Optical Pulse Drive Circuit With Cathode Pre-Charge Compensation
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Solution Overview
Problem
Time-of-flight-based measurement systems, such as 3D sensing and LIDAR, face challenges in emitting optical pulses with well-defined rectangular shapes due to parasitic elements in drive circuits, which increase rise and fall times, affecting measurement precision.
Innovation Solution
An electrical drive circuit using cathode pre-charge and cathode-pull compensation techniques, with a single switch and input trigger signal, provides complementary main and compensation currents to form optical pulses with sharp rise and fall times, improving pulse shape and reducing parasitic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional drive circuits are used to drive optical loads, then the circuit design is simple, but the rise and fall times of optical pulses are increased due to parasitic elements, reducing measurement precision
Solution Approach 1:
The drive circuit is segmented into multiple functional blocks: a first circuit block providing main current through a switch and rectifier, and a second circuit block providing compensation current through a capacitor connected in parallel with the rectifier. This segmentation allows independent optimization of each block to compensate for parasitic effects and achieve sharp rise and fall times.
Solution Approach 2:
The compensation current circuit is designed to produce a current that anticipates and counteracts the parasitic effects in the main current circuit. The capacitor is pre-charged to generate a compensation current with opposite polarity to the parasitic current, thereby canceling out the unwanted effects before they degrade the pulse shape.
2Shape
If parasitic elements are present in the drive circuit, then the circuit implementation is easier, but the optical pulse shape deteriorates with increased rise and fall times
Solution Approach 1:
The parasitic elements in the drive circuit are converted from harmful factors into beneficial components. The rectifier's parasitic capacitance and the switch's parasitic inductance are utilized as part of the compensation mechanism. By carefully designing the compensation current circuit, these parasitic elements contribute to shaping the optical pulse rather than degrading it, achieving sharp rise and fall times.
3Device complexity
If a single switch circuit is used, then the device complexity is reduced, but the ability to provide both main and compensation currents independently is limited
Solution Approach 1:
The single switch in the drive circuit is designed to perform multiple functions: it controls both the main current flow through the optical load and the charging/discharging of the compensation capacitor. This multi-functionality allows the circuit to generate both main and compensation currents using a single switching element, maintaining simplicity while achieving independent current control through proper circuit configuration.
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 enables the emission of optical pulses with short rise and fall times, enhancing measurement precision and accuracy in TOF-based systems while simplifying circuit design and increasing power efficiency.
Implementation Method 1
a capacitor connected in parallel with the rectifier
Implementation Method 2
an inductor connected between the second end of the switch and the second source
Implementation Method 3
a rectifier connected between the cathode and a second end of the switch
Data Source
AI summary
In some implementations, an electrical drive circuit may generate a rectangular optical pulse using cathode pre-charge and cathode-pull compensation. The electrical drive circuit may include an anode and a cathode to connect an optical load, a switch, a first source connected between the anode and a ground, a rectifier connected between the cathode and the switch, a capacitor connected in parallel with the rectifier, a second source connected to the ground, and an inductor connected between the switch and the second source. In some implementations, when the switch is closed and the optical load is connected, a first current is provided to the optical load through the first source, the rectifier, and the switch, and a second current is provided to the optical load through the first source, the capacitor, and the switch, where a rise time of the first current complements a fall time of the second current.