Patent ID: 11908397
Assignee: X-SIGNAL INTEGRATED CO., LTD.
Field: Audio-visual technology (Electrical engineering)
Classification: CPC G  Y | IPC G

Claim 4:
5. An LED backlight modulation method based on duty cycle reference point setting, the LED backlight modulation method being applied to an LED backlight control circuit with row and column scan lines, the LED backlight control circuit with row and column scan lines comprising a plurality of LED string channels, each consisting of a predetermined number of multiple LED strings, and for all the LED strings in each LED string channel, the LED strings each being connected at high potential terminals thereof to unique one of a plurality of row scan lines, each of the row scan lines being provided with a switching device; wherein:
a duty cycle reference point is set for each LED string channel, a duty cycle reference point being located in a selected duration of the row scan line, and a duty cycle reference point percentage X of the duty cycle reference point being expressed as:, X
   =
   
    
     T
     X
    
    
     T
     SW
    
   
  
  ;
 

wherein TSW is a line selection duration of the row scan line; and TX is a time point at which the duty cycle reference point is located;
when a conduction duration of the LED string channel is TCH and a conduction duty cycle of the channel is P,

TCH=TSW·P; 

if TCH≤TSW·X, 

then a rising edge time point position Trise of the conduction duration of the LED string channel is expressed as:

Trise=TSW·(X−P), and

a falling edge time point position Tfall of the conduction duration of the LED string channel is expressed as:

Tfall=TSW·X 

otherwise, the rising edge time point position Trise of the conduction duration of the LED string channel is expressed as:

Trise=0, and

the falling edge time point position Tfall of the conduction duration of the LED string channel is expressed as:

Tfall=TSW·P; and

different duty cycle reference point percentages X are set for the LED string channels.