Floating Switch Unit for Airbag Control Chip Area Reduction

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Solution Overview

Problem

The existing floating switch unit in airbag control units requires large MOS transistors with high breakdown voltage, making it difficult to downsize semiconductor integrated circuits and increasing manufacturing costs, and the current requirements vary with the number and type of connected slaves, further increasing chip area and ON-resistance.

Innovation Solution

A semiconductor integrated circuit device with a reduced number of switches in the switching circuit, utilizing a configuration of Hi-side and Lo-side switch portions connected to electrostatic capacitance elements and buses, along with P-channel and N-channel MOS transistors, level shift units, and Zener diodes to manage power supply and control signals efficiently.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a floating switch unit with high breakdown voltage MOS transistors is used to maintain communication during short-circuit conditions, then reliability is improved, but device area and manufacturing cost increase

Engineering Contradiction:

Improvecommunication continuity during short-circuitVSAvoidchip area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The bus interface is divided into multiple operational modes (normal mode, bus A short-circuit mode, bus B short-circuit mode) with dedicated switching circuits for each mode. This segmentation allows each switching circuit to be optimized for its specific function, reducing the overall transistor size requirements compared to a single high-breakdown-voltage transistor handling all scenarios.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the breakdown voltage parameter of MOS transistors based on operational mode. In normal operation, lower breakdown voltage transistors are used. Only during short-circuit conditions do higher breakdown voltage transistors activate, and even then, the patent uses multiple lower-voltage transistors in parallel rather than a single high-voltage transistor, reducing overall area.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the current value is increased to enable connection of multiple slaves to the bus, then adaptability is improved, but chip area and ON-resistance decrease

Engineering Contradiction:

Improvenumber of connected slavesVSAvoidchip area

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The switching circuits dynamically adjust their operation based on the number and type of slaves connected to the bus. The control unit monitors bus conditions and activates appropriate switching circuits, allowing the system to scale current capacity adaptively rather than being designed for maximum capacity from the start, thus reducing chip area.

Inventive Principle:

Principle #15Dynamics

3Power

If the current value is increased to decrease ON-resistance of the switch, then power delivery capability is improved, but chip area increases

Engineering Contradiction:

Improvepower supply capabilityVSAvoidchip area

Core Design Contradiction:

PowerVSArea of stationary object

Solution Approach 1:

Multiple switching circuits are merged and coordinated to provide the required power supply capability. Instead of using a single large transistor with high current capacity, the patent combines several smaller transistors working together, each handling a portion of the total current, thereby achieving the same power delivery capability with reduced individual transistor sizes and overall chip area.

Inventive Principle:

Principle #5Merging (Combining)

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 allows for downsizing of semiconductor integrated circuits, increases reliability, and reduces manufacturing costs by minimizing the number of switches and ON-resistance, while maintaining reliable power supply and communication even in short-circuit conditions.

Implementation Method 1

a first electrostatic capacitance element CS and a second electrostatic capacitance element CH

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

a switch which charges a first electrostatic capacitance from a battery power supply, a switch which provides the power supply from the first electrostatic capacitance

Methodology Applied

Scientific EffectElectrical Conduction: Conduction (electrical)

Implementation Method 3

Zener diodes to manage power supply and control signals efficiently

Methodology Applied

Scientific EffectZener breakdown: Avalanche Breakdown

Data Source

PatentUS8093762B2Semiconductor integrated circuit device

Publication Date: 2012.01.10 RENESAS ELECTRONICS CORP

AI summary

In a power phase period when in normal operation, switch portions SW2H and SW2L and switch portions SW3H and SW3L are turned ON, respectively, and switch portions SW1H and SW1L are turned OFF. And floating power supply is provided from an electrostatic capacitance element CS to buses A and B, a floating control circuit 4, a transmitter circuit 5, and a receiver circuit 6, respectively. In a data phase period, the switch portions SW1H and SW1L are turned ON, and the switch portions SW2H, SW2L, SW3H, and SW3L are turned OFF. By that manner, the electrostatic capacitance element CS is charged by the power supply of a battery B, and an electrostatic capacitance element CH provides the floating power supply to the floating control circuit 4, the transmitter circuit 5, and the receiver circuit 6, respectively. By this manner, a floating switch unit 7 in which the number of the switch portions is considerably reduced can be configured.