Adaptive LED Drive Circuit for Wide Voltage Range
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Solution Overview
Problem
Conventional LED drive circuits fail to simultaneously maintain a constant current state and achieve desired dimming depth across a wide input voltage range, particularly in applications with varying input voltages like 120V and 277V, due to fixed maximum on-time parameters that do not adapt to voltage changes.
Innovation Solution
The method involves setting multiple sets of preset maximum on-time and current limit parameters that are adaptively selected based on the input voltage, allowing the system to adjust these parameters to ensure constant current and optimal dimming performance across a wider voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large maximum on-time parameter is set for 120V input voltage, then the system can achieve constant current state at 120V, but the dimming schedule becomes short and dimming depth is reduced at 277V input voltage
Solution Approach 1:
The patent applies dynamics by making the maximum on-time parameter adjustable rather than fixed. The controller dynamically selects between a first maximum on-time parameter and a second maximum on-time parameter based on the detected input voltage level, allowing the system to adapt its timing characteristics to match different voltage conditions and achieve both constant current and adequate dimming schedule
Solution Approach 2:
The patent implements parameter changes by modifying the maximum on-time parameter value based on input voltage conditions. When high input voltage is detected, the controller uses a smaller second maximum on-time parameter; when low input voltage is detected, it uses a larger first maximum on-time parameter. This parameter adaptation resolves the contradiction between maintaining constant current and preserving dimming depth across different voltage levels
2Adaptability or versatility
If a small maximum on-time parameter is set for 277V input voltage, then the system can achieve desired dimming schedule at 277V, but the system cannot achieve constant current state at 120V input voltage
Solution Approach 1:
The system dynamically adjusts the maximum on-time parameter based on real-time voltage detection. The controller switches between two parameter sets depending on whether the input voltage is high (277V) or low (120V), enabling the system to maintain both dimming schedule performance and constant current operation across different voltage conditions
Solution Approach 2:
The patent changes the maximum on-time parameter value according to input voltage levels. For high voltage (277V), a smaller second maximum on-time parameter is used to achieve proper dimming schedule. For low voltage (120V), a larger first maximum on-time parameter is used to maintain constant current state, thus resolving the contradiction through conditional parameter modification
3Device complexity
If fixed maximum on-time parameter is used, then the device complexity is reduced, but the system cannot simultaneously meet constant current and dimming requirements across wide input voltage range
Solution Approach 1:
The patent introduces dynamic parameter selection where the controller automatically chooses between two maximum on-time parameter values based on detected input voltage. This dynamic adaptation enables the system to handle a wide input voltage range (120V and 277V) while maintaining both constant current and dimming performance, overcoming the limitations of fixed parameter designs
Solution Approach 2:
The system modifies the maximum on-time parameter based on input voltage conditions. By detecting the voltage level and selecting appropriate parameter values (first maximum on-time parameter for 120V, second for 277V), the system achieves adaptability across wide voltage ranges without requiring complex user configuration or multiple hardware designs
Data Source
AI summary
A light-emitting diode (LED) drive method, an LED drive circuit, and an LED lighting device are provided. The method includes: setting preset values of a maximum on-time parameter and a current limit parameter, where the preset values are in at least two sets; selecting a set of the preset values of the maximum on-time parameter and the current limit parameter after a value of a voltage signal on a direct current (DC) bus is detected; controlling a drive current flowing through an LED load based on a selected maximum on-time parameter and a selected current limit parameter. The maximum on-time parameter and the current limit parameter of the system can be adaptively adjusted according to an input voltage, so that the system can have a preferred dimming schedule and dimming depth while realizing a constant current in a wider input voltage range.