A power supply is a device that supplies electric power to an electrical load. The power supply is needed for our everyday use to charge phones, laptops, to operate every electronic device. There are different circuit diagrams for supplying power. The process of supplying power is divided into four main part which includes,
- Transformers
- Rectifiers
- Smoothing
- Regulating
Figure 1: Power supply block diagram
However we are concerned about designing and building the regulatory aspect of the power supply. Below is the designed circuit diagram for the voltage regulation and its simulations.
Figure 2: proposed power regulator
The above circuit contains two voltage sources, one is an AC while the other is a DC. In this design we are assuming that the voltage from the smoothing capacitor still contains ripples. That is why we have an AC supply from the signal generator.
The operational amplifier uses the negative voltage of the input signal to generate a reference voltage below ground so that the output voltage can be adjusted. The current limiting is accomplished by sensing the voltage drop across a small resistor placed in series with the negative supply line. The output of the Op-Amp reduces the voltage at the base of transistor Q3 in figure 2 which in turn reduces the current to pass transistor Q1 so that the current stays constant. Transistor Q1 and Q2 should be mounted on a heat sink.
The output voltage (voltage across R15) depends on the value of the R12 resistor. The resistor R12 should be above 3.3K ohms to obtain a good output voltage. It should be noted that the higher the value of R12, the lower the output voltage. Below are the simulated waveform's for the AC source signal, input signal and the output signal.
Figure 3: The AC source signal with amplitude of 1V and frequency of 25hertz.
Figure 4 :The total input signal from both the AC source and DC source with of 25V and internal resistance 1 ohm.
From the above simulated waveform's, it can be seen that the circuit design worked properly and there was no ripple on the output.
The next update on this project will try to implement the above design into real practice. Watch out for it.
