Amplification Circuit Compensation for Common-Mode Voltage Fluctuation
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Solution Overview
Problem
The BD modulation switching technique used in class-D amplifiers results in significant common-mode voltage fluctuation, which degrades the gain of differential operational amplifiers in the loop filter.
Innovation Solution
An amplification circuit with a common-mode voltage compensation circuit that includes a switching-type digital-to-analog converter, which couples the control node to power ground voltage when both output signals are high and to power supply voltage when both output signals are low, thereby establishing voltage dividers to stabilize the common-mode voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If BD modulation switching technique is used to achieve high-efficiency amplification, then power loss is reduced, but common-mode voltage fluctuation occurs which degrades amplifier gain
Solution Approach 1:
The patent introduces a common-mode voltage compensation circuit as an intermediary component that generates a compensation signal to counteract the common-mode voltage fluctuation caused by BD modulation switching. This compensation circuit includes compensation capacitors and switches that actively adjust the common-mode voltage level, thereby maintaining amplifier gain stability while preserving the high-efficiency benefits of BD modulation
Solution Approach 2:
The patent dynamically changes the common-mode voltage parameter through the compensation circuit. By adjusting the common-mode voltage level in response to the switching states of the power driver transistors, the system maintains stable differential signal operation despite the inherent common-mode fluctuations from BD modulation
2Productivity
If BD modulation switching is implemented with large analog input signals, then amplification efficiency is improved, but common-mode voltage fluctuation becomes more significant
Solution Approach 1:
The compensation circuit operates as a feedback mechanism that continuously monitors the common-mode voltage level and adjusts the compensation signal accordingly. The circuit uses the differential output signals to control the switching states of compensation transistors, creating a closed-loop system that maintains common-mode voltage stability during high-efficiency BD modulation operation
Data Source
AI summary
An amplification circuit with a common-mode voltage compensation circuit is shown. The common-mode voltage compensation circuit has a first compensation resistor coupled between an input terminal of a loop filter of the amplification circuit and a control node, and a second compensation resistor coupled between another input terminal of the loop filter and the control node. The control node is coupled to a power ground voltage when the two output signals of the amplification circuit are high, and it is coupled to a power supply voltage when the two output signals of the amplification circuit are low.