BACKLIGHT UNIT AND DISPLAY DEVICE INCLUDING THE SAME
A backlight unit includes: a light source unit including at least one light emitting diode (“LED”) string; a driving current controller which is connected to a cathode terminal of the at least one LED string and controls a driving current which flows through the at least one LED string; a feedback unit which generates a feedback signal based on a dimming input signal and a voltage of the cathode terminal of the at least one LED string; and a direct current to direct current (“DC-DC”) converter which generates a driving voltage in response to the feedback signal and provides the driving voltage to the light source unit.
1 . A backlight unit comprising:
a light source unit including at least one light emitting diode string;
a driving current controller which is connected to a cathode terminal of the at least one light emitting diode string and controls a driving current which flows through the at least one light emitting diode string;
a feedback unit which generates a feedback signal based on a dimming input signal and a voltage of the cathode terminal of the at least one light emitting diode string; and
a direct current to direct current converter which generates a driving voltage in response to the feedback signal and provides the driving voltage to the light source unit.
2 . The backlight unit of claim 1 , wherein
the feedback unit includes:
a first dimming signal converter which converts the dimming input signal according to a first function and generates a conversion dimming signal;
at least one diode which is connected to the cathode terminal of the at least one light emitting diode string; and
a first amplifier which receives the conversion dimming signal and an output voltage of the at least one diode and generates the feedback signal, and inputs the feedback signal to the direct current to direct current converter.
3 . The backlight unit of claim 2 , wherein
the first function has an output which decreases according to an increase of the dimming input signal.
4 . The backlight unit of claim 3 , wherein
the at least one diode of the feedback unit is connected to a reference voltage via a resistor.
5 . The backlight unit of claim 4 , wherein
the driving current controller includes:
a second dimming signal converter which converts the dimming input signal according to a second function and generates a dimming reference signal,
a transistor including a drain terminal which is connected to the cathode terminal of the at least one light emitting diode string; and
a second amplifier which receives the dimming reference signal and a voltage of a source terminal of the transistor and generates a control signal, and inputs the control signal to a control terminal of the transistor.
6 . The backlight unit of claim 5 , wherein
the second function has an output which increases according to an increase of the dimming input signal.
7 . The backlight unit of claim 6 , wherein
the driving current controller further includes a resistor which is connected to the source terminal of the transistor.
8 . The backlight unit of claim 7 , wherein
a drain-source voltage of the transistor increases as the dimming input signal decreases.
9 . The backlight unit of claim 1 , wherein
the driving current controller includes:
a second dimming signal converter which converts the dimming input signal according to a second function and generates a dimming reference signal,
a transistor including a drain terminal which is connected to the cathode terminal of the at least one light emitting diode string; and
a second amplifier which receives the dimming reference signal and a voltage of a source terminal of the transistor and generates a control signal, and inputs the control signal to a control terminal of the transistor.
10 . The backlight unit of claim 9 , wherein
the second function has an output which increases according to an increase of the dimming input signal.
11 . The backlight unit of claim 10 , wherein
the driving current controller further includes a resistor which is connected to the source terminal of the transistor.
12 . The backlight unit of claim 11 , wherein
a drain-source voltage of the transistor increases as the dimming input signal decreases.
13 . A display device comprising:
a display panel including a plurality of pixels;
a light source unit which generates and provides light to the display panel, and includes at least one light emitting diode string; and
a light source driver which drives the light source unit,
wherein the light source driver includes:
a driving current controller which is connected to a cathode terminal of the at least one light emitting diode string and controls a driving current which flows through the light emitting diode string;
a feedback unit which generates a feedback signal based on a dimming input signal and a voltage of the cathode terminal of the at least one light emitting diode string; and
a direct current to direct current converter which generates a driving voltage in response to the feedback signal and provides the driving voltage to the light source unit.
14 . The display device of claim 13 , wherein
the feedback unit includes:
a first dimming signal converter which converts the dimming input signal according to a first function and generates a conversion dimming signal,
at least one diode which is connected to the cathode terminal of the at least one light emitting diode string, and
a first amplifier which receives the conversion dimming signal and an output voltage of the at least one diode and generates the feedback signal, and inputs the feedback signal to the direct current to direct current converter.
15 . The display device of claim 14 , wherein
the first function has an output which decreases according to an increase of the dimming input signal.
16 . The display device of claim 15 , wherein
the at least one diode of the feedback unit is connected to a reference voltage via a resistor.
17 . The display device of claim 13 , wherein
the driving current controller includes:
a second dimming signal converter which converts the dimming input signal according to a second function and generates a dimming reference signal;
a transistor including a drain terminal which is connected to the cathode terminal of the at least one light emitting diode string; and
a second amplifier which receives the dimming reference signal and a voltage of a source terminal of the transistor and generates a control signal, and inputs the control signal to a control terminal of the transistor.
18 . The display device of claim 17 , wherein
the second function has an output which increases according to an increase of the dimming input signal.
19 . The display device of claim 18 , wherein
the driving current controller further includes a resistor which is connected to the source terminal of the transistor.
20 . The display device of claim 13 , wherein
a drain-source voltage of the transistor increases as the dimming input signal decreases.