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https://github.com/johassel/h_bridge_inverter
Hardware/Microcontroller project to build basic functions of an H-Bridge Inverter
https://github.com/johassel/h_bridge_inverter
inverter-control microcontroller micropython mosfet-driver power-electronics raspberry-pi-pico
Last synced: 7 days ago
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Hardware/Microcontroller project to build basic functions of an H-Bridge Inverter
- Host: GitHub
- URL: https://github.com/johassel/h_bridge_inverter
- Owner: JoHassel
- License: mit
- Created: 2024-12-24T12:50:53.000Z (16 days ago)
- Default Branch: main
- Last Pushed: 2025-01-01T20:26:46.000Z (8 days ago)
- Last Synced: 2025-01-01T20:29:17.271Z (8 days ago)
- Topics: inverter-control, microcontroller, micropython, mosfet-driver, power-electronics, raspberry-pi-pico
- Language: C
- Homepage:
- Size: 10.8 MB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# H-Bridge Inverter
## Goal
Basic functionality of an H-Bridge Inverter (12V DC --> 230V AC)
## Overview
1. Microcontroller (Raspi Pico) generates a sine PWM as a control signal
2. Sine PWM goes into a gate driver (Bootstrap)
3. Bootstrap (one for each side) controls H-Bridge MOSFETs --> sine_wave AC
Fig.1 - Simple H-Bridge
## Code
* based on [sPWM_Basic/sPWM_Basic.ino](https://github.com/Irev-Dev/Arduino-Atmel-sPWM/blob/d9c89ceef080a3c18ce5a02e0e310f1f46b8f579/sPWM_Basic/sPWM_Basic.ino)
### Flowchart
Fig.2 - Flowchart Code
### Output
Fig.3 - Sine PWM Output
## Hardware
### Why Bootstrap Circuit?
* source of high side MOSFET floats between V_AC (here: 12V AC) --> V_GS at the high side MOSFET must be high enough to safely switch on/off the MOSFET
* if low side MOSFET on, Bootstrap capacitor is chraged up to V_DC (here: 12V DC, voltage drop over bootstrap diode negligible)
* if high side MOSFET is switched on, the capacitor delivers its voltage to the control pin of the high side MOSFET
Fig.4 - Bootstrap CIrcuit
### Circuit Design
* [Infineon IR2104](https://www.infineon.com/cms/de/product/power/gate-driver-ics/ir2104/) was used
* Dimensioning based on [TI Application Note](https://www.ti.com/lit/an/slua887a/slua887a.pdf?ts=1735164351528&ref_url=https%253A%252F%252Fwww.google.com%252F)
* MOSFETs: [IRFB7537](https://www.infineon.com/dgdl/Infineon-Data_Sheet_IRFS7537PBF-DS-v01_01-EN.pdf?fileId=5546d462533600a4015364c3ee2729cb)
#### Bootstrap Capacitor
$C_{boot} >= \frac{Q_{total}}{\Delta V_{HB}} = 183.75nF$ (Rule of thumb: 10 times gate capacitance leads to $190nF$) --> $C_{boot} = 200 nF$
$Q_{total} = Q_G + I_{HBS} \cdot \frac{D_{max}}{f_{sw}} + \frac{I_{HB}}{f_{sw}} $
* $Q_G = 210nC$ from [Data Sheet MOSFET](https://www.infineon.com/dgdl/Infineon-Data_Sheet_IRFS7537PBF-DS-v01_01-EN.pdf?fileId=5546d462533600a4015364c3ee2729cb)
* $I_{HBS} = 50 \mu A$ from [Data Sheet Gate Driver](https://www.infineon.com/cms/de/product/power/gate-driver-ics/ir2104/)
* $D_{max} = 1$ (will be slightly lower beacause of 520ns Dead time, 100% assumed for conservative caluclation)
* $f_{sw} = 10kHz$
* $I_ {HB} = 55 \mu A$ from [Data Sheet Gate Driver](https://www.infineon.com/cms/de/product/power/gate-driver-ics/ir2104/)
$\Delta V_{HB} = V_ {DD} − V_ {DH} − V_ {HBL} = 1.2V $
* $V_ {DD} = V_{DC} = 12V$
* $V_ {DH} = 1V $ from [Data Sheet 1N4148](https://www.vishay.com/docs/81857/1n4148.pdf)
* $V_{HBL} = 9.8V$ from [Data Sheet Gate Driver](https://www.infineon.com/cms/de/product/power/gate-driver-ics/ir2104/)
##### Bootstrap Resistor
$R_{boot} = \frac{V_{DD} - V_{Boot,Diode}}{I_{peak}} = 5.5 \Omega$ --> $5.6 \Omega$
* $V_{DD} = V_{DC} = 12V$
* $V_{Boot,Diode} = V_ {DH} = 1V $ from [Data Sheet 1N4148](https://www.vishay.com/docs/81857/1n4148.pdf)
* I_{peak} = I_{FSM} = 2A from [Data Sheet 1N4148](https://www.vishay.com/docs/81857/1n4148.pdf)
#### Gate Resistors
$R_{G,HS} = \frac{V_{Gate}}{I_{o+}} = 92 \Omega$ --> $91 \Omega$
* $V_{Gate} = V_{DC} = 12V$
* $I_{o+} >= 130mA $ from [Data Sheet Gate Driver](https://www.infineon.com/cms/de/product/power/gate-driver-ics/ir2104/)
$R_{G,LS} = \frac{V_{Gate}}{I_{o-}} = 44 \Omega$ --> $47 \Omega$
* $V_{Gate} = V_{DC} = 12V$
* $I_{o+} >= 270mA $ from [Data Sheet Gate Driver](https://www.infineon.com/cms/de/product/power/gate-driver-ics/ir2104/)
### Output Filter
* second order passive lowpass filter (LC filter)
* Cutoff frequency $f_g = \frac{1}{2 \pi \cdot \sqrt{LC}}$ (see [ElectronicBase.net](https://electronicbase.net/de/tiefpass-berechnen/))
* Cap chosen based on availabilty in store: $C_{Filter} = 10 \mu F$ (use film cap, not a polarized one)
* $L_{Filter} = 100mH$ --> $f_g = 159.2Hz$
## Results
The higher the resolution of the sine PWM (pwm_periods & scaler, see code) the clearer the sine wave output gets. Since the performance of the C code is better than the Micropython code (see below), the sine wave from the C code has less ripples. The amplitude is relatively low at the moment since there is no output voltage regulation yet.
Fig.5 -Resulting Sine Wave with Micropython Code
Fig.6 -Resulting Sine Wave with C Code
## Performance
Disclaimer: I know Micropython is not made for high performance applications, but rather for rapid prototyping and easy debugging. I still wanted to see how far I can get with Micropython and compare it to C.
Also the C code can become much faster by shorten the timer callback, using bit operations and more.
I am looking forward to any improvement suggestions :)
| Language | Code Version | $f_{sin,set}$ in Hz | $f_{sin,real}$ in Hz | $f_{switch,real}$ in kHz |
| ----------- | ----------- | ----------- | ----------- | ----------- |
| MicroPython | 26/12/2024 | 50 | 50 | 5 |
| MicroPython | 26/12/2024 | 100 | 100 | 10 |
| MicroPython | 26/12/2024 | 500 | 105.3 | 10.5 |
| C | 02/01/2025 | 50 | 50 | 5 |
| C | 02/01/2025 | 100 | 100 | 10 |
| C | 02/01/2025 | 500 | 444.4 | 44.4 |
## ToDos
* shorten timer callback
* add output voltage regulation
* (if inductive load: add external flyback diodes in parallel to MOSFETs)