AN2600
Application note
SMPS for high-end PVR based on L6668
Introduction
The set-top box (STB) market is growing very fast due to the high growth of both satellite
and terrestrial/cable broadcasting. As expected, the market is always looking for solutions
with high cost effectiveness and performance.
This document introduces a reference design of a 55 W switch-mode power supply
dedicated to high-end set-top box applications, and in particular for PVRs (Personal Video
Recorders). This kind of solution in addition to typical loads is able to supply HD and VFD
front panels. The board accepts European input voltage range (from 185 to 265V
ac
) and
delivers eight outputs. It is based on the advanced current mode PWM controller L6668,
working at fixed frequency. Despite high performance, standard parts are used, e.g.
standard capacitors are connected on the outputs in place of low ESR components
commonly used, contributing to an overall decrease of the total cost of the solution.
Figure 1.
STEVAL-ISA040V1
January 2008
Rev 1
1/30
www.st.com
Contents
AN2600
Contents
1
2
Main characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Circuit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1
2.2
Transformer specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1.1
Windings data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
BOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3
Test description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
Cross regulation and main waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
High frequency ripple of output voltages at full load . . . . . . . . . . . . . . . . . 20
Measurement of RMS current of output capacitors . . . . . . . . . . . . . . . . . 21
Dynamic load test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Startup behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Wakeup time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Short circuit test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Conducted emission (EMI) measurements . . . . . . . . . . . . . . . . . . . . . . . 28
Thermal measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4
5
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2/30
AN2600
List of tables
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Table 19.
Table 20.
Table 21.
Output specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Windings parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Output voltages measurement at V
in
= 184 V and full load . . . . . . . . . . . . . . . . . . . . . . . . . 12
Output voltages measurement at V
in
= 230 V and full load . . . . . . . . . . . . . . . . . . . . . . . . . 12
Output voltages measurement at V
in
= 276 V and full load . . . . . . . . . . . . . . . . . . . . . . . . . 13
Output voltages measurement at V
in
= 184 V and reduced load. . . . . . . . . . . . . . . . . . . . . 14
Output voltages measurement at V
in
= 230 V and reduced load. . . . . . . . . . . . . . . . . . . . . 15
Output voltages measurement at V
in
= 276 V and reduced load. . . . . . . . . . . . . . . . . . . . . 15
Output voltages measurement at V
in
= 184 V and reduced load (20 W) . . . . . . . . . . . . . . . 17
Output voltages measurement at V
in
= 230 V and reduced load (20 W) . . . . . . . . . . . . . . . 17
Output voltages measurement at V
in
= 276 V and reduced load (20 W) . . . . . . . . . . . . . . . 17
Output voltages measurement at V
in
= 230 V and light load . . . . . . . . . . . . . . . . . . . . . . . . 19
Measurement of high frequency ripple of output voltages at V
in
= 230 V and full load . . . . 20
Measurement of RMS current of output capacitors at V
in
= 230 V and full load . . . . . . . . . 21
Dynamic load test on 3.3 V
out
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Dynamic load test on 5 V
out
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Overshoot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Thermal behavior of the components at primary side. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Thermal behavior of the components at secondary side . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3/30
List of figures
AN2600
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.
STEVAL-ISA040V1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Electrical schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Transformer electrical and mechanical drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Vds and Id of STP5NK60Z in full load at V
in
= 184 V
rms
- 50 Hz . . . . . . . . . . . . . . . . . . . . 13
Vds and Id of STP5NK60Z in full load at V
in
= 230 V
rms
- 50 Hz . . . . . . . . . . . . . . . . . . . . 13
Vds and Id of STP5NK60Z in full load at V
in
= 276 V
rms
- 50 Hz. . . . . . . . . . . . . . . . . . . . 14
Vds and Id of STP5NK60Z at reduced load V
in
= 184 V
rms
- 50 Hz . . . . . . . . . . . . . . . . . 15
Vds and Id of STP5NK60Z at reduced load V
in
= 230 V
rms
- 50 Hz . . . . . . . . . . . . . . . . . 16
Vds and Id of STP5NK60Z at reduced load V
in
= 276 V
rms
- 50 Hz . . . . . . . . . . . . . . . . . 16
Vds and Id of STP5NK60Z at reduced load (20 W) V
in
= 184 V
rms
- 50 Hz . . . . . . . . . . . . 18
Vds and Id of STP5NK60Z at reduced load (20 W) V
in
= 230 V
rms
- 50 Hz . . . . . . . . . . . . 18
Vds and Id of STP5NK60Z at reduced load (20 W) V
in
= 276 V
rms
- 50 Hz . . . . . . . . . . . . 19
Vds and Id of STP5NK60Z at light load at 230 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
High frequency ripple of output voltages at full load at 230 V. . . . . . . . . . . . . . . . . . . . . . . 21
Outputs behavior under dynamic load on 3.3 V output at V
in
=230 V. . . . . . . . . . . . . . . . . 22
Behavior of outputs with dynamic load applied to 5 V output at V
in
=230 V . . . . . . . . . . . . 23
Startup behavior of the system at V
in
= 184 V
rms
- 50 Hz. . . . . . . . . . . . . . . . . . . . . . . . . . 24
Startup behavior of the system at V
in
= 230 V
rms
- 50 Hz. . . . . . . . . . . . . . . . . . . . . . . . . . 24
Startup behavior of the system at V
in
= 276 V
rms
- 50 Hz. . . . . . . . . . . . . . . . . . . . . . . . . . 25
Wakeup behavior of the system at V
in
= 184 V
rms
- 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . 26
Wakeup behavior of the system at V
in
= 230 V
rms
- 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . 26
Wakeup behavior of the system at V
in
= 276 V
rms
- 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . 27
Short circuit on 5 V output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Conducted emissions of the system at full load and V
in
=230 V - phase conducted emission28
Conducted emissions of the system at full load and V
in
=230 V-neutral conducted emission 28
4/30
AN2600
Main characteristics
1
Main characteristics
The main characteristics of the SMPS are listed below:
●
Input voltage:
–
–
V
in
= 185 ÷ 265 V
rms
f=50 Hz
Output specifications
Vout (V):
1
2
3
4
5
6
7
8
3.3
5
12
16
23
-25
3.3 AC
33
Iout (A)
3.5
1.9
0.8
0.5
0.5
0.15
0.08
0.01
Pout (W)
11.55
9.5
9.6
8
11.5
3.75
0.25
0.33
+/- 10%
55 W
Tolerance
+/- 5%
+/- 5%
+/- 2%
+/- 10%
+/- 10%
+/- 10%
Notes
Dedicated to 3.3 V circuitry, 2.6 V and
1.1 V local post regulators
Dedicated to HDD, display, 5V circuitry
and 2.6 V local post regulators
Dedicated to HDD
Dedicated to LNB for satellite DVB
Dedicated to LNB for satellite DVB
Dedicated to display
Dedicated to the display filaments
Dedicated to the tuner
Table 1.
P
OUT
(W) =
●
●
EMI: in accordance with EN55022 Class B
Safety: in accordance with IEC 60065 7
th
ed.
5/30
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