llc resonant half bridge converter design consideration
TRANSCRIPT
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www.fairchildsemi.com
LLC Resonant Half Bridge Converter
Design Consideration
Marco Farneti
Field Application Engineer
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Agenda
1. Introduction
1. What is soft switching ?2. Soft Switching Operation
2. Resonant Converter Overview
1. Limitation of conventional resonant converter2. LLC Resonant Converter Overview
3. Integrated Transformer
3. LLC Resonant Converter Operation Mode
4. FSFR series Half-Bridge Resonant Converter and design Application1. Features of FSFR series
2. Application circuit for FSFR series
3. 3KW PSU Application - Block Diagram
4. 350W PSU Application - Block Diagram
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1. Introduction
Growing demand for higher power
density and low profile in power
converter has forced to increase
switching frequency
However, Switching Loss has been
an obstacle to high frequency
operation
Capacitive loss Reverse recovery lossOverlap of voltage and current
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1.1 What is soft switching ?
Hard switching Overlap of voltage and current
Capacitive loss
Reverse recovery loss
Zero-voltage-switching (ZVS)
Turn on while switch voltage (Vds) is
zero by flowing current through the
anti parallel diode
Id
Vds
v, i
Psw
t on t off
t
t
on off
Vds
id
Vg
t
t
t
ids
Vg
V ds
I
VTurn-off
Turn-on
Hard-Switching mode
Soft-switching mode
ZVS
ZCS
[ The ideal zero-voltage soft switching ]
[ Switch voltage, current and power loss under hard switching ]
[ Switching loss of a switch during switching interval ]
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1.2 Soft Switching Operation
Resonant converter: processes power in a sinusoidal manner and
the switching devices are softly commutated
Voltage across the switch drops to zero before switch turns on (ZVS)
• Remove overlap area between V and I when turning on
• Capacitive loss is eliminated
Series resonant converter / Parallel resonant converter
Q2
Q1
Resonant
Circuit
VDS
IDS
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2. Resonant Converter Overview
+
VO
-
Ro
Q1
Q2
n:1I
p
Lr
Lm
Cr
Ids2
Vd
Vin
resonant network
Series Resonant (SR) converter
The resonant inductor (Lr) and resonant capacitor (Cr) are in series
The resonant capacitor is in series with the load
The resonant tank and the load act as a voltage divider DC gain is always
lower than 1 (maximum gain happens at the resonant frequency)
The impedance of resonant tank can be changed by varying the frequency of
driving voltage (Vd)
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2. Resonant Converter Overview
+
VO
-
Ro
Q1
Q2
n:1I
p
Llkp
Cr
Ids2
Vd
Vin
resonant network
Parallel Resonant (PR) converter
The resonant inductor (Lr) and resonant capacitor (Cr) are in series
The resonant capacitor is in parallel with the load
The impedance of resonant tank can be changed by varying the
frequency of driving voltage (Vd)
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2.1 Limitation of SRC and PRC resonant
Limitation of the conventional SRC(Series Resonant Converter) Can optimize performance at one operating point, but not with wide range of input voltage
and load variations (too wide frequency range)
Difficult to regulate the output at light or no load condition
Limitation of the conventional PRC(Parallel Resonant Converter) Large amount of circulating current because the load is connected in parallel with the
resonant network,
Difficult to apply in high power applications.
