Class-D Amplifier Common-Mode Control for Pop-Free Transitions
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Solution Overview
Problem
Class-D amplifiers experience audible clicks or pops during startup and shutdown due to component mismatches, leading to inefficiencies and increased transition times, and existing solutions either require large capacitors or result in residual pops or incur large, adding cost and area.
Innovation Solution
The proposed solution involves controlling the common mode voltage (VCM) in a non-linear manner to adjust the duty cycle of the PWM signal, using a VCM delay controller and filtering circuitry to minimize pops while reducing transition time and capacitor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional startup and shutdown control is used in class-D amplifiers, then the amplifier can operate, but audible clicks or pops occur during transitions
Solution Approach 1:
The patent applies preliminary action by adjusting the common mode voltage before the actual startup or shutdown occurs. The VCM delay controller modifies the common mode voltage in advance during the transition period, preventing the component mismatches that cause audible clicks or pops before they can manifest in the output signal.
Solution Approach 2:
The patent changes the common mode voltage parameter dynamically during startup and shutdown transitions. By varying the common mode voltage according to a predetermined sequence, the amplifier avoids the fixed parameter conditions that lead to audible artifacts, while maintaining efficient operation during normal operation.
2Object-affected harmful factors
If existing solutions are used to reduce pops, then pop reduction is achieved, but large capacitors are required increasing area and cost
Solution Approach 1:
The patent uses parameter changes in the common mode voltage to achieve pop reduction without requiring large capacitors. By dynamically adjusting the common mode voltage parameter during transitions, the system achieves effective pop suppression through control methodology rather than through large energy storage components.
Solution Approach 2:
The patent replaces the mechanical/electrical approach of using large capacitors with an electronic control approach. Instead of relying on large capacitive elements to manage voltage transitions, the system uses active control of the common mode voltage parameter to achieve the same protective function with minimal additional area.
3Object-affected harmful factors
If existing solutions are used to reduce pops, then pop reduction is achieved, but implementation complexity increases
Solution Approach 1:
The patent implements a universal control mechanism that handles both startup and shutdown transitions using the same common mode voltage adjustment methodology. The VCM delay controller serves multiple functions: it manages transitions in both directions, works with existing amplifier circuitry, and provides a standardized approach that reduces overall system complexity despite the added control capability.
Solution Approach 2:
The patent introduces the common mode voltage as an intermediary parameter that mediates between the power supply and the differential output stages. By controlling this intermediate parameter, the system manages transitions without directly modifying the main signal path, thereby reducing the complexity of changes required in the core amplifier circuitry.
Data Source
AI summary
Methods, apparatus, systems, and articles of manufacture are described to regulate an amplifier. An example apparatus includes a modulator; a comparator having an input and an output, the input of the comparator coupled to an output of the modulator; a first switch having a voltage source terminal and a second terminal; a second switch having a voltage source terminal and a second terminal; a resistor having a first terminal and a second terminal, the first terminal of the resistor coupled to the second terminal of the first switch and the second terminal of the second switch; a capacitor having a terminal coupled to the second terminal of the resistor; and a buffer having an input and an output, the input of the buffer coupled to the terminal of the capacitor and the second terminal of the resistor, the output coupled to an input of the modulator.