Endoscope LED Current Control for High-Speed PWM Imaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
LEDs in electronic endoscope systems are prone to destruction due to high-frequency PWM signals, which exceed the rated current limits due to response delays in the feedback system, especially when high shutter speeds are required for clear imaging.
Innovation Solution
A processor for electronic endoscope systems that includes a light source unit synthesizing light beams and a current control unit with a current generation unit and feedback circuit to stabilize output current, using a low-pass filter to adjust PWM signals and perform both analog and PWM dimming, protecting the LEDs from overcurrent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-frequency PWM signal is used for high shutter speed imaging, then image quality is improved, but LED reliability deteriorates due to overcurrent
Solution Approach 1:
The patent introduces a current control unit as an intermediary between the PWM signal source and the LED. This unit includes a current generation unit that converts the PWM signal into a controlled current signal, and a feedback circuit unit that monitors and regulates the current. The intermediary actively manages the current waveform to prevent overcurrent conditions while maintaining the high-frequency PWM operation needed for high shutter speed imaging.
Solution Approach 2:
The patent implements a feedback control system where the feedback circuit unit continuously monitors the current flowing through the LED and adjusts the output of the current generation unit accordingly. This feedback mechanism detects current deviations and corrects them in real-time, preventing overcurrent conditions that would damage the LED while allowing high-frequency PWM signals to be used for high-quality imaging.
2Illumination intensity
If PWM dimming control is applied to LED, then light intensity control is improved, but current stability deteriorates due to feedback response delay
Solution Approach 1:
The patent employs a feedback circuit unit that continuously monitors the actual current flowing through the LED and compares it with the target current waveform. When deviations are detected, the feedback mechanism adjusts the current generation unit's output in real-time, correcting instability caused by response delays. This closed-loop control maintains current stability even during PWM dimming operations.
Solution Approach 2:
The patent uses a dynamic current control approach where the current generation unit actively adjusts the current waveform in response to changing PWM signals and feedback conditions. Rather than using a fixed current source, the system dynamically adapts the current parameters to match the desired light intensity while maintaining stability, allowing flexible dimming control without sacrificing current consistency.
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 processor effectively stabilizes the output current to prevent LEDs from being destroyed by high-frequency PWM signals, ensuring reliable imaging without LED damage.
Implementation Method 1
a feedback circuit unit that feeds back a current flowing through each of the light-emitting elements to stabilize the output current generated by the current generation unit
Implementation Method 2
a current generation unit that generates, as a current to be applied to each of the light emitting elements, an output current which has a duty ratio corresponding to a pulse width modulation control signal (PWM control signal) and has an amplitude corresponding to a lower-voltage control signal selected from a first control signal and a second control signal obtained by subjecting the PWM control signal to filter processing
Implementation Method 3
a second control signal obtained by subjecting the PWM control signal to filter processing
Data Source
AI summary
A processor for electronic endoscope, the processor being used in an electronic endoscope including an image sensor, a light source unit that synthesizes light beams to be emitted from a plurality of light emitting elements to generate illumination; and a current control unit that controls a current to be applied to each of the light emitting elements in the light source unit. The current control unit includes a current generation unit that generates, an output current which has a duty ratio corresponding to a pulse width modulation (PWM) control signal and has an amplitude corresponding to a lower-voltage control signal selected from a first control signal and a second control signal obtained by subjecting the PWM control signal to filter processing, and a feedback circuit unit that feeds back a current flowing through each of the light-emitting elements to stabilize the output current generated by the current generation unit.