Time-of-Flight Sensor Charge Compensation Circuit
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Solution Overview
Problem
Time-of-flight sensors face limitations in dynamic range due to saturation issues at integration nodes, leading to decreased accuracy in distance measurement, especially under varying light conditions.
Innovation Solution
A time-of-flight sensor with at least one pixel featuring two integration nodes connected to a charge compensation device using SBI input transistors, where the SBI current transistors operate independently from the supply voltage, utilizing a reset voltage to extend the margin for setting the SBI threshold, allowing for compensation currents to be provided when integration nodes reach a saturation potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the integration nodes are supplied with supply voltage for charge compensation, then the charge compensation function can be implemented, but the margin for setting the SBI threshold is limited
Solution Approach 1:
The patent changes the voltage parameter from supply voltage to reset voltage for the SBI current transistors. This parameter change allows the SBI threshold to be set with a larger margin because the reset voltage can be adjusted independently from the supply voltage, providing greater flexibility in threshold setting while maintaining the charge compensation function.
2Adaptability or versatility
If the SBI threshold is set closer to the saturation potential to increase dynamic range, then the dynamic range is improved, but the integration nodes may saturate more easily
Solution Approach 1:
The patent implements a feedback mechanism where the actual voltage at the integration node is continuously monitored. When the voltage approaches the saturation potential, the system automatically activates charge compensation to prevent saturation. This feedback loop allows the SBI threshold to be set closer to the saturation potential (increasing dynamic range) while maintaining reliability through automatic saturation prevention.
3Adaptability or versatility
If the supply voltage is increased to provide more headroom for SBI threshold setting, then the margin for SBI threshold is improved, but the power consumption increases
Solution Approach 1:
The patent changes the voltage reference from supply voltage to reset voltage, allowing the SBI threshold to be set with adequate margin without increasing the supply voltage. The reset voltage can be adjusted independently to provide the necessary headroom for threshold setting, thereby avoiding the increased power consumption that would result from raising the supply voltage.
Data Source
AI summary
The present invention provides a time-of-flight sensor (22) including at least one time-of-flight pixel (23) for demodulating a received modulated light beam (Sp2), wherein the time-of-flight pixel (23) comprises at least two integrating nodes (Ga, Gb) and the integration nodes (Ga, Gb) are connected to a device (500) for charge compensation, wherein the charge compensation device (500) comprises at least two SBI input transistors (M1, M2) which at a potential (Ua, Ub) of the integration nodes (Ga, Gb) which according to the amount exceeds an SBI threshold value (USBI) drive SBI current transistors (M3, M4) such that at both integration nodes (Ga, Gb) a compensating current (ik) of the same level flows, wherein the source terminals of the SBI-current transistors (M3, M4) are not connected to a supply voltage (UDD) but are connected to a working voltage (URES, Uarb) (FIG. 7).