Reference frequency from ambient light signal

摘要

A system includes an oscillator referenced to a frequency extracted from periodic intensity modulations of incident light. The incident light can be intensity modulated based on the frequency of the AC voltage that powers artificial lighting. The system includes a light-sensitive element configured to generate an output signal indicative of an intensity of incident light and a controller. The controller can receive a first input signal based on the output signal from the light-sensitive element. In the presence of artificial lighting, the first input signal has a frequency based on a reference frequency at which an intensity of light incident on the light-sensitive element periodically varies. The controller can generate a control signal based in part on the reference frequency. The controller can provide the generated control signal to the adjustable oscillator to thereby adjust the oscillator frequency.

主权项

1. A system comprising:
an adjustable oscillator configured to generate a periodically varying output signal at an oscillator frequency, wherein the oscillator frequency is at least partially based on an input control signal; a light-sensitive element configured to generate an output signal indicative of an intensity of light incident on the light-sensitive element; a controller configured to: (i) receive a first input signal based on the output signal from the light-sensitive element, wherein the first input signal has a frequency based on a reference frequency at which an intensity of light incident on the light-sensitive element periodically varies; (ii) generate a control signal based in part on the reference frequency; and (iii) provide the generated control signal to the adjustable oscillator to thereby adjust the oscillator frequency; and a pulse generation circuit configured to generate the first input signal received by the controller, wherein the pulse generation circuit comprises a comparator configured to: (i) receive a voltage signal based on the output signal from the light-sensitive element; and (ii) output a series of voltage pulses, wherein each voltage pulse corresponds to the received voltage signal exceeding a threshold voltage.