Designing a Voltage Regulated Power Supply

In summary, the conversation discusses a voltage regulated power supply that consists of a full bridge rectifier, filter capacitor, and NPN bipolar junction transistor. It is fed from a 240V 50Hz source and must produce a +15V output for load currents up to 2A. The rectifier diodes have a constant forward voltage drop of 1.0V. The conversation covers the circuit arrangement, calculation of peak rectified voltage, selection of zener breakdown voltage, design of bias resistor, determination of BJT voltages, and calculation of average power dissipated. It is recommended to have practical experience with constructing and investigating such a power supply for better understanding.
  • #1
andyleo
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Homework Statement



A voltage regulated power supply consists of a full bridge rectifier feeding into a filter capacitor,
and then into an NPN bipolar junction transistor (BJT) operating as an emitter follower, and
with the base of the BJT biased using a resistor and a zener diode. The power supply is fed from
a 240V (rms) 50Hz source, which is stepped down through a 15:1 transformer. The power
supply must produce a +15V output for load currents up to 2A. The rectifier diodes have a
forward voltage drop that is a constant 1.0V irrespective of the load current.
a. Sketch the circuit arrangement for this type of voltage regulated power supply.
b. Calculate the peak rectified voltage that appears across the filter capacitor.
c. Select the zener breakdown voltage required to achieve the target regulated voltage.
d. Choose an acceptable voltage ripple for the rectifier, and hence design the required bias
resistor.
e. Determine the maximum and minimum collector-emitter voltages for the BJT.
f. Hence calculate the average power dissipated in the BJT.

Homework Equations



Vz=V°+0.7
Iz*Rz + Ibe*Rz ≤ Vp - Vripple - Vz
I(output current)= C * ( dv/dt )

The Attempt at a Solution



I took a photo of what I did so far ... :
http://imageshack.us/photo/my-images/573/img00289201110260009.jpg/I'm not sure how I would solve this problem .. can you guys help me ?I was good with the sketch, I'm not sure about the rectified voltage and the BJT voltages required it to operate... I'm lost please HELP!
 
Last edited:
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  • #2


It helps considerably if you have constructed & investigated such a power supply. I think it would be difficult if you haven't. Three is no substitute for hands-on practical lab work.
 

1. What is a voltage regulated power supply?

A voltage regulated power supply is an electronic device used to provide a constant and stable output voltage to power electronic circuits or devices. It is designed to protect sensitive electronic components from voltage fluctuations and ensure that they receive a consistent and appropriate level of power.

2. Why is voltage regulation important in a power supply?

Voltage regulation is important because electronic devices require a specific and consistent voltage to function properly. Any fluctuations or deviations in voltage can cause damage to the components or result in unreliable performance. A voltage regulated power supply ensures that the output voltage remains within a specific range, providing the necessary stability for electronic devices to operate efficiently.

3. What are the key components of a voltage regulated power supply?

The key components of a voltage regulated power supply include a transformer, rectifier, filter, and voltage regulator. The transformer converts the input voltage to a lower or higher value, depending on the desired output. The rectifier converts the AC voltage to DC, and the filter removes any remaining AC components. The voltage regulator then regulates the output voltage to the desired level.

4. How do you design a voltage regulated power supply?

The design of a voltage regulated power supply involves selecting appropriate components and calculating the necessary values for each component based on the desired output voltage and current. This includes determining the transformer turns ratio, selecting the appropriate rectifier and filter components, and choosing a suitable voltage regulator. The design process also involves testing and adjusting the circuit to ensure the desired output is achieved.

5. What are the advantages of using a voltage regulated power supply?

There are several advantages to using a voltage regulated power supply, including stable and consistent output voltage, protection for electronic devices, and improved efficiency. Additionally, a voltage regulated power supply can be designed to provide multiple output voltages, making it versatile for various electronic circuits and devices. It also helps reduce noise and interference in the power supply, ensuring reliable performance of electronic components.

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