Request for Guidance on Implementing Synchronous Rectification (SR) on STM32G474

[Abdul-khalil]

Dear ST Support Team,

I am currently working on an LLC resonant converter project using the STM32G474 microcontroller.

My goal is to implement Synchronous Rectification (SR) using the STM32G474's PWM timers and Comparator peripherals. However, I am unsure about the correct peripheral configuration and firmware implementation.

I would appreciate your guidance on the following:

• How should I configure the PWM timers and Comparator peripherals in STM32CubeMX for Synchronous Rectification?

• Which timer and comparator connections are recommended for this application?

• Are there any reference projects, example firmware, or application notes available for implementing SR on the STM32G474?

• Are there any recommended CubeMX configurations or firmware examples that demonstrate this functionality?

• Could you recommend any official documentation, training material, videos, or tutorials that explain the implementation of LLC Synchronous Rectification using STM32?

My objective is to understand the complete implementation flow so that I can develop the firmware correctly.

Any reference designs, example projects, or educational resources would be greatly appreciated.

Thank you for your support.
 

[Khaled_DHIF]

Hello ​@Abdul-khalil ,

 

For STM32G474-based synchronous rectification (SR), the implementation approach described in AN5499 is a good starting point, even if the application note is written for a flyback converter. The same building blocks apply to an LLC secondary-side SR, but the thresholds, timing, and blanking windows must be tuned experimentally because the resonant waveforms are different. The main points are:

• Use a VDS sensing network to shift the SR MOSFET drain voltage into the MCU analog range.
• Use two comparators if possible:
  • COMP1 to detect SR turn-on when VDS falls below the threshold.
  • COMP2 to detect SR turn-off when VDS rises again near the zero-current point.
• Use an advanced timer such as TIM1/TIM8 in One-Pulse Mode:
  • COMP1 starts the pulse
  • the PWM output drives the SR MOSFET gate
  • COMP2 clears/stops the pulse
• Add blanking windows after turn-on and turn-off to avoid false triggering due to ringing or switching noise.
• Tune the thresholds and timing on the bench using scope measurements of VDS and VGS.

Link for AN5499: How to implement adaptive synchronous rectification in flyback converters using STM32 MCUs

 

Kind regards,

DHIFKhaled