Adjustable Blanking Period Over-Current Protection Circuit
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Solution Overview
Problem
Conventional over-current protection methods are inadequate for heavy-duty power tools, as they may cause abrupt shutdowns due to transient over-current conditions and lack compatibility across different applications, leading to potential damage and inefficiency.
Innovation Solution
A monitoring and control circuit with a sense block, comparators, and a control module that generates a pulse width modulation (PWM) signal to adjust the current by varying the duty cycle and frequency, enabling the protection circuit to switch between normal and protection modes based on threshold comparisons, thereby reducing current without complete cutoff.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional over-current protection method with a fixed blanking period is used, then the current can be limited during over-current conditions, but the system may cause abrupt shutdowns during transient over-current conditions in heavy-duty power tools
Solution Approach 1:
The patent applies dynamics by making the blanking period adjustable rather than fixed. The control circuit can modify the blanking period duration based on the severity and duration of the over-current condition, allowing the system to adapt between aggressive protection for severe faults and lenient operation for transient conditions, thereby preventing abrupt shutdowns during temporary over-current events while maintaining reliable protection.
Solution Approach 2:
The patent changes the parameter of the blanking period from a fixed value to an adjustable parameter. By varying the blanking period duration according to the specific over-current situation, the system can distinguish between transient over-current conditions that should be tolerated and severe over-current conditions requiring immediate shutdown, thus resolving the contradiction between protection reliability and operational smoothness.
2Reliability
If the blanking period is chosen appropriately for one specific application, then the system protection is suitable for this application, but the compatibility of the system protection in various applications is not adequate
Solution Approach 1:
The patent implements universality by designing a protection circuit with an adjustable blanking period that can be configured for different applications. The control circuit allows the blanking period to be modified according to the specific requirements of various power tool applications, enabling a single circuit design to serve multiple functions and applications effectively, thus achieving both reliable protection and broad compatibility.
Solution Approach 2:
The patent makes the blanking period dynamic and configurable, allowing the same protection circuit to adapt to different application requirements. By enabling adjustment of the blanking period parameter, the system can be optimized for light-duty applications with shorter periods or heavy-duty applications with longer periods, providing universal applicability across different power tool types.
3Device complexity
If a fixed threshold comparison method is used, then the current protection is simple to implement, but the system cannot effectively distinguish between transient and sustained over-current conditions
Solution Approach 1:
The patent applies dynamics by introducing an adjustable blanking period that allows the system to dynamically respond to over-current conditions. The control circuit monitors the over-current duration during the blanking period and can distinguish between transient conditions (where current returns to normal within the period) and sustained conditions (where current remains elevated), enabling reliable detection without excessive complexity.
Solution Approach 2:
The patent uses preliminary action by establishing a configurable blanking period before making the final over-current determination. This preliminary time window allows the system to observe whether the over-current condition is transient or sustained, providing reliable discrimination between different fault types while maintaining relatively simple circuit implementation.
Data Source
AI summary
A monitoring and control circuit comprises a sense block, a first and a second comparators, and a control module. The current sense block is coupled to a switch for generating a monitoring signal indicative of a current flowing through the switch. The first comparator coupled to the sense block is operable for comparing the monitoring signal to a first threshold and for providing a first signal according to a first comparison result between the monitoring signal and the first threshold. The second comparator coupled to the sense block is operable for comparing the monitoring signal to a second threshold and for providing a second signal according to a second comparison result between the monitoring signal and the second threshold. The control module coupled to the first comparator and the second comparator provides a control signal for controlling the switch according to the first signal and the second signal so as to adjust the current.