v IN
Q1
Q2
D1
D2
Vout+
-RLOADCr Lr
Co
Np:Ns
I ds1
Ids2
ID
Ir
+
-
+
-
Vds1
Vds2
Iout+-
v IN
Q1
Q2
D1
D2
Vout+
-RLOADCr Lr
Co
Np:Ns
I ds1
Ids2
ID
Ir
+
-
+
-
Vds1
Vds2
Iout+-
Cr
Half-bridge series resonant (SR) converter Half-bridge parallel resonant (PR) converter
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2.2 LLC Resonant Converter Overview
LLC resonant converter Topology looks almost same as the conventional LC series
resonant converter
Magnetizing inductance (Lm) of the transformer is relatively small and involved in the resonance operation
Voltage gain is different from that of LC series resonant converter
+
VO
-
Ro
Q1
Q2
n:1I
p
Lr
Lm
Cr
Ids2
Vd
Im
ID
Vin
resonant network
Io
+
VO
-
Ro
Q1
Q2
n:1I
p
Lr
Lm
Cr
Ids2
Vd
Vin
resonant network
LC Series resonant converter LLC resonant converter
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2.2 LLC Resonant Converter Overview
Features of LLC resonant converter
- Reduced switching loss through ZVS: Improved efficiency
- Narrow frequency variation range over wide load range
- Zero voltage switching even at no load condition
- Typically, integrated transformer is used instead of discrete magnetic
components
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2.2 LLC Resonant Converter Overview
Advantages
Reduced switching loss through ZVS Improved efficiency and EMI
Reduced magnetic components size by high frequency operation
Narrow frequency variation range over wide load range
Drawbacks
Larger circulating current compared to LC resonant converter due to the relatively small magnetizing inductance
Difficult to optimize transformer design
LLC Resonant converter
v IN
Q1
Q2
D1
D2
Vout+
-RLOADCr Lr
Co
Lm
Np:Ns
I ds1
Ids2
ID
Im
Ir
+
-
+
-
Vds1
Vds2
Iout+- Half-bridge LLC resonant converter
//m ac acj L R R
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2.3 Integrated Transformer
Integrated transformer in LLC resonant converter
Two magnetic components are implemented with a single core (use
the primary side leakage inductance as a resonant inductor)
One magnetic components (Lr) can be saved
Leakage inductance not only exists in the primary side but also in
the secondary side
Need to consider the leakage inductance in the secondary side
+
VO
-
Ro
Q1
Q2
n:1
Lr
Lm
Cr
Ids2
Vd
ID
Vin
Io
+
VO
-
Ro
Q1
Q2
n:1I
p
Llkp
Lm
Cr
Ids2
Vd
Llks
Im
ID
Vin
Integrated transformer
Io
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3. LLC Resonant Converter Operation mode
Below resonance (fs<fo)
Larger circulating current
Soft commutation of
rectifier diode
Above resonance (fs>fo) Smaller circulating current
Hard commutation of rectifier diode
Ip
Im
IO
ID
(I) fs < f
o Ip
ID I
O
Im
(II) fs > f
o
fo
fs
Gain (M)Below resonance
(fs<f
o)
above resonance
(fs>f
o)
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1) T1) T00~T~T11
3.1 Operation mode
LLC resonant HB converter
IN
Q1
Q2
D1
D2
Vout
+
-RLOADCr Lr
Co
Lm
Np:Ns
I ds1
Ids2
Im
Ir
+
-
+
-
Vds1
Vds2
- + ID
-+
t
t
t
t
t
t
t
t
t
VIN
On
Dead time
T0 T1 T2 3T 4T
C rmaxV
VC rmin
VCR
Vgs1
Vgs2
Vds1
Vds2
Ids1
Ir, Im
VCr
Iout
Ir
Im
IL rpeak
Off
VCOSSQ1
Q1 is ON, Q2 is OFF
D1 is ON, D2 is OFF; V(D2) = -2·Vout
Ir flows through Q1’s body diode ZVS Condition
Lm is charged with constant voltage
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22) T) T11~T~T22
3.2 Operation mode
LLC resonant HB converter
vIN
Q1
Q2
D1
D2
Vout
+
-RLOADCr Lr
Co
Lm
Np:Ns
I ds1
Ids2
Im
Ir
+
-
+
-
Vds1
Vds2
- + ID
-+
Q1 is ON, Q2 is OFF
D1 is ON, D2 is OFF; V(D2) = -2·Vout
Lm is dynamically shorted: V(Lm) = Ns/Np·Vout.
Cr resonates with Lm
Ir flows through Q1’s RDS(on) from Vin to Gound
Energy is taken from Vin and goes to Vout
t
t
t
t
t
t
t
t
VIN
T0 T1 T2 3T 4T
Vgs1
Vgs2
Vds1
Vds2
Ids1
V
Iout
Dead time
Ir, Im
C rmaxV
VC rmin
VC r
Cr
On Off
t
IL rpeakIr
Im
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33) T) T22~T~T33
3.3 Operation mode
LLC resonant HB converter
vIN
Q1
Q2
