AN2521
Application note
19 V - 75 W laptop adapter with tracking boost PFC
pre-regulator, using the L6563 and L6668
Introduction
This application note describes the characteristics and features of a 75 W wide range input
mains and power-factor-corrected ac-dc adapter evaluation board. Its electrical specification
is tailored to a typical high-end portable computer power adapter. The distinctive attributes
of this design are the very low standby input consumption (< 0.3 W at 265 V), the excellent
global efficiency (> 85%) for a two stage architecture and the low cost.
Figure 1.
October 2007
L6668 and L6563-75W adapter evaluation board (EVAL6668-75W)
Rev 1
1/33
www.st.com
Contents
AN2521
Contents
1
Main characteristics and circuit description . . . . . . . . . . . . . . . . . . . . . 4
2
Test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3
4
2.1
Efficiency measurements at full load, tracking boost option (TBO) . . . . . . 8
2.2
Harmonic content measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Functional check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1
Normal operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.2
Standby and no-load operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.3
Over current and short circuit protection . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.4
Overvoltage and open loop protection . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
EVAL6668-75W: thermal map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.1
Thermal protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.2
Thermal map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5
Conducted emission pre-compliance test . . . . . . . . . . . . . . . . . . . . . . 22
6
Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7
PFC coil specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8
9
2/33
7.1
General description and characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.2
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7.3
Electrical schematic and winding characteristics . . . . . . . . . . . . . . . . . . . 28
7.4
Mechanical aspect and pin numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Transformer specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.1
General description and characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.2
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.3
Electrical diagram and winding characteristics . . . . . . . . . . . . . . . . . . . . . 30
8.4
Mechanical aspect and pin numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
AN2521
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.
L6668 and L6563-75W adapter evaluation board (EVAL6668-75W) . . . . . . . . . . . . . . . . . . 1
Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
EVAL6668-75W global efficiency measurements at full load . . . . . . . . . . . . . . . . . . . . . . . . 8
L6563 tracking boost and voltage feed-forward blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
EVAL6668-75W PFC output voltage vs. ac input voltage . . . . . . . . . . . . . . . . . . . . . . . . . 10
PFC efficiency with and without TBO function at full load . . . . . . . . . . . . . . . . . . . . . . . . . 10
Flyback converter efficiency with and without TBO function at full load . . . . . . . . . . . . . . . 10
Comparison between the global efficiency with and without TBO . . . . . . . . . . . . . . . . . . . 11
EVAL6668-75W compliance to EN61000-3-2 standard @230 V, 50 Hz - full load . . . . . . 11
EVAL6668-75W compliance to JEIDA-MITI standard @100 V, 60 Hz - full load . . . . . . . . 11
EVAL6668-75W compliance to EN61000-3-2 standard @230 V, 50 Hz - half load . . . . . 12
EVAL6668-75W compliance to JEIDA- MITI standard @100 V, 60 Hz - half load . . . . . . . 12
EVAL6668-75W input current waveform @100 V, 60 Hz - full load . . . . . . . . . . . . . . . . . . 12
EVAL6668-75W input current waveform @230 V, 50 Hz - full load . . . . . . . . . . . . . . . . . . 12
EVAL6668-75W flyback stage waveforms @115 V, 60 Hz-full load. . . . . . . . . . . . . . . . . . 13
EVAL6668-75W flyback stage waveforms @230 V, 50 Hz-full load. . . . . . . . . . . . . . . . . . 13
Adapter circuit primary side waveforms 265 V, 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
EVAL6668-75 W no-load operation waveforms @90 V, 60 Hz . . . . . . . . . . . . . . . . . . . . . 14
EVAL6668-75 W no-load operation waveforms @265 V, 50 Hz . . . . . . . . . . . . . . . . . . . . 14
EVAL6668-75 W transition full load-to-no load at 265 V, 50 Hz . . . . . . . . . . . . . . . . . . . . . 15
EVAL6668-75 W transition no load-to-full load at 265 V, 50 Hz . . . . . . . . . . . . . . . . . . . . . 15
EVAL6668-75 W short circuit at full load & 230 Vac-50 Hz . . . . . . . . . . . . . . . . . . . . . . . . 17
EVAL6668-75 W short circuit removal at full load & 230 Vac-50 Hz . . . . . . . . . . . . . . . . . 17
EVAL6668-75 W short circuit at no-load & 230 Vac-50 Hz . . . . . . . . . . . . . . . . . . . . . . . . 18
EVAL6668-75 W short circuit removal at no-load & 230 Vac-50 Hz. . . . . . . . . . . . . . . . . . 18
EVAL6668-75W Open loop at 115 Vac-60 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Thermal map at 115 Vac-60 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Thermal map at 230 Vac-50 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
CE peak measure at 100 Vac and full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
CE peak measure at 230 Vac and full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Mechanical aspect and pin numbering of PFC coil. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Winding position on coil former. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Mechanical aspect and pin numbering of flyback transformer . . . . . . . . . . . . . . . . . . . . . . 32
3/33
Main characteristics and circuit description
1
AN2521
Main characteristics and circuit description
The main characteristics of the SMPS are listed here below:
●
Universal input mains range: 90 - 264 Vac, 45 −65 Hz
●
Output voltages: 19 V @ 4 A continuous operation
●
Mains harmonics: in accordance with EN61000-3-2 class-D
●
Standby mains consumption: less than 0.3 W @ 265 Vac
●
Overall efficiency: greater than 85%
●
EMI: in accordance with EN55022-class B
●
Safety: in accordance with EN60950
●
PCB single layer: single side, 70 µm, CEM-1, 78 x 174 mm, mixed PTH/SMT
The circuit is made up of two stages: a front-end PFC using the L6563 and a flyback
converter based on the L6668. The electrical schematic is shown in Figure 2.
The flyback stage works as the master stage and therefore is dedicated to controlling circuit
operation, including standby and protection functions. Additionally, it switches the PFC stage
on and off the by means of a dedicated pin on the control IC, thus helping to achieve good
efficiency even at light load. The input EMI filter is a classic Pi-filter, 1-cell for differential and
common mode noise. An NTC in series with the PFC output capacitor limits the inrush
current produced by the charging of the capacitor at plug-in.
The purpose of the PFC stage is to reduce the harmonic content of the input current to be
within the limits imposed by European norm EN61000-3-2. Additionally, it provides a
regulated dc bus used by the downstream converter.
The PFC controller is the L6563 (U1), working in transition mode. It integrates all functions
needed to control the PFC as well as an interface to the master converter. Its power stage
topology is a conventional boost converter, connected to the output of the rectifier bridge. It
includes the coil L2, the diode D3, the capacitor C6 and the power switch Q2, a power
MOSFET.
The secondary winding of L2 (pins 8-3) provides the L6563 with information about the core
demagnetization of the PFC coil, needed by the controller for TM (transition mode)
operation. The divider R7, R12 and R18 provides the L6563 with the instantaneous input
voltage information that is used to modulate the boost current, and to derive additional
information such as the average value of the ac line, which is used by the VFF (voltage feedforward) function. The divider R2, R6, R8, R9 is dedicated to sensing the output voltage and
feeds the information to the error amplifier, while the divider R3, R5, R11, R19, directly
connected to the output voltage, is dedicated to protecting the circuit in case of voltage loop
failure. To maximize overall efficiency, the PFC makes use of the so-called "tracking boost
option" (TBO). With this function implemented the dc output voltage of the PFC changes
proportionally with the mains voltage. The L6563 achieves this functionality by adding a
resistor (R30) connected to the dedicated TBO pin (#6).
