Patent ID: 7598679

Claim:
An apparatus, comprising: an integrated circuit configured to provide power to at least one light source, the integrated circuit further configured to receive a vertical synchronization signal, the integrated circuit comprising: synchronization detection circuitry configured to determine whether the frequency of said vertical synchronization signal complies with at least one of a Phase Alternating Line (PAL) or National Television System Committee (NTSC) vertical synchronization signal, said synchronization detection circuitry comprising: a current source and a capacitor configured to generate an internal reference signal, a switch configured to discharge said capacitor based on said vertical synchronization signal, and a comparator configured to compare said internal reference signal with a DC reference signal and generate a first signal if said internal reference signal is less than said DC reference signal and a second signal if the internal reference signal is greater than said DC reference signal; wherein said first signal is generated if said vertical synchronization signal changes state before said internal reference signal reaches said DC reference signal, and said second signal is generated if said vertical synchronization signal changes state after said internal reference signal reaches said DC reference signal, flip-flop circuitry configured to receive said first and second signals and generate first and second output signals, respectively; wherein said first output signal is indicative that said vertical synchronization signal is an NTSC vertical synchronization signal and said second output signal is indicative that said vertical synchronization signal is said PAL vertical synchronization signal; and pulse width modulation (PWM) circuitry configured to generate a PWM signal to adjust power to said light source, said PWM signal having a frequency that is based on the detected frequency of said vertical synchronization signal.