PASR DRAM Burst Buffer for Low-Power Image Capture
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Solution Overview
Problem
Camera systems, especially security cameras, face challenges in capturing pre-event video due to long shutter lag and high power consumption, limiting the capacity of low-power memory buffers and requiring continuous operation for event detection.
Innovation Solution
A low-power image capture device utilizing a combination of static random-access memory (SRAM) and partial-array self-refresh (PASR) dynamic random-access memory (DRAM) as a first-in, first-out image frame buffer, where images are stored in SRAM during low-power mode and transferred in bursts to PASR DRAM, which is powered only during image bursts and activation events, allowing for efficient power management and extended preview capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If SRAM is used for image buffer to enable low-power operation, then power consumption is reduced, but storage capacity is limited and cost increases
Solution Approach 1:
The patent divides the image buffer into two segments: a small SRAM buffer for low-power operation and a larger DRAM buffer for extended storage capacity. The SRAM handles active frame buffering while the DRAM provides additional preview frame storage, resolving the contradiction between low power consumption and large storage capacity.
Solution Approach 2:
The patent combines SRAM and DRAM buffers into a unified FIFO image frame buffer system. The SRAM and DRAM work together as a single buffer hierarchy, allowing the system to achieve both low-power operation (from SRAM) and large storage capacity (from DRAM) simultaneously.
2Quantity of substance
If DRAM is used for image buffer to increase storage capacity, then storage capacity increases, but power consumption increases
Solution Approach 1:
The patent implements periodic bursting transfers from SRAM to DRAM instead of continuous operation. The DRAM buffer is activated and receives data in periodic bursts, then enters a low-power state, significantly reducing average power consumption while maintaining large storage capacity for preview frames.
Solution Approach 2:
The patent applies different operational modes to different parts of the buffer system: SRAM operates continuously at low power for active frames, while DRAM operates in periodic burst mode for preview frames. This local differentiation allows each component to optimize its power consumption based on its specific function.
3Quantity of substance
If camera operates continually to capture pre-event video, then preview capacity increases, but power consumption increases
Solution Approach 1:
The patent implements preliminary action by continuously capturing and buffering preview frames in the SRAM/DRAM buffer hierarchy before activation events occur. This allows pre-event video capture without continuous full-system operation, as only the minimal buffer writing function runs continuously at low power.
Solution Approach 2:
The patent implements dynamic power management where the camera system transitions between different operational states: a low-power standby state where only the image sensor and buffer writing operate, and a full-power active state when events are detected. This dynamic operation allows preview capacity while minimizing average power consumption.
Data Source
AI summary
A low-power image capture device includes a first image buffer in SRAM coupled to receive images from an image sensor, and a second image buffer receiving images transferred in bursts from the first image buffer, the second image buffer implemented in PASR DRAM, the image buffers together operating as a first-in, first-out, (FIFO) buffer. The device includes an activation detector. The PASR DRAM is powered while receiving bursts of images from the first image buffer, and when the image capture device is in the activated mode; and in ultra-low power PASR mode otherwise. A method includes capturing images into the first image buffer, transferring the images in bursts into a second image buffer in PASR DRAM powered while receiving the images in bursts, the PASR DRAM otherwise in ultra-low power PASR mode; and, upon activating, an image processor receiving images from the second image buffer.