A switching regulator's efficiency is often determined by what factor?

The efficiency of a switching regulator is largely influenced by the duty cycle of the switching. The duty cycle refers to the ratio of the time the switch is on to the total time of the switching cycle. It directly affects how long the energy is transferred from the input to the output during each cycle.

A higher duty cycle means that the regulator is spending more time in the "on" state, which can lead to increased energy transfer to the output but can also lead to higher losses due to switching. Conversely, a lower duty cycle reduces the energy transferred but can improve efficiency in certain contexts. Therefore, understanding and optimizing the duty cycle is key to maximizing the regulator's efficiency, as it directly impacts how effectively the input power is converted to the output power while minimizing losses.

The other factors listed do play a role in the overall performance of a switching regulator, but they do not have as direct an impact on efficiency as the duty cycle. For instance, input ripple current and load impedance influence other aspects of design and performance, while transistor junction temperature affects longevity and reliability rather than direct efficiency calculations. Thus, the duty cycle stands out as the primary factor affecting a switching regulator's efficiency.