AN2448 Application note
EVALTSM1052: Ultra small battery charger using TSM1052
Introduction
This document describes a low power adapter that can be used in travel battery charger applications. It uses the new Constant Voltage Constant Current (CVCC) controller TSM1052, which is housed in one of the smallest packages available (SOT23-6L). Thanks to its low consumption and low operating voltage, good electrical performance is achieved. Another important feature of this SMPS is the absence of the Y1 safety capacitor between primary and secondary grounds. Figure 1. EVALTSM1052 demo board
July 2007
Rev 1
1/21
www.st.com
Contents
AN2448
Contents
1 Adapter features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 1.2 Main characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Circuit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 3
Electrical behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Electrical performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1 3.2 3.3 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Output characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Hold-up time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4 5 6 7 8
Conducted noise measurements (pre-compliance test) . . . . . . . . . . . 16 Thermal measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 BOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
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AN2448
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. EVALTSM1052 demo board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Vin = 115 Vrms - 60 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Vin = 230 Vrms - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Maximum supply voltages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Minimum supply voltages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Vin = 115 Vac - no-load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Vin = 230 Vac - no-load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Vin = 115 Vac - short circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Vin = 230 Vac - short circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Efficiency vs. output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Output characteristics at 115 Vac with CDC (cable drop compensation) . . . . . . . . . . . . . . 13 Power down at 115 Vac - 60 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Power down at 230 Vac - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 CE peak measure at 115 Vac and full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 CE peak measure at 230 Vac and full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Vin = 115 Vac - full load - bottom and top sides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Vin = 230 Vac - full load - bottom and top sides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 THT components placing (top side) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 SMT components placing (bottom side) and copper tracks. . . . . . . . . . . . . . . . . . . . . . . . 20
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Adapter features
AN2448
1
1.1
Adapter features
Main characteristics
Input: Vin: 90 ~ 264 Vrms f: 45 ~ 66 Hz 5.1Vdc 2% 600 mA Cable drop compensation (0.33 mV/mA) Pin below 0.3 W
Output:
No-load: Shor t circuit: protected with nominal current regulation PCB type & size: CEM-1 Single side 35 m 48 x 18 mm
Safety: according to EN60065 EMI: according to EN55022 - class B
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AN2448 Figure 2.
F1 10 Ohm 2W D5 1N 4148W S 2 6 1
I1
1m H
Electrical diagram
AC1
C9 1uF I C 1B S FH617-A 3 X007 2
Vout
2
9 0 ÷2 6 4 V A C
1 8 C2 4. 7F 400V R2 680 Ohm D2 U F 108G R5 100 Ohm R6 330 Ohm
D1 S1Z B60 4-
C4 1. 5nF 250V TR 1A EF 12. 6LP TR 1C EF 12. 6LP
R1 330K
+3
C1 2. 2F 400V
1
R9 22K 1% R 14 22K C8 4. 7nF
AC2
IC 2 D3 1N 4148W S 5678 VI PER 12AS-E 4 4 5 FB 7 TR 1B EF 12. 6LP 3 R 3 1K 3 21 TR 1D EF 12. 6LP C5 330nF 9 I C 1A SF H 617-A3 X007 SS C6 470F 16V VD D DDDD R 15 0 Ohm D4 STPS3L40S C 11 1. 8nF C7 22nF 1 R 13 220K 2 3
IC 3 Vc t rl Gnd Out Vc c Vs I c t rl TSM1052 6 5 4 R7 22K 1% R 12 2. 2K
5 .1 V - 600mA
4
C3 33F 50V R4 2. 2 Ohm
C 10 10nF
R8 4. 7K
R 10 10K 1%
GND
R 11 0. 33 Ohm
Adapter features
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Adapter features
AN2448
1.2
Circuit description
The circuit used implements a flyback topology, which is ideal for a low power, low cost isolated converter. At primary side a VIPer12A-E has been used. This IC includes a current mode PWM controller and a Power MOSFET in a small SO-8 package. The converter works in both continuous and discontinuous conduction mode depending on the input voltage (the circuit has a wide range input) and the output load. The switching frequency is internally fixed at 60 KHz. The design has been developed to reduce overall component count and adapter cost. The input section includes a resistor for inrush current limiting, a diode bridge, two electrolytic bulk capacitors and an inductor as front-end ac-dc converter and EMC filter. The transformer is a layer type, uses a standard EF12.6 ferrite core and is designed to have a reflected voltage of about 90 V. The peculiarity of this transformer is the winding technique which allows the elimination