Switch-mode power supply short-circuit protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In switch-mode power supplies, the current sensing resistor is often short-circuited during production, leading to inefficient screening processes and potential safety hazards due to excessive current flow, which existing methods like fixed turn-on time limitations fail to address effectively across varying input voltages.
Innovation Solution
A control apparatus with a short-circuit protection module that detects a voltage across the current sensing resistor and generates a protection signal to control the switching transistor's operation, preventing damage by turning it off when a short-circuit is detected, thereby avoiding erroneous protection and breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the current sensing resistor is used for current-limiting protection, then the switching transistor is protected from excessive current, but the protection system becomes vulnerable to false triggering when the sensing resistor is short-circuited
Solution Approach 1:
The patent applies preliminary action by detecting the voltage across the current sensing resistor at a specific moment when the switching transistor is turned on. If the voltage is below a predetermined threshold within a predetermined period, the system proactively shuts down before damage can occur. This preventive detection mechanism resolves the contradiction by establishing reliable protection without requiring complex continuous monitoring systems.
Solution Approach 2:
The patent uses the voltage signal across the current sensing resistor as an intermediary to detect short-circuit conditions. Instead of directly monitoring the sensing resistor's physical state or using complex diagnostic circuits, the system mediates through the voltage signal that naturally appears during switching operation. This simple intermediary approach provides reliable detection while maintaining system simplicity.
2Ease of operation
If a fixed delay time is used to detect short-circuit, then the detection process is simple, but the protection becomes inaccurate under varying input voltages
Solution Approach 1:
The patent applies dynamics by making the detection threshold adaptive rather than fixed. The predetermined voltage threshold is adjusted based on the input voltage level, allowing the system to maintain accurate short-circuit detection across varying operating conditions. This dynamic adjustment resolves the contradiction by preserving detection simplicity while improving accuracy through voltage-proportional thresholding.
Solution Approach 2:
The patent changes the detection parameter (voltage threshold) based on operating conditions. Instead of using a single fixed voltage threshold, the system adjusts the threshold parameter according to the input voltage level, enabling accurate short-circuit detection across different voltage conditions while maintaining the simplicity of threshold-based detection.
3Speed
If the switching transistor is shut down immediately upon detecting low voltage, then protection is rapid, but false shutdowns occur during normal operation
Solution Approach 1:
The patent uses preliminary action by detecting the voltage condition at the precise moment when the switching transistor is turned on. The predetermined period for detection is synchronized with the switching cycle, ensuring that the voltage check occurs when it is most meaningful. This timing-based approach enables rapid protection response while avoiding false shutdowns during normal operation.
Solution Approach 2:
The patent applies periodic action by checking the voltage across the sensing resistor at regular intervals synchronized with the switching cycle. The detection occurs during specific periods when the switching transistor is expected to be on, creating a rhythmic detection pattern that distinguishes normal operation from fault conditions, thus enabling fast response without false positives.
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
The solution effectively prevents switch-mode power supply breakdown and erroneous protection by accurately detecting short-circuits and controlling the switching transistor, enhancing safety and reducing production inefficiencies.
Implementation Method 1
a short-circuit protection module, configured to detect a voltage across a current sensing resistor of the switch-mode power supply
Data Source
AI summary
The present disclosure provides a control apparatus of a switch-mode power supply and a switch-mode power supply. In the control apparatus of the present disclosure, a short-circuit protection module is set, and when a switching transistor of the switch-mode power supply is turned on, and the short-circuit protection module detects that a voltage across a current sensing resistor of the switch-mode power supply is less than a predetermined value within a predetermined period, that is, the current sensing resistor is short-circuited, the short-circuit protection module generates a short-circuit protection signal, and a driving controller controls the switching transistor to turn off according to the protection signal, thereby switching off the control apparatus, preventing breakdown of the switch-mode power supply, and avoiding erroneous protection.