Power Tips: Compensating Isolated Power Supplies

Once you understand the transfer function of an opto-isolator and TL431 circuit, it becomes easier to compensate isolated power supplies. In this Power Tips "Ask the Expert" video Dave asks TI’s Brian King to do the math to derive this transfer function and gain insight to the location of the compensator poles and zeros.

• Read Power Tips: How to measure frequency response in isolated power supplies on TI’s Power house blog.
• Power Tips: Compensating Isolated Power Supplies article on EETimes.
• Read additional blog posts authored by Brian King.

• Learn more about the following power supply controllers related to this video:
  • UCC2809-2 primary-side controller
  • UCC28740 constant-voltage, constant-current flyback controller using opto-coupler feedback.
  • UCC2897A advanced current-mode active clamp PWM controller
  • UCC27511 4-A/8-A single-channel high-speed low-side gate driver
• Download the following TI Design power reference designs:
  • PMP9203 – Universal AC Input 5V/2A USB Adaptor with Fixed Frequency Operation Reference Design
  • PMP9204 – Universal AC Input 5V/2A USB Adaptor with DCM/Valley-Switching and Opto Feedback Reference Design
  • PMP9720 – 48V-60Vdc Input, 12V/150W Active Clamp Forward - Reference Design