Minimizing the number of components enables a smaller, longer-lasting, and lower-cost system design.
Single-stage PFC Primary Side Control (PSR) LED Driver

LED lighting is evolving as a promising solution to replace traditional lighting sources such as fluorescent and incandescent lights. However, designers face several challenges in residential and commercial LED lighting applications supporting up to 20W, including bulbs, lights (GU10/E17, E26/27, PAR30/38), and tubes/bars. Implementing dimming functions within existing TRIAC dimmer infrastructure is not easy due to dimmer compatibility issues. Additionally, the requirement to implement within a small PCB space must also be considered.

To help designers solve these challenges, Fairchild Semiconductor developed the FL7732, a primary side control (PSR) controller for single-stage flyback driving with power factor correction (PFC) functionality, and the FL7730, which is compatible with TRIAC and analog dimming.
The FL7730 is an active PFC controller for single-stage flyback topology applications. The device supports both TRIAC and analog dimming. Implemented with Fairchild’s proprietary analog sensing technology, the device enables flicker-free TRIAC dimming control over the full range of optical output from 0 to 100%.

The FL7730 and FL7732 combine primary side control (PSR) and single-stage PFC topologies to reduce the number of components, such as input electrolytic capacitors and feedback circuits, providing a smaller size, longer lifespan, and lower system design costs.

To improve power factor and THD, both products are equipped with fixed on-time control functions using internal error amplifiers and low-bandwidth compensators. Precise constant current control (± 5%) controls the accurate output current independently of the input and output voltages, enabling designers to achieve high and enhanced lighting quality. To ensure DCM operation with optimized PF/THD and a simple design, the operating frequency is adjusted proportionally to the output voltages of both devices.

FL7730 for dimming, offering excellent PF (≥ 0.9), low Total Harmonic Distortion (THD) (Class C), and efficiency of up to 85% – FL7732, offering efficiency of over 85% in non-dimming applications – these products meet global energy saving regulations.

Fairchild provides a total solution portfolio for low-power (<20W), medium-power (20W–50W), and high-power (>50W) LED applications. Our highly integrated PWM and PFC controller solutions improve overall lighting efficiency while reducing the number of components, enabling smaller lamp sizes and simplifying complex designs. Fairchild’s extensive product portfolio ranges from discrete devices to integrated solutions including PFC controllers, high-voltage gate drivers, and MOSFETs. Along with efforts to save energy and meet the most stringent regulations, Fairchild has developed innovative products that maximize performance while reducing board space, design complexity, and system costs. Furthermore, online design tools and Fairchild’s global Power Resource Centers, comprised of regional centers of power engineers and FAEs, are the industry standard for customer design support.