Signal generating method and circuit for controlling dimming of LED

1. A signal generating method for controlling dimming of an LED, comprising:

generating a first pulse signal, the first pulse signal comprising information of P bits gray levels, P being an integer, wherein the minimum pulse-width of the first pulse is N, N is an integer;

generating a second pulse signal after the first pulse signal, the second pulse signal comprising information of Q bits gray levels, Q being an integer, wherein the amplitude of the second pulse signal is different from the amplitude of the first pulse signal, the minimum pulse-width of the second pulse is the same as the minimum pulse-width of the first pulse; and

utilizing the first pulse signal and the second pulse signal to represent gray levels information of the LED;

wherein the duty ratio of the first pulse signal is between 0 and 2 P /N for representing information of P bits gray levels, the duty ratio of the second pulse signal is between 0 and 2 Q /N for representing information of Q bits gray levels.

2. The signal generating method for controlling dimming of an LED according to claim 1 , wherein the resolution of the gray levels information of the LED is higher than P bits or Q bits, but lower than or equal to P+Q bits.

3. The signal generating method for controlling dimming of an LED according to claim 1 , wherein the first pulse signal and the second pulse signal are pulse width modulation (PWM) signals.

4. The signal generating method for controlling dimming of an LED according to claim 3 , wherein the length of the first pulse signal and the length of the second pulse signal are the same.

5. The signal generating method for controlling dimming of an LED according to claim 1 , wherein the amplitude of the second pulse signal is smaller than the amplitude of the first pulse signal.

6. The signal generating method for controlling dimming of an LED according to claim 1 , wherein the first pulse signal is a pulse width modulation (PWM) signal, the length of the first pulse signal is 2 P /N, the duty ratio of the first pulse signal is between 0 and 2 P /N for representing information of P bits gray levels, the second pulse signal is a pulse amplitude modulation (PAM) signal, the amplitude of the second pulse signal is between 0 and 2 Q /N for representing information of Q bits gray levels.

7. The signal generating method for controlling dimming of an LED according to claim 1 , wherein the first pulse signal is a pulse amplitude modulation (PAM) signal, the amplitude of the first pulse signal is between 0 and 2 P /N for representing information of P bits gray levels, the second pulse signal is a pulse width modulation (PWM) signal, the length of the second pulse signal is 2 Q /N, the duty ratio of the second pulse signal is between 0 and 2 Q /N for representing information of Q bits gray levels.

8. A signal generating circuit for controlling dimming of an LED, comprising:

a pulse generator, generating a first pulse signal and a second pulse signal after the first pulse signal, the minimum pulse-width of the pulse generator being N, N being an integer, the first pulse signal comprising information of P bits gray levels, P being an integer, the second pulse signal comprising information of Q bits gray levels, Q being an integer, wherein the amplitude of the second pulse signal is different from the amplitude of the first pulse signal; and

a driving circuit, coupled to the pulse generator, controlling gray levels of the LED according to gray levels information represented by the first pulse signal and the second pulse signal;

wherein the duty ratio of the first pulse signal is between 0 and 2 P /N for representing information of P bits gray levels, the duty ratio of the second pulse signal is between 0 and 2 Q /N for representing information of Q bits gray levels.

9. The signal generating circuit for controlling dimming of an LED according to claim 8 , wherein the resolution of the gray levels information of the LED is higher than P bits or Q bits, but lower than or equal to P+Q bits.

10. The signal generating circuit for controlling dimming of an LED according to claim 8 , wherein the first pulse signal and the second pulse signal are pulse width modulation (PWM) signals.

11. The signal generating circuit for controlling dimming of an LED according to claim 8 , wherein the length of the first pulse signal and the length of the second pulse signal are the same.

12. The signal generating circuit for controlling dimming of an LED according to claim 8 , wherein the amplitude of the second pulse signal is smaller than the amplitude of the first pulse signal.

13. The signal generating circuit for controlling dimming of an LED according to claim 8 , wherein the first pulse signal is a pulse width modulation (PWM) signal, the length of the first pulse signal is 2 P /N, the duty ratio of the first pulse signal is between 0 and 2 P /N for representing information of P bits gray levels, the second pulse signal is a pulse amplitude modulation (PAM) signal, the amplitude of the second pulse signal is between 0 and 2 Q /N for representing information of Q bits gray levels.

14. The signal generating circuit for controlling dimming of an LED according to claim 8 , wherein the first pulse signal is a pulse amplitude modulation (PAM) signal, the amplitude of the first pulse signal is between 0 and 2 P /N for representing information of P bits gray levels, the second pulse signal is a pulse width modulation (PWM) signal, the length of the second pulse signal is 2 Q /N, the duty ratio of the second pulse signal is between 0 and 2 Q /N for representing information of Q bits gray levels.