Advanced Qualification · A-004 Power supplies · A-004-004-011
In a regulated power supply, a diode connected across the input and output terminals of a regulator is used to:
- A provide an RF by-pass for the voltage control
- B provide additional capacity
- C protect the regulator from voltage fluctuations in the primary of the transformer
- D protect the regulator from reverse voltages
Correct answer: D — protect the regulator from reverse voltages. From the official ISED question bank, verified word for word.
Why
When a power supply is turned off, stored energy in nearby capacitors can push current backward through the regulator, creating reverse voltage that may destroy the delicate internal components. The full explanation — and one for every question — is in Pro.
Practise this section
Power supplies: rectifiers, filtering, regulation, switching supplies and their failure modes.