Fairchild’s FL7730 is a dimmable single-stage PFC offline LED driver, compatible with traditional TRIAC control, compatible with non-dimmable lamp designs, does not require large input capacitors and feedback circuits, has open-circuit, short-circuit protection, and cycle-by-cycle limit. Current, starting current 20uA, working current 5mA, application voltage is 80VAC ~ 308VAC, mainly used for lighting. This article introduces the main characteristics of FL7730, block diagram and main performance indicators of 8.4W LED lighting, lamp shape, PCB circuit diagram, bill of materials and PCB Component layout diagram.

This highly integrated PWM controller, FL7730MY, provides several features to enhance the performance of single-stage flyback converters. The proprietary topology, TRUECURRENT™, enables the simplified circuit design for LED lighting applications.

The FL7730 is an active Power Factor Correction (PFC) controller using single-stage flyback topology. Dimming control with no flicker is implemented by an analog sensing method. Primary-side regulation and single-stage topology reduce external components such as input bulk capacitor and feedback circuitry and minimize cost. To improve good power factor and Total Harmonic Distortion (THD), constant on-time control is utilized with internal error amplifier and a low-bandwidth compensator. Precise constant-current control regulates accurate output current, independent of input voltage and output voltage. Operating frequency is proportionally changed by output voltage to guarantee DCM operation with higher efficiency. FL7730 provides protections such as open-LED,short-LED, and over-temperature protection.

TRIAC dimming is smoothly managed by dimming brightness control without flicker. By using single-stage topology with primary-side regulation, an LED lighting board can be implemented with few external components and minimized cost. It does not require an input bulk capacitor or feedback circuitry . To implement good power factor and low total harmonic distortion, constant on-time control is utilized with an external capacitor connected to the COMI pin.

Precise constant-current control regulates accurate output current versus changes in input voltage and output voltage. The operating frequency is proportionally changed by the output voltage to guarantee Discontinuous Conduction Mode (DCM) operation with higher efficiency and simpler design. The FL7730MY provides protections such as open-LED, short-LED, and over-temperature protections. Current-limit level is automatically reduced to minimize output current and protect external components in a short-LED condition.

The FL7730MY controller is available in an 8-pin SOP package.

FL7730 main features:

￭ Compatible with Traditional TRIAC Control (No need to change existing lamp infrastructure: wall switch & wire)

￭ Compatible with Non-Dimming Lamp Designs

￭ Cost-Effective Solution without Input Bulk Capacitor and Feedback Circuitry

￭ Power Factor Correction (PFC)

￭ Accurate Constant-Current (CC) Control, Independent Online Voltage, Output Voltage, Magnetizing Inductance Variation

￭ Line Voltage Compensation for CC Control

￭ Linear Frequency Control for Better Efficiency and Simple Design

￭ Open-LED Protection

￭ Short-LED Protection

￭ Cycle-by-Cycle Current Limiting

￭ Over-Temperature Protection with Auto Restart

￭ Low Startup Current: 20µA

￭ Low Operating Current: 5mA

￭ SOP-8 Package Available

￭ Application Voltage Range: 80VAC ~ 308VAC

FL7730 application:
Lighting

Figure 1. FL7730 block diagram
Main performance indicators of LED lighting:


Figure 2.8.4W LED Light PCB Outline Drawing: Top View

Figure 3.8.4W LED Light PCB Outline Drawing: Bottom View

Figure 4.8.4W LED light outline drawing

Figure 5.8.4W LED light circuit diagram

Figure 6.8.4W LED lamp transformer circuit diagram

8.4W LED Lamp Bill of Materials (BOM):

Figure 7.8.4W LED Lamp PCB Component Layout: Top Layer

Figure 8.8.4W LED Lamp PCB Component Layout: Bottom Layer
For details, see:
http://www.fairchildsemi.com/an/AN/AN-FEB020H.pdf
and
http://www.fairchildsemi.com/support/referencedesign/docs/RD-L020-2.pdf