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ECE 4284 Flyback Converter Design

ECE 4284 Flyback Converter Design. Dong Dong , Jing Xue , Sara Ahmed, Zidong Liu, Gulliate Tensaw May 2009. Review of Previous Work. Power Stage Design Input voltage: 15~25V input Output voltage: 5V, ripple 1% Nominate output power: 25W Half load change response: ΔV out within 5%

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ECE 4284 Flyback Converter Design

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  1. ECE 4284Flyback Converter Design Dong Dong, Jing Xue, Sara Ahmed, Zidong Liu, Gulliate Tensaw May 2009

  2. Review of Previous Work • Power Stage Design • Input voltage: 15~25V input • Output voltage: 5V, ripple 1% • Nominate output power: 25W • Half load change response: ΔVout within 5% • Primary side switching frequency 50 kHz • Device Selected • MOSFET: SI4896DY-T1-E3CT-ND, 80V 6.7A • Diode: 497-2753-5-ND, 45V 15A • Controller Design • Compensator Transfer Function Parts of Design Parameters

  3. Flyback Converter Design Outline • Schematic Circuit Design • Voltage Regulation Part • Power Stage Primary Part • Power Stage Transformer Part • Power Stage Secondary Part • Controller and Feedback Part • Printed Circuit Board Design • Layout Consideration • Hardware Fabrication • Transformer Winding & Test • Soldering & Test Procedure • Verification Results • Problems & Discussion

  4. Schematic Circuit Design Flyback Circuit Sketch

  5. Schematic Circuit Design: Voltage Regulation Part • Components: • Voltage Regulator: LM78L15ACM-ND • C1=0.33μF, C2=0.01μF, C3=0.1μF, R1=1KΩ • Application: Provide constant input voltage for the circuit • Power Stage Input: Vg=15~25V • Controller Power: VC=15V • Pull-up Voltage for Gate Signal: VCC=15V • Special Notes for Design: • Coupling & decoupling cap to reduce voltage ripple • Low pass filter between VC & VCC to reduce switch noise

  6. Schematic Circuit Design: Power Stage Primary Part • Components: • Input Capacitor: C4=100μF • Snubber: C9=0.1μF, R2=500Ω, D2: ES3B-E3/57TGICT-ND • Application: • Input Cap: Reduce input voltage ripple • Snubber: • Special Notes for Design: • Number of input cap depends on the length of the bus

  7. Schematic Circuit Design: Power Stage Primary Part (Cont’d) • Components: • MOSFET Switch: SI4410DY • Gate Drive: D4: RB751V-40-TPMSCT-ND, R7=10Ω, R8=10KΩ • Application: • D4 is used to increase turn-off speed • R7 is used to limit the instantaneous current that is drawn when the FET is turned on • Special Notes for Design: • Number of input cap depends on the length of the bus

  8. Schematic Circuit Design: Power Stage Primary Part (Cont’d) • Components: • T2: 50:1 Current Transformer • D3: RB751V-40-TPMSCT-ND, R5= 6.25Ω, C17= • Application: • Limit the maximum current passing through MOSFET • Special Notes for Design: • Number of input cap depends on the length of the bus

  9. Schematic Circuit Design: Power Stage Transformer Part • Components: • Transformer N1:N2=3:2 • Magnetizing Inductance(referred to pri.): 80μH • Leakage Inductance(referred to pri.): Small as possible • Special Notes for Design: • Reverse polarity for Flyback transformer

  10. Schematic Circuit Design: Power Stage Secondary Part • Components: • Diode: D1: 497-2753-5-ND, 45V, 15A • Snubber: R12=R13=10Ω, C24=330pF • Output Cap: C15=1mF • Application: • Snubber • Special Notes for Design: • Reverse polarity for flyback transformer

  11. Schematic Circuit Design: Controller • Components: • Controller: UC3825DW • Application: Produce PWM gate signal • Open-loop reference voltage • Closed-loop amplifier & comparator • Soft-start • Current limit protection

  12. Schematic Circuit Design: Controller (Cont’d) • Components: • C23=18nF • Application: Soft-start Time Control • Soft-start time=10µs • CSSVSS=Q=9µA*10µs • Components: • R9=5.36kΩ, C22=5.73nF • Application: Switching Frequency Control • Max. Duty Cycle=0.96 • Osc_freq ≈1.6*DMAX/(CT *RT)=50 kHz • Components: • C20=, C21= • Application: • Regulate VC

  13. Schematic Circuit Design: Controller (Cont’d) • Components: • R11=, C25= • Application: • Components: • R11=, C25= • Application: Current Limit Protection • Max. Duty Cycle=0.96 • Osc_freq ≈1.6*DMAX/(CT *RT)=50 kHz

  14. Schematic Circuit Design: Feedback Loop • Application: Closed-loop Compensator • List of RC parameters

  15. Flyback Converter Design Outline • Schematic Circuit Design • Voltage Regulation Part • Power Stage Primary Part • Power Stage Transformer Part • Power Stage Secondary Part • Controller and Feedback Part • Printed Circuit Board Design • Layout Consideration • Hardware Fabrication • Transformer Winding & Test • Soldering & Test Procedure • Verification Results • Problems & Discussion

  16. Printed Circuit Board Design

  17. Printed Circuit Board Design

  18. Flyback Converter Design Outline • Schematic Circuit Design • Voltage Regulation Part • Power Stage Primary Part • Power Stage Transformer Part • Power Stage Secondary Part • Controller and Feedback Part • Printed Circuit Board Design • Layout Consideration • Hardware Fabrication • Transformer Winding & Test • Soldering & Test Procedure • Verification Results • Problems & Discussion

  19. Hardware Fabrication

  20. Flyback Converter Design Outline • Schematic Circuit Design • Voltage Regulation Part • Power Stage Primary Part • Power Stage Transformer Part • Power Stage Secondary Part • Controller and Feedback Part • Printed Circuit Board Design • Layout Consideration • Hardware Fabrication • Transformer Winding & Test • Soldering & Test Procedure • Verification Results • Problems & Discussion

  21. Verification Results

  22. Flyback Converter Design Outline • Schematic Circuit Design • Voltage Regulation Part • Power Stage Primary Part • Power Stage Transformer Part • Power Stage Secondary Part • Controller and Feedback Part • Printed Circuit Board Design • Layout Consideration • Hardware Fabrication • Transformer Winding & Test • Soldering & Test Procedure • Verification Results • Problems & Discussion

  23. Debug of Board • Problem: • Snubber circuit design is not good Bigger snubber cap causes the gate signal unstable Smaller snubber cap causes big spikes • The snubber design and based on the prelimary one and some iterations • The final snubber design is R = ?? C = ??

  24. Debug of Board Gate Drive • Trying to minimize the gate drive loop to reduce the parasitics. • Take off the diode to reduce the turn-off speed to alleviate the turn off spike. • Tune up the gate resistor to reduce switching speed • The final gate resistor is R = 20 Ohmes

  25. Debug of Board

  26. Light Load Open-Loop Results Test Condition: Input: 20V Output: 4.88V Output Power: 1W Vo Vds

  27. Full Load Open-Loop Results Test Condition: Input: 20V Output: 5.2V Output Power: 20W Vo Vds

  28. Small signal TF measurement Zo Gvd

  29. Control to Output TF Magnitude Phase

  30. Output Impedance Magnitude Phase

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