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45W / 24V Output Isolated Flyback Reference Design for Smart Speakers and Tubular Motors

October 30, 2019 by Paul Shepard

DER-815 is an engineering report and reference design from Power Integrations which describes a 45W isolated flyback ac-dc power supply that can deliver Constant Voltage (CV), Constant Current (CC) and Constant Power (CP) output. The power supply is designed to provide a 24V constant voltage output from 0A to 1.88A load current.

Constant current is programmed at 3A by the IS pin resistor providing 45W constant power output from 24 V to 15 V. The DER board is designed to operate at input voltage range from 90- to 265-Vac.

The Innoswitch3-CP device is a quasi-resonant flyback controller that combines the primary and secondary controllers along with the power MOSFET in a single low-profile surface mount off-line flyback switcher IC.

The secondary-side controller incorporates secondary-side synchronous rectifier drive. The device also includes an innovative inductive coupling feedback link (FluxLink™), which safely bridges the isolation barrier and eliminates the need for an optocoupler.

DER-815 offers an accurate CV/CP/CC regulation throughout the input range. The key design goals were high efficiency and compact size design.

(click on schematic to enlarge)

Summary of Features

  • 45W constant power output at 24V to 15V
  • >91% average efficiency at nominal ac input
  • <75mW no-load input power
  • Low component count, 37 parts
  • Integrated protection and reliability features
  • Output short-circuit
  • Line and output OVP
  • Line surge or line overvoltage
  • Over temperature shutdown
  • Meets IEC 2.5kV ring wave, 2kV differential surge
  • Meets EN55015 conducted EMI

The document contains the power supply specification, schematic, bill of materials, transformer documentation, printed circuit layout, design spreadsheet, and performance data.