Patent ID: 7999494
Filing Date: 2011-08-16
Classification: H05B

Abstract:
1. An electronic ballast with dimming control from power line sensing for a fluorescent lamp, comprising: a line switching sensing circuit, used to generate a switching sensing signal by performing a voltage comparison operation on a DC voltage, and generate a reset signal by detecting the instance when a filtered DC voltage falls below a reset threshold level, wherein said DC voltage and said filtered DC voltage are derived from a main input voltage rectified from a power line, and said reset threshold level is above a minimum operation voltage of said electronic ballast; a control voltage generator, used to generate a control voltage according to a count of said switching sensing signal, and said control voltage generator is reset by said reset signal when said power line is turned off for a period exceeding a predetermined time; a voltage controlled oscillator, used to generate a oscillating signal according to said control voltage; and a non-overlapping driver, used to generate a high side driving signal and a low side driving signal according to said oscillating signal.