Differential Class-D Amplifier Loops for Crossover Distortion
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Solution Overview
Problem
Existing amplifier circuits face challenges in reducing signal distortion, particularly in class-D amplifier circuits used for driving speakers, where crossover distortion can occur due to narrow pulse widths and limited open loop gain.
Innovation Solution
The amplifier circuit employs two loop filters with integration circuits and a negative resistor circuit to generate differential output signals with reduced crossover distortion, increasing open loop gain, and using high-pass filters to prevent abrupt current changes, thereby minimizing signal distortion and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a class-D amplifier circuit is used to drive speakers, then power efficiency is improved, but signal distortion increases due to crossover distortion
Solution Approach 1:
The amplifier circuit is divided into two separate push-pull amplifier circuits (first and second) that operate independently. Each circuit has its own feedback loop and integration circuit, allowing them to process different portions of the signal waveform separately. This segmentation prevents the crossover distortion that occurs in traditional single-ended class-D amplifiers by eliminating the need for a single output stage to handle the entire signal range.
Solution Approach 2:
The patent implements feedback circuits that feed back the output signals to the respective integration circuits. The first feedback circuit connects the first output signal to the first integration circuit, and the second feedback circuit connects the second output signal to the second integration circuit. This feedback mechanism allows the system to correct for distortions and maintain accurate signal reproduction while preserving the power efficiency of class-D operation.
2Loss of energy
If the pulse width is reduced to improve switching efficiency, then power consumption decreases, but crossover distortion increases
Solution Approach 1:
By segmenting the amplifier into two independent push-pull circuits, each handling half of the signal waveform, the patent eliminates crossover distortion entirely. Each circuit operates with sufficient pulse width to accurately represent its portion of the signal without the transitions and dead zones that cause distortion in single-ended designs.
Solution Approach 2:
Instead of using a single amplifier circuit that switches between positive and negative output states (which causes crossover distortion), the patent inverts the approach by using two circuits that each maintain a consistent output state. The first circuit handles the positive half-cycle and the second circuit handles the negative half-cycle, both with continuous operation and feedback, thereby inverting the traditional class-D architecture to eliminate the distortion source.
3Device complexity
If open loop gain is limited to maintain circuit simplicity, then device complexity is reduced, but signal distortion increases
Solution Approach 1:
The patent employs feedback circuits in each push-pull amplifier stage that feed the output signals back to their respective integration circuits. This feedback mechanism effectively increases the open-loop gain of each stage, allowing for more accurate signal reproduction and reduced distortion. The feedback loops compensate for non-linearities and ensure that the output accurately follows the input signal, thereby reducing distortion without requiring excessively complex circuitry.
Solution Approach 2:
The patent changes the operational parameters of the amplifier circuits by implementing dual independent push-pull stages with separate feedback loops. This parameter change allows each circuit to operate with optimized gain and bandwidth settings, improving overall signal fidelity. The separation of feedback paths enables independent optimization of each channel's parameters, reducing distortion while maintaining manageable circuit complexity through modular design.
Data Source
AI summary
An amplifier circuit of the present disclosure includes: an input circuit that is configured to generate a differential current including a first current and a second current on the basis of an input signal; a first loop filter including a first former-stage integration circuit, a first inverter circuit, and a first latter-stage integration circuit, the first former-stage integration circuit configured to perform an integral action on the basis of the first current and a current corresponding to a first output signal, and the first latter-stage integration circuit that is configured to generate a first signal by receiving an output signal of the first inverter circuit and the first output signal and performing an integral action; a first modulation circuit; a first output circuit; a second loop filter including a second former-stage integration circuit, a second inverter circuit, and a second latter-stage integration circuit, the second former-stage integration circuit that receives the second current and a current corresponding to a second output signal and is configured to perform an integral action, and the second latter-stage integration circuit configured to generate a second signal by performing an integral action on the basis of an output signal of the second inverter circuit and the second output signal; a second modulation circuit; and a second output circuit.