Method and device for obtaining conduction angle, method and device for driving LED

1. A method for obtaining a conduction angle of a trailing edge dimmer, the method comprising:

determining a time point t 0 when the trailing edge dimmer starts to be conductive;

determining an earliest time point t 1 when a deviation from an ideal waveform appears; and

determining the conduction angle t 1 -t 0 of the trailing edge dimmer based on the earliest time point t 1 when the deviation from the ideal waveform appears and the time point t 0 when the trailing edge dimmer starts to be conductive.

2. The method of claim 1 ,

wherein the determining an earliest time point when a deviation from an ideal waveform appears comprises:

performing sampling on an output voltage of the trailing edge dimmer, comparing the sampled values with an ideal waveform, and

determining the earliest time point t 1 when the deviation from the ideal waveform appears based on the difference between the output voltage and the ideal waveform.

3. The method of claim 1 ,

wherein in the determining the conduction angle of the trailing edge dimmer, an average value of the conduction angles obtained in a plurality of cycles is calculated, and the average value is taken as an obtained conduction angle.

4. An LED driving method, comprising:

determining a type of a dimmer;

obtaining a conduction angle of a leading edge dimmer, when it is determined that the dimmer connected is the leading edge dimmer;

obtaining a conduction angle of a trailing edge dimmer with a method for obtaining a conduction angle of a trailing edge dimmer, when it is determined that the dimmer connected is the trailing edge dimmer, the method comprising:

determining a time point t 0 when the trailing edge dimmer starts to be conductive;

determining an earliest time point t 1 when a deviation from an ideal waveform appears; and

determining the conduction angle t 1 -t 0 of the trailing edge dimmer based on the earliest time point t 1 when the deviation from the ideal waveform appears and the time point t 0 when the trailing edge dimmer starts to be conductive; and

generating a dimming signal according to the obtained conduction angle of the dimmer.

5. The LED driving method of claim 4 , further comprising:

an anti-jittering control process after the conduction angle of the dimmer is obtained, wherein in the anti-jittering control process, a change in the conduction angle of the dimmer is detected, and only when the change in the conduction angle of the dimmer is larger than a certain threshold value, the dimming signal is generated according to the changed conduction angle of the dimmer.

6. The LED driving method of claim 4 , further comprising:

detecting whether the dimmer is connected, before the determining the type of the dimmer.

7. A conduction angle obtaining device for a trailing edge dimmer, the device comprising:

a conducting time point determiner, which is configured to determine a time point t 0 when the trailing edge dimmer starts to be conductive;

a phase cutting point determiner, which is configured to determine an earliest time point t 1 when a deviation from an ideal waveform appears; and

a conduction angle determiner, which is configured to determine the conduction angle t 1 -t 0 of the trailing edge dimmer based on the earliest time point t 1 when the deviation from the ideal waveform appears and the time point t 0 when the trailing edge dimmer starts to be conductive.

8. The conduction angle obtaining device for a trailing edge dimmer of claim 7 , wherein the phase cutting point determiner further comprises a sampling device and a comparing device, wherein:

the sampling device is configured to perform sampling on an output voltage of the trailing edge dimmer to obtain sampled values, and the comparing device is configured to compare the sampled values with an ideal waveform, and determine the earliest time point t 1 when the deviation from the ideal waveform appears based on the difference between the output voltage and the ideal waveform.

9. The conduction angle obtaining device for a trailing edge dimmer of claim 7 , wherein the conduction angle determiner further comprises an averaging device, which is configured to calculate an average value of the conduction angles obtained in a plurality of cycles, and take the average value as an obtained conduction angle.

10. An LED driving device, comprising:

a dimmer type determiner, which is configured to determine a type of a dimmer;

a conduction angle obtaining device for a leading edge dimmer, which is configured to obtain a conduction angle of a leading edge dimmer, when it is determined that the dimmer connected is the leading edge dimmer;

a conduction angle obtaining device for a trailing edge dimmer, which is configured to obtain a conduction angle of a trailing edge dimmer, when it is determined that the dimmer connected is the trailing edge dimmer, the conduction angle obtaining device comprising:

a conducting time point determiner, which is configured to determine a time point t 0 when the trailing edge dimmer starts to be conductive;

a phase cutting point determiner, which is configured to determine an earliest time point t 1 when a deviation from an ideal waveform appears;

a conduction angle determiner, which is configured to determine the conduction angle t 1 -t 0 of the trailing edge dimmer based on the earliest time point t 1 when the deviation from the ideal waveform appears and the time point t 0 when the trailing edge dimmer starts to be conductive; and

a dimming circuit, which is configured to generate a dimming signal according to the obtained conduction angle of the dimmer.

11. The LED driving device of claim 10 , further comprising:

an anti-jittering controller after the conduction angle obtaining device for the leading edge dimmer and the conduction angle obtaining device for the trailing edge dimmer and before the dimming circuit, wherein the anti-jittering controller is configured to detect a change in the conduction angle of the dimmer, and only when the change in the conduction angle of the dimmer is larger than a certain threshold value, the dimming signal is generated according to the changed conduction angle of the dimmer.

12. The LED driving device of claim 10 , further comprising:

a dimmer detector before the dimmer type determiner, which is configured to detect whether the dimmer is connected.