Fairchild FAN6754B65W (19V/3.42A) Notebook Power Solution

Fairchild's FAN6754B is a highly integrated green-mode PWM controller that can enhance the performance of flyback converters and minimize standby power consumption. High voltage start-up, low operating current 1.5mA, fixed PWM frequency 65kHz, frequency hopping to reduce EMI, peak current mode control, mainly used in LCD monitors, LCD TVs and notebook computers. This article introduces the main features of FAN6754B, functional block diagram, typical application circuit diagram and the main indicators, circuit diagram, bill of materials and PCB layout diagram of 65W (19V / 3.42A) flyback converter.

FAN6754B: Highly Integrated Green- Mode PWM Controller

The highly integrated FAN6754B PWM controller provides several features to enhance the performance of flyback converters. To minimize standby power consumption, a proprietary green-mode function provides off-time modulation to continuously decrease the switching frequency under light-load conditions.

Under zero-load and very light-load conditions, FAN6754B saves PWM pulses by entering deep burst mode. This burst mode function enables the power supply to meet international power conservation requirements.

FAN6754B integrates a frequency-hopping function internally to reduce EMI emission of a power supply with minimum line filters. Built-in synchronized slope compensation is accomplished by proprietary HV monitor to adjust VLimit for constant output power limit over universal AC input range. The gate output is clamped at 13V to protect the external MOSFET from over-voltage damage.

Other protection functions include AC input brownout protection with hysteresis, and VDD over-voltage protection. For over-temperature protection, an external NTC thermistor can be applied to sense the external switcher's temperature. When VDD OVP or OTP are activated, an internal latch circuit is used to latch-off the controller. The latch mode is reset when the VDD supply is removed.

FAN6754B is available in an 8-pin SOP package.

FAN6754B main features:

 High-Voltage Startup

 AC Input Brownout Protection with Hysteresis

 Monitor HV to Adjust VLimit

 Low Operating Current: 1.5m

A▪ Linearly Decreasing PWM Frequency to 22KHz

 Frequency Hopping to Reduce EMI Emission

 Fixed PWM Frequency: 65KHz

 Peak-Current-Mode Control

 Cycle-by-Cycle Current Limiting

 Leading-Edge Blanking (LEB)

 Internal Open-Loop Protection

 GATE Output Maximum Voltage Clamp: 13V

 VDD Under-Voltage Lockout (UVLO)

 VDD Over-Voltage Protection (OVP)

 Programmable Over-Temperature Protection (OTP)

 Internal Latch Circuit (OVP, OTP)

 Open-Loop Protection (OLP); Restart for MR, Latch for ML

 Built-in 8ms Soft-Start Function

FAN6754B Application:

LCD Monitor

LCD TV

Notebook PC

Figure 1. FAN6754B functional block diagram

Figure 2. FAN6754B typical application circuit diagram

Low cost green mode PWM controller flyback converter 65W (19V / 3.42A) for laptop adapters This document describes a 65W power supply using FAN6754AMR and FAN6204MY synchronous rectification IC. This power supply is targeted towards power adapters and open- frame consumer products.

With the internal high-voltage startup circuitry, the power loss due to bleeding resistors is eliminated. To further reduce power consumption, FAN6754AMR is manufactured using the BiCMOS process. This allows an operating current of only 1.5mA and low startup current of 30μA. Built-in synchronized slope compensation ensures the stability of peakcurrent-mode control. In addition, FAN6204MY improves conduction losses in heavy load, and the SR controller stops all SR switching operation to reduce the operating current in light load.

Main indicators of flyback converter:


Figure 3. 65W flyback converter appearance Figure

4. 65W flyback converter telegram registration route Figure
65W flyback converter bill of materials (BOM):



Figure 5. 65W flyback converter PCB layout (Top)

Figure 6. 65W Flyback Converter PCB Layout (Layer)
For more information, please see:
http://www.fairchildsemi.com/products/evaluationboards/FEBFAN6754AMR_CP450v1.pdf?user-guide=