USERS MANUAL AN1603 ISL6752/54EVAL1Z Rev.2.00 May 25, 2018 ZVS DC/DC Power Supply with Synchronous Rectifiers Evaluation Board Abstract The ISL6752/54EVAL1Z is a new design based on the ISL6752EVAL1Z but with several design modifications to improve the efficiency from 90% to 95%. The control circuit has been moved off the main board onto a daughter card. Two different daughter cards are provided: one using the ISL6752 and the other using the ISL6754. Both control cards use the Intersil Zero Voltage Switching (ZVS) topology. The ISL6752 daughter card features pulse by pulse current limiting, and the ISL6754 daughter card features a patented method for average current limiting that results in a brick-wall current limit profile. The ISL6752/54EVAL1Z Printed Circuit Board (PCB) layout has also been greatly improved over the ISL6752EVAL1Z. Even though the overall size of the board has been reduced, the copper losses have been reduced as well. In addition to the ZVS function, this board also incorporates N-Channel FETs as secondary side rectifiers, also known as Synchronous Rectifiers (SR). Power dissipation of the secondary side rectifiers is reduced because the conduction losses of SRs are significantly less than the conduction losses of PN or Schottky diodes. Table of Contents Scope 3 Block Diagram 4 Daughter Cards .4 ZVS Full Bridge 5 High Voltage Protection 5 Primary Side Current Sensing .6 Synchronous Rectifier Drive Circuit .6 Current Doubler Output .6 Basic SR Principles 7 SR Drive Timing Requirements 7 SR Drive and Bias .8 Current Doubler .8 Current Sensing 10 Conclusion 11 References 12 Evaluation Board Set-up . 12 Setting Up . 12 Danger . 12 Caution 12 Waveforms 13 ZVS 13 ZVS Waveforms . 13 Load Transients Waveforms . 14 Output Ripple and Noise Waveforms . 17 Transformer Current, Primary Winding Waveforms . 18 Performance Curves 19 PCB Layout 20 Schematics- Main Board, ISL6752/54EVAL1Z 25 Schematics - Daughter Card . 27 Bill of Materials 28 AN1603 Rev.2.00 Page 1 of 33 May 25, 2018ZVS DC/DC Power Supply with ISL6752/54EVAL1Z Synchronous Rectifiers Evaluation Board List of Figures FIGURE 1. NEW ISL6752/54EVAL1Z 3 FIGURE 2. ISL6752/54EVAL1Z BLOCK DIAGRAM 4 FIGURE 3. ISL6752 DAUGHTER CARD 4 FIGURE 4. ISL6754 DAUGHTER CARD .5 FIGURE 5. FULL BRIDGE .5 FIGURE 6. PROTECTION CIRCUITS .5 FIGURE 7. PRIMARY SIDE CURRENT SENSING 6 FIGURE 8. SRs AND DRIVERS .6 FIGURE 9. PULSE TRANSFORMER AND DRIVER .6 FIGURE 10. CURRENT DOUBLER OUTPUT 7 FIGURE 11. TIMING FOR SRs AND BRIDGE FETs 7 FIGURE 12. SIMPLIFIED SR DRIVE SCHEMATIC .8 FIGURE 13. CURRENT FLOW IN TWO INDUCTORS OF CURRENT DOUBLER TOPOLOGY 9 FIGURE 14. INDUCTOR CURRENT WAVEFORMS .9 FIGURE 15. PRIMARY SIDE CURRENT SENSING CIRCUIT USING ONE CT 10 FIGURE 16. PERFORMANCE OF CURRENT SENSING OUTPUT . 10 FIGURE 17. NO LOAD SENSE VOLTAGE ACROSS RS . 10 FIGURE 18. PLACEMENT OF TWO CURRENT SENSING TRANSFORMERS 11 FIGURE 19. CURRENT SENSING TRANSFORMER IN THE COMMON SOURCE LEAD 11 FIGURE 20. CURRENT SENSING TRANSFORMER IN THE COMMON DRAIN LEAD . 11 FIGURE 21. RESONANT SWITCHING WITH 100% (50A) LOAD . 13 FIGURE 22. RESONANT SWITCHING WITH 50% (25A) LOAD 13 FIGURE 23. STEP LOAD: 0A TO 12.5A (12.5A DELTA) 14 FIGURE 24. STEP LOAD: 25A TO 37.5A (12.5A DELTA) . 14 FIGURE 25. STEP LOAD: 37.5A TO 50A 15 FIGURE 26. STEP LOAD: 0A TO 25A . 15 FIGURE 27. STEP LOAD: 0A TO 50A . 16 FIGURE 28. SHORT CIRCUIT RELEASE WITH ISL6754 16 FIGURE 29. OUTPUT RIPPLE, 50A LOAD, 40MHz BANDWIDTH .17 FIGURE 30. OUTPUT RIPPLE, 50A LOAD, 145MHz BANDWIDTH 17 FIGURE 31. PRIMARY TRANSFORMER CURRENT vs OUTPUT LOAD TRANSIENT (25A TO 50A) 18 FIGURE 32. PRIMARY TRANSFORMER CURRENT vs OUTPUT LOAD TRANSIENT (50A TO 25A) 18 FIGURE 33. POWER EFFICIENCY vs LOAD (ISL6752 OR ISL6754) . 19 FIGURE 34. LOAD REGULATION 19 FIGURE 35. PULSE BY PULSE vs AVERAGE CURRENT LIMIT . 19 FIGURE 36. SILKSCREEN TOP 20 FIGURE 37. LAYER 1 . 21 FIGURE 38. LAYER 2 . 22 FIGURE 39. LAYER 3 . 23 FIGURE 40. LAYER 4 . 24 FIGURE 41. MAIN BOARD, PRIMARY, ISL6752 54EVAL1Z . 25 FIGURE 42. MAIN BOARD, SECONDARY, ISL6752 54EVAL1Z . 26 FIGURE 43. DAUGHTER CARD, ISL6754DBEVAL 27 FIGURE 44. DAUGHTER CARD, ISL6752DBEVAL1Z 28 AN1603 Rev.2.00 Page 2 of 33 May 25, 2018