Switching Circuit Topology for Negative Current Blocking
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Solution Overview
Problem
Existing switching devices face challenges in preventing negative currents, which can lead to latch-ups and operational issues, especially in high-current applications like vehicle onboard systems.
Innovation Solution
A negative current prevention circuit is introduced, comprising a P-channel MISFET and a diode connected between the input electrode and the control circuit, along with a resistor to limit current, effectively preventing negative currents and reducing voltage drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional switching device is used without a negative current prevention circuit, then the device structure remains simple, but negative currents can occur causing latch-ups and operational failures
Solution Approach 1:
The patent introduces a P-channel MISFET as an intermediary component between the input electrode and control circuit. This intermediary element specifically prevents negative currents from reaching the control circuit while allowing normal positive currents to pass through, thereby protecting the system without requiring complete redesign of the existing switching device architecture.
Solution Approach 2:
The negative current prevention circuit is designed to preemptively block negative currents before they can cause latch-ups or operational failures. By placing the P-channel MISFET in advance in the current path, the system prevents harmful negative currents from occurring in the first place, rather than responding to failures after they happen.
2Reliability
If the P-channel MISFET back gate is connected to the N-type semiconductor substrate, then the device structure is simplified, but negative currents cannot be effectively prevented
Solution Approach 1:
The patent segments the gate control function by separating the back gate connection from the main substrate. Instead of directly connecting the back gate to the N-type semiconductor substrate, the invention introduces an independent connection path that allows the back gate to be controlled separately, enabling effective negative current prevention while maintaining structural clarity.
Solution Approach 2:
The patent applies different connection qualities to different parts of the MISFET structure. The back gate is given a specific independent connection that differs from the main substrate connection, creating localized control capability. This local quality differentiation enables the back gate to specifically prevent negative currents without affecting the overall device operation.
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 proposed solution effectively prevents negative currents, reduces voltage drops, and enhances the operational reliability of switching devices in high-current applications, such as vehicle onboard systems.
Implementation Method 1
a P-channel MISFET configured to be connected, with its drain toward the input electrode and its source and back gate both toward the control circuit, between the input electrode and the control circuit
Implementation Method 2
a diode configured to be connected, with its anode toward the input electrode and its cathode toward the control circuit, between the input electrode and the control circuit
Implementation Method 3
along with a resistor to limit current
Data Source
AI summary
A switching device includes: an N-type semiconductor substrate; a power MISFET having the N-type semiconductor substrate as its drain; an input electrode receiving an input signal; a control circuit generating a gate control signal for the power MISFET according to the input signal; and a negative current prevention circuit provided between the input electrode and the control circuit. The negative current prevention circuit includes: a P-channel MISFET connected, with its drain toward the input electrode and its source and back gate toward the control circuit, between the input electrode and the control circuit, with its gate fed with a fixed potential, with the potential at its back gate separated from the potential of the N-type semiconductor substrate; and a diode connected, with its anode toward the input electrode and its cathode toward the control circuit, between the input electrode and the control circuit.