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Fairchild’s FAN9611/12 is a cross dual boundary conduction mode (BCM) power factor correction (PFC) controller, which can control two power chains connected in parallel with a phase shift of 180 degrees, and control the power from 300W to 800W. The switching frequency is between 16.5kHz and 525kHz, and the starting current is 80uA. It is mainly used in 100-1000W AC/DC power supply, large-screen LCD-TV, PDP-TV and RP-TV power supply, high-efficiency desktop computer and server power supply, network and communication power supply As well as solar micro-inverters. This article introduces the main features, block diagrams, typical application circuit diagrams of FAN9611/12, and the main features, circuit diagrams, bill of materials and PCB component layout diagrams and peak current limit circuit diagrams of the FAN9611 300W cross double BCM small-size PFC evaluation board. .

The FAN9611/12 family of interleaved dual Boundary-Conduction-Mode (BCM) Power-Factor-Correction (PFC) controllers operate two parallel-connected boost power trains 180° out of phase. Interleaving extends the maximum practical power level of the control technique from about 300W to greater than 800W. Unlike the continuous conduction mode (CCM) technique often used at higher power levels, BCM offers inherent zerocurrent switching of the boost diodes, which permits the use of less expensive diodes without sacrificing efficiency. Furthermore, the input and output filters can be smaller due to ripple current cancellation and effective doubling of the switching frequency.

The converters operate with variable frequency, which is a function of the load and the instantaneous input / output voltages. The switching frequency is limited between 16.5kHz and 525kHz. The Pulse Width Modulators (PWM) implement voltage-mode control with input voltage feedforward. When configured for PFC applications, the slow voltage regulation loop results in constant on-time operation within a line cycle. This PWM method, combined with the BCM operation of the boost converters, provides automatic power factor correction.

The controllers offers bias UVLO (10V / 7.5V for FAN9611 and 12.5V / 7.5V for FAN9612), input brownout, over-current, open-feedback, output overvoltage, and redundant latching over-voltage protections.

Furthermore, the converters’ output power is limited independently of the input RMS voltage. Synchronization between the power stages is maintained under all operating conditions.

Main features of FAN9611/12:

Sync-Lock™ Interleaving Technology for 180° Out-of-Phase Synchronization Under All Conditions

Automatic Phase Disable at Light Load

Dead-Phase Detect Protection

2.0A Sink, 1.0A Source, High-Current Gate Drivers

High Power Factor, Low Total Harmonic Distortion

Voltage-Mode Control with (VIN)2 Feedforward

Closed-Loop Soft-Start with User-Programmable Soft-Start Time for Reduced Overshoot

Minimum Restart Frequency to Avoid Audible Noise

Maximum Switching Frequency Clamp

Brownout Protection with Soft Recovery

Non-Latching OVP on FB Pin and Latching Second-Level Protection on OVP Pin

Open-Feedback Protection

Power-Limit and Current Protection for Each Phase

Low Startup Current of 80μA Typical

Works with DC and 50Hz to 400Hz AC Inputs

FAN9611/12 application:

100-1000W AC-DC Power Supplies

Large Screen LCD-TV, PDP-TV, RP-TV Power

High-Efficiency Desktop and Server Power Supplies

Networking and Telecom Power Supplies

Solar Micro Inverters

Figure 1. Block diagram of FAN9611/12

Figure 2. FAN9611/12 typical application circuit diagram

Figure 3. Cross-BCM PFC circuit diagram using FAN9611/12

FAN9611 300W cross dual BCM small size PFC evaluation board

The FAN9611 interleaved, dual Boundary-Conduction-Mode (BCM), Power-Factor- Correction (PFC) controllers operate two parallel-connected boost power trains 180º out of phase. Interleaving extends the maximum practical power level of the control technique from about 300W to greater than 800W. Unlike the Continuous Conduction Mode (CCM) technique often used at higher power levels, BCM offers inherent zerocurrent switching of the boost diodes (no reverse-recovery losses), which permits the use of less expensive diodes without sacrificing efficiency. Furthermore, the input and output filters can be smaller due to ripple current cancellation between the power trains and doubling of effective switching frequency.

The advanced line feed-forward with peak detection circuit minimizes the output voltage variation during line transients. To guarantee stable operation with less switching loss at light load, the maximum switching frequency is clamped at 525kHz. Synchronization is maintained under all operating conditions.

Protection functions include output over-voltage, over-current, open-feedback, undervoltage lockout, brownout, and redundant latching over-voltage protection. FAN9611 is available in a lead-free, 16-lead, Small-Outline Integrated-Circuit (SOIC ) package.

This FAN9611 evaluation board uses a four-layer Printed Circuit Board (PCB) designed for 300W (400V/0.75A) rated power. The maximum rated power is 350W and the Maximum On-Time (MOT) power limit is set to 360W. The FEBFAN9611_S01U300A is optimized to demonstrate all the FAN9611 efficiency and protection features in a lowprofile height form factor less than 18mm.

Main features of FAN9611 300W PFC evaluation board:

180° Out-of-Phase Synchronization

Automatic Phase Disable at Light Load

1.8A Sink, 1.0A Source, High-Current Gate Drivers

Transconductance (gM) Error Amplifier for Reduced Overshoot

Voltage-Mode Control with (VIN)2 Feed-Forward

Closed-Loop Soft-Start with Programmable Soft-Start Time for Reduced Overshoot

Minimum Restart Timer Frequency to Avoid Audible Noise

Maximum Switching Frequency Clamp

Brownout Protection with Soft Recovery

Non-Latching OVP on FB Pin and Second-Level Latching Protection on OVP Pin

Open-Feedback Protection

Over-Current and Power-Limit Protection for Each Phase

Low Startup Current: 80μA Typical

Works with DC input or 50Hz to 400Hz AC Input

Figure 4. Outline drawing of FAN9611 300W PFC evaluation board: top

Figure 5. Outline drawing of FAN9611 300W PFC evaluation board: bottom

FAN9611 300W PFC evaluation board electrical and mechanical specifications:

Figure 6. Circuit diagram of FAN9611 300W PFC evaluation board

FAN9611 300W PFC Evaluation Board Bill of Materials:

Figure 7. FAN9611 300W PFC evaluation board component layout diagram: top

Figure 8. FAN9611 300W PFC evaluation board component layout diagram: bottom

Figure 9. FAN9611 300W PFC evaluation board peak current limit circuit diagram

For details, see:

http://www.fairchildsemi.com/ds/FA/FAN9611.pdf

and

http://www.fairchildsemi.com/products/evaluationboards/FEBFAN9611_S01U300A.pdf?user-guide=

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