Switch Mode Current Limiter Using Transmission Line Diversion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional switch mode current limiters are inefficient due to the high cost and limited capacity of free wheel diodes, which are required to handle diverted current, especially when connected to inductive circuits.
Innovation Solution
A current limiter design that uses a switch controlled by a control component to open or close based on current thresholds, with a transmission line instead of a free wheel diode to handle diverted currents, allowing for more arbitrary current strengths and lower costs, and optionally includes a capacitor, inductor, or MEMS switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a free wheel diode is used to divert current when the switch is opened, then the current path is maintained, but the device becomes expensive and has limited ability to handle intense current pulses
Solution Approach 1:
The patent changes the fundamental parameter of the current diversion component from a diode (with limited current handling capability) to a transmission line (with arbitrary current handling capability). The transmission line's characteristic impedance and physical dimensions are adjusted to accommodate intense current pulses, transforming the system's current handling parameters to resolve the contradiction between reliability and manufacturing ease.
Solution Approach 2:
The transmission line is implemented as a PCB trace or simple conductive structure that is much cheaper than a free wheel diode. While the transmission line may experience voltage spikes when the switch opens, these are manageable through proper design, making the overall system more cost-effective while maintaining sufficient reliability for the application.
2Reliability
If the switch is opened to interrupt excessive current, then current protection is achieved, but the diverted current requires expensive components with limited capacity
Solution Approach 1:
The transmission line serves multiple functions: it provides a current diversion path, acts as an impedance matching element, and can be integrated into the existing PCB structure. This multi-functionality reduces device complexity by eliminating the need for separate expensive diode components while maintaining current protection capability.
Solution Approach 2:
The transmission line acts as an intermediary between the switch and the load, providing a controlled impedance path for diverted current. This intermediary structure simplifies the overall circuit design compared to direct connections or complex protection networks, reducing device complexity while ensuring reliable current protection.
3Ease of manufacture
If a transmission line is used instead of a free wheel diode, then current handling capacity and cost are improved, but the switch opening creates voltage spikes
Solution Approach 1:
The transmission line is designed with appropriate characteristic impedance and length to cushion the voltage spike that occurs when the switch opens. By carefully selecting the transmission line parameters beforehand, the voltage reflection and overshoot are controlled to acceptable levels, preventing damage to the switch and other components while maintaining the cost and current capacity advantages.
Data Source
AI summary
A current limiter (100, 200, 400, 500, 700) comprises a switch (110) and connection means (105, 125) to a load and to a DC-voltage source. A control component (115) measures the current from a load to a DC-voltage source to the switch and controls the switch (110) to an open position if the current is above a threshold. In the closed position, the switch (110) admits current from the load to the DC-voltage source. The current limiter also comprises a transmission line (120) with a first (121) and a second (122) end. The first end (121) is connected to the input port of the switch (110), and the second end (122) is left open or connected to make the transmission line (120) connected in series with the switch (110).