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New Power Control Reference Design from Microchip


New Design Allows a Secondary Side Device to Control The Primary Power Input


In modern offline AC-DC power solutions, programmability and adaptive control offer the flexibility and intelligence needed by smart home devices to better interface with their power systems. In these systems, a secondary side microcontroller is typically not capable of starting a system without the use of a separate bias power source. A new reference design from Microchip solves this problem using the MCP1012 auxiliary AC-DC controller, demonstrating 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 microcontroller. The control between the system and the load can be more precise and purposefully coupled, through a simplified design, reducing size and cost.

Click for Larger Image - New Power Control Reference Design from Microchip The reference design uses a patented isolation technique for isolated feedback. This patented isolation technique called Inde-Flux transformer technology is being licensed to Würth Elektronik eiSos. Inde-Flux technology is used in the Inde-Flux Transformer, the first transformer made by Würth Elektronik eiSos using this IP and sold as part of Microchip’s 15W MCP1012 reference design. This transformer combines the signal power and signal communication into one device, removing the need for optical feedback or an independent signal transformer. The option is also available to use more traditional approaches with a planar pulse transformer on the reference design, as well as the ability of the design to work with more traditional optocouplers and signal transformers. The secondary-side control is then enabled through a combination of the transformer and Microchip’s new MCP1012 AC-DC controller along with the SAM D20 series 32-bit microcontrollers.

The MPC1012 primary-side auxiliary controller provides for system start up, gating and protecting an offline flyback converter for the secondary microcontroller. 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 MCP1012 offline reference design provides the principal working elements 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 removing the need for optocouplers in many applications such as appliances and smart speakers. This Inde-Flux transformer technology, can be scaled to standard and custom transformer designs for different voltages and power levels as needed.

“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 utilizing offline power. Where this solution is used in systems with a secondary MCU, customers can realize up to 60% savings of the bias supply area and reduce the bias supply bill of materials costs by $3 or more.”

Technical Specifications of the MCP1012 Auxiliary Controller

  • High-Voltage Start-up
  • Only a Few External Components Required
  • Internal Open-Loop, Peak Current-Mode (PCM) Current Regulator for Start-up
  • Current Regulator Constant 21 µs Off Time
  • Programmable Low-Frequency Oscillator (LFO) Period
  • Cycle-by-Cycle Current Limiting
  • Protection Against Continuous Conduction Mode (CCM) of Operation
  • Able to Accept External PWM Commands from a Secondary Side Controller via Isolator
  • Undervoltage Lockout (UVLO) and Overvoltage Lockout (OVLO) Protections
  • Sleep and Wake-up Commands
  • Low Sleep Power: <15 mW
  • Robust Gate Driver, Able to Drive 2.2 nF Load at 65 kHz
  • Overtemperature Protection


More information on the MCP1012 Primary-Side Start-up IC can be found on the Microchip Web site at Microchip MCP1012 Auxiliary Controller product page

Note: The Microchip name and the Microchip logo are registered trademarks of Microchip Technology Incorporated in the U.S.A and other countries. All other trademarks mentioned herein are the property of their respective companies.


The company's Web site address is www.microchip.com
[Reprinted with kind permission from Microchip Corporation - Release Date, 6th January, 2021]