Ece 4284 flyback converter design
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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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ECE 4284Flyback 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: 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


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


Schematic Circuit Design

Flyback Circuit Sketch


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


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


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


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


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


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


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


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


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


Schematic Circuit Design: Feedback Loop

  • Application: Closed-loop Compensator

  • List of RC parameters


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


Printed Circuit Board Design


Printed Circuit Board Design


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


Hardware Fabrication


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


Verification Results


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


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 = ??


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


Debug of Board


Light Load Open-Loop Results

Test Condition:

Input: 20V

Output: 4.88V

Output Power: 1W

Vo

Vds


Full Load Open-Loop Results

Test Condition:

Input: 20V

Output: 5.2V

Output Power: 20W

Vo

Vds


Small signal TF measurement

Zo

Gvd


Control to Output TF

Magnitude

Phase


Output Impedance

Magnitude

Phase


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