Boost Converter Calculator
Design boost (step-up) DC-DC converters. Calculate inductor, capacitor values, and component ratings for your power supply.
Calculator
Enter values and click Calculate
How to Use This Calculator
This boost converter calculator helps you design step-up DC-DC power supplies by calculating the key component values needed for your application.
- Select a Common IC — Or enter your own input/output specifications
- Set Voltages and Current — Define input voltage, output voltage, and load current
- Choose Switching Frequency — Higher frequency = smaller components, but more losses
- Set Ripple Requirements — 30% inductor ripple and 50mV output ripple are typical
- Adjust Efficiency — Start with 85% and adjust based on IC datasheet
- Click Calculate — Get component values and design recommendations
Boost Converter Theory
A boost converter is a DC-DC switching regulator that steps up voltage while stepping down current. It's more efficient than linear regulators because it uses switching rather than dissipating excess power as heat.
Basic Operation
- Switch ON: Current flows through inductor, storing energy in its magnetic field
- Switch OFF: Inductor releases energy through diode to output
- Output Capacitor: Smooths the pulsating current to provide steady DC
Key Formulas
Boost vs Buck Converter
| Aspect | Boost | Buck |
|---|---|---|
| Voltage | Steps up (Vout > Vin) | Steps down (Vout < Vin) |
| Current | Iout < Iin | Iout > Iin |
| Switch Stress | Higher (sees Vout) | Lower (sees Vin) |
| Input Current | Continuous | Pulsating |
Component Selection
Inductor Selection
| Parameter | Requirement | Reason |
|---|---|---|
| Inductance | Calculated value ±20% | Controls ripple current |
| Saturation Current | > Peak current × 1.3 | Prevents core saturation |
| DC Resistance (DCR) | As low as possible | Reduces I²R losses |
| Core Material | Ferrite or powdered iron | Low core losses at frequency |
Diode Selection
The boost diode sees the full output current and must handle high-frequency switching. Schottky diodes are preferred for their low forward voltage drop.
| Type | Vf | Best For |
|---|---|---|
| Schottky | 0.3-0.5V | High efficiency, most applications |
| Ultrafast | 0.8-1.0V | High voltage (Vout > 100V) |
| Synchronous FET | I×Rds(on) | Maximum efficiency |
Output Capacitor Selection
Output capacitor ESR is critical in boost converters because it's the main contributor to output ripple voltage. Use multiple ceramic capacitors in parallel or low-ESR electrolytics.
Design Tips
Layout Best Practices
- Keep the power stage loop (switch, diode, output cap) as small as possible
- Place input capacitor close to IC power pins
- Use wide traces for high-current paths
- Keep feedback resistors away from noisy switching nodes
- Use ground plane on bottom layer
Duty Cycle Limitations
| D < 50% | Optimal efficiency, easy control |
| 50% < D < 80% | Acceptable, watch for stability |
| D > 80% | Difficult to regulate, consider different topology |
Common Mistakes to Avoid
- Using inductor with insufficient saturation current rating
- Ignoring diode reverse recovery losses at high frequency
- Poor layout causing excessive EMI and noise
- Not accounting for input current (much higher than output)
- Insufficient input capacitance for pulsating current
Frequently Asked Questions
What's the maximum boost ratio I can achieve?
Practically, boost ratios up to 4:1 or 5:1 are achievable with good efficiency. Higher ratios require very high duty cycles which become difficult to regulate and suffer from poor efficiency. For ratios above 5:1, consider a flyback or coupled-inductor topology.
Why is my boost converter not starting?
Common causes include: insufficient input voltage for the IC's minimum Vin, soft-start capacitor too large, feedback network incorrect, or enable pin not properly connected. Check that output voltage is close to input voltage at startup (the converter starts from Vin).
Can I use a boost converter for battery-powered devices?
Yes, boost converters are ideal for battery-powered devices. They can maintain a stable 3.3V or 5V output as battery voltage drops. Look for ICs with low quiescent current for battery applications, and consider those with a bypass mode when Vin > Vout.
How do I reduce output voltage ripple?
Add more output capacitance (especially low ESR ceramics), increase switching frequency, or add an LC post-filter. Note that increasing inductor value reduces ripple but makes transient response slower.
Synchronous vs. non-synchronous boost - which should I use?
Synchronous (using a MOSFET instead of diode) is more efficient, especially at high currents and low output voltages. Non-synchronous (diode) is simpler, cheaper, and has inherent reverse-blocking capability. For battery-powered applications, synchronous is usually preferred.
Verify Your Component Selections
After calculating your component values, use Schemalyzer to verify your schematic design. Our AI-powered analysis catches common errors and suggests improvements.
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