45W USB Type-C™ Power Delivery Adapter Reference Design with Synchronous Rectification

July 27, 2018 by Paul Shepard

The STEVAL-USBPD45C 45W ac-dc adapter reference design from STMicroelectronics features a USB Type-C connector and functions as a USB Power Delivery provider with a single source port. The reference design accepts a wide input mains range and delivers 5V, 9V and 15V output voltage profiles, according to the Source Power Rules of the current USB Power Delivery specification.

The adapter architecture is based on two boards: the STEVAL-USBPD45P power supply board implementing the power stage in flyback topology with synchronous rectification, and the STEVAL-USBPD45I Digital Control Board designed to control the USB Type-C connector and manage the USB Power Delivery stack and the adaptive synchronous rectification algorithm.

The flyback converter is based on the STCH03 offline pwm controller for low standby adapters and the STF7N80K5 MDmesh™ K5 primary MOSFET.

On the secondary side, the adaptive synchronous rectification with STL40N75LF3 Power MOSFET is controlled and driven directly by the STM32F051 MCU, allowing an overall efficiency improvement with a very low external component count.

The USB type-C port is controlled by the certified STUSB1602A, enabling the VBUS power path and integrating high voltage protections on VBUS and CC lines.

The STUSB1602A also integrates VBUS monitoring and discharge path features for further external component count reduction. The chipset (STM32F051 + STUSB1602A) and relative stack X-CUBE-USB-PD running on STM32 are PD 3.0 certified.

STEVAL-USBPD45P circuit schematic (click on schematic to enlarge)

The adapter is protected against any destructive electrostatic discharge (ESD) from the USB Type-C connector by an ESDA25P35-1U1M ESD protection device which exceeds the IEC61000-4-2 Level 4 standard, offering ESD protection higher than 30kV on the VBUS pin. This protection also provides surge immunity against electrical over stress (EOS) to prevent damage to the internal circuitry by offering up to 35A 8/20μs protection, as per the IEC61000-4-5 standard.

The adapter is designed to meet the most stringent energy saving recommendations (EU and DOE CoC ver. 5 - Tier 2).

Features of the STEVAL-USBPD45C 45W ac-dc adapter reference design include:

  • USB PD 3.0 compliant
  • Universal input mains voltage range: from 90- to 264-Vac (frequency from 45Hz to 65Hz)
  • Three fixed PDOs available: 5V, 9V, 15V - 3A continuous operation
  • Load power limited to 45W
  • Minimum four-point average efficiency in active mode compliant with CoC ver. 5 - Tier 2 and DOE requirement
  • Efficiency >50% with Pout = 250mW; <35mW no-load standby power
  • Adaptive synchronous rectification with digital driver and controller
  • Load feedforward
  • OVP, UVP, OC, short-circuit protections
  • ESD protection: >30kV contact on VBUS and 20kV contact on CC lines and according to IEC61000-4-2
  • Immunity against surge current on VBUS pin up to 35A in a 8/20 μs waveform, according to IEC61000-4-5
  • Compact design: 73x51x25 mm
  • RoHS compliant