Class-D Amplifier Peak Current Sensing Without RC and ADC Overhead
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Solution Overview
Problem
Conventional class-D amplifier current sensing methods consume significant chip area due to the use of RC circuits and ADCs, and introduce errors due to assumptions about voltage drops across transistors.
Innovation Solution
A novel current sensing configuration using a peak detector and current sensor with switched capacitors and current mirrors to accurately capture and digitize peak current values, reducing chip area and improving precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RC circuits and ADCs are used for current sensing, then measurement precision is improved, but chip area increases significantly
Solution Approach 1:
The patent extracts the essential function of current sensing from complex RC circuits and ADCs, implementing it through a simplified peak detector circuit that uses only basic electronic components (operational amplifier, capacitor, and transistor) to capture peak current values directly without requiring large chip area
Solution Approach 2:
The patent creates a simplified copy of the current sensing function using a peak detector that replicates the essential measurement capability without the bulky RC circuits and ADCs, achieving the same measurement purpose with minimal components and reduced chip area
2Area of stationary object
If conventional current sensing methods are used, then chip area is reduced, but measurement precision deteriorates with error ratios of 10%
Solution Approach 1:
The patent applies preliminary action by capturing the peak current value at the moment it occurs using the peak detector circuit, locking in the maximum value before any degradation or error can occur, thereby achieving high measurement precision without requiring large chip area for complex continuous monitoring circuits
3Measurement precision
If RC circuits and ADCs are used for current sensing, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive RC circuits and ADCs with inexpensive basic electronic components (operational amplifier, capacitor, transistor) that are cheaper and easier to manufacture, achieving adequate measurement precision without the high cost of complex integrated circuits
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution significantly reduces chip area and cost while achieving precision error ratios of 0.4% to 1.3%, compared to the typical 10% error ratios of conventional methods.
Implementation Method 1
a first capacitor coupled between the output node of the peak detector and a lower power rail
Implementation Method 2
a second capacitor coupled between a second node and the lower power rail, and a drain of the third n-type transistor is coupled to the second node
Data Source
AI summary
The class-D amplifier includes an output driver stage configured to output an output signal at an output node. The class-D amplifier also includes a current sensing circuit coupled to the output node of the output driver stage, and the current sensing circuit may include: a peak detector coupled to the output node of the output driver stage configured to capture a peak value of the output signal, and a current sensor coupled to the peak detector and configured to receive the peak value of the output signal and generate a sense current based on the peak value of the output signal.