| 摘要 |
A circuit which detects an end-of-lamp life or false lamp condition in a fluorescent lamp being driven by an electronic ballast by indirectly sensing total load power through an analog signal indicative of the operating frequency while controlling lamp power using phase control, and which deactivates the half-bridge driver circuit if the operating frequency exceeds a predetermined maximum frequency. Controlling the lamp power via phase control enables the simple detection of excessive lamp power due to either a symmetrical or an asymmetrical increase in lamp running voltage over the course of the life of the lamp. A simple resistor user-programmable interface which allows flexibility for setting different threshold levels for different ballast/lamp combinations. The circuit is easily implemented in an electronic ballast driver IC (e.g., the IR2158/2159), resulting in the elimination of existing high-voltage-sensing-component methods, reduction of PCB interconnects, and an increase in manufacturability.
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