Background Light Suppression Circuit for Time-of-Flight Sensors
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Solution Overview
Problem
Existing circuits for background light suppression in time-of-flight sensors are limited in functionality and space efficiency, particularly in handling varying levels of extraneous light, which can lead to saturation and erroneous distance measurements.
Innovation Solution
A circuit with a differential input stage and switchable current sources for maximum detection and common mode operations, allowing for adaptable compensation currents based on background light conditions, enabling seamless operation across different applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate circuits are provided for maximum detection mode and common mode operation, then the functionality is improved, but the device complexity and space consumption increase
Solution Approach 1:
The patent combines both maximum detection mode and common mode operation into a single unified circuit. The input stage includes bypass and common mode switches that can selectively connect to different operational paths, allowing one circuit to perform multiple functions that would traditionally require separate circuits.
Solution Approach 2:
The operational amplifier and current sources are designed to be multi-functional, serving both maximum detection and common mode operations. The circuit can be switched between different modes using the bypass and common mode switches, making a single circuit universal for multiple applications.
2Adaptability or versatility
If multiple current sources are provided for different operating modes, then the adaptability to different light conditions is improved, but the device complexity increases
Solution Approach 1:
The circuit employs switchable current sources that can dynamically change their operation mode. The bypass and common mode switches allow the current sources to be reconfigured between maximum detection mode and common mode operation, providing dynamic adaptability without requiring completely separate static circuits for each mode.
3Device complexity
If a single circuit is used for both maximum detection and common mode operation, then the device complexity is reduced, but the adaptability to different applications may be compromised
Solution Approach 1:
The unified circuit is segmented into distinct functional paths using bypass and common mode switches. These switches create separate operational paths within the single circuit, allowing independent control of maximum detection and common mode operations while maintaining the benefits of a compact unified design.
Data Source
AI summary
Described is a circuit for background light suppression (SBI, 500) for a light propagation time sensor (22) which operates according to a phase measuring principle and the light propagation time pixels of which have integration nodes or diodes (Ga, Gb, diode_a, diode_b) for the accumulation of charges, having an input stage (50), an operational amplifier (OP) and an SBI current source (SQ), wherein the input phase (50) has bypass and common mode circuits (SBP, SVcm) via which signals of the integration nodes (Ga, Gb, diode_a, diode_b) are guided to the operational amplifier (OP) and via which the operational amplifier (OP) can be switched to a maximum detection or common mode operation, wherein the operational amplifier (OP) is designed such that based on the signals of the integration nodes (Ga, Gb, diode_a, diode_b) switched by the input stage (50) to the operational amplifier (OP), a gate voltage (gate_cs) is generated for the SBI current source (SQ), wherein the SBI current source (SQ) has a first current source (SQ1) for the maximum detection operation and a second and third current source (SQ2a, SQ2b) for the common mode operation wherein the current sources (SQ1, SQ2a, SQ2b) can be connected via switches (S) to integration nodes (Ga, Gb, diode_a, diode_b).