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Dual Switch Flyback Converter Solution:
The Ideal Solution for 75~200W Power Supplies
>90% Efficiency and Meets 2013 ErP: < 0.5W @ 0.25W load
www.fairchildsemi.com1
Agenda
• Challenges for designing 75~200W power supplies
• Fairchild’s Dual Switch Flyback Solution
• Topology Comparison
• Evaluation Boards Test Results
• Ideal Solution for Both Efficiency and Standby Power
www.fairchildsemi.com2
• Ideal Solution for Both Efficiency and Standby Power
Consumption
Challenges in Designing
Switching Power Supplies
Low Standby Power Consumption
High Efficiency
High Power Density
www.fairchildsemi.com3
High Power Density
High Reliability
Low Cost
Existing Single Flyback Converter Solution –
Does Not Meet All Design Challenges
Low Standby Power Consumption
High Efficiency
High Power Density
• Poor Efficiency, difficult
to achieve > 90%
• Low Power Density
www.fairchildsemi.com4
High Power Density
High Reliability
Low Cost
• Low Power Density
Existing LLC Converter Solution –
Does Not Meet All Design Challenges
Low Standby Power Consumption
High Efficiency
High Power Density
• Does not meet 2013 ErP
Lot 6 (<[email protected])
without auxiliary power
www.fairchildsemi.com5
High Power Density
High Reliability
Low Cost
• Sensitivity to the
transformer tolerance and
gate drive timing.
Single Flyback
- Poor efficiency
- Good standby power
What If you had a solution that met all of
your design challenges...
What if you had…
- Good efficiency
- Excellent standby power
performance
LLC Resonant
- Excellent heavy load
efficiency
- Poor medium and light load
efficiency
- Poor standby power
consumption
www.fairchildsemi.com6
Introducing the
Dual Switch Flyback Solution (75~200W)
www.fairchildsemi.com7
FAN6920: BCM PFC +
QR PWM Combo
FAN7382: H/L Driver
FAN6204: SR Controller
Key Features –
Dual Switch QR Flyback Converter
Low Standby Power Consumption
• Meet 2013 ErP Lot 6
• PIN<0.5W @230Vac with PO=0.25W)
• PIN<0.25W@ 230Vac with no load
High Efficiency
• Leakage inductance energy is recycled to the input and snubber circuitry is not required
• 500V MOSFETs can be used in the primary side
• Low switching loss with valley switching in the primary side
• Lower voltage stress on the secondary side rectifier
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• Lower voltage stress on the secondary side rectifier
• Variable PFC output voltage technique can be used to improve low line efficiency of the
entire system
Easy Design
• Same as well known conventional Flyback converter design
• Easy transformer mass production
• Ultra low profile transformer can be used without concern of leakage inductance
Low EMI
• Drain voltage overshoot is clamped to input voltage
• Valley switching
Basic Operation of Dual Switch Flyback
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Phase 1: Q1&Q2 On
Phase 2: Q1&Q2 Off, D1, D2 on
Phase 3&4: Q1&Q2 off,
D1&D2 off
Vo
+
-
Vin
+
-
iLk
iLmnVo
-
+
+
Vds-low
-
+
Vds-high
-
Dual Switch Flyback Benefits –
Improvement in Energy Loss
• No snubber loss or heat problem
• Leakage inductance energy is
recycled into bulk capacitor
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Single Flyback
Dual Flyback
iLK
iDS
Dual Switch Flyback Benefits –
High Reliability and Low Switching Loss
Vds
VDS max = VIN + n*VO + Spike VDS max= VIN
• Low MOSFET Drain Source Voltage Good reliability
• Allow large n design Near ZVS Switching Low switching loss
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VIN
Vo×
Vo× n
n