of the usual Y1 safety capacitor between the primary and the secondary. A RCD clamp network is used for leakage inductance demagnetization. The power supply for the VIPer12A-E is obtained with a self supply winding from the transformer connected in forward configuration. This circuit provides a voltage that is directly proportional to the input rectified voltage and independent from the load voltage. In this way even in short circuit condition (VOUT = 0), the IC is correctly supplied. The wide VDD operating range (9 V to 38 V) of the VIPer12A-E allows a wide range mains input voltage. At secondary side, the TSM1052 constant voltage constant current (CVCC) controller is used. Like the VIPer12A-E, the TSM1052 is also supplied with a forward configuration, in order to obtain the same benefit. The voltage is taken on one half of the secondary winding (between pins 8 and 6), rectified with diode D5 and added to the output voltage. Under all working conditions, the voltage supply for the TSM1052 and the photodiode IC1B is equal to the output voltage plus forward rectified voltage on half secondary. With this configuration a correct supply is provided over the whole input range, even with the output short circuited. With this configuration a small ripple at twice line frequency is present at the output. This is due to the supply of the photodiode IC1B, which is a replica of the voltage on C2. Usually this is not a problem in battery chargers. There are two ways to eliminate this phenomenon if necessary:
C9 can be substituted by an electrolytic capacitor (at least 47 F) The TSM1052 and IC1B can be attached directly to the output voltage. In this case the current regulation is guaranteed only for output voltages down to 1.7 V
Resistor R7 has been added for cable drop compensation (the higher the output current the higher the output voltage). R7 has been chosen according to the cable characteristics (it has about 0.3 of resistance).
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AN2448
Electrical behavior
2
Electrical behavior
Figure 3 and Figure 4 show all the VIPer12A-E waveforms during normal operation at full load. The converter operates in DCM at both 115 Vrms and 230 Vrms: Figure 3. Vin = 115 Vrms - 60 Hz
CH1: VIPer12A-E supply voltage (yellow) CH2: VIPer12A-E feedback pin (red) CH3: VIPer12A-E drain voltage (green)
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Electrical behavior Figure 4. Vin = 230 Vrms - 50 Hz
AN2448
CH1: VIPer12A-E supply voltage (yellow) CH2: VIPer12A-E feedback pin (light blue) CH3: VIPer12A-E drain voltage (purple) Due to the forward supply, the VDD voltage is directly proportional to the input voltage, so it is nearly double at 230 Vac with respect to 115 Vac. The worst case (maximum / minimum) supply voltages for both primary and secondary sides are shown in Figure 5 and Figure 6. For the maximum voltages, the converter operates with the maximum load in CV mode (that is, the maximum output voltage is present, thanks to the cable drop compensation) and with the maximum input voltage (264 Vac). In this condition the VIPer12A-E has a maximum supply voltage of 35.2 V and the TSM1052 16.16 V. Minimum voltages are taken with short circuit on the output (CC regulation) and minimum input voltage (90 Vac). Given this condition the VIPer12A-E has a minimum supply voltage of 10.48 V and the TSM1052 2.12 V.
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AN2448 Figure 5. Maximum supply voltages
Electrical behavior
CH1: output voltage (yellow) CH2: VIPer12A-E supply voltage (light blue) CH3: TSM1052 supply voltage (green) Figure 6. Minimum supply voltages
CH1: output voltage (yellow) CH2: VIPer12A-E supply voltage (light blue) CH3: TSM1052 supply voltage (green)
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Electrical behavior Let's see what happens at the extreme conditions: no load and short circuit.
AN2448
During no load conditions, the circuit operates in burst mode allowing an input power of less than 300 mW over the whole input voltage range. Figure 7. Vin = 115 Vac - no-load
CH1: output voltage (yellow) CH2: VIPer12A-E drain pin (purple) CH3: TSM1052 supply voltage (green) Figure 8. Vin = 230 Vac - no-load
CH1: output voltage (yellow) CH2: VIPer12A-E drain pin (purple) CH3: TSM1052 supply voltage (green)
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AN2448 Figure 9. Vin = 115 Vac - short circuit
Electrical behavior
CH1: output voltage (yellow) CH2: VIPer12A-E drain pin (purple) CH3: TSM1052 supply voltage (green) Figure 10. Vin = 230 Vac - short circuit
CH1: output voltage (yellow) CH2: VIPer12A-E drain pin (purple) CH3: output current (green)
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Electrical performance
AN2448
With the circuit used in this evaluation board, when the output current has rapid variation from maximum to zero and the input voltage is low ( < 105 Vac), the VIPer12A-E loses the supply for about 400-500 ms. The output voltage thereby decreases. After that time the IC turns on again and the output returns to the nominal value. This behavior is not problematic in this kind of application and has not been modified, in order to have a smaller and cheaper solution. If this phenomenon must be avoided, however, it is enough to increase C3 to 100 F.
