ST AN2485 Application note
AN2485
Application note
400 W FOT-controlled PFC pre-regulator with the L6563
Introduction
This application note describes an evaluation board based on the Transition-mode PFC
controller L6563 and presents the resu lts of th e be nc h evaluation. The board implemen ts a
400 W, wide-range mains input, a PFC pre-conditioner suitable for ATX PSU, or a flat
screen display. The chip is operated with Fixed-Off-Time control in order to use a low-cost
device like the L6563 which is usually prohibitive at this power level. Fixed-Off-Time control
allows Continuous Conduction Mod e operation which is normally achieved with more
expensive control chips and more complex control architectures.
L6563 400W FOT PFC Demo board (EVAL6563-400W)
March 2007 Rev 1 1/29
www.st.com
Contents AN2485
Contents
1 Main characteristics and circuit description . . . . . . . . . . . . . . . . . . . . . 4
2 Test results and significant waveforms . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 Harmonic content measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Inductor current in FOT and L6563 THD optimizer . . . . . . . . . . . . . . . . . 10
2.3 Voltage feedforward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.4 Start-up and RUN pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.5 Start-up at light load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.6 Open loop protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.7 Power management/housekeeping functions . . . . . . . . . . . . . . . . . . . . . . 17
3 Layout hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4 Audible noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5 Thermal measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6 Conducted emission pre-compliance test . . . . . . . . . . . . . . . . . . . . . . 22
7 Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8 PFC coil specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.1 General description and characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.3 Mechanical aspect and pin numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
10 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2/29
AN2485 List of figures
List of figures
Figure 1. EVAL6563-400W evaluation board: electrical schematic. . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 2. EVAL6563-400W compliance to EN61000-3-2 at 230 Vac-full load . . . . . . . . . . . . . . . . . . 7
Figure 3. EVAL6563-400W compliance to JEIDA-MITI at 100 Vac-full load . . . . . . . . . . . . . . . . . . . . 7
Figure 4. EVAL6563-400W compliance to EN61000-3-2 at 230 Vac-70 W load . . . . . . . . . . . . . . . . 7
Figure 5. EVAL6563-400W compliance to JEIDA-MITI at 100 Vac-70 W load . . . . . . . . . . . . . . . . . . 7
Figure 6. EVAL6563-400W Input current waveform at 100 V - 60 Hz - 400 W load . . . . . . . . . . . . . . 8
Figure 7. EVAL6563-400W Input current waveform at 230 V - 50 Hz - 400 W load . . . . . . . . . . . . . . 8
Figure 8. EVAL6563-400W Input current waveform at 100 V - 60 Hz - 200 W load . . . . . . . . . . . . . . 8
Figure 9. EVAL6563-400W Input current waveform at 230 V - 50 Hz - 200 W load . . . . . . . . . . . . . . 8
Figure 10. EVAL6563-400W Input current waveform at 100 V - 60 Hz - 70 W load . . . . . . . . . . . . . . . 8
Figure 11. EVAL6563-400W Input current waveform at 230 V - 50 Hz - 70 W load . . . . . . . . . . . . . . . 8
Figure 12. Power Factor vs. Vin and load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 13. THD vs. Vin and load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 14. Efficiency vs. Vin and load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 15. Static Vout regulation vs. Vin and load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 16. EVAL6563-400W Inductor current ripple envelope at 115 Vac - 60 Hz - full load . . . . . . . 10
Figure 17. EVAL6563-400W Inductor current ripple (detail) at 115 Vac - 60 Hz - full load . . . . . . . . . 10
Figure 18. EVAL6563-400W Inductor current ripple envelope at 230 Vac - 50 Hz - full load . . . . . . . 11
Figure 19. EVAL6563-400W Inductor current ripple (detail) at 230 Vac - 50 Hz - full load . . . . . . . . . 11
Figure 20. EVAL6563-400W Input mains surge from 90 Vac to 140 Vac - full load - C
Figure 21. L6562 FOT Input mains surge from 90 Vac to 140 Vac - full load - NO V
Figure 22. EVAL6563-400W Input mains dip from 140 Vac to 90 Vac - full load - C
Figure 23. L6562 FOT Input mains dip from 90 Vac to 140 Vac - full load - NO V
Figure 24. EVAL6563-400W Input current shape at 100 Vac-60 Hz vs. V
