Adaptive Inverter Control for Common-Mode EMI Reduction
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Solution Overview
Problem
Existing isolated power supply systems face challenges in reducing dipole radiation due to asymmetry in the turn-on or turn-off of transistor pairs, leading to significant common-mode voltage variations and electromagnetic emissions.
Innovation Solution
A control circuit comprising an inverter circuit, adaptive control circuit, oscillation circuit, and driving circuit is employed to synchronize the phases of voltage signals, using phase detection and adjustment mechanisms to minimize common-mode voltage variations and reduce electromagnetic radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a full-bridge circuit is used for DC to AC conversion, then power conversion capability is improved, but asymmetry in transistor switching causes large common-mode voltage variation and dipole radiation
Solution Approach 1:
The patent implements a feedback mechanism where the switching states of transistors are monitored and fed back to the control circuit. The control circuit adjusts the switching signals in real-time to ensure symmetric turn-on and turn-off of transistor pairs, thereby minimizing common-mode voltage variation and reducing dipole radiation while maintaining full-bridge power conversion capability
Solution Approach 2:
The patent dynamically adjusts switching parameters (timing, duration, sequence) of the transistor pairs based on detected phase differences. By changing these parameters adaptively, the system maintains symmetric switching operation to reduce common-mode voltage variation and dipole radiation emissions while preserving the power conversion function
2Reliability
If transistors are turned on or off asymmetrically due to manufacturing variations, then device robustness is improved, but common-mode voltage variation increases leading to electromagnetic emissions
Solution Approach 1:
The control circuit incorporates feedback from phase detection of voltage signals to monitor switching symmetry. When manufacturing variations cause asymmetric switching, the feedback mechanism detects the phase difference and adjusts control signals to compensate, maintaining symmetric operation and reducing electromagnetic emissions while preserving device robustness
Solution Approach 2:
The patent employs dynamic adjustment of switching parameters based on real-time phase detection. The system adapts its switching behavior dynamically to compensate for manufacturing variations, ensuring symmetric turn-on and turn-off of transistor pairs regardless of initial device characteristics, thereby reducing common-mode voltage variation and electromagnetic emissions
3Adaptability or versatility
If phase difference between voltage signals is large, then switching flexibility is improved, but common-mode voltage variation increases causing dipole radiation
Solution Approach 1:
The control circuit uses phase detection feedback to monitor the phase difference between voltage signals. When phase difference exceeds a threshold indicating excessive switching flexibility, the feedback mechanism adjusts switching parameters to reduce the phase difference, thereby minimizing common-mode voltage variation and dipole radiation while maintaining appropriate switching flexibility
Solution Approach 2:
The patent dynamically changes switching parameters (timing, sequence, duration) based on detected phase differences. By adaptively adjusting these parameters, the system maintains optimal switching flexibility while ensuring phase synchronization between voltage signals, thus reducing common-mode voltage variation and electromagnetic radiation
Data Source
AI summary
Control circuits for reducing electromagnetic radiation and control methods thereof, and isolated power supply systems are disclosed. The control circuit includes: an inverter circuit, a first adaptive control circuit, a first oscillation circuit and a first driving circuit, the inverter circuit outputs a first voltage signal and a second voltage signal; the first oscillation circuit generates and outputs a first oscillation signal, a first sampling end of the first adaptive control circuit couples to the first voltage signal, a second sampling end of the first adaptive control circuit couples to the second voltage signal, an input end of the first adaptive control circuit connects with an output end of the first oscillation circuit, an output end of the first adaptive control circuit connects with an input end of the first driving circuit, and an output end of the first driving circuit connects with a control end of the inverter circuit.