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Regulated Power Sources
28 questions By Tony R. Kuphaldt
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Question 28 of 28
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):
- Zener diode fails shorted:
- Zener diode fails open:
- Series resistor fails open:
- Series resistor fails shorted:
For each of these conditions, explain why the resulting effects will occur.
Reveal answer- Zener diode fails shorted: Little voltage across load, increased voltage across Rseries, increased current through source and Rseries.
- Zener diode fails open: Increased voltage across load, decreased voltage across Rseries, decreased current through source and Rseries.
- Series resistor fails open: No voltage across D1 or load, no current through D1 or load, no current through source.
- Series resistor fails shorted: Full source voltage across load and D1, greatly increased current through D1, increased current through source, D1 will most likely overheat and fail.
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.
