Today electricity has become the life line of all cities and even the rural areas. With depleting fossil fuel, sun light promises to be one of the major renewable source of energy that can be accessed directly from anywhere and under all circumstances on this planet, free of cost. Let's learn one of the methods of converting solar energy into electricity for our personal benefits.
In one of my previous posts I have discussed a solar inverter circuit which rather had a simple approach and incorporated an ordinary inverter topology using a transformer.
Transformers as we all know are bulky, heavy and may become quite inconvenient for some applications.
In the present design I have tried to eliminate the use of a transformer by incorporating high voltage mosfets and by stepping up the voltage through series connection of solar panels. Let's study the whole configuration the with the help of the following points:
Looking at the circuit diagram, we can see that it basically consists of three main stages, viz. the oscillator stage made up of the versatile IC 555, the output stage consisting of a couple of high voltage power mosfets and the power delivering stage which employs the solar panel bank, which is fed at B1 and B2.
Since the IC cannot operate with at voltages more than 15V, it is well guarded through a dropping resistor and a zener diode. The zener diode limits the high voltage from the solar panel at the connected 15V zener voltage.
However the mosfets are allowed to be operated with the full solar output voltage, which may lie anywhere between 200 to 260 volts. On overcast conditions the voltage might drop to well below 170V, So probably a voltage stabilizer may be used at the output for regulating the output voltage under such situations.
The mosfets are N and P types which form a pair for implementing the push pull actions and for generating the required AC.
The mosfets arenot specified in the diagram, ideally they must be rated at 450V and 5 amps, you will come across many variants, if you google a bit over the net.
The used solar panels should strictly have an open circuit voltage of around 24V at full sunlight and around 17V during bright dusk periods.
R1 = 6K8
R2 = 140K
C1 = 0.1uF
Diodes = are 1N4148
R3 = 10K, 10 watts,
R4, R5 = 100 Ohms, 1/4 watt
B1 and B2 = from solar panel
Z1 = 5.1V 1 watt
Use these formulas for calculating R1, R2, C1....
The above 555 IC design may not be so reliable and efficient, a much reliable design can be seen below in the form of a full H-bridge inverter circuit. This design can be expected of providing much better results than the above 555 IC circuit
Another advantage of using the above circuit is that you won't require a dual solar panel arrangement, rather a single series connected solar supply would be enough to operate the above circuit for achieving a 220V transformerless inverter output.