Self Switching Off Power Supply-ppt 23q4o

A mini project on: SELF SWITCHING POWER SUPPLY

UNDER THE ESTEEMED GUIDENCE OF MR.M.SUMAN Asst.Prof

Presented by: BATCH NO:5 PROJECT 1. K.SINDHU 2. M.N.MALLESWARI 3.RAMEEZ SHAIK 4.N.SAI SRAVANTHI

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CONTENTS • • • • • • • • • •

OBJECTIVE NEED OF SELF SWITCHING POWER SUPPLY INTRODUCTION CIRCUIT DIAGRAM MAIN COMPONENTS USED OPERATION ADVANTAGES APPLICATIONS CONCLUSION REFERENCES

OBJECTIVE • To design a circuit which switches off itself when load is disconnected. •To provide better flexibility and safety.

NEED OF SELF SWITCHING POWER SUPPLY:• Power supply is a device which converts the available power of one set of characteristics into another set of characteristics to meet specified requirements. • Conventional series regulated linear supplies maintain a constant voltage by dissipating excess power in ohmic losses. • The linear regulator can therefore tend to be very inefficient.

SELF SWITCHING POWER SUPPLY • Supplies power through low loss components such as capacitors,transformers,switches. • Converts 230v a.c supply to 3.7 to 8.7 d.c supply. • Switches off itself when load is disconnected across its output terminals,eliminating power losses.

CIRCUIT DIAGRAM

MAIN COMPONENTS USED • • • • • • • • •

Transformer (230/12V,50HZ,250mA) Push-to-on switch Bridge rectifier(1A) Relay(12V,200ohms) Transistors(BC147,BC157) Voltage regulated IC7805 LED Diodes(1N4007) Resistors and capacitors

OPERATION

• Self switching power supply requires 12v a.c but the available supply is of 230v a.c ,hence a step down transformer is used. • A bridge rectifier is used to convert this a.c to d.c. • A filter is used to remove the ripples. • A voltage regulated IC is used to get fixed d.c.

• When load is connected,the potential drop across diodes D1 and D2 makes transistors T2 and T1 to conduct. • As a result relay gets energised and remains in that state as long as the load is connected. • At the same time capacitor C2 gets charged through T2.

• When load is disconnected transistor T2 is cutoff. • C2 starts discharging through the base of transistor T1. • Relay gets de-energised,switching off the mains input to the primary of the transformer.

ADVANTAGES • self switching facility provides less power loss . • Low cost. • Portable. • Life span of electronic equipments increases.

APPLICATIONS • Used in variable laboratory applications,where we need variable voltages in different levels. • Used in toys,working at these limited voltages. • Used for protection of electronic equipments.

FUTURE SCOPE • Though in the prototype a transformer with a secondary voltage of 12v,250mA was used it can be changed as per ’s requirement. • In that case IC should be provided with a heat sink.

• Potentiometer,relay ratings should be changed accordingly.

CONCLUSION • Hence a power supply circuit is designed which switches off itself when load is disconnected.

REFERENCES • M D Singh, K B Khanchandani,”Power Electronics”, Published by Tata McGraw-Hill companies, Electrical &Electronics Engineering Series, Second Edition • Power Electronics Handbook by Muhammad H.Rashid, second edition. • www.electronicsforyou.com

• THANK YOU