This document describes the design of a medium-power, low-cost inverter capable of generating approximately 300VA of power from a car battery. The inverter uses common electronic components like timers, flip-flops, transistors, and MOSFETs to convert the DC battery voltage into a 50Hz AC output that can power lights and other devices. It includes sections on the circuit diagram, block diagram, oscillator, driver circuit, and power amplifier. The inverter is intended for use in rural areas lacking reliable electricity access and has applications for lighting, studying, and portable power. Future developments proposed include adding solar panels to recharge the car battery powering the inverter.

1. MEDIUM-POWER
LOW-COST INVERTER
ATHARVA CHAVAN

2. CONTENTS
1. Introduction
2. Circuit diagram
3. Block diagram
4. Low-battery indicator
5. Oscillator-cum-divider
6. Driver circuit
7. Power amplifier
8. Applications
9. Future development

3. INTRODUCTION
• The main supply supplies us with alternating current (AC) electricity.
• AC is the standard form of electricity.
• AC is used for grid services that connect cities and power plants, because it is
more efficient for long distance transmission.
• An inverter is an electronic circuit that converts direct current (DC) to alternating
current (AC) and also changes it’s voltage.
• An inverter is used as a backup supply, in places were power cutoff is frequent.
• An inverter uses an inverter battery as it’s input supply.

4. INTRODUCTION
• This medium-power inverter is capable of generating approximately 300VA
power. You can power the inverter from your car battery to generate 50Hz AC
supply.
• The inverter provides enough back-up power to light up upto three 100W bulbs
for up to two hours, provided the car battery is fully charged.
• The cost of this inverter circuit is much cheaper than the mainstream inverters.
• The cost of car battery is cheaper than the inverter battery.
• Thus total cost of this inverter is cheaper than the mainstream inverter.

5. CIRCUIT DIAGRAM

6. BLOCK DIAGRAM
CAR
BATTERY
POWER
SUPPLY
OSCILLATOR
CUM
DIVIDER
DRIVER
CIRCUIT
LOAD
CAR
BATTERY
CHARGER
BATTERY
LEVEL
BUZZER POWER
AMPLIFIER
INVERTER
TRANSFORMER

7. LOW-BATTERY INDICATOR
• For long life of the battery, it should not be
allowed to discharge to a voltage below 10V.
• For audio-visual indication of the low-battery
level, a dual operational amplifier IC LM358
has been used.
• A fixed reference voltage of 5.1V is applied to
its positive input, while the sensing voltage is
applied to its negative input.
• Set preset VR1 such that the piezobuzzer
sounds when the on-load battery voltage
falls below 10V DC.

8. OSCILLATOR-CUM-DIVIDER
• The oscillator-cum-divider section is built around timer IC LM555
(IC2) and dual J-K flip-flop 7473 (IC3). Only one flip-flop of the dual
JK flip-flop is used here.
• Timer LM555 is wired as an astable multivibrator, whose time
period is decided by resistors R7 and R8 and capacitor C5.
• It produces 100 Hz at output pin 3, which is given to pin 5 of the J-K
flip-flop to produce 50 Hz medium-power low-cost inverter with
50% duty cycle.
• When the inverter is switched on using switch S1, IC2 starts
producing 100 Hz, while the J-K flip-flop produces 50 Hz at its
output pins 8 and 9.

9. DRIVER CIRCUIT
• The flip-flop output is fed to MOSFET driver
transistors T1 and T2 via a diode-resistor
combination.
• At any instant, if the voltage of pin 8 of IC3 is +5V,
the voltage at its pin 9 will be 0V, and vice versa.
• Whenever output pin 8 of IC3 goes high, NPN
transistor T1 conducts and the corresponding set
of MOSFETs (T3through T5) remains cut off while
the collector of transistor T2 is at 5V.
• Thus current flows through half of the inverter
transformer’s primary winding.

10. POWER AMPLIFIER
• The power amplifier section comprises
two sets of three power MOSFETs
(IRFZ44) connected in parallel for
operation of the inverter.
• The output of IC3 drives the MOSFETs (T3
through T5, and T6 through T8) via
transistors T1 and T2 to generate 50Hz,
230V AC at the output of inverter
transformer X1.

11. APPLICATIONS
• This medium power low cost inverter can be used in rural areas where the electricity is
supplied only for some hours.
• Batteries of tractors or cars can be used as a power supply for the inverter.
• Instead of 100w bulbs, CFL bulbs can be used which are less power consuming and more
efficient, and thus it will increase the backup time of the inverter.
• In rural areas where students depend upon candle light or kerosene lanterns to study, can use
this inverter and study under the bright light of CFL lamps.
• This Inverter is portable and thus can be taken anywhere needed.

12. FUTURE DEVELOPMENT
• IN ORDER TO CHARGE THE CAR BATTERY, SOLAR PANEL CAN BE USED.
• SOLAR PANELS CAN BE COSTLY BUT IT WILL BE A ONE TIME INVESTMENT FOR THE PERSON, THUS HE WILL NOT
BE COMPLETELY DEPENDENT UPON THE ELECTRICITY SUPPLY WHICH IS PROVIDED DURING A VERY SHORT
PERIOD OF THE DAY.

13. THE END
THANK YOU