24V Constant Voltage GaN Power Reference Design for Smart Home Lighting

April 20, 2020 by Paul Shepard

A new design example report (DER-857) from Power Integrations describes a 24V constant voltage output isolated flyback ac-dc power supply suitable for smart home applications. This circuit is designed to operate from an input voltage range of 90- to 132-Vac and drive a nominal LED voltage string of 24V at 2.7A through a constant current post regulator.

The ultra-compact design features switched valley-fill PFC to support the newest models of LED track lights, spot lights or 2" downlights.

In addition, it provides 65W total output, enough to serve as the sole power supply of a modern low-voltage (24V) wiring system in a smaller home that features smart thermostats, video doorbells, smoke detectors and other home automation fixtures.

The combination of high power factor (>0.9 at 120Vac) and constant voltage output is achieved by PI's PowiGaN™-based high-power-density LYTSwitch™-6 LED driver IC. This highly efficient design meets DoE Level VI energy efficiency standards, and LYTSwitch-6's high level of integration both lowers overall cost and simplifies installation.

DER-857 Schematic (click on schematic to enlarge)

Summary of Specifications and Features

  • Accurate constant voltage and constant current regulation
  • Industry first ac-dc controller with isolated, safety rated feedback without optocoupler
  • High power factor, >0.9 at 120Vac
  • Ultrafast transient response
  • Highly energy efficient, >88% across line
  • Integrated protection and reliability features
    • Output short-circuit protection
    • Line and output OVP
    • Thermal foldback and over temperature shutdown with hysteretic automatic power recovery
  • CCM + quasi-resonant switching for precision CC/CV operation without need for loop compensation
  • Meets IEC 2.5kV ring wave, 1kV differential surge
  • Meets EN55022 conducted EMI