Stochastic Semiconductor Neuron Circuit for Low Power Neuromorphic Systems

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Solution Overview

Problem

Silicon neuron circuits face challenges in achieving high integration, low power consumption, and temperature stability, particularly in analog circuits used in neuromorphic systems, where manufacturing errors and temperature variations pose significant issues.

Innovation Solution

A semiconductor device incorporating stochastic circuits with a sigmoid function-like input/output characteristic, utilizing CMOS configuration and noise introduction units to control output currents probabilistically, thereby reducing noise and temperature dependency while enhancing integration and power efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If analog circuits are used to achieve high integration and low power consumption, then power efficiency and integration density improve, but temperature stability and manufacturing precision deteriorate

Engineering Contradiction:
Improvepower consumptionVSAvoidtemperature stability
Core Design Contradiction:
Use of energy by moving objectVSReliability

Solution Approach 1:

The circuit is divided into multiple identical stochastic neuron circuits that can be integrated in large numbers on a single chip. Each neuron circuit operates independently with digital-like binary states, allowing parallel processing while maintaining temperature stability through the collective behavior of many identical units.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent replaces traditional analog continuous voltage systems with a digital-like stochastic system using binary states (0 or 1) and random noise. This substitution of continuous analog signals with discrete digital states improves temperature stability while maintaining low power consumption characteristics.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If analog circuits are used to achieve high integration, then integration density improves, but manufacturing precision and robustness against variations worsen

Engineering Contradiction:
Improveintegration densityVSAvoidmanufacturing variation robustness
Core Design Contradiction:
ProductivityVSManufacturing precision

Solution Approach 1:

The patent replaces sensitive analog continuous circuits with digital-like stochastic circuits that use binary states and random noise. This digitalization makes the circuits much more robust against manufacturing variations while enabling high integration density through standard CMOS fabrication processes.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the operating parameters from continuous analog voltages to discrete binary states (0 or 1) with stochastic transitions. This parameter change from continuous to discrete domains fundamentally improves robustness against manufacturing variations while maintaining high integration capability.

Inventive Principle:
Principle #35Parameter changes

3Adaptability or versatility

If traditional neuron circuits are used, then basic neural function is achieved, but temperature dependency and power consumption increase

Engineering Contradiction:
Improveneural function capabilityVSAvoidpower consumption
Core Design Contradiction:
Adaptability or versatilityVSUse of energy by stationary object

Solution Approach 1:

The stochastic neuron circuits use periodic random noise injection to trigger state transitions between 0 and 1. This periodic stochastic action replaces continuous analog operation, reducing average power consumption while maintaining neural computational capabilities through event-driven operation.

Inventive Principle:
Principle #19Periodic action

Data Source

PatentUS11468248B2Semiconductor device
Publication Date: 2022.10.11 NEC CORP
  • US11468248B2 patent drawing
  • US11468248B2 patent drawing
  • US11468248B2 patent drawing

AI summary

Input unit to which a voltage is applied, current output unit that outputs a high level current or a low level current in response to the voltage applied to input unit, and stochastic circuit unit that, in response to the voltage applied to input unit, changes a probability that the high level current or the low level current is output from current output unit, in accordance with a sigmoid function used in a mathematical model of a neural activity are included.