Class-D Amplifier Deglitching Circuit for Cleaner PWM Switching
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Solution Overview
Problem
Conventional class-D amplifiers experience glitches at the output of the comparator due to spikes in the power supply rail or ground references, leading to audible distortion and increased power dissipation, which are typically addressed using additional high-frequency clocks and low-pass filters that can introduce complexity and distortion.
Innovation Solution
A deglitching circuit with digital logic is introduced between the comparator and drive circuit, utilizing a clock signal of the same frequency as the switching frequency to remove glitches without an additional high-frequency clock and low-pass filter, thereby simplifying the circuit and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional class-D amplifiers use additional high-frequency clocks and low-pass filters to remove glitches, then glitch removal effectiveness is improved, but device complexity increases
Solution Approach 1:
The patent extracts and removes only the necessary deglitching function from the complex conventional circuitry (high-frequency clocks and low-pass filters) and implements it through a simplified logic circuit that samples the PWM signal at the switching frequency, thereby removing glitches while reducing overall circuit complexity
Solution Approach 2:
The patent introduces a logic circuit as an intermediary component between the comparator and drive circuit that uses the existing switching frequency clock signal to sample and filter glitchy PWM signals, eliminating the need for additional high-frequency clocks and complex low-pass filters while maintaining effective glitch removal
2Reliability
If conventional class-D amplifiers use additional high-frequency clocks and low-pass filters to remove glitches, then glitch removal effectiveness is improved, but power consumption increases
Solution Approach 1:
The patent extracts and removes only the necessary deglitching function from the power-consuming conventional circuitry (high-frequency clocks and low-pass filters) and implements it through a simplified logic circuit that operates at the existing switching frequency, thereby removing glitches while reducing power consumption
Solution Approach 2:
The patent enables the existing switching frequency clock signal to serve dual purposes: both driving the normal class-D amplifier operation and providing the sampling clock for the deglitching logic circuit, thereby eliminating the need for additional power-consuming high-frequency clocks while maintaining effective glitch removal
3Object-affected harmful factors
If conventional class-D amplifiers use low-pass filters to filter out switching noise, then noise filtering is improved, but distortion is introduced
Solution Approach 1:
The patent introduces a logic circuit as an intermediary that samples the PWM signal at the switching frequency using AND logic operations, providing noise filtering functionality without the signal degradation and distortion introduced by conventional analog low-pass filters
Solution Approach 2:
The patent replaces the analog low-pass filter (a continuous analog system) with a digital logic-based sampling system that operates at discrete switching frequency intervals, thereby achieving noise filtering through logical operations rather than analog frequency attenuation, which avoids introducing phase shifts and signal distortion
Data Source
AI summary
In an embodiment, a class-D amplifier includes an input terminal configured to receive an input signal; a comparator having an input coupled to the input terminal; a deglitching circuit having an input coupled to an output of the comparator; and a driving circuit having an input coupled to an output of the deglitching circuit. The deglitching circuit includes a logic circuit coupled between the input of the deglitching circuit and the output of the deglitching circuit. The logic circuit is configured to receive a clock signal having the same frequency as the switching frequency of the class-D amplifier.