Speaker Current Sensing Circuit to Eliminate Common-Mode Conversion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current audio signal processing systems face challenges in accurately sensing speaker current, particularly due to common-mode to differential-mode conversion, which affects temperature prediction and total harmonic distortion, especially in high-power mobile devices with limited battery voltage.
Innovation Solution
The implementation of a circuitry with capacitive summation and double-sampling techniques to reduce systematic mismatch and random capacitance mismatch, using an H-bridge amplifier configuration with capacitive elements to eliminate common-mode components and improve accuracy in current sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional current sensing is used in high-power audio amplifiers, then power output is achieved, but common-mode to differential-mode conversion occurs causing inaccurate temperature prediction and increased total harmonic distortion
Solution Approach 1:
The patent extracts and removes the harmful common-mode component from the current sensing signal path. By using a differential amplifier configuration that rejects common-mode signals, the unwanted conversion effect is eliminated while preserving the useful differential signal for accurate speaker current sensing.
Solution Approach 2:
The patent employs asymmetric capacitor values (C1 ≠ C2) in the feedback network of the differential amplifier. This asymmetry is deliberately designed to cancel out the common-mode to differential-mode conversion effect, where the different capacitance values create opposing phase shifts that neutralize the harmful conversion.
2Device complexity
If simple amplification stages are used, then device complexity is low, but systematic mismatch and random capacitance mismatch reduce sensing accuracy
Solution Approach 1:
The patent implements a feedback mechanism using capacitors C1 and C2 connected from the output to the inverting input of the differential amplifier. This feedback network compensates for systematic mismatches in the amplifier stages and reduces the impact of random capacitance variations, thereby improving sensing accuracy without requiring complex circuitry.
3Use of energy by moving object
If battery voltage is limited in mobile devices, then portability is improved, but achieving high power output becomes difficult
Solution Approach 1:
The patent changes the operating parameters of the amplifier by using differential signaling and capacitive feedback networks that optimize the voltage utilization. This allows the amplifier to achieve higher power output from limited battery voltage by improving the efficiency of voltage-to-power conversion and reducing energy losses.
Data Source
AI summary
Certain aspects of the present disclosure are generally directed to circuitry and techniques for current sensing. For example, certain aspects provide a circuit for signal amplification including a first amplifier, a second amplifier, and a third amplifier. The circuit also includes a first capacitive element coupled between a first output of the first amplifier and a first input of the third amplifier, a second capacitive element coupled between a second output of the first amplifier and a second input of the third amplifier, a third capacitive element coupled between a first output of the second amplifier and the first input of the third amplifier, and a fourth capacitive element coupled between a second output of the second amplifier and the second input of the third amplifier.