AN2994
Application note
400 W FOT-controlled PFC pre-regulator with the L6563S
Introduction
This application note describes a demonstration board based on the transition-mode PFC
controller L6563S and presents the results of its bench evaluation. The board implements a
400 W, wide-range mains input, PFC pre-conditioner suitable for ATX PSU, flat screen
displays, etc. The chip is operated with fixed off time control in order to use a low-cost device
like the L6563S, which is usually prohibitive at this power level. Fixed-off-time control allows
continuous conduction mode operation, which is normally achieved with more expensive
control chips and more complex control architectures.
Figure 1.
L6563S 400 W FOT PFC demonstration board (p/n EVL6563S-400W)
November 2010
Doc ID 15796 Rev 2
1/38
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Contents
AN2994
Contents
1
2
Main characteristics and circuit description . . . . . . . . . . . . . . . . . . . . . 5
Test results and significant waveforms . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
Harmonic content measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Inductor current in FOT and L6563S THD optimizer . . . . . . . . . . . . . . . . 12
Voltage feed-forward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Start-up and RUN pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Brownout function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Start-up at light loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Overvoltage and open-loop protection . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Power management/housekeeping functions . . . . . . . . . . . . . . . . . . . . . . 24
3
4
5
6
7
8
Layout hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Audible noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Thermal measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Conducted emissions pre-compliance tests peak detection . . . . . . . 30
Bill of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
PFC coil specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8.1
8.2
8.3
General description and characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Mechanical aspects and pin numbering . . . . . . . . . . . . . . . . . . . . . . . . . . 35
9
10
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
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Doc ID 15796 Rev 2
AN2994
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.
Figure 30.
Figure 31.
Figure 32.
Figure 33.
Figure 34.
Figure 35.
Figure 36.
Figure 37.
Figure 38.
Figure 39.
Figure 40.
Figure 41.
Figure 42.
Figure 43.
Figure 44.
Figure 45.
L6563S 400 W FOT PFC demonstration board (p/n EVL6563S-400W). . . . . . . . . . . . . . . . 1
EVL6563S-400W demonstration board: electrical schematic . . . . . . . . . . . . . . . . . . . . . . . 7
EVL6563S-400W compliance to EN61000-3-2 Standard at full load . . . . . . . . . . . . . . . . . . 8
EVL6563S-400W compliance to JEITA-MITI Standard at full load. . . . . . . . . . . . . . . . . . . . 8
EVL6563S-400W compliance to EN61000-3-2 Standard at 70 W load . . . . . . . . . . . . . . . . 8
EVL6563S-400W compliance to JEITA-MITI Standard at 70 W load . . . . . . . . . . . . . . . . . . 8
EVL6563S-400W input current waveform at 100 V, 60 Hz, 400 W load. . . . . . . . . . . . . . . . 9
EVL6563S-400W input current waveform at 230 V, 50 Hz, 400 W load. . . . . . . . . . . . . . . . 9
EVL6563S-400W input current waveform at 100 V, 60 Hz, 200 W load. . . . . . . . . . . . . . . . 9
EVL6563S-400W input current waveform at 230 V, 50 Hz, 200 W load. . . . . . . . . . . . . . . . 9
EVL6563S-400W input current waveform at 100 V, 60 Hz, 70 W load. . . . . . . . . . . . . . . . 10
EVL6563S-400W input current waveform at 230 V, 50 Hz, 70 W load. . . . . . . . . . . . . . . . 10
Power factor vs. Vin and load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
THD vs. Vin and load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Efficiency vs. Vin and load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Static Vout regulation vs. Vin and load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
EVL6563S-400W inductor current ripple envelope at 115 Vac, 60 Hz, full load. . . . . . . . . 12
EVL6563S-400W inductor current ripple (detail) at 115 Vac, 60 Hz, full load . . . . . . . . . . 12
EVL6563S-400W inductor current ripple envelope at 230 Vac, 50 Hz, full load. . . . . . . . . 13
EVL6563S-400W inductor current ripple (detail) at 230 Vac, 50 Hz, full load . . . . . . . . . . 13
EVL6563S-400W input current shape at 100 Vac, 60 Hz, CFF = 470 nF, RFF = 390 kΩ
. .15
EVL6563S-400W input current shape at 100 Vac, 60 Hz, CFF = 1.5 µF, RFF = 390 kΩ
. .15
EVL6563S-400W input mains surge from 90 Vac to 140 Vac, full load, CFF = 1 µF . . . . . 16
L6562A FOT input mains surge from 90 Vac to 140 Vac, full load, NO VFF input . . . . . . . 16
