Silicon-controlled incandescent lamp principle.
The principle of silicon controlled light: The potentiometer RV2 adjusts the phase Angle of the thyristor (TRIAC). When VC3 exceeds DIAC's breakdown voltage, the thyristor will guide. When the SCR (Iholding) to their current (figure 2), when the thyristor turn-off, and must wait until the C3 again next half cycle recharge to conduction. Light bulb filament and dimming signal of the phase Angle of voltage and current is closely related to the change of the phase Angle range between 0 degrees (close to 0 degrees to 180 degrees (depending on the dimmer).
P = I2R I = U/R, P = U2 / R half thyristor conduction, voltage amplitude does not change, so the instantaneous power is constant, on the timeline, only half of the whole conduction time in power, the power of reason 90 degrees two-way thyristor conduction is half full conduction, rather than a quarter.
One way to control silicon is only positive half waveguide, which is equivalent to diode, and the actual power consumption of incandescent lamp is 1/4. It's 1/8 when the Angle is 90 degrees. Both sides of the two sides are able to guide the positive and negative half wave, and the actual end of the incandescent lamp is full voltage, and the power consumption is one. The positive and negative half waveguide angles are 1/4 for all 90 degrees.
