ORing FET Voltage-Difference Control to Prevent False Turn-Off
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Solution Overview
Problem
Conventional ORing FET control circuits falsely trigger the ORing FET to turn off due to voltage drops caused by reasons other than internal short circuits, leading to frequent on-off cycles.
Innovation Solution
An ORing FET control circuit and method that determine whether to turn off the ORing FET based on the voltage across the ORing FET, using a comparator and resistors to set a threshold, ensuring accurate detection of internal short circuits and avoiding false triggers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the conventional ORing FET control circuit uses a transistor to detect voltage drops, then the circuit structure is simple, but the ORing FET is falsely triggered to turn off when voltage drops occur for reasons other than internal short circuits
Solution Approach 1:
The patent changes the detection parameter from simple voltage level comparison (conventional method) to voltage difference comparison across the ORing FET. By measuring the voltage difference between the input terminal and output terminal of the ORing FET, the circuit can distinguish between normal voltage drops (which do not cause large voltage differences across the FET) and internal short circuits (which cause large voltage differences), thereby eliminating false triggers while maintaining circuit simplicity
Solution Approach 2:
The patent introduces a voltage difference detection mechanism as an intermediary between the voltage drop detection and the ORing FET control. Instead of directly responding to voltage drops, the circuit uses the voltage difference across the FET as an intermediate parameter to determine whether to trigger turn-off, providing more accurate fault detection without complicating the overall circuit structure
2Speed
If the ORing FET turns off immediately upon voltage drop detection, then the response speed is fast, but the operation stability deteriorates due to frequent on-off cycles
Solution Approach 1:
The patent changes the control parameter from absolute voltage level to voltage difference across the ORing FET. This parameter change enables the circuit to maintain fast response to actual faults (internal short circuits) while ignoring normal voltage fluctuations, thereby achieving both fast response speed and operation stability by eliminating unnecessary on-off cycles
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 ensures immediate turn-off of the ORing FET during internal short circuits while preventing false triggers due to other voltage drops, thereby stabilizing the operation of power supply units.
Implementation Method 1
A positive input terminal and a negative input terminal of the comparator are electrically connected to the input voltage and the output voltage respectively
Data Source
AI summary
An ORing FET control circuit and method are provided. The circuit includes an ORing FET, a comparator, first, second and third resistors, a first capacitor, a diode and a driving unit. The positive and negative input terminals of the comparator are electrically connected to the input and output voltages. The first resistor, the second resistor, the first capacitor, and the third resistor are electrically connected in series between a reference voltage and a ground terminal sequentially. The reference voltage is lower than a voltage at the positive input terminal. When the input voltage is lower than the output voltage, if a voltage across the ORing FET is larger than a threshold, the comparator outputs a driving signal at low level, and correspondingly the driving unit turns off the ORing FET. The threshold depends on resistances of the first and second resistors.