Switching Circuit Protector for PWM Overcurrent Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional switching circuit protectors fail to accurately break a semiconductor switch when operating in PWM mode due to errors in temperature estimation, leading to potential overheating of the cable despite actual temperature exceeding the threshold.
Innovation Solution
A switching circuit protector that includes a semiconductor switch, a current sensor, a controller, a temperature estimator, and an anomaly determiner, which shifts the semiconductor switch from PWM to DC drive state when the estimated temperature exceeds a threshold, ensuring reliable protection against overcurrent and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature estimation is used to protect the switching circuit, then the protection response time is delayed, but the system complexity is reduced
Solution Approach 1:
The patent applies preliminary action by monitoring the current flowing through the cable and accumulating energy information in advance. When an overcurrent condition is detected, the controller immediately switches from PWM mode to DC mode or cuts off power, without waiting for the temperature to actually reach the threshold. This proactive approach based on current monitoring ensures rapid protection response while maintaining system reliability.
2Use of energy by moving object
If PWM drive state is used to operate the load, then the power efficiency is improved, but the temperature estimation accuracy deteriorates
Solution Approach 1:
The patent introduces current monitoring as an intermediary parameter to indirectly assess cable temperature conditions. Instead of directly measuring temperature (which is inaccurate under PWM), the system monitors the current flowing through the cable and uses this information to trigger protective actions. This intermediary approach allows the system to maintain PWM efficiency while achieving accurate overcurrent protection.
3Object-affected harmful factors
If the semiconductor switch is broken to protect the cable, then the cable overheating is prevented, but the load operation is interrupted
Solution Approach 1:
The patent applies dynamics by enabling the semiconductor switch to dynamically transition between different operating states: PWM drive state for normal efficient operation, DC drive state for overcurrent protection, and off state for severe overload protection. This dynamic state switching allows the system to adapt to different operating conditions, maintaining productivity when possible while preventing cable overheating when necessary.
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
Effectively protects the switching circuit and load by accurately detecting temperature increases and preventing overheating, even in cases of errors in temperature estimation, reducing the risk of semiconductor switch damage and ensuring safe operation.
Implementation Method 1
a current sensor for detecting a current flowing in the switching circuit
Implementation Method 2
calculating a quantity of heat generation and a quantity of heat radiation of the switching circuit
Implementation Method 3
calculating a quantity of heat generation and a quantity of heat radiation of the switching circuit
Data Source
AI summary
A switching circuit protector switches a semiconductor device (11) provided in a switching circuit connecting a power supply (VB) to a load (RL), from a PWM drive state to a DC drive state when an estimated temperature of a cable of the switching circuit estimated by a temperature estimator (22) exceeds a threshold temperature (Tth), in the state where the semiconductor device (11) is controlled to operate in the PWM drive state to drive the load (RL). Therefore, when an overcurrent is caused in the cable, the estimated temperature exceeds the threshold temperature (Tth) so as to break the semiconductor device (11). Accordingly, the switching circuit can surely be protected by the switching circuit protector.