| Problem | Likely Cause | Solution | | :--- | :--- | :--- | | | Insufficient dead time | Increase PWM1CON value. | | Output waveform has flat top | DC bus voltage drooping | Increase bulk capacitance on DC link (e.g., 470uF/450V). | | Audible noise in transformer | Frequency drifting | Ensure crystal oscillator is accurate. Use stable timer interrupts. | | PIC resets under heavy load | Brown-out or EMI | Add decoupling caps (100nF + 10uF) directly across PIC Vdd/Vss. | | No output on RC4/RC5 | Configuration bits wrong | Verify CCP1CON is set to Half-Bridge mode ( 0x8E ). |
High-speed drivers like the IR2110 or IR2110S are used to isolate the microcontroller and provide the high gate voltage needed to switch power MOSFETs.
// Adjust duty cycle based on feedback (Simple PI loop placeholder) unsigned int duty = sineTable[index]; if (feedback < 512) duty = duty + 10; // Increase duty if voltage low if (duty > 121) duty = 121; // Max limit pic16f716 inverter circuit
Timer1 often handles the base 50Hz/60Hz frequency, while Timer2 manages the high-frequency PWM switching (typically 10kHz–20kHz) to keep the transformer quiet and efficient.
| Component | Specification | |--------------------|----------------------------------| | Microcontroller | PIC16F716 | | MOSFETs | IRFZ44N / IRF3205 (4 pcs) | | Gate Drivers | IR2110 (2 pcs) | | Transformer | 12-0-12 to 230V, 500VA | | Inductor (filter) | 2mH, 10A | | Capacitor (filter) | 4.7µF / 400V (AC side) | | Voltage regulator | 7805 | | Diodes | 1N4148, 1N4007 | | Problem | Likely Cause | Solution |
CCP1CON = 0x8E; // Half-Bridge mode, PWM enabled, P1A active high, P1B active high PWM1CON = 0x15; // Dead time = (0x15 * Tosc * Prescale) ~ 1us
Among the myriad of microcontrollers available, the stands out as a hidden gem for inverter design. Why? Because it comes equipped with a dedicated CCP (Capture/Compare/PWM) module that supports Complementary PWM outputs with dead-time control —a feature typically found only in more expensive digital signal controllers. Use stable timer interrupts
// 4. Main Loop while(1) ADRESL;