Enabling Secondary Side Microcontroller To Control Primary Power

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New AC-DC microcontroller utilisess Inde-Flux transformer technology licensed to simplify design, and reduce size and cost

Programmability and adaptive control are necessary for modern offline AC-DC power solutions to flexibly interface smart home devices with power systems. In these systems, a secondary side microcontroller (MCU) is typically not capable of starting a device without a separate bias power supply.

Solving this problem is the MCP1012 high voltage auxiliary AC-DC controller that has the ability to remove the independent bias power supply in many applications. The MCP1012 offline auxiliary device enables the system to transfer control of the power and duty cycle to a secondary MCU, thus maintaining a precise and purposefully coupled control between the system and the load that also reduces size and cost.

The reference design uses an isolation technique called Inde-Flux transformer technology for isolated feedback. The transformer combines signal power and signal communication into one device, eliminating the need for optical feedback or an independent signal transformer. It can be used for more traditional approaches with a planar pulse transformer on the reference design, as well as to design with more traditional optocouplers and signal transformers.

The secondary-side control is then enabled through a combination of the transformer and the MCP1012 AC-DC controller along with the SAM D20 series 32-bit MCU. The MPC1012 primary-side auxiliary controller provides system startup, gating and offline flyback converter protection for the secondary MCU. The device enables a range of benefits such as direct measurement and active regulation of voltage and/or current, high loop bandwidth by direct loop closure and simplified communication for load-referenced systems.

The 15W MCP102 offline reference design is suitable for a 15W offline power design with the necessary firmware to enable the elimination of the auxiliary power supply on the primary side. This can reduce the complexity of the system including eliminating the need for optocouplers in many applications such as appliances and smart speakers. The Inde-Flux transformer technology can be scaled to standard and custom transformer designs for different voltages and power levels.

“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,” said Rich Simoncic, senior vice president of Microchip’s analog, power and interface business unit.

The 15W MCP1012 offline reference design, part number EV37F82A, is now available from Microchip Technology. The company also offers a fundamental 1W evaluation board, the DT100118, for the MCP1012 AC-DC controller from Wurth Elektronik.


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