Power Transfer Switch Overcurrent Protection via SCR and FET
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Solution Overview
Problem
Existing power transfer switches in semiconductor manufacturing processes face challenges in providing stable standby power without interruption, especially during short circuits, leading to increased system complexity and potential equipment damage, and require complex commutation sensing and voltage detection algorithms.
Innovation Solution
A power transfer switch design utilizing FET bidirectional switches and SCR switches connected in parallel, with a drive control unit for simultaneous or sequential switching, and optionally including a relay switch, to enable high-speed operation and prevent overcurrent damage, allowing seamless transition between main and standby power sources without requiring complex commutation sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a MOSFET is used as a power transfer switch for high-speed operation, then switching speed is improved, but the device is vulnerable to overcurrent damage during short circuit accidents
Solution Approach 1:
The patent introduces a current-limiting resistor as an intermediary component connected in series with the MOSFET. This resistor limits the peak current during short circuit accidents, protecting the MOSFET from overcurrent damage while allowing high-speed switching operation. The resistor acts as a mediator that sacrifices some current limiting capability to preserve the MOSFET's reliability.
Solution Approach 2:
The patent employs a snubber circuit (comprising a resistor and capacitor in series) connected in parallel with the MOSFET to provide beforehand cushioning. This circuit absorbs voltage spikes and limits current peaks during switching transients and short circuit conditions, protecting the MOSFET before damage can occur. The snubber circuit pre-prepares protective action to cushion against anticipated overcurrent stress.
2Reliability
If an SCR is used as a power transfer switch, then overcurrent protection is improved, but switching speed decreases due to commutation time requirements
Solution Approach 1:
The patent replaces the mechanical relay-based power transfer switch with a semiconductor-based system (MOSFET with current limiting). This substitution eliminates the need for mechanical commutation sensing and voltage detection algorithms, achieving both high-speed operation and overcurrent protection through electronic current limiting rather than mechanical switching coordination.
3Device complexity
If a relay type power transfer switch is used, then simplicity of structure is improved, but switching speed becomes slow (10 ms or more)
Solution Approach 1:
The patent replaces the mechanical relay system with a solid-state MOSFET-based power transfer switch. This substitution eliminates mechanical moving parts and commutation mechanisms, reducing switching time from 10 ms or more to microsecond-level speeds while maintaining structural simplicity through the use of basic circuit components (MOSFET, current-limiting resistor, snubber circuit).
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
Enables stable and uninterrupted power supply during unstable conditions, reducing system complexity and preventing equipment damage, with the ability to operate at high speeds and maintain power integrity even during short circuits, thus increasing the mean time between failures.
Implementation Method 1
A power transfer switch design utilizing FET bidirectional switches and SCR switches connected in parallel, with a drive control unit for simultaneous or sequential switching
Data Source
AI summary
The present invention comprises a drive control unit configured such that, when a first power supply (Vin1) is abnormal, an OFF signal is simultaneously applied to the gates of first and second semiconductor switches (Q1, Q2) of a first switching element, and at the same time, an SCR switch of a second switching element and an FET bidirectional switch are turned on in order.