VDS of Single Flyback VDS of Dual Flyback Larger switching
loss
Near ZVS
Switching
Dual Switch Flyback Benefits –
Reduction in Secondary-Side Conduction Loss
• Benefit of high turn ration n to SR MOSFET
• VDS of SR MOSFET is : VIN/n + VOUT
• Large n Lower VDS Lower MOSFET Ron
in lower price cost & efficiency
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Example:
VIN = 420V, Vo = 12V, n= 12
VDS = 420V/12 + 12V = 47V
Could choose 60V or 75V SR MOSFET
Dual Switch Flyback Benefits –
Improvement in Low Line Efficiency
• Two Level PFC output to improve low line efficiency
www.fairchildsemi.com13
PFC stage efficiency with different PFC output
voltages at 115VAC
Dual Switch Flyback Benefits –
Improved Light Load Efficiency
• Deep extended Valley switching ( up to 12th valley) to allow low operating
frequency in light load Improved light load efficiency
Load ↓ Freq↑ Poor light load
efficiency
Freq. nearly
constant
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First valley detect
5th valley detect
12th valley detect
QR Operation without extended valley switch Other IC: QR Operation with extended valley ( up to 4th valley)
FAN6920 Deep extended valley switch
Dual Switch Flyback Benefits –
Achieves Low Standby Power Consumption
• Dual Switch Flyback Meets < 0.5W @ 0.25W ( 2013 ErP)
• PFC Stage:
• High line/light load Turn off PFC
• Low line/light load burst mode
• QR Stage:
• enter into burst mode when light load
• No snubber loss
www.fairchildsemi.com15
• No snubber loss
• SR Stage:
• Turn off SR when light load
Voltage
VAC PO= 0W PO=0.25W
115V 0.186W 0.482W
230V 0.195W 0.486W
Load
Standby Power Consumption
Dual Switch Flyback Single Flyback
- Easy design
- Poor Efficiency
- Good standby power
A topology that meets all of your design
challenges...
VDD
RES
AGNDGND
LPC
VOUT
Lm
IDS ISR
R1
R2 R4
R3
n:1
GATE
8
3 5
7
64
Q2
Q1
IDS
Q1
FAN7382FAN6920
FAN6204
LLC Resonant
- Complicated design
-Excellent heavy load
efficiency
- Poor medium and light load
efficiency
- Poor standby power
consumption
www.fairchildsemi.com16
- Ideal for 75~200W
- Easy Design
- Good Efficiency with OFF
time modulation
- Excellent standby power
performance with burst
operation
consumption
Dual Switch QR Flyback Converter vs.
Single SwitchSingle Switch QR Flyback- RCD snubber is required to dissipate leakage
inductance energy
- When reflected output voltage (VO×Np/Ns) is larger
than input voltage, ZVS is achieved
- High voltage MOSFET is required (700~800V)
Dual Switch QR Flyback- Leakage inductance energy is recycled to input
- If the reflected output voltage (VO×Np/Ns) is larger than
the input voltage, energy is not transferred to the output
(ZVS is not allowed)
- 500V MOSFETs can be used
www.fairchildsemi.com17
Lower clamping
voltage requires more
loss in RCD snubber
VDS is clamped
to VIN without
lossTDTON
TS
VINVo×Np/Ns
IDS
VDS
Vo×Np/Ns
ID×NS/NP
Dual-Switch QR Flyback vs.
LLC resonant ConverterDual Switch QR Flyback
- Primary side current reduces as load decreases
- Near ZVS (Valley switching)
- Simple transformer design same as conventional
flyback converter
- No shoot through issue
LLC Resonant Converter
- Large circulating current in the primary side
even at light load condition (high standby power
consumption)
- Full ZVS
- Complicated transformer design
- Inherent shoot through issue
Q2+
VO
Ip
Lr
Im
ID
www.fairchildsemi.com18
Q1 IDS1
Vin
-
n:1
LmCr
Ip
IDS1
Im
ID
Light Load Condition
Ip
IDS1
Im
ID
Heavy Load Condition
IDS1
ID
Light Load Condition
VDS1
IDS1
ID
Heavy Load Condition
VDS1
Dual-Switch QR Flyback vs.
