EE 241 Design Problem

Paguio, CindySandoval, Andrew

Valdez, Rozelle

Typical Lab Supply Single Output Flyback converter in DCM Vi = universal supply (85V to 264V) Io = 0 to 3A Vo = 2V to 20V

Specifications

Block Diagram

Linear Regulator

Flyback Converter Assumptions:

◦ Efficiency = 80%◦ fs = 175kHz◦ Iout = 5A

Design Approach◦ 5 Outputs (4.3V, 8.3V, 12.3V, 16.3V, 20.3V)

Tap Configuration◦ 15V Primary Auxiliary Output

To power PWM Controller◦ 24V Secondary Auxiliary Output

To power op-amps in linear regulator and the flyback switcher

Flyback Transformer Design Primary Side:

◦ Core: E14-3C90◦ Ie = 78.6mm, Ae = 97.1mm^2, Ue =67

N = 26.68 turns

Secondary Side:

15V flyback auxiliary output: Nsec = 3.48 turns24V flyback auxiliary output: Nsec = 4.93 turns

(1)

(2)

Flyback Transformer Secondary Side:

◦ Multi-output tap configuration◦ Outputs are in 4V increments (4.3V, 8.3V, 12.3V,

16.3V, 20.3V)◦ Eq. 2 is used to get Nsec for Vout = 4.3V

◦ Nsec(4.3V) = 0.998 turns◦ Nsec(4V) = 0.938 turns◦ Nsec(8.3V) = Nsec(4.3V) + Nsec(4V)◦ Nsec(12.3V) = Nsec(4.3V) + 2*Nsec(4V)◦ Nsec(16.3V) = Nsec(4.3V) + 3*Nsec(4V)◦ Nsec(20.3V) = Nsec(4.3V) + 4*Nsec(4V)

Flyback Transformer

PWM Controller Circuit and Switch:◦ Osc pin:

fs = 175kHz, 1.8/RC, R >= 5kHz R1 = 5kohms, C4 = 2nF

◦ Sense pin: Pout = Vout,max*Iout,max = 20.3*5A=101.5W I_peak = (5.5*Pout)/Vin,min =

(5.5*101.5)/(85*sqrt(2)) = 4.64A Rsense = 1.0/I_peak = 1.0/4.64 = 215mΩ

Flyback Transformer

Flyback (PWM Controller)

Flyback (Simulation Circuit)

Flyback (Output Simulation) Conditions: Vin = 85Vrms

Flyback (Output Simulation) Conditions: Vin = 264Vrms

Flyback (Simulation) Conditions: Vin = 85Vrms Operation is in DCM

Flyback (Simulation) Conditions: Vin = 264Vrms Operation is in DCM

Vaux2

10k

R21

Vaux2

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R20

Vaux2

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Vaux2

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V3

V5V4

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V5

D6D5

D4D3D2D1

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Vaux2

R7 V4Q4

R8

Vaux2

R5 V3Q3

R6

Vaux2

R3 V2Q2

R4

Vaux2

R1 V1Q1

R2

VsetVaux2

X5

LM393X4

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LM393

Vaux2

Vaux2

Vaux2

Vset

Vset

Vset

Vtl431

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Vaux2

Switching Circuit

Switching Circuit

Vf b5

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Vf b2

Vf b1

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R27

Vf ly back2

Vf ly back1 4.3

Vf ly back1

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Vf ly back2

4

Vf ly back3

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Vf ly back4

4

Vf ly back5

Vf ly back3

Vf ly back4

Vf ly back5

1.8k

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Switching Circuit

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R22

Vselect

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Vf ly back1

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Vselect

Switching Circuit

Switching Circuit

Vf b1

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Vf b5

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R33

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Vf b