Fairchild AN-6026 Specifications Manual
Summary
Designed for professionals building high-efficiency power supplies, this manual details the implementation of an Active Power Factor Correction (PFC) circuit using FAN7529 boost controllers. The guide provides comprehensive technical knowledge on both current and voltage modes of PFC operation. It meticulously covers the underlying circuitry, including detailed descriptions of critical internal blocks like the Zero Current Detector and Error Amplifier. Use this resource to understand how to design robust, optimal power factor conversion systems for demanding electrical applications.
Page 1 Text Content
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Application Note AN-6026 Design of Power Factor Correction Circuit Using FAN7529
1. Introduction FAN7527B; however, the sensing network can cause addi- tional power loss. In the voltage mode, the switch turn-on is
The FAN7529 is an active power factor correction (PFC)
the same as that of the current mode, but the switch turn-off
controller for the boost PFC application that operates in the
is determined by an internal ramp signal. The ramp signal is
critical conduction mode (CRM). The critical conduction
compared with an error amplifier output and the switch turn-
mode boost power factor converter operates at the boundary
on time is controlled to be constant, as shown in Figure 1. If
of continuous conduction mode and discontinuous conduc-
the turn-on time is constant, the peak inductor current is pro-
tion mode. The CRM PFC controllers are of two kinds: the
portional to the rectified AC line voltage, as shown in Figure
current-mode CRM PFC controller and the voltage-mode
2. In this way, the input current waveform follows the wave-
CRM PFC controller. For the current mode, a boost switch is
form of the input voltage, thereby obtaining a good power
turned on when the inductor current reaches zero and turned
factor. The FAN7529 is a voltage-mode CRM PFC control-
off when the inductor current meets the desired current refer-
ler. Because the voltage-mode CRM PFC controller does not
ence. In this case, the rectified AC line voltage should be
need the rectified AC line voltage information, it can save
sensed to generate the current reference, as in the
the power loss of the sensing network.
AC IN
Turn- ur On
Turn- Off
RSENSE
Feedback
Disable
Error Amp
Figure 1. Voltage Mode CRM Boost PFC Circuit
Diode
Conduction
Inductor Current Inductor
Current
Average Input
MOSFET
Current
Conduction
Gating Signal Constant On- time & Variable Off- time
Figure 2. CRM Boost PFC Inductor Current Waveform
© 2006 Fairchild Semiconductor Corporation www.fairchildsemi.com Rev. 1.0.4 • 4/25/08
Page Summary Contents For Fairchild AN-6026 Specifications Manual
Manual Details
| Brand | Fairchild |
|---|---|
| Pages | 23 |
| File Size | 346.51 KB |
| Published | July 06, 2026 |
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Frequently Asked Questions
How does the Zero Current Detector (ZCD) function?
The ZCD generates the MOSFET turn-on signal when the boost inductor current reaches zero, utilizing an auxiliary winding for detection.
What are the thresholds for Over-Voltage Protection (OVP)?
OVP shuts down the output drive block if the input voltage (V_IN) is higher than 2.675V, allowing a 0.175V hysteresis.
How can I externally disable the IC?
An external, small-signal 6.5V to 1.5V MOSFET can be used to manually disable the IC and reduce power consumption.
Can the FAN7529 be used in life support systems?
No; Fairchild’s products are not authorized for use as critical components in life support devices or systems without express written approval.