FLS3247N - Single-Stage PFC PSR Offline LED Driver | onsemi
MPN: FLS3247N β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.62 | $1.62 |
| 10 | $1.46 | $14.60 |
| 100 | $1.25 | $125.00 |
| 500 | $1.08 | $540.00 |
| 1,000 | $0.94 | $940.00 |
FLS3247N Overview
An offline LED driver IC is a power management IC that converts AC mains input into a regulated constant current for LED strings. In the power-management hierarchy, the FLS3247 sits within the AC-DC offline switcher family, specifically the flyback converter topology, and eliminates the need for a secondary-side feedback circuit by sensing output information from the primary-side auxiliary winding.
Key features include single-stage PFC operation with constant on-time control for high power factor and low THD, primary-side regulation that removes the optocoupler and secondary feedback components, an integrated power MOSFET that reduces BOM count, and built-in protection functions for robust offline operation. According to the onsemi FLS3217/FLS3247 datasheet, the single-stage topology requires no input bulk capacitor or feedback circuitry, minimizing cost and board area.
Technically, the device implements a quasi-resonant-style flyback controller with constant on-time modulation via an external capacitor on the COMI pin, achieving good power factor without a dedicated PFC stage. The integrated MOSFET handles the switching duty, and the controller provides cycle-by-cycle current limiting for fault resilience.
Typical applications include LED bulbs, T8/T5 LED tube lamps, LED ceiling and downlights, and other sub-20W-class offline luminaires where cost, power factor, and form factor dominate the design.
Design consideration: because PSR regulates from the auxiliary winding, tightly coupled transformer windings and careful magnetics design are essential to maintain output current accuracy over line and load.
This page synthesizes distributor data, drop-in alternative guidance, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for FLS3247N β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
FLS3217N
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
FLS3247N Maximum Ratings & Electrical Characteristics
| Function | Single-Stage PFC Primary-Side-Regulation Offline LED Driver with Integrated Power MOSFET |
| Topology | Flyback (AC-DC Offline Switcher) |
| Switching Frequency | 65 kHz |
| Control Scheme | Constant on-time, primary-side regulation |
| Outputs | 1 |
| Dimming Support | Yes |
| Package | DIP-7 |
| Mounting Type | Through Hole |
| Series | FLS3247 |
| RoHS Status | Compliant |
| Power Factor Correction | Single-stage PFC (no input bulk capacitor required) |
FLS3247N dip-7 Pin Configuration Guide
Pin configuration for FLS3247N (dip-7 package). This power device features gate, drain, and source terminals. For non-polarized packages, refer to the manufacturer datasheet for exact pin 1 orientation and footprint details. Common applications include power supply design, motor driving, and load switching.
No detailed pinout data available for FLS3247N.
Refer to the datasheet for full pin configuration.
Typical Applications
FLS3247N is suitable for 6 applications: LED Bulb Drivers, LED Tube Lights (T8/T5), LED Ceiling and Downlight Fixtures, Dimmable Offline LED Drivers, Low-Cost Consumer Lighting Power Supplies, Replacement / Service of Legacy LED Luminaires.
LED Bulb Drivers
The FLS3247N is purpose-built for retrofit LED bulb drivers in the low-power offline class, where bill-of-materials cost and small form factor dominate. Its single-stage PFC topology with constant on-time control delivers good power factor and low THD without a separate PFC stage or input bulk capacitor, and primary-side regulation removes the optocoupler and secondary feedback circuitry entirely. The integrated 65 kHz power MOSFET means the entire drive electronics fit on a circular PCB sized to the bulb base. Because PSR senses output from the auxiliary winding, tight transformer coupling is the main design consideration for output current accuracy.
Recommended
LED Tube Lights (T8/T5)
For T8 and T5 LED tube drivers, the FLS3247N provides the constant-current output needed for uniform LED string brightness across line variations. Its primary-side regulation maintains output current accuracy without secondary-side sensing, which is valuable in the narrow linear PCB format of tube luminaires where component height and count are constrained. The single-stage PFC meets the power factor expectations of commercial lighting installations without a dedicated correction stage, and the integrated MOSFET reduces the driver PCB to a minimal flyback design. Built-in protection features improve field reliability in fixtures with constrained thermal environments.
