The LED consists of step-down capacitor
The step-down capacitor is least expensive for led of design scheme.
In practice , resistance – capacitor circuit is also commonly used. the step-down capacitor similar to constant power supply, constant value associated with capacitance capacity. there is another a parameters capacitive reactance. we know that capacitive reactance associated with AC input voltage base on formula as follows:
1÷（2π×f×C）
by the proper choice of the controller parameters( capacitance capacity), the current stability of led is guaranteed.