Malfunction of voltage regulation Dual VNH5019


I’m using the motor driver Dual VNH5019. When tested under different loads, I have found that the actual motor voltage differs from the setted voltage (you can see that in the attachment). The x-axis represents the setted, the y-axis represents the actual measured voltage.

The measurement series are from top to bottom:
DC motor without load
DC motor with load
resistor with 600 ohm
resistor with 10 ohm

My supply voltage is 24 V at a maximum current of 5 A.

According to your instructions I would have expected a load-independent voltage.

Does the Dual VNH5019 run within its specifications?
Is there a possibility to use a load-independent voltage regulation or to improve the behavior shown in the chart?

Many thanks in advance for your reply!

Konrad Henkel

Hello, Konrad.

Please note, adjusting the output of the motor driver does not directly change the voltage it delivers but the duty cycle of the PWM signal. Those curves seem to match what we would expect in drive-coast mode; during the off-portion of the PWM cycle, the inductance of the motor creates a back EMF that pushes against the current and maintains the voltage across the motors. Using the VNH5019 in drive-brake mode will probably give a more linear result.

- Jeremy