Switch control systems for light emitting diodes and methods thereof

1. A system for controlling one or more light emitting diodes, the system comprising:

a current generator configured to generate a first current flowing through the one or more light emitting diodes, the one or more light emitting diodes being configured to receive a rectified voltage generated by a rectifying bridge coupled to a TRIAC dimmer;

a bleeder configured to receive the rectified voltage; and

a controller configured to:

receive a sensing voltage from the current generator, the sensing voltage indicating a magnitude of the first current;

receive an input voltage generated by a voltage divider, the voltage divider being configured to receive the rectified voltage, the input voltage indicating a magnitude of the rectified voltage; and

output a control signal to the bleeder;

wherein the controller is further configured to:

generate the control signal to turn off the bleeder if the input voltage satisfies a first condition so that the bleeder does not generate a second current, the second current being larger than zero in magnitude; and

generate the control signal to turn on the bleeder if the input voltage satisfies a second condition so that the bleeder generates the second current;

wherein the second condition is different from the first condition;

wherein:

the controller includes a flip-flop; and

the flip-flop is configured to directly output the control signal.

2. The system of claim 1 wherein the controller is further configured to:

generate the control signal at a first logic level from a first time to a second time, during which the input voltage is smaller than a reference voltage in magnitude;

generate the control signal at a second logic level from the second time to a third time, during which the input voltage is larger than the reference voltage in magnitude; and

generate the control signal at the first logic level from the third time to a fourth time, during which the input voltage is smaller than the reference voltage in magnitude;

wherein the first logic level and the second logic level are different.

3. The system of claim 2 wherein:

the control signal at the first logic level is configured to turn on the bleeder so that the bleeder generates the second current; and

the control signal at the second logic level is configured to turn off the bleeder so that the bleeder does not generate the second current.

4. The system of claim 1 wherein the rectifying bridge is coupled to the TRIAC dimmer through a fuse.

5. The system of claim 1 wherein:

the controller further includes a comparator;

the comparator is configured to generate a comparison signal based on the sensing voltage; and

the flip-flop is further configured to receive the comparison signal and generate the control signal based at least in part on the comparison signal.

6. A method for controlling one or more light emitting diodes, the method comprising:

generating a first current flowing through the one or more light emitting diodes, the one or more light emitting diodes being configured to receive a rectified voltage generated by a rectifying bridge coupled to a TRIAC dimmer;

receiving a sensing voltage, the sensing voltage indicating a magnitude of the first current;

receiving an input voltage, the input voltage indicating a magnitude of the rectified voltage; and

outputting, by a controller, a control signal to the bleeder;

wherein the outputting a control signal to the bleeder includes:

generating the control signal, by a flip-flop in the controller, to turn off the bleeder if the input voltage satisfies a first condition so that the bleeder does not generate a second current, the second current being larger than zero in magnitude;

generating, by the flip-flop in the controller, the control signal to turn on the bleeder if the input voltage satisfies a second condition so that the bleeder generates the second current; and

directly outputting, b the flip-flop in the controller, the control signal;

wherein the second condition is different from the first condition.

7. A system for controlling one or more light emitting diodes, the system comprising:

a current generator configured to generate a first current flowing through the one or more light emitting diodes, the one or more light emitting diodes being configured to receive a rectified voltage generated by a rectifying bridge coupled to a TRIAC dimmer;

a bleeder configured to receive the rectified voltage; and

a controller configured to:

receive a sensing voltage from the current generator, the sensing voltage indicating a magnitude of the first current;

receive an input voltage generated by a voltage divider, the voltage divider being configured to receive the rectified voltage, the input voltage indicating a magnitude of the rectified voltage; and

output a control signal to the bleeder;

wherein the controller is further configured to:

generate the control signal at a first logic level from a first tune to a second time, during which the input voltage is smaller than a reference voltage in magnitude;

generate the control signal at a second logic level from the second time to a third tune, during which the input voltage is larger than the reference voltage in magnitude; and

generate the control signal at the first logic level from the third time to a fourth time, during which the input voltage is smaller than the reference voltage in magnitude;

wherein the first logic level and the second logic level are different;

wherein:

the controller includes a flip-flop; and

the flip-flop is configured to directly output the control signal.

8. The system of claim 7 wherein:

the control signal at the first logic level is configured to turn on the bleeder so that the bleeder generates a second current; and

the control signal at the second logic level is configured to turn off the bleeder so that the bleeder does not generate the second current.

9. The system of claim 7 wherein the rectifying bridge is coupled to the TRIAC dimmer through a fuse.

10. A method for controlling one or more light emitting diodes, the method comprising:

generating a first current flowing through the one or more light emitting diodes, the one or more light emitting diodes being configured to receive a rectified voltage generated by a rectifying bridge coupled to a TRIAC dimmer;

receiving a sensing voltage, the sensing voltage indicating a magnitude of the first current;

receiving an input voltage, the input voltage indicating a magnitude of the rectified voltage; and

outputting, by a controller, a control signal to the bleeder;

wherein the outputting a control signal to the bleeder includes:

generating, by a flip-flop in the controller, the control signal at a first logic level from a first time to a second time, during which the input voltage is smaller than a reference voltage in magnitude;

generating, by the flip-flop in the controller, the control signal at a second logic level from the second time to a third time, during which the input voltage is larger than the reference voltage in magnitude;

generating, by the flip-flop in the controller, the control signal at the first logic level from the third time to a fourth time, during which the input voltage is smaller than the reference voltage in magnitude; and

directly outputting, b the flip-flop in the controller, the control signal;

wherein the first logic level and the second logic level are different.

11. The system of claim 7 wherein:

the controller further includes a comparator;

the comparator is configured to generate a comparison signal based on the sensing voltage; and

the flip-flop is further configured to receive the comparison signal and generate the control signal based at least in part on the comparison signal.