Feedback Loop Phase Alignment for Quiet Class-D Amplifier Startup
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Solution Overview
Problem
Class D-amplifiers experience spurious input during startup, leading to acoustic noise due to the transition from an idle to a steady-state operation mode, which existing technologies fail to adequately address.
Innovation Solution
A transition smoothing apparatus comprising a loop filter, an analog-to-digital converter, a controller, and an alignment detector, which integrates errors, digitizes them, and generates control signals to manage the transition smoothly, reducing spurious input and acoustic noise by detecting phase alignment between control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Class D-amplifier transitions from idle to steady-state operation mode, then the amplifier becomes operational and provides audio output, but spurious input and acoustic startup noise are generated
Solution Approach 1:
The alignment detector performs preliminary detection of phase alignment between control signals before the amplifier fully transitions to steady-state operation. This preliminary action allows the system to prepare for smooth transition by identifying when control signals are properly aligned, preventing spurious input generation during the startup process
Solution Approach 2:
The control loop with feedback control continuously monitors the amplifier operation and adjusts control signals based on detected phase alignment. The feedback mechanism enables real-time correction of potential spurious input conditions by maintaining proper synchronization between control signals during the transition from idle to operational mode
2Object-generated harmful factors
If a control loop is implemented to manage the transition, then the spurious input is reduced, but the device complexity increases
Solution Approach 1:
The alignment detector serves multiple functions: it detects phase alignment between control signals, determines when smooth transition conditions are met, and controls the transition timing. This multi-functionality reduces the need for separate dedicated components for each function, thereby limiting the increase in device complexity while effectively reducing spurious input
Solution Approach 2:
The alignment detector acts as an intermediary component between the control signals and the amplifier operation. It mediates the transition process by monitoring phase alignment and controlling when the smooth transition occurs, simplifying the overall control architecture while effectively managing spurious input reduction
Data Source
AI summary
Transition smoothing apparatus for reducing spurious input to a system under feedback control connected to a control loop. The apparatus includes a loop filter to integrate an error between an input signal applied to the loop filter and an output signal of the system under feedback control, an analog-to-digital converter to provide digitized integrated error values, a controller to generate output values supplied to the system under feedback control in response to the digitized integrated error values and in a start-up sequence to control a feedback digital-to-analog converter according to the digitized integrated error values to supply a first control signal to the loop filter and control the system under feedback control to generate a second control signal, and an alignment detector to detect phase alignment between the first control signal and the second control signal to control a smooth transition into closed loop operation of the control loop.