US 10,462,873 B2
Backlight circuit, electronic device, and backlight adjustment method
Junqing Shuai, Beijing (CN); Haojing Zhang, Beijing (CN); Jianfei Chu, Beijing (CN); and Shilei Wang, Beijing (CN)
Assigned to Huawei Technologies Co., Ltd., Shenzhen (CN)
Appl. No. 16/60,442
Filed by HUAWEI TECHNOLOGIES CO., LTD., Shenzhen, Guangdong (CN)
PCT Filed Dec. 9, 2015, PCT No. PCT/CN2015/096869
§ 371(c)(1), (2) Date Jun. 8, 2018,
PCT Pub. No. WO2017/096567, PCT Pub. Date Jun. 15, 2017.
Prior Publication US 2018/0368220 A1, Dec. 20, 2018
Int. Cl. H05B 33/08 (2006.01); G09G 3/36 (2006.01); G09G 3/34 (2006.01)
CPC H05B 33/086 (2013.01) [G09G 3/3406 (2013.01); G09G 3/36 (2013.01); H05B 33/0845 (2013.01); G09G 2320/064 (2013.01); G09G 2320/0633 (2013.01)] 19 Claims
OG exemplary drawing
 
1. A backlight circuit, wherein the backlight circuit comprises a backlight power supply chip and an adjustable resistor circuit;
the backlight power supply chip comprises a set pin configured to set a reference current, an input pin, and an output pin;
the adjustable resistor circuit comprises a first end connected to the set pin and a second end connected to a ground, wherein the adjustable resistor circuit further comprises a first resistor branch and a second resistor branch, wherein the first resistor branch and the second resistor branch have different resistance values used to generate different reference currents, and wherein a resistance value R1 of the first resistor branch and a resistance value R2 of the second resistor branch meet one of the following conditions:
R1≥R2×maximum duty cycle2/minimum duty cycle1; and
R1≤R2×minimum duty cycle1/maximum duty cycle2,
wherein the minimum duty cycle1 is a minimum duty cycle when the set pin is connected to the first resistor branch, and wherein the maximum duty cycle2 is a maximum duty cycle when the set pin is connected to the second resistor branch;
the adjustable resistor circuit further comprises a control end, wherein the control end is configured to receive a switching signal, and the adjustable resistor circuit selects, according to the switching signal, a resistor branch from the first resistor branch and the second resistor branch to connect to the set pin for generating the reference current; and
the backlight power supply chip is configured to generate a drive current based on the reference current and a duty cycle of a pulse-width modulation (PWM) signal, wherein the PWM signal received by the input pin, and wherein the backlight power supply chip is further configured to output the drive current by using the output pin, wherein the drive current is used to drive a backlight source to emit.