AN3011 STMICROELECTRONICS | Alldatasheet
Document overview
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- PDF pages: 37
Technical content
Datasheet sections
- 1 Board descriptions
- 1.1 Electrical specifications
- 1.2 Schematic and bill of materials
- 1.3 Transformer
- 2 Testing the board
- 2.1 Typical board waveforms
- 2.2 Precision of the regulation and output voltage ripple
- 3 Efficiency
- 3.1 Light load performance
- 3.1.1 No-load condition
- 3.1.2 Low-load performance
- 3.2 Test equipment and measurement of efficiency and input power
- 3.2.1 Measuring input power notes
- 3.3 Overload protection
- 3.4 Secondary winding short-circuit protection
- 3.5 Output overvoltage protection
- 3.6 Brown-out protection
- 4 Conclusions
- 5 References
- 6 Revision history
application is in standby mode. to reduce the transformer size. Figure 1. Demonstration board image
Table 12. Low-load performance. P
1 Board descriptions
1.1 Electrical specifications
The electrical specifications of the demonstration board are listed in Table 1.
1.2 Schematic and bill of materials
Table 1. Electrical specifications
Figure 2. Schematic
Table 2. BOM C3 33 µF 450 V electrolytic cap. C4 22 µF 35 V electrolytic cap.
1.3 Transformer
Figure 3, 4, 5, and 6 show the size and pin distances (inches and [mm]) of the transformer. Table 2. BOM (continued) Table 3. Transformer characteristics
2 Testing the board
2.1 Typical board waveforms
minimum 90 VAC and the maximum 265 VAC. (mainly in the VIPer) and the stress on the above mentioned components. Figure 7. Drain current and voltage at full- Figure 8. Drain current and voltage at full- Figure 9. Drain current and voltage at full- Figure 10. Drain current and voltage at full-
2.2 Precision of the regulati on and output voltage ripple
and minimum VOUT, see Ta bl e 4). The VDD voltage was also measured. the regulated output divided by output current of the unregulated output). measured to verify the effectiveness of the LC filter.
- The output voltage ripple when the converter input voltage is 115 VAC is shown in
Table 4. Output voltage and V DD line-load regulation
3 Efficiency
load) for different input voltages. The results are given in Table 5 below. Figure 16, the value of efficiency versus load for different input voltages is plotted. Figure 15. Efficiency vs V IN Table 5. Efficiency
Figure 16. Efficiency vs load (the average was obtained considering efficiency at different input voltages). Table 6. Active-mode efficiency
nameplate output current greater than or equal to 550 mA. mode for standard models and for low voltage models respectively. Figure 19. ENERGY STAR efficiency criteria Table 8. Energy efficiency criteria for standard models Table 9. Energy efficiency criteria for low voltage models
3.1 Light load performance
3.1.1 No-load condition
affects the input power due to the power dissipated in the resistor divider itself. other low load cases, is given in order to supply more complete information. Table 10. No-load input power Table 11. Energy consumption criteria for no-load
3.1.2 Low-load performance
- POUT = 30 mW
- POUT = 50 mW
Table 12. Low-load performance. P OUT = 30 mW (brown-out disabled) Table 13. Low-load performance. P OUT = 30 mW (brown-out enabled) Table 14. Low-load performance. P OUT = 50 mW (brown-out disabled)
- POUT = 100 mW
Table 15. Low-load performance. P OUT = 50 mW (brown-out enabled) Table 16. Low-load performance. P OUT = 100 mW (brown-out disabled) Table 17. Low-load performance. P OUT = 100 mW (brown-out enabled)
- POUT = 200 mW
Figure 20. Converter input power vs Vin_ac in light-load condition Table 18. Low-load performance. P OUT = 200 mW (brown-out disabled)
Figure 22. Efficiency vs AC input voltage when the input power is 1 W
3.2 Test equipment and measurem ent of efficiency and input
average measured power, averaging the instantaneous measured power. source and the wattmeter internal block diagram. order to measure the output voltage of the power converter. the current sourced by the electronic load.
3.2.1 Measuring input power notes
higher than zero) and across the cables that connect the wattmeter to the UUT.
Figure 25. Wattmeter connection scheme for high input current 30 minutes (warm-up period) immediately prior to conducting efficiency measurements. be recorded at the end of the 5 minute period. accumulated energy is measured over time for both AC input and DC output. this by the integration time itself gives the average input power.
3.3 Overload protection
The following waveforms show the behavior of the converter when the output is shorted.
Figure 28. Converter power capability
3.4 Secondary winding sh ort-circuit protection
behavior of the system during these tests.
3.5 Output overvoltage protection
cycles before it stops operation (see device datasheet for details). Figure 31. OVP circuit Figure 32 and 33). The crest value of the CONT pin voltage tracks the output voltage.
condition ([6.731 V; 7.035 V], ΔVOUT_OVP = 304 mV less then 5% of variation). that the OVP protection is not erroneously activated.
3.6 Brown-out protection
ensures noise immunity. The brown-out comparator is also provided with current hysteresis. pin is below 450 mV and OFF if the voltage exceeds 450 mV plus the voltage hysteresis. Table 21. Overvoltage protection activation level test results (continued)
4 Conclusions
The flyback converter is suitable for different applications and can be used as an external adapter or as an auxiliary power supply in consumer equipment. Special focus was put on low-load performance and the bench results are good with a very low input power in light- load conditions. The efficiency performance was compared with the requirements of the ENERGY STAR program for external AC/DC adapters with very good results, as the measured active mode efficiency is always higher with respect to the minimum required.
5 References
- ENERGY STAR ® Program requirements for single voltage external AC/DC adapter (Version 2.0) 2. VIPER27 datasheets
6 Revision history
Table 22. Document revision history 13-Jan-2011 1 Initial release.