Mini Circuit Breaker Using D-MOSFET Heat to Speed Overcurrent Trip
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Solution Overview
Problem
Miniature electronic components, such as microprocessors, are vulnerable to electrical stresses like overcurrent and voltage transients due to their miniaturization, leading to potential device failure, and existing circuit breakers are inadequate in responding quickly to overcurrent events.
Innovation Solution
A miniature circuit breaker design incorporating a bi-metallic switch and a depletion mode MOSFET (D MOSFET) that works together to provide rapid overcurrent protection by using the MOSFET's heat generation to trigger the bi-metallic switch, creating a fast response to overcurrent conditions and preventing overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If existing circuit breakers are used, then overcurrent protection is provided, but the response time is too slow to protect miniaturized components from electrical stresses
Solution Approach 1:
The patent combines a bi-metallic strip (thermal element) with a depletion mode MOSFET (electrical element) into a hybrid circuit breaker. The MOSFET provides rapid electrical response to overcurrent conditions by detecting current through its gate, while the bi-metallic strip provides thermal response by bending in response to heat from excessive current. This merging of thermal and electrical detection mechanisms enables both fast response time and reliable protection for miniaturized components.
2Volume of moving object
If component miniaturization is pursued, then device size is reduced, but sensitivity to electrical stresses like overcurrent and voltage transients increases
Solution Approach 1:
The circuit breaker is designed to detect overcurrent conditions before they can cause damage to miniaturized components. The depletion mode MOSFET immediately responds to excessive current by adjusting its conductivity, and the bi-metallic strip prepares to open the circuit if the overcurrent persists. This preliminary action prevents electrical stresses from reaching levels that would harm sensitive miniaturized components.
3Reliability
If a bi-metallic strip alone is used, then thermal response to overcurrent is provided, but the response time is insufficient for rapid protection
Solution Approach 1:
The depletion mode MOSFET acts as an intermediary between the bi-metallic strip and the circuit being protected. It provides immediate electrical detection and response to overcurrent conditions, triggering or assisting the bi-metallic strip's thermal response. This intermediary element bridges the gap between slow thermal response and the need for rapid protection, enabling the system to trip quickly while maintaining reliable thermal-based overcurrent detection.
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 combination of the bi-metallic switch and D MOSFET significantly reduces the time to trip in response to overcurrent events, effectively protecting downstream components from damage by quickly cutting off current and preventing overheating.
Implementation Method 1
The bi-metallic strip includes an elongated metal strip and a metal winding wrapped around the strip. The elongated metal strip bends if the current rating of the miniature circuit breaker is exceeded.
Implementation Method 2
a depletion mode field effect transistor (D MOSFET) that works together to provide rapid overcurrent protection by using the MOSFET's heat generation to trigger the bi-metallic switch
Data Source
AI summary
A miniature circuit breaker for providing short circuit and overload protection is disclosed herein. The miniature circuit breaker features a field effect transistor (FET), which may be a depletion mode metal oxide semiconductor FET (D MOSFET), a junction field-effect transistor (JFET), or a silicon carbide JFET, the FET being connected to a bi-metallic switch, where the bi-metallic switch acts as a temperature sensing circuit breaker. In combination, the D MOSFET and bi-metallic switch are able to limit current to downstream circuit components, thus protecting the components from damage.