Rise time is defined as the time required for the power supply output voltage to transition from 10% to 90% of its rated value. This characteristic is a critical indicator of power supply responsiveness and directly impacts the stability and reliability of digital circuits and sensitive sensor applications.
Here, t10 % represents the timestamp when the output voltage reaches 10% of the rated value, and t90% represents when it reaches 90%. For example, consider a 5 V power supply. If the output reaches 0.5 V (10%) at 0.5 ms and 4.5 V (90%) at 1.5 ms, the rise time is 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
Ideally, rise time must be optimized for the specific load. Extremely fast rise times can generate significant inrush currents, potentially stressing internal components or triggering protection circuits. Conversely, slow rise times may prevent digital circuits from initializing correctly, leading to startup failures or logic errors.
In complex systems, power sequencing is also critical. For circuits requiring multiple voltage rails, the timing and order of power-up events affect overall functionality. Engineers often use sequence control ICs or soft-start functions to precisely manage rise times and ensure safe, synchronized system startup.