SSD Command Scheduling to Reduce Peak Current Spikes

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Solution Overview

Problem

Solid-state drives (SSDs) face challenges in managing peak current demands and current surges due to simultaneous operations across multiple channels, leading to increased power consumption and signal integrity issues, which existing solutions like timing delays and channel restrictions do not adequately address.

Innovation Solution

The method involves scheduling commands based on current consumption profiles using look-up tables to optimize the timing of command initiation, reducing peak current spikes and surges by analyzing and selecting the appropriate look-up table based on the current profiles of ongoing and potential commands.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple commands are executed simultaneously across multiple channels to improve productivity, then the processing throughput increases, but peak current demands and current surges increase causing power consumption issues and signal integrity problems

Engineering Contradiction:

Improvecommand processing throughputVSAvoidpeak current demand

Core Design Contradiction:

ProductivityVSPower

Solution Approach 1:

The system dynamically adjusts command scheduling based on real-time current consumption profiles. The controller monitors ongoing commands and adaptively schedules new commands to avoid overlapping high-current periods, making the command execution pattern flexible rather than fixed to achieve both high throughput and controlled peak current

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the timing parameters of command execution based on current consumption characteristics. By analyzing current profiles and adjusting command start times, the system modifies execution parameters to distribute peak current demands across different time slots while maintaining overall productivity

Inventive Principle:

Principle #35Parameter changes

2Power

If timing delays are applied to bus transitions to reduce simultaneous current spikes, then peak current demands are reduced, but command processing time increases and productivity decreases

Engineering Contradiction:

Improvepeak current demandVSAvoidcommand processing time

Core Design Contradiction:

PowerVSLoss of time

Solution Approach 1:

The system performs preliminary analysis of current consumption profiles before scheduling commands. By pre-characterizing the current signatures of different command types and their temporal patterns, the controller can proactively schedule commands to avoid current surge overlaps without introducing unnecessary delays

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback from ongoing command current profiles to adjust scheduling decisions. The controller continuously monitors actual current consumption and uses this information to optimize the timing of subsequent commands, creating a closed-loop system that minimizes processing time while controlling peak current

Inventive Principle:

Principle #23Feedback

3Power

If channel restrictions are imposed to limit simultaneous operations, then current surges are reduced, but the number of parallel operations decreases and productivity is reduced

Engineering Contradiction:

Improvecurrent surge magnitudeVSAvoidparallel command execution

Core Design Contradiction:

PowerVSProductivity

Solution Approach 1:

The system segments the command execution timeline into distinct phases based on current consumption patterns. By dividing the operation schedule into segments with different current profiles and scheduling commands appropriately within and across these segments, the system maintains parallel execution capability while controlling current surges through temporal organization rather than channel limitation

Inventive Principle:

Principle #1Segmentation

4Power

If larger bulk capacitors are used to meet peak current demands, then current surge capacity increases, but device complexity and cost increase

Engineering Contradiction:

Improvepeak current supply capacityVSAvoidcapacitor size and configuration

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The system converts the potentially harmful effect of current surges into a scheduling constraint that optimizes overall system performance. By treating current surge avoidance as a scheduling objective rather than a power supply limitation, the system eliminates the need for oversized capacitors while actually improving power efficiency through intelligent command timing

Inventive Principle:

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

Data Source

PatentUS10120817B2Device and method for scheduling commands in a solid state drive to reduce peak power consumption levels

Publication Date: 2018.11.06 KIOXIA CORP

AI summary

The current consumed by flash memory devices on the channels of a solid-state drive (SSD) device will be in the form of a time varying waveform, characterized mainly by the types of commands being processed, and are often in the form of periods of constant levels interspersed with very short high current peaks or spikes. When multiple commands are being processed, significant high current peak demands and current surges can occur. The invention described herein is a device and method for scheduling commands to be processed in order to reduce the size of peak current demands and current surges. According to one embodiment of the invention, the device and method for scheduling a command uses look-up tables to determine the time to initiate the processing of the command by the flash memory devices.