Light Source Driver Circuit With Bypass Path for Fast Pulse Switching
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Solution Overview
Problem
Conventional driver circuits for light sources in ToF systems are limited by parasitic inductances that affect the rise and fall times of excitation current pulses, impacting measurement accuracy and power consumption, particularly in portable applications.
Innovation Solution
A driver circuit design incorporating a current control unit with a drive path and a bypass path, along with a common current source, minimizes the effect of parasitic inductances by ensuring a constant current flow through these inductances, allowing for faster rise and fall times and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional driver circuit design is used, then the circuit can operate with standard components, but parasitic inductances increase the rise time and fall time of excitation current pulses
Solution Approach 1:
The driver circuit is segmented into multiple parallel current paths (first current path and second current path) instead of a single path. This segmentation allows the circuit to manage current flow more effectively, reducing the impact of parasitic inductances on rise and fall times by providing alternative current routes.
Solution Approach 2:
The driver circuit dynamically switches between different current paths using controllable switches. During turn-on, the first current path is activated; during turn-off, the second current path is activated. This dynamic switching optimizes performance by selecting the appropriate path based on the operational state, thereby minimizing parasitic inductance effects.
2Use of energy by moving object
If high peak power current pulses are generated to achieve large depth sensing range, then the depth sensing range increases, but power consumption increases
Solution Approach 1:
The circuit dynamically manages power delivery by using different current paths for turn-on and turn-off operations. This dynamic approach allows the circuit to achieve high peak power when needed for depth sensing while minimizing power consumption during switching transitions, thus balancing power efficiency with sensing range.
Solution Approach 2:
The circuit converts the potentially harmful effect of parasitic inductances into a beneficial feature by using them in conjunction with the bypass path during turn-off. The parasitic inductances that normally slow down switching are utilized to maintain current flow through the bypass path, enabling faster turn-off and reduced power consumption.
3Measurement precision
If the rise time and fall time are reduced for high measurement accuracy, then measurement accuracy improves, but the circuit complexity increases
Solution Approach 1:
The driver circuit is divided into functional segments (first current path with first switch, second current path with second switch, and current source) that can be independently controlled. This segmentation allows each segment to be optimized for specific functions, achieving fast rise and fall times without requiring complete redesign of the entire circuit.
Solution Approach 2:
The current source serves multiple functions: it provides current through the first path during turn-on and through the second path during turn-off. This multi-functionality reduces the need for separate current sources for each path, thereby reducing overall circuit complexity while maintaining high measurement accuracy.
Data Source
AI summary
The present disclosure relates to a driver circuit for a light source and related methods of operating the driver circuit. In particular, it relates to a driver circuit designed to reduce the effect of parasitic inductances on the rise time/fall time of excitation current pulses applied to the light source using the driver circuit.