Audio Signal Filtering for Class-D Amplifier Power Supply Pumping
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Solution Overview
Problem
Existing class-D amplifiers experience a significant processing load due to the power supply pumping phenomenon, which causes fluctuations in power supply voltage, and existing solutions require complex calculations to mitigate these fluctuations.
Innovation Solution
An audio processing device with a processor that generates and selects between two signals based on frequency reduction, determining the existence of a power supply pumping phenomenon to control the output and reduce voltage fluctuations, thereby simplifying the control process and reducing the load on the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cutoff frequency of the high-pass filter is increased stepwise to reduce power supply voltage fluctuation, then the power supply pumping phenomenon is suppressed, but the processing load increases due to time series coefficient calculations
Solution Approach 1:
The patent changes the control parameter from dynamic time series coefficient calculation to a simple binary state selection between two predetermined filter settings. The processor selects between a first state (first high-pass filter characteristics) and a second state (second high-pass filter characteristics) based on whether power supply voltage fluctuation exceeds a threshold, avoiding complex real-time coefficient calculations while maintaining effective suppression of the power supply pumping phenomenon
Solution Approach 2:
The patent segments the filter control into two distinct states with predetermined characteristics. Instead of continuously adjusting the cutoff frequency, the system divides the control space into two segments: a first state for normal operation and a second state for suppressing power supply pumping. This segmentation simplifies the control logic and reduces processing load while maintaining the ability to respond to power supply voltage instability
2Reliability
If complex time series calculations are performed to control filter coefficients, then power supply voltage fluctuation is reduced, but the processing load and computational complexity increase
Solution Approach 1:
The patent performs preliminary configuration of two high-pass filters with predetermined characteristics before runtime. The first high-pass filter is configured with first characteristic values and the second high-pass filter with second characteristic values in advance. During operation, the processor simply selects between these pre-configured filters based on power supply voltage conditions, eliminating the need for complex real-time coefficient calculations and improving processing efficiency
Data Source
AI summary
An audio processing device includes: at least one processor configured to: generate a first signal by reducing components that fall below a first frequency in an audio signal; generate a second signal by reducing components that fall below a second frequency that is higher than the first frequency in the audio signal; select between a first state for outputting the first signal and a second state for outputting the second signal; and output one of the selected first or second signal as an output signal; and a class-D amplifier configured to amplify the output signal, in which, the at least one processor is further configured to: determine whether or not a power supply pumping phenomenon exists or a possibility of the power supply pumping phenomenon exists, in a power source that supplies a power supply voltage to the class-D amplifier; and in which, in the selecting between the first state and the second state, the at least one processor is configured to select: the first state in a case where a determination result is negative, where the power supply pumping phenomenon is determined to not exist or the possibility of the power supply pumping phenomenon is determined to not exist; and the second state in a case where the determination result is affirmative, where the power supply pumping phenomenon is determined to exist or the possibility of the power supply pumping phenomenon is determined to exist.