LED backlight modulation method based on duty cycle reference point setting

1. A light-emitting diode (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

;

and 0<X<1;

wherein T SW is a line selection duration of the row scan line; and T X is a time point at which the duty cycle reference point is located;

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

T rise =T SW ·(1− P )· X;

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

T fall =T SW ·[P +(1− P )· X];

wherein P is a duty cycle of the conduction of the channel; and

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

2. The LED backlight modulation method based on duty cycle reference point setting according to claim 1 , wherein a number of the row scan lines is same as a number of LED strings in the LED string channel.

3. 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 T SW is a line selection duration of the row scan line; and T X is a time point at which the duty cycle reference point is located;

when a conduction duration of the LED string channel is T CH and a conduction duty cycle of the channel is P,

T CH =T SW ·P;

if T CH ≤T SW ·(1− X ),

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

T rise =T SW ·X , and

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

T fall =T SW ·[P+X],

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

T rise =T SW ·(1− P ), and

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

T fall =T SW ; and

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

4. The LED backlight modulation method based on duty cycle reference point setting according to claim 3 , wherein a number of the row scan lines is same as a number of LED strings in the LED string channel.

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 T SW is a line selection duration of the row scan line; and T X is a time point at which the duty cycle reference point is located;

when a conduction duration of the LED string channel is T CH and a conduction duty cycle of the channel is P,

T CH =T SW ·P;

if T CH ≤T SW ·X,

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

T rise =T SW ·( X−P ), and

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

T fall =T SW ·X

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

T rise =0, and

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

T fall =T SW ·P ; and

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

6. The LED backlight modulation method based on duty cycle reference point setting according to claim 5 , wherein a number of the row scan lines is same as a number of LED strings in the LED string channel.