Smart Electronic Switch With Multi-Time Constant Filter
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Solution Overview
Problem
Conventional fuses and electronic fuses struggle to effectively manage dynamic electric loads, as they are designed for constant thermal loads, leading to potential overheating and damage when current exceeds nominal levels due to their fixed time-current characteristics.
Innovation Solution
An integrated circuit with a power transistor and current sensing circuit that generates a protection signal using a filter with multiple time constants, allowing for adaptive time-current characteristics to match the load's dynamic behavior, thereby preventing overheating and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fuses or electronic fuses with fixed time-current characteristics are used, then they provide over-current protection for constant thermal loads, but they cannot effectively manage dynamic electric loads and may cause overheating or damage when current exceeds nominal levels
Solution Approach 1:
The patent applies the dynamics principle by implementing a monitor circuit with a filter that has two or more different time constants. This allows the electronic fuse to dynamically adjust its response characteristics based on the load conditions. The filter can selectively emphasize either instantaneous current values or time-averaged current values depending on the situation, enabling the system to adapt to both dynamic and constant thermal loads effectively.
2Device complexity
If the electronic fuse uses a single time constant filter, then the circuit is simple, but it cannot properly handle both instantaneous over-current events and sustained thermal loading conditions
Solution Approach 1:
The patent applies the segmentation principle by dividing the filtering function into multiple parallel paths, each with a different time constant. Instead of using a single complex filter, the system segments the current signal processing into multiple filtering channels that can be selectively combined. This approach maintains relative circuit simplicity while achieving reliable protection for both instantaneous and sustained over-current conditions.
3Temperature
If the electronic fuse triggers disconnection quickly on current exceedance, then it prevents cable overheating, but it may cause unnecessary disconnections for transient current spikes in dynamic loads
Solution Approach 1:
The patent applies the feedback principle by using the monitor circuit to continuously compare the filtered current signal against threshold values and provide feedback control. The dual time constant filter provides differentiated feedback responses: one path responds quickly to immediate threats while another path provides context about sustained conditions. This feedback mechanism allows the system to distinguish between dangerous thermal loading and benign transient spikes, maintaining cable temperature control while avoiding unnecessary disconnections.
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 enables the smart electronic switch to dynamically adjust its operation based on the load's current characteristics, effectively protecting the wire and load from overheating and damage by switching off when necessary, enhancing the safety and reliability of electric installations.
Implementation Method 1
The filter has a transfer characteristic with two or more time constants
Implementation Method 2
enabling a load current path from a supply pin and an output pin by switching-on a power transistor
Implementation Method 3
a current sensing circuit coupled to the power transistor and configured to generate a current sense signal indicative of a load current passing through the power transistor
Data Source
AI summary
An integrated circuit that may be employed as a smart switch is described herein. In accordance with one embodiment the integrated circuit includes a power transistor coupled between a supply pin and an output pin and a current sensing circuit coupled to the power transistor and configured to generate a current sense signal indicative of a load current passing through the power transistor. The integrated circuit further comprises a monitor circuit configured to receive the current sense signal and to provide a protection signal based on the current sense signal and a threshold value, wherein the monitor circuit includes a filter that is configured to receive a filter input signal that depends on the current sense signal. The filter has a transfer characteristic with two or more time constants.