Download 6，Reference Design

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FL7732MY
Design
presentation
Application fortitle
LED
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Peter Deng
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Dec 2012
Table of Contents
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2
FL7732MY Key Features
Basic operation
Systems reference design
Customer design Issue
Design Tool
Reference design
Product Map
FSC Success Story
1,FL7732MY Key Features
• Features:
 High power factor correction>0.9
 Accurate CC control about 3% without secondary feedback
 Very wide application voltage range: 80Vac~308Vac
 Cycle by cycle current limiting, and with compensation by line voltage
 With wide Vdd operation voltage
 Protection:
 Open-LED protection
 Short-LED protection.
 Over temperature protection with auto restart
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Basic Operation
Internal Block
1.
2.
IC operate voltage
OVP at LED open
1.
IC over temperature
protection
1.
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Linear frequency control base on
Vs voltage, improve efficiency
1.Current sensor
2. Power limit
Very simple
Constant
current loop
compensation
with one cap
about 1uf
1.
2.
Detect output voltage
Detect output discharge time
2，Basic Operation
2.1 Constant current control
The Io current calculation:
If the transformer is fix, So Io
value be related to Rsense.
But actually, Tdis is uncertain
during to Ic surrounding circuit
parameter.
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2， Basic Operation
2.2 Discharge time detect
1. IC will catch Vs voltage when 85% of last
time discharge to be sample voltage , when
Vs voltage drop over ΔV than the sample
voltage, IC consider the discharge time is
end
2.
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•
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Affect discharge time parameter
Vcc rectifier select fast Tr
select suitable filter capacitor
Secondary rectifier select fast Tr
2，Basic Operation
2.3 Linear Frequency Control
 When Vout decrease, the Vs will decrease
which cause frequency decrease, and Tdis
will increase, so make sure Io constant
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2，Basic Operation
2.4 Open LED Protection

When LED removed, the Vdd will continue
increasing till it trigger OVP. Then it will ender
in the Hiccup mode.

