SLYT877 April   2026 LMG3427R030 , TMS320F280039C

 

  1.   1
  2. 1 Introduction
  3. 2 How to let PFC enter TCM at light loads
  4. 3 How to detect zero current
  5. 4 How to achieve ZVS at TCM
  6. 5 Transitioning between CCM and TCM
  7. 6 Dynamic dead time
  8. 7 Control law and PWM generation
  9. 8 Test results
  10. 9 Conclusion
  11. 10References
  12. 11About the author

3 How to detect zero current

For TCM control, adding a zero current detection (ZCD) circuit by placing a resistor on the PFC ground return path or adding a second winding on the boost inductor will detect the instant that the inductor current drops to zero. Some devices, such as TI's LMG3427R030 gallium nitride (GaN) field-effect transistor (FET), have a built-in ZCD circuit, generating a ZCD signal when the current goes to zero, as shown in Figure 3. Using this device as a high-frequency switch can significantly simplify the design process. The ZCD signal is sent to a microcontroller (MCU) for further processing.


ZCD signal generation

Figure 3 ZCD signal generation