Download Single Stage 800 mA Converter with High Power Factor

DN06069/D
Design Note – DN06069/D
Single Stage, Off-line, Isolated 12 Volt,
800 mA Converter with High Power Factor
Device
Application
Input Voltage
Output Power
Topology
I/O Isolation
NCP1028
LED lighting, white
goods, bias supplies
90 to 265 Vac
10 W nominal
DCM Flyback
Yes – 3 kV
Output
Output Voltage
Nominal Current
Peak Current
12 V
100 to 700 mA
800 mA
PFC (Yes/No)
Inrush Limiting / Fuse
Operating Temp. Range
Cooling Method /
Supply Orientation
Signal Level Control
Yes
1 A fuse
0 to +60°C
Convection
None
Others Isolated, step-down conversion with high power factor in a single converter.
Since this is a monolithic current mode control chip, the
ramp compensation pin was utilized to negate some of
the feed-forward effects of current mode control to
improve the power factor. Feed-forward pre-regulates off
the 120 Hz rectified line ripple which is detrimental to the
overall power factor because it prevents true fixed ontime duty ratio through a complete ac line cycle. This is
essential for high power factor when using a
discontinuous mode (DCM) flyback topology to
implement an isolated, single stage PFC converter.
Circuit Description
This design note (DN) describes an off-line, low power,
isolated power supply which has inherent active power
factor correction (PFC) integrated into the single stage
flyback power topology. This power supply is intended
for LED lighting, white goods, industrial, and other
applications where a high input power factor is required
despite the low power output. For example, Energy Star
requires PF > 0.9 for commercial lighting applications;
and PF > 0.7 for similar residential lighting applications
above 5 watts output. In this design example, the power
supply output can provide in excess of 750 mA at 12
volts nominal. Other output configurations are possible
by merely changing the transformer design (secondary
turns) and the output sensing zener diode (Z1).
Details and additional application notes on the NCP1028
monolithic controller can be found at the ON
Semiconductor website. For higher power, single stage
PFC converters please see information on the
NCP1608, NCP1652A, NCL30000, and the NCL30001
controllers.
Despite the overall simplicity, one of the drawbacks of
incorporating PFC and voltage conversion in a single,
isolated power stage is that the feedback loop must have
narrow bandwidth (< 40 Hz) otherwise the power factor
would be low (capacitor C8 sets the bandwidth). As a
consequence, the 120 Hz line ripple is propagated to the
output and can only be filtered by the output
capacitance. In this example 2,000 uF of output
capacitance was adequate to keep the 120 Hz ripple to
about 700 mV p/p with a load of 700 mA (~ 6%).
Additional output capacitance will reduce it even more.
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Key Features
y Simple, low power converter with high input PF
y Power factor above 0.9 for 120 vac operation for most
typical loads
y Inherent over-current and over-temperature protection
y Input EMI filter
y Easily adjustable for other output voltage/current
configurations
1
DN06069/D
Schematic
F1
L1
3.9 mH
1 A,
AC 250 Vac
C1
R1
input
1M 10 nF
0.5W "x"
D1-D4
MRA4007
T1
C2
10 nF
"x"
R2
22
C3
0.1uF
400V
D6
MBRS360T
10
R3
100K,
1W 1
C4
2.7 nF
2 kV
+
C7
0.1
C6
C5
6
9
D5
1N4936
R4
10K
5
12 Vdc @
800mA max
_
1000 uF
16V
x2
2
MMSD4148A
R12
1.5M
R8
10
D7
NCP1028
(100 kHz)
5
3
C10
10 uF
25V
C11
1 nF
D9
R5
Vtrim
(0 ohm)
R9
1K
R6
U1
MMSD4148A
D8
Z1
MMSZ5242B
8
+
R11
1.5M
3
2
4
4
R10
39K
7
1
8
U2
1
R7
330
C8
+ C9
47 uF
25V
1 uF
47
3
opto
2
NOTES:
1. L1 is Coilcraft E3491-AL common mode EMI inductor (3.9 mH)
2. See Magnetics Data Sheet for T1 construction details (EF-16 core & horizontal bobbin)
3. Z1 zener sets Vout: Vout = Vz + 0.85V; R5 is optional voltage trim (up) resistor
4. R10 sets slope compensation (which optimizes PF)
5. Values of "X" caps C1 & C2 will influence power factor at light loads (more C = lower PF)
6. Crossed schematic lines are not connected
10 Watt, 12 Volt Output Single Stage
Power Factor Corrector Supply (Rev 1)
1
© 2010 ON Semiconductor.
