Backlight unit, display apparatus having the same and operating method of backlight unit

1. A backlight unit comprising:

a power converter configured to generate a light-source power voltage according to a voltage control signal;

an LED string connected to the light-source power voltage;

a short-circuit detector configured to receive the light-source power voltage and to enable a short-circuit signal; and

a light source controller configured to generate the voltage control signal to interrupt generation of the light-source power voltage when the short-circuit signal is enabled, wherein the short-circuit detector comprises:

a voltage divider configured to divide the light-source power voltage to output a detection voltage; and

a comparing circuit configured to generate a reference voltage having a reference voltage level corresponding to a voltage level of the detection voltage among a plurality of reference voltage levels, and to enable the short-circuit signal in accordance with a result of a comparison of the reference voltage level with the detection voltage, and

wherein the comparing circuit comprises:

a first comparator configured to compare the voltage level of the detection voltage with that of a first voltage, and to output a first comparison signal;

a second comparator configured to compare the voltage level of the detection voltage with that of a second voltage different than the first voltage, and to output a second comparison signal;

an adding circuit configured to output the reference voltage corresponding to the first comparison signal and the second comparison signal; and

a third comparator configured to compare a voltage level of the reference voltage with that of the detection voltage, and to enable the short-circuit signal in accordance with the result of the comparison.

2. The backlight unit of claim 1 , wherein the adding circuit is configured to add the first comparison signal, the second comparison signal, and a bias voltage to output the reference voltage.

3. The backlight unit of claim 2 , wherein a voltage level of the second voltage is higher than that of the first voltage.

4. The backlight unit of claim 1 , wherein the comparing circuit is configured to:

output the reference voltage with a first reference voltage level when the detection voltage is lower than a first voltage level;

output the reference voltage with a second reference voltage level when the detection voltage is higher than the first voltage level and lower than a second voltage level; and

output the reference voltage with a third reference voltage level when the detection voltage is higher than the second voltage level, and

wherein the second voltage level is higher than the first voltage level.

5. The backlight unit of claim 1 , wherein one end of the LED string is connected to the light-source power voltage and another end of the LED string is connected to the light source controller.

6. The backlight unit of claim 1 , wherein the voltage divider comprises:

a first resistor connected between the light-source power voltage and a first node; and

a second resistor connected between the first node and a ground voltage, and

wherein the voltage divider is configured to output a voltage at the first node as the detection voltage.

7. A display apparatus comprising: a display panel comprising a plurality of pixels;

a drive circuit configured to control the display panel to display an image; and

a backlight configured to supply light to the display panel, wherein the backlight comprises:

a power converter configured to generate a light-source power voltage according to a voltage control signal; an LED string connected to the light-source power voltage;

a short-circuit detector configured to receive the light-source power voltage and to enable a short-circuit signal; and

a light source controller configured to generate the voltage control signal to interrupt generation of the light-source power voltage when the short-circuit signal is enabled, and wherein the short-circuit detector comprises:

a voltage divider configured to divide the light-source power voltage to output a detection voltage; and a comparing circuit configured to generate a reference voltage having a reference voltage level corresponding to a voltage level of the detection voltage among a plurality of reference voltage levels the detection voltage among a plurality of reference voltage levels, and to enable the short-circuit signal in accordance with a result of a comparison of the reference voltage level with the detection voltage, and

wherein the comparing circuit comprises:

a first comparator configured to compare the voltage level of the detection voltage with that of a first voltage to output a first comparison signal;

a second comparator configured to compare the voltage level of the detection voltage with that of a second voltage different than the first voltage to output a second comparison signal;

an adding circuit configured to output the reference voltage corresponding to the first comparison signal and the second comparison signal; and

a third comparator configured to compare a voltage level of the reference voltage with that of the detection voltage, and to enable the short-circuit signal in accordance with the result of the comparison.

8. The display apparatus of claim 7 , wherein the adding circuit is configured to add the first comparison signal, the second comparison signal, and a bias voltage to output the reference voltage.

9. The display apparatus of claim 8 , wherein a voltage level of the second voltage is higher than that of the first voltage.

10. An operation method of a backlight unit, the method comprising:

providing a light-source power voltage;

detecting a voltage level of the light-source power voltage;

selecting a reference voltage level for a reference voltage from a plurality of reference voltage levels in accordance with a voltage level of a detection voltage;

outputting the reference voltage having the selected reference voltage level;

comparing the reference voltage with the detection voltage and enabling a short-circuit signal in accordance with a result of the comparison; and interrupting generation of the light-source power voltage when the short-circuit signal is enabled,

wherein selecting the reference voltage level comprises comparing the voltage level of the detection voltage with that of a first voltage to output a first comparison signal, and comparing the voltage level of the detection voltage with that of a second voltage different than the first voltage to output a second comparison signal; and

wherein outputting the reference voltage having the selected reference voltage level comprises outputting the reference voltage corresponding to the first comparison signal and the second comparison signal.

11. The operation method of claim 10 , wherein the outputting of the reference voltage comprises:

outputting the reference voltage with a first level when the detection voltage is lower than a first voltage level;

outputting the reference voltage with a second level when the detection voltage is higher than the first voltage level and lower than a second voltage level; and

outputting the reference voltage with a third level when the detection voltage is higher than the second voltage level, and

wherein the second voltage level is higher than the first voltage level.