Author:
Ally Winning, European Editor, PSD
Date
07/24/2025
PDF
Auxiliary power supplies are popular designs that are used in many consumer and industrial applications. There are many products that require mains power to run a motor or other device, but also need much lower voltages to run the control systems and other low power circuits. It is difficult to drop from the mains voltage to a much lower voltage with designers usually facing a choice between losing efficiency by using a single stage conversion, or prioritizing efficiency with the downside of needing a higher cost and larger solution. Neither of those options are very acceptable to consumers who are cost sensitive and want smaller products and legislators, who demand high efficiency. Recently, Infineon has launched the latest generation of the company’s CoolSET System-in-Package (SiP) family, which has been developed to give power designers a conversion from AC inputs of between 85V to 265V into a stable 12V DC output at up to 93% efficiency in a small package.
The CoolSET SiP devices integrate multiple critical functions into the DSO-12 package, including the primary-side PWM controller, the secondary-side synchronous rectification (SR) controller, and Infineon’s proprietary CT-Link Technology, a galvanically isolated digital communication interface that replaces traditional optocouplers. This high level of integration eliminates the need for multiple discrete components, significantly reducing PCB space and simplifying system design. Despite the compact form factor, the CoolSET solution can deliver up to 60W of output power without the need for a heatsink, essential for space-constrained applications.
The CoolSET solution is built on Infineon’s proven CoolMOS C7 technology. The SiP includes a rugged 800V MOSFET with a high-voltage startup cell rated up to 950V. Zero Voltage Switching (ZVS) flyback topology is used to minimize switching losses, reduce EMI, and boost efficiency. Additionally, the device’s multi-mode control algorithm adapts dynamically across varying loads, optimizing power consumption. For standby operations, the solution boasts consumes under 30mW, making it one of the most energy-efficient solutions in the market.
The CT-Link Technology provides isolated communication from the primary side of the circuit to the secondary. Abdul explains, “CT-Link is Infineon’s proprietary galvanic isolation technology, which has been in production for more than 20 years and is now in its fourth generation. It uses a coreless transformer to provide reinforced isolation of up to 5.7kV and is rated for 37.5 years, enabling the secondary controller to send information to the primary controller without sacrificing isolation or efficiency. CT-Link technology enhances reliability and also improves signal integrity, simplifying compliance with safety standards, reducing the need for optocouplers, which degrade over time.”
The CoolSET SiP family is available in two variations – the 60W EM Series is tailored for home appliances and includes enable/disable features for the primary-side LDO, giving designers control over power states to reduce consumption, and the LM Series is geared toward industrial SMPS and server auxiliary supplies, offering flexible external control for bus voltage sensing, and delivering up to 45W output power. A future variant incorporating wide bandgap technology is also in the pipeline, and expected to push output capabilities up to 100W, further expanding its use in industrial and AI server applications.
