Rise time refers to the duration from the moment a power supply output is enabled until the output voltage transitions from 10 % to 90 % of its rated value. This characteristic serves as a crucial indicator of power supply responsiveness and significantly impacts the reliability of digital circuits and sensor applications.
where t10 % represents the time when output voltage reaches 10 % of the rated value and t90 % represents the time when it reaches 90 %. For example, with a 5 V-rated power supply that reaches 0.5 V (10 %) at 0.5 ms and 4.5 V (90 %) at 1.5 ms, the rise time equals 1.0 ms.
- Linear power supplies: 20-50 ms
- Switching power supplies: Less than 1 ms
- High-speed high-voltage (HV) modules: Several tens of microseconds
Excessively short rise times can generate large inrush currents, potentially stressing circuits and the power supply itself. Conversely, overly long rise times may prevent proper digital circuit initialization, leading to malfunctions or startup failures. Therefore, achieving an appropriate balance during design is essential.
System-wide startup sequence compatibility also proves critical, particularly in multi-supply circuits where power-up timing and sequencing can affect overall functionality. To address these requirements, engineers commonly employ power sequencing control ICs and soft-start functions to precisely control and optimize individual power supply rise times.