LED driver apparatus

1. A light emitting diode (LED) driver apparatus, comprising:

a pulse width modulation (PWM) signal generation unit configured to generate a PWM signal using an oscillator having a preset frequency;

a direct current (DC)-DC converter configured to provide a driving voltage to an LED array using the generated PWM signal;

an LED driving unit configured to drive the LED array using a dimming signal; and

a synchronization unit configured to reset a clock signal of the oscillator by synchronizing the oscillator to restart at a point in which a feedback voltage of the LED array is equal to or less than a preset first reference voltage.

2. The LED driver apparatus as claimed in claim 1 , wherein the synchronization unit includes a comparator configured to output a high level signal as a reset signal of the oscillator when the feedback voltage of the LED array is equal to or lower than the preset first reference voltage.

3. The LED driver apparatus as claimed in claim 1 , wherein the preset first reference voltage is greater than the feedback voltage at a normal operation of the LED array.

4. The LED circuit apparatus as claimed in claim 1 , wherein the LED driving unit is further configured to drive a plurality of LED arrays,

wherein the synchronization unit comprises:

a plurality of comparators, each comparator configured to output a high level signal when the feedback voltage of corresponding one of the plurality of LED arrays is equal to or lower than the preset first reference voltage;

an OR gate configured to receive output signals of the plurality of comparators and output a logic-OR result; and

a pulse output unit configured to receive an output signal of the OR gate and output a pulse signal corresponding to the output signal of the OR gate as a reset signal from the oscillator.

5. A light emitting diode (LED) driver apparatus, comprising:

a pulse width modulation (PWM) signal generation unit configured to generate a PWM signal using an oscillator having a preset frequency;

a direct current (DC)-DC converter configured to provide a driving voltage to an LED array using the generated PWM signal;

an LED driving unit configured to drive the LED array using a dimming signal; and

a synchronization unit configured to reset a clock signal of the oscillator in response to a current provided to the LED array being equal to or greater than a preset first reference current.

6. The LED driver apparatus as claimed in claim 5 , wherein the synchronization unit includes a current comparator configured to output a high level signal as a reset signal of the oscillator when the current provided to the LED array is equal to or greater than the preset first reference current.

7. The LED driver apparatus as claimed in claim 6 , wherein the current comparator comprises:

a current source configured to output the preset first reference current;

a transistor configured to receive a feedback voltage from the LED array at a drain thereof;

first and second resistors operatively connected in series between the current source and a ground terminal;

a third resistor arranged between a source of the transistor and the ground terminal;

a first operational amplifier of which a non-inverting terminal operatively connected to a first node commonly connected to the current source and one terminal of the first resistor, an inverting terminal operatively connected to a second node, which is commonly connected to a source of the transistor and the third resistor, and an output terminal operatively connected to a gate of the transistor; and

a second operational amplifier comprising an inverting terminal operatively connected to a third node, which is commonly connected to another terminal of the first resistor and one terminal of the second resistor, and a non-inverting terminal operatively connected to the second node, which is commonly connected to the source of the transistor and the third resistor, and configured to output an input difference between the non-inverting terminal and the inverting terminal as the reset signal from the oscillator.

8. The LED driver apparatus as claimed in claim 5 , wherein the preset first reference current is lower than a constant current at a normal operation of the LED array.

9. The LED driver apparatus as claimed in claim 5 , wherein the LED driving unit is further configured to drive a plurality of LED arrays,

wherein the synchronization unit comprises:

a plurality of current comparators, each current comparator configured to output a high level signal when a current flowing in one of the corresponding plurality of LED arrays is equal to or greater than the preset first reference current;

an OR gate configured to receive output signals from the plurality of current comparators and output a logic-OR result; and

a pulse output unit configured to receive an output signal from the OR gate and output a pulse signal corresponding to the output signal from the OR gate as the reset signal from the oscillator.

10. A light emitting diode (LED) driver apparatus, comprising:

a synchronization unit configured to

measure a feedback voltage of an LED array or a constant current flowing through the LED array to determine a point in time to drive the LED array,

generate a reset signal to an oscillator at a pulse width modulation (PWM) signal generation unit at the point in time when the LED array is driven,

generate the reset signal to reset a clock signal of the oscillator in response to the feedback voltage of the LED array being equal to or lower than a preset first reference voltage, and

generate the reset signal to the oscillator in response to the current provided to the LED array being equal to or greater than a preset first reference current to maintain a constant output voltage and a constant output current.

11. The LED driver apparatus as claimed in claim 10 , wherein the pulse width modulation (PWM) signal generation unit is configured to generate a PWM signal using the oscillator having a preset frequency.

12. The LED driver apparatus as claimed in claim 11 , further comprising:

a direct current (DC)-DC converter configured to provide a driving voltage to the LED array using the generated PWM signal; and

an LED driving unit configured to drive the LED array using a dimming signal.

13. The LED driver apparatus as claimed in claim 10 , wherein the preset first reference voltage is greater than the feedback voltage at a normal operation of the LED array.

14. The LED circuit apparatus as claimed in claim 12 , wherein the LED driving unit is further configured to drive a plurality of LED arrays,

wherein the synchronization unit comprises:

a plurality of comparators, each comparator configured to output a high level signal when the feedback voltage of corresponding one of the plurality of LED arrays is equal to or lower than the preset first reference voltage;

an OR gate configured to receive output signals of the plurality of comparators and output a logic-OR result; and

a pulse output unit configured to receive an output signal of the OR gate and output a pulse signal corresponding to the output signal of the OR gate as the reset signal from the oscillator.

15. The LED driver apparatus as claimed in claim 10 , wherein the synchronization unit comprises a current comparator comprising:

a current source configured to output the preset first reference current;

a transistor configured to receive a feedback voltage from the LED array at a drain thereof;

first and second resistors operatively connected in series between the current source and a ground terminal;

a third resistor arranged between a source of the transistor and the ground terminal;

a first operational amplifier of which a non-inverting terminal operatively connected to a first node commonly connected to the current source and one terminal of the first resistor, an inverting terminal operatively connected to a second node, which is commonly connected to a source of the transistor and the third resistor, and an output terminal operatively connected to a gate of the transistor; and

a second operational amplifier comprising an inverting terminal operatively connected to a third node, which is commonly connected to another terminal of the first resistor and one terminal of the second resistor, and a non-inverting terminal operatively connected to the second node, which is commonly connected to the source of the transistor and the third resistor, and configured to output an input difference between the non-inverting terminal and the inverting terminal as the reset signal from the oscillator.

16. The LED driver apparatus as claimed in claim 10 , wherein the preset first reference current is lower than a constant current at a normal operation of the LED array.

17. The LED driver apparatus as claimed in claim 12 , wherein the LED driving unit is further configured to drive a plurality of LED arrays,

wherein the synchronization unit comprises:

a plurality of current comparators, each current comparator configured to output a high level signal when a current flowing in one of the corresponding plurality of LED arrays is equal to or greater than the preset first reference current;

an OR gate configured to receive output signals from the plurality of current comparators and output a logic-OR result; and

a pulse output unit configured to receive an output signal from the OR gate and output a pulse signal corresponding to the output signal from the OR gate as the reset signal from the oscillator.