MPPT Boost Converter Firmware

Design and Control of Renewable Energy Technology

STM32F303K8T (Nucleo-32) | 100 kHz PWM | Perturb & Observe MPPT

---

Technical Badges

---

System Overview

This firmware implements a Maximum Power Point Tracking (MPPT) controller for a 10W photovoltaic panel using a DC-DC boost converter. It runs on the STM32F303K8T Nucleo-32 development board and controls an IRF510 MOSFET via a TC4429 isolated gate driver at 100 kHz.

Theoretical converter efficiency: 94.65% at rated MPP (10W, 15V in → 30V out, D=0.5).

---

Hardware Architecture

PV Panel (10W, 20V)
    │
    ├── [40kΩ/10kΩ divider] ──[MCP602 buffer]──[RC LPF 390Ω/10nF]──[4.7V Zener]──► PA0 (V_SENSE)
    │
    └── [1Ω shunt] ──────────[MCP602 buffer]──[RC LPF 390Ω/10nF]──[4.7V Zener]──► PA1 (I_SENSE)

STM32F303K8T (Nucleo-32 @ 64 MHz)
    │
    └── PB0 (TIM3_CH3 PWM 100kHz) ──[56Ω R_Gate]──► TC4429 Gate Driver (12V)
                                                              │
                                                         IRF510 MOSFET
                                                              │
                                                    Boost Converter Circuit
                                                    L: 3C90 Ferrite Toroid
                                                    D: 1N4002
                                                    C: 2× output caps (parallel)
                                                    R_Load: 100Ω / 5W

Signal	Pin	Function
V_SENSE	PA0	ADC1_CH1 — panel voltage via 5:1 divider
I_SENSE	PA1	ADC1_CH2 — panel current via 1Ω shunt
PWM_OUT	PB0	TIM3_CH3 — 100 kHz gate drive signal
LED	PB3	Onboard LD3 — MPPT status indicator
UART TX	PA2	USART2 — telemetry at 115200 baud

---

Repository Structure

arm-mppt-boost-converter/
├── firmware/
│   ├── main.c              ← Core P&O control loop + state machine
│   ├── adc.c / adc.h       ← ADC1 register config + 8× oversampling
│   ├── pwm.c / pwm.h       ← TIM3 CH3 100 kHz PWM peripheral setup
│   ├── leds.c / leds.h     ← PB3 LED indicator driver
│   ├── usart.c / usart.h   ← USART2 telemetry (115200 baud)
│   ├── systick_delay.c/h   ← 1 ms SysTick delay
│   ├── PLL_Config.c/h      ← HSI × 16 = 64 MHz PLL setup
│   ├── PWR.h               ← Sleep mode macros
│   ├── main.h              ← System constants (Fcy, priorities)
│   └── device/
│       ├── startup_stm32f303x8.s   ← ARM reset handler + vector table
│       ├── system_stm32f3xx.c      ← CMSIS system init
│       └── STM32F303K8Tx_FLASH.ld  ← Linker script (64KB Flash, 12KB RAM)
├── Makefile                ← arm-none-eabi-gcc build system
├── MPPT_Report.pdf
└── README.md

---

P&O Algorithm

The Perturb & Observe algorithm adjusts the boost converter duty cycle by ±0.5% every 100 ms and observes the resulting change in output power:

Measure V(k), I(k)
P(k) = V(k) × I(k)
ΔP   = P(k) − P(k−1)
ΔV   = V(k) − V(k−1)

if |ΔP| > 5 mW:           ← outside dead-zone: still tracking
    if ΔP > 0:
        duty += (ΔV ≥ 0) ? −0.5% : +0.5%   ← continue same direction
    else:
        duty += (ΔV ≥ 0) ? +0.5% : −0.5%   ← reverse direction
else:                      ← inside dead-zone: MPP locked, hold duty
    (no change)

duty = clamp(duty, 10%, 90%)
output_pwm(duty)

Key parameters:

Parameter	Value	Rationale
Perturbation step	0.5%	Fine enough to find MPP, fast enough to track
Dead-zone	5 mW	Stops oscillation once settled at MPP
Loop period	100 ms	Allows output capacitors to fully settle
Duty limits	10–90%	Prevents inductor saturation at low duty; OV at high duty
ADC oversampling	×8	Reduces noise by ~2.8×; effective resolution ≈13.5 bits

---

Power Loss Budget (at 10W MPP, D=0.5, 100 kHz)

Component	Loss (W)	% of Input	Source
1N4002 diode conduction	0.335	3.35%	Vf = 1.0V
IRF510 MOSFET switching	0.029	0.29%	tr=16ns, tf=9.4ns
IRF510 MOSFET conduction	0.121	1.21%	R_DS(on)=0.54Ω
3C90 core losses	0.050	0.50%	Datasheet @ 100kHz
Total	0.535	5.35%
Efficiency η	—	94.65%

Improvement opportunity: replacing the 1N4002 with a Schottky diode (e.g. 1N5819, Vf≈0.3V) would reduce diode conduction loss by ~70%, pushing efficiency above 97%.

---

Build Instructions

Option 1: STM32CubeIDE (recommended)

1. Install STM32CubeIDE
2. File → Import → General → Existing Projects into Workspace
3. Select this folder — CubeIDE will recognise the Makefile project
4. Right-click project → Properties → MCU/MPU GCC Compiler → verify STM32F303K8Tx
5. Project → Build then Run → Debug (flash via ST-Link on Nucleo USB connector)

Option 2: Keil MDK

Open keil_project/STM_code.uvprojx — the original Keil project is included unchanged.

Option 3: arm-none-eabi-gcc (CLI)

# Install toolchain (Ubuntu/Debian/WSL)
sudo apt install gcc-arm-none-eabi binutils-arm-none-eabi

# Get STM32F3 CMSIS device headers (required, Apache 2.0 licence)
git clone https://github.com/STMicroelectronics/cmsis-device-f3 ../cmsis-device-f3
git clone https://github.com/ARM-software/CMSIS_5 ../cmsis_core

# Build
make CMSIS_CORE_INC=../cmsis_core/CMSIS/Core/Include \
     CMSIS_DEVICE_INC=../cmsis-device-f3/Include

# Flash with OpenOCD + ST-Link
make flash

---

Telemetry Output

Connect a serial terminal (PuTTY, screen, minicom) to the Nucleo virtual COM port:

• Baud rate: 115200
• Format: 8N1

Output format (tab-separated):

V=15.23   I=0.657   P=10.006   D=50.5
V=15.20   I=0.659   P=10.027   D=50.0
V=15.21   I=0.659   P=10.033   D=50.0   ← MPP locked (ΔP < 5mW dead-zone)

LED status (PB3, onboard LD3):

• Steady ON: MPP locked
• Slow blink (100ms): actively tracking
• Fast blink (50ms): duty cycle limit reached — check circuit

---

Algorithm Comparison (Chapter 4 summary)

	P&O (implemented)	INC	FOCV
Complexity	Low	High	Very Low
Steady-state oscillation	Yes, ±0.5%	No	No
Fast irradiance tracking	Can fail	Correct	Slow
Sensor requirements	V + I	V + I	V only
Recommended for	Stable conditions	Cloudy/variable	Cost-sensitive

---

*W.L.P.T.N. Wijayasinghe