Switched-Capacitance Charge Pump for High-Frequency Laser Diode Control
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Solution Overview
Problem
Existing laser diode control circuits are limited in their ability to efficiently generate current pulses at high frequencies and may not fully discharge the laser diode, leading to suboptimal performance and potential spurious oscillations.
Innovation Solution
A switched-capacitance charge pump circuit with a switching circuit and additional charge balancing switch, capable of emitting current pulses in the range of 10 to 800 MHz and ensuring full discharge of the laser diode, using capacitors with capacitance between 10 to 500 pF and MOS transistors for control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional control circuits are used to generate current pulses for laser diode, then the circuit structure is simple, but the pulse generation frequency is limited and the laser diode cannot be fully discharged
Solution Approach 1:
The patent replaces conventional current source-based control circuits with a switched-capacitance charge pump circuit. This substitution enables high-frequency current pulse generation (10-800 MHz) by utilizing capacitor charging and discharging cycles controlled by switching elements, overcoming the frequency limitations of traditional circuits while maintaining manageable complexity through standardized capacitor and switch components
Solution Approach 2:
The patent implements periodic charging and discharging of capacitors through controlled switching actions. The switching circuit periodically connects capacitors to charge them and then disconnects to allow discharge through the laser diode, creating regular current pulses at frequencies between 10-800 MHz. This periodic action ensures complete discharge of the laser diode between pulses, improving performance while enabling high-frequency operation
2Reliability
If conventional control circuits are used, then the circuit resistivity is low, but spurious oscillations occur and laser diode performance is suboptimal
Solution Approach 1:
The patent replaces conventional low-resistivity current sources with a switched-capacitance charge pump that inherently provides higher output resistivity during discharge phases. This substitution suppresses spurious oscillations by preventing unwanted feedback loops and ensures complete discharge of the laser diode, thereby improving reliability and eliminating performance-degrading oscillations
Solution Approach 2:
The patent introduces capacitors as intermediary energy storage elements between the power supply and the laser diode. These capacitors act as buffers that smooth current delivery, prevent direct coupling between stages that could cause oscillations, and ensure controlled discharge through the laser diode. The intermediary capacitors isolate potential oscillation paths while maintaining reliable pulse generation
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
Enables regular current pulse generation at high frequencies, ensures full discharge of the laser diode, and reduces spurious oscillations by increasing the circuit's resistivity.
Implementation Method 1
the charge pump comprises at least one capacitor... the at least one capacitor has a capacitance in the range from 10 to 500 pF
Implementation Method 2
the second switch is an N-channel MOS transistor... the second switch is a P channel MOS transistor
Data Source
AI summary
A circuit includes a laser diode and a switched-capacitance charge pump coupled to control the laser diode. The charge pump can include a capacitor and a switching circuit that is capable of triggering a charge and discharge of the capacitor. The switching circuit can include a switch and an inverting circuit.