The PFC is switched on and off by a switch (Q1) on the VCC pin of the L6563, which is
activated by the PFC-STOP pin of the L6668. The PFC-STOP pin is intended to stop the
PFC controller at light load by cutting its supply. This happens when the COMP pin on the
L6668 controller goes below 2.2V.
The downstream converter, acting as the master stage, is managed by the L6668 IC (U2), a
current mode controller. The 65 kHz nominal switching frequency has been chosen to
4/33
AN2521
Main characteristics and circuit description
achieve a compromise between the transformer size and the harmonics of the switching
frequency, thereby optimizing the input filter size and the total solution cost. The power
MOSFET is a standard, inexpensive 800 V component housed in a TO-220FP package,
requiring a small heat sink. The transformer is the layer type, using the standard ferrite core
EER35. The transformer is manufactured by TDK and designed in accordance with
EN60950. The reflected voltage is ~130 V, providing sufficient room for the leakage
inductance voltage spike while maintaining a margin for the reliability of the power MOSFET.
The rectifier D8 and the Transil D4 clamp the peak of the leakage inductance voltage spike
at turn-off of the power MOSFET.
The controller L6668 offers maximum flexibility by integrating all the functionality needed for
high performance SMPS control with a minimum component count. A new feature
embedded in the device is a high voltage current source used at start-up which draws
current directly from the dc bus and charges capacitor C33. After the voltage on C33 has
reached the L6668 turn-on threshold and the circuit starts to operate, the controller is
powered by the transformer via the auxiliary winding and diode D11. After start-up, the HV
current source is deactivated, saving power during normal operation and allowing very good
circuit efficiency during standby.
The L6668 utilizes a Current Mode control system, so the current flowing through the
primary winding is sensed by R52 and R53 and is then fed into pin #12 (ISEN). Resistor
R41 connected between pin #12 (ISEN) and pin #15 (S_COMP) provides the correct slope
compensation to the current signal, necessary for correct loop stability in CCM mode at duty
cycles greater than 50%. The circuit connected to pin #7 (DIS) provides over-voltage
protection in case of feedback network failure, while the thermistor R58 provides for a
thermal protection of the power MOSFET (Q5). This pin is also connected to the
PWM_LATCH pin of the L6563 which is dedicated to stopping activity of the flyback
converter in case of PFC loop failure that could be damaging to the circuit. To definitively
latch this state, the internal circuitry of the L6668 monitors the VCC and periodically
reactivates the HV current source to supply the IC. After OVP detection and L6668 Disable
intervention, circuit operation can be resumed only after disconnection of the mains plug.
The switching frequency is programmed by the RC connected to pin #16 (RCT) and in case
of reduced load operation the controller can decrease the operating frequency via pin #13
(STBY) and resistor R42, proportionate with the load consumption. The resistor divider R60
and R61 connected to pin #9 (SKIPADJ) allows setting of the initial L6668 threshold to Burst
Mode functionality when the power supply is lightly loaded. Additional functions embedded
in the L6668 are the programmable soft-start and a 5 V reference, available externally.
Circuit regulation is achieved by modulating the voltage on the COMP pin (#10), by means
of the optocoupler U3. Also connected to the COMP pin is the Q6, Q8, R44, R62, C42 and
D13 network, which is dedicated to driving ISEN over its hiccup mode threshold in case of
overload or short condition. In this case the device will be shut down and its consumption
will decrease almost to pre-start-up level. The device will resume operation as soon as the
VCC voltage has dropped below the VCC restart level. Thus a reliable hiccup mode is
invoked until the short is removed. A short on-time and long off-time of the hiccup mode are
obtained allowing the average current flowing in the secondary side components to be kept
at a safe level, avoiding consequent catastrophic failures due to their overheating.
Output regulation is done by means of two loops, a voltage and a current loop working
alternately. A dedicated control IC, the TSM1014, has been used. It integrates two
operational amplifiers and a precise voltage reference. The output signal of the error
amplifiers drives optocoupler SFH617A-4 to transfer the information to the primary side and
achieve the required insulation of the secondary side. The output rectifier D7 is a dual
common-cathode Schottky diode. The output rectifier has been selected according to the
5/33
Main characteristics and circuit description
AN2521
calculated maximum reverse voltage, forward voltage drop and power dissipation. The
snubber, made up of R14, R66 and C8, damps the oscillation produced by the diode D7. A
small LC filter has been added on the output in order to filter the high frequency ripple.
6/33
90-264Vac
1
2
3
C21
470N
R18
51K
R12
3M3
R7
3M3
C15
1uF
R15
RES
C9
100N
C23
RES
R17
62K
R34
270K
R26
120K
C19
2N2
C3
470NF-X2
C25
220PF
R30
22K
C2
2N2
C1
2N2
7
6
5
4
3
2
1
R33
10K
C26
22N
PFC-OK
TBO
VFF
CS
MULT
RUN
ZCD
GND
GD
VCC
~
PWM-LATCH
8
9
10
11
12
13
14
D2
GBU4J
PWM-STOP
R9
75K-1%
U1
L6563
COMP
INV
R8
75K-1%
C4
470NF-X2
L1
HF2826-253Y1R2-T01
_
R56
4K7-1%
R50
1K0
C32
100N
Q3
RES
C38
470PF
R25
470R
R21
RES
C11
RES
8
OTP PROT
C20
10N
R23
27R
D6
RES
C14
220N
C5
470N-400V
6
D1
D10
LL4148
R29
RES
R24
100K
R59
24K
R58
M57703
C33
22uF-50V
R4
68K
3
5
C40
100N
8
7
6
5
4
3
2
1
1
R60
56K
VREF
DIS
N.C.
VCC
OUT
GND
HVS
HV
Q2
STP9NK50ZFP
R16
10K
2
C41
10N
SKIP_ADJ
COMP
SS
ISEN
STBY
PFC_STOP
JP7
RES
R61
33K
RCT
S_COMP
R28
2K2
D9
BZV55-C8V2
U2
L6668
R10
RES
9
10
11
12
13
14
15
16
R31
4K7
C39
4N7
C37
82N
C30
2N2-5%
R41
10K
R6
1M0-1%
R2
1M0-1%
C22
2u2-25V
C6
100uF-450V
R1
NTC 10R-S236
Q1
BC857C
D3
STTH2L06
R27
0R33
1N4005
L2
SRW25CQ-T03H102
D13
LL4148
C34
100PF
R42
8K2
R37
10K-1%
R32
RES
R57
100R
R19
36K
R11
2M2
R5
2M2
R3
2M2
C42
10uF-50V
R62
3K3
Q8
BC847C
R51
2K2
R46
47R
D12
LL4148
Q7
RES
R43
4R7
R72
0R0
D15
RES
D5
BZV55-B30
R44
47K
Q6
BC857C
R52
0R39
R47
100K
R71
RES
C27
47uF-50V
D11
BAV103
R53
0R39
R64
43K-1%
Q5
STP10NK80ZFP
R73
62K
R13
RES
R38
RES
D14
LL4148
Q4
RES
R35
2R7
C28
RES
5-6
2-3
D4
1.5KE250A
D8
STTH108A
C10
RES
R14
3R9
U3
SFH617A-4
T1
SRW32EC-T01H114
C24
2N2 - Y 2
10-11
D7
STPS20H100CFP
C12
15-16
C8
1N0-200V
C7
2N2 - Y 2
4
~
F1
FUSE 4A
1
3
+
J1
INPUT CONN.
