Low Voltage Stabilized Power Supply - Essay Example

Almost all electronic circuits need electrical power to operate: this is usually provided by batteries or mains powered power supply. A stabilized power supply is one in which its output is maintained at constant voltage and is not affected by changes in load current.

The low-voltage output is applied to points X & Y from the main transformer after making sure that the link connectors were correctly connected to the board. A green LED illuminated indicating everything was working in the correct form. A multimeter that was set to AC voltage was used to measure the input voltage between X & Y. Since the meter displayed the voltage in Root Mean Square which is also known as RMS, the result had to be multiplied by √2 to give the peak to a peak value (Vpeak = Vrms X √2). The multimeter was then set to DC voltage; the voltage was then measured at A, B, C, and E with respect to point D. The results will be shown in the results section of this report.

The recorded voltage at A (Vad) was compared to the calculated peak value of (Vxy peak). In the ideal conditions, these results should match, but point A got reduced because of the drop in voltage across the rectifier diodes.

The voltage in the terminals of the transistors and the voltage across the 1Ω resistor (which is the voltage between A & C, Vac) were measured and then results were recorded. These results will also be shown in the results section of this report.

The mains power was then switched off and the "Collector Link" was then disconnected. The multimeter was set to DC current measurement. After doing so, the power was then switched back on and the transistor's collector current (Ic) was measured which was possible by connecting the multimeter between the two exposed pins which are the Collector links. The power was switched off once more, the Collector Link was then reconnected but the Base Link was connected this time. The power was switched back on and the transistor's base current (Ib) was measured which was performed by connecting the multimeter between two exposed pins (Base Link pins). The values were recorded and the Base Link connection was restored.

The currents for the emitter and the transistor's collector are almost identical in this setup. The results show that the power supply load current is the same as the current for the transistor collector. The Transistor Current Gain was then calculated.

The mains power was disconnected and also the Capacitor Link in order to eliminate the 1000μF capacitor from the circuit. The power was then connected and an oscilloscope that its input was set to DC and a vertical scale of 2 volts/division and a horizontal scale of 4 or 5 ms/division was used to view the voltage at points C and D. This wave was recorded by saving the display of the oscilloscope's screen via USB memory stick. (Figure 2)

The Capacitor Link was reconnected without any change in the oscilloscope's connections, to restore normal operation. A new waveform was visible on the oscilloscope's display screen, it was recorded and the ripple voltage was measured. (Figure 3)

A simple answer to the question that was given in the lab activity sheet -was "Is it possible to measure any voltage ripple on the waveform here? If so, what is the output peak-to-peak ripple voltage?"- would be: yes, it is possible and the ripples were very little (measured at 40 mV) which is an indication of a fairly high-quality board. And the output peak-to-peak ripple voltage was measured at 640 mV.