Power Conversion Apparatus Abnormal Feedback Current Protection
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Solution Overview
Problem
Conventional power conversion apparatuses fail to detect abnormal feedback current signals, leading to continuous high current output and potential damage during short circuits, as the PWM control chip cannot sense voltage at the common node between the power switch and current sensing resistor.
Innovation Solution
A power conversion apparatus with a current sensing unit and control chip that monitors the duty cycle and voltage of the PWM signal, stopping the power switch if the duty cycle is continuously high and the current sensing signal voltage is low, thereby preventing damage by entering a protection mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PWM control chip uses the current sensing pin to sense voltage at the common node between the power switch and current sensing resistor, then the power conversion apparatus can adjust the conduction state of the power switch to protect from overcurrent, but when a short circuit occurs at the common node, the PWM control chip cannot detect the voltage and continuously outputs abnormally large current causing damage
Solution Approach 1:
The patent segments the voltage sensing function into two independent paths: (1) the original current sensing pin path for normal overcurrent protection, and (2) a new independent voltage sensing path that monitors the voltage at the common node separately. This segmentation allows the system to detect short circuit conditions through the independent voltage sensing path even when the current sensing path fails due to short circuit at the common node.
Solution Approach 2:
The patent introduces an intermediary voltage sensing mechanism that indirectly monitors the health of the current sensing path by measuring the voltage at the common node. This intermediary sensing approach provides a backup detection method that can identify when the primary current sensing has failed, enabling the system to respond appropriately to prevent damage.
2Productivity
If the control chip continuously switches the power switch with high duty cycle when feedback current signal is abnormal, then the power conversion apparatus maintains operation, but the power conversion apparatus or internal components are more susceptible to damages
Solution Approach 1:
The patent implements preliminary protective action by continuously monitoring the voltage at the common node through the independent voltage sensing path. When an abnormal condition is detected (such as short circuit indicated by abnormal voltage levels), the system proactively stops switching the power switch before excessive current can cause damage, rather than waiting for damage to occur.
Solution Approach 2:
The patent establishes a feedback mechanism where the voltage sensing result from the independent voltage sensing path is fed back to the control chip. This feedback loop enables the control chip to detect abnormal conditions and automatically adjust its operation by stopping the power switch switching, thereby protecting the system components from damage while maintaining the ability to resume operation after the abnormal condition is resolved.
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
Prevents continuous switching of the power switch during abnormal conditions, thereby protecting the power conversion apparatus and its internal components from damage by accurately detecting and responding to abnormal feedback current signals.
Implementation Method 1
The current sensing unit senses the current flowing through the power switch and outputs a current sensing signal
Data Source
AI summary
A power conversion apparatus and a protection method of the power conversion apparatus while a feedback current signal of the power conversion apparatus is abnormal are provided. The protection method includes a step of stopping switching a power switch if a duty cycle of a pulse width modulation signal is continuously greater than a preset duty cycle for at least one signal cycle and a voltage of a current sensing signal is smaller than a preset voltage level during the at least one signal cycle.