Double-Ended Retrofit LED Pin-Safety Circuit for HF Ballast Compatibility
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Solution Overview
Problem
Retrofit LED lighting devices face challenges in achieving compatibility with electronic ballasts, particularly High Frequency (HF) ballasts, due to the need for precise filament impedance matching and safety concerns during installation, which can lead to overheating issues and safety hazards.
Innovation Solution
A double-ended retrofit LED lighting device with a pin-safety circuit that includes switches connected to both ends, bypassing the filament circuit when the device is turned on, and an impedance matching circuit to improve power transfer and reduce signal reflection, ensuring safe operation and compatibility with HF ballasts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the filament impedance is made low to enable HF ballast operation, then the ballast can start up properly, but the resistors inside the LED device overheat
Solution Approach 1:
The patent applies dynamics by making the filament impedance adjustable rather than fixed. The circuit transitions between different impedance states: during startup it presents low impedance for ballast operation, and during normal operation it presents high impedance to prevent overheating. This dynamic adjustment resolves the contradiction between needing low impedance for startup and high impedance for safe operation.
Solution Approach 2:
The patent changes the impedance parameter over time and operating conditions. By using control circuitry to adjust the filament impedance based on operational state (startup vs. normal operation), the system optimizes performance at different stages. This parameter change allows the same circuit to satisfy conflicting requirements at different times.
2Temperature
If the filament impedance is made high to prevent resistor overheating, then the resistors remain cool, but the HF ballast cannot start up properly
Solution Approach 1:
The patent applies preliminary action by providing a dedicated startup mode where the filament impedance is temporarily set to a low value just long enough to enable the HF ballast to start up. After startup is achieved, the impedance is switched to a high value for normal operation. This preliminary low-impedance action resolves the startup requirement without compromising safety during ongoing operation.
Solution Approach 2:
The dynamic switching between low and high impedance states allows the system to meet the ballast startup requirement transiently while maintaining safe operating temperatures during sustained operation. The temporal separation of these conflicting requirements through dynamic control resolves the contradiction.
3Ease of operation
If the pins are made accessible during installation for ease of connection, then installation is simpler, but hazardous voltage can be induced causing safety hazards
Solution Approach 1:
The patent introduces an intermediary safety circuit between the accessible pins and the high-voltage mains input. This intermediary circuit includes isolation components and control logic that prevent hazardous voltage from reaching the user-accessible pins during installation, while still allowing the device to function normally. The intermediary protects users without compromising installation ease.
Solution Approach 2:
The patent applies preliminary anti-action by implementing safety measures that preemptively prevent hazardous voltage induction before it can affect users during installation. The circuit design includes inherent safety features that block or redirect potentially harmful voltages, ensuring that even if pins are accessible during installation, no hazardous voltage can be induced.
Data Source
AI summary
A double ended retrofit LED lighting device having two connecting terminals (L1, L2) at a first end for connection to a power source and two further connecting terminals (R1, R2) at a second end for further connection to said power source, the LED lighting device comprising: —at least one LED (D1) for emitting light, —an LED driver arranged for receiving an AC current from said power source and for driving said at least one LED based on said received AC current, —a filament circuit (RfilL) connected between said two connecting terminals (L1, L2) for supporting a filament current circulating back to said power source for indicating a presence of said LED lighting device to said power source, and—a pin-safety circuit comprising two pin-safety switches (SwLa, SwLb), wherein each pin-safety switch is connected to a respective separate terminal of said two connecting terminals (L1, L2) and comprises a changeover contact, wherein said changeover contact comprises: —a central node (CC) arranged to be connected to said power source; —a normally-closed node (NC) arranged to be connected to said filament circuit (RfilL); —a normally-open node (NO) arranged to be connected to said LED driver, such that said filament circuit (RfilL) is functionally disconnected, when said AC current flows to, or from, said LED driver.