A light emitting diode driving circuit for driving an LED module formed by a plurality of light emitting diodes connected in parallel or in series, the light emitting diode driving circuit comprising:
- a bridge rectifier receiving an AC power input for rectifying the AC power and outputting pulse DC voltage;
- an inductor L1 having one end electrically coupled to the bridge rectifier for receiving the pulse DC voltage and having another end forwardly-biased and electrically coupling to one end of a LED module;
- a power switch having a first end, a second end and a controlled end for determining conduction or non-conduction of the first end and the second end;
- the first end being electrically coupled to the another end of the inductor;
- a first amplifier circuit electrically coupled to the second end of the power switch;
- the first amplifier circuit converting and amplifying a first current flowing through the power switch to a first voltage with a first amplification factor;
- a second amplifier circuit forwardly-biased and electrically coupled to another end of the LED module;
- and the second amplifier circuit converting and amplifying a second circuit flowing through the LED module to a second voltage with a second amplification factor;
- a switch driving circuit electrically coupled to the controlled end of the power switch for controlling the conduction and non-conduction of the power switch;
- when the power switch is conducted, the first current flowing through the inductor and then to the power switch so that the inductor stores energy therein and the first amplifier circuit outputs the first voltage;
- when the power switch is not conducted, the inductor releases energy to cause the second current flowing through the LED module and the second amplifier circuit outputs the second voltage;
- a D type flip-flop which is enabled by a trigger signal to the input end of a clock input end thereof;
- and a Q end thereof being electrically coupled to the switch driving circuit for controlling the conduction and non-conduction of the power switch through the switch driving circuit;
- and
- a comparator circuit receiving the first voltage and the second voltage;
- and comparing the first voltage with the reference voltage to determine whether the first voltage is smaller than the reference voltage;
- if yes, it outputting a logic 1 to the D type flip-flop so as to conduct the power switch through the switch driving circuit;
- otherwise, the comparator circuit outputting a logic 0 to the D type flip-flop so as not to conduct the power switch through the switch driving circuit;
- and the comparator circuit comparing the second voltage with the reference voltage;
- when the comparator circuit determines that the second voltage is greater than the reference voltage, it outputs a logic 0 to the D type flip-flop to cause the power switch not to conduct continuously through the switch driving circuit;
- otherwise, the comparator circuit outputting a logic 1 to the D type flip-flop so as to control the power switch to conduct through the switch driving circuit;
- and the comparator circuit comparing the first voltage and the reference voltage again.