Four-switch buck-boost converter
Regulated ideal CCM/DCM states, operating-corner sweep, component stress and a separate loss budget.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
Assumptions
- Reported maxima are over the shown input/load samples and mode boundaries; the analytic CCM buck input-capacitor RMS stationary point is included when in range. They are not a proof of all nonlinear operating extrema.
- Power-stage duty and currents are regulated ideal-circuit values. Losses are evaluated afterward; the displayed efficiency is not fed back into ideal conversion equations.
- Diode emulation uses a zero-current idle interval in DCM. Forced PWM permits negative current; boundary conduction is reported as CCM.
- Ripple sums integrated capacitor charge, ESR step and an ESL edge estimate. ESR/ESL values are per capacitor, and identical parallel current sharing is assumed.
- Losses use operating-temperature resistances, constant diode drop, hard-switching overlap and energy-equivalent Coss. Core loss, reverse recovery, dead time and control power are excluded.
- Four-switch automatic mode selects buck, boost or ideal pass-through. Real transition hysteresis and minimum pulse control are controller-specific; conduction losses conservatively include an extra series FET.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Minimum input voltage
- 6 V
- Nominal input voltage
- 12 V
- Maximum input voltage
- 18 V
- Output-voltage magnitude
- 12 V
- Minimum load
- 0.02 A
- Maximum / design load
- 1 A
- Switching frequency
- 200000 Hz
- Chosen inductance
- 0.000047 H
- Nominal output capacitance
- 0.0001 F
- Parallel output capacitors
- 1
- Capacitance retained after bias/tolerance
- 0.7
- Each output-capacitor ESR
- 0.02 Ω
- Each output-capacitor ESL
- 1e-9 H
- Output ripple target
- 0.05 V
- Inductor ripple target / average
- 0.3
- Inductor winding resistance
- 0.05 Ω
- Switch RDS(on) at operating temperature
- 0.03 Ω
- Rectifier forward drop
- 0.5 V
- Synchronous rectifier RDS(on)
- 0.02 Ω
- Each switching transition time
- 2e-8 s
- Switch gate charge
- 2e-8 C
- Gate-drive voltage
- 5 V
- Energy-equivalent switch Coss
- 1e-10 F
- Minimum controller current limit
- 4 A
- Inductor saturation current
- 4 A
- Controller maximum duty
- 0.95
- Controller minimum on-time
- 5e-8 s
- Controller minimum off-time
- 5e-8 s
- Ambient temperature
- 25 °C
- Switch assembly thermal resistance
- 40 K/W
- Rectifier / conduction control
- forced
- Four-switch modulation
- auto
Results
- Output voltage target
- 12 V
- Chosen inductance (nominal pass-through)
- 0.000047 H
- Nominal duty
- 0
- Nominal conduction mode
- Ideal pass-through
- Target L for nominal CCM ripple
- 0 H
- Critical inductance at maximum load
- 0 H
- CCM/DCM boundary load
- 0 A
- Inductor average current
- 1 A