🔍 Key Concepts

• Difference between linear power supplies (tied to input line frequency) and switching power supplies (operate at much higher frequencies) • Typical switching power supply frequencies used in electronic display systems (order of magnitude: tens to hundreds of kilohertz) • Effect of switching frequency on transformer size and audible noise

💭 Think About

• Which of the choices are close to the power line frequency or its simple multiples, and which are much higher? • For a compact electronic display, would the power supply designer prefer low-frequency (large, heavy magnetics) or higher-frequency (smaller components) operation? • Which frequencies are likely to fall in or near the audible range for humans, and which are clearly above it for quieter operation?

✅ Before You Answer

• Identify which option(s) are related to mains frequency (e.g., 60 Hz and its rectified ripple). • Eliminate any frequency that is too low for a modern switching display supply, considering size and efficiency. • Compare the remaining choices and choose the one that is a realistic, commonly used switching frequency range for compact electronic displays.