Power Source Switching Circuit for Seamless Backup Transfer
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Solution Overview
Problem
Conventional methods for switching between primary and backup power sources in electronic circuits often result in power interruptions, voltage level limitations, and slow response times due to mechanical relays or diode-OR components, which fail to ensure continuous operation.
Innovation Solution
A circuit utilizing power field effect transistors (FETs) and a dual ideal diode-OR controller, coupled with an opto-isolator and microcontroller, to smoothly and quickly switch between primary and backup power sources without interrupting the load, using configurable voltage thresholds to prevent voltage and current transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical relays are used to switch between power sources, then switching function is achieved, but power interruptions and slow response times occur
Solution Approach 1:
The patent replaces mechanical relays with solid-state power FETs (field effect transistors) to eliminate mechanical switching limitations. The power FETs provide contactless switching with microsecond response times, eliminating the slow mechanical contact making/breaking process while ensuring continuous power delivery to the load during source transitions.
Solution Approach 2:
The patent introduces an opto-isolator as an intermediary device between the control circuit and the power FET gate. This opto-isolator provides electrical isolation while transmitting control signals, allowing the microcontroller to safely control high-voltage power switching without direct electrical connection, thereby improving reliability and protecting the control circuit.
2Reliability
If diode-OR components are used for power source switching, then power source selection is achieved, but voltage level limitations and high transients occur
Solution Approach 1:
The patent uses the controllable resistance characteristic of power FETs to dynamically adjust circuit parameters during switching. By controlling the gate voltage of the power FETs, the device resistance can be smoothly transitioned from low to high state, enabling soft switching that prevents voltage transients and eliminates the hard switching limitations of diode-OR components.
Solution Approach 2:
The patent replaces ideal diode-OR components with controllable power FETs managed by a dual ideal diode-OR controller. This substitution provides active control over power source selection, allowing the system to monitor voltage levels from both sources and selectively connect the appropriate source without the voltage level limitations and transient spikes inherent in passive diode-OR switching.
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 seamless switching between power sources, reducing energy spikes and ensuring continuous operation by eliminating voltage and current transients, with enhanced reliability and faster response times compared to mechanical or diode-based systems.
Implementation Method 1
an opto-isolator coupled to a control input of the first power FET and a controller coupled to the opto-isolator that selectively turns on and off the opto-isolator
Implementation Method 2
first and second power field effect transistors (FET) coupled between the second port and the third port, a third power FET coupled between the first port and the third port
Data Source
AI summary
A method for selecting a power source for a load is provided. The method includes monitoring the primary power source, when the primary power source is providing power to the load, determining if a condition of the primary power source crosses a first threshold, when the condition crosses the first threshold, turning on a first power field effect transistor to couple a back-up power source to the load through a second power field effect transistor, when the primary power source is not providing power to the load, determining if a condition of the primary power source crosses a second threshold, and when the condition crosses the second threshold, switching off the first power field effect transistor to couple the primary power source to the load through a third power field effect transistor.