Light Source Dimming Control Circuit EMI Reduction
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Solution Overview
Problem
Existing light source dimming technologies face challenges in balancing the accuracy of pulse width modulation dimming mode with increased EMI and the inaccuracy of analog dimming mode, particularly as current levels change.
Innovation Solution
A light source dimming control circuit that incorporates a voltage signal generator, reference voltage signal generator, switch, resistor, switch controller, and current controller, allowing for seamless transition between analog and pulse width modulation dimming modes by using a sawtooth signal and diodes to control the switch and current flow, thereby optimizing current levels for reduced EMI and improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse width modulation dimming mode is used to improve brightness control accuracy, then the electro-magnetic interference (EMI) increases
Solution Approach 1:
The patent changes the operating parameters by switching between two dimming modes (PWM and analog) based on the current level. At high current levels, PWM mode is used for high precision control, while at low current levels, analog mode is used to reduce EMI. This parameter-based mode switching resolves the contradiction by adapting the control method to the operating conditions.
Solution Approach 2:
The patent implements a dynamic control system that automatically transitions between PWM dimming mode and analog dimming mode based on the detected current level. This dynamic adaptation allows the system to optimize between precision and EMI reduction in real-time, resolving the technical contradiction through flexible operational states.
2Object-generated harmful factors
If analog dimming mode is used to reduce EMI interference, then the inaccuracy of the driving current is enlarged by tolerances of the analog components
Solution Approach 1:
The patent changes the control method based on current level parameters. At high current levels where analog component tolerances have less relative impact, analog dimming is used to minimize EMI. At low current levels where precision is more critical, PWM dimming is employed. This parameter-based approach resolves the contradiction between EMI reduction and accuracy.
Solution Approach 2:
The system dynamically switches between analog and PWM dimming modes based on the operating current level. This dynamic adaptation ensures that when precision is more critical (low current), PWM mode is active, while when EMI reduction is prioritized (high current), analog mode is active, resolving the technical contradiction.
3Measurement precision
If PWM dimming mode is used at high current levels, then brightness control precision is improved, but EMI increases
Solution Approach 1:
The patent implements parameter-based mode selection where the dimming method changes based on current level. The system transitions from PWM mode at high currents (where precision is needed and EMI is less problematic) to analog mode at low currents (where EMI reduction is prioritized). This resolves the contradiction by adapting to operating conditions.
Solution Approach 2:
The control system dynamically adapts its operating mode based on real-time current level detection. This dynamic behavior allows the system to optimize performance by using PWM when precision is critical and analog when EMI reduction is more important, resolving the technical contradiction through flexible operation.
4Object-generated harmful factors
If analog dimming mode is used at low current levels, then EMI is reduced, but component tolerances cause inaccuracy
Solution Approach 1:
The patent uses parameter-based mode switching where the dimming method is selected based on current level. At low current levels where precision is more sensitive to component tolerances, the system switches to PWM mode to maintain accuracy. At high current levels where EMI is more problematic, analog mode is used. This resolves the contradiction by adapting to the specific operating conditions.
Solution Approach 2:
The system implements dynamic mode switching that responds to current level changes. This dynamic adaptation ensures optimal performance by selecting the appropriate dimming mode (PWM or analog) based on the operating point, resolving the technical contradiction between EMI reduction and precision requirements.
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 circuit effectively dims the light source in analog mode for high current levels to minimize EMI and in pulse width modulation mode for low current levels to enhance brightness control accuracy, thereby combining the advantages of both methods while avoiding their disadvantages.
Implementation Method 1
The reference voltage signal generator comprises a first diode with an anode end coupled to the voltage signal generator, and a cathode end coupled to the output end; and a second diode with an anode end receiving the second voltage signal, and a cathode end coupled to the output end
Data Source
AI summary
The present invention provides a light source dimming control circuit, which includes a voltage signal generator for generating a first voltage signal between a predetermined voltage level and a ground level; a reference voltage signal generator for generating a reference voltage signal at an output end according to the first voltage signal and a second voltage signal; a first switch with a first end coupled to an output end of alight source; a first resistor with a first end coupled to a second end of the first switch, and a second end coupled to a ground end; a switch controller coupled to the first switch and the voltage signal generator for controlling on/off states of the first switch according to a sawtooth signal and the first voltage signal; and a current controller for controlling current flowing through the first resistor according to the reference voltage signal.