qspice-power-electronics

name	qspice-power-electronics
description	Simulate and characterize switching power converters in QSpice. Use for buck/boost/SMPS work — staging transient and AC analyses, measuring efficiency and step response, and assessing loop gain, phase margin, and gain margin for stability.
license	MIT
metadata	{"author":"qspice-mcp","version":"1.0"}

QSpice: Power Electronics

A workflow for switching converters (buck, boost, SMPS): get a working transient, then characterize efficiency, transient response, and control-loop stability.

When to use

• Designing or analyzing a DC-DC converter or other switching power stage.
• You need efficiency, output ripple, load-step response, or loop-gain / phase-margin numbers — not just "does it run."

When NOT to use

• The run won't converge or stops early → qspice-convergence-debugging first.
• Generic single-node waveform reads/metrics → qspice-waveform-analysis.

Workflow

1. Get a circuit. materialize_reference_circuit for a bundled starting point (e.g. buck_converter_cpp), or author your own. inspect_schematic to confirm topology; check_schematic for a conservative ERC pass (floating nets, single-pin nets, missing ground) before spending sim time.
2. Transient first. prepare_transient to stage a .tran directive long enough to reach steady state plus the events you care about, then run_simulation.
3. Characterize the output. read_waveform on the switching node and output; measure_step_response for rise time / overshoot / settling on a load or reference step; measure_efficiency from input/output power traces.
4. Assess the loop. prepare_loop_gain_analysis (Tian or Middlebrook injection) + prepare_ac, run, then measure_stability_margins for crossover frequency, phase margin, and gain margin.

What "good" looks like

Metric	Tool	Sanity check
Regulation	read_waveform / measure_waveform	V(out) settles near target
Ripple	read_waveform	Output ripple within spec at steady state
Efficiency	measure_efficiency	Pout/Pin physical (<1), losses reasonable
Transient	measure_step_response	Bounded overshoot, settles, no sustained ring
Stability	measure_stability_margins	Phase margin typically ≥ 45°, positive gain margin

Conventions

• Simulate to steady state before measuring ripple/efficiency — early transient windows skew averages.
• Run check_schematic before long transient sweeps; a floating feedback node is cheaper to catch statically than after a failed multi-second run.
• For loop gain, keep the injection method consistent between staging and margin measurement.