TOF Illumination Driver Circuit With DAC Feedback for Low Phase Noise
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Solution Overview
Problem
Existing illumination drivers for time-of-flight systems fail to meet requirements of high current support, high modulation frequencies, and low phase noise, and are affected by thermal noise, flicker noise, and parasitic capacitance, leading to nonlinearity and inefficiency.
Innovation Solution
A circuit design incorporating an amplifier and digital-to-analog converter (DAC) with current elements and switches, which provides a feedback mechanism to stabilize current flow through a light emitting diode (LED), reducing flicker noise and parasitic capacitance effects while maintaining efficiency and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing illumination driver designs are used, then circuit simplicity is maintained, but the driver fails to meet high current support requirements and exhibits nonlinearity
Solution Approach 1:
The patent implements a feedback mechanism where the DAC output is fed back through a feedback switch to the amplifier input, creating a closed-loop system that stabilizes current delivery to the LED and reduces nonlinearity while maintaining circuit manageability
Solution Approach 2:
The patent uses dynamic switching elements (switches controlled by clock signals) within the DAC structure to achieve high-speed operation and high modulation frequencies, transforming a static circuit into a dynamically controllable system that meets TOF performance requirements
2Measurement precision
If existing illumination drivers operate at high modulation frequencies, then depth accuracy improves, but phase noise increases
Solution Approach 1:
The feedback loop compensates for phase noise by continuously adjusting the DAC output based on the actual current delivered to the LED, maintaining signal integrity even at high modulation frequencies of 50 MHz or more
Solution Approach 2:
The patent changes the operational parameters of the circuit elements, particularly using high-speed switches and optimizing the timing of switch activation with clock signals, to achieve high modulation frequencies while controlling phase noise through precise parameter management
3Reliability
If existing illumination drivers are used, then device simplicity is maintained, but thermal noise and flicker noise affect performance
Solution Approach 1:
The feedback mechanism detects and compensates for noise-induced current variations, reducing the impact of thermal and flicker noise on the LED current and improving overall signal quality for TOF measurements
Solution Approach 2:
The circuit performs preliminary noise filtering and stabilization through the amplifier and feedback loop before the current reaches the LED, preventing noise from affecting the light output and subsequent depth measurements
4Productivity
If existing illumination drivers are used, then power consumption is reduced, but current delivery efficiency decreases
Solution Approach 1:
The patent employs periodic switching of the DAC current elements synchronized with clock signals, delivering current in efficient pulses that match the TOF modulation requirements, improving current delivery efficiency while managing power consumption through duty cycle 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
The solution achieves stable and efficient current delivery to the LED, enhancing depth accuracy and resolution in time-of-flight systems by reducing phase noise and power consumption, and minimizing the impact of parasitic capacitance.
Implementation Method 1
The light source in a typical TOF system is a light emitting diode (LED) or a laser module
Implementation Method 2
The DAC includes one or more current elements. Each current element of the one or more current elements receives a clock. The DAC includes one or more switches corresponding to the one or more current elements
Data Source
AI summary
The disclosure provides a circuit. The circuit includes an amplifier and a digital to analog converter (DAC). The amplifier receives a reference voltage at an input node of the amplifier. The DAC is coupled to the amplifier through a refresh switch. The DAC includes one or more current elements. Each current element of the one or more current elements receives a clock. The DAC includes one or more switches corresponding to the one or more current elements. A feedback switch is coupled between the one or more switches and a feedback node of the amplifier. The DAC provides a feedback voltage at the feedback node of the amplifier.