Ham Radio General Class Practice Test

Which of the following is an important characteristic for capacitors used to filter the DC output of a switching power supply?

1. Low equivalent series resistance

2. High equivalent series resistance

3. Low Temperature coefficient

4. High Temperature coefficient

The correct answer is: Low equivalent series resistance

The important characteristic for capacitors used to filter the DC output of a switching power supply is low equivalent series resistance (ESR). Low ESR is critical in this application because it minimizes energy losses that can occur due to the internal resistance of the capacitor when it is in operation. In switching power supplies, the rapid changes in voltage can lead to high ripple currents passing through the capacitors. A capacitor with low ESR will reduce the generation of heat and improve the efficiency of the power supply, as less energy is wasted as heat due to resistive losses. Additionally, low ESR helps maintain stable output voltage and reduces the risk of voltage overshoot during abrupt load changes. Capacitors with high ESR would experience greater losses, potentially leading to overheating and decreased reliability over time. Similarly, the temperature coefficients are relevant for thermal stability and performance but do not directly relate to the filtering efficiency of capacitors in a switching power supply as closely as ESR does. Therefore, having capacitors with low equivalent series resistance is crucial for optimal performance in this context.