Circuit and method for generating PWM signal for DC-DC converter using dimming signal and LED driving circuit for backlight having the same

1. A pulse width modulation (PWM) signal generating circuit configured to generate a PWM signal for a DC-DC converter using a dimming signal, the PWM signal generating circuit comprising:

a normal PWM signal generator configured to generate a normal PWM signal based on a clock signal provided to the DC-DC converter; and

a compensation PWM signal generator configured to generate a compensation PWM signal based on the clock signal and the dimming signal.

2. The PWM signal generating circuit as claimed in claim 1 , wherein the normal PWM signal generator is further configured to generate the normal PWM signal during a first level period of the dimming signal.

3. The PWM signal generating circuit as claimed in claim 2 , wherein the first level period of the dimming signal comprises a high-level period of the dimming signal.

4. The PWM signal generating circuit as claimed in claim 1 , wherein the compensation PWM signal generator is further configured to generate at least one compensation PWM signal during a second level period of the dimming signal.

5. The PWM signal generating circuit as claimed in claim 4 , wherein the second level period of the dimming signal comprises a low-level period.

6. The PWM signal generating circuit as claimed in claim 1 , wherein the compensation PWM signal has a pulse width that is the same as a pulse width of the normal PWM signal.

7. The PWM signal generating circuit as claimed in claim 6 , wherein the compensation PWM signal has a pulse width that is the same as a pulse width of the clock signal.

8. The PWM signal generating circuit as claimed in claim 1 , wherein the compensation PWM signal generator comprises:

a signal detector configured to:

detect a low-level period of the dimming signal; and

generate a detection signal; and

a signal generator configured to:

receive the detection signal from the signal detector; and

generate the compensation PWM signal.

9. The PWM signal generating circuit as claimed in claim 8 , wherein the signal detector comprises a flip-flop configured to:

detect the low-level period of the dimming signal at a rising edge of the clock signal; and

generate the detection signal.

10. The PWM signal generating circuit as claimed in claim 8 , wherein the signal generator comprises a flip-flop configured to:

receive the detection signal from the signal detector; and

generate the compensation PWM signal.

11. The PWM signal generating circuit as claimed in claim 10 , wherein the flip-flop of the signal generator is reset at a negative edge of the clock signal.

12. The PWM signal generating circuit as claimed in claim 11 , wherein the compensation PWM signal has a pulse width that is the same as a pulse width of the normal PWM signal.

13. The PWM signal generating circuit as claimed in claim 1 , further comprising:

an output unit configured to:

receive the normal PWM signal from the normal PWM signal generator and the compensation PWM signal from the compensation PWM signal generator; and

provide the normal PWM signal and the compensation PWM signal to the DC-DC converter.

14. The PWM signal generating circuit as claimed in claim 13 , wherein the output unit comprises an adder configured to:

add the normal PWM signal received from the normal PWM signal generator and the compensation PWM signal received from the compensation PWM signal generator; and

provide an added PWM signal to the DC-DC converter as the PWM signal.

15. A light emitting diode (LED) driving circuit for backlight, comprising:

a PWM signal generator configured to generate a PWM signal using a clock signal and a dimming signal;

a DC-DC converter configured to provide an output voltage to an LED of an LED array for backlight, based on the PWM signal generated by the PWM signal generator; and

an LED driving unit configured to generate a driving signal for driving the LED using the dimming signal, wherein:

the PWM signal generator comprises:

a normal PWM signal generator configured to generate a normal PWM signal based on the clock signal during a high-level period of the dimming signal; and

a compensation PWM signal generator configured to generate a compensation PWM signal based on the clock signal during a low-level period of the dimming signal.

16. The LED driving circuit as claimed in claim 15 , wherein the compensation PWM signal has a pulse width that is the same as a pulse width of the normal PWM signal.

17. The LED driving circuit as claimed in claim 16 , wherein the compensation PWM signal has a pulse width that is the same as a pulse width of the clock signal.

18. The LED driving circuit as claimed in claim 15 , wherein the compensation PWM signal generator comprises:

a RS flip-flop configured to:

generate a low-level period of the dimming signal at a rising edge of the clock signal; and

generate a detection signal; and

a D flip-flop configured to generate an output signal at the rising edge of the clock signal based on the detection signal, the D flip-flop being reset at a falling edge of the clock signal to generate the compensation PWM signal.

19. The LED driving circuit as claimed in claim 15 , further comprising:

an adder configured to:

add the normal PWM signal received from the normal PWM signal generator and the compensation PWM signal received from the compensation PWM signal generator; and

provide an added PWM signal to the DC-DC converter.

20. A method configured to generate a PWM signal for a DC-DC converter using a dimming signal, the method comprising:

generating a normal PWM signal based on a clock signal during a first period of a dimming signal;

providing the normal PWM signal to the DC-DC converter; and

generating a compensation PWM signal based on the clock signal during a second period of the dimming signal.

21. The method as claimed in claim 20 , wherein the generating of the normal PWM signal comprises generating the normal PWM signal during a high-level period of the dimming signal.

22. The method as claimed in claim 20 , wherein the generating of the compensation PWM signal comprises generating the compensation PWM signal during a low-level period of the dimming signal.

23. The method as claimed in claim 20 , wherein the compensation PWM signal has a pulse width that is the same as a pulse width of the normal PWM signal.