1000uF-25V ZL
C31
RES
C29
RES
R40
RES
C35
270N
R45
2K2
U4
TS3431IZ-RES
R54
47K
R36
1K8
C16
R66
3R9
1000uF-25V ZL
R48
4K7-1%
C44
100N
R49
24K-1%
R68
120K-1%
R39
56K-1%
R22
R015-1W - MSR1
R20
20K
C13
R67
6K2-1%
L3
TSL0706 - 1R5-4R3
100uF-25V YXF
R65
22K
4
3
2
1
R69
1K0
CV-
CC+
CC-
8
5
6
7
C43
2N2
CV_OUT
GND
CC_OUT
VCC
19V@4A
CON2-IN
2
1
J2
TSM1014
V_REF
U5
C17
100N
C36
100N
R55
22R
Figure 2.
2
AN2521
Main characteristics and circuit description
Electrical diagram
g
7/33
Test results
AN2521
2
Test results
2.1
Efficiency measurements at full load, tracking boost option
(TBO)
The following table and diagrams show the single converter and overall efficiency measured
at different input voltages. These measurements are performed with nominal load (4 A).
Table 1.
Efficiency measurements at full load using the TBO function
Vinac
Efficiency
PFC
dc-dc
Global
90 [V]
93.63%
89.83%
84.11%
115 [V]
95.62%
89.07%
85.17% (1)
230 [V]
97.84%
89.81%
87.87% (1)
265 [V]
97.53%
89.06%
86.86%
1. Compliant to CEC, EU-COC, regulation. In Table 1 and Figure 3 the single converter efficiency
measurement is shown. Thanks to the very good efficiency of any single block the overall efficiency is very
high too, especially if we compare this data with similar converters using a double stage and a flyback
topology as downstream converter.
Figure 3.
EVAL6668-75W global efficiency measurements at full load
90%
OVERALL EFFICIENCY
89%
WITH TBO
88%
87%
86%
85%
84%
83%
82%
81%
80%
90
Table 2.
115
Vin [Vrms]
230
265
ENERGY STAR compliance
ENERGY STAR efficiency
Vinac
1A
2A
3A
4A
Average
115 [V]
85.26%
86.32%
86.28%
85.17%
85.75%
230 [V]
83.4%
85.2%
86.74%
87.87%
85.8%
In Table 2 the ENERGY STAR efficiency measurements are shown. The average of the two
mains voltage inputs in four different load conditions is compliant with the target requirement
(better than 84%).
8/33
AN2521
Test results
To achieve optimal efficiency the PFC stage implements the tracking boost function. It
consists of a PFC output voltage that follows the input voltage. Typically, in traditional PFC
stages, the dc output voltage is regulated at a fixed value (typically 400 volts) but in some
applications, such as this one using a flyback as the downstream converter, it could be
advantageous to regulate the PFC output voltage with the tracking boost or "follower boost"
approach. In this way the circuit with the TBO function provides improved efficiency and,
thanks to the lower differential voltage across the boost inductor, the value of L2 can be
reduced as compared to the same circuit without the TBO function. In the present case a
400 µH inductor has been used, while with a fixed output voltage PFC working at a similar
operating frequency, a 700 µH inductor is required.
To achieve the TBO function on the L6563, a dedicated input of the multiplier is available on
TBO pin #6. This function can be implemented by simply connecting a resistor (RT) between
the TBO pin and ground.
Figure 4.
L6563 tracking boost and voltage feed-forward blocks
COM
Vout
Rectified mains
2
IR
current
reference
R1
2.5V
INV
+
- E/A
1
MULTIPLIER
1/V
2
R5
9.5V
ITBO
IR
+
1:1
CURRENT
"ideal"
diode
3
3V
R2
L6563
L6563A
R6
6
5
TBO
ITBO
MUL
9.5V
RT
VFF
CF
RF
The TBO pin presents a dc level equal to the peak of the MULT pin voltage and is then
representative of the mains RMS voltage. The resistor defines the current, equal to
V(TBO)/RT, which is internally mirrored 1:1 and sunk from the INV pin (pin 1) input of the
error amplifier. In this way, when the mains voltage increases, the voltage at the TBO pin will
increase as well, and so will the current flowing through the resistor connected between
TBO and GND. A larger current will then be sunk by the INV pin and the output voltage of
the PFC pre-regulator will be forced higher. Obviously, the output voltage will move in the
opposite direction if the input voltage decreases.
To avoid an unwanted rise in output voltage should the mains voltage exceed the maximum
specified value, the voltage at the TBO pin is clamped at 3 V. By properly selecting the
multiplier bias it is possible to set the maximum input voltage above which input-to-output
tracking ends and the output voltage becomes constant. If this function is not used, the pin
should be left open; the device will regulate at a fixed output voltage.
9/33
Test results
AN2521
Figure 5.
EVAL6668-75W PFC output voltage vs. ac input voltage
PFC OUTPUT VOLTAGE [V]
417
384
384
351
351
318
285
252
242
219
218
186
80
130
180
Vin [Vrms]
230
280
In Figure 5 we can see that the PFC output voltage variation vs. the ac input voltage (i.e. the
input voltage for the flyback stage) is dependent on the input mains voltage, but its range is
narrower than a wide range input. Thus the design of the flyback converter is not completely
optimized as with a standard PFC delivering a stable 400 V output, but its design is much
simpler than that of a wide range flyback. Additionally, the PFC converter using the TBO,
with its lower differential voltage across the inductor and lower current ripple, will have lower
RMS current and therefore better efficiency at low mains, where normally the efficiency of
typical PFCs is lower. The result is a global efficiency of the circuit that will be higher than
that of a fixed output voltage one circuit, especially at lower mains. Most of the power
dissipation will not be concentrated on the PFC only but will be shared with the flyback.
Therefore, there will not be thermal hotspots and the reliability of the circuit will be improved.
This is confirmed in the diagram in Figure 6, where the efficiency of the PFC has been
measured both with the active TBO function and without it. As shown, at low input mains the
circuit has an efficiency improvement better than 2 percent. As the input mains voltage
increases the switching losses become more significant and the fixed output voltage PFC
appears more efficient.
Figure 6.
PFC efficiency with and without
TBO function at full load
Figure 7.
