METHOD OF DRIVING LIGHT-SOURCE AND DISPLAY APPARATUS FOR PERFORMING THE METHOD

• US 20170092204A1
• Filed: 12/09/2016
• Published: 03/30/2017
• Est. Priority Date: 06/01/2012
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Group)
• Original Assignee: Samsung Display Company Limited (Samsung Group)
• Inventors: KIM, Seung-Wan, CHOI, Min-Soo, LEE, Gwang-Teak, IM, Tae-Gon, KIM, Myoung-Soo, LEE, Hwan-Woong, CHOI, Seung-Young
• Granted Patent: US 10,854,149 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G09G 2300/023 Display panel composed of stacked panels
• CPC Class Codes: G09G 2310/0289 Details of voltage level shifters arranged for use in a driving circuit
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 5/10 Intensity circuits
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]
• CPC Class Codes: H05B 45/345 Current stabilisation; Maintaining constant current
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A method of driving a light-source module includes adjusting a frequency of a boosting switching signal based on a dimming signal which controls luminance of a light-emitting diode (“LED”) string of the light-source module, where the LED string comprises a plurality of LEDs connected to each other in series, and controlling a main transistor in response to the boosting switching signal to transfer a driving voltage to the LED string.

Claims

1. A method of driving a light-source module, the method comprising:

adjusting a frequency of a pulse width modulation (“

PWM”

) control signal having a current control pulse to control a light-emitting diode (“

LED”

) string of the light-source module, wherein the LED string comprises a plurality of LEDs connected to each other in series; and

controlling a control switching element, which is connected to an end portion of the LED string, in response to the PWM control signal.

2. The method of claim 1, wherein the adjusting the frequency of the PWM control signal comprises:

generating a chopping wave of a first driving frequency when a level of the dimming signal, which controls luminance of the LED string, is greater than a preset value; and

adjusting the frequency of the PWM control signal to generate a first PWM control signal using the chopping wave of the first driving frequency.

4. The method of claim 1, wherein the adjusting the frequency of the PWM control signal comprises:

generating a chopping wave of a first driving frequency when a level of a detection voltage detected from the end portion of the LED string is substantially equal to a preset value; and

adjusting the frequency of the PWM control signal to generate a first PWM control signal using the chopping wave of the first driving frequency.

5. The method of claim 4, wherein the adjusting the frequency of the PWM control signal comprises:

generating a chopping wave of a second driving frequency when the level of the detection voltage is different from the preset value; and

adjusting the frequency of the PWM control signal to generate a second PWM control signal using the chopping wave of the second driving frequency.

3. The method of claim 3, wherein the adjusting the frequency of the PWM control signal comprises:

generating a chopping wave of a second driving frequency higher than the first driving frequency when the level of the dimming signal, which controls luminance of the LED string, is less than the preset value; and

adjusting the frequency of the PWM control signal to generate a second PWM control signal using the chopping wave of the second driving frequency.

6. A display apparatus comprising:

a display panel configured to receive an image signal and to display an image corresponding to the image signal;

a light-source module comprising a light-emitting diode (“

LED”

) string, wherein the LED string comprises a plurality of LEDs connected to each other in series; and

a light-source driving part comprising a main transistor, configured to adjust a frequency of a pulse width modulation (“

PWM”

) control signal having a current control pulse to control the LED string, and configured to control a control switching element, which is connected to an end portion of the LED string, in response to the PWM control signal.

7. The display apparatus of claim 6, wherein the light-source driving part comprises:

an image analyzing part configured to analyze the image signal and to determine a target luminance value of the LED string;

a dimming level determining part configured to determine a dimming signal of the LED string using the target luminance value; and

a driving signal generating part comprising the main transistor, configured to adjust the driving frequency of the boosting switching signal based on the dimming signal and configured to drive the main transistor in response to the boosting switching signal.

8. The display apparatus of claim 7, wherein the driving signal generating part comprises:

a frequency oscillating part configured to generate a chopping wave;

a frequency modulating part configured to modulate a driving frequency of the chopping wave to a first driving frequency, or a second driving frequency higher than the first driving frequency, based on the dimming signal which controls luminance of the LED string; and

a constant current control part configured to generate first or second PWM control signal as the PWM control signal based on the chopping wave of the first or second driving frequency.

9. The display apparatus of claim 8, wherein the frequency modulating part comprises:

an input part configured to receive the dimming signal;

a voltage dividing part configured to divide a voltage of the dimming signal;

a diode part connected to the input part and the voltage dividing part;

an oscillating transistor configured to operate in response to a divided voltage received from the voltage dividing part; and

a resistor part comprising a second resistor connected in parallel to a first resistor of the frequency oscillating part, which determines the driving frequency of the chopping wave.

10. The display apparatus of claim 7, wherein the driving signal generating part comprises:

a frequency oscillating part configured to generate a chopping wave;

a frequency modulating part configured to modulate a driving frequency of the chopping wave to a first driving frequency or a second driving frequency higher than the first driving frequency, based on a detection voltage detected from the end portion of the LED string; and

a constant current control part configured to generate first or second PWM control signal as the PWM control signal based on the chopping wave of the first or second driving frequency.

11. The display apparatus of claim 10, wherein the frequency modulating part comprises:

an input part configured to receive the detection voltage;

a voltage dividing part configured to divide the detection voltage;

a diode part connected to the input part and the voltage dividing part;

an oscillating transistor configured to operate in response to a divided voltage received from the voltage dividing part; and

a resistor part comprising a second resistor connected in parallel to a first resistor of the frequency oscillating part, which determines the driving frequency of the chopping wave.