Patent ID: 7558081
Filing Date: 2009-07-07
Classification: H05B

Abstract:
1. A control circuit implemented in an integrated circuit for providing a drive signal to a power semiconductor device for providing an output power signal to a filament lamp, said control circuit comprising: an oscillator for generating an oscillating control signal; and a driver receiving said oscillating control signal and producing said drive signal; a dimming control circuit which controls said oscillator for dimming said lamp; wherein said dimming circuit comprises a first circuit having a dimming signal as an input, said dimming signal comprising a variable voltage level setting a dimming level, and further having a synchronizing signal as an input derived from a full wave rectified AC line signal waveform; the first circuit producing a pulsed synchronizing signal for synchronizing a ramp signal developed across a capacitor to said full wave rectified AC line signal waveform; further comprising a second circuit receiving said dimming signal and said ramp signal and producing a rectangular waveform synchronized to said full wave rectified AC line signal waveform, said rectangular waveform having a duty cycle related to the voltage level of said dimming signal and being provided as an input to said oscillator to generate said oscillating control signal, whereby said oscillating control signal drives the driver to produce the drive signal for the power semiconductor device to produce the output power signal comprising a phase cut oscillating signal synchronized to said full wave rectified AC line signal waveform and having a phase cut component determined by the voltage level of said dimming signal.