95%
WITHOUT TBO
FLYBACK STAGE EFFICIENCY
PFC STAGE EFFICIENCY
100%
99%
98%
Flyback converter efficiency with
and without TBO function at full
load
WITH TBO
97%
96%
95%
94%
93%
92%
91%
90%
90
115
Vin [Vrms]
230
265
94%
400 Vdc FIXED I/P VOLTAGE
93%
WITH TBO
92%
91%
90%
89%
88%
87%
86%
85%
90
115
230
Vin [Vrms]
265
Using the TBO function even the flyback converter efficiency is very good, as shown in
Figure 7 where it is compared with the efficiency of the same converter powered by a fixed
10/33
AN2521
Test results
400 V input voltage. It can be observed that an improvement is achieved at 90 Vac and 230
Vac mains.
As a final measurement, the comparison between the global efficiency with and without
TBO is shown in Figure 8, confirming the previous measurements.
Figure 8.
Comparison between the global efficiency with and without TBO
OVERALL EFFICIENCY
90%
89%
WITHOUT TBO
88%
WITH TBO
87%
86%
85%
84%
83%
82%
81%
80%
90
2.2
115
Vin [Vrms]
230
265
Harmonic content measurement
One of the main purposes of a PFC pre-conditioner is to correct the input current distortion,
decreasing the harmonic contents below the limits of the relevant regulations. Therefore, the
board has been tested according to the European rule EN61000-3-2 Class-D and Japanese
rule JEIDA-MITI Class-D, at full load and 50% of output rated load, at both nominal input
mains voltages.
As demonstrated in the illustrations below, the circuit is capable of reducing the harmonics
well below the limits of both regulations from full load down to light load. Because the
maximum input power of the board is close to the limit of 75 W, to demonstrate the correct
behavior of the circuit it has been tested also a 37 W (half load). Of course, no current
regulation requires meeting any limit at these power levels.
Figure 9.
EVAL6668-75W compliance to
EN61000-3-2 standard @230 V, 50
Hz - full load
Measured value
Figure 10. EVAL6668-75W compliance to
JEIDA-MITI standard @100 V, 60 Hz
- full load
EN61000-3-2 Class-D limits
Measured value
JEIDA-MITI Class-D limits
1
0.1
Harmonic Current [A]
Harmonic Current [A]
1
0.01
0.001
0.1
0.01
0.001
0.0001
0.0001
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Harmonic Order [n]
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Harmonic Order [n]
11/33
Test results
AN2521
Figure 11. EVAL6668-75W compliance to
EN61000-3-2 standard @230 V, 50
Hz - half load
Measured value
Figure 12. EVAL6668-75W compliance to
JEIDA- MITI standard @100 V, 60 Hz
- half load
EN61000-3-2 Class-D limits
Measured value
JEIDA-MITI Class-D limits
1
Harmonic Current [A]
Harmonic Current [A]
1
0.1
0.01
0.001
0.1
0.01
0.001
0.0001
0.0001
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Harmonic Order [n]
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
Harmonic Order [n]
On the bottom side of each diagram the total harmonic distortion and power factor have
been measured as well. The values in all conditions give a clear idea of the correct
functioning of the PFC even if the tracking boost option has been implemented.
For user reference, input current and voltage waveforms at the nominal input mains voltages
and full load are shown below.
Figure 13. EVAL6668-75W input current
waveform @100 V, 60 Hz - full load
CH1: input mains voltage
CH2: input mains current
12/33
Figure 14. EVAL6668-75W input current
waveform @230 V, 50 Hz - full load
CH1: input mains voltage
CH2: input mains current
AN2521
Functional check
3
Functional check
3.1
Normal operation
Figure 15 and Figure 16 display some waveforms of the flyback stage during steady-state
operation of the circuit at full load and nominal input voltage ranges. Under full load
conditions the L6668 switching frequency has been set to 65 kHz in order to achieve good
efficiency and to limit the switching noise.
It's possible to note that the CH3 relevant to the output voltage of the PFC circuit shows the
tracking boost function setting at a different PFC output voltage (247 / 348 volts), which is
dependent on the mains input voltage as mentioned on the previous page.
Figure 15. EVAL6668-75W flyback stage
waveforms @115 V, 60 Hz-full load
CH1: input mains voltage
CH2: input mains current
CH3: PFC output voltage
Figure 16. EVAL6668-75W flyback stage
waveforms @230 V, 50 Hz-full load
CH1: input mains voltage
CH2: input mains current
CH3: PFC output voltage
In Figure 17 the drain voltage waveforms and the measurement of the peak voltage at full
load and maximum mains input voltage are shown.
The maximum voltage peak in this condition is 676 V, which ensures reliable operation of the
power MOSFET with a good margin against the maximum BVDSS.
13/33
Functional check
AN2521
Figure 17. Adapter circuit primary side waveforms 265 V, 50 Hz
CH1: Q7 drain voltage
CH2: L6668 Vpin #12 (ISEN)
3.2
Standby and no-load operation
Figure 18. EVAL6668-75 W no-load operation
waveforms @90 V, 60 Hz
CH1: Q7 drain voltage
CH2: L6668 COMP (pin #10)
CH3: L6668 VCC (pin #5)
Figure 19. EVAL6668-75 W no-load operation
waveforms @265 V, 50 Hz
CH1: Q7 drain voltage
CH2: L6668 COMP (pin #10)
CH3: L6668 VCC (pin #5)
In Figure 18 and Figure 19, some no-load waveforms of the circuit are shown. As illustrated,
the L6668 works in burst mode to achieve optimal efficiency. The burst mode threshold can
be adjusted by setting the divider connected to the SKIPADJ pin (#9). When the voltage at
the COMP pin falls 50 mV below the voltage on the SKIPADJ pin, the IC is shut down and
consumption is reduced. The chip is re-enabled as the voltage on the COMP pin exceeds
the voltage on the threshold set by pin 9 with its hysteresis. Additionally, in order to achieve
the best efficiency during light load operation the PFC stage is turned off. In fact, the L6668
pin #14 (PFC_STOP) is dedicated to enabling or disabling PFC operation according to the
14/33
AN2521
Functional check
output load level. This pin is intended to drive the base of a PNP transistor in systems
including a PFC pre-regulator, to stop the PFC controller at light load by cutting its supply.
Pin #14 (PFC_STOP), while normally low, opens if the voltage on the COMP pin is lower
than 2.2 V, and returns low when the voltage on the COMP pin exceeds 2.7 V. Whenever the
IC is shut down, either latched (DIS > 2.2 V, ISEN > 1.5 V) or not latched (UVLO, SKIPADJ <
0.8), the pin is open as well. In Figure 19, the VCC value is also given, showing that the IC is
powered with a good margin with respect to the L6668 turn-off threshold (9.4 V), avoiding
any spurious turn-off possibilities that could affect the output voltage stability.
In Table 3, the power consumption from the mains during no-load operation is shown. As
can be observed, thanks to the L6668 standby functionality the input power constantly
remains well below 300 mW. Therefore, all mandatory or voluntary regulations currently
applicable or that will become effective in the near future can be respected using this
chipset.
Table 3.
