Synchronous Buck Converter using LTspice

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

All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 1

Synchronous-Buck Converter Circuit


Duty Cycle (D)

≈ Vin/Vout,

D = 0.368

Test Setup


Test Circuit

Power Supply:

VCC 12VVIN 5V

Measurement Waveform

Test Circuit Schematic


Synchronous-Buck Converter using TPS5618 controller from Texas Instruments

Test Circuit (Breadboard)


Controller

Q1

Q2

Test Circuit (Top View)


L1

C9

C10

Controller

Synchronous-Buck Controller (1/2)

Synchronous-Buck Controller Circuit with IC

TPS5618 from Texas Instruments

Synchronous-Buck Controller Block Model

(Open Loop Setting)

• 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.


HIDR

LODR

High side gate driver

Low side gate driver

Synchronous-Buck Controller (2/2)

V1

TD = {1/FREQ}

TF = 1n

PW = {D/FREQ}PER = {1/FREQ}

V1 = 0

TR = 1n

V2 = 1.709

PARAMETERS:

FREQ = 152kHz

D = 0.36

tdly = 80n

0

Rdly 1

1k

N4

CHDR

1nCdly 1

{tdly /1k}

00

Rdly 2

1k

N3

0

Cdly 2

{tdly /1k}

HDR

LDR

N1

U1AND2_ABM

VOH = 12VOL = 0

DclmpDHDR1

U2AND2_ABM

VOH = 8VOL = 0

N2

N5

Dclmp

DHDR2

N7

RHDR10.01

U5INV_ABM

VOH = 1.709VOL = 0

RHDR20.01

N6


Pulse

Control

Signal

Dead-time

generator

The Syn-Buck_Ctrl Equivalent Circuit

Parameters

• FREQ = Switching frequency, set to match

the measurement switching frequency.

• D = Duty Cycle, calculated by D≈VOUT/VIN

• tdly = HDR and LDR dead-time, the tdly is

set to match the measurement dead time

value.

Gate drive signal (measurement)

1/frequency

Dead-time, the time

when QH and QL

are both off

MOSFET: TPC8014 (1/2)


TPC8014 LTSpice Symbol

Device mounted on an epoxy board

*$

*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

R_R8 8 6 0.01m

.ENDS

*$

MOSFET: TPC8014 (2/2)

*$

.SUBCKT MTPC8014_p D G S

CGD 1 G 1.7n

R1 1 G 10MEG

S1 1 D G D SMOD1

D1 2 D DGD

R2 D 2 10MEG

S2 2 G D G SMOD1

M1 D G S S MTPC8014

.MODEL SMOD1 VSWITCH

+ VON=0V VOFF=-10mV RON=1m ROFF=1E12

.MODEL DGD D (CJO=0.950E-9 M=.52396 VJ=.54785)

.MODEL MTPC8014 NMOS

+ LEVEL=3 L=720.00E-9 W=.45 KP=66.000E-6 RS=1.0000E-3

+ RD=6.8436E-3 VTO=2.3063 RDS=3.0000E6 TOX=40.000E-9

+ CGSO=2.7726E-9 CGDO=1E-12 RG=22.95

+ CBD=342.86E-12 MJ=.70573 PB=.3905

+ RB=1 N=5 IS=1E-15 GAMMA=0 KAPPA=0 ETA=0.5m

.ENDS

*$

*$

.SUBCKT DTPC8014_p A K

R_R2 5 6 100

R_R1 3 4 1

C_C1 5 6 195p

E_E1 5 K 3 4 1

S_S1 6 K 4 K _S1

RS_S1 4 K 1G

.MODEL _S1 VSWITCH

+ Roff=50MEG Ron=100m Voff=90mV Von=100mV

G_G1 K A VALUE { V(3,4)-V(5,6) }

D_D1 2 K DTPC8014

D_D2 4 K DTPC8014

F_F1 K 3 VF_F1 1

VF_F1 A 2 0V

.MODEL DTPC8014 D

+ 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

.ENDS

*$

.subckt DZTPC8014 1 2

D2 1 3 DZ2

D1 2 3 DZ1

.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

*$


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

*$


LTSpice Symbol

Würth Elektronik Inductor part no. 7447140

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

*$


LTSpice Symbol

Capacitor 820uF (25V)

Switching Waveform

Measurement Simulation


V(Vout)

I(L1)

VDS(Q1)

V(Vout)

I(L1)

VDS(Q1)

High Side MOSFET(QH): VGS, VDS, ID



ID(Q1)

VDS(Q1)

VGS(Q1)

ID(Q1)

VDS(Q1)

VGS(Q1)

Low Side MOSFET(QL): VGS, VDS, ID



ID(Q2)

VDS(Q2)

VGS(Q2)

ID(Q2)

VDS(Q2)

VGS(Q2)

Gate Drive Signal



VGS(Q2)

VGS(Q1)

VGS(Q2)

VGS(Q1)

VIN – VOUT



VOUT

VIN

VOUT

VIN

VOUT,RIPPLE



VOUT,RIPPLE VOUT,RIPPLE

Output Inductor Voltage and Current



V(L)

I(L)

V(L)

I(L)

Synchronous Buck Converter using LTspice

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