Simple 37V to 5V Voltage Step-Up Converter Schematic
For a reliable step-up solution, use an MT3608 module. Its input range of 2.0–24V pairs well with a single-cell lithium source, delivering 5V/2A output without heatsinks up to 300 mA. Solder the feedback resistors (R1=68K, R2=22K) directly to the module pads to sidestep PCB trace noise; this ratio yields 4.98V ±0.1% under load. Keep the inductor (4.7 µH, 1.5 A saturation) within 12 mm of the IC to minimize EMI.
When prototyping, bypass the MT3608’s onboard diode (SS34) with a 1N5819 schottky if efficiency above 85% is critical–this swap cuts forward drop to 0.3V and trims standby current to 6 µA. Connect EN pin straight to Vin through a 10K pull-up if automatic start is needed; omit for manual enable via tactile switch. Always solder a 22 µF X7R ceramic across both input and output terminals to suppress voltage ripple below 30 mV peak-to-peak.
For cost-sensitive designs under 500 mA load, substitute the MT3608 with a discrete MC34063 circuit. Configure timing capacitor (470 pF) and sensing resistor (0.22 Ω, 1%) to target 28 kHz switching; this prevents audible whine. Use a 47 µH toroidal inductor rated 950 mA DC resistance ≤0.2 Ω for minimal core loss. Output capacitor must be 100 µF tantalum or 47 µF ceramic; tantalum gives 2% tighter regulation, ceramic slashes ESR to 5 mΩ.
Verify thermal performance with a FLIR E4 at 400 mA load–MT3608 die should stabilise below 55 °C; anything hotter demands a 6.5 mm² copper pour on the bottom layer. Isolate sensitive microcontrollers at least 15 mm away; route ground return paths through a star topology to avoid ground bounce corrupting ADC readings.
Step-Up Voltage Adapter: Hands-On Build Instructions
Select a low-power MT3608 module for boosting single-cell lithium outputs to a stable 4.8–5.2 V range without overheating. Solder the input pads directly to the battery’s positive and negative terminals, ensuring the trace width can handle at least 1.5 A continuous draw. The feedback resistors–typically 100 kΩ between FB and GND, plus 820 kΩ between FB and Vout–must be precision 1 % tolerance to prevent overshoot that could damage microcontrollers.
Component Placement and Thermal Considerations
Position the inductor as close as feasible to the IC’s SW pin to minimize parasitic inductance, which degrades efficiency. Use a 22 µH, 2 A-rated, shielded inductor; its saturation current rating should exceed the expected load by 30 %. Apply a heatsink–even a small copper pad–underneath the IC if ambient temperatures exceed 40 °C or if the output current surpasses 0.8 A. Include a 10 µF ceramic input capacitor rated at 6.3 V or higher within 2 mm of the input pads to suppress ripple at high switching frequencies.
For load regulation, add a 47 µF tantalum output capacitor with an ESR below 50 mΩ close to the output terminals. Verify the entire boost stage on an oscilloscope: set the trigger level just above the expected ripple, confirm the switching waveform remains below 50 mV peak-to-peak at full load, and ensure the frequency stabilizes around 1.2 MHz. Any deviation suggests incorrect feedback resistor values or a faulty inductor; recalibrate or replace components until clean, stable power is achieved.
Core Elements for Boosting a Single-Cell Li-Ion Output to USB Power Levels
The heart of any voltage escalation setup is the switching regulator IC. Look for parts like the MT3608, XL6009, or TPS61090–each engineered to handle the gap between ~4.2 V peak and 5 V with minimal losses. The MT3608, for instance, delivers 2 A output at 93 % efficiency when fed from a 3.3 V source, while the XL6009 tolerates inputs down to 3 V and pumps up to 4 A. Match the IC’s quiescent current (
Inductors determine ripple, efficiency, and footprint. Use a shielded drum core in the 10–22 μH range; anything lower risks saturation, anything higher saps transient response. A 22 μH coil with ≤ 30 mΩ DCR and ≥ 2 A saturation current keeps ripple below 20 mVpp at 1 MHz. Pair it with the regulator’s internal compensation network–some ICs (e.g., MT3608) require only a single 22 pF feedback cap, simplifying layout.
| Part | Value Range | Critical Tolerances | Example PN |
|---|---|---|---|
| Inductor | 10–22 μH | ≤ 30 mΩ DCR, ≥ 2 A Isat | SL2520-220M-R |
| Input Cap | 10–22 μF | ≥ 6.3 V, X5R/X7R | GRM188R60J226MEA0 |
| Output Cap | 22–47 μF | ≥ 6.3 V, X5R/X7R | GRM21BR60J476ME15 |
| Schottky | – | ≤ 0.3 V Vf, ≥ 1 A | SS14 |
Output capacitance dictates load-step recovery. Fit at least 22 μF of low-ESR ceramic (X5R/X7R) directly across the IC’s output pins; 47 μF yields sub-30 μs response for 500 mA load jumps. Add a 0.1 μF bypass cap at the input to absorb sourcing transient spikes–omitting it risks lock-up during brown-in events.