Input power at no-load vs. mains voltage
Vin [Vrms]
Input power [W]
90
0.126
115
0.146 (1)
230
0.268 (1)
265
0.282
1. Compliant to CEC, EU-COC, Energy Star
Figure 20. EVAL6668-75 W transition full load- Figure 21. EVAL6668-75 W transition no loadto-no load at 265 V, 50 Hz
to-full load at 265 V, 50 Hz
CH1: Q2 drain voltage
CH2: L6668 SOFT START - pin #11
CH3: output voltage
CH4: L6668 VCC (pin #5)
CH1: Q2 drain voltage
CH2: L6668 SOFT START - pin #11
CH3: output voltage
CH4: L6668 VCC (pin #5)
In Figure 20 and Figure 21, the transitions from full load to no-load and vice-versa at
maximum input voltage have been checked. The maximum input voltage has been chosen
for the above illustrations because it is the most critical input voltage for transition. In fact, at
no-load, the burst pulses have a lower repetition frequency and the VCC could drop, causing
restart cycles of the controller. Additionally, there is a wider range variation for the input
15/33
Functional check
AN2521
voltage to the flyback converter as a result of the PFC turning on or off. As the figures show,
both transitions are clean and there is no output voltage, VCC dip or restarting attempt that
could affect proper power supply operation.
The input power consumption of the board has also been checked at light load conditions,
simulating an adapter powering a laptop PC during power-saving operation. The results are
shown in Table 4, 5 and 6 below, where the low load efficiency with standard inputs of 115 V
and 230 V is calculated.
Table 4.
Light load efficiency (0.5 W)
Vinac [Vrms]
Pout [W]
Pin [W]
Efficiency
115
0.52
0.75 (1)
68.67%
0.52
(1)
58.52%
230
0.88
1. Compliant to US Executive order 13221 “1W _Standby“
Table 5.
Light load efficiency (1.2 W)
Vinac [Vrms]
Pout [W]
Pin [W]
Efficiency
115
1.2
1.55
77.86%
230
1.2
1.71
70.35%
Table 6.
Light load efficiency (2.4 W)
Vinac [Vrms]
Pout [W]
Pin [W]
Efficiency
115
2.41
2.93
82.14%
230
2.4
3.14
76.56%
As visible in Table 4, 5 and 6, the input power consumption is always very low and the
efficiency remains significantly high even at output power levels where the power supply
efficiency normally drops. This is achieved thanks to the burst mode adjustable threshold of
the L6668 SKIPADJ pin and the PFC management by the PFC_STOP pin, as previously
described.
3.3
Over current and short circuit protection
An important function of any power supply is its ability to survive instances of output
overload or short circuit, avoiding any consequent failure. Additionally, the power supply
must be compliant with safety rules which require that the components will not melt or burnout in fault conditions. It’s common to find circuits with good protection capability against
load shorts but which do not survive dead shorts such as those of an output electrolytic
capacitor or a secondary rectifier, or in cases of transformer saturation. Moreover, in cases
of a shorted rectifier the equivalent circuit changes and the energy are delivered even during
the ON time, as in forward mode. In this evaluation board the over-current is managed by
U5, a CC/CV controller. Inside the IC there is a reference and two Or-end operational
amplifiers, one dedicated to act as the error amplifier of the voltage loop and the other
dedicated to act as the error amplifier of the current loop. If the output current exceeds the
programmed value, the current loop error amplifier takes over and, via the optocoupler,
16/33
AN2521
Functional check
controls the voltage at the COMP pin of the L6668, thus regulating the output current. In
case of a dead short, the current cannot be limited effectively by U5 because it will be
unpowered. Therefore, additional, efficient protection circuitry on the primary side will be
needed. In this board the voltage at the ISEN pin of the L6668 is sensed and if it exceeds
the VISENdis threshold the controller is forced to work in hiccup mode. In this way the
controller stops operation and will remain in the OFF state until the voltage across the VCC
pin decreases to a level below the UVLO threshold. It will then attempt to restart, but without
success if the secondary short has not been removed. This provides a low frequency hiccup
working mode, limiting the current flowing on the secondary side and thus preventing the
power supply from overheating and failing.
Figure 22 shows the circuit behavior during short circuit. Observe that the L6668 stops
switching, the VCC voltage drops until it reaches the UVLO threshold. Then the IC
decreases its consumption, thus increasing the duration of the OFF time, and avoiding high
dissipation on the secondary side under short conditions. The soft start capacitor will also
be discharged. At this point, the HV start-up pin recharges the VCC capacitor and, as soon
the turn-on threshold is reached, the circuit attempts to restart but it will cease operation
within a few milliseconds, repeating the sequence just described. The restart attempt will be
repeated indefinitely until the short is removed.
Figure 23, instead, shows the sequence of operation in short circuit when the short is
removed. As the figure illustrates, a new start-up sequence takes place and the circuit
resumes normal operation after a soft-start cycle.
Figure 22. EVAL6668-75 W short circuit at full Figure 23. EVAL6668-75 W short circuit
load & 230 Vac-50 Hz
removal at full load & 230 Vac-50 Hz
CH1: Q2 drain voltage
CH2: SOFT START voltage - pin #11
CH3: output voltage
CH4: VCC
CH1: Q2 drain voltage
CH2: SOFT START voltage - pin #11
CH3: output voltage
CH4: VCC
Thanks to the TSM1014 and the HV current source of the L6668, the fault protection
sequences described in Figure 22 and Figure 23 do not change significantly for any other
input voltage, above all not in the input voltage range of the board.
The protection described previously works correctly even in cases where the output short is
applied during standby or no load operations. The L6668 protects the circuit via the
sequences that has been described for the full load operation, and the circuit resumes
17/33
Functional check
AN2521
correct operation when the short is removed. In Figure 24 and Figure 25 both sequences
are captured during 230 Vac operation but they do not change significantly over the input
mains range.
Figure 24. EVAL6668-75 W short circuit at no- Figure 25. EVAL6668-75 W short circuit
load & 230 Vac-50 Hz
removal at no-load & 230 Vac-50 Hz
CH1: Q2 drain voltage
CH2: SOFT START voltage - pin #11
CH3: output voltage
CH4: VCC
3.4
CH1: Q2 drain voltage
CH2: SOFT START voltage - pin #11
CH3: output voltage
CH4: VCC
Overvoltage and open loop protection
The EVAL6668-75W board implements two different open loop protections: one for the PFC
and another for the flyback stage.
The PFC controller L6563 is equipped with an OVP, monitoring the current flowing through
the compensation network and entering the error amplifier (pin COMP, #2). When this
current reaches about 18 µA the output voltage of the multiplier is forced to decrease, thus
reducing the energy drawn from the mains. If the current exceeds 20 µA, the OVP is
triggered (dynamic OVP), and the external power transistor is switched off until the current
falls below approximately 5 µA. However, if the overvoltage persists (e.g. if the load is
completely disconnected), the error amplifier will eventually saturate low, triggering an
internal comparator (static OVP) which will keep the external power switch turned off until
the output voltage returns to a point near the regulated value.
The OVP function described above is capable of handling "normal" overvoltage conditions,
i.e. those resulting from an abrupt load/line change or occurring at start-up. It cannot handle
the overvoltage generated, for instance, when the upper resistor of the output divider fails
open. The voltage loop can no longer read the information on the output voltage and will
force the PFC pre-regulator to work at maximum ON time, causing the output voltage to rise
uncontrollably.
A pin on the L6563 (PFC_OK, #7) has been provided for additional monitoring of the output
voltage with a separate resistor divider (R3, R5, R11 high, R19 low, see Figure 1.and 2).
