Boost Converter Designer

Design step-up switching regulators.

Input Voltage (V)

Output Voltage (V)

Output Current (A)

Switching Freq (kHz)

Inductor Ripple Current (%)

Duty Cycle -- %

Inductor (L) -- µH

Capacitor (C) -- µF

What is a Boost Converter?

A Boost Converter (step-up converter) is a DC-to-DC switching converter that steps up voltage while stepping down current. It allows you to create a higher output voltage than your input voltage, which is impossible with linear regulators.

It works by storing energy in an inductor when the switch is closed, and then dumping that energy—plus the input voltage—into the output capacitor when the switch opens. "Boosting" the voltage comes at the cost of higher input current.

Calculating Component Values (Formulas)

We need to determine the Duty Cycle, Inductance, and Output Capacitance to ensure stable operation.

1. Duty Cycle (D)

D = 1 - (V_in / V_out) × Efficiency

(Ideal D = 1 - Vin/Vout)

2. Inductor Selection (L)

Inductance is chosen to set the ripple current (ΔI_L) to about 30-40% of the input current.

L = (V_in × (V_out - V_in)) / (ΔI_L × f_sw × V_out)

3. Capacitor Selection (C)

Boost converters are "discontinuous" at the output, meaning the capacitor must supply the entire load current while the switch is on.

C_min = (I_out × D) / (f_sw × ΔV_out)

Practical Applications

LED Drivers: Boosting 3V from a battery to 30V to drive a long string of LEDs in series.
USB Power Banks: Boosting the 3.7V Li-Ion battery voltage to 5.0V for the USB output.
Nixie Tubes: Generating 180V from a 12V supply to power vintage gas-discharge displays.

FAQ

Can a Boost Converter step down voltage?

No. A standard boost converter's output voltage must always be higher than the input. If Vin > Vout, current will flow uncontrollably through the inductor and diode to the load, potentially damaging the circuit. You need a Buck-Boost converter for that.

Why is my Boost Converter getting hot?

Heat usually comes from the MOSFET or Diode. If the duty cycle is very high (>80%), the switch is on most of the time, leading to massive conduction losses. Try to keep the Vout/Vin ratio below 4:1 for a single stage.

What is the "Right Half Plane Zero"?

This is a complex stability issue in boost converters. Effectively, if you suddenly ask formore power by increasing the duty cycle, the current initially drops before rising. This makes control loop design (PID) harder than for buck converters.