Figure 25. EVAL6563-400W Input current shape at 100 Vac-60 Hz vs. V
FF
FF
FF
ripple - CFF = 470 nF . . 14
ripple - CFF = 1.5 uF . . . 14
Figure 26. EVAL6563-400W start-up at 90 Vac-60 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 27. EVAL6563-400W start-up at 265 Vac-50 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 28. EVAL6563-400W start-up at 80 Vac-60 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 29. EVAL6563-400W Start-up at 265 V -50 Hz - 30 mA load. . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 30. EVAL6563-400W start-up at 265 V -50 Hz - no load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 31. EVAL6563-400W open loop at 115 Vac-60 Hz - full load. . . . . . . . . . . . . . . . . . . . . . . . . . 16
Figure 32. L6563 On/Off control by a cascaded converter controller via PFC_OK or RUN pin . . . . . 17
Figure 33. Interface circuits that let the L6563/A switch on or off a PWM controller . . . . . . . . . . . . . . 18
Figure 34. EVAL6563-400W PCB layout (not 1:1 scaled) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 35. Thermal map at 115 Vac-60 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Figure 36. Thermal map at 230 Vac-50 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Figure 37. 115 Vac and full load - phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Figure 38. 115 Vac and full load - neutral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Figure 39. 230 Vac and full load - phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Figure 40. 230 Vac and full load - neutral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Figure 41. Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Figure 42. Pin side view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Figure 43. Mechanic aspect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
= 470 nF . . 12
FF
input . . . . . . . 12
FF
= 470 nF . . . . 13
FF
input . . . . . . . . . 13
3/29
Main characteristics and circuit description AN2485
1 Main characteristics and circuit description
The main characteristics of the SMPS are:
● Line voltage range: 90 to 265 Vac
● Minimum line frequency (f
● Regulated output voltage: 400 V
● Rated output power: 400 W
● Maximum 2f
● Hold-up time: 22 ms (V
● Maximum switching frequ ency: 85 kHz (@Vin=90 Vac, Pout=400 W)
● Minimum estimated efficiency: 90% (@Vin=90 Vac, Pout=400 W)
● Maximum ambient temperatur e: 50 °C
● EMI: in acc. with EN55022 Class-B
● PCB type and size: Single side, 70 um, CEM-1 , 148.5 x 132 mm
● Low profile design: 35 mm component maximum heigh t
output voltage ripple: 10 V pk-pk
L
The evaluation board implements a Power Factor Correc t ion (P F C) pr e- re gu la to r de livering
400 W continuous power on a regulated 400 V rail from a wide range mains voltage. The
board provides f or the reduction of the mains h armonics which allows meeting the standards
of the European norm EN61000-3-2 or the Japanese norm JEID A-MITI. This rail is the input
for the cascaded isol ated DC-DC converter that provides the output rails required by the
load.
): 47 Hz
L
after hold-up time: 300 V)
DROP
The board is equipped with enough heat sinking to allow full-load operation in still air. With
an appropriate airflow, and without any change in the circuit, the ev aluation board can easily
deliver up to 450 W.
The controller is the L6563 (U1), integrating all the functions needed to control the PFC
stage and to interface with the downstream con v erter . The L6563 controller chi p is designed
for Transition-Mode (TM) operation, where the boost inductor works next to the boundary
between Continuous (CCM) and Discontinuous Conduction Mode (DCM). However, with a
slightly different usage, the chip can operate so that the boost inductor works in CCM,
surpassing the limitations of TM operation in terms of power handling capability. The gatedrive capability of the L6563 is also adequate to drive the MOSFETs used at higher power
levels. This approach, which couples the simplicity and cost-effectiveness of TM operation
with the high-current capability of CCM operation, is the Fixed-Off-Time (FOT) control. The
control modulates the ON-time of the power switch, while its OFF-time is kept constant.
More precisely, the Line-Modulated FOT (LM-FOT), where the OFF-time of the power
switch is not rigorously constant but is modulated by the instantaneous mains voltage , will
be used. Please refer t o AN1792 (“De sign of Fixed-Off-Time-Controlled PFC Pre-regulators
with the L6562”) for a detailed description of this technique as indicated in Section 9:
References (point 2).
