paguio, cindy sandoval, andrew valdez, rozelle. typical lab supply single output flyback...
TRANSCRIPT
Typical Lab Supply Single Output Flyback converter in DCM Vi = universal supply (85V to 264V) Io = 0 to 3A Vo = 2V to 20V
Specifications
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
Vaux2
10k
R21
Vaux2
10k
R20
Vaux2
10k
R19
Vaux2
10k
R18
10k
R17
V3
V5V4
V5
V5
D6D5
D4D3D2D1
Vaux2
R9 V5Q9
R10
Vaux2
R7 V4Q4
R8
Vaux2
R5 V3Q3
R6
Vaux2
R3 V2Q2
R4
Vaux2
R1 V1Q1
R2
VsetVaux2
X5
LM393X4
LM393X3
LM393
X6
LM393
Vaux2
Vaux2
Vaux2
Vset
Vset
Vset
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R11
8k
R12
8k
R13
8k
R14
8k
R15
D7D8
D9D10D11
D12D13
V4
V4V5
V3
V2
Vaux2
Switching Circuit
Vf b5
Vf b4
Vf b3
Vf b2
Vf b1
9.8k
R27
Vf ly back2
Vf ly back1 4.3
Vf ly back1
4
Vf ly back2
4
Vf ly back3
4
Vf ly back4
4
Vf ly back5
Vf ly back3
Vf ly back4
Vf ly back5
1.8k
R23
5.8k
R25
13.8k
R29
17.8k
R31
Switching Circuit
1K
R22
Vselect
Vaux2
Vaux2
Vaux2
Vaux2
Vaux2V5
V4
V1
S5
S4
S3
S1
S2
V2
V3
Vf ly back2
Vf ly back1
Vf ly back3
Vf ly back4
Vf ly back5
Vselect