Fairchild AN4107 User's Guide
Summary
Essential technical documentation for implementing high-efficiency power factor correction (PFC) using the FAN7527 active control controller within boost converter designs. This manual thoroughly explains the PFC mechanism, detailing how a sophisticated internal multiplier forces the input current to perfectly track sinusoidal AC line voltage. It provides engineers with comprehensive insights into the chip's operation, including detailed block diagrams and critical over-voltage protection modes (Soft OVP, Dynamic/Static OVP). Ideal for power electronics designers building systems that require superior power quality and compliance with modern electrical standards.
Page 1 Text Content
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Application Note AN4107 Design of Power Factor Correction Using FAN7527
1. Introduction power factor is obtained.
The FAN7527 is an active power factor correction(PFC) 1-1. Internal Block Diagram controller for boost PFC application which operates in the It contains following blocks. critical conduction mode. It turns on MOSFET when the Error amplifier (E/A) inductor current reaches zero and turns off MOSFET when Zero current detection (Idet) the inductor current meets the desired input current reference Switch current sensing (CS) voltage as shown in Fig. 1. In this way, the input current Input voltage sensing (MULT) waveform follows that of the input voltage, therefore a good Switch drive (OUT)
Inductor Peak Current
Inductor Current
Inductor Average Current
Gating Signal
Figure 1. Inductor Current Waveform
8Vcc 2.5V Ref
UVLO Internal Bias
12V 9V OUTDrive
Output
Timer R
2V 1.5V Zero Current Detector
Static OVP
Current Sense Comparator
Veao(L)=2.25V
Vmo 0.25V
Vm1 +−
0 ~ 3.8V Vm2 Vref~Vref+2.5V INV1
Vea(-)
Multiplier OVP
Isovp=30u A
Current Error Amp
Vmo K Idovp=40u A
Detector
−⋅ Vref2Vm1Vm
GND EA_OUT
Figure 2. Block diagram of the FAN7527
Rev. 1.0.2
©2001 Fairchild Semiconductor Corporation Rev. A, May 2000
Page Summary Contents For Fairchild AN4107 User's Guide
Manual Details
| Brand | Fairchild |
|---|---|
| Pages | 14 |
| File Size | 486.37 KB |
| Published | June 05, 2026 |
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Frequently Asked Questions
What is the primary purpose of the FAN7527 controller?
It is an active power factor correction (PFC) controller designed for boost PFC applications.
How does the device protect against over voltage conditions?
If the monitored current exceeds 40uA, the OVP protection triggers and switches off the transistor until the current drops below approximately 10uA.
What mechanism forces the input current to be sinusoidal?
The multiplier output controls the comparator threshold voltage, allowing the peak inductor current to follow the AC line and forcing the average input current to be sinusoidal.