US 12,144,077 B2
Dimming interface using combination of analog and digital dimming
Giovanni Gritti, Bergamo (IT); and Claudio Adragna, Monza (IT)
Assigned to STMicroelectronics S.r.l., Agrate Brianza (MB) (IT)
Filed by STMicroelectronics S.r.l., Agrate Brianza (IT)
Filed on Sep. 30, 2021, as Appl. No. 17/490,034.
Prior Publication US 2023/0123235 A1, Apr. 20, 2023
Int. Cl. H05B 45/325 (2020.01); H05B 45/10 (2020.01); H05B 45/397 (2020.01)
CPC H05B 45/325 (2020.01) [H05B 45/10 (2020.01); H05B 45/397 (2020.01)] 18 Claims
OG exemplary drawing
 
1. An LED lighting system, comprising:
switching circuitry configured to adjustably drive a string of LEDs, the switching circuitry controlled by a reference current and an enable signal; and
a controller configured to generate the reference current and enable signal based upon a PWM signal such that the switching circuitry, under control of the reference current and the enable signal:
sources a first LED current to the string of LEDs that is proportional to a duty cycle of the PWM signal when the duty cycle is greater than a threshold duty cycle; and
sources a second LED current to the string of LEDs that has a duty cycle proportional to the duty cycle of the PWM signal when the duty cycle of the PWM signal is less than the threshold duty cycle, such that a magnitude of an average LED current delivered to the string of LEDs is proportional to the duty cycle of the PWM signal when the duty cycle of the PWM signal is less than the threshold duty cycle.