Power FET RF Detection Circuit for Unintended Turn-On Prevention
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Solution Overview
Problem
Circuits in vehicles are susceptible to radio frequency (RF) interference, which can cause unintended operation or damage due to RF signals, particularly during transit or due to cable length, leading to issues like thermal runaway and incorrect signal values.
Innovation Solution
A circuit architecture that includes a gate pull-down circuit, a pull-down bias circuit, and an RF detector to detect RF interference and create a low impedance path between the gate and source terminals of a power FET, preventing unintended turn-on and mitigating RF interference effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a power FET is used to control high power loads, then the power handling capability is improved, but the circuit becomes susceptible to RF interference causing unintended operation
Solution Approach 1:
The patent introduces an RF detector circuit as an intermediary component that monitors the source terminal of the power FET for RF signals. When RF interference is detected, the detector activates a pull-down circuit that creates a low impedance path between gate and source, effectively mediating the harmful RF effects before they can cause unintended FET operation.
Solution Approach 2:
The circuit applies preliminary anti-action by proactively detecting RF signals before they can trigger unintended power FET turn-on. The RF detector continuously monitors for interference and preemptively activates the discharge path to counteract potential harmful effects, preventing thermal runaway and incorrect signal values before they occur.
2Object-affected harmful factors
If the gate pull-down circuit is activated to create low impedance path, then RF interference protection is improved, but the circuit complexity increases
Solution Approach 1:
The gate pull-down circuit components are pre-configured and ready in the circuit architecture, but remain inactive during normal operation. The RF detector triggers activation of this pre-prepared protection mechanism only when needed, providing RF protection without requiring the circuit to be permanently complex or active.
Solution Approach 2:
The protection function is extracted as a separate, independently controllable subsystem with its own switchable activation. The RF detector and pull-down circuit operate as a distinct protection module that can be engaged or disengaged based on RF conditions, rather than being permanently integrated into the normal power FET control path.
3Reliability
If the RF detector continuously monitors the source terminal, then detection reliability is improved, but the energy consumption increases
Solution Approach 1:
The RF detector employs periodic monitoring rather than continuous active detection. The circuit uses passive RF signal detection that activates the pull-down protection only during periodic sampling when RF signals are present, reducing average energy consumption while maintaining reliable detection capability when interference occurs.
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 effectively prevents unintended operation and damage by creating a discharge path, ensuring the power FET operates as intended and maintaining signal integrity even under RF interference conditions, with the ability to handle RF signals up to 30 dBm across various frequencies.
Implementation Method 1
a first capacitor having a first terminal coupled to the source terminal and a second terminal coupled to the gate terminal
Implementation Method 2
The first transistor has a drain terminal coupled to the second node, a source terminal coupled to a ground node... effectively prevents unintended operation and damage by creating a discharge path
Data Source
AI summary
In some examples, the disclosure includes a circuit including a power field effect transistor (FET), a gate pull-down circuit, a pull-down bias circuit, and a radio frequency (RF) detector coupled to the source terminal of the power FET and the pull-down bias circuit. In an example, the RF detector circuit is configured to detect a presence of an alternating current signal at a source terminal of the power FET when the power FET is in a non-conductive state and control the pull-down bias circuit to bias the gate pull-down circuit to create a low impedance path between a gate terminal of the power FET and the source terminal of the power FET when the power FET is in the non-conductive state and the alternating current signal is present at the source terminal of the power FET.