Blend Dimming Circuit for LED Brightness Control
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Solution Overview
Problem
Conventional dimming methods for LED lighting face challenges in controlling brightness effectively, particularly with rapid increases in input current during PWM dimming, leading to flickering and inefficiencies in current regulation.
Innovation Solution
A blend dimming approach that combines PWM and analog dimming techniques, where a conduction angle is detected to generate control signals, enabling the PWM dimming circuit to regulate brightness when the angle is above a threshold, and using both PWM and analog dimming when the angle is below the threshold, optimizing the dimming curve to reduce rapid current increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PWM dimming mode is used to regulate LED brightness, then brightness control precision is improved, but input current increases rapidly causing flickering and instability
Solution Approach 1:
The patent dynamically switches between PWM dimming mode and analog dimming mode based on the conduction angle detected from the phase-missing DC voltage signal. When the conduction angle is greater than a threshold, PWM dimming is used for precise brightness control. When the conduction angle is less than the threshold, analog dimming is used to prevent rapid current increases and flickering. This dynamic adaptation resolves the contradiction between brightness control precision and input current stability.
Solution Approach 2:
The patent changes the dimming control parameter based on the conduction angle condition. By detecting the conduction angle of the phase-missing DC voltage signal and comparing it with a threshold, the system switches between different dimming methods (PWM or analog). This parameter change strategy allows the system to optimize both brightness control precision and input current stability under different operating conditions.
2Reliability
If analog dimming is used to reduce rapid current increase, then input current stability is improved, but brightness control precision deteriorates
Solution Approach 1:
The system dynamically selects the appropriate dimming method based on real-time detection of the conduction angle. When the conduction angle indicates stable operating conditions (greater than threshold), PWM dimming provides precise brightness control. When the conduction angle indicates potential instability (less than threshold), analog dimming is activated to prevent current spikes and flickering. This dynamic selection resolves the contradiction by choosing the optimal method for each operating state.
Solution Approach 2:
The patent uses feedback from the conduction angle detection to determine which dimming method to employ. The phase-missing DC voltage signal provides feedback about the operating state, and this feedback information is used to switch between PWM and analog dimming modes. This feedback mechanism ensures that the system maintains both brightness control precision and input current stability by adapting to real-time conditions.
3Ease of operation
If PWM dimming circuit is enabled to control power stage, then brightness regulation capability is improved, but device complexity increases due to additional control signals
Solution Approach 1:
The patent merges PWM dimming control and analog dimming control into a unified blend dimming circuit. The conduction angle detector, analog dimming circuit, and PWM dimming circuit work together as an integrated system. The analog dimming circuit generates a control signal that is combined with the PWM dimming signal, allowing both control methods to operate simultaneously or alternately without requiring separate independent systems. This merging reduces overall device complexity while maintaining enhanced brightness regulation capability.
Solution Approach 2:
The blend dimming circuit is designed to perform multiple functions through a single integrated structure. The same circuit can implement both PWM dimming and analog dimming modes, as well as automatically switch between them based on conduction angle detection. This multi-functionality eliminates the need for separate dimming circuits for each mode, thereby reducing device complexity while providing comprehensive brightness regulation capability.
Data Source
AI summary
The present disclosure relates to blend dimming circuits and methods for driving light loads. In one embodiment, a method can include: converting an external sinusoidal AC power supply to a phase-missing DC voltage signal; detecting a conduction angle of the phase-missing DC voltage signal to generate a first control signal representing the conduction angle; generating an analog dimming signal based on the first control signal; generating, by a PWM dimming circuit, a PWM dimming signal based on the analog dimming signal and a light load feedback signal; regulating light load brightness by PWM dimming when the conduction angle is greater than a threshold angle; regulating the light load brightness by PWM and analog dimming when the conduction angle is less than the threshold angle; and enabling a power stage circuit when the first control signal is active to regulate the brightness of the light load.