AC/DC Power Supply Embedded Design

Challenge

Renewable energy & sustainability are creating exciting new product development opportunities. A start-up company in the electric mobility space tapped AppliedLogix to help them develop a high-efficiency, compact, AC/DC power supply for their product.

One of the most challenging aspects of this design was the combination of achieving high-efficiency power conversion (i.e. high power-density) while meeting the stringent form factor requirements. The safety/regulatory requirements (designing for CE & UL), i.e., Isolation, creepage, and clearance, also proved to be quite challenging to achieve.

Solution

The AppliedLogix Team conceived, designed, and delivered a custom embedded solution that met all aspects of the customer’s requirements goals for a high-power-density, low cost, dual USB Type-C portable charger. The solution was delivered on time and in lock-step with the client’s product development schedule. The development effort started with a requirements generation phase, something we call a phase 0, and once completed, flowed directly into the full product development / commercialization effort.

Benefits

• High-efficiency power conversion
• Small form-factor
• Dual USB Type-C power delivery

System Overview

There are 5 custom PCBs (Printed Circuit Boards) contained within the device. As shown in the mechanical drawing view, each PCB was carefully optimized for space utilization – components are nested from adjacent boards in a 3D manner to minimize the overall package size.

The main hardware functionality is broken down into:

1. Input power filtering, overvoltage & transient protection
2. Power Factor Correction (STCMB1 -Transition Mode PFC with X-cap discharge)
3. Resonant power conversion (STCMB1 – LLC resonant combo controller)
4. Synchronous rectification & output filter (SRK2001 -Synchronous Rectification controller)
5. USB power delivery negotiation  – providing  multiple  output  voltage  & current  levels (Bluetooth Low Energy Controller – BMD-300-A-R – based on a NORDIC NRF52832 SOC)

AppliedLogix built a USB Power Delivery protocol stack from the ground up to support the application’s unique load-sharing and port-prioritization requirements. The stack handles detection and interaction with devices plugged into the power supply, and negotiation of power contracts at standard PD levels depending on total load, device capabilities, and environmental conditions. The supply’s firmware can re-negotiate USB-PD power contracts on both ports depending on internal temperature, and a Bluetooth Low-Energy (BLE) connection allows monitoring from a mobile device.

The supply’s firmware is supported by a thorough unit test suite and targets the Nordic nRF52 microcontroller. The USB-PD stack is platform-independent, and has also been utilized on ST’s STM32 and TI’s TiVA ARM Cortex-M microcontrollers.