The calculation:
Vout_ovp=Ns/Na*Vovp

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Output electrolytic capacitor rated voltage must
be more than the Vout_ovp
2，Basic Operation
2.5 Short LED protection
 When LED shorted, the Vs become low during
to low output voltage
 Then OCP level down to 0.2V to reduce the
output power.
 It will ender in the Hiccup mode.
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3，Systems reference design
• Vdd design
1. the start-up resistor suggestion 100K~200K to make good start-up time.
2. the Vdd cap suggest 22uF~47uf to make Vdd voltage not drop
3.Adjust turn rate of Na/Ns to to make sure the max output
voltage to trigger the Vdd ovp.
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3，Systems reference design
• Vs function:
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•
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1. Detect output voltage
2. CC control
3. Frequency control
• Vs design:
1. Make Vs voltage is 2.35V when output is max
Vout*Na/Ns*(Rvs1/Rvs2)=2.35V
2. Cs suggestion 10pF~22pF
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3，Systems reference design
• COMI design:
1. COMI is constant current loop compensation, this pin is the output of the
transconductance error amplifier
2. Only use one cap to get the constant current compensation,
the reference value: 2.2uF~4.7uF. The cap affect PFC and overshoot when
start-up
3. The compensation cap must be nearby IC.
COMI
FL7732
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CcomI
3，Systems reference design
• CS pin design:
1. CS I is current sense , which detect the mosfet current for the output –
current regulation.
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4, Customer design Issue
4.1 Startup fail at CR Mode
Root Cause: Startup fail at CR mode is due to that output voltage could increase
rated voltage
Solution: increase the Vdd capacitor capacity.
Remark:
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LED load characteristic is as CV mode , not CR mode.
4, Customer design Issue
4.2 larger input power at Short LED
Root Cause:
Although Cs level down to 0.2V at short LED , but during to primary inductor
will be discharge slowly , the internal minimum on time 600ns energy will may
be cause IC enter CC mode, so input power will become larger.
Solution: 1. decrease Vcc capacitor capacity or enlarger startup resistor
2. enlarger transformer inductor
3. select second diode of small tr
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5，Design Tool
The Max Vout is OVP
voltage, normally it is
over 4~8V voltage.
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5，Design Tool
The Max duty is between 20%~45%
It maybe be larger at low line
it is smaller at high line
Ton should be less than 10us
Vcs <=0.67V
The max magnetic flux density <0.3T
The Np >=Np.min
Lik is normal 1%
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5，Design Tool
The Vsn should be larger than Vro and it is
typical to set to 2~2.5 times of Vro
The voltage set to 5%~10% of Vsn
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5，Design Tool
Vin.bnk normally is 30~70
Cvs normally is 10~30pF
Ccomi normally is 1uF~4.7uF
If output voltage is over shoot at high input
voltage when start-up , should be increased
Ccomi
Cvdd normally is 10uf~47u8uF.
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6，Design Design
Customer Spec:
 Application: T8/18W
 Input Voltage: 90Vac~264Vac
 Output : 58V/0.3A
 Efficiency: 92%
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6，Reference Design
6.1 buck-boost topology
Inductor
parallel
Why select FL7732, not FL7701 ?
1. FL7732 have line voltage compensation
2. FL7732 OVP function better FL7701
Why select Inductor parallel:
1. PCB size limit
2 . Better EMI
3. Be easy compatible to variety LED in same pcb
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6，Reference Design
6.1 buck-boost topology
115Vac
CV=55V /0.3A
Vdrain
Vdrain
I_mosfet
I_mosfet
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6，Reference Design
6.1 buck-boost topology
230Vac
CV=55V /0.3A
I_mosfet
I_mosfet
Vdrain
Vdrain
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6，Reference Design
6.1 buck-boost topology
Constant Current
Efficiency
115Vac
230Vac
CV (V)
Current(mA)
PF
CV (V)
Current(mA)
PF
55V
284
0.987
55V
290
0.945
50V
290
0.987
50V
290
0.940
45V
290
0.987
45V
289
0.932
40V
293
0.986
40V
292
0.924
35V
292
0.985
35V
290
0.910
30V
295
0.983
30V
291
0.898
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Voltage
Efficiency
115Vac
89.82%
230Vac
89.85%
6，Reference Design
6.2 buck topology
Line voltage
compensation
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6，Reference Design
6.2 buck topology
115Vac
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CV=55V /0.3A
6，Reference Design
6.2 buck topology
230Vac
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CV=55V /0.3A
6，Reference Design
6.2 buck topology
Constant Current
Efficiency
115Vac
230Vac
CV
Current
PF
CV
Current
PF
55V
305
0.978
55V
299
0.945
50V
300
0.981
50V
295
0.940
45V
284
0.983
45V
285
0.932
40V
265
0.985
40V
276
0.924
35V
256
0.986
35V
273
0.910
30V
247
0.984
30V
270
0.898
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Voltage
Efficiency
115Vac
91.67%
230Vac
90.75%
7，Product Map
Lamp Type
Ornament Lighting (≤ 20W)
Indoor/Outdoor (20 ~ 100W)
Light
Strip
(1.5W ~ 5W)
R-Lamp
(5W ~ 10W)
Street (100W +)
Non-Isolated
PFC Buck
FL7701
FL7730
FLS0116
Blub
(3W ~ 20W)
FL6300A
FL6961
FL6961 + FL6300A
PFC + LLC H/B +
ILED cont.
FL7930
FAN7621/31
FLSXX00XS
~
FLSXX00HS
FL6961
FAN7346
FAN7340/2
FL7734
FLS3217M
FLS3247
FL7730
FL7930 + FAN7621S
FL7930 + FLSxxxXS + FAN7346
FL7732
Rectifier : Ultra fast, Hyper fast I / II , Stealth™ II Diodes– 200/300/600V
PowerTrench® MOSFET, SuperFET ® 2 MOSFET, FRFET® MOSFET, UniFET™ II MOSFET – 25 ~ 1000V
Develop product
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FL6961
FL7733
FLS3247
FLS0116
Street Light
(50W ~
100W~)
PFC + QR
Flyback
FAN6300H
FLS3247
Down Light
(10W ~ 30W)
Flat Light
(50W ~ 60W)
Single Stage
PFC Flyback
FL7732
FLS3217
FL7701
L-Light
(20W ~ 30W)
PSR
Flyback
w/wo PFC
New Product
Released
8，FSC Success Story
Fairchild
Disty.
GPRC
PL&AE
Customer
FAE
1. Provide web-design ,china
microsite and webinar
2. Provide Customized demo
board Design
3. Provide customer training
and seminar
4. On line provide design skill
and technical support
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Contact Information
Web-design link:
http://www.fairchildsemi.com
http://www.fairchildsemi.com/design_tools/power-supply-webdesigner/
http://www.21ic.com/fairchild/
Peter Deng
P. 13682664856
[email protected]
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Thanks!
32
Thank You
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