AC-DC and LED Lighting

Every electrical product need the DC voltage power input converted from AC voltage delivered from power company, some of them were designed as a power adapter provided AC-DC power conversion, some of them installed as an open frame power module which was embedded inside products with only AC power supplied externally.

There are 2 common-used AC-DC technologies in the market: The one is single-stage, which adds switching power circuit right after AC bridge rectifier to provide constant current, it brings the higher power factor with less enough components used to reduce the cost. However, it also brings the higher ripple noises as another fruits; The other one is two-stage, after the first switching power circuit to provide stable DC voltage right after bridge rectifier, the second switching power circuit is added after to provide constant current. More complexity circuits bring the lowest ripple and higher power factor than the single-stage.

Power Factor ( PF ), is a specific physical quantity, is defined as the ratio of the real power flowing to the load to the apparent power in the circuit, it reflects the percentage of the generated power effectively be used in the power system, to evaluate the reasonable quantities of power consumed. Equipments rely on the Power Factor Correction (PFC) to improve the PF, to minimize the apparent power and the sinking current to increase the efficiency of entire power system.