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In this article, we are going to instigate a simple Uninterruptible power supply (UPS) using a 12V battery. We are going to explain these UPS circuits very simply so that a new electronics student can understand. These UPS circuits can be used for operating a specific appliance or load.
In this circuit idea, we can build at home using the most ordinary or commonly used components to produce a reasonable output. This simple UPS circuit can be used not only for the usual electrical load but also in complex gadgets like computer supplies. This inverter circuit utilizes a modified sine wave design. UPS power supply features may not be critically required for the operation of sophisticated circuits. This uninterruptible power supply presented here can well suffice the requirement. This inverter circuit includes a Built-in universal battery charger also.
The IC1 SN74LVC1G132 has a single NAND gate encapsulated in a small package. It is the heart of the oscillator stage and requires just one capacitor and one resistor for the required oscillations. The value of these two passive components determines the frequency of the oscillator and can be changed as u want and this frequency is around 250 Hz.
The generated frequency is applied to the next stage consisting of a single decade counter IC 4017. The IC 4017 is configured so that its outputs produce and repeat a set of five sequential logic high outputs. in this, the input Is a square wave so generated output is also a square wave.
The base leads of two pairs of Darlington paired high gain, hi-power transistors are attached to the IC such that it receives and conducts to the alternate outputs power.
Since the base voltages to the transistors from the IC are skipped, the resultant square impulse from the transformer carries only 1/2 the average value compared to the other inverters. This dimensioned RMS average power of the generated square waves very much resembles the average value of the mains AC that is normally available at our home power sockets and thus becomes suitable for most sophisticated electronic gadgets.
this uninterruptible power supply design is fully automatic and will revert to the inverter mode the moment input power fails. This is done through a couple of relays; RL2 has a dual set of contacts for reversing both output lines.
Components required for Charger Circuit