Inbox adapters and chargers

Overview

USB power delivery electronic design

The USB PD standard (USB power delivery) allows to charge quickly via a USB connection. The specification caters to much higher power ratings than typical smartphone-based charging designs, as it is intended to power hard drives, printers, and displays, as well as larger portable electronics like laptops. In other words, it enables increased power levels from existing USB standards. The maximum 100 W power supply is achieved with 20 V and up to 5 A. Making use of the highest power modes also requires specially rated USB cables, as standard cables are only rated for 7.5W at most. In addition to faster charging, this USB standard enables both host and peripheral devices to provide power, the power direction is no longer fixed. Essential is the communication of a suitable Power Rule, i.e. the source and the host exchange their requirements to figure out how much power to transfer. In this way, power management across multiple peripherals is optimized. Each device is supplied only the power it requires (e.g. low power cases such as headsets vs a laptop being a high power case).

Discover the reference designs, boards, and design support documents.

Products

System diagram: USB power delivery

Learn more - the right products for your topology and your power class

10W to 75W converter designs based on flyback topology or DCM PFC topology

The 700 V CoolMOS™ P7 offers a price competitive solution for consumer applications such as chargers and adapters in the power range from 10 W to 75 W. This product addresses the low power SMPS market where it tackles common barriers through excellent performance and ease-of-use. The named power converters are typically based on flyback topologies. 700 V CoolMOS^TM P7 is a tailored technology optimized for flyback and DCM (discontinuous current mode) PFC applications. SOT-223 offers a smaller footprint while being pin-to-pin compatible with DPAK while achieving similar thermal performance.

The 600V CoolMOS™ PFD7 is dedicated to ultrahigh power density designs and offers up to 1.17 percent efficiency increase compared to the CoolMOS™ P7 technologies, which leads to a power density increase of 1.8 W/in³. Its feature set includes a robust fast body diode, up to 2kV ESD protection, and low EMI.

Forced frequency resonant flyback controller for high-density adapters

The XDPS21071 is a digital PWM controller for high-density adapter applications based on DCM flyback topology. Check the reference design schematics for a 45W USB power delivery solution.

OptiMOS™ PD optimized for Sync Rectification

OptiMOS™ PD is an N-channel power MOSFET family meeting highest efficiency standards even in a compact 3x3 package, achieves a lower temperature in a 3x3 package compared to the next best alternative in 5x6. BOM cost reduction can be achieved as the parts are fully driven from 4.5V (low threshold voltage) by minimized on-state resistance, low gate, output and reverse recovery charges.

High power density chargers/adapter designs with more than 30W

In a completely enclosed USB adapter, any size-reduction through high switching frequency or package innovation must go hand in hand with efficiency improvements to maintain low component and adapter case temperatures. The picture shows the relationship between power density and the minimum efficiency required to keep the adapter case temperature below 70°C for a 65 W adapter. It is evident that to increase the power density above 20 W/in3 , the converter efficiency must be above 92.5 percent. Typically, for chargers and adapters with universal input range (90 Vac-264 Vac) the most critical operating point to meet the minimum efficiency requirement is at:

Maximum continuous output power
Minimum input voltage (typically 90 Vac)

The reason for this is that at this operating point the conduction losses reach the maximum, resulting in a poorer overall efficiency compared to high input-line conditions.

The single-switch QR Flyback has been widely adopted in power adapter applications: it is operated in Discontinuous Conduction Mode (DCM), achieving Zero Voltage Switching (ZVS) at low-line and partial hard switching at high-line. However, the hard-switching operation occurring at high-line together with the lack of recovery of the transformer leakage energy limits the maximum switching frequency at which the adapter can be operated. In order to overcome these limitations designers are moving toward topologies embedding the following features:

Soft-switching (ZVS) operation, regardless of the input-line voltage and loading conditions
Recovery of the transformer leakage energy

Learn more about how to include ZVS operation in your design

Boards

Tools & Software

Reference designs

45 W flyback converter reference design for USB power delivery (PD)

This document is intended for users who wish to design a FFR ZVS Flyback converter (forces frequency zero voltage switching) e.g. for High Density (HD) adapters. It describes a 45W off-line flyback converter design of: