Semiconductor Light Source Drive Device PWM Current Control
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Solution Overview
Problem
Existing semiconductor light source drive devices face challenges in maintaining high power efficiency and accurate current control during high-speed pulse-width modulation, particularly due to fluctuations in temperature and power supply voltage, as well as manufacturing variations.
Innovation Solution
A semiconductor light source drive device comprising a switching element, current detection element, switching power source, PWM supply circuit, target value setting part, and comparator, which rapidly converges the average current value by comparing detected and target current values to control the power supply, allowing for stable and efficient pulse-width modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional drive circuits are used for high-speed PWM, then switching speed can be achieved, but power efficiency deteriorates and current control accuracy worsens due to temperature and voltage fluctuations
Solution Approach 1:
The patent implements a feedback mechanism where the actual current flowing through the semiconductor light source is detected and compared with the target current value. The comparator generates an error signal that is integrated and used to adjust the PWM duty cycle dynamically, ensuring accurate current control while maintaining high switching speeds and power efficiency.
Solution Approach 2:
The patent replaces conventional voltage-based PWM control with a current-based control system. By directly controlling and feedback the current through the light source rather than relying on voltage switching, the system achieves better power efficiency and current control accuracy without sacrificing PWM switching speed.
2Speed
If conventional drive circuits are used for high-speed PWM, then switching speed can be achieved, but current control accuracy deteriorates due to temperature and power supply voltage fluctuations
Solution Approach 1:
The patent implements a feedback mechanism where the actual current flowing through the semiconductor light source is detected and compared with the target current value. The comparator generates an error signal that is integrated and used to adjust the PWM duty cycle dynamically, ensuring accurate current control while maintaining high switching speeds and power efficiency.
Solution Approach 2:
The patent dynamically adjusts the PWM duty cycle parameter based on real-time current feedback. By changing the duty cycle parameter in response to detected current deviations, the system maintains accurate current control despite temperature and voltage fluctuations, while preserving high-speed PWM capability.
3Device complexity
If simple PWM control is used, then device complexity is reduced, but current convergence speed worsens when on-time ratio changes
Solution Approach 1:
The patent implements a feedback mechanism where the actual current flowing through the semiconductor light source is detected and compared with the target current value. The comparator generates an error signal that is integrated and used to adjust the PWM duty cycle dynamically, ensuring accurate current control while maintaining high switching speeds and power efficiency.
Solution Approach 2:
The patent introduces an integrator circuit as an intermediary between the comparator and the PWM control. This integrator smoothly adjusts the PWM duty cycle based on accumulated error signals, enabling rapid current convergence when on-time ratio changes without requiring overly complex control logic.
4Device complexity
If voltage-based PWM control is used, then device complexity is reduced, but power efficiency and current control accuracy worsen
Solution Approach 1:
The patent replaces conventional voltage-based PWM control with a current-based control system. By directly controlling and feedback the current through the light source rather than relying on voltage switching, the system achieves better power efficiency and current control accuracy without sacrificing PWM switching speed.
Solution Approach 2:
The patent implements a feedback mechanism where the actual current flowing through the semiconductor light source is detected and compared with the target current value. The comparator generates an error signal that is integrated and used to adjust the PWM duty cycle dynamically, ensuring accurate current control while maintaining high switching speeds and power efficiency.
Data Source
AI summary
A semiconductor light source drive device includes a semiconductor light source; a switching element that controls a current flowing through the semiconductor light source by being on/off-controlled by a PWM signal provided to the control end; a current detection element that detects a current flowing through the semiconductor light source; a switching power source that supplies power supply voltage to a series connection of the semiconductor light source, the switching element, and the current detection element; a PWM supply circuit supplies the PWM signal and its on-time ratio information; a target value setting part converts the on-time ratio information to a target average current value and outputs the target average current value; and a comparator compares the target average current value with an average current value detected by the current detection element and outputs comparison output to the switching power source as a signal for control.