最新版功率因数校正（PFC）手册（中）.pdf

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85

CHAPTER 7

Bridgeless PFC

Introduction

The need for higher efficiencies from the PFC stage has led the circuit designers to look closely at all sections of the circuit

and develop possible lower loss alternatives. One section that contributes significantly to the losses is the input bridge rectifier.

As a result, the alternatives to eliminate the diode bridge or convert it into a dual-use circuit have been explored for many years.

2

4

Figure 7−1 portrays the diode bridge that is usually inserted between the EMI filter and the PFC stage. This bridge rectifies

♦

For one line half-wave, D1 and D4 conduct (red arrows of Figure 7−1)

♦

I

bridge

T

line

T

line

22

@ I

in(rms)

(eq. 2)

Where:

♦

P

♦

♦

line

@ P