Synchronous Buck Converter using LTspice

1. Synchronous-Buck Converter Circuit
• Synchronous-Buck Converter Circuit
• Test Setup
• Test Circuit
• Synchronous-Buck Controller
• MOSFET: TPC8014
• Inductor L1: Würth Elektronik Inductor
• Capacitor C9: 820uF (25V)
• Switching Waveform
• High Side MOSFET(QH): VGS, VDS, ID
• Low Side MOSFET(QL): VGS, VDS, ID
• Gate Drive Signal
• VIN-VOUT
• VOUT,RIPPLE
• Output Inductor Voltage and Current
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2. Synchronous-Buck Converter Circuit
Duty Cycle (D)
≈ Vin/Vout,
D = 0.368
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3. Test Setup
Power Supply:
Measurement Waveform VCC 12V
VIN 5V
Test Circuit
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4. Test Circuit Schematic
Synchronous-Buck Converter using TPS5618 controller from Texas Instruments
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5. Test Circuit (Breadboard)
Q1
Q2
Controller
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6. Test Circuit (Top View)
L1
C9
C10
Controller
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7. Synchronous-Buck Controller (1/2)
Synchronous-Buck Controller Circuit with IC Synchronous-Buck Controller Block Model
TPS5618 from Texas Instruments (Open Loop Setting)
HIDR
High side gate driver
Low side gate driver
LODR
• The Syn-Buck_Ctrl is a block model that generates gate drive pulse signal to control MOSFET
switches of the Synchronous-Buck Converter. The duty cycle, switching frequency, and the
switching dead-time are input into the model to match the real circuit.
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8. Synchronous-Buck Controller (2/2)
Parameters
• FREQ = Switching frequency, set to match
the measurement switching frequency.
PARAMETERS: • D = Duty Cycle, calculated by D≈VOUT/VIN
•
FREQ = 152kHz
D = 0.36
DHDR1 RHDR1 tdly = HDR and LDR dead-time, the tdly is
U1 Dclmp 0.01
tdly = 80n AND2_ABM N7 set to match the measurement dead time
Rdly 1
N4
N5 N6
HDR value.
Dclmp RHDR2 CHDR Dead-time, the time
1k
Cdly 1 VOH = 12 DHDR2 0.01 1n when QH and QL
Pulse {tdly /1k} VOL = 0
0 are both off
Control 0
Signal 1/frequency
U5 U2
INV_ABM AND2_ABM
N1 N2
Rdly 2
N3 LDR
VOH = 1.709
VOL = 0
1k
V1 Cdly 2 VOH = 8
{tdly /1k} VOL = 0
TD = {1/FREQ}
TR = 1n 0
TF = 1n Dead-time
0 V1 = 0
V2 = 1.709 generator
PW = {D/FREQ}
PER = {1/FREQ}
The Syn-Buck_Ctrl Equivalent Circuit
Gate drive signal (measurement)
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9. MOSFET: TPC8014 (1/2)
*$
*PART NUMBER: TPC8014
*MANUFACTURER: TOSHIBA
*VDSS=30V, ID=11A
*All Rights Reserved Copyright (c) Bee Technologies Inc. 2011
.SUBCKT TPC8014 1 2 3 4 5 6 7 8
X_U1 6 4 3 MTPC8014_p
X_U2 4 3 DZTPC8014
X_U3 3 6 DTPC8014_p
R_R1 1 3 0.01m
R_R2 2 3 0.01m
R_R5 5 6 0.01m
R_R7 7 6 0.01m
Device mounted on an epoxy board R_R8 8 6 0.01m
.ENDS
*$
TPC8014 LTSpice Symbol
