VIPower VB409: OFF-LINE AC/DC CONVERTER Aiello Macina INTROD

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VIPower VB409: OFF-LINE AC/DC CONVERTER Aiello Macina INTROD

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AN1219 APPLICATION NOTE
VIPower VB409: OFF-LINE AC/DC CONVERTER
Aiello Macina
INTRODUCTION VB409 off-line AC-DC Converter. supplies output with current internally limited 70mA. device made using Vertical Intelligent Power (VIPower) M1-HV technology. first part this paper covers performance VB409. second part describes increase efficiency. order reduce power dissipation phase control method used. device made stages: high voltage pre-regulator voltage linear regulator. first stage provides charging current external voltage capacitor during time period determined external divider which sets conduction angle. This charge used feed voltage linear regulator stage. Fig.1: VB409 Application Scheme
Half Fully rectified main
VB409
Iout
Vout Load
Fig. Main Waveforms
Ilim Itot
T+t0 T+t1 T+t2
Vcap
Vcmax Vcmin
January 2000
AN1219 APPLICATION NOTE
DESIGN CONSIDERATIONS Figure shows general schematic. Figure shows main waveforms half wave rectification. Some general considerations about board design device power dissipation made. output current Iout internal quiescent current possible write:
Iout Itot
Where continuos charge consumption voltage regulator stage. This also charge which needs given capacitor during conduction time high voltage switch. Referring Fig.2 seen that conduction time greater than capacitor value chosen guarantee supply voltage stage during this longer time interval. best condition have capacitor charged maximum voltage time. With this hypothesis possible calculate
drop trilinton power stage, device turned when:
asin
with maximum capacitor voltage
charge lost during interval
With hypothesis that this lost charge recovered during first conduction period power stage immediately delivers maximum current Ilim, time needed
-Ili Ilim
This operative condition, that external divider turn high voltage switch case conduction angle greater than interval high voltage stage power will work regulation mode, that will supply only current Itot. Assuming real turn-off time high voltage stage will switched again
During interval charge supplied capacitor
Itot
This charge will recovered
once again H.V. Stage will work regulation mode.
AN1219 APPLICATION NOTE
terms power dissipation following expression written:
optimum value found minimizing this function Fig. VB409 Application Scheme with Input Filter
Half Fully rectified main
VB409
Iout
Vout Load
APPLICATION CIRCUIT IMPROVE EFFICIENCY circuit figure used further decrease power dissipation, comparison made with standard circuit (Fig.1). series inductance decouples power switch from mains, allowing work saturation region when voltage divider must connected before inductance, order sense mains distorted voltage waveform after purpose diode twofold: limits overvoltage across VB409, presence inductance when power switch turned-off; discharge path energy stored inductance during device conduction. following waveforms behavior VB409 compared, using both standard circuit modified one. measurements have been done considering same output current Iout (24mA).
AN1219 APPLICATION NOTE
Fig. Input Current Voltage Standard Configuration
Fig. Input Current Voltage with Series Inductance
Fig. shows current voltage input using standard configuration. Fig. shows same waveforms using topology Fig. with series inductance. seen that power consumption reduced about 25%.
AN1219 APPLICATION NOTE
Fig. First Pulse Standard Configuration Zoom
Fig. First Pulse with Series Inductance Zoom
AN1219 APPLICATION NOTE
Fig. Second Pulse Standard Configuration Zoom
Fig. Second Pulse with Series Inductance Zoom
AN1219 APPLICATION NOTE
Fig. Fig. respectively show zoom Fig. Fig. during rising edge input voltage, while Fig. Fig. show zoom Fig. Fig. during falling edge. same measurements were repeated using full wave rectified mains using Graetz bridge; this configuration conduction occurs four times period (T). Figs.10-11 show conduction current respectively with without series inductor, well power dissipation both configurations. Fig. Input Current Voltage Standard Configuration with Full Rectified Main
Fig. Input Current Voltage with Series Inductance Full Rectified Main
AN1219 APPLICATION NOTE
Looking power dissipation seen that there advantages using bridge without series inductance fact there increase power dissipation (762mW instead 703.5mW). However, possible obtain appreciable reduction power dissipation employing series filter. this case (Fig.11) power reduced 421.8mW representing gain 100mW compared half wave rectified configuration with series inductance (Diode filter P=526.8mW).
AN1219 APPLICATION NOTE
Information furnished believed accurate reliable. However, STMicroelectronics assumes responsibility consequences such information infringement patents other rights third parties which results from use. license granted implication otherwise under patent patent rights STMicroelectronics. Specifications mentioned this publication subject change without notice. This publication supersedes replaces information previously supplied. STMicroelectronics products authorized critical components life support devices systems without express written approval STMicroelectronics. logo registered trademark STMicroelectronics 2000 STMicroelectronics Printed ITALY- Rights Reserved. STMicroelectronics GROUP COMPANIES Australia Brazil China Finland France Germany Hong Kong India Italy Japan Malaysia Malta Morocco Singapore Spain Sweden Switzerland United Kingdom U.S.A. http://www.st.com

VIPower VB409: OFF-LINE AC/DC CONVERTER Aiello Macina INTROD

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