Class D Amplifier Current Feedback for Pulse Error Distortion
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Solution Overview
Problem
Class D amplifiers suffer from pulse error distortion due to unknown output current, leading to voltage errors that cannot be corrected with simple non-linearity in the forward path, requiring access to the current waveform for accurate correction.
Innovation Solution
Incorporating a correction circuit with a current sensor and voltage sensor to generate a non-linear correction signal that modifies the duty cycle, using a soft clipper to provide the correction signal to the modulator, allowing for real-time adjustment based on sensed current and voltage measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple non-linearity correction is applied in the forward path, then device complexity is reduced, but manufacturing precision of output voltage deteriorates due to inability to correct pulse error distortion
Solution Approach 1:
The patent implements feedback by sensing the output current through a current sensor and using this sensed current to generate a correction signal that compensates for pulse error distortion. The correction circuit receives feedback about the actual output current and adjusts the duty cycle accordingly, enabling accurate correction of voltage errors that simple forward-path non-linearity correction cannot address.
Solution Approach 2:
The patent introduces an intermediary correction signal that mediates between the modulator output and the final output voltage. This correction signal, generated based on sensed current measurements, acts as an intermediate adjustment that modifies the duty cycle to compensate for pulse error distortion, thereby improving output voltage accuracy without requiring complete redesign of the amplification path.
2Manufacturing precision
If current sensing and correction circuitry is added, then output voltage accuracy is improved, but device complexity increases
Solution Approach 1:
The patent implements feedback by sensing the output current through a current sensor and using this sensed current to generate a correction signal that compensates for pulse error distortion. The correction circuit receives feedback about the actual output current and adjusts the duty cycle accordingly, enabling accurate correction of voltage errors that simple forward-path non-linearity correction cannot address.
Solution Approach 2:
The patent changes the parameter being controlled from a fixed non-linearity correction to a dynamic correction based on sensed current measurements. By measuring the actual output current and using this information to generate a correction signal, the system adapts the correction amount to match actual operating conditions, improving accuracy while keeping the correction circuit relatively simple.
3Manufacturing precision
If duty cycle modification is applied, then pulse error distortion is corrected, but distortion remains at high load currents without current feedback
Solution Approach 1:
The patent implements feedback by sensing the output current through a current sensor and using this sensed current to generate a correction signal that compensates for pulse error distortion. The correction circuit receives feedback about the actual output current and adjusts the duty cycle accordingly, enabling accurate correction of voltage errors that simple forward-path non-linearity correction cannot address.
Solution Approach 2:
The patent transitions from a static non-linearity correction approach to a dynamic correction approach that adapts to varying load conditions. By continuously sensing the output current and adjusting the correction signal in real-time based on actual current measurements, the system maintains effective distortion correction across the full range of operating conditions, including high load currents where fixed correction fails.
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 effectively corrects pulse error distortion by adjusting the duty cycle, improving output voltage accuracy and reducing distortion, especially at varying load currents, with significant improvement in distortion correction across a wide range of output voltages.
Implementation Method 1
a current sensor that senses the current from the output inductor to the output terminal
Implementation Method 2
a voltage sensor at the output terminal, coupled to the correction circuitry
Data Source
AI summary
A class D amplifier that includes circuitry to apply a non-linear correction to pulse error distortion. The amplifier includes an output voltage controlling circuit, comprising at least two switches, controlled by a modulator; an output inductor, coupling the switching circuit to an output terminal; and correction circuitry to provide to the modulator a correction signal characterized by a non-linearity. The correction circuitry includes a current sensor that senses the current from the output inductor to the output terminal.