dc motorh-bridgel298pwm
I am using L298 motor driver to drive motors (12v , 900mA),I am using PWM to control motor speed but the problem is
1.When I set PWM frequency to 100 Hz motor work with jerks no noise at all.
2.When I set PWM frequency to 500 Hz motor work with little jerks and little noise.
3.When I set PWM frequency to 1000 Hz motor work with noise and no jerks at all.
4.When I set PWM frequency to 20 kHz motor dosen't work at all.
what should I do?
Shoot-through current refers to the condition where both switches/MOSFETs on one side of the H-Bridge are on simultaneously. Under normal conditions, the H-bridge is under one of the following conditions:
If, however, both switches on one side are on simultaneously, a huge current can flow (Only 34mΩ per leg, remember?), which is usually destructive. I'm not sure why both switches would be on - Possibly an issue with gate capacitance and switching time?
The datasheet says that the PWM pin is:
Voltage controlled input pin with hysteresis, CMOS compatible. Gates of low side FETs are modulated by the PWM signal during their ON phase allowing speed control of the motor.
You might get better luck with higher voltages if you modulated the PWM such that it was centered on the ON-pulses:
Motor on: ---- ---- -- -- S-Left-Top__/------\________/------\________ S-Rght-Bot___/----\___________/--\__________ S-Rght-Top__________/------\________/------\ S-Left-Bot___________/----\___________/--\__
But you'll definitely want to look very carefully at Figures 4, 5, and 6 of that datasheet.
This answer isn't correct. f.e. L298 motor shiled has PWM and PLL too. look at L298 wiki. Main difference is that with PLL you controlling speed and direction at one pin from -255 to 255 and second pin HIGH/LOW sets only enable/disable motor (you must switch pins as wiki says). With PWM you controlling speed with one pin and direction with second pin.
For me PLL works better than PWM, where I had problems that one of motor starts later.
Best Answer
As long as your PWM frequency is in the audible range (50 - 15000 Hz), there will be some audible noise. It doesn't mean something is wrong or about to break, simply vibrations at those frequencies propagate through air and can be heard.
If you absolutely want to get rid of the noise, you'll need a frequency of 20 kHz or more. L298 has a maximum commutation frequency of 25 kHz, so you should be able to get it working at 20 kHz (at least at 40-60% duty cycle) if your PWM waveforms respect that limit. Perhaps if you display your PWM signals with an oscilloscope, you'll realize why it didn't work.