Power Switching Control Device Grounding for Noise Immunity
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Solution Overview
Problem
Existing power switching control devices for electric systems, such as ignition devices for internal combustion engines, face issues with erroneous overheating detection due to electromagnetic noise affecting the temperature sensing circuits, leading to unnecessary shutdowns of the semiconductor switching elements even when they are within normal temperature ranges.
Innovation Solution
A power switching control device is designed with a switching IC and a control circuit IC connected by bonding wires, where a conductive layer grounds the control circuit IC, stabilizing its substrate potential and reducing the impact of electromagnetic noise on temperature sensing, thereby accurately detecting overheating and preventing false triggers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the control circuit IC is connected to the switching IC by bonding wires, then the device can be constructed with separate ICs for flexibility, but electromagnetic noise causes LC resonance that leads to erroneous overheating detection
Solution Approach 1:
A conductive layer is introduced as an intermediary between the control circuit IC and the bonding wires. This conductive layer acts as a shield that intercepts electromagnetic noise before it can couple with the bonding wires and cause LC resonance, thereby protecting the temperature detection circuit while maintaining the separate IC construction
Solution Approach 2:
The conductive layer creates an electromagnetic shielded environment around the control circuit IC, analogous to creating an inert atmosphere. This shielded environment prevents external electromagnetic noise from interfering with the sensitive temperature detection circuits, ensuring accurate overheating detection
2Ease of manufacture
If bonding wires are used to connect switching IC and control circuit IC, then manufacturing is simplified, but inductive and capacitive components in wires cause electromagnetic noise and LC resonance
Solution Approach 1:
The conductive layer serves as a mediator between the bonding wires and the control circuit IC. It provides a low-impedance path to ground for electromagnetic noise, preventing the noise from coupling into the sensitive detection circuits while maintaining the simple wire-based connection structure
Solution Approach 2:
The harmful electromagnetic noise is extracted and directed to ground through the conductive layer, separating it from the signal paths. This allows the bonding wires to remain simple connectors while their associated electromagnetic interference is actively managed and removed from the sensitive circuits
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 erroneous overheating detection and subsequent shutdowns of the semiconductor switching elements, ensuring reliable operation of the ignition device even under electromagnetic noise conditions, maintaining normal spark discharge functionality.
Implementation Method 1
the IGBT temperature may be detected based on the temperature characteristic of diodes formed in a switching integrated circuit (IC), in which the IGBT is formed. That is, this method is based on the forward voltage drop of diodes varies with temperature.
Implementation Method 2
This construction is likely to be affected by electromagnetic noise, because the wires have inductive components (L) and capacitive components (c) are formed between the wires and the frame, etc. The electromagnetic noise causes LC resonance with the L components and the C components
Data Source
AI summary
A power switching control device for electric systems such as an ignition device for internal combustion engines has a control circuit IC and a switching IC. A temperature sensor is provided in the switching IC. The control circuit IC is joined to a grounding terminal through a conductive layer provided therebetween. Thus, the substrate potential of the control circuit IC is stabilized to the ground potential so that the temperature sensor is prohibited to operate erroneously due to electromagnetic noise.