D1
D2
Vout
+
-RLOADCr Lr
Co
Lm
Np:Ns
I ds1
Ids2
Im
Ir
+
-
+
-
Vds1
Vds2
- + ID
-+
Q1 is ON, Q2 is OFF
D1 and D2 are OFF; V(D1)=V(D2)=0
; transformer’s secondary is open
Ir=Im
t
t
t
t
t
t
t
t
t
VIN
Dead time
T0 T1 T2 T3T 4 T6T 5
C rmaxV
VC rmin
IL rpeak
VCR
Vgs1
Vgs2
Vds1
Vds2
Ids1
Ir, Im
V Cr
Iout
Ir
Im
On Off
VCOSSQ1
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33) T) T33~T~T44
3.4 Operation mode
LLC resonant HB converter
vIN
Q1
Q2
D1
D2
Vout
+
-RLOADCr Lr
Co
Lm
Np:Ns
I ds1
Ids2
Im
Ir
+
-
+
-
Vds1
Vds2
- + ID
-+
Q1 and Q2 are OFF (dead-time)
D1 and D2 are OFF; V(D1)=V(D2)=0
; transformer’s secondary is open
I(Lr+Lm) charges Coss of Q1 and discharges Coss of Q2,
until V(Coss of Q2)=0
; Q2’s body diode starts conducting
Output energy comes from Co
Phase ends when Q2 is switched on
t
t
t
t
t
t
t
t
t
VIN
Dead time
T0 T1 T2 T3T 4 T6T 5
C rmaxV
VC rmin
IL rpeak
VCR
Vgs1
Vgs2
Vds1
Vds2
Ids1
Ir, Im
V Cr
Iout
Ir
Im
On Off
VCOSSQ1
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4. FSFR series HB Resonant Converter
PWM / PFM Controller + High side Drive IC + 2 MOSFET
in 9-SIP PKG
Universal controller : can be applied various topology
High-side drive IC : has immunity against switching noise
MOSFET with fast recovery body diode trr = 120ns
PWM IC
HV IC
2 MOSFET
Advantage through system integration
• High reliability & productivity
• BOM cost reduction
• Easy design
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4.1 Features of FSFR series
Variable frequency control with 50% duty cycle for half-bridge resonant converter topology
High efficiency through zero voltage switching (ZVS) : typ. Eff=93~94% for Vo=24V
Internal MOSFETs with Fast Recovery Type Body Diode (trr=120ns)
Internally optimized dead time (fixed. 350ns)
Up to 300kHz operating frequency
Pulse skipping for Frequency limit (programmable) at light load condition
Simple remote ON/OFF control
Various Protection functions: Over Voltage Protection (OVP), Over Current Protection
(OCP), Abnormal Over Current Protection (AOCP), Internal Thermal Shutdown (TSD)
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4.2 Application circuit for FSFR series
Control
IC
C105
22uF/
50V
Vcc
VDLLVcc
RT
CON
CS
SG PG
VCTR
HVcc
Ns
VoNp Ns
C101
220uF/
450V
R104
7.2k
R105
7.2kC107
6.8uF
R107
3.9k
JP1
10
R106
270
D101
1N4137
C102
22nF/
630V
D211
FYP2010DN
D212
FYP2010DN
C106
150nF
U3
KA431 C203
47nF
R203
33k
R205
7k
R204
62k
R202
1k
R201
10k
C201
2200uF
35V
C202
2200uF
35V
R101
0.2Ω
R102
1kΩ
C102
100pF
C108
12nF
R206
2k
C204
12nF
Vin=400Vdc
LLC resonant converter for LCD TV
Vin=350~400V, Vo=25V, Io=8A (200W)
Eff=94% at full load
No heat sink is required up to 200W
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4.3 3KW PSU Application - Block Diagram
P F CRectifier
2SK3235(HITACHI)*6EAKSU20B60(Nihon Inter)*2EA
D25XB60 (600V 25A)SHINDENGEN*2EA
PFC IC
TK83854(TOKO)PFC controller
FQAF24N50(FAIRCHILD)*6EA
Output
42V_66A
Input
100-240Vac
switching regulator
CXA8038A(SONY)Resonant mode
DC-DC Converter
KCF25A20(Nihon Inter)*6EA
2SK3313(TOSHIBA)*2EA
switching regulator
CXA8038A(SONY)Resonant mode
DC-DC Converter
FCH30A06(Nihon Inter)*2EA
Output
12V_12A
KCQ60A06(Nihon Inter)*3EA
FCH30A03L(Nihon Inter)*1EA
Synchronous Buck Converter
Output
3.3V_25A
2SK3573(NEC)*1EASI4894(VISHAY)*10EA
Controller
PU5103(TI)Synchronous DC/DC
LLC Resonant HBLLC Resonant HB
LLC Resonant HBLLC Resonant HB
CCM PFCCCM PFC
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4.4 350W PSU Application - Block Diagram
Rectifier
Input
100-240Vac
FQPF13N50CF(FSC)*2EA
switching regulator
CXA8038A(SONY)
Resonant mode
DC-DC Converter
IPP06CN10N(Infineon)*2EA
Output
12V_32A
P F C
PFC IC
UC3854DW
SPA21N60C3_Infineon*1EA
STTH15R 06FP_ST*1EA
Synchronous Rectification
MIP2G4(Panasonic)*1EA
Flyback
converter
5V 3A STB
FCH10A15(Nihon Inter)*1EA
DCM PFCDCM PFC
LLC Resonant HBLLC Resonant HB
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