Key Takeaways
- VIN changes → Vout changes proportionally (with fixed D)
- Load variation + input variation = dual problem, both require automatic D adjustment
Lesson 2
Input Voltage Step: Output Drifts Along
VIN steps from 12V to 15V, Vout immediately rises from 6V to 7.5V — open-loop is equally helpless against input changes.
Besides load changes, input voltage fluctuation is common in practice: battery discharges from 4.2V to 3.0V, automotive 12V drops to 9V during cranking, adapter output varies ±10% due to grid fluctuation.
Vout = D × VIN: when VIN changes but D doesn't, output shifts linearly. VIN up 25% (12→15V), Vout up 25% (6→7.5V).
VIN Step: 12V → 15V
At t=10ms VIN jumps to 15V. Output rises from ≈6V to ≈7.5V, no auto-correction.
After reading this section, run the simulation and observe the waveforms. To explore further, open the example in a standalone page.
Watch Items
- out jumps from ≈6V to ≈7.5V at t≈10ms