1. Prof R T Kennedy1 EET 423 POWER ELECTRONICS -2

2. Prof R T Kennedy2 IDEAL TRANSFORMER MAGNETIC DEVICE ELECTRICAL ISOLATION FUNCTION: TRANSFER ENERGY SCALE CURRENT and VOLTAGE TRANSFER NO ENERGY STORAGE

3. Prof R T Kennedy3 REAL TRANSFORMER SOME ENERGY STORAGE MAGNETISING INDUCTANCE (WITHIN CORE) minimised by using gapless core minimised by using high permeability core LEAKAGE INDUCTANCE (EXTERNAL to CORE)

4. Prof R T Kennedy4 TRANSFORMER PARASITICS

5. Prof R T Kennedy5 TRANSFORMER LIMITATIONS LOW FREQUENCY core saturation SMPS FREQUENCIES core loss

6. Prof R T Kennedy6 FLYBACK CONVERTER TRANSFORMER BASICALLY MULTI WINDING COUPLED INDUCTOR energy storage in non-magnetic gap energy recoverable DESIGN LIMITATIONS core + winding losses  temperature rise & efficiency fixed  core losses reduce with temperature increase core saturation saturation flux density reduces with temperature increase leakage inductance

7. Prof R T Kennedy7 FLYBACK CONVERTER TRANSFORMER

8. Prof R T Kennedy8 FORWARD CONVERTER TRANSFORMER NORMAL TRANSFORMER NO energy storage ideally leakage inductance represents energy stored in non-magnetic regions mutual inductance represents stored energy in core DESIGN LIMITATIONS core losses leakage inductance

9. Prof R T Kennedy9 FORWARD CONVERTER TRANSFORMER

10. Prof R T Kennedy10 LEAKAGE INDUCTANCE EFFECTS

11. Prof R T Kennedy11 FLYBACK TRANSFORMER Magnetising Current is important in flyback transformers (& inductors) represents Energy Storage requirements Leakage Inductance is a parasitic

12. Prof R T Kennedy12 FERRITE CORE TOROIDAL TRANSFORMER

13. Prof R T Kennedy13

14. Prof R T Kennedy14 REDUCE LEAKAGE INDUCTANCE

15. Prof R T Kennedy15

16. Prof R T Kennedy16 LOW OUTPUT VOLTAGE HIGH OUTPUT CURRENT

17. Prof R T Kennedy17 OUTPUT CURRENT SHARING

18. Prof R T Kennedy18 HIGH EFFICIENCY