The design considerations for both the PNP and NPN transistors are same. Since the diodes are used for biasing, the forward voltage drop across the diodes should be equal to the forward voltage drops across the transistors. Thus R b for each is calculated to be 10 Ohms. The bias resistor is then given byįor each transistor, the V BE(ON) is about 2V. However since this current is more than the maximum base current of the transistor, we prefer a value less than the maximum base current. This gives a bias current of about 0.4A *10, i.e.4A. For this reason we use a power transistor TIP41 with a maximum collector current of 6A, where the base current is given by the collector current divided by the DC current gain. This requires use of high power transistors to allow the flow of maximum amount of current to the load. Switching Circuit Design:Our main aim is to develop an AC signal of 220V. Here we prefer using a 150K potentiometer to fine tune the output signal.Īlso a ceramic capacitor of 0.01uF is used between the control pin and ground. Since our requirement is f =50Hz and D = 50% and assuming C to be 0.1uF, we can calculate the values of R1 and R2 to be 10K and 140K Ohms respectively. Also the duty cycle of the output signal is given by: Where R1 is the resistance between discharge pin and Vcc, R2 is the resistance between discharge pin and threshold pin and C is capacitance between threshold pin and ground. We know, frequency of oscillations for a 555 timer in astable mode is given by: Here an astable multivibrator using 555 timer is designed. Oscillator Design:An astable multivibrator can be used as an oscillator. The frequency of oscillation is determined by the values of capacitor and resistors.Ĭircuit Diagram Circuit Diagram of 12v DC to 220v AC Converter – ElectronicsHub.Org An important use of 555 Timer IC is in its use as an astable multivibrator.Īn astable multivibrator produces an output signal which switches between the two states and hence can be used as an oscillator. Here the collector emitter voltage is minimum and collector current is maximum.Īnother important aspect of this circuit is the oscillator. When the transistor is biased in saturation region, both the collector emitter and collector base junctions are forward biased. For this application, the transistor is biased in saturation and cut-off region. One of the important applications of a transistor is in switching. The reason for using power transistor is they have very low output impedance, allowing maximum current to flow at the output. Normally for low and medium power applications, power transistors are used. Inverter circuits can either use thyristors as switching devices or transistors. To design a 100 watt Inverter read Simple 100 Watt inverter 12v DC to 220v AC Converter Circuit Using Astable Multivibrator In order to increase the capacity of the inverter, the number of MOSFETS must be increased. The transformer combines both the inverting signals to generate a 220V alternating square wave output.īy using a 24V battery, loads up to 85W can be powered, but the design is inefficient. The turns ratio of the transformer must be 1:19 in order to convert 12V to 220V. These amplified signals are given to the step-up transformer with its center tap connected to 12V DC. The inverting signals from the oscillator are amplified by the Power MOSFETS T1 and T4. The formula for the frequency of square wave generated by the astable multivibrator is The values of R1, R2 and C1 (R4, R3 and C2 are identical) will decide the frequency. In the circuit, R1, R2, R3, R4, C1, C2, T2 and T3 form the oscillator.Įach transistor produces inverting square waves. This can be achieved by constructing an Astable multivibrator which produces a square wave at 50Hz. A 50Hz oscillator is required as the frequency of AC supply is 50Hz. The circuit can be divided into three parts: oscillator, amplifier and transformer. 12v-220v center tapped step up transformer.The inverter implemented in this circuit is a square wave inverter and works with devices that do not require pure sine wave AC. It can be used to power lamps up to 35W but can be made to drive more powerful loads by adding more MOSFETS. This primary voltage is then stepped up to a higher voltage depending upon the number of turns in primary and secondary coils.Īlso get an idea about 12V to 24V DC Converter Circuit Inverter circuit Using TransistorsĪ 12V DC to 220 V AC converter can also be designed using simple transistors. The basic idea behind every inverter circuit is to produce oscillations using the given DC and apply these oscillations across the primary of the transformer by amplifying the current. Applications of 12v DC to 220v AC Converter Circuit.12v DC to 220v AC Converter Circuit Operation.12v DC to 220v AC Converter Circuit Using Astable Multivibrator.
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