Signal Processing Noise Immunity via Power Switching
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Solution Overview
Problem
Signal processing circuits, particularly analog to digital converters, are susceptible to noise propagation through the power supply rail, which can lead to inaccurate conversions and output errors due to noise-induced perturbations during critical decision-making processes.
Innovation Solution
Incorporating a switch or filter in the power supply to disconnect or attenuate noise from the signal processing apparatus during critical operations, utilizing a reservoir capacitor to provide temporary power and reduce noise interference, and implementing a noise-reducing filter in the power supply path to minimize noise impact on the circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the signal processing apparatus is continuously connected to the power supply, then the operation is uninterrupted and power delivery is stable, but noise propagates through the power supply rail and perturbs critical decision-making processes
Solution Approach 1:
A reservoir capacitor is pre-charged before the critical decision period to store sufficient energy. The capacitor is charged during a preliminary time period when the switch is closed, ensuring that when the switch opens during the critical decision period, the capacitor can immediately supply power without interruption or noise propagation.
Solution Approach 2:
The power supply connection is periodically interrupted during critical decision periods by opening the switch. This periodic disconnection occurs only when needed (during critical decisions) rather than continuously, allowing noise filtering when required while maintaining normal operation otherwise. The reservoir capacitor enables this periodic action by bridging the power supply gaps.
2Object-affected harmful factors
If the switch disconnects the signal processing apparatus from the power supply during critical periods, then noise propagation is reduced, but power interruption may occur without sufficient energy storage
Solution Approach 1:
The reservoir capacitor is pre-charged to an appropriate voltage level before the critical decision period begins. This preliminary charging ensures that when the switch opens, the capacitor has sufficient stored energy to maintain power supply to the apparatus throughout the entire critical period without voltage droop or interruption.
Solution Approach 2:
The impedance of the power supply path is dynamically changed by switching. When the switch is closed, the impedance is low allowing normal power flow. When the switch opens during critical periods, the impedance increases to block noise propagation, while the reservoir capacitor maintains voltage levels. The capacitor's impedance characteristics change with its charge state, providing different functions at different times.
3Measurement precision
If the critical decision period is extended to ensure accurate conversion, then conversion accuracy improves, but exposure to noise propagation increases
Solution Approach 1:
The switch is opened periodically during the conversion process specifically during the critical decision period when the converter is most vulnerable to noise. This creates a noise-free window for the critical comparison operation. The periodic switching allows the conversion process to continue with extended duration for accuracy while limiting noise exposure to only the necessary minimum duration during critical decisions.
Solution Approach 2:
Noise protection is applied locally and selectively during the critical decision period rather than uniformly throughout the entire conversion process. The switch opens only when the comparator is making its critical decision, providing targeted noise filtering exactly where and when it is most needed for accuracy, while allowing other non-critical phases to proceed without interruption.
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
This approach significantly improves the noise immunity of signal processing circuits by reducing noise-induced errors and enhancing the accuracy of conversion results, applicable to various converter technologies and circuits requiring reduced electrical noise environments.
Implementation Method 1
utilizing a reservoir capacitor to provide temporary power and reduce noise interference
Data Source
AI summary
A signal processing apparatus that includes a circuit in which a signal processing function is performed during a first time period, the signal processing apparatus including or being associated with a switch or a filter in a power supply to the signal processing apparatus so as to disconnect the signal processing apparatus from the power supply or to filter the power supply during a second time period that is coincident with at least part of the first time period.