Voltage Sampling Control Circuit for Isolated Switching Power Supply
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Solution Overview
Problem
In isolated switching power supplies, voltage sampling across transformer windings can be affected by resonance and parasitic parameters, leading to inaccurate voltage information and abnormal circuit operation due to interference, especially when the rise time of the voltage signal is long.
Innovation Solution
A voltage sampling control circuit that generates first and second blanking time signals based on reference voltages, ensuring the sampling signal is not detected during their activation, and converts the sampling signal to a detection signal after both blanking times have deactivated, using a bleeder circuit, blanking time control circuit, and sample and hold circuit to generate a feedback signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage sampling is performed continuously across transformer windings, then real-time voltage information is obtained, but resonance and parasitic parameters cause inaccurate voltage information and abnormal circuit operation
Solution Approach 1:
The patent applies preliminary action by generating blanking time signals before the resonance interference occurs. The blanking time control circuit detects the voltage sampling signal and generates blanking time signals that prevent sampling during resonance periods in advance, thus avoiding the harmful effects of resonance on voltage measurement accuracy.
Solution Approach 2:
The patent uses blanking time signals as an intermediary mechanism between the voltage sampling signal and the sampling process. These blanking time signals act as a mediator that blocks the sampling of inaccurate voltage information during resonance periods, allowing accurate sampling only when the voltage signal is stable and free from resonance interference.
2Measurement precision
If blanking time signals are used to block sampling during resonance, then accurate voltage information is obtained, but sampling cannot be performed during the blanking period
Solution Approach 1:
The patent applies periodic action by implementing continuous monitoring of the voltage sampling signal to generate blanking time signals periodically. The blanking time control circuit continuously detects voltage levels and generates blanking signals only during necessary periods, allowing sampling to proceed normally during non-resonance periods while blocking only during resonance interference.
Solution Approach 2:
The patent uses parameter changes by adjusting the blanking time duration based on the detected voltage signal characteristics. The blanking time control circuit monitors the voltage sampling signal and generates blanking time signals with durations adapted to the actual resonance conditions, minimizing time loss while ensuring accurate sampling.
3Duration of action of stationary object
If voltage sampling is performed during resonance periods, then continuous monitoring is maintained, but the rise time of the voltage signal causes interference and abnormal operation
Solution Approach 1:
The patent implements feedback by using the voltage sampling signal itself to control the sampling process. The blanking time control circuit continuously monitors the voltage sampling signal and uses this feedback to generate blanking time signals that prevent sampling during resonance periods, ensuring reliable circuit operation while maintaining continuous monitoring capability.
Solution Approach 2:
The patent applies preliminary action by detecting voltage signal characteristics in advance to predict resonance conditions. The blanking time control circuit monitors the voltage sampling signal and generates blanking time signals before resonance interference affects the sampling, preventing abnormal circuit operation while maintaining continuous monitoring.
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 effectively shields resonance periods, providing accurate voltage information and preventing abnormal circuit operation by ensuring the sampling signal is not sampled during interference, thus stabilizing the power supply operation.
Implementation Method 1
a voltage at one side can be sampled from the other side of the transformer based on the coupling properties between the windings of the transformer
Data Source
AI summary
A voltage sampling control circuit can include: a bleeder circuit that generates a sampling signal by sampling a voltage across a winding of a transformer of an isolated switching power supply; a blanking time signal control circuit that activates a first blanking time signal when the sampling signal is higher than a first reference voltage, and activates a second blanking time signal when the sampling signal rises to a level of a second reference voltage, where active portions of the first and second blanking time signals overlap, and the sampling signal is not detected during activation of either of the first and second blanking time signals; a converter configured to convert the sampling signal to a detection signal after both of the first and second blanking time signals have been deactivated; and a sample and hold circuit configured to receive the detection signal, and to generate a feedback signal.