VISUAL SOLUTIONS

Complete Reference Designs for Offline LED Drivers

STMicroelectronics offers a full range of components and reference designs for engineering teams working on offline LED driver applications. The range of solutions includes all the most common driver architectures, including constant current source, dimmable current source, flyback and step-down current source.

For common electrically isolated applications such as architectural and general lighting, STMicroelectronics recommends a design combining its VIPer family of integrated offline switching regulators with the TSM family of voltage and current controllers. The VIPer12A and VIPer22A devices combine a dedicated current-mode PWM (Pulse Width Modulation) controller and high-voltage power MOSFET in a single-chip device within a DIP-8 and SO-8 packaging. They feature an internal 60kHz oscillator, overcurrent and overvoltage protection and an automatic burst mode for low loads.

STMicroelectronics has used these devices as the basis of a set of complete reference designs implementing isolated flyback architecture. The designs are supplied as application notes and evaluation boards. They can be used to deliver a constant current output of 350mA and an output voltage from 3V to 27V, driving up to eight LEDs. A variant with integrated PWM dimming is available.



Designers seeking to replace halogen bulbs with LEDs can either use a VIPer device in conjunction with a step-down converter such as the STMicroelectronics L6902 or with a current feedback loop implemented with a device such as the TSM1051. For higher power applications, a reference design based on the VIPer 53 device includes power factor correction, allowing 11 LEDs to be driven with 350mA, or nine LEDs to be driven at 700mA.

In environments that can tolerate voltage ripple and a relatively high output capacitance, the STMicroelectronics L6562 device can be used in a cost-effective, integrated single-stage PFC and LED supply configuration, providing a high power factor and high efficiency at the load.

Other non-isolated applications, such as emergency lighting and traffic signals, can be realised using a device such as the L6565 quasi-resonant controller. STMicroelectronics provides several specimen applications for the L656x series of devices. These include a fixed off-time design which can accommodate varying numbers of LEDs without component changes; a high efficiency buck configuration that can power up to 30 LEDs in series; and a fully prototyped design, supplied in schematic format, for a circuit in which dimming is controlled by the input voltage.



Features

• Complete range of LED driver components and reference designs
• Designed for use at worldwide mains supply voltages
• Variety of topologies
  • Constant current source
  • Dimmable current source
  • Flyback
  • Step-down current source
• Range of switching regulators
  • Integrated PWM control and MOSFET
• Range of voltage and current controllers
• Power factor controllers
• Quasi-resonant controllers

Applications

• LED lighting
• General purpose illumination
• Display and architectural lights
• Signage
• Traffic signals

For further information, including a copy of the LED Drivers (AC-DC converters) Product Brief, please click here