LED Drive Circuit Using Coordinated Switching for Stable Dimming
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Solution Overview
Problem
Existing LED light source control technologies face challenges in efficiently regulating current and voltage to achieve precise intensity and color control, particularly in dimming applications, which can lead to erroneous operations and inefficiencies.
Innovation Solution
A controllable impedance circuit coupled with a feedback loop and digital control circuit that adjusts the peak and average load current through pulse-width modulation, using a combination of switching devices and filter circuits to generate drive signals for precise control of LED light sources, allowing for both constant current reduction and pulse-width modulation dimming techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional LED control technologies are used, then the system structure is simple, but precise intensity and color control cannot be achieved leading to erroneous operations
Solution Approach 1:
The patent implements feedback circuits that continuously monitor the LED light source parameters and adjust the drive signals accordingly. The control circuit receives feedback about the actual intensity and color output and modifies the PWM duty cycle and current magnitude to maintain precise control, preventing erroneous operations while achieving the desired precision.
Solution Approach 2:
The patent employs dynamic control mechanisms including PWM (pulse-width modulation) and constant current reduction techniques that continuously adapt the drive parameters. The control circuit dynamically adjusts the duty cycle and current magnitude based on real-time conditions, enabling precise intensity and color control without requiring an overly complex static circuit design.
2Stability of the object's composition
If current load control technique is used with multiple parallel LED strings, then current balance can be achieved, but additional regulation elements are required increasing device complexity
Solution Approach 1:
The patent designs the control circuit to perform multiple functions simultaneously: it regulates current to each parallel LED string, maintains current balance between strings, and provides dimming control through PWM. By integrating these functions into a single control architecture with shared feedback paths and a unified PWM generator, the patent achieves current balance without adding separate regulation elements for each string.
Solution Approach 2:
The patent combines the current regulation and dimming control functions into a single integrated control circuit. The feedback from parallel LED strings is merged into a common control pathway, and the PWM signal generation is unified, allowing the system to maintain current balance across multiple strings without requiring individual regulation elements for each string.
3Illumination intensity
If PWM dimming technique is used, then light output can be precisely dimmed, but complex switching control is required
Solution Approach 1:
The patent implements PWM dimming by applying periodic switching signals to the LED drive circuit. The control circuit generates regular pulse waves with variable duty cycles, where the pulse frequency remains constant but the on-time proportion changes to achieve precise dimming. This periodic action simplifies the switching control compared to continuous analog adjustment.
Solution Approach 2:
The patent achieves precise dimming control by changing the duty cycle parameter of the PWM signal rather than modifying the pulse frequency or amplitude. The control circuit adjusts the proportion of on-time within each PWM period, providing precise control over the average current to the LED while maintaining a simple switching mechanism with fixed frequency and amplitude characteristics.
Data Source
AI summary
A controllable lighting device may utilize a controllable impedance circuit to conduct a load current through an LED light source. The controllable impedance circuit may be coupled in series with a first switching device, which may be rendered conductive and non-conductive via a pulse-width modulated signal to adjust an average magnitude of the load current. The controllable lighting device may further comprise a control loop circuit that includes a second switching device. The second switching device may be rendered conductive and non-conductive in coordination with the first switching device to control when a feedback signal is provided to the control loop circuit and used to control the LED light source. The control loop circuit may be characterized by a time constant that is significantly greater than an operating period of the load current.