Isolated Output Switching Circuit for Inductive Load Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In inductive load switching applications, significant noise is introduced when the local ground 'flies' negative, causing disruptions across multiple channels due to inductive flyback voltages, which existing technologies fail to adequately isolate, leading to noise coupling between channels.
Innovation Solution
An isolated output switching circuit that employs a gate pull-down circuit to activate and deactivate the output switching device by clamping the control input node to the output voltage level, rather than pulling it to a common ground, and utilizes smaller transistors with lower breakdown voltages, along with a slope control circuit to manage the rise and fall times of control signals, thereby reducing noise and conserving semiconductor real estate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If external resistor and external diode are used to isolate local ground from global ground, then noise coupling between channels is reduced, but device complexity and external component count increase
Solution Approach 1:
The patent extracts the ground isolation function from external components (resistor and diode) and implements it internally using a dedicated isolation circuit integrated into the controller chip. This internal isolation circuit actively manages the local ground potential, eliminating the need for external isolation components while maintaining noise reduction between channels.
Solution Approach 2:
The patent introduces an intermediary isolation circuit between the local ground and global ground that actively manages potential differences. This intermediary circuit includes transistors and control logic that regulate the connection between ground domains, preventing noise coupling while allowing controlled current flow, thus replacing passive external components with an active internal mechanism.
2Object-affected harmful factors
If larger transistors with higher breakdown voltages are used in the gate pull-down circuit, then noise isolation is improved, but semiconductor real estate and cost increase
Solution Approach 1:
The patent changes the voltage reference parameter for the gate pull-down circuit from a fixed ground reference to a dynamic reference tied to the output voltage level. By clamping the control input node to the output voltage level rather than to ground, the circuit maintains adequate voltage headroom for noise isolation while allowing the use of smaller transistors with lower breakdown voltages, thus reducing semiconductor area.
Solution Approach 2:
The patent makes the reference voltage for the gate pull-down circuit dynamic rather than static. The control input node is clamped to follow the output voltage level, which varies during operation. This dynamic adjustment allows the transistor size to be optimized for the actual voltage differential experienced during switching, rather than being oversized to handle the maximum possible voltage swing to ground.
Data Source
AI summary
A semiconductor device includes an output switching device having an input node, an output node, and a control input node. The control input node enables an input voltage applied to the input node to be switched to the output node. A gate pull-down circuit controls the control input node of the output switching device in response to at least one control signal. The gate pull-down circuit activates the output switching device by raising the voltage level of the control input node above the voltage level of the output node and deactivates the output switching device by clamping the control input node to the voltage level of the output node. A gate pull-up circuit receives an enable signal and generates the at least one control signal to the gate pull-down circuit in response to the enable signal.