www.dasWindrad.de

Greetings, I have started a buck converter project for a small wind turbine. So far I have a 555 timer at 10 kHz driving a IR2117 gate driver to turn a n channel MosFet on and off. The main problem I am having is the IR2117 is turning on during the off cycle of 555 timer. Is there a solution to this problem? Any help will be greatly appreciated.



I am using a bench power supply for Vcc of IC’s until I solve this problem.
This is a first attempt.

Hi,

I found a reference to the problem on page 8 and 9.

http://www.nalanda.nitc.ac.in/industry/ ... /An978.pdf

It recommends increasing the boot strap capacitor to a valve greater 0.47 uf. I will post results when available.

Have you checked the the PWM input of the IR2117. It can happen, that a DC-DC converter (especially inductor converters) distort the operation of other components. How did you set it up? On breadboard or wired or PCB? It doesn't look like a bootstrap problem in the video, because the line after the jitter is longer and looks solid.

Hi, this is a first attempt. Photos show prototype board configuration. The wave form shows input and output of the IR2117 with no mosfet connected. When I connect the mosfet to the circuit I am manually spinning the PMA and the video shows that the mosfet is turning on during the off cycle of the IR2117 and tracks or the position changes as the RPM of the PMA increases and decreases. I have no experience with this type of circuit and any help will be greatly appreciated.








top wave is Voltage at load, bottom is voltage at mosfet gate.



input and output of IR2117 with light as load.

Hallo,

so eine Schaltung läuft besser mit einem P-Kanal-Fet und ohne Treiber-Chip. Der 555 kann dann das Gate direkt ansteuern.

MfG. Andreas

Grüße, ich danke Ihnen für Informationen über den P-Kanal MOSFET. Es ist gut, eine andere Option zu haben. Danke

I don't like high side drivers, as Andreas said p-channels are easier to handle and with new more efficient models high side drivers are getting pretty much obsolete.

With your design you'll propably get some problems with the charge pump, because the VS-Pin of the driver doesn't get down to ground when switching. The frequency (10kHz) is very low for a high side driver, and that's why you'll need a very big bootstrap cap, expecially when the difference between Vcc and Vsource is realy big.

You can try this: don't power the ir2117 from external power. Connect VCC, bypass cap and the diode directly to the drain of the mosfet. This will give the bootstrap cap a good initial charge, and the charging pump only needs to provide 8V or more.

May be, take a look at this:
viewtopic.php?f=19&t=895&start=100#p13294

Greetings, I added the larger caps to the boot strap and the ringing is still there but only noticeable at lower RPM’s.

I am still using the 555 timer. I increased the duty cycle to 80% and inverted the output so the duty cycle at the input of the IR2117 is 20% high. I connect a 12 volt 50 watt light and spinning the PMA manually I was able to illuminate the 50 watt light with relative ease. Wow, a shorter duty cycle made all the different. The PMA was much easier to spin and even maintained momentum for a short period when I stopped spinning the PMA.

Without the buck converter I was unable to illuminate the 50 watt load under manual operation.

I am still using the bench power supply to power the IC’s.

Performance has definitely improved.

I still need away to control the duty cycle at different PMA RPM’s and find away to power the IC’s from the battery or PMA. Next step is to try charging the battery. It maybe time to start thinking about adding a micro controller. Thank you for all the suggestions.



http://youtu.be/B3dLzZZ5jKQ

photo of PMA

Hallo, tauschte ich das mit einem IRF510 IRF540 und ich bin nicht in der Lage zu replizieren die Ergebnisse im letzten Video gezeigt. Es ist eine verwirrende Situation. Es kann eine andere Bootstrap-Kondensator oder eine andere Lösung. Ich kann nicht fortgesetzt, bis eine Lösung gefunden wird. Die Schaltung wird mit einer geringeren Belastung funktionieren, aber nicht mit 50-Watt-Last zu arbeiten. Das Oszilloskop zeigt die IRF540 beginnt sich zu drehen auf dann sehr schnell ausschaltet, dann die Gewinne Vin Ausmaß und die 555 Timing-Signal abschaltet. Kommentare willkommen.




Hi, I exchanged the IRF510 with a IRF540 and I am unable replicate the results shown in the last video. It is a puzzling situation. It may require a different bootstrap capacitor or some other solution. I am unable to continue until a solution is found. The circuit will function with a lower load but does not work with 50 watt load. The oscilloscope shows the IRF540 starts to turn on then very quickly turns off, then the Vin gains magnitude and the 555 timing signal shuts down. Comments welcome.