Charger for Portable Devices
The consumer sector requests compact power supplies for devices like cameras, notebooks, phones, tablets and other gadgets. The new USB-PD (power delivery) standard solves the hassle to take multiple power supplies when traveling by providing a common connector. With this standard it is possible to deliver up to 100W over USB where the voltage ranges from 5V to 20V. The goal of this project was to design a compact and cost effective power supply for such an application.
- Input voltage: 90V - 265V
- Output voltageg: 5V – 20V (galvanic isolation)
- Output power: 65W
- Power density: 1W/cm³
- Efficiency: >90%
For a compact and cost effective solution, a single stage topology was selected. With a two-switch forward converter, the required input and output voltage range can be covered. Synchronous rectification on the secondary side provides high efficiency with output currents up to 3.25A. The compact design required a thermal optimization iteration of the circuit. Placements of components is crucial for thermal performance and durability of the converter.
With a prototype, the design was verified and showed good performance. The single stage design was able to span the full input and output voltage range. Furthermore the topology selection was confirmed by a high efficiency up to 93% and over 90% in a wide range. With the compact format of 85x42x22mm the power supply fits in every hand bag.
Industry partner: Infineon Technologies AG, Munich (DE)