Class G Audio Amplifier Charge Pump for Low-Loss Dual Supply Control
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Solution Overview
Problem
Class G audio amplifiers face challenges in achieving high efficiency, small size, and low cost due to high loss and large layout issues in existing designs, particularly under light loads, which result in increased costs and electromagnetic interference.
Innovation Solution
A class G audio amplifier design that incorporates a charge pump to dynamically provide both positive and negative power supplies with adjustable amplitudes based on input signal levels, using a charge pump with switches and capacitors to optimize power delivery and reduce voltage across the audio output stage, allowing for efficient operation across varying signal conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-supply class AB amplifier uses blocking capacitors to block DC bias, then the amplifier can operate with simple power supply, but the blocking capacitors require large capacitance (e.g., 470 μF) which increases size, manufacturing cost, and may interfere with external circuits
Solution Approach 1:
The charge pump continuously generates a negative power supply voltage that mirrors the positive supply voltage, enabling continuous operation of the audio output stage without requiring large blocking capacitors to handle DC bias. This continuous action eliminates the need for large capacitance while maintaining proper biasing throughout the signal cycle.
Solution Approach 2:
The charge pump acts as an intermediary device between the positive power supply and the audio output stage, generating the required negative supply voltage. This intermediary eliminates the need for large blocking capacitors by providing active voltage generation rather than passive DC blocking, thus reducing capacitor size while maintaining ease of manufacture.
2Weight of stationary object
If a charge pump is used to provide negative power supply with same amplitude as positive supply, then large capacitance blocking capacitors are eliminated and only small capacitors (e.g., 1 μF) are needed, but loss increases and efficiency decreases when input signal is small
Solution Approach 1:
The charge pump dynamically adjusts the negative power supply amplitude based on the instantaneous input signal level. When the input signal is large, the charge pump provides full-amplitude negative supply; when the input signal is small, the charge pump reduces the negative supply amplitude accordingly. This dynamic adjustment reduces power loss and improves efficiency during low-signal conditions while maintaining the benefit of small capacitor sizes.
Solution Approach 2:
The charge pump changes the voltage parameter of the negative power supply based on the input signal level. By varying the negative supply voltage amplitude dynamically, the system optimizes the operating point of the audio output stage, reducing energy loss when input signals are small while maintaining low capacitor requirements.
3Loss of energy
If two power supplies with same amplitude are used to power audio output stage, then efficiency is improved by reducing loss as both supplies vary with input signal, but the buck converter requires large layout and generates EMI, and additional inductor increases cost
Solution Approach 1:
The charge pump replaces the mechanical/bulk inductor-based buck converter system with a capacitive switching architecture. This substitution eliminates the need for large inductors and complex magnetic components, significantly reducing layout area while maintaining the ability to provide dynamic positive and negative power supplies that reduce power loss.
Solution Approach 2:
The charge pump uses capacitive switching to dynamically change the voltage parameters of both positive and negative power supplies based on input signal level. This approach achieves the same power loss reduction as a variable buck converter but with a more compact implementation that reduces layout area and eliminates EMI-generating inductors.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances efficiency and reduces size and cost by dynamically adjusting power supplies in response to input signal levels, minimizing loss and electromagnetic interference, while maintaining high-quality audio output with reduced distortion.
Implementation Method 1
a charge pump coupled to the level detector for providing a positive power supply and a negative power supply in response to the level detected signal
Implementation Method 2
a charge pump with switches and capacitors to optimize power delivery
Data Source
AI summary
The present technology is directed to class G audio amplifiers and the associated methods of operation. In one embodiment, a class G audio amplifier includes an input port, an audio output stage, a level detector, and a charge pump. The class G audio amplifier regulates the power supplies of the audio output stage according to the input signal, so as to realize high efficiency and high quality audio output.