage between a boost mode and an inverting mode;

the boost inverting power stage comprising;

an inductor;

a first power switch coupled between the power input terminal and inductor;

a second power switch coupled between the inductor and a ground terminal;

a first diode coupled between the negative power rail and inductor;

a second diode coupled between the inductor and positive power rail;

a first capacitor coupled to the negative power rail;

a second capacitor coupled to the positive power rail;

a first voltage divider coupled to the negative power rail for dividing the negative rail voltage to generate a first feedback signal for the controller; and

a second voltage divider coupled to the positive power rail for dividing the positive rail voltage to generate a second feedback signal for the controller.

2. The class-G amplifier of claim 1, wherein the controller comprises:

a first error amplifier coupled to the audio level detector for amplifying a difference between a first detection signal provided by the audio level detector and a first feedback signal derived from the positive rail voltage to generate a first error signal;

a first comparator coupled to the first error amplifier and boost inverting power stage for comparing the first error signal with a first ramp signal to generate a first control signal to determine the positive rail voltage;

a second error amplifier coupled to the audio level detector for amplifying a difference between a second detection signal provided by the audio level detector and a second feedback signal derived from the negative rail voltage to generate a second error signal; and

a second comparator coupled to the second error amplifier and boost inverting power stage for comparing the second error signal with a second ramp signal to generate a second control signal to determine the negative rail voltage.

3. A control method for a highly efficient class-G amplifier having an amplifier circuit coupled between a positive power rail and a negative power rail to amplify an audio input signal of the class-G amplifier, the control method comprising the steps of:

switching a boost inverting power stage between a boost mode and an inverting mode for generating a positive rail voltage and a negative rail voltage on the positive and negative power rails respectively; and

detecting the audio input signal for adjusting the positive and negative rail voltages;

the step of detecting the audio input signal adjusting the positive and negative rail voltages comprising the steps of;

generating a first detection signal and a second detection signal according to the audio input signal;

amplifying a difference between the first detection signal and a first feedback signal derived from the positive rail voltage for generating a first error signal;

comparing the first error signal with a first ramp signal for generating a first control signal to determine the positive rail voltage;

amplifying a difference between the second detection signal and a second feedback signal derived from the negative rail voltage for generating a second error signal; and

comparing the second error signal with a second ramp signal for generating a second control signal to determine the negative rail voltage.