LED Drive Circuit with Dynamic Load Impedance for Ballast Compatibility
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Solution Overview
Problem
LED tubes face compatibility issues with electronic ballasts, particularly constant-power and magnetic ring self-excited ballasts, leading to over-power usage, which can cause damage or premature decay due to the higher power output from these ballasts compared to the LED tubes.
Innovation Solution
An LED drive circuit with a load impedance increasing circuit and feedback control circuit, utilizing a switching element like a FET or relay, and a current detection unit, which adjusts the load impedance based on the operating current of the LED to match the ballast's output power, thereby reducing the output power and preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the LED tube is connected to a constant-power electronic ballast or magnetic ring self-excited electronic ballast, then the ballast maintains the output power corresponding to the fluorescent lamp, but the power output is much larger than the power of the LED tube, causing over-power usage, overheating, or premature decay
Solution Approach 1:
The patent applies the dynamics principle by making the load impedance adjustable rather than fixed. The load impedance adjusting circuit dynamically changes the impedance value based on the detected operating current, allowing the system to adapt to different ballast types and prevent over-power usage while maintaining compatibility with constant-power electronic ballasts and magnetic ring self-excited ballasts.
Solution Approach 2:
The patent implements feedback control through a feedback control circuit that detects the operating current of the LED and uses this information to adjust the load impedance via the load impedance adjusting circuit. This closed-loop feedback mechanism ensures the LED operates within safe current limits while maintaining compatibility with high-power ballasts.
2Reliability
If the LED tube is designed with built-in protection to prevent over-power damage, then the LED tube can be protected from damage, but the LED tube becomes incompatible with constant-power electronic ballasts, affecting product sales
Solution Approach 1:
The patent introduces a load impedance adjusting circuit as an intermediary component between the LED and the ballast. This intermediary actively adjusts the load impedance to match the ballast's output characteristics, eliminating the need for passive protection circuits that would block compatibility. The intermediary enables both protection and compatibility simultaneously.
Solution Approach 2:
The patent changes the electrical parameter (load impedance) dynamically based on the ballast type and operating conditions. By adjusting the impedance parameter rather than using fixed protection thresholds, the system maintains compatibility with different ballast types while still protecting the LED from over-power conditions.
3Device complexity
If a conventional LED drive circuit is used with electronic ballasts, then the circuit structure is simple, but the load impedance does not match the ballast's high power output, causing over-power usage and potential damage
Solution Approach 1:
The load impedance adjusting circuit serves multiple functions: it matches the load impedance to the ballast's high power output, limits the operating current to protect the LED, and maintains compatibility with different ballast types. This multi-functional component adds moderate complexity while solving multiple problems simultaneously.
Data Source
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AI summary
The present invention provides a light-emitting diode (LED) drive circuit and an LED lamp. The LED drive circuit includes: a feedback control circuit and a load impedance increasing circuit, wherein the feedback control circuit acquires the operating current of an LED, compares the operating current with a default threshold, drives the load impedance increasing circuit to operate when the operating current of the LED is greater than or equal to the threshold, and allows the load impedance increasing circuit not to operate when the operating current of the LED is less than the threshold; and the load equivalent impedance of the LED drive circuit is increased when the load impedance increasing circuit operates. The technical proposals of the present invention can reduce the output power of an electronic ballast, allow the LED lamp to work within the design power, and ensure the normal use of the LED lamp and the product life.