| Classification | Type | Characteristics | Typical Applications |
|---|---|---|---|
| Voltage Level | 5V TTL PWM | • Compatible with digital logic levels • Weak drive capability (<20mA) |
Direct MCU GPIO output |
| 12/24V Industrial PWM | • Strong noise immunity • Can drive relays/solenoids |
PLC control, industrial motor speed regulation | |
| Signal Form | Unipolar PWM | • 0V~Vcc square wave • Simple circuitry |
LED dimming, DC motor control |
| Bipolar PWM | • -Vcc~+Vcc square wave • Requires H-bridge circuit |
AC motors, servo drives | |
| Isolation | Non-isolated PWM | • Direct drive • Common ground system |
Board-level circuit control |
| Opto-isolated PWM | • Electrical isolation between input/output • Reduced response speed |
High-voltage equipment control (e.g., inverters) | |
| Magnetic-isolated PWM | • Excellent high-frequency characteristics (MHz level) • Higher cost |
New energy inverters |
Brushed DC Motors:
Speed control via duty cycle adjustment (e.g., car window motors, 30%~70% linear speed regulation)
PWM frequency: 1-20kHz (above human hearing range)
Stepper Motors:
Microstepping control using PWM (e.g., 3D printers with 256 microsteps require 8-bit PWM resolution)
DC-DC Conversion:
Buck/Boost circuits regulate output voltage via PWM (e.g., smartphone fast-charging ICs at 300kHz~2MHz)
Efficiency formula: η = (Vout × Iout) / (Vin × Iin_avg)
Battery Charging:
Both constant-current and constant-voltage phases use PWM control (e.g., Li-ion charger IC TP4056)
LED Dimming:
• Low-frequency PWM (100Hz-1kHz) avoids flicker
• High-end solutions use hybrid dimming (PWM + analog)
// Arduino example analogWrite(LED_PIN, 128); // 50% duty cycle
IR Remote Control:
38kHz carrier wave PWM encoding (e.g., NEC protocol)
Data format: Leader code (9ms high + 4.5ms low) + 16-bit data (PWM encoded)
Class D Audio:
Digital-to-analog conversion via 500kHz~1MHz PWM (e.g., TAS5624 amplifier IC)
| Parameter | Typical Range | Impact |
|---|---|---|
| Frequency | 1Hz-1MHz | • Low freq: Motors/lighting (avoid noise) • High freq: Power conversion (reduce inductor size) |
| Duty Cycle | 0%-100% | • 0%: Fully off • 100%: Full power output |
| Resolution | 8bit-16bit | • 8bit (256 levels): Basic control • 16bit (65,536 levels): Precision instruments |
| Rise Time | 10ns-1μs | Too fast causes EMI; too slow increases switching loss |
| Load Type | Recommended Solution | Schematic Example |
|---|---|---|
| Low current (<100mA) | Transistor (e.g., 2N3904) | PWM→[10kΩ]→BJT→Load→GND |
| High current (>1A) | MOSFET (e.g., IRF540N) | PWM→[Gate driver]→MOSFET→Load→GND |
| Isolated control | Opto+MOSFET (e.g., PC817+IRF540N) | PWM→Opto→[Driver]→MOSFET |
RC Low-Pass Filter:
Converts PWM to analog voltage (e.g., 10kΩ+1μF, cutoff frequency 16Hz)
Cutoff frequency: fc = 1/(2πRC)
LC Filter:
For high-current applications (e.g., motor drives, 100μH+100μF)
Electric Vehicles:
IGBT modules use 20kHz PWM for motor control (Tesla Model 3)
Industrial Robots:
Servo drives accept 400Hz PWM position commands (FANUC systems)
Home Appliances:
Inverter AC compressor drives (15kHz PWM)
| Issue | Cause | Solution |
|---|---|---|
| MCU reset due to PWM | Power fluctuation from high current | Add 100μF electrolytic + 0.1μF ceramic decoupling capacitors |
| Motor whine | PWM frequency within audible range | Increase frequency to >18kHz |
| Excessive heat | High switching loss | Use low Rds(on) MOSFETs or reduce frequency |
Higher Frequencies:
GaN devices enable PWM frequencies >10MHz (e.g., USB PD3.1 fast charging)
Digitalization:
Digital PWM (DPWM) replacing analog modulation (e.g., TI C2000 series)
Integration:
SmartMOS combines drivers with PWM generation (e.g., Infineon IPD70P04P4)
Pro Tip: When designing PWM systems, prioritize load characteristics (inductive/capacitive/resistive) before selecting frequency and drive solutions to avoid 90% of common issues.
