Solid-State Image Pickup Device Load Transistor Voltage Control
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Solution Overview
Problem
Existing solid-state image pickup devices face challenges in reducing power consumption, particularly with analog circuits that occupy a large ratio when pixels are miniaturized, and previous techniques suffer from signal interference, slow operating speeds, and poor linearity due to nonlinear capacity of signal lines.
Innovation Solution
A solid-state image pickup device with a pixel array section and load transistors configured as source follower circuits, where a control circuit adjusts the supply voltage or current of load transistors based on the amount of light received, using a dynamic range deciding circuit to control power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If pixels are miniaturized, then the device can achieve higher resolution and compact size, but analog circuits occupy a relatively large ratio and consume more power
Solution Approach 1:
The patent applies dynamics by making the supply voltage of load transistors variable rather than fixed. The control circuit dynamically adjusts the supply voltage based on the dynamic range of pixel signals, allowing the system to adapt power consumption to actual operating conditions. This resolves the contradiction by enabling low power consumption during low-light conditions while maintaining sufficient performance when needed.
Solution Approach 2:
The patent changes the parameter of supply voltage for load transistors from a constant value to a variable value that depends on the dynamic range of pixel signals. By controlling the supply voltage according to light reception conditions and signal characteristics, the system optimizes the balance between power consumption and circuit performance, allowing pixel miniaturization without proportionally increasing analog circuit power usage.
2Use of energy by stationary object
If PWM system is used to reduce power consumption, then power usage decreases, but signal interference occurs due to photodiodes connected via switch elements
Solution Approach 1:
The patent introduces an intermediary approach by using load transistors with controlled supply voltages as mediators between the photodiodes and the reading circuit. Instead of directly connecting photodiodes via switch elements that cause interference, the load transistors with dynamically controlled supply voltages serve as intermediate components that isolate and condition the signals, reducing interference while maintaining power savings.
Solution Approach 2:
The patent changes the operating parameters of the reading circuit by dynamically adjusting the supply voltage of load transistors based on the dynamic range of pixel signals. This parameter change allows the system to operate in a low-power mode during normal conditions while maintaining signal integrity, avoiding the need for aggressive PWM switching that causes interference.
3Device complexity
If amplifier is removed to reduce complexity, then device configuration simplifies, but operating speed becomes slow
Solution Approach 1:
The patent applies self-service by making the load transistors provide both the loading function and the amplification function through their dynamically controlled supply voltages. The load transistors themselves perform the amplification task without requiring separate dedicated amplifiers, as their supply voltage can be adjusted to provide the necessary gain. This maintains simplicity while preserving operating speed.
Solution Approach 2:
The patent makes the load transistors multi-functional by having them serve both as load elements and as amplification components. By controlling the supply voltage of load transistors based on signal characteristics, a single component performs multiple functions that would traditionally require separate circuits, simplifying the overall device configuration while maintaining performance.
4Device complexity
If fixed supply voltage is used for load transistors, then circuit configuration is simple, but power consumption cannot be optimized
Solution Approach 1:
The patent implements feedback by having the control circuit continuously monitor the dynamic range of pixel signals and adjust the supply voltage of load transistors accordingly. This feedback mechanism allows the system to optimize power consumption in real-time based on actual operating conditions, resolving the contradiction between simple configuration and optimized power usage.
Solution Approach 2:
The patent transforms the static supply voltage into a dynamic parameter that changes with operating conditions. The control circuit adjusts the supply voltage of load transistors based on the dynamic range of pixel signals, enabling the system to adapt power consumption to actual needs while maintaining relatively simple circuit configuration through integrated control.
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 approach enables low power consumption in a simpler configuration by dynamically adjusting the supply voltage or current, reducing power usage while maintaining effective signal processing and linearity.
Implementation Method 1
When light is incident to a photodiode in a predetermined period after a potential VPD of the photodiode is reset to a predetermined potential VRST, the potential VPD of the photodiode is reduced by an amount corresponding to the amount of the incident light.
Data Source
AI summary
The present technique relates to a solid-state image pickup device capable of realizing low power consumption in a simpler configuration, a control method therefor, and an electronic apparatus. The solid-state image pickup device includes a pixel array section that has a plurality of pixels arranged two-dimensionally in a matrix shape, load transistors each of which configures a source follower circuit with an amplification transistor of each pixel of the pixel array section, and a control circuit that, in accordance with the amount of light received by one or more of the pixels, controls a supply voltage of each of the load transistors or controls a current flowing through each of the load transistors. The present technique can be applied to a solid-state image pickup device, for example.