The power stage of the PFC is a conventional boost converter, connected to th e output of
the rectifier bridge D2. It includes the coil L4, the diode D3 and the capacitors C6 and C7.
The boost switch is represented by the power mosfets Q1 and Q2. The NTC R2 limits the
inrush current at switch on. It has been connect ed on the DC rail, in series to the output
electrolytic capacitor, in order to improve efficiency during low line operation. Additionally,
the splitting in two of output capacitors (C6 and C7) provides for managing the AC current
4/29
AN2485 Main characteristics and circuit description
mainly by the film capacitor C7 which allows fo r a less costly ele ctrolytic to bear on ly the DC
part.
At start-up the L6563 is powered b y the Vcc capacitor (C12) that is charged via the resistors
R3 and R4. The L4 secondary winding (pins #8-11) and the charge pump circuit (R5, C10,
D5 and D4) generate the Vcc voltage powering the L6563 during normal operations.
The divider R32, R33 and R34 provides the L6563 multiplier with the information of the
instantaneous voltage t hat is used to modula te the boost current. T he instantaneous v oltage
information is also used to get the average value of the AC line by the V
(Voltage Feed-
FF
Forward) pin . Divider R9, R10, R11, R12, and R13 is dedicated to sense output voltage
while divider R6, R7, R8, and R24 is dedicated to protect t he circuit in case of voltage loop
failures. The Line-Modu lated FOT is obtained by the timing generator components D6, C1 5,
R15, C16, R16, R31, and Q3.
The board is equipped with an input EMI filter designed for a 2-wire input mains plug. It is
composed of two stages, a Common Mode Pi-filter connected at the input (C1, L1, C2, C3)
and a Differential Mode Pi-filter afte r the input bridge (C4, L3, C5). The boar d also off ers the
possibility to easily connect a downstream converter and test the interface signals managed
by the L6563.
5/29
Main characteristics and circuit description AN2485
Figure 1. EVAL6563-400W evaluation board: electrical schematic
NC
RTN
RTN
+400Vdc
+400Vdc
J2
12345
+400Vdc
R2
NTC 2R5-S237
D3
STTH8R06
D1
1N5406
L4
PQ40-500uH
5-6 1-2
L3
DM-51uH-6A
+
D2
D15XB60
~
L2
RES
JP101
JUMPER
1 2
L1
CM-1.5mH-5A
F1
8A/250V
+400Vout
C7
330uF-450V
C6
470nF-630V
811
C5
470nF-630V
C4
470nF-630V
-
~
C3
680nF-X2
C9
RES
C8
RES
1 2
C2
470nF-X2
C1
470nF-X2
R1
1M5
Q2
STP12NM50FP
Q1
STP12NM50FP
D8
D7
LL4148
R36
3R9
C10
18N
D5
R5
47R
R3
180K
R4
180K
R102
JP102
JUMPER
R10
680k
R9
680k
+400Vdc
BZX85-C15
D4
LL4148
D6
LL4148
C15
100pF
C12
47uF/50V
C11
470nF/50V
10
12
0R0
R11
680k
R6
2M2
R7
2M2
14
R13
15k
VCC
U1
L6563
R12
82K
INV1COMP2MULT3CS4VFF5TBO6PFC-OK
R14
56k
C13
100nF
C14
1uF
R8
2M2
11
13
GD
ZCD
RUN
GND
LL4148
R17
6R8
R15
3K3
R16
R28
RES
9
PWM-STOP
15K
C16
220pF
123J3RES
R29
RES
8
7
R18
6R8
R35
3R9
R31
1k5
R30
RES
PWM-LATCH
R26
C17
10nF
R24
36K
R23
0R39-1W
R22
0R39-1W
R21
0R39-1W
R20
0R39-1W
R19
1K0
C20
330pF
R101
0R0
Q3
BC857C
C19
2nF2
R27
240k
150k
C21
C18
470nF
10nF
R34
10k
R33
620k
R32
620k
1
2
J1
90 - 265Vac
6/29
AN2485 Test results and significant waveforms
2 Test results and significant waveforms
2.1 Harmonic content measurement
One of the main purposes of a PFC pre-conditioner is the correction of input current
distortion, decreasing the harmonic contents below the limits of European and Janapese
regulations. The board has been teste d according to Europ ean norm EN61000-3-2 Class-D
and Japanese norm JEIDA-MITI Class-D, at full load and 70 W output power, at both the
nominal input voltage mains.