3
3.1
Electrical performance
Efficiency
Table 1 and Table 2 show the board efficiency at the two nominal voltages. Table 1.
Io [A] 0.1 0.2 0.3 0.4 0.5 0.6
Efficiency at 115 Vrms
Vo [V] 5.153 5.185 5.217 5.248 5.280 5.310 Po [W] 0.520 1.036 1.566 2.096 2.638 3.187 Iin [mA] 16.9 27.4 38.2 47.6 58.7 68.5 Pin [W] 0.832 1.483 2.235 2.928 3.769 4.530 Efficiency 62.5% 69.9% 70.1% 71.6% 70.0% 70.3%
Table 2.
Io [A] 0.1 0.2 0.3 0.4 0.5 0.6
Efficiency at 230 Vrms
Vo [V] 5.158 5.190 5.222 5.254 5.286 5.319 Po [W] 0.520 1.037 1.568 2.098 2.641 3.192 Iin [mA] 12.8 20.1 25.5 32.6 38.4 43.6 Pin [W] 1.033 1.740 2.364 3.193 3.908 4.572 Efficiency 50.4% 59.6% 66.3% 65.7% 67.6% 69.8%
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AN2448 Figure 11. Efficiency vs. output current
Efficiency
75.0%
Electrical performance
70.0%
65.0%
Efficiency
60.0% 115Vac 230Vac 55.0%
50.0%
45.0%
40.0% 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Output current [A]
As indicated in Table 3, the no-load consumption is always below 300 mW, and therefore complies with the more restrictive standards (European Code Of Conduct). Table 3.
Value Pin [W] VOUT [V]
No-load consumption
90Vac 0.106 5.12 115Vac 0.131 5.12 230Vac 0.239 5.12 264Vac 0.273 5.12
3.2
Output characteristics
Figure 12 shows the output characteristics (taken with 115 Vac mains input) on PCB pads and at the end of the output cable. Values are very close also at 230 Vac. It is interesting to note that, while in the constant current region, the output voltage can reach zero. Figure 12. Output characteristics at 115 Vac with CDC (cable drop compensation)
V -I characteristics
6 5
O u tp u t voltage [V]
4 3 2 1 0 0 200 400
Ou tp u t current [mA]
P C B output E n d of cable
600
800
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Electrical performance
AN2448
The effect of the cable drop compensation is also worthy of note. Table 4 shows the output voltage at various load amounts measured at the output connector, after the output cable. 115 Vac and 230 Vac mains input give very similar results. With the cable drop compensation the output voltage is nearly constant while, without this feature, at maximum load the output voltage goes down to 4.96 V (about -3.1%). The effect of this feature is also clearly visible in the output characteristic (Figure 12), with a flat line while in the constant voltage regulation region. Table 4. Output voltage at output connector
Iout [A] Vout [V] with CDC Vout [V] without CDC 0 5.12 5.12 0.1 5.13 5.09 0.2 5.13 5.07 0.3 5.14 5.04 0.4 5.14 5.01 0.5 5.15 4.98 0.6 5.15 4.96
3.3
Hold-up time
During power down phase the output voltage undergoes a clean transition without restart trials or glitches. By observing the waveforms it is possible to measure the hold-up time. In Figure 13 and Figure 14 this condition is shown for the two nominal voltages of 115 Vac and 230 Vac. In the worst case, 115 Vac, a hold-up time of about 17.1 ms is measured. Figure 13. Power down at 115 Vac - 60 Hz
CH1: output voltage (yellow) CH3: rectified input voltage (purple)
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AN2448 Figure 14. Power down at 230 Vac - 50 Hz
Electrical performance
CH1: output voltage (yellow) CH3: rectified input voltage (pur ple)
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Conducted noise measurements (pre-compliance test)
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4
Conducted noise measurements (pre-compliance test)
Figure 15 and Figure 16 show the conducted noise measurements performed at the two nominal voltages with peak detection and considering only the worst phase. The measurements have a good margin with respect to the limits (stated in EN55022 CLASS B specifications). Figure 15. CE peak measure at 115 Vac and full load
Figure 16. CE peak measure at 230 Vac and full load
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Thermal measurements
5
Thermal measurements
A thermal analysis of the board was performed using an IR camera. The results are shown in Figure 17 and Figure 18 for 115 Vac and 230 Vac mains input. Both images refer to full load condition (Iout = 600 mA). TAMB = 25 C for both figures Emissivity = 0.9 for all points Figure 17. Vin = 115 Vac - full load - bottom and top sides
Table 5.