Disclaimer: ON Semiconductor is providing this design note “AS IS” and does not assume any liability arising from its use; nor
does ON Semiconductor convey any license to its or any third party’s intellectual property rights. This document is provided only to
assist customers in evaluation of the referenced circuit implementation and the recipient assumes all liability and risk associated
with its use, including, but not limited to, compliance with all regulatory standards. ON Semiconductor may change any of its
products at any time, without notice.
Design note created by Frank Cathell, e-mail: [email protected]
April 2010, Rev. 0
www.onsemi.com
2
DN06069/D
MAGNETICS DESIGN DATA SHEET
Project / Customer: ON Semiconductor - 10 watt single stage PFC xfmr
Part Description: 10 watt NCP1028 DCM PFC transformer, 100 kHz, 12V / 800mA (Rev 1)
Schematic ID: T1
Core Type: E24/25 (E25/10/6); 3C90 material or similar
Core Gap: Gap for 725 to 775 uH across pins 2 and 10 with pins 1 and 9 connected
Inductance: 750 uH +/-5% (across pins 2 and 10 with pins 1 and 9 connected)
Bobbin Type: 10 pin horizontal mount for E24/25 (E25/10/6)
Windings (in order):
Winding # / type
Turns / Material / Gauge / Insulation Data
Primary A (1 - 10)
25 turns of #30HN over 1 layer. Insulate with tape
for 1.5 kV to next winding. Self leads to pins..
Vcc (3 - 8)
5 turns of #30 HN spiral wound over 1 layer with
3 mm end margins minimum. Self leads to pins.
Insulate with 1 layer of Mylar tape.
12V Secondary (5 - 6)
5 turns of two pieces of #26 triple insulated
wire wound bifilar over previous winding evenly
and in 1 layer. Insulate with 1 layer of tape;
Self leads to pins.
Primary B (2 - 9)
Same as Primary A.
Hipot: 3 kV from primaries & Vcc to secondary for 1 minute.
Lead Breakout / Pinout
Schematic
(Top View)
10
10 9 8 7 6
1
5
9
2
6
3
12 3 4 5
8
April 2010, Rev. 0
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3
DN06069/D
Power Factor and Efficiency versus Load Plots
PF versus Iout
1
Power Factor
0.95
120 Vac
0.9
230 Vac
0.85
0.8
0.3
0.4
0.5
0.6
0.7
Output current (amps)
1
Efficiency % versus Iout
81
Efficiency (%)
80
79
Eff -120Vac
78
Eff - 230Vac
77
76
75
0.3
0.4
0.5
0.6
0.7
0.8
Output current (amps)
1
© 2010N Semiconductor.
Disclaimer: ON Semiconductor is providing this design note “AS IS” and does not assume any liability arising from its use; nor
does ON Semiconductor convey any license to its or any third party’s intellectual property rights. This document is provided only to
assist customers in evaluation of the referenced circuit implementation and the recipient assumes all liability and risk associated
with its use, including, but not limited to, compliance with all regulatory standards. ON Semiconductor may change any of its
products at any time, without notice.
Design note created by Frank Cathell, e-mail: [email protected]
April 2010, Rev. 0
www.onsemi.com
4
DN06069/D
120 Hz Output Ripple
700 mA Load; Cout = 2000 uF (2 volts per division vertical)
350 mA Load; Cout = 2000 uF
1
© 2010 ON Semiconductor.
Disclaimer: ON Semiconductor is providing this design note “AS IS” and does not assume any liability arising from its use; nor
does ON Semiconductor convey any license to its or any third party’s intellectual property rights. This document is provided only to
assist customers in evaluation of the referenced circuit implementation and the recipient assumes all liability and risk associated
with its use, including, but not limited to, compliance with all regulatory standards. ON Semiconductor may change any of its
products at any time, without notice.
Design note created by Frank Cathell, e-mail: [email protected]
April 2010, Rev. 0
www.onsemi.com
5