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10. MOSFET: TPC8014 (2/2)
*$ *$
.SUBCKT DTPC8014_p A K
.SUBCKT MTPC8014_p D G S
R_R2 5 6 100
CGD 1 G 1.7n R_R1 3 4 1
R1 1 G 10MEG C_C1 5 6 195p
S1 1 D G D SMOD1 E_E1 5 K 3 4 1
S_S1 6 K 4 K _S1
D1 2 D DGD
RS_S1 4 K 1G
R2 D 2 10MEG .MODEL _S1 VSWITCH
S2 2 G D G SMOD1 + Roff=50MEG Ron=100m Voff=90mV Von=100mV
M1 D G S S MTPC8014 G_G1 K A VALUE { V(3,4)-V(5,6) }
D_D1 2 K DTPC8014
.MODEL SMOD1 VSWITCH
D_D2 4 K DTPC8014
+ VON=0V VOFF=-10mV RON=1m ROFF=1E12 F_F1 K 3 VF_F1 1
.MODEL DGD D (CJO=0.950E-9 M=.52396 VJ=.54785) VF_F1 A 2 0V
.MODEL MTPC8014 NMOS .MODEL DTPC8014 D
+ LEVEL=3 L=720.00E-9 W=.45 KP=66.000E-6 RS=1.0000E-3 + IS=824.87E-12 N=1.2770 RS=6.2420E-3 IKF=7.3139
+ CJO=3.0000E-12 BV=60 IBV=100.00E-6 TT=24.062E-9
+ RD=6.8436E-3 VTO=2.3063 RDS=3.0000E6 TOX=40.000E-9 .ENDS
+ CGSO=2.7726E-9 CGDO=1E-12 RG=22.95 *$
+ CBD=342.86E-12 MJ=.70573 PB=.3905 .subckt DZTPC8014 1 2
+ RB=1 N=5 IS=1E-15 GAMMA=0 KAPPA=0 ETA=0.5m D2 1 3 DZ2
D1 2 3 DZ1
.ENDS
.model DZ1 D
*$ + IS=0.01p N=0.1 ISR=0
+ CJO=3E-12 BV=22.423 IBV=0.001 RS=0
.model DZ2 D
+ IS=0.01p N=0.1 ISR=0
+ CJO=3E-12 BV=22.423 IBV=0.001 RS=411.11
.ENDS
*$
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11. Inductor L1: Würth Elektronik Inductor
*$
*PART NUMBER: L7447140
*MANUFACTURER: Würth Elektronik
*All Rights Reserved Copyright (c) Bee Technologies Inc. 2011
.SUBCKT L7447140 1 2
R_RS 1 N1 10.366m
L_L1 N1 2 4.84796uH
C_C1 N1 2 0.357pF
R_R1 N1 2 15.3375k
.ENDS
*$
Würth Elektronik Inductor part no. 7447140
LTSpice Symbol
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12. Capacitor C9: 820uF (25V)
*$
*PART NUMBER: EEUFM1E821L
*MANUFACTURER: Panasonic
*CAP=820uF, Vmax=25V
*All Rights Reserved Copyright (C) Bee Technologies Inc. 2011
.SUBCKT C820U 1 2
L_L1 1 N1 8.16935nH
C_C1 N1 N2 812.73uF
R_R1 N2 2 15.695m
.ENDS
*$
Capacitor 820uF (25V)
LTSpice Symbol
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13. Switching Waveform
Measurement Simulation
VDS(Q1) VDS(Q1)
I(L1)
I(L1)
V(Vout)
V(Vout)
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14. High Side MOSFET(QH): VGS, VDS, ID
Measurement Simulation
VGS(Q1) VGS(Q1)
VDS(Q1)
VDS(Q1)
ID(Q1) ID(Q1)
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15. Low Side MOSFET(QL): VGS, VDS, ID
Measurement Simulation
VGS(Q2) VGS(Q2)
VDS(Q2)
VDS(Q2)
ID(Q2) ID(Q2)
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16. Gate Drive Signal
Measurement Simulation
VGS(Q1) VGS(Q1)
VGS(Q2) VGS(Q2)
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17. VIN – VOUT
Measurement Simulation
VIN VIN
VOUT VOUT
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18. VOUT,RIPPLE
Measurement Simulation
VOUT,RIPPLE VOUT,RIPPLE
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19. Output Inductor Voltage and Current
Measurement Simulation
V(L)
V(L)
I(L)
I(L)
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