65W GaN-Based Adapter for Appliances and Industrial Applications – Reference Design

August 25, 2019 by Paul Shepard

The DER-747 from Power Integrations is a 20V / 3.25A output ac-dc power supply using the InnoSwitch3-EP. This charger design shows the high power density and efficiency that is possible due to the high level of integration of the InnoSwitch3-EP controller, combined with the internal gallium-nitride power switches, providing high levels of performance.

The quasi-resonant InnoSwitch3-EP combines primary, secondary and feedback circuits in a single surface-mounted package. This highly-integrated device enables solutions with very low component counts. The DER-747 reference design, for example, includes only 43 components.

In the InnoSwitch3-EP GaN switches replace the traditional silicon high-voltage transistors on the primary side of the IC, reducing conduction losses when current is flowing, and considerably reducing switching losses during operation. This results in substantially less wasted energy and therefore increased efficiency and power delivery from the space-saving InSOP-24D package.

Populated circuit board photograph, top.

Populated circuit board photograph, bottom

Summary and Features

  • InnoSwitch3-EP is industry first ac-dc IC with isolated, safety rated integrated feedback
  • All the benefits of secondary-side control with the simplicity of primary-side regulation
    • Insensitive to transformer variation
    • Built-in synchronous rectification for high efficiency
  • Meets DOE6 and CoC Tier 2 V5 2016
  • <40mW no-load input power
  • Primary sensed overvoltage protection
  • Very low component count: 43 components
  • >6db margin on conducted EMI
  • Very high average efficiency
    • 92.5% at 115Vac and 230Vac
  • Very high full-load efficiency
    • 92.0% at 115Vac and 93.5% at 230Vac