EVL6563S-400W input mains dip from 140 to 90 Vac, full load, CFF = 1 µF. . . . . . . . . . . 17
L6562A FOT input mains dip from 140 to 90 Vac, full load, NO VFF input . . . . . . . . . . . . 17
EVL6563S-400W start-up at 90 Vac, 60 Hz, full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
EVL6563S-400W start-up at 265 Vac, 50 Hz, full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
EVL6563S-400W start-up attempt at 80 Vac, 60 Hz, full load . . . . . . . . . . . . . . . . . . . . . . 19
EVL6563S-400W start-up with slow input voltage increase - full load . . . . . . . . . . . . . . . . 20
EVL6563S-400W turn-off with slow input voltage decrease - full load . . . . . . . . . . . . . . . . 20
EVL6563S-400W start-up at 265 V, 50 Hz, 30 mA load . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
EVL6563S-400W start-up at 265 V, 50 Hz, no load and with external Vcc . . . . . . . . . . . . 21
EVL6563S-400W open loop at 115 Vac,60 Hz, full load . . . . . . . . . . . . . . . . . . . . . . . . . . 23
On/Off control by a cascaded converter controller via PFC_OK or RUN pin . . . . . . . . . . . 24
Interface circuits that let the L6563S switch a PWM controller on or off. . . . . . . . . . . . . . . 25
EVL6563S-400W PCB layout (not 1:1 scaled) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Thermal map at 115 Vac, 60 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Thermal map at 230 Vac, 50 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
115 Vac and full load - phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
115 Vac and full load - neutral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
230 Vac and full load - phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
230 Vac and full load - neutral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Side view of pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
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List of tables
AN2994
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Measured temperature at 115 Vac and 230 Vac - full load . . . . . . . . . . . . . . . . . . . . . . . . 29
Bill of materials for the EVL6563S-400W demonstration board . . . . . . . . . . . . . . . . . . . . . 31
Winding characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
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Doc ID 15796 Rev 2
AN2994
Main characteristics and circuit description
1
Main characteristics and circuit description
The EVL6563S-400W demonstration board has the following characteristics.
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Line voltage range: 90 to 265 Vac
Minimum line frequency (f
L
): 47 Hz
Regulated output voltage: 400 V
Rated output power: 400 W
Maximum 2f
L
output voltage ripple: 10 V pk-pk
Hold-up time: 22 ms (V
DROP
after hold-up time: 300 V)
Maximum switching frequency: 85 kHz (Vin = 90 Vac, Pout = 400 W)
Minimum estimated efficiency: 90% (Vin = 90 Vac, Pout = 400 W)
Maximum ambient temperature: 50 °C
EMI: in accordance with EN55022 Class-B
PCB type and size: single side, 70 µm, CEM-1, 148.5 x 132 mm
Low profile design: 35 mm component maximum height
The demonstration board implements a power factor correction (PFC) pre-regulator
delivering 400 W of continuous power on a regulated 400 V rail from a wide-range mains
voltage, and providing for the reduction of the mains harmonics, thus complying with the
European norm EN61000-3-2 and the Japanese norm JEITA-MITI. This rail will be the input
for the cascaded isolated DC-DC converter that will provide the output voltages required by
the load.
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 demonstration board can
easily deliver up to 450 W.
The controller is the L6563S (U1), integrating all the functions needed to control the PFC
stage and to interface with the downstream converter. The L6563S controller chip 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,
hence surpassing the limitations of TM operation in terms of power handling capability. The
gate-drive capability of the L6563S 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) is used, where the OFF time of
the power switch is not rigorously constant but is modulated by the instantaneous mains
voltage. Refer to [2] for a detailed description of this technique.
The power stage of the PFC is a conventional boost converter, connected to the 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 connected to the DC rail, in series to the output
electrolytic capacitor, in order to improve the efficiency during low line operation.
Additionally, the splitting into two of the output capacitors (C6 and C7) means that the AC
current is mainly managed by the film capacitor C7, making the electrolytic cheaper
because it only has to bear the DC part.
Doc ID 15796 Rev 2
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