DC-DC Converter Switching Noise Suppression Circuitry
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Solution Overview
Problem
DC-DC converters face challenges in suppressing switching noise and power supply noise, which can lead to inaccurate overcurrent protection and potential damage to load circuitry, reducing the reliability and efficiency of the converter.
Innovation Solution
Incorporating a replica current sensing circuit and a differential amplifier to match and cancel common-mode noise components between the output current sensing path and the reference current path, ensuring accurate overcurrent protection and improved reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switching elements are used to transform input voltage to switched voltage, then power conversion efficiency is improved, but switching noise is generated that affects overcurrent protection accuracy
Solution Approach 1:
The patent creates a replica current sensing circuit that copies the structure and noise characteristics of the output current sensing circuit. This replica circuit generates a noise signal that matches the switching noise present in the actual sensing path, allowing the noise to be canceled through differential amplification while maintaining accurate overcurrent protection capability.
Solution Approach 2:
The patent introduces a differential amplifier as an intermediary element that processes the sensing signals. The differential amplifier configuration inherently rejects common-mode noise while amplifying the differential signal containing the actual current information, thus separating the useful current measurement from the harmful switching noise.
2Measurement precision
If noise suppression measures are implemented, then overcurrent protection accuracy is improved, but device complexity increases
Solution Approach 1:
Instead of using complex digital filtering or external noise cancellation circuits, the patent employs a replica current sensing circuit that mirrors the structure of the main sensing circuit. This copying approach generates matching noise signals that can be canceled through simple differential amplification, achieving noise suppression without substantial complexity increase.
Solution Approach 2:
The replica current sensing circuit is designed to self-generate the appropriate noise signal by replicating the same switching noise mechanisms present in the main sensing path. This self-service approach eliminates the need for external noise injection circuits or complex adaptive filtering algorithms.
3Measurement precision
If common-mode noise is rejected, then signal-to-noise ratio is improved, but power supply noise and switching noise may be amplified
Solution Approach 1:
The replica current sensing circuit copies not only the sensing topology but also the noise generation mechanisms, including power supply noise coupling and switching noise. This ensures that the noise signals from both the main and replica paths are matched in characteristics, allowing the differential amplifier to reject them as common-mode noise rather than amplifying them.
Solution Approach 2:
The differential amplifier configuration provides inherent feedback mechanisms that maintain the balance between the two sensing paths. By continuously comparing the signals from the output current sensing circuit and the replica current sensing circuit, the system dynamically rejects common-mode noise while preserving the differential signal containing the actual current measurement.
Data Source
AI summary
A DC-DC converter is disclosed. The DC-DC converter includes a sensing circuit having a first path to sense an output current of the DC/DC converter. A reference circuit generates a reference current to flow along a second path. The reference current is for comparison to the output current. A noise injection circuit couples to the second path and includes a replica circuit of the sensing circuit to sense the reference current. A differential amplifier rejects a common mode noise between the first path and the second path.