As shown in Figure 2, 3, 4, and 5, the circuit is able to reduce the harmonics well below the
limits of both regulations from full load down to light load. 70 W of output power has been
chosen because it is almost the lower power limit at which the harmonics must be limited
according to these international norms.
Figure 2. EVAL6563-400W compliance to
10
1
0.1
0.01
Harmo nic Curr en t [A]
0.001
EN61000-3-2 at 230 Vac-full load
Measured value EN61000-3-2 Cla ss-D limits
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Harmoni c Order [n]
Figure 4. EVAL6563-400W compliance to
1
0.1
EN61000-3-2 at 230 Vac-70 W load
Measured value EN61000-3-2 Class-D lim i ts
Figure 3. EVAL6563-400W compliance to
JEIDA-MITI at 100 Vac-full load
Measured value JEIDA-MI T I Cla ss-D lim its
10
1
0.1
0.01
Harmoni c Current [A]
0.001
1 3 5 7 9 111315171921232527293133353739
Harmonic Order [n]
Figure 5. EVAL6563-400W compliance to
JEIDA-MITI at 100 Vac-70 W load
Measured value JEIDA-MI T I Class-D lim i ts
1
0.1
0.01
Harmo nic Cu r r ent [A]
0.001
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Harmonic Order [n]
For user reference, waveforms of the input current and voltage at the nominal input voltage
mains and different load conditions are given in Figure 6, 7, 8, 9, 10, and 11.
0.01
Harm o n ic Cur r e n t [A]
0.001
1 3 5 7 9 111315171921232527293133353739
Harmonic Order [n]
7/29
Test results and significant waveforms AN2485
Figure 6. EVAL6563-400W Input current
waveform at 100 V - 60 Hz - 400 W
load
Figure 8. EVAL6563-400W Input current
waveform at 100 V - 60 Hz - 200 W
load
Figure 7. EVAL6563-400W Input current
waveform at 230 V - 50 Hz - 400 W
load
Figure 9. EVAL6563-400W Input current
waveform at 230 V - 50 Hz - 200 W
load
Figure 10. EVAL6563-400W Input current
waveform at 100 V - 60 Hz - 70 W
8/29
load
Figure 11. EVAL6563-400W Input current
waveform at 230 V - 50 Hz - 70 W
load
AN2485 Test results and significant waveforms
The Power Factor (PF) and the Total Harmonic Distortion (THD) have been measured too
and the results are reported in Figure 12. and Figure 13. As shown, the PF at full load and
half load remains close to unity throughout the input voltage mains range while it decreases
at high mains range when the circuit is deliv ering 70 W. THD is low, remaining within 25% at
maximum input voltage .
Figure 12. Power Factor vs. Vin and load Figure 13. THD vs. Vin and load
PF
1.05
1
0.95
0.9
RMS
400W
200W
70W
]
0.85
0.8
0.75
0.7
90 100 115 130 180 230 265
VIN [V
THD [%]
30
V
IN [VRMS
400W
200W
70W
]
25
20
15
10
5
0
90 100 115 130 180 230 265
Efficiency is very good at all load and line conditions. At full load it is always significantly
higher than 90%, making this design suitable for high efficiency power supply.
The measured output voltag e v ariation at different line and load conditions is given in Figure
15. As shown, the voltage is perfectly stable over the input vo lta ge r ang e d ue to th e Voltage
Feed-Forward function embedded in the L6593. Only at 265 Vac and light load, there is a
negligible deviation of 1 V due to the intervention of the burst mode (for the "static OVP")
function.
Figure 14. Efficiency vs. Vin and load Figure 15. Static Vout regulation vs. Vin and
Eff [%]
100%
95%
90%
85%
80%
75%
90 100 115 130 180 230 265
VIN [V
RMS
400W
200W
70W
15W
]
404
403.5
403
402.5
402
401.5
401
400.5
400
load
V
[VDC]
OUT
400W
200W
70W
15W
90 100 115 130 180 230 265
VIN [V
]
RMS
9/29
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