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Brief introduction of PFC regulator switching power supply
- May 16, 2017 -

Switching power supply is a very important component in PFC switching power supply.

In PFC, the switching power supply function and the common switching power supply are not great difference, but the power supply is different. Common switching power supply requires 220V rectifier power supply, while PFC regulator switching power supply is powered by B+PFC. This paper will introduce a simple introduction to PFC power.

After rectification does not add a filter capacitor, the pulse of the non-filtered voltage half-week as the source of power supply chopper, as a result of a series of chopper to do "switch" operating pulsating positive voltage is "chopped" into the current waveform, its waveform features:

1, the current waveform is intermittent, its envelope and voltage waveform is the same, and envelope and voltage waveform phase of the same phase.

2, because of the role of Chopper, the half-wave pulsating dc power into high frequency (by the chopper frequency decision, about 100KHz) "AC" Electricity, the high-frequency "AC" power to once again after rectification to be the rear-level PWM switching power supply used.

3, from the total external power supply system to achieve the AC voltage and AC current and the same phase and voltage waveform and current waveform are in line with the sine wave shape, not only solved the power factor compensation problem, also solves electromagnetic compatibility (EMC) and electromagnetic interference (EMI) problem.

The high frequency "AC" Electricity is powered by a rectifier diode rectifier and a PWM switching power supply to a DC voltage (power supply) backward level. The DC voltage is referred to in some data as: B+PFC (TPW-4211 is so), in the chopper output B+PFC voltage is generally higher than the original 220 AC rectification filter after the +300V, the reason is the selection of high voltage, the inductance of the line diameter small, the line pressure drop, the filter capacitance small capacity, and the filter effect is good, the rear-level PWM switching pipe requirements of many advantages.

Current PFC switching power supply part, switching effect of the chopper (K) There are two ways to work:

1, continuous conduction mode (CCM): Switching pipe working frequency must, and the duty ratio (coefficient) of the conductivity varies with the magnitude of the chopper voltage.

2, discontinuous conduction mode (DCM): chopping switch tube working frequency varies with the size of the chopper voltage ("open" and "close" time are equal in each switching cycle).

Power factor correction switching power supply in PFC switching part and the excitation part of the PWM switching power supply are accomplished by a piece of IC, a piece of IC can complete the design.

The above is a simple introduction to the PFC of switching power supply. It can be seen that this switching power supply has the characteristics of small inductance path, small line pressure drop, small filter capacitance capacity. Compared with the traditional switching power supply has obvious advantages. For PFC switching power supply still not very understanding of friends can spend a few Zhong Lai reading this article, I believe there will be unexpected harvest.