SLVAED3A July   2019  – April 2024 TPS568230

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Power Loss
    1. 2.1 Switching Loss
    2. 2.2 Conduction Loss
    3. 2.3 Driver Loss
    4. 2.4 Test Results
  6. 3Output Ripple
  7. 4Transient Response
  8. 5PCB Layout
  9. 6Conclusion
  10. 7References
  11. 8Revision History

2.2 Conduction Loss

In modern power conversion, though the V × I losses are much closer to the ideal or the value of zero when the switch is off, there are considerable losses when the switch is on, and that is due to the presence of on-resistance of MOSFET. This particular loss term is clearly the conduction loss.

The conduction loss coincides with the interval in which power is being processed in the converter. Unlike the switching loss, the conduction loss is not frequency-dependent. It does depend on duty-cycle. Equation 3 shows the conduction loss of a MOSFET.

Equation 3. P=IRMS2×RDS

where

  • IRMS is the RMS of the switching current
  • RDS is the on-resistance of the MOSFET

The diode conduction loss is the other major conduction loss term in the buck converter. It is equal to VD × ID_AVG, where VD is the diode forward-drop. ID_AVG is the average current through the diode which is equal to IO × (1-D) for the buck converter. It is also frequency-independent.