In PFC switching power supply, switching power supply is a very important part.A switching power supply of PFC function and the difference between ordinary switch regulated power supply is not big, just differ in power supply.Ordinary rectifier switch stabilized voltage supply need 220 v power supply, and PFC voltage switch power is supplied by B + PFC.This paper will focus on PFC power supply were introduced simply.
Without filtering without filter capacitor after rectification, the pulsation of the positive half cycle as a chopper voltage of power supply source, due to the chopper "switch" of a series of job pulsation of positive voltage to be "cut" into current waveform, the waveform features are:
1, the current waveform is intermittent, the envelope is the same as the voltage waveform, and the envelope and phase voltage waveform in phase.
2, due to the role of chopper, half wave pulsating direct current into high frequency (100 KHZ) is determined by chopping frequency, "communication", the high frequency of "communication" electricity again after rectification can be level PWM switch regulated power supply is used.
3, from the outside of the electricity system in general to the ac voltage and ac current in phase and voltage waveform and current waveform are accord with sine waveform, both can solve the problem of power factor compensation, also solve the electromagnetic compatibility (EMC) and electromagnetic interference (EMI) problem.
The high frequency electric after a rectifier diode rectifier "exchange" and a filter into a dc voltage (power) backward level of the PWM switch power supply.The dc voltage on some data call it: B + PFC (TPW - 4211), the chopper output of B + PFC voltage is generally higher than the original 220 after ac rectifier filter + 300 v, the reason is that selects high voltage, the inductance of the wire diameter is small, small line drop, filter capacitance, and filtering effect is good, the low level PWM switch tube requirements after many benefits.
The PFC part of switch power supply, switching effect of chopping tube (K) has two work modes:
Continuous conduction mode (CCM) : 1, the work frequency of the switch tube must be, and the conduction of the duty ratio (coefficient) changes over the chopping voltage amplitude.
2, discontinuous conduction mode (DCM) : chopping the work frequency of the switch tube change with was the size of the chopper voltage (each switching cycle is equal to "open" and "off" time).
Power factor correction PFC of switch power supply switching power supply part and PWM switching power supply part of the incentive part are completed by an integrated circuit, an IC can finish the design.
The above is a switching power supply PFC simple introduction.As you can see, this kind of switch regulated power supply with small inductance path, line pressure drop and the characteristics of the filter capacitance is small.Compared with the traditional switch regulated power supply has more obvious advantages.For PFC switch regulated power supply is still not too understand friends can take a few minutes to read this article, believe that will have unexpected harvest.