LED Driver Circuit Analog Current Control for Surgical Lighting
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Solution Overview
Problem
Current LED driver circuits using pulse width modulation (PWM) cause LEDs to flash rapidly, leading to eye fatigue in prolonged exposure situations, particularly in surgical lighting systems where this can be detrimental to both surgeons and patients.
Innovation Solution
An LED driver circuit with a voltage converter providing a fixed voltage to an LED string and a current-based light-adjusting unit controlling the current amplitude in an analog manner based on the duty cycle of a PWM signal, eliminating the need for rapid switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If PWM dimming technique is used to drive LEDs, then power consumption is reduced and lighting control is achieved, but LED flashing occurs causing eye fatigue
Solution Approach 1:
The patent applies periodic pulse width modulation signals to control the LED string, where the duty cycle of the PWM signal determines the lighting intensity. By using periodic action with appropriate frequency, the patent achieves power control while minimizing perceptible flashing effects that cause eye fatigue.
Solution Approach 2:
The patent changes the operating parameters of the LED driver circuit, specifically using a voltage converter to provide stable voltage and adjusting the PWM duty cycle to control current amplitude. This parameter adjustment allows energy savings while reducing the harmful flashing effect by optimizing the switching characteristics.
2Ease of operation
If PWM switching is used for LED control, then lighting intensity adjustment is achieved, but flashing and stripes appear on monitors
Solution Approach 1:
The patent introduces a voltage converter as an intermediary component between the power supply and the LED string. This mediator stabilizes the voltage before it reaches the LEDs, reducing electrical noise and switching transients that cause monitor interference, while still allowing PWM control for lighting adjustment.
Solution Approach 2:
The patent modifies the electrical parameters by using a voltage converter to provide stable voltage and controlling current amplitude through PWM duty cycle adjustment. This changes the operating characteristics to reduce electromagnetic interference that causes flashing and stripes on monitors.
3Productivity
If rapid switching between zero-current and full-current states is used, then PWM dimming is achieved, but eye fatigue occurs during prolonged exposure
Solution Approach 1:
The patent uses periodic PWM signals with optimized frequency and duty cycle to control LED illumination. By adjusting the periodic action parameters, the patent maintains lighting control efficiency while reducing the amplitude and frequency of current transitions that cause eye fatigue during prolonged exposure.
Solution Approach 2:
The patent changes the current waveform parameters by using a voltage converter and controlling current amplitude through PWM duty cycle. This modifies the switching characteristics to reduce the severity of current transitions, thereby maintaining productivity while reducing eye fatigue.
Data Source
AI summary
The present invention provides an LED driver circuit, comprising a voltage converter electrically connected to a power supply and an LED string, wherein the voltage converter provides a fixed voltage to the LED string; and a current-based light-adjusting unit electrically connected to the voltage converter, wherein the current-based light-adjusting unit controls the amplitude of the current flowing through the LED string, in an analog manner and based on a duty cycle of a pulse width modulation signal.