Multi-Source ASIC Supply Circuit With PMOS Star-Point Switching

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Solution Overview

Problem

Existing electrical circuits for supplying application-specific integrated circuits (ASICs) in motor vehicle control units face challenges in efficiently switching between different voltage sources during varying operating states, leading to potential undervoltage and short circuits due to the finite switching time of MOS transistors and power loss in diodes.

Innovation Solution

The proposed electrical circuit connects multiple voltage sources to a common star point via PMOS transistors operating in the weak inversion region, allowing for smooth transitions and enabling each voltage source to be independently enabled or disabled, eliminating the need for comparators and reducing voltage drops.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If diodes are used to connect voltage sources to a common star point, then the circuit structure is simple, but the voltage at the star point is always one diode forward voltage below the highest available voltage source, causing undervoltage in the ASIC

Engineering Contradiction:

Improvecircuit structureVSAvoidvoltage availability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent changes the electrical parameter (voltage drop) by replacing diodes with PMOS transistors operating in weak inversion region, reducing the voltage drop from typical diode forward voltage (0.7V) to a much smaller value, thereby ensuring the ASIC receives sufficient voltage even when battery voltage drops during engine starting

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses PMOS transistors as a functional copy/alternative to diodes, achieving the same one-way current conduction function while improving the voltage drop characteristic. The PMOS transistors replicate the protective function of diodes against reverse current while maintaining higher voltage at the star point

Inventive Principle:

Principle #26Copying

2Reliability

If MOS transistors with comparators are used for switching between voltage sources, then availability is maintained during voltage drops, but the finite switching time and comparator delay can cause brief interruptions or short circuits between sources

Engineering Contradiction:

Improveavailability during voltage dropsVSAvoidswitching time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent extracts and removes the comparator component from the circuit, eliminating the time delay associated with voltage comparison and decision-making. The PMOS transistors directly respond to voltage differences without requiring external comparison logic, thereby eliminating switching delays and preventing brief interruptions or short circuits

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The PMOS transistors automatically respond to voltage differences between sources and the star point without external control signals. When a voltage source exceeds the star point voltage by more than the threshold voltage, the corresponding PMOS transistor automatically conducts, providing self-regulating operation without comparators or control logic

Inventive Principle:

Principle #25Self-service

3Device complexity

If diodes are used to protect against reverse current, then the circuit is simple, but power loss is converted in the diodes

Engineering Contradiction:

Improvecircuit structureVSAvoidpower loss in diodes

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the typically harmful effect of voltage drop in protection devices into a beneficial feature by using PMOS transistors with very low voltage drop in weak inversion region. This minimal voltage drop reduces power loss while maintaining the protective function against reverse current, turning what was previously a significant energy loss into a negligible effect

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 solution ensures stable power supply to ASICs by minimizing voltage drops and preventing short circuits, allowing for seamless switching between voltage sources and maintaining functionality during voltage dips, thereby enhancing the reliability and efficiency of the power supply.

Implementation Method 1

PMOS transistors in a first subcircuit for supplying a first star point with a first output voltage from different voltage sources in a weak inversion region

Methodology Applied

Scientific EffectWeak inversion region operation:

Data Source

PatentEP3741020B1Electrical circuit for supplying a consumer from different power sources

Publication Date: 2023.10.18 ROBERT BOSCH GMBH

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AI summary

The invention relates to an electrical circuit for supplying a consumer from different power sources (VSUP1, VSUP2, VSUP3), comprising a first partial circuit (X) for standby operation of the consumer and a second partial circuit (Y) for normal operation of the consumer.