Analysis of the shortcomings and problems of SCR dimming

There are still a series of problems when using silicon controlled dimming.

(1) the dimming process, with the internal conduction angle changes, sine wave input voltage was damaged by SCR, thereby reducing the power factor value (PF), PF is usually less than 0.5, and in the light, with the conduction angle is small, the power factor value is more and more low brightness (1/4 only 0.25).

(2) as above, the input voltage sine wave is destroyed, and the sine wave increases the harmonic coefficient.

(3) the input of non sinusoidal voltage waveform in LED drive circuit will produce serious interference signal (EMI).

(4) it is very easy to cause the instability in the low light load because of the lack of current. The solution is to add a leakage resistance. Typically, the leakage resistance consumes at least 1-2 watts of power, which reduces the efficiency of the constant current source circuit.

(5) when using the silicon controlled dimming circuit to adjust the light of the incandescent lamp, when the input LC filter and the silicon controlled oscillation, the human eye can not see the oscillation due to the thermal inertia of the incandescent lamp. However, when the silicon controlled dimming circuit is used in conjunction with the LED drive circuit, audio noise and flicker can occur, which is often unacceptable.