Key component temperatures at 115 Vac - 600 mA
Point A B C D E F G Temperature [C] 69.2 72.3 63.0 66.3 68.3 64.0 66.2 Reference R2 (clamp) R1 (clamp) IC2 (VIPer12A-E) D4 (output diode) TR1 (windings) TR1 (ferrite) Hot spot on PCB due to bottom side components
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Thermal measurements Figure 18. Vin = 230 Vac - full load - bottom and top sides
AN2448
Table 6.
Key component temperatures at 230 Vac - 600 mA
Point A B C D E F G Temperature [C] 70.4 72.7 67.9 66.1 70.4 66.0 68.5 Reference R2 (clamp) R1 (clamp) IC2 (VIPer12A-E) D4 (output diode) TR1 (windings) TR1 (ferrite) Hot spot on PCB due to bottom side components
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AN2448
BOM
6
BOM
Table 7.
Ref C1 C2 C3 C6 C4 C5 C7 C8 C9 C10 C11 D1 D2 D3 D5 D4 F1 I1 IC1 IC2 IC3 R1 R2 R3 R4 R5 R6 R7 R9 R8 R10 R11 R12 R13
EVALTSM1052 bill of material
Description Electr.cap. 2.2 F 400 V 105C SEK Electr.cap. 4.7 F 400 V 105C SEK Electr.cap. 33 F 50 V 105C Electr.cap. 470 F 16 V 105C SEK Chip capacitor 1.5 nF/250 V X7R Chip capacitor 330 nF/16 V X7R Chip capacitor 22 nF/25 V X7R Chip capacitor 4.7 nF/25 V X7R Chip capacitor 1 uF/16 V X7R Chip capacitor 10 nF/50 V X7R Chip capacitor 1.8 nF/50 V X7R Single phase bridge S1ZB60 Diode UF108G DIODE 1N4148WS Diode STPS3L40S Fuse res. 10 Ohm 5% 2 W Inductor 1 mH CECL-102K Opto SFH617-A3 X007 I.C. VIPer12AS-E I.C. TSM1052CLT Chip resistor 330 K 5% Chip resistor 680 Ohm 5% Chip resistor 1 K 5% Chip resistor 2.2 Ohm 5% Chip resistor 100 Ohm 5% Chip resistor 330 Ohm 5% Chip resistor 22 K 1% Chip resistor 4.7 K 5% Chip resistor 10 K 1% Chip resistor 0.33 Ohm 1% 200 ppm Chip resistor 2.2 K 5% Chip resistor 220 K 5% SMT SO8 SOT23-6L 0805 0805 0603 0603 0603 0603 0603 0603 0603 1206 0805 0603 COILS ELECTR. SIEMENS STMicroelectronics STMicroelectronics Size ø6x11 p2.5 ø8x11 p3.5 ø5x11 p2.5 ø8x11 p3.5 0805 0603 0603 0603 0603 0603 0603 MBS D041 SOD323 SMC STMicroelectronics PANJIT TEAPO/YAGEO Manufacturer TEAPO/YAGEO TEAPO/YAGEO
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PCB layout Table 7.
Ref R14 R15 TR1
AN2448 EVALTSM1052 bill of material (continued)
Description Chip resistor 22 K 5% Chip resistor 0 Ohm Transformer Size 0603 0603 EF12.6 LP Manufacturer
7
PCB layout
Figure 19. THT components placing (top side)
Figure 20.
SMT components placing (bottom side) and copper tracks
8
Revision history
Table 8.
Date 04-Jul-2007
Revision history
Revision 1 First issue Changes
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AN2448
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