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Basic AC-DC Power Supplies
31 questions By Tony R. Kuphaldt
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Question 22 of 31
Complete this schematic diagram, turning it into a split (or dual power supply, with three output terminals: V, Ground, and -V:
Reveal answerExamples of “split” or “dual” power supply schematic diagrams abound in textbooks. I’ll let you do the research here and present your answer(s) during class discussion!
Notes:Students need not provide details of voltage regulation, but merely show how AC from a center-tapped transformer winding may be rectified into two distinct DC outputs with a common “ground” connection.
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Question 23 of 31
Predict how all component voltages and currents in this circuit will be affected as a result of the following faults. Consider each fault independently (i.e. one at a time, no multiple faults):
- Any one diode fails open:
- Transformer secondary winding fails open:
- Inductor L1 fails open:
- Capacitor C1 fails shorted:
For each of these conditions, explain why the resulting effects will occur.
Reveal answer- Any one diode fails open: Half-wave rectification rather than full-wave, less DC voltage across load, more ripple (AC) voltage across load.
- Transformer secondary winding fails open: no voltage or current on secondary side of circuit after C1 discharges through load, little current through primary winding.
- Inductor L1 fails open: no voltage across load, no current through load, no current through rest of secondary-side components, little current through primary winding.
- Capacitor C1 fails shorted: increased current through both transformer windings, increased current through diodes, increased current through inductor, little voltage across or current through load, capacitor and all diodes will likely get hot.
Notes:The purpose of this question is to approach the domain of circuit troubleshooting from a perspective of knowing what the fault is, rather than only knowing what the symptoms are. Although this is not necessarily a realistic perspective, it helps students build the foundational knowledge necessary to diagnose a faulted circuit from empirical data. Questions such as this should be followed (eventually) by other questions asking students to identify likely faults based on measurements.
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Question 24 of 31
Suppose this power supply circuit was working fine for several years, then one day failed to output any DC voltage at all:
When you open the case of this power supply, you immediately notice the strong odor of burnt components. From this information, determine some likely component faults and explain your reasoning.
Reveal answerShorted capacitor, open transformer winding (as a result of overloading), shorted diode(s) resulting in blown fuse.
Notes:Troubleshooting scenarios are always good for stimulating class discussion. Be sure to spend plenty of time in class with your students developing efficient and logical diagnostic procedures, as this will assist them greatly in their careers.
Remind your students that test instrument readings are not the only viable source of diagnostic data! Burnt electronic components usually produce a strong and easily-recognized odor, always indicative of overheating. It is important to keep in mind that often the burnt component is not the original source of trouble, but may be a casualty of some other component fault.
i m using power supply for CCTV PTZ Camera with his adaptor rating of 230v AC input & 24V AC Output ,2A load current. what would be the power consumption is their from the main supply line? means is it taking 2 amp from main line of it would be from the adaptor itself?