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τροφοδοτικό- PFC(active-passive)


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Active PFC

The preferable type of PFC is Active Power Factor Correction (Active PFC) since it provides more efficient power frequency. Because Active PFC uses a circuit to correct power factor, Active PFC is able to generate a theoretical power factor of over 95%. Active Power Factor Correction also markedly diminishes total harmonics, automatically corrects for AC input voltage, and is capable of a full range of input voltage. Since Active PFC is the more complex method of Power Factor Correction, it is more expensive to produce an Active PFC power supply.

Passive PFC

The most common type of PFC is Passive Power Factor Correction (Passive PFC). Passive PFC uses a capacitive filter at the AC input to correct poor power factor. Passive PFC may be affected when environmental vibration occurs. Passive PFC requires that the AC input voltage be set manually. Passive PFC also does not use the full energy potential of the AC line.

http://www.endpcnoise.com/cgi-bin/e/pfc.html

What's Active / Passive PFC ?

Passive PFC, using inductor, capacitor circuitry to reduce harmonic current, because power source frequency is 50 Hz or 60Hz low frequency, it needs large inductor and capacitor. Moreover, the power factor improvement is only around 75%~80%. Active PFC , using active components(control circuit and power sine conductor On/Off switch), the fundamental working theory is to adjust input current wave-form to simulate input voltage waveform. With this method, we can achieve power factor near or equal to the 100% power factor target.

Active type power factor correction using active component (control circuit and power sine conductor ON/OFF switch). Its fundamental working theory is to adjust input current waveform to looks like input voltage waveform, this can reach the point where power factor of 1 goal. Also, the input voltage range can be 90Vdc to 264V without additional switch for choosing the voltage range. To have a universal voltage model, this power factor regulator is a very important additional value. Otherwise, the cost increased more.

Why Active PFC better than Passive PFC?

1. Active PFC improves Power Factor to more than 95% , which surpasses the 75%PF with Passive PFC solution. Thus Active PFC is more energy saving than Passive PFC.

2. Lighter equipment will be the trend for all 3C products and PSU as well. Passive PFC PSU adopts cumbersome components which make it much heavier than an Active PFC PSU.

Benefits of Active PFC:

* Large buffer to EN harmonics requirement to ensure compliance.

* Opportunity for future cost decreases as ICs requirement volumes increase.

* Low risk in terms of material shortage.

* A more "professional" solution than Passive one.

* Full range feature comes with less cost.

* Perfect power factor approach 1 for power utilization. (Environment friendly)

* Better competition when power goes up was the trend of CPU's requirement.

Negatives of Passive PFC:

* Mass production of inductor must be accurate due to small buffer to EN harmonics limit.

* Heavy weight that might create problems during transport. (Vibration & shock)

* Possible shortage of ferrite material.

* Vibration noise if structure is not fixed correctly.

* Poor competition (cost and performance) when power up to 300W or more.

http://www.seasonicusa.com/support.faq.php

Passive PFC, using inductor, capacitor circuitry to reduce harmonic current, because power source frequency is 50 Hz or 60Hz low frequency, it needs large inductor and capacitor. Moreover, the power factor improvement is only around 75%~80%. Active PFC, using active components (control circuit and power sine conductor On/Off switch), the fundamental working theory is to adjust input current waveform to simulate input voltage waveform. With this method, we can achieve power factor near or equal to the 100% power factor target.

Active type power factor correction using active component (control circuit and power sine conductor ON/OFF switch). Its fundamental working theory is to adjust input current waveform to looks like input voltage waveform, this can reach the point where power factor of 1 goal. Also, the input voltage range can be 90Vdc to 264V without additional switch for choosing the voltage range. To have a universal voltage model, this power factor regulator is a very important additional value. Otherwise, the cost increased more.

http://twe.enlightcorp.com/support/faq/index1.php?serial=12

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