Diode selection is often overlooked yet pivotal. A fast-switching Schottky (≤ 30 ns trr) with ≤ 0.3 V forward drop minimizes conduction losses. The SS14 or B540C handle 1 A continuous, 4 A surge, and drop only 0.28 V at 500 mA. Reverse leakage (
Feedback resistors set the exact output level. Use 1 % tolerance SMD parts; a 240 kΩ (R1) and 180 kΩ (R2) combo targets 5.0 V from the MT3608’s 0.6 V reference. For USB compliance, trim output to 5.00 ± 0.25 V–adjust R1 down to 220 kΩ if necessary. Keep trace stubs
Step-by-Step Wiring of a Voltage Step-Up Module for Single-Cell Lithium Power Sources
Begin by connecting the positive terminal of the 1S Li-ion cell directly to the input anode of the MT3608 or similar switching regulator board. Use 22 AWG silicone wire for flexibility and heat resistance–avoid stranded copper if vibration is a factor, as it can loosen over time. The negative terminal must link to the board’s ground pad; ensure this trace is shorter than 10 cm to minimize voltage drop under load.
Install a 10 µF input capacitor between the power source’s terminals, within 2 mm of the regulator’s pins. This suppresses switching noise that can corrupt nearby sensors or radios. Set the output voltage with a multiturn potentiometer: turn clockwise to raise beyond the 5 V target until a multimeter reads 5.2 V, then fine-tune back to 5.0 V to account for load regulation sag. Secure the potentiometer with a dab of needle-nose pliers to prevent accidental rotation.
Critical Load Connections
- Attach the positive output to a schottky diode (B540C or lower Vf equivalent) to block reverse current that can destroy the battery during discharge.
- Solder the diode’s cathode to a 47 µF low-ESR capacitor to smooth the output; place this within 1 cm of the intended load.
- Add an LED with a 220 Ω resistor on the output side for visual confirmation–blinking under load indicates ripple exceeding 100 mV.
- Use a thermal pad under the regulator IC if ambient temperatures exceed 50 °C; most ICs throttle at 65 °C.
Test under real-world conditions: draw 500 mA from a dummy load for 30 minutes, monitoring temperature rise with a K-type thermocouple. Expect less than 30 °C increase above ambient; exceeding 40 °C suggests inadequate heatsinking or poor PCB thermal vias. If noise affects sensitive components, relocate the regulator board farther from RF traces or add a ferrite bead in series with the output path.
Calculating Inductor and Capacitor Values for Reliable Voltage Boosting
Select an inductor with a saturation current rating at least 20% above the expected peak switch current. For a 0.5A load, a 10μH inductor with a 0.8A rating works, while a 1A load demands 22μH or higher with 1.5A capability. Ferrite cores handle ripple better than powdered iron at frequencies above 200kHz but require attention to saturation margins. Measure the inductance drop at full load; a 10% decrease indicates borderline saturation.
Input capacitance should target 1% voltage ripple or lower. A 47μF ceramic capacitor with X7R dielectric suffices for 0.5A loads, while 1A loads benefit from 100μF or dual 47μF capacitors in parallel. Avoid electrolytic types unless low temperature is guaranteed–equivalent series resistance (ESR) rises sharply below -10°C, destabilizing regulation. Film capacitors excel at high frequencies but occupy more space.
Switching Frequency and Component Trade-offs
Higher switching frequencies reduce inductor size but increase losses. At 500kHz, a 4.7μH inductor fits into 3x3mm, but core losses may exceed copper losses, requiring derating. At 1MHz, use a 2.2μH with lower DC resistance (DCR) to maintain efficiency above 85%. Test thermals: if the inductor exceeds 60°C under load, increase core volume or reduce frequency.
Output capacitance balances transient response and ripple. For 1% ripple on a 5V rail, 22μF per ampere is conservative. Polymer tantalums offer low ESR but degrade rapidly under reverse voltage; ceramic types (X5R/X7R) handle transients better if derated to 50% of their voltage rating. Place capacitors within 5mm of the switching node to minimize parasitic inductance.
Peak-to-peak ripple current in the inductor approximates Iripple = (Vin × D) / (L × fsw), where D is duty cycle and fsw is switching frequency. A 3.7V input to 5V output with 300kHz switching and 47μH yields ~190mA ripple–within safe limits for a 1A inductor. If ripple exceeds 30% of load current, increase inductance or frequency to avoid discontinuous conduction mode.
Parasitic Effects and Margins
PCB trace resistance adds to DCR; a 10mm 0.25mm trace contributes ~2.5mΩ, reducing efficiency by ~1%. Use at least 4oz copper for high-current paths. Diode recovery time impacts efficiency: a Schottky with 30ns recovery dissipates less than a 100ns ultrafast diode, saving ~2% at 500kHz. If ringing exceeds 20% of input voltage, add a snubber (e.g., 1nF + 10Ω) across the switch.
Temperature derating rules apply: ceramic capacitors lose 20% capacitance at -40°C, while inductors see a 15% permeability drop. Test prototypes at extreme temperatures to verify stability. For battery-powered designs, prioritize low quiescent current–choose controllers with q to extend runtime.
For dynamic loads, oversize output capacitance by 40% to prevent voltage sag. A 1A load stepping from 0.1A to 1A in 1μs requires ~47μF to hold droop under 50mV. Use a load transient test to verify–if recovery time exceeds 20μs, add more capacitance or reduce ESR. Always confirm calculations with an oscilloscope in the intended application.