Infineon launches flyback converter for USB-PD to reduce power losses

In most wall-powered electrical systems, one of the significant sources of power loss is during the power conversion process. Between the wall power supply and the DC load, there is a need to rectify the AC to DC power and convert it from the rectified DC to a lower voltage regulated DC power. This whole process can result in significant power losses.

There are many converters that are designed to maximize efficiency. One example is the flyback converter, which has become increasingly popular due to its simple output filter design and ability to be used for multiple outputs. An example is the use of a flyback converter topology in a cell phone charger.

To that end, Infineon Technologies this week released a new series of reference designs for USB-PD-based chargers that utilize a flyback topology for maximum efficiency.

What is a Flyback Converter?

The flyback converter is a switching power supply (SMPS) DC/DC converter topology that operates in a mutual inductive manner.

In many ways, a flyback converter operates similarly to a buck converter. The main difference is that the flyback converter replaces the inductor with the primary coil of the transformer and utilizes the secondary coil as its output.

Examples of flyback and buck-boost converter circuits. Image courtesy of Anurag Gupta

These circuits typically use a pulse width modulation (PWM) signal to control the base of a switching transistor, thereby modulating the current flowing through the primary winding of the transformer. When current flows through the primary winding, energy is stored as a magnetic field. When the current stops flowing, the stored magnetic field disappears and the release of energy appears in the secondary winding where it is used as output. In a practical circuit, feedback is used to monitor the output voltage and control the PWM signal as needed.

The advantages of a flyback transformer include isolation between input and output, high efficiency of the SMPS, the ability to provide multiple output voltages, and importantly, the low number of components required compared to other SMPSs.

Block diagram of the XDPS2201. Image courtesy of Infineon Technologies

According to the company, their new power supply, the XDPS2201, combines the advantages of an asymmetrical half-bridge flyback topology and a resonant converter, enabling soft switching.

This soft switching minimizes switching losses and EMI, two of the biggest drawbacks of SMPS. Along with this, the converter also comes with an adaptive digital algorithm that allows it to achieve the highest possible performance under different and varying input and output conditions.

According to the datasheet, this converter can help achieve power densities above 20 W/inch^3 and efficiencies above 93%.

As the demand for faster charging of mobile devices continues to grow, more innovation is needed in this area. That appears to be exactly what Infineon has done here. While improving the efficiency of the flyback converter, it also helps to minimize issues such as EMI, which is a major step in the right direction.