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I am controlling a brushless AC motor using 3 indépendant half-bridges of two L298N and my issue with this is that the sine voltages it is generating are inaccurate compared to the commands sent. The biggest contributor is a high voltage drop.
I thought of adjusting the motor supply voltage but since I am going to upscale this to 3 actuators there would be many settings and there is still some un-calibratable error anyway.
I would like to achieve 1% accuracy on 0-12V winding voltages. The sine waves are 16Hz, 6 bits quantisation, 11kHz PWM, and draw 500mA max (in-rush), with 9mH inductance.
- 1Virtually any you can find will be better than the L298. – Andy aka 17 hours ago
- I bet, but are there any which would do what I want and better without closed loop on the voltage? – Mister Mystère 17 hours ago
- For low voltage you want something FET based not Darlington based. Shopping questions aren’t on topic, the key information you need is to look for something with FET’s. But you may also have to model the commutation process… Incidentally youay be able to re-flash an R/C hobby “ESC” – Chris Stratton 17 hours ago
- As you said, the biggest trouble maker is the voltage drop. I am playing with BTN7971 MOSFET H-bridge, which has very very low on resistance. Perhaps I can summary something as an answer. Reference: (1) “L298 and BTN7971B”:electronics.stackexchange.com/questions/510755/…. Cheers. – tlfong01 15 hours ago
- (1) I checked that L298 total path drop for 2A, is around 4V. So R = V / I = 4 / 2 = 2Ω. For BTN7071B, the on resistance is only of the order of 30mΩ. (2) For L298, the voltage drop has a big range of about 2V to 5V, so you need to perhaps get 100 samples and grade/group them yourself. (3) “BTN7971B High Current PN Half Bridge NovalithIC – Infineon 2008 June”: mouser.com/datasheet/2/196/… Good luck. Cheers. – tlfong01 15 hours ago
- This is a summary of the L298 EE characteristics: imgur.com/5Zw4XaZ. Cheers. – tlfong01 15 hours ago
- 1Thanks but the BTN7971B sounds like overkill here. I have come across the DRV8874 which has 120mOhm max Rdson (unidirectional currents), which yields 0.5% error across all voltages. Am I missing anything else? – Mister Mystère 13 hours ago
- DRV8874 with 1200mΩ looks good. This is a discussion on DRV8874: electronics.stackexchange.com/questions/108686/…. – tlfong01 2 hours ago
- The other MOS H-bridge you might consider is TB6612, with 500mΩ on resistance. (3) AliExpress TB6612FNG H-Bridge DC Mother Driver (0.5Ohm on resistance) – US5 aliexpress.ru/item/32466224012.html (4) TB6612FNG Datasheet – Toshiba sparkfun.com/datasheets/Robotics/TB6612FNG.pdf. Cheers. – tlfong01 2 hours ago