This divider is selected so that the voltage at the pin reaches 2.5 V if the output voltage
18/33
AN2521
Functional check
exceeds a preset value, usually larger than the maximum Vo that can be expected, including
also overshoots due to worst-case load/line transients.
In this case, VO = 400 V, Vox = 460 V. Select: R3 + R5 + R11 = 6.6 MΩ. Three resistors in
series have been chosen according to their voltage rating.
Thus: R19 = 6.6 MΩ · 2.5 / (460-2.5) = 36 kΩ.
When this function is triggered, the gate drive activity is immediately stopped, the device is
shut down, its quiescent consumption is reduced below 250 µA and the condition is latched
as long as the supply voltage of the IC is above the UVLO threshold. At the same time the
pin PWM_LATCH (pin #8) is asserted high. The PWM_LATCH is an open source output
capable of delivering 3.7 V minimum with a 0.5 mA load, intended for tripping a latched
shutdown function of the PWM controller IC in the cascaded dc-dc converter, so that the
entire unit is latched off. To restart the system it is necessary to recycle the input power, so
that the VCC voltages of both the L6563 and the PWM controller go below their respective
UVLO thresholds.
The PFC_OK pin doubles its function as a not-latched IC disable: a voltage below 0.2 V will
shut down the IC, reducing its consumption below 1 mA. In this case both PWM_STOP and
PWM_LATCH keep their high impedance status. To restart the IC simply let the voltage at
the pin go above 0.26 V.
Note that this function offers complete protection against not only feedback loop failures or
erroneous settings, but also against a failure of the protection itself. If a resistor in the
PFC_OK divider fails short or open, or the PFC_OK (#7) pin is floating, it will result in the
shutting down of the L6563 and stopping of controller operation of the flyback stage.
Figure 26. EVAL6668-75W Open loop at 115 Vac-60 Hz - full load
An open loop event is captured in Figure 26. Note the protection intervention stopping the
operation of the L6563 and the activation of the PWM_LATCH pin that is connected to the
L6668 pin #7 (DIS). This function of the L6668 is a latched device shutdown. Internally the
pin connects a comparator which shuts the IC down and brings its consumption to a value
just higher than before start-up, when the voltage on the pin exceeds 2.2 V. The information
is latched and it is necessary to recycle the input power to restart the IC. The latch is
removed as the voltage on the VCC pin goes below the UVLO threshold.
19/33
EVAL6668-75W: thermal map
AN2521
The flyback stage is also protected against open loop conditions that lead to loss of control
of the output voltage. A divider connected to the auxiliary winding of the transformer is also
connected to the L6668 pin #7 (DIS) and, in case of excessively high output voltage
resulting from loop failure, provides for the triggering of the internal comparator connected to
that pin. In this case operation of the L6563 will cease because the L6668 will stop the PFC
stage operation via the PFC_STOP pin. The VCC powering both the ICs will be maintained
by the HV start-up generator of the L6668. To restart the operation, it will be necessary to
unplug and re-plug the mains, to unlatch the L6668.
4
EVAL6668-75W: thermal map
4.1
Thermal protection
The EVAL6668-75W is also equipped with thermal protection of the flyback's power
MOSFET (Q5). Its temperature is sensed using the NTC thermistor R58 connected to the
L6668 pin #7 (DIS). If the temperature of the heat sink rises above the maximum allowed
level (80 - 85 °C), the threshold of the internal comparator will be exceeded and the L6668
latched as in the case of open loop. To restart the operation of the circuit, it will be
necessary to unplug and re-plug the mains.
4.2
Thermal map
In order to check the reliability of the design, thermal mapping has been performed using an
infrared camera. In Figure 27 and 28, the thermal measurements on the key components at
nominal input voltage are shown. The correlation between the measurement points and
components for both thermal maps is indicated in Table 7 below. The ambient temperature
during both measurements was 27 °C. All other components on the board work within the
temperature limits, ensuring reliable long-term operation of the power supply.
Figure 27. Thermal map at 115 Vac-60 Hz - full load
20/33
AN2521
EVAL6668-75W: thermal map
Figure 28. Thermal map at 230 Vac-50 Hz - full load
Table 7.
Measured temperature table @115 Vac and 230 Vac - full load
Point
Component
Temperature @115 Vac
Temperature @230 Vac
A
D2
59.6 °C
52.9 °C
B
Q2
59.9 °C
54.0 °C
C
D4
101 °C
100 °C
D
Q5
75.8 °C
67.2 °C
E
T1 - WINDING
76.1 °C
77.7 °C
F
T1 – CORE
74.9 °C
76.3 °C
G
D7
77.4 °C
75.7 °C
H
R1 (NTC)
100 °C
80.5 °C
21/33
Conducted emission pre-compliance test
5
AN2521
Conducted emission pre-compliance test
The following figures are the peak measurements of the conducted noise emissions at full
load and nominal mains voltages. The limits shown on the diagrams are those of EN55022
Class-B, which are most popular requirements for domestic equipment and imposes less
stringent limits compared to the Class-A, which is dedicated to IT technology equipment. As
visible in the diagrams, in all test conditions there is a good margin for the measurements
with respect to the limits.
Figure 29. CE peak measure at 100 Vac and full load
Figure 30. CE peak measure at 230 Vac and full load
22/33
AN2521
Bill of material
6
Bill of material
Table 8.
EVAL6668-75W evaluation board: bill of material
Des.
Part type/part value
Description
Supplier
C1
2N2
Y1 safety cap.
Murata
C10
Res.
Not used
C11
Res.
Not used
C12
1000 µF-25V ZL
Aluminium ELCAP - ZL series - 105 °C
Rubycon
C13
100 µF-25V YXF
Aluminium ELCAP - YXF series - 105 °C
Rubycon
C14
220NF
50 V CERCAP - general purpose
AVX
C15
1 µF
25 V CERCAP - general purpose
AVX
C16
1000 µF-25V ZL
Aluminium ELCAP - ZL series - 105 °C
Rubycon
C17
100N
50 V CERCAP - general purpose
AVX
C19
2N2
50 V CERCAP - general purpose
AVX
C2
2N2
Y1 safety cap.
Murata
C20
10N
50 V CERCAP - general purpose
AVX
C21
470N
25 V CERCAP - general purpose
AVX
C22
2µ2-25 V
Aluminium ELCAP - YXF series - 105 °C
Rubycon
C23
Res.
Not used
C24
2N2 - Y1 DE1E3KX222M
Y1 safety cap.
Murata
C25
220PF
50 V CERCAP - general purpose
AVX
C26
22N
50 V CERCAP - general purpose
AVX
C27
47 µF-50 V
Aluminium ELCAP - YXF Series - 105 °C
Rubycon
C28
Res.
Not used
C29
Res.
Not used
C3
470N-X2
X2 film CAPACITOR - R46-I 3470--M1-
Arcotronics
C30
2N2-5%
50 V - 5% - C0G - CERCAP
AVX
C31
Res.
