N-Channel Power Transistor Reverse Current Cut-off
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Solution Overview
Problem
Existing semiconductor devices for electronic control units in vehicles face challenges in efficiently cutting off reverse current flow from loads to power supplies, particularly when using n-channel transistors, which can lead to increased size and loss due to parasitic diodes and forward voltage drops, while p-channel transistors offer higher on-resistance and reduced miniaturization potential.
Innovation Solution
A semiconductor device configuration incorporating an n-channel first power transistor and a second power transistor in series, along with a booster circuit and a gate discharge circuit, which charges and discharges the gate of the first power transistor to control energization and cut off reverse current flow effectively, utilizing a backflow prevention diode and a pMOS transistor to manage power supply potentials and prevent backflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If n-channel transistors are used to reduce size and loss, then device size and power loss are reduced, but reverse current cut-off capability deteriorates due to parasitic diodes
Solution Approach 1:
The relay device is segmented into two series-connected n-channel transistors (first and second transistors) instead of using a single transistor or p-channel transistor. This segmentation allows independent control of each transistor's gate, enabling the first transistor to block reverse current while the second transistor controls normal operation, thus resolving the contradiction between using n-channel transistors and achieving reverse current cut-off capability
Solution Approach 2:
A discharge circuit is introduced as an intermediary component connected to the gate of the first transistor. This discharge circuit actively removes gate charge when reverse connection is detected, ensuring the first transistor remains in cutoff state during reverse current conditions. The intermediary discharge circuit enables reliable reverse current blocking without requiring p-channel transistors or diodes
2Reliability
If p-channel transistors are used to achieve reverse current cut-off, then reverse current blocking capability is improved, but on-resistance increases and miniaturization potential is reduced
Solution Approach 1:
The invention changes the operational parameters of n-channel transistors through active gate charge management. By dynamically controlling the gate charge of the first transistor via the discharge circuit, the transistor's electrical characteristics are changed from conducting state to cutoff state during reverse connection, achieving reverse current blocking with lower on-resistance compared to p-channel transistors
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
This configuration enables efficient cut-off of reverse current flow while maintaining low loss and miniaturization, allowing for compact and efficient relay devices that reduce weight, cost, and power consumption in vehicles.
Implementation Method 1
The first gate discharge circuit discharges the gate charge of the first power transistor to the source when the potential of the negative power supply terminal is higher than the potential of the positive power supply terminal
Implementation Method 2
The first booster circuit charges the gate of the first power transistor
Data Source
AI summary
A semiconductor device and electronic control device capable of shutting off the reverse current flow from a load to a power supply is provided.The power transistor QN1 is provided between the positive power supply terminal Pi2(+) and the load-driving terminal Po2(+), and has a source and a back-gate coupled to the positive power supply terminal Pi2(+). The power transistor QN2 is provided in series with the power transistor QN1, and its sources and backgates are coupled to the load-driving terminal Po2(+). The booster CP1a charges the gates of the power transistors QN1. The gate discharge circuit DCG1a discharges the gate charge of the power transistor QN1 to the source when the potential of the negative power supply terminal Pi2(−) is higher than the potential of the positive power supply terminal Pi2(+).