Predictive Supply Switching in Class-D Audio Amplifiers
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Solution Overview
Problem
Class-D amplifiers face significant energy wastage during no-load and light-load operations due to high internal operating voltages, leading to increased power loss and potential for audible interference and current surges when voltage is rapidly changed.
Innovation Solution
A method that predicts the voltage requirement for the output stage of a class-D amplifier, allowing it to operate with the lowest necessary voltage and gradually switch to higher voltages as needed, ensuring sufficient voltage is available without causing interference, by using a digital signal processing unit to determine and apply voltages of different magnitudes before amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high internal operating voltages are used in class-D amplifiers, then sufficient voltage is available for proper amplification, but power loss increases significantly during no-load and light-load operations
Solution Approach 1:
The amplifier dynamically adjusts its internal operating voltage based on the actual signal requirements. The voltage is changed from a fixed high level to a variable level that adapts to the instantaneous power needs, thereby reducing energy waste during low-power operations while ensuring sufficient voltage is available when needed for proper amplification.
Solution Approach 2:
The internal operating voltage parameter is changed from a constant high value to a variable value that can be adjusted according to the signal power requirements. This parameter change allows the amplifier to operate efficiently at lower voltages during no-load and light-load conditions while maintaining the capability to provide high voltage when required for full-power operation.
2Loss of energy
If voltage is rapidly changed to reduce power loss, then energy efficiency improves, but audible interference and current surges occur
Solution Approach 1:
The amplifier performs preliminary action by predicting future power requirements based on the delayed audio signal. This allows voltage changes to be planned and executed in advance, preventing sudden voltage transitions that would cause audible interference and current surges. The voltage is adjusted smoothly before the high-power signal actually arrives at the output stage.
Solution Approach 2:
The system uses feedback by continuously monitoring the delayed audio signal to determine future power requirements. This feedback mechanism allows the amplifier to anticipate when voltage changes are needed and execute them smoothly, avoiding rapid transitions that would generate harmful interference and current surges while still achieving energy efficiency.
3Loss of energy
If voltage magnitude is reduced to save energy, then power loss decreases, but voltage may be insufficient for proper amplification when needed
Solution Approach 1:
The amplifier takes preliminary action by using the delayed audio signal to predict future power requirements and proactively adjust the voltage magnitude before the high-power signal arrives. This ensures that when full power amplification is needed, the voltage has already been increased to the appropriate level, preventing insufficient voltage while maintaining energy efficiency during low-power periods.
Solution Approach 2:
The voltage magnitude is made dynamic rather than fixed, allowing it to be adjusted in real-time based on predicted signal requirements. This dynamic adjustment ensures the voltage is reduced to save energy during no-load and light-load operations while being increased to sufficient levels when needed for proper amplification, resolving the contradiction between energy saving and voltage sufficiency.
Data Source
AI summary
The invention relates to a method for operating a class-D amplifier (2) for an audio signal (4), which class-D amplifier contains an output stage (10) and a signal-processing unit (12) in a signal path (6), wherein a voltage (U) of at least two magnitudes (U1, U2) is provided for the output stage (10), a voltage requirement (B) of the output stage (10) for the audio signal (4) is predictively determined from the audio signal (4) at a measurement location (14) before the signal-processing unit (12), a magnitude (U1, U2) that is minimally sufficient for the voltage requirement (B) is selected on the basis of the voltage requirement (B) and said magnitude is applied to the output stage (10) before the amplification. A class-D amplifier (2) for an audio signal (4), having a signal path (6), which has an output stage (10) and a signal-processing unit (12), contains a voltage source (16) for the output stage (10) having a voltage (U) of at least two magnitudes (U1, U2), a measurement location (14) before the signal-processing unit (12), and a control and evaluation unit (18) for predictively determining a voltage requirement (B) for the output stage (10) for the proper amplification of the audio signal (4) from the audio signal (4) at the measurement location (14), wherein the control and evaluation unit (18) selects a magnitude (U1, U2) that is minimally sufficient for the voltage requirement (B) on the basis of the voltage requirement (B) and applies said magnitude to the output stage (10) before the amplification.