LLC Resonant Converter
Dual Switch QR Flyback Converter LLC Resonant Converter
Full load efficiency Good (Valley switching) Best (Full ZVS)
Light load efficiency Good (same as Flyback converter) Poor (Due to the large circulating current)
Applying burst mode operation Easy (same as Flyback converter) Difficult (Due to gain curve characteristics)
Decrease PFC output voltage with line
voltage to improve PFC efficiency
Easy to incorporate due to wider
allowable input voltage range
Difficult to incorporate due to narrow allowable
input voltage range
Synchronous rectification Easy to control Difficult to control
Conventional Current Mode Control VCO based PFM
www.fairchildsemi.com19
Feedback control
Conventional Current Mode Control
- Easy to design compensation network
- Good line / load transient response
VCO based PFM
- Difficult to design compensation network
- Poor line / load transient response
Design Easy (same as Flyback converter) Complicated (Resonant network design)
Transformer Manufacturing Not sensitive to transformer tolerance Very sensitive to transformer tolerance
Reliability
Good
-No concern about shoot-through of
primary side switches
Poor
-Shoot-through of primary side MOSFETs
results in catastrophic failure
- Operation in capacitive region can also
result in MOSFET failure
Power Range Suitable for <200W application Suitable for >200W application
Dual-Switch QR Flyback vs.
LLC Resonant Converter
89.0
90.0
91.0
92.0
93.0
94.0
95.0
96.0
Efficiency (%)
LLC Resonant (VIN=115Vac)
Efficiency Comparison
90W/19V Demo Board
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86.0
87.0
88.0
0 20 40 60 80 100
% Load
Dual Switch QR (VIN=115Vac)
LLC Resonant (VIN=230Vac)
Dual Switch QR (VIN=230Vac)
Table 1 Key Components for Each TopologyFunction LLC Resonant Half-Bridge Converter Dual Switch QR Flyback Converter
PFC MOSFET
PFC Diode
DC-DC MOSFETS
SR MOSFETS 2 FDB045AN08A0 (75V, 4.5mΩ typ.) ×2 FDB031N08 (75V, 2.4mΩ typ.) ×1
FQI13N50 (Rdson=0.39Ω typ.)
ES3J (600V/3A)
FQI13N50 (Rdson=0.39Ω typ.) ×2
Dual Switch Flyback Schematic
www.fairchildsemi.com21
90W/19V Slim Adapter
60mm 95mm
16.5mm
89.37
90.6990.5191.58
90.0890.88
89.0
90.0
91.0
92.0
93.0
94.0
Efficiency (%)
VIN=115Vac
VIN=230Vac
www.fairchildsemi.com22
22.5W 45W 67.5W 90W
115VAC 89.37% 90.69% 90.51% 89.87%
230VAC 91.58% 90.08% 90.88% 91.01%
Input Power @ No Load
VAC(RMS) P
IN(W)
90 0.190
115 0.186
230 0.195
264 0.210
VAC(RMS) PIN(W)
115 0.478
230 0.482
Input Power @ 0.25W
PIN<0.5W
2013 EUP spec.PIN<0.2W@230VAC
88.0
89.0
0 20 40 60 80 100% Load
(Note)18AGW-1.5m cable is included (63mΩ impedance), which
results in 1.41W loss at 100% load.
130W/19V All-In-One PC power
100mm 145mm
Input Power @ no load
92.1592.3291.65
92.15
93.59
90.0
91.0
92.0
93.0
94.0
Efficiency (%)
VIN=115Vac
VIN=230Vac
www.fairchildsemi.com23
Spec: PIN<0.5W 2013 EUP
Input Power @ 0.25W
Efficiency 20%
26W
50%
65W
100%
130W
3 point
AVG.
115Vac/60Hz 89.29% 92.15% 92.32% 91.25%
230Vac /50Hz 91.65% 92.15% 93.59% 92.56%
VAC (RMS) PIN(W)
115 0.478
230 0.482
VAC (RMS) PIN(W)
90 0.19
115 0.186
230 0.195
264 0.21
Input Power @ no load89.29
88.0
89.0
0 20 40 60 80 100% Load
200W/19V All-In-One PC Power
90.01
91.62
90.76
92.16
91.76
92.60
90.0
91.0
92.0
93.0
94.0
Efficiency (%)
VIN=115Vac
VIN=230Vac
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Efficiency 20%
40W
50%
100W
100%
200W
3 point
AVG.