Not used
C32
100N
50 V CERCAP - general purpose
AVX
C33
22 µF-50 V
Aluminium ELCAP - YXF series - 105 °C
Rubycon
C34
100PF
50 V CERCAP - general purpose
AVX
C35
270N
25 V CERCAP - general purpose
AVX
C36
100N
50 V CERCAP - general purpose
AVX
C37
82N
50 V CERCAP - general purpose
AVX
C38
470PF
50 V CERCAP - general purpose
AVX
23/33
Bill of material
Table 8.
AN2521
EVAL6668-75W evaluation board: bill of material (continued)
Des.
Part type/part value
Description
Supplier
C39
4N7
50 V CERCAP - general purpose
AVX
C4
470N-X2
X2 film capacitor - R46-I 3470--M1-
Arcotronics
C40
100N
50 V CERCAP - general purpose
AVX
C41
10N
50 V CERCAP - general purpose
AVX
C42
10 µF-63 V
Aluminium ELCAP - SR series - 85 °C
Rubycon
C43
2N2
50 V CERCAP - general purpose
AVX
C44
100N
50 V CERCAP - general purpose
AVX
C5
470N-400 V
B32653A4474J - polyprop. film cap
EPCOS
C6
100 µF-450 V
Aluminium ELCAP - LLS Series - 85 °C
NICHICON
C7
2N2 - Y1 DE1E3KX222M
Y1 safety cap.
Murata
C8
1N0-200 V
200 V CERCAP - general purpose
AVX
C9
100N
50 V CERCAP - general purpose
AVX
D1
1N4005
General purpose rectifier
Vishay
D10
LL4148
Fast switching diode
Vishay
D11
BAV103
Fast switching diode
Vishay
D12
LL4148
Fast switching diode
Vishay
D13
LL4148
Fast switching diode
Vishay
D14
LL4148
Fast switching diode
Vishay
D15
Res.
Not used
D2
GBU4J
Single phase bridge rectifier
Vishay
D3
STTH2L06
Ultrafast high voltage rectifier
STMicroelectronics
D4
1.5KE250A
TRANSIL
STMicroelectronics
D5
BZV55-B30
ZENER diode
Vishay
D6
Res.
Not used
D7
STPS20H100CFP
High voltage power Schottky rectifier
STMicroelectronics
D8
STTH108A
High voltage ultrafast rectifier
STMicroelectronics
D9
BZV55-C8V2
ZENER diode
Vishay
F1
FUSE 4 A
Fuse T4A - time delay
Wichmann
J1
MKDS 1,5/ 3-5,08
PCB term. block, screw conn., pitch 5MM - 3 W.
Phoenix Contact
J2
MKDS 1,5/ 2-5,08
PCB term. block, screw conn., pitch 5mm - 2 W.
Phoenix Contact
JP5
Jumper
Tinned copper wire jumper
JP7
Res.
Tinned copper wire jumper - not used
JP10
Jumper
Tinned copper wire jumper
JP11
Jumper
Tinned copper wire jumper
24/33
AN2521
Table 8.
Bill of material
EVAL6668-75W evaluation board: bill of material (continued)
Des.
Part type/part value
Description
Supplier
JP12
Jumper
Tinned copper wire jumper
JP13
Jumper
Tinned copper wire jumper
JP14
Jumper
Tinned copper wire jumper
L1
HF2826-253Y1R2-T01
25 MH-1.2 A input EMI filter
TDK
L2
SRW25CQ-T03H112
400 µH PFC inductor
TDK
L3
TSL0706 - 1R5-4R3
1 µ5 - radial inductor
TDK
Q1
BC857C
PNP small signal BJT
ZETEX
Q2
STP9NK50ZFP
N-channel power MOSFET
STMicroelectronics
Q3
Res.
Not used
Q4
Res.
Not used
Q5
STP10NK80ZFP
N-channel power MOSFET
STMicroelectronics
Q6
BC857C
PNP small signal BJT
ZETEX
Q7
Res.
not used
Q8
BC847C
NPN small signal BJT
ZETEX
R1
NTC 10R-S236
NTC resistor 10R - P/N B57236S0100M000
EPCOS
R10
Res.
Not used
R11
2M2 - 1%
SMD std film res. - 1/4 W - 1% - 100 ppm/°C
BC Components
R12
3M3
SMD std film res. - 1/4 W - 1% - 100 ppm/°C
BC Components
R13
Res.
Not used
R14
3R9
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
R15
Res.
Not used
R16
10 kΩ
SMD std film res. - 1/8 W - 1% - 100 ppm/°C
BC Components
R17
62 kΩ
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R18
51 kΩ
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R19
36 kΩ
SMD std film res. - 1/8 W - 1% - 100 ppm/°C
BC Components
R101
0R0
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R102
0R0
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R103
0R0
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R104
0R0
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R105
0R0
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R2
1M0-1%
SMD std film res. - 1/4 W - 1% - 100 ppm/°C
BC Components
R20
20 kΩ
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R21
Res.
Not used
R22
R015 - 1 W
SMD film res. 1 W - 2512 MSR1
MEGGIT
R23
27R
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
BC Components
25/33
Bill of material
Table 8.
AN2521
EVAL6668-75W evaluation board: bill of material (continued)
Des.
Part type/part value
Description
Supplier
R24
100 kΩ
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R25
470R
SFR25 axial stand. film res. - 0.4 W - 5% - 250 ppm/°C
BC Components
R26
120 kΩ
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R27
0R33
SFR25 axial stand. film res. - 0.4 W - 5% - 250 ppm/°C
BC Components
R28
2k2
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R29
Res.
Not used
R3
2M2 - 1%
SMD std film res. - 1/4 W - 1% - 100 ppm/°C
BC Components
R30
22 kΩ
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R31
4k7
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R32
Res.
Not used
R33
10 kΩ
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R34
270 kΩ
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R35
2R7
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R36
1k8
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R37
10 kΩ - 1%
SMD std film res. - 1/8 W - 1% - 100 ppm/°C
BC Components
R38
Res.
Not used
R39
56 kΩ - 1%
SMD std film res. - 1/4 W - 1% - 100 ppm/°C
BC Components
R4
68 kΩ
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R40
Res.
Not used
R41
10 kΩ
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R42
8k2
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R43
4R7
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R44
47 kΩ
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R45
2k2
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R46
47R
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R47
100 kΩ
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R48
4k7 - 1%
SMD std film res. - 1/8 W - 1% - 100 ppm/°C
BC Components
R49
24 kΩ - 1%
SMD std film res. - 1/8 W - 1% - 100 ppm/°C
BC Components
R5
2M2 - 1%
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R50
1k0
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R51
2k2
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R52
0R39
SFR25 AXIAL std film res. - 0.4 W - 5% - 250 ppm/°C
BC Components
R53
0R39
SFR25 axial stand. film res. - 0.4 W - 5% - 250 ppm/°C
BC Components
R54
47 kΩ
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R55
22R
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
26/33
AN2521
Table 8.
Bill of material
EVAL6668-75W evaluation board: bill of material (continued)
Des.
