US 12,218,481 B2
Laser safety circuit providing frequency-based average current monitoring
Stephen N. Sweet, San Jose, CA (US); and Dong Zheng, Los Altos, CA (US)
Assigned to APPLE INC., Cupertino, CA (US)
Filed by Apple Inc., Cupertino, CA (US)
Filed on Mar. 24, 2021, as Appl. No. 17/211,761.
Prior Publication US 2022/0311211 A1, Sep. 29, 2022
Int. Cl. H01S 5/068 (2006.01); H01S 3/13 (2006.01)
CPC H01S 5/06808 (2013.01) [H01S 3/13 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A laser safety circuit, comprising:
a current-to-frequency converter configured to generate a first signal modulated at a first frequency, the first frequency varying in accord with an amplitude of a drive current provided to a laser;
an oscillator configured to generate a second signal having a second frequency;
an up/down counter configured to periodically increment or decrement a count responsive to a relationship between the first frequency and the second frequency, and assert an average current trip signal when the count satisfies a threshold count; and
a control circuit configured to modify operation of the laser responsive to the assertion of the average current trip signal.