| 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
- 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.
- Transient first.
prepare_transient to stage a .tran directive long
enough to reach steady state plus the events you care about, then
run_simulation.
- 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.
- 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.
