Speed adjust for L6207

[apoggiali]

Posted on March 19, 2012 at 10:50

Hi everybody

On my simple Cw, Ccw control, for low power brushed d.c. motors, realized around L6207, i need to adjust the motor's speed.

Is it a good idea to Pulse Width  modulate the enable input (EA) instead using it just at purpose?

I am little bit afraid to fall in beating problems with pwm current control.

I'm considering the possibilty to devolope a new project, any suggestion about a more suitable chip?

Thank a lot for helps

Alfredo

[Enrico Poli]

Posted on March 20, 2012 at 11:30

Hello Alfredo,

It is not clear to me what do you mean with ''eating problems''. Could you explain it?

In my opinion the current control of the L6207 should fit your needs. The constant TOFF control implemented by the device should be able to control the phase current until the motor BEMF is lower than the supply voltage. The PWM on the EN pin could be also used, but in this case the current ripple could be significant because disabling the output bridges a fast decay is performed.

Power dissipation should also be considered: during the time the L6207 is disabled, the phase current flows through the body diodes of the power bridges which are less ''efficient'' than MOS.

Anyway, if you are not interested in the PWM current control you could use L6205 or L6206 instead of L6207.

Regards

Enrico

[apoggiali]

Posted on March 21, 2012 at 08:42

[Enrico Poli]

Posted on March 21, 2012 at 15:41

Hi Alfredo,

Now the point is clearer. You are using the PWM current control to limit the motor current and you want to regulate the motor speed using the enable pin of the L6207 (some kind of PWM of the motor current). It is correct?

In this case I think this is not a good idea because the motor torque is very discontinuous (every time you disable the chip you imposes a strong deceleration).

You could set the VREF value using a PWM modulation, this way you can regulate the motor current and as a consequence the torque and speed.

Another option is to used the L6206 and sets the overcurrent threshold (PROGCL pins) to your maximum current and drive the DC motor using the classic voltage mode approach: a PWM on the INX pins sets the mean voltage applied to the DC motor and as a consequence you can control the speed.

Ciao

Enrico

P.S. Your English is not so poor, but if you want we can continue in Italian. I prefer to use English in order to allows all forum members to give her/his opinion.

[apoggiali]

Posted on March 21, 2012 at 17:33

[Enrico Poli]

Posted on March 22, 2012 at 13:20

At your disposal.

Ciao

Enrico