12V to 120/230 V AC inverter
Introduction
Whenever an alternate power source of approximately 120 to 220 v AC is required, an inverter circuit is used. An inverter circuit converts rather boosts a low voltage DC supply to a high voltage power supply. Probably, the output voltage will be AC in nature. You can make use of a 12V car battery with higher power ratings to energise the circuit and the resultant output is our required 120/230v AC power supply, which is commonly used to run utility items in our day-to-day life. In the households, we operate lights, fans and motors to run using the AC source from the wall outlets. This inverter circuit is actually very useful during normal power failure periods for running the electrical items. The inverter circuit has to be switched on during emergencies, that is, whenever there is a power failure in the supply line. Actually, by adding a few additional circuits, these inverters can be made automatic.
Obtaining alternating current, i.e. AC from direct current i.e DC is possible by using an electronic device called power inverter. This AC can be used in home electrical devices such as lights and fans etc. Here, a lower DC power source (normally 12 V DC like a car battery) is used to enhance the output AC (normally 230 v AC ), which we use in our households through wall outlets.
How it Works:
Now, let us discuss how the inverter works. The power inverter circuit converts lower DC electricity into higher AC electricity. The conversion is done through electronic switching circuits through which we get a high voltage alternating current waveform. Typically, two types of output waveform are used. The first one is the basic form called ‘modified sine wave’. The second one is ‘pure sine wave’. Cheap inverters adopt the first type, whereas costly one uses the pure sine wave type for better, stable and efficient power supply. Normal electrical appliances such as lights and fans can be used with the modified sine wave. Sensitive and sophisticated appliances require a pure sine wave type.
Know your design
The inverter circuit shown here gives a square waveform output of AC current. The primary of the transformer is center-tapped, and the secondary has just two terminals, from which 230 AC is available in square wave form. Here, the transistors work in the multivibrator mode for fast switching, thereby creating a pulsating current in the primary of the transformer. This current is expanded in the secondary to a higher level, delivering a higher voltage of nearly 230 volts. To drive the transistors a high current low voltage battery is needed. As such a car battery of 12v with 100 to 120 Amps capacity battery is used in the circuit. The design shown here consists of only inverter function. Normally these inverter gadgets come with a battery charger and auto control circuit. The circuit design for such advanced type will be discussed in the coming posts.
Know your assembly
The circuit can be assembled in a vero board for neat placement of components. It is important to observe that the power transistors should be mounted on a very heavy heat sink. Since large amount of heat is produced in the device, heat sink is a must for this inverter. The heavy duty battery is kept outside the circuit. The power transformer is also mounted on a separate enclosure as the size of it is very big and produces heat.
Conclusion
The inverter project is a worth for the households and small commercial places, especially for the use of backup power source and emergency lighting support.
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