| Parameter | Value | Unit |
|---|---|---|
| Average output voltage | — | V |
| Output power | — | W |
| Ripple current ΔIL | — | A |
| Ripple ratio | — | % |
| Switching loss | — | W |
| Conduction loss | — | W |
| Total loss | — | W |
| Estimated efficiency | — | % |
| Filter cutoff f_c | — | Hz |
| f_sw / f_c ratio | — | — |
Theory Notes
Average voltage and ripple current:
$$V_{\text{avg}} = D \cdot V_{\text{in}}, \quad \Delta I_L = \frac{(V_{\text{in}} - V_{\text{avg}}) \cdot D}{L \cdot f_{\text{sw}}}$$Switching and conduction losses:
$$P_{\text{sw}} = \frac{1}{2} V_{\text{in}} \cdot I_{\text{out}} \cdot (t_r + t_f) \cdot f_{\text{sw}}$$ $$P_{\text{con}} = I_{\text{out}}^2 \cdot R_{\text{DS(on)}} \cdot D$$LC filter cutoff:
$$f_c = \frac{1}{2\pi\sqrt{LC}}$$Engineer Dialogue — "Why go to higher switching frequency?"
🧑🎓 "I keep hearing that higher PWM frequency is better — what's the actual benefit?"
🎓 "Higher frequency means shorter switching periods, so you can achieve the same ripple current with a smaller inductor. That directly translates to smaller, lighter hardware. EV inverters operate at 20–100 kHz partly for this reason."
🧑🎓 "So why not just go to 1 MHz?"
🎓 "Switching losses scale with frequency. Every time the MOSFET switches, there's an overlap of voltage and current that dissipates heat. At 100 kHz you might have 2 W of switching loss — scale to 1 MHz and that becomes 20 W. You'd need to massively over-size the heatsink."
🧑🎓 "Is that where SiC and GaN come in?"
🎓 "Exactly. SiC and GaN have switching times 5–10× shorter than silicon MOSFETs, so the switching loss per cycle drops dramatically. That's why EV on-board chargers now run at 200–400 kHz with SiC — smaller magnetics, higher power density, same efficiency."