Recommended
LED Ceiling and Downlight Fixtures
Downlight and ceiling luminaire drivers benefit from the FLS3247N's high integration: controller, 65 kHz power MOSFET, single-stage PFC, and PSR feedback in one DIP-7 device. This reduces the driver module to a transformer, a handful of passives, and the IC, fitting the cylindrical driver cans typical of recessed fixtures. The absence of an input bulk capacitor shortens the input side and improves power factor, while dimming support enables compatibility with leading-edge dimmer installations common in residential and commercial ceilings. Thermal design should account for enclosed-fixture ambient temperatures when sizing the magnetics and copper pours.
Recommended
Dimmable Offline LED Drivers
The FLS3247N supports dimming in AC-DC offline flyback configurations, making it suitable for luminaires that must operate with wall-box dimmers. Because the constant on-time single-stage PFC control draws input current that follows the rectified line waveform, the driver presents a resistive-like load that cooperates reasonably with phase-cut dimming compared with capacitive-input designs. Primary-side regulation keeps the LED current regulated across the dimming range without a secondary feedback path, and the 65 kHz switching frequency keeps audible noise and magnetics size in a practical balance for consumer lighting products.
Recommended
Low-Cost Consumer Lighting Power Supplies
Cost-driven consumer lighting power supplies adopt the FLS3247N because it collapses the AC-DC constant-current conversion chain into one IC. According to the onsemi datasheet, the single-stage topology with primary-side regulation requires the fewest external components, no input bulk capacitor, and no feedback circuitry, directly attacking the dominant cost drivers in sub-20W-class drivers. The DIP-7 through-hole package also simplifies assembly for low-cost single-sided or minimal-layer PCBs. Designers should validate output current accuracy across production transformer tolerance since PSR depends on auxiliary-winding coupling.
Recommended
Replacement / Service of Legacy LED Luminaires
Because the FLS3247N is end-of-life, its most active use case today is servicing and remanufacturing legacy LED luminaires already designed around it. Technicians can source remaining authorized stock through DigiKey and Rochester Electronics listings. For designs needing the identical DIP-7 footprint with lower power, the FLS3217N drops in pin-to-pin with the same 65 kHz PSR controller. Where stock is exhausted and the power class demands the FLS3247N rating, a driver-board redesign using an active onsemi flyback controller is the long-term path; no cross-brand pin-compatible equivalent was identified.
Recommended
Recommended Products Summary
Engineering reference data for FLS3247N β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | FLS3217N |
|---|---|---|
| Package | DIP-7 | DIP-7 - same |
| Brand | onsemi (formerly Fairchild Semiconductor) | onsemi |
| Switching Frequency | 65 kHz | 65 kHz |
| Control Topology | Single-stage PFC, PSR flyback, constant on-time | Single-stage PFC, PSR flyback, constant on-time |
| Integrated Power MOSFET | Yes - higher power rating | Yes - lower power rating |
| Dimming Support | Yes | Yes |
| Optocoupler Required | No (primary-side regulation) | No (primary-side regulation) |
| Lifecycle Status | EOL (Rochester lifecycle stock) | EOL |
Key Differentiators
- Higher integrated MOSFET power rating within the family (vs FLS3217N)
- No optocoupler or input bulk capacitor required (vs Conventional secondary-regulated flyback drivers)
- Constant on-time single-stage PFC control (vs FLS3217N (same scheme) and two-stage PFC solutions)
Design Notes
The FLS3247N implements single-stage PFC via constant on-time control; the on-time is set by an external capacitor on the COMI pin. Size this capacitor per the onsemi datasheet equation for your target on-time, since it directly sets power factor, THD, and peak MOSFET current. Because there is no input bulk capacitor, the design must tolerate the full rectified sine envelope - verify the integrated MOSFET current rating at the lowest line voltage and full LED load, with margin for startup transient peaks.
Primary-side regulation infers output voltage and current from the auxiliary winding waveform during the flyback demagnetization interval. Transformer leakage inductance and winding interleaving therefore directly affect output current accuracy and line/load regulation. Specify a tightly coupled auxiliary winding, keep the leak-age-sensing trace short, and add the datasheet-recommended RC blanking on the sense node to prevent premature sampling caused by the leakage inductance reset spike.
The integrated power MOSFET dissipates conduction and switching losses inside the DIP-7 package. Estimated: in a sub-20W LED driver at ~85% efficiency, total loss on the order of 3 W is realistic, with the majority on the MOSFET and transformer. Provide generous copper area around the DIP-7 drain and ground pins, and verify junction temperature in an enclosed luminaire ambient (often 50-60 C) rather than at free-air room ambient; derate output power accordingly for sealed fixtures.
Compliance Information
RoHS compliance per DigiKey listing. Additional compliance details should be confirmed against the official onsemi product page.
