The Power Factor refers to the relationship between the effective Power and the total Power consumption (apparent Power), that is, the effective Power divided by the total Power consumption (apparent Power) ratio. Basically, the power factor can measure the extent to which the power is effectively used. When the power factor value is greater, the power utilization rate is higher on behalf of it. Power factor is used to measure the power efficiency of electrical equipment parameters, low power factor represents low power efficiency. In order to improve the power factor of electrical equipment technology is called power factor correction.
Computer switching power supply is a capacitive input circuit, the phase difference between the current and voltage will cause the loss of switched power, then the need for PFC circuit to improve the power factor. At present, there are two kinds of PFC, one is passive PFC (also known as passive PFC) and active PFC (also known as active PFC).
02 Passive PFC
Passive PFC is generally divided into "inductance compensation" and "Valley Fill Circuit".
"Inductance compensation type" is to reduce the phase difference between the fundamental current and the voltage of the AC input to improve the power factor, "inductance compensation type" includes silent type and non-silent type. "Inductance compensation type" power factor can only reach 0.7 ~ 0.8, it is generally near the high voltage filter capacitor.
"Valley circuit type" belongs to a new type of passive power factor correction circuit, its characteristic is to use the valley behind the rectifier bridge circuit to greatly increase the conduction Angle rectifier tube, by filling in pinggu, make it become a close to the sine wave input current from the spike pulse waveforms, to increase the power factor to around 0.9, significantly reduce the total harmonic distortion. Compared with the traditional inductive passive power factor correction circuit, it has the advantages of simple circuit, obvious power factor compensation effect, and it does not need to use large inductors in the input circuit.
03 Active PFC
While the active PFC is composed of inductors and capacitors and electronic components. It is small in size and adjusts the current waveform through a special IC to compensate the phase difference between current and voltage. Active PFC can achieve a high power factor -- typically more than 98% -- but they are also relatively expensive. In addition, active PFC can also be used as auxiliary power supply, so in the use of active PFC circuit, often do not need standby transformer, and active PFC output DC voltage ripple is very small, this power supply does not need to use a large capacity of the filter capacitor.
More than one thousands of kinds the switching power supply,each PFC power supply is the active PFC SMPS. More details please check the below product link:
