Systems and methods for intelligent dimming control using TIRAC dimmers

1. An apparatus for a power conversion system, the apparatus comprising:

a process-and-drive component configured to receive an input signal associated with a TRIAC dimmer and output a drive signal to a switch to affect a current that flows through a primary winding of a power conversion system;

wherein:

the input signal includes a first pulse corresponding to a first input period, the first pulse being associated with a first pulse width; and

the first pulse width is larger than a first threshold for normal operation of the TRIAC dimmer;

wherein the process-and-drive component is further configured to:

process information associated with the first pulse width and a second threshold, the second threshold being larger than the first threshold; and

in response to the first pulse width being smaller than the second threshold, even if the first pulse width is still larger than the first threshold, maintain the drive signal at a first logic level without modulation to keep the switch open during at least the first input period.

2. The apparatus of claim 1 wherein the TRIAC dimmer is incapable of generating, with a rectifying bridge, a second pulse, the second pulse being associated with a second pulse width smaller than the first threshold.

3. The apparatus of claim 1 wherein the TRIAC dimmer is configured to generate, with a rectifying bridge, a second pulse associated with a second pulse width larger than the first threshold.

4. The apparatus of claim 1 wherein the process-and-drive component is further configured to provide a bleeding current to the TRIAC dimmer for the normal operation of the TRIAC dimmer so that an output current of the power conversion system does not change rapidly over a range of pulse widths for the input signal.

5. The apparatus of claim 1 , further comprising:

a reference signal generator configured to receive the input signal and generate a reference signal based on at least information associated with the input signal;

an error amplifier configured to receive the reference signal and a current sensing signal and generate an amplified signal based on at least information associated with the reference signal and the current sensing signal;

a modulation component configured to generate a modulation signal based on at least information associated with the amplified signal; and

a drive component configured to generate the drive signal based on at least information associated with the modulation signal.

6. The apparatus of claim 5 , wherein the reference signal generator includes:

a first logic control component configured to receive the input signal and generate a first signal based on at least information associated with the input signal; and

a reference signal modulator configured to receive the first signal and change the reference signal based on at least information associated with the first signal.

7. The apparatus of claim 6 wherein the drive component includes:

a second logic control component configured to receive the modulation signal and a dimming signal generated by the first logic control component and generate a second signal based on at least information associated with the modulation signal and the dimming signal; and

a gate driver configured to generate the drive signal based on at least information associated with the second signal.

8. The apparatus of claim 5 wherein the modulation component includes:

a multiplier configured to receive the amplified signal and the input signal and generate a multiplied signal based on at least information associated with the amplified signal and the input signal; and

a modulator configured to receive the multiplied signal and the current sensing signal and generate the modulation signal based on at least information associated with the multiplied signal and the current sensing signal.

9. The apparatus of claim 5 wherein the error amplifier is further configured to generate the amplified signal with a capacitor.

10. The apparatus of claim 1 wherein the process-and-drive component is further configured to, in response to the first pulse width being equal to or smaller than the second threshold, maintain the drive signal at the first logic level without modulation to keep the switch open to decrease an output current of the power conversion system.

11. The apparatus of claim 1 wherein:

the first pulse width corresponds to a phase angle associated with the first input period;

the phase angle is larger than a third threshold for normal operation of the TRIAC dimmer; and

the process-and-drive component is further configured to:

process information associated with the phase angle and a fourth threshold, the fourth threshold being larger than the third threshold; and

in response to the phase angle being smaller than the fourth threshold, even if the phase angle is still larger than the third threshold, maintain the drive signal at the first logic level without modulation to keep the switch open during at least the first input period.

12. A method for a power conversion system, the method comprising:

receiving an input signal associated with a TRIAC dimmer, the input signal including a first pulse corresponding to a first input period, the first pulse being associated with a first pulse width, the first pulse width being larger than a first threshold for normal operation of the TRIAC dimmer;

processing information associated with the input signal; and

outputting a drive signal to a switch to affect a current that flows through a primary winding of a power conversion system;

wherein the processing information associated with the input signal includes processing information associated with the first pulse width and a second threshold, the second threshold being larger than the first threshold; and

wherein the outputting a drive signal to a switch to affect a current that flows through a primary winding of a power conversion system includes, in response to the first pulse width being smaller than the second threshold, even if the first pulse width is still larger than the first threshold, maintaining the drive signal at a first logic level without modulation to keep the switch open during at least the first input period.