Test Type-II compensation under a VIN step (12V→15V) and compare with Ch4's proportional feedback.
Stability ultimately manifests in time-domain transient behavior. This lesson repeats the Ch4 L2 test — VIN jumps from 12V to 15V — but with the Type-II compensator. Compare two metrics: steady-state error and transient waveform.
Proportional feedback (Ch4, gain=-10) at VIN=15V: output rises to ~6.1V (error ~0.1V). Type-II compensation: the integrator forces error to zero in steady state, so Vout stays exactly 6V at VIN=15V. The principle: infinite DC gain of the integrator means it keeps integrating as long as any error exists, until error is completely eliminated.
Transient waveform: after the VIN step, the compensator produces a brief, clean, small-amplitude deviation, then quickly returns to target. No ringing, no overshoot — this is the time-domain signature of adequate phase margin. With insufficient PM, you'd see overshoot and decaying oscillations.
Chapter summary: proportional control (Ch4) → limited gain, residual error; high gain without compensation (L1) → oscillation; Type-II compensation (L3-L4) → high accuracy + stability. Compensation is the critical bridge between 'theory' and 'practice' in SMPS design.
VIN 12V→15V. Output precisely holds 6V, clean transient with no ringing. Compare Ch4 L2 (error ~0.1V).
After reading this section, run the simulation and observe the waveforms. To explore further, open the example in a standalone page.