AD2 - Adapter Less than 75 W

Adapters < 75 W
Agenda
• New ENERGY STAR® requirements
• Needed features to meet the new specification
• New controllers
• Practical examples
• Conclusion
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EPA 2.0 (External Power Supplies)
(was > 0.84 in previous version 1.1)
(< 0.5 W in 1.1)
(< 0.75 W in 1.1)
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Agenda
• New ENERGY STAR® requirements
• Needed features to meet the new specification
• New controllers
• Practical examples
• Conclusion
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Improving Efficiency
•
Sources of loss:
– Switching losses:
Ploss ( switching ) =
1
2
⋅ C DRAIN ⋅ VDRAIN ( turn−off ) ⋅ FSW
2
– Gate charge losses:
Ploss ( gate ) = Vgate ( high) ⋅ Qgate ⋅ FSW
•
Ways to improve efficiency:
– Lower the switching frequency FSW Î frequency foldback at light loads
– Lower the Drain voltage at turn-off Î valley switching
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Reducing No-load Input Power
• Static losses in the start-up circuit:
– Start-up resistor permanently drawing current from the bulk capacitor
• Ways to lower the start-up circuit losses
– With external start-up resistor
Î Extremely low start-up current
– Integrated start-up current source Î Extremely low leakage when off
– Connect the start-up circuit to the half-wave rectified ac input
HV rail
Start-up resistors
NCP1351
1
8
2
7
3
6
4
5
Vcc
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Agenda
• New ENERGY STAR® requirements
• Needed features to meet the new specification
• New controllers
• Practical examples
• Conclusion
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The Right Controllers
• Two new families of controllers implement features to
increase efficiency and lower no-load input power:
– NCP1237/38/87/88:
fixed-frequency controllers with integrated start-up current
source, frequency foldback and skip mode
Æ Increased efficiency at light load and standby
– NCP1379/80
valley switching controllers with extremely low start-up
current and frequency foldback
Æ Increased efficiency at all load levels
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NCP1237/38/87/88
Value Proposition
The NCP12X7/X8 series represents the next generation of fixed frequency PWM controllers. It targets applications
where cost-effectiveness, reliability, design flexibility and low standby power are compulsory.
Unique Features
ƒ High-voltage current source
with built-in Brown-out and
mains OVP
ƒ Freq. reduction in light load
conditions and skip mode
ƒ Adjustable Over Power
Protection
Benefits
Application Data
ƒ Fewer components and
rugged design
ƒ Extremely low no-load
standby power
ƒ Simple option to alter the
max. peak current set
point at high line
DSS
NCP1237A
NCP1237B
NCP1238A
NCP1238B
NCP1287A
NCP1287B
NCP1288A
NCP1288B
Others Features
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
Latch-off input for severe fault conditions, allowing
direct connection of NTC
Timer-based protection: auto-recovery or latched
Dual OCP option available
Built-in ramp compensation
Frequency jittering for a softened EMI signature
Vcc operation up to 30 V
Market & Applications
ƒ
ƒ
AC-DC adapters for notebooks, LCD monitor, game
console, printers
CE applications (DVD, STB)
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Yes
Yes
Yes
Yes
HV only
HV only
HV only
HV only
Dual
OCP
Yes
Yes
No
No
Yes
Yes
No
No
Latch
Auto
Recovery
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Various options available depending
upon end applications needs
Ordering & Package Information
ƒ
ƒ
NCP1237/38xDR2G - NCP1287/88xDR2G
SOIC-7 2500p per reel
Pb O, DW
NCP1237/38/87/88 – Brown-out and Mains OVP
HV
Detection independent of
Ripple on HV pin
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Can be connected to the
half-wave rectified ac line
NCP1237/38/87/88 – Brown-out and Mains OVP
Timer-based detection
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Passes full line cycle drop-out
NCP1237/38/87/88 – Over Power Protection
Need to compensate for the
effect of the propagation delay
Over Power Protection
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The compensation current
creates an offset on the
Current Sense signal
Maximum output power clamped
NCP1237/38/87/88 – Frequency Foldback
Switching frequency
lowered at light load
Increased efficiency
Switching frequency
clamped at 25 kHz
No audible noise
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NCP1237/38/87/88 – Latch-off Protection
Vcc
VLATCH
OVP
Latch!
LATCH
OK
Latch!
OTP
time
An NTC thermistor can be directly connected to the IC
Less external components needed
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NCP1379/80
Value Proposition
The NCP1380 is a high-performance circuitry aimed to powering QR converters. Capitalizing on a novel valley-lockout
system, the controller shifts gears and reduces the switching frequency as the power loading becomes lighter.
Unique Features
ƒ Valley switching operation
with valley-lockout
ƒ Freq. reduction in light load
condition
ƒ Adjustable Over Power
Protection
Benefits
Application Data
ƒ Excellent efficiency over a
wide range and noise free
operation
ƒ Extremely low no-load
standby power
ƒ Simple option to alter the
max. peak current set
point at high line
HV-bulk
Vout
Chrono A/B
ZCD / OPP
1
Others Features
ƒ
ƒ
ƒ
ƒ
ƒ
Auto-recovery or latched internal output short-circuit
protection
Fixed 80 ms timer for short-circuit protection
Combined Over-voltage and over-temperature
protection (A and B versions)
Combined OVP & brown-out (C and D versions)
3 µs blanking delay to ignore leakage ringing at turn-off
Market & Applications
ƒ
ƒ
ƒ
AC-DC adapters for notebooks, LCD monitor, game
console
Auxiliary power for Flat TVs
CE applications (DVD, STB)
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Gnd
OVP
8
2
7
3
6
4
5
OTP
Gnd
Design flexibility
Ordering & Package Information
ƒ
ƒ
NCP1380xDR2G
SOIC-8 2500p per reel
Pb
O, DW
NCP1379/80 - QR Mode with Valley Lockout
•
•
As the load decreases, the controller changes valley (1st to 4th valley)
The controller stays locked in a valley until the output power changes
significantly.
