# US 11,908,397 B2 · LED backlight modulation method based on duty cycle reference point setting

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- Number: US 11,908,397 B2
- Document ID: US11908397B2
- Status: Granted
- Kind: B2
- Application number: 18/228,005
- Filed: 2023-07-31
- Published: 2023-11-23
- Granted: 2024-02-20
- Earliest claimed: 2022-03-07
- Assignees: X-Signal Integrated Co., Ltd.
- Applicants: X-Signal Integrated Co., Ltd.
- Inventors: Guanou Yang
- Web page: https://patentgrep.com/patent/US11908397B2

## CPC

- G09G 3/32: semiconductive, e.g. using light-emitting diodes [LED]
- G09G 3/342: {using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines}
- G09G 2310/08: Details of timing specific for flat panels, other than clock recovery
- G09G 2320/064: by time modulation of the brightness of the illumination source
- G09G 2330/025: Reduction of instantaneous peaks of current
- Y02B 20/30: Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

A light-emitting diode (LED) backlight modulation method based on duty cycle reference point setting is provided, and the LED backlight modulation method is applied to an LED backlight control circuit with row and column scan lines. Different duty cycle reference points are set for the LED string channels in the LED backlight control circuit in row-column scanning mode, whereby the LED string channels can be turned on or off at different time points during a turn-on duration of the row scan line to achieve lighting in the duty cycle, so as to realize the staggered setting of the turn-on time point and turn-off time point of each channel and avoid the need for large current jump at a power drive terminal.

## Claims

### Claim 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 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;
a rising edge time point position Trise of a conduction duration of the LED string channel is expressed as:
Trise=TSW·(1−P)·X;
a falling edge time point position Tfall of the conduction duration of the LED string channel is expressed as:
Tfall=TSW·[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.

### Claim 2 (depends on 1)

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.

### Claim 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 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·(1−X),
then a rising edge time point position Trise of the conduction duration of the LED string channel is expressed as:
Trise=TSW·X, and
a falling edge time point position Tfall of the conduction duration of the LED string channel is expressed as:
Tfall=TSW·[P+X],
otherwise, the rising edge time point position Trise of the conduction duration of the LED string channel is expressed as:
Trise=TSW·(1−P), and
the falling edge time point position Tfall of the conduction duration of the LED string channel is expressed as:
Tfall=TSW; and
different duty cycle reference point percentages X are set for the LED string channels.

### Claim 4 (depends on 3)

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.

### Claim 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.

### Claim 6 (depends on 5)

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.