PWM
Overview
Pulse Width Modulation (PWM) blocks provide high-performance waveform generation for motor control, power conversion, and signal generation applications. The MPLAB Blockset offers PWM blocks optimized for different device families and application requirements, from edge-aligned PWM to high-resolution PWM with fine edge positioning.
Available PWM Blocks
PWM HS FEP - High-Resolution PWM with Fine Edge Positioning
PWM HighSpeed - High-Speed PWM for dsPIC33C/CH/CK
PWM - Standard PWM for dsPIC30F/33F/33E
MCPWM - Motor Control PWM for PIC32MK
PWM SAM7x - PWM for SAM ARM Microcontrollers
TCC PWM - Timer/Counter for Control (SAM)
PWM Override Blocks
Override blocks provide software control over PWM outputs:
PWM HighSpeed Override
Force PWM outputs to specific states independent of generator. Use with extreme caution - improper use can damage hardware.
PWM SAM7x Override
Override control for SAM7x PWM outputs. Essential for emergency shutdown and safety systems.
Block Selection Guide
By Device Family
| Device Family | Recommended PWM Block | Key Advantage |
|---|---|---|
| dsPIC33A (33AK) | PWM_HS_FEP | Highest resolution (250 ps), fine edge placement |
| dsPIC33C (CH/CK/CDV) | PWM_HighSpeed | Independent time bases, flexible modes |
| dsPIC33E (non-GS) | PWM | Standard complementary PWM |
| dsPIC33E GS | PWM_HighSpeed | Enhanced features with APLL |
| dsPIC33F / dsPIC30F | PWM | dsPIC30F/33F device support |
| PIC32MK | MCPWM | Digital comparator integration |
| SAM E70/S70/V70/V71 | PWM_SAM7x | Up to 8 channels, advanced features |
| SAM E5x/D5x/C2x | TCC_PWM | Pattern generation, compact |
By Application Requirements
| Application | Block Choice | Why? |
|---|---|---|
| Premium 3-Phase Motor | PWM_HS_FEP | Ultra-low THD, fine edge control |
| Standard 3-Phase Motor | PWM_HighSpeed | Independent channels, good performance |
| BLDC with Hall Sensors | TCC_PWM | Built-in pattern generator |
| High-Frequency SMPS | PWM_HS_FEP | Sub-nanosecond resolution |
| Interleaved Converters | PWM_HighSpeed | Independent time bases per channel |
| dsPIC30F/33F/33E Motor Drive | PWM | Wide device support |
| Fault-Tolerant System | MCPWM | Digital comparator, advanced fault handling |
PWM-ADC Synchronization
Critical for motor control and power conversion - ADC sampling must be synchronized with PWM to minimize switching noise and ensure accurate measurements.
How It Works:
PWM modules can generate trigger signals that automatically start ADC conversions at precise moments within the PWM period. This synchronization ensures current and voltage measurements occur when switching transients have settled, providing clean data for control algorithms.
Trigger Timing Strategies:
| Trigger Point | PWM Mode | Benefit | Typical Application |
|---|---|---|---|
| Valley (center of low period) | Center-aligned | Minimum switching noise | 3-phase motor control |
| Peak (center of high period) | Center-aligned | High-side current sensing | Buck converters |
| Start of period | Edge-aligned | Simple timing | Basic power supplies |
| Mid-period | Edge-aligned | Balanced measurement | General purpose |
Multiple Trigger Support:
Advanced PWM modules (dsPIC33A, dsPIC33C) can generate multiple independent trigger outputs, enabling:
- Simultaneous multi-phase sampling for 3-phase motor control
- Staggered ADC conversions to distribute processing load
- Auxiliary measurements (DC bus voltage, temperature) at different times
Configuration Principles:
- Choose trigger point based on switching waveform characteristics
- Verify trigger timing with oscilloscope before motor/power testing
- Use hardware triggers instead of software polling for deterministic timing
- Match ADC sample time to source impedance and noise settling requirements
Typical Applications:
- Motor FOC: Sample phase currents at valley (minimum noise) for current loop
- SMPS: Sample output voltage mid-period for voltage loop
- Multi-motor: Use independent triggers for each motor’s ADC channels
Device Family Support Summary
| PWM Block | dsPIC30F | dsPIC33F | dsPIC33E | dsPIC33C | dsPIC33A | PIC32MK | SAM E7x | SAM E5x | SAM C2x |
|---|---|---|---|---|---|---|---|---|---|
| PWM | ✅ | ✅ | ✅ (non-GS) | ❌ | ❌ | ❌ | ❌ | ❌ | ❌ |
| PWM_HighSpeed | ❌ | ⚠️ (selected) | ✅ GS | ✅ | ❌ | ❌ | ❌ | ❌ | ❌ |
| PWM_HS_FEP | ❌ | ❌ | ❌ | ❌ | ✅ | ❌ | ❌ | ❌ | ❌ |
| MCPWM | ❌ | ❌ | ❌ | ⚠️ (selected) | ✅ | ✅ | ❌ | ❌ | ❌ |
| PWM_SAM7x | ❌ | ❌ | ❌ | ❌ | ❌ | ❌ | ✅ | ❌ | ❌ |
| TCC_PWM | ❌ | ❌ | ❌ | ❌ | ❌ | ❌ | ❌ | ✅ | ✅ |
Legend: ✅ Full Support | ⚠️ Selected Devices | ❌ Not Available
See Also
Related Block Categories:
- ADC Blocks - For PWM-synchronized current/voltage sampling
- Timer Blocks - For precise timing and capture
- Encoders - For motor position feedback (QEI, PDEC)
Application Notes:
- AN1078 - Sensorless Field-Oriented Control of PMSM
- AN1292 - Sensorless Field-Oriented Control of Three-Phase PMSMs
- AN1160 - Sensorless Field-Oriented Control
Example Projects:
💡 Need Help Choosing?
- For dsPIC33A → PWM_HS_FEP
- For dsPIC33C designs → PWM_HighSpeed
- For dsPIC33F/33E → PWM
- For ARM-based designs → PWM_SAM7x or TCC_PWM
PWM SAM7x
Advanced PWM peripheral for SAM ARM Cortex-M microcontrollers. Provides complementary PWM with dead-time, fault protection, and pattern generation …
Read more →MCPWM
MCPWM (Motor Control PWM) offers enhanced features beyond standard PWM blocks, including programmable fault sources with digital comparator inputs, …
Read more →PWM
The PWM block supports up to 4 complementary PWM channel pairs with independent duty cycle control, dead-time insertion, fault protection, and …
Read more →PWM HighSpeed
This block is designed for demanding motor control and power conversion applications requiring precise timing, independent channel control, and high …
Read more →PWM HighSpeed Override
The override block works in conjunction with the MCHP_PWM_HighSpeed block and can force PWM outputs to specific logic levels regardless of the PWM …
Read more →PWM HS FEP
This advanced PWM peripheral is specifically designed for precision motor control, high-frequency power conversion, and applications demanding …
Read more →PWM SAM7x Override
Direct control of PWM output pins for SAM7x devices, allowing software override of PWM signals for safety shutdown, diagnostics, and custom patterns. …
Read more →TCC PWM
Timer/Counter for Control (TCC) PWM peripheral for SAM microcontrollers. Features advanced pattern generation, complementary outputs with dead-time, …
Read more →