¾ No valley jumping noise
¾ Natural switching frequency limitation
80000
SWITCHING FREQUENCY (Hz)
70000
60000
50000
4th
3rd
2nd
1st
40000
30000
20000
QR operation
10000
0
0
10
VCO mode
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20
30
OUTPUT POWER (W)
40
50
60
NCP1379/80 - Frequency Foldback
•
•
Occurs when VFB < 0.8 V (POUT decreasing) or VFB < 1.6 V (POUT
increasing)
Fixed peak current (25% of Ipk,max), variable frequency set by the FB
loop.
Ipk max
Constant peak current (25% of Ipk max)
Fsw1 @ Pout1
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Fsw2 @ Pout2
Pout1 > Pout2
NCP1379/80 - Frequency Foldback
•
•
The switching frequency is set by the end of charge of Ct capacitor
The end of charge of Ct capacitor is controlled by the FB loop
Vdd
Load
Rpullup
FB
Enable VCO
mode
Ct
6.5-(10/3)Vfb
VFBth
ICt
VCO
-
Vdd
Ct
+
Ct
discharge
Controlled by FB loop
S
DRV
Q
Q
R
CS comparator
(Timing capacitor voltage)
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NCP1379/80 - Overpower Protection
•
•
•
Laux with flyback polarity swings to –NVIN during the on time.
Adjust amount of OPP voltage with Ropu // Ropl.
VCS,max = 0.8 V + VOPP
Ropu
CS
ZCD/OPP
OPP
Peak current
set point
IpFlag
1
Aux
Ropl
ESD
protection
V ILIMIT
100%
+
-
Demag
60%
Vth
leakage blanking
DRV
Tblank
370
Non dissipative OPP !
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VIN (V)
Agenda
• New ENERGY STAR® requirements
• Needed features to meet the new specification
• New controllers
• Practical examples
• Conclusion
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20
Fixed-Frequency Example: Schematic
10k
10k
2.7k
57.4k
120k/0.5W
A typical 65 W notebook adapter (19 V output)
(not optimized for EPS 2.0)
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Fixed-Frequency Example: Efficiency
•
EPS 2.0 efficiency (compared to NCP1271, from a previous generation)
VIN
% of POUTnom
100 %
(65 W)
75 %
(49 W)
50 %
(32 W)
25 %
(16 W)
115 Vac
230 Vac
NCP1271
NCP1271
88.5 %
88.7 %
88.4 %
88.2 %
89.2 %
89.1 %
88.2 %
88.3 %
88.9 %
88.9 %
86.8 %
87.0 %
88.2 %
88.4 %
87.3 %
Average at 230 Vac: 87.7 %
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84.3 %
Effect of the
frequency
foldback
Fixed-Frequency Example: Standby Power
•
Light load and no load input power with the NCP1237
(compared to NCP1271, from a previous generation)
VIN
POUT
230 Vac
NCP1271
NCP1271
10.7 W
12.0 W
(88.7 %)
12.2 W
(87.5 %)
12.5 W
(85.1 %)
13.2 W
(80.76 %)
1.3 W
1.67 W
(78.0 %)
1.77 W
(72.9 %)
1.75 W
(74.2 %)
2.46 W
(52.4 %)
0.5 W
0.74 W
(69.0 %)
0.81 W
(62.6 %)
0.76 W
(66.0 %)
1.34 W
(37.3 %)
No load
71 mW
76 mW
97 mW
121 mW
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115 Vac
Fixed-Frequency Example: Summary
95
Efficiency (%)
85
75
– 115 Vac - NCP1237
– 230 Vac - NCP1237
65
– 115 Vac - NCP1271
– 230 Vac - NCP1271
55
45
35
0
10
20
30
40
Ouput power (W)
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50
60
70
Valley Switching Example: Efficiency
•
EPS 2.0 efficiency with the NCP1380, valley switching controller
VIN
115 Vac
230 Vac
100 %
88.7 %
91.1 %
75 %
88.8 %
90.9 %
50 %
89.2 %
89.1 %
25 %
88.2 %
87.9 %
% of POUTnom
Average at 115 Vac: 88.7 %
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Valley Switching Example: Standby Power
•
Light load and no load input power with the NCP1380
VIN
115 Vac
230 Vac
10.7 W
12.37 W
(86.5 %)
12.44 W
(86 %)
1.3 W
1.85 W
(70.3 %)
1.82 W
( 71.4 %)
0.5 W
0.82 W
(61 %)
0.78 W
(64.1 %)
No load
122 mW
210 mW
POUT
No-load standby power meets ENERGY STAR® with a start-up resistor!
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Agenda
• New ENERGY STAR® requirements
• Needed features to meet the new specification
• New controllers
• Practical examples
• Conclusion
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27
Adapters < 75 W: Conclusion
• Meeting the most recent requirements from ENERGY STAR®
or IEC is possible with the classical Flyback converter
• Two new controllers sharing the same concept of frequency
foldback at light load make it possible:
– Fixed-frequency: NCP1238 family
– Valley-switching (Quasi-resonant, QR): NCP1380 family
• Average efficiencies above 87% are possible
• No-load input power below 300 mW is possible, even with a
start-up resistor
• No-load input power below 100 mW is achievable, although
the controller alone cannot ensure this. The whole power
supply must be designed to reduce power waste.
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For More Information
•
View the extensive portfolio of power management products from ON
Semiconductor at www.onsemi.com
•
View reference designs, design notes, and other material supporting
the design of highly efficient power supplies at
www.onsemi.com/powersupplies
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