Reference design enables a secondary side microcontroller to control primary power

In modern offline AC/DC power solutions, programmability and adaptive control provide the flexibility and intelligence required by smart home devices to better interface with their power systems. In these systems, a secondary side MCU is generally not able to start a system without utilising a separate bias power supply. A new reference design from Microchip Technology solves this problem using the MCP1012 high voltage auxiliary AC/DC controller, exhibiting the ability to remove the independent bias power supply in many applications. The offline auxiliary device allows the system to transfer control of the power and duty cycle to a secondary MCU. The control between the system and the load can be more precise and purposefully coupled, through a design that is able to be simplified, decreasing size and cost.

The reference design employs a patented isolation technique for isolated feedback. This technique, called Inde-Flux transformer technology, is being licensed to Würth Elektronik eiSos. Inde-Flux technology is utilised in the Inde-Flux Transformer, the first transformer made by the company utilising this IP and sold as part of Microchip’s 15W MCP1012 offline reference design. This transformer merges the signal power and signal communication into one device, eradicating the necessity for optical feedback or an independent signal transformer. The option is also offered to use more conventional approaches with a planar pulse transformer on the reference design, as well as the capability of the design to work with more traditional optocouplers and signal transformers. The secondary-side control is then enabled via a combination of the transformer and a newly released MCP1012 AC/DC controller along with the SAM D20 series 32-bit MCU.

“The combination of our Inde-Flux technology in a Würth Elektronik eiSos transformer, our MCP1012 AC-DC controller and our SAM D20 series 32-bit MCU creates a unique solution to offline power management,” said Rich Simoncic, senior vice president of Microchip’s analog, power and interface business unit. “These devices enable a simpler, more reliable implementation of complex bi-directional communication between the primary and secondary elements used in many isolated applications utilising offline power. Where this solution is used in systems with a secondary MCU, customers can realise up to 60% savings of the bias supply area and reduce the bias supply bill of materials costs by $3 or more.”