Circuit design of 30W set-top box power supply

Summary:

working principle

The isolated flyback converter shown in the figure is based on the TOP257PN (U2) in the TOPSwitch-HX IC family. Selecting a P-package (8-pin DIP package) eliminates the need for external heat sinks and reduces cost. The converter acts as an external adapter for the set-top box power supply (where subsequent multi-output conversions are performed directly by several DC/DCs internally), which typically requires lower standby and no-load power consumption.

design feature

  • Low cost, low component count, compact and lightweight power supply
  • Extremely energy efficient
  • Low load and standby power consumption
  • No-load power consumption less than 250 mW at 265 V AC input
  • Output power is 30 W when operating at 50 °C, no external heat sink is required
  • Integrated safety and reliability:
  • Precise automatic recovery and hysteretic shutdown with hysteresis to keep PCB temperature within safe conditions under all conditions
  • Enters the auto-restart protection state when the output short circuit and the feedback loop open loop
  • Excellent input voltage regulation and load regulation
  • Conforms to EN55022 and CISPR-22 Class B for conducted EMI requirements with EMI margin >10 dBμV

See the PDF document for details (click on the PDF file to download)

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