Analog Pulse Width Limiting for TOF Laser MOSFET Heat Protection
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Solution Overview
Problem
In high frequency, high timing resolution systems like Time of Flight (TOF) determining sub-systems, programmable digital control of power MOSFETs driving high power light emitters can lead to overheating due to unduly large pulse widths or unduly small spacings between pulses, risking damage to components.
Innovation Solution
A pulse duration limiting circuit with an analog integrator and a voltage triggered clamping device is used to integrate programmable digital pulses, switching off high powered components when a threshold voltage is reached, preventing overheating by inhibiting current supply to the power switching device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If programmable digital control is used to define pulse widths, then timing resolution and flexibility are improved, but risk of overheating increases due to unduly large pulse widths or small spacings
Solution Approach 1:
The analog integrator continuously integrates the digitally controlled pulse widths before they reach the power switching device. This preliminary analog processing establishes a physical limit on the maximum pulse duration that can be safely applied, preventing unduly large pulse widths from causing overheating while preserving the benefits of digital programmability for timing resolution
Solution Approach 2:
The patent introduces an analog integrator and voltage-triggered clamping device as intermediary components between the digital control system and the power switching device. This intermediary analog circuitry translates and limits the digitally defined pulse widths, ensuring that the programmable timing resolution is maintained while the physical output is constrained to safe operating parameters
2Area of stationary object
If power switching device is closely packed next to driven load, then space utilization is improved, but heat generation and overheating risk increase
Solution Approach 1:
The analog integrator performs preliminary processing of the control pulses to prevent unduly large pulse widths from reaching the closely packed power switching device and load. This advance limitation reduces the thermal stress on components that are necessarily in close proximity, mitigating overheating risks while maintaining compact layout
Solution Approach 2:
The patent dynamically changes the pulse width parameter through analog integration and clamping, converting potentially harmful long pulses into safe shorter pulses. This parameter transformation allows the system to maintain compact component spacing while automatically adjusting the thermal load to safe levels
3Reliability
If analog integrator with voltage triggered clamping device is used to limit pulse duration, then overheating prevention is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex digital monitoring and control systems with a simpler analog integrator and voltage-triggered clamping device. The analog circuit naturally integrates the pulse signal and automatically clamps it at the predetermined voltage threshold, achieving reliable overheating prevention through inherent analog behavior rather than complex digital logic
Solution Approach 2:
The analog integrator and voltage-triggered clamping device operate autonomously to limit pulse durations. The circuit self-regulates by naturally integrating incoming pulses and automatically clamping the output when the predetermined voltage threshold is reached, providing reliable overheating prevention without requiring external monitoring or control systems
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 effectively prevents overheating of high powered components and nearby components by automatically switching them off or into a lower power mode, ensuring system reliability and longevity.
Implementation Method 1
A pulse duration limiting circuit is provided having an analog integrator configured to integrate over time, the programmably defined digital pulses
Implementation Method 2
The threshold voltage is one at and above which the voltage triggered clamping device switches from a first transconductance mode having relatively low transconductances mode to a second transconductance mode having substantially higher transconductances
Implementation Method 3
when the voltage triggered clamping device is triggered into its second transconductance mode having the substantially higher transconductances, it removes current from the current supplying circuit branch and thereby significantly impedes the ability of the current supplying circuit branch to supply current
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
A power switching device (e.g., MOSFET) drives relatively large surges of pulsed power through a laser emitter of a Time of Flight determining system where both the switching device and laser emitter are closely packed on a printed circuit board having further closely packed and temperature sensitive other components. A pulse duration limiting circuit is provided having an analog integrator configured to integrate over time, the produced and programmably defined pulses. A voltage triggered clamping device couples to an output of the analog integrator. The voltage triggered clamping device has a predetermined threshold voltage at and above which it switches from a relatively low transconductance mode to a substantially higher transconductance mode. The voltage triggered clamping device is coupled to a current supplying circuit branch of the system, the current supplying circuit branch being one that has an ability to supply current for switching on the power switching device.