Part type/part value
Description
Supplier
R56
4k7 - 1%
SMD std film res. - 1/8 W - 1% - 100 ppm/°C
BC Components
R57
100R
SFR25 axial stand. film res. - 0.4 W - 5% - 250 ppm/°C
BC Components
R58
M57703 - 10 kΩ
10 k thermistor - B57703M0103G040
EPCOS
R59
24 kΩ
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R6
1M0 - 1%
SMD std film res. - 1/4 W - 1% - 100 ppm/°C
BC Components
R60
56 kΩ
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R61
33 kΩ
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R62
3k3
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R63
0R0
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R64
43 kΩ - 1%
SFR25 axial stand. film res. - 0.4 W - 1% - 100 ppm/°C
BC Components
R65
22 kΩ
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R66
3R9
SMD std film res. - 1/4 W - 5% - 250 ppm/°C
BC Components
R67
6k2 - 1%
SMD std film res. - 1/4 W - 1% - 100 ppm/°C
BC Components
R68
120 kΩ - 1%
SMD std film res. - 1/8 W - 1% - 100 ppm/°C
BC Components
R69
1k0
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R7
3M3
SMD std film res. - 1/4 W - 1% - 100 ppm/°C
BC Components
R71
Res.
Not used
R72
0R0
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R73
62 kΩ
SMD std film res. - 1/8 W - 5% - 250 ppm/°C
BC Components
R8
75 kΩ - 1%
SMD std film res. - 1/8 W - 1% - 100 ppm/°C
BC Components
R9
75 kΩ - 1%
SMD std film res. - 1/8 W - 1% - 100 ppm/°C
BC Components
T1
SRW32EC-T01H114
Power transformer
TDK
U1
L6563
Transition mode PFC controller
STMicroelectronics
U2
L6668
Smart primary controller
STMicroelectronics
U3
SFH617A-4
Optocoupler
Infineon
U4
res.
Not used
U5
TSM1014
Low consumption CC/CV controller
HS1
Heat sink for D2&Q2
HS2
Heat sink for Q5
HS3
Heat sink for D7
STMicroelectronics
27/33
PFC coil specification
AN2521
7
PFC coil specification
7.1
General description and characteristics
7.2
Note:
7.3
●
Application type: consumer, home appliance
●
Inductor type: open
●
Coil former: vertical type, 5+3 pins
●
Max. temp. rise: 45 °C
●
Max. operating ambient temp.: 60 °C
●
Mains insulation: N.A.
●
Unit finishing: varnished
Electrical characteristics
1
●
Converter topology: boost, transition mode
●
Core type: CQ25 - PC47
●
Minimum operating frequency: 20 kHz
●
Typical operating frequency: 400 µH ±10% @1 kHz - 0.25 V (see Note: 1)
●
Peak primary current: 3.5 Apk
●
RMS primary current: 1.2 Arms
Measured between pins #5 and #6
Electrical schematic and winding characteristics
Figure 31. Electrical diagram
8
5
AUX
PRIM.
3
6
Table 9.
Winding characteristics
PINS
Winding
RMS current
Number of
turns
Wire
8-3
AUX (1)
0.05 ARMS
5 spaced
Ø 0.28 mm
1.2 ARMS
50
Multi stranded #10 x Ø 0.20 mm
5-6
Primary
(2)
type
1. Aux winding is wound on coil former before primary winding. To be insulate with a layer of polyester tape.
2. Primary winding external insulation: 2 layers of polyester tape
28/33
AN2521
Mechanical aspect and pin numbering
●
Maximum height from PCB: 20 mm
●
COIL former type: vertical, 5+3 pins
●
PINS #1, 2, 4, 7 have been removed
●
External copper shield: Not insulated, wound around the ferrite core and including the
coil former. Height is 7 mm. Connected to pin #3 by a solid wire.
Figure 32. Mechanical aspect and pin numbering of PFC coil
1. External COPPER sheet (0.025x7 mm)
2. MYLAR tape - 1 turn
D
˳ x8
C
8
5
1
7'.
7.4
PFC coil specification
6
25CQ-TXX
TDK
Ⴜ ႒႒႒႒
5
1
A
5
6
B1 B1 B1 B1
1
5
F E
6
8
B2
●
A: 27.0 max mm
●
B1: 3.0 ± 0.3 mm
●
B2: 5.0 ± 0.3 mm
●
C: 3.3 ± 0.3 mm
●
D: 19.0 max mm
●
E: 21.0 ± 0.5 mm
●
F: 23.7 ± 0.5 mm
B2
29/33
Transformer specification
AN2521
8
Transformer specification
8.1
General description and characteristics
8.2
Note:
8.3
●
Application type: consumer, home appliance
●
Transformer type: open
●
Winding type: layer
●
Coil former: horizontal type, 9+9 pins
●
Max. temp. rise: 45 °C
●
Max. operating ambient temp.: 60 °C
●
Mains insulation: acc. with EN60950
●
Unit finishing: varnishing
Electrical characteristics
●
Converter topology: flyback, CCM/DCM mode
●
Core type: EER34 - PC47
●
Min. operating frequency: -
●
Typical operating freq: 60 kHz
●
Primary inductance: 550 µH 10% @1 kHz - 0.25 V (see Note 1)
●
Leakage inductance: 17 µH max
●
Max. peak primary current: 2.65 Apk
●
RMS primary current: 0.78 Arms
@ 100 kHz - 0.25 V (see Note 1 - Note 2)
1
Measured between pins 1-3
2
Measured between pins 1-3 with all secondary windings shorted
Electrical diagram and winding characteristics
Figure 33. Electrical diagram
5
PRIM. A
2
6
15-16
PRIM. B
+12V
3
8
AUX
9
30/33
10-11
AN2521
Transformer specification
Table 10.
Note:
Winding characteristics
Pin
Winding
O/P RMS
current
Number of
turns
Number of
layers
Wire type
5-6
Aux
0.05 ARMS
7 spaced
1
G2 – φ 0.23 mm
3-1
Primary - A
0.39 ARMS
60
2
G2 – 2 x φ 0.23 mm
8 - 10
19 V
5.2 ARMS
8
1
Multistrand
G2 - 4 x φ 0.64 mm
4-2
Primary - B
0.39 ARMS
60
2
G2- 2 x φ 0.23 mm
All terminal wires must be insulated by tube
Figure 34. Winding position on coil former
6.2
Polyester tape - 2 layers
Polyester tape - 2 layers
Polyester tape - 2 layers
Polyester tape - 1 layers
6.2
PRIMARY - B
19V
PRIMARY - A
AUX
Barrier tape
coil former
Note:
Primaries A & B are in parallel
8.4
Mechanical aspect and pin numbering
●
Maximum height from PCB: 30 mm
●
Coil former type: horizontal, 9+9 pins (pin 2 removed)
●
pin distance: 4 mm
●
Row distance: 35 mm
●
External copper shield: not insulated, wound around the ferrite core and including the
coil former. Height is 12 mm.
31/33
Revision history
AN2521
Figure 35. Mechanical aspect and pin numbering of flyback transformer
1. External copper sheet (0.025x12 mm)
2. Mylar tape - 1 T
9
●
A: 38.0 max mm
●
B: 4.0 ± 0.3 mm
●
C: 3.5 ± 0.5 mm
●
D: 26.5 max mm
●
E: 40.0 max mm
●
F: 35.0 ± 0.5 mm
Revision history
Table 11.
32/33
Document revision history
Date
Revision
24-Oct-2007
1
Changes
Initial release
AN2521
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