115Vac/60Hz 90.01% 91.62% 90.76% 90.79%
230Vac /50Hz 92.16% 91.76% 92.60% 92.17%
Input Power @ 0.5W
VAC (RMS) PIN(W)
115 0.762
230 0.781
VAC (RMS) PIN(W)
90 0.168
115 0.183
230 0.206
264 0.223
Input Power @ no load Input Power @ 0.25W
VAC (RMS) PIN(W)
115 0.484
230 0.487
90.01
88.0
89.0
0 20 40 60 80 100% Load
Example Circuit (19V/90W)
C40.33μ/450V C50.33μ/450V
+C7
47μ
/450V
1
23
Q4FQI13N50C
2 1
D1ES3J
1
23
Q2FQI13N50C
R104.7M±1%
1
23
Q1
FQI13N50C
21
D4ES1H
21
D2ES1JH
VSPFCVSPWM
R94.7M±1%
AC
AC -
+
BD1
DF08S PFC_VO
R747K
R847K
+ C1533μ/50V2
1
D9RS1D
1
2
CN1
CN/2pin AC inlet
MOV1MOV/U07 470
C1
XC/0.47u/250VL
F1
F/4A/250V
R2
1.5M/1206
R1
1.5M/1206
+
C8820μ/25V VO+
VO+1
VO-1
R16
0R15 R17
0R27
L2
DET1
HG
LG
D7S1M
D6S1M
PFCZCD
VDD
VS
VBO
AUX
R5 100R4 100R3 100
C17102P/100V
R20220K±1%
C18104P/50V
12
56
411
TX1
+C6
47μ
/450V
U1
1
2 3
Q5FDB031N08
21
D11
NCR19
R/0R
SRDET
SRDET
VO1
C10
YC/102P/250V
+
C9820μ/25V
C11YC/102P/250V
C3NC
C2NC
AC
AC -
+
BD2DF08S
VBO1
L4
S047
VO
21
ZD118V/0.5W
21
ZD218V/0.5W
VLD
OPFC
2 1
D8LL4148
R1351
2
13
Q32N2907
R14
100
R15NC
PFC_GATE
84
3
5
6 1
7
2
11
TX2
2 1
L3A220μ/DR127
L1
www.fairchildsemi.com25
D14LL4148
R46 51
YC/102P/250VD13LL4148
R47 51
R114.7M±1%
R124.7M±1%
R30154K±1%
R2278.7K±1%
D10RS1D
C27224P
C21NC
C25105P
R24220
C24
221P
C20102P
RANGE1
COMP2
INV3
CSPFC4
CSPWM5
OPFC6
VDD7
OPWM8
FB11
RT12
VIN13
ZCD14
N.C.15
HV16
GND9
DET10
U2
FAN6920
C29102P
R2647.5K
C23471P
R23220
VSPFC
R27 560
C26473P
OPFC
VSPWM
VS6
LO5
LIN3
HIN2
VB8
VCC1
COM4
HO7
U3
FAN7382
C30225P
VB
C31
104P
PFC_VO
TR1
NTC/100K
R313.6K
R298.2K±1%
R2847.5K±1%
C28NC
U4LTV357A
C33103P
R51330
R521.5K
R5068K, 1%
R5310K, 1%
R4910K
AK
RU5
KA431SAMF2TF
VO+
VO
2 1
D15ES1JH
HG
VBO
LGOPWM
OPWM
AUX
PFCZCD
FBPWM
FBPWM
VS
R219.1K±1%
R4811.3K±1%
R1847K±1%
C32NC
VO
C19104P
VDD
R6249K
R25 NC
C22474P
GATE3
PGND4
AGND6
LPC8
VDD5
RP/RES7
FAN6204/5
VDD
+ C1633uF/50V
VDD
OPWMR45NC
D12LL4148
2 1D5
SS16
PFC_GATE
Target Applications
• Power Range from 75W ~200W
• All in One (AIO) PC Power
• LED TV
• Notebook Adapter
• Game Console
• LED Lighting
www.fairchildsemi.com26
• LED Lighting
• Applications that Require High Efficiency and Low Standby
Power Consumption for Single Output
Ideal Solution for Both Efficiency and
Standby Power Consumption
EfficiencyStandby
Power Efficiency
Standby
Power
LLCSingle
Flyback
www.fairchildsemi.com27
LLCFlyback
Dual
Switch
Flyback
Excellent
Average
EfficiencyLow
Standby Power
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