US 10,512,130 B1
Multi-string LED drivers and current switching techniques
Erhan Ozalevli, Santa Clara, CA (US); and Behzad Mohtashemi, Campbell, CA (US)
Assigned to Apple Inc., Cupertino, CA (US)
Filed by Apple Inc., Cupertino, CA (US)
Filed on Feb. 1, 2019, as Appl. No. 16/265,401.
Int. Cl. H05B 33/08 (2006.01); G09G 3/34 (2006.01)
CPC H05B 33/0827 (2013.01) [G09G 3/3406 (2013.01); H05B 33/0812 (2013.01)] 19 Claims
OG exemplary drawing
 
1. A circuit comprising:
a first source;
a second source;
a set of drivers, each of the set of drivers comprising:
a set of first transistors, each first transistor coupled to a pulse-width modulation (PWM) signal;
a first resistor;
a second transistor, the second transistor coupled to the set of first transistors and the first resistor;
a third transistor, the third transistor coupled to the second transistor and the second source; and
an operational amplifier coupled to the second transistor; and
a set of strings of series-connected light emitting diodes (LEDs), wherein the set of strings of series-connected LEDs is coupled to the set of drivers and the first source, such that a respective one of the set of drivers is configured to connect to any one of the set of strings of series-connected LEDs.