Common-Mode Harmonic Detection for Class-D Amplifier Duty Control
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Solution Overview
Problem
Conventional semiconductor apparatuses for radio communication require Low Pass Filters (LPFs) to suppress harmonics, making it difficult to determine the extent of harmonic production without them.
Innovation Solution
A semiconductor apparatus with a common mode detector circuit and a detector circuit that detects the amplitude level of even-order harmonics, allowing for the optimization of the duty ratio of a class-D amplifier to minimize second harmonic amplitude, thereby suppressing harmonics without the need for an LPF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If an LPF is used to suppress harmonics, then harmonic suppression is improved, but device complexity increases and it becomes difficult to determine the extent of harmonic production without the LPF
Solution Approach 1:
The patent extracts the harmonic suppression function from the LPF and implements it through common mode detection. The common mode detector circuit separates even-order harmonics (including second harmonics) from the amplified signal by detecting common mode components, thereby suppressing harmonics without requiring an LPF and reducing device complexity
Solution Approach 2:
The patent implements feedback by using the common mode detector to monitor harmonic levels and feed this information back to the control circuit. The control circuit then adjusts the amplifier's operating parameters based on this feedback to minimize second harmonic amplitude, achieving automatic harmonic suppression without additional filtering components
2Object-generated harmful factors
If an LPF is used to suppress harmonics, then harmonic suppression is improved, but the amplifier cannot operate at high efficiency
Solution Approach 1:
The patent applies preliminary action by detecting and suppressing even-order harmonics through common mode detection before they can significantly degrade amplifier efficiency. The common mode detector identifies harmonic components early in the signal path, allowing the control circuit to adjust amplifier parameters proactively to maintain high efficiency operation
3Object-generated harmful factors
If the duty ratio of the amplifier is optimized to minimize second harmonic amplitude, then harmonic suppression is improved, but measurement precision is required to detect the minimum point
Solution Approach 1:
The patent introduces an intermediary common mode detector that converts the task of measuring small second harmonic amplitude changes into measuring common mode signal levels. This intermediary detection method enhances measurement precision by transforming the measurement into a more detectable form, allowing accurate identification of the minimum second harmonic point
Data Source
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AI summary
A semiconductor apparatus that can detect the amplitude level of harmonics is provided. A semiconductor apparatus 10 includes a common mode detector circuit 11 that detects AC signals in a common mode, and a detector circuit 12 that detects the amplitude level of an even-order harmonic output from the common mode detector circuit 11. The common mode detector circuit 11 combines AC signals being differential signals in common mode, thereby cancelling out odd-order harmonics to obtain direct current and even-order harmonics. The detector circuit 12 detects the amplitude level of the even-order harmonics from a signal obtained by the common mode detection, and outputs the detected amplitude level.