Current flow controller for DC Motors

[mikebar]

Will the motor run in one direction or you need both directions? CW/CCW

If one direction, then I would use IRFZ44. PIC PWM pin directly goes to the gate with 15K to GND. Easy, reliable, affordable.

If you need both directions then I wish you luck


For the diode, what is your plan to use it? Where, why, idea etc.

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Thank for the suggestions.
Yes, I need just one direction: CW
I think to use the diode in order to protect the MosFET from the back EMF while switching on and off the motor because the PWM (like anode to the side where the motor is connected to the GND through the FET and catode to +24Vcc)
I saw from the datasheet of the mosfet you have suggested that the IRFZ44 has an internal avalanche diode. So my one outside is useless.
But I also saw in the datasheet that there is no mention about IRFZ44 to be a "logic level" mosfet. Since I never used it before, it is really enough to drive a PIC pin directly to the Gate and put in the middle of this path a 15K resistor to the GND?

Thank you in advance.

[sougata]

IRFZ44 has an internal avalanche diode. So my one outside is useless.

The MOSFET body diode is not a soft recovery type. While you can live without an external diode putting one may save trouble. Switch Off ringing + Brush Noise + Reverse Recovery Time may kill your MOSFET.

You can use SG3525 PWM controller that solves your whole purpose.

[mikebar]

The MOSFET body diode is not a soft recovery type. While you can live without an external diode putting one may save trouble. Switch Off ringing + Brush Noise + Reverse Recovery Time may kill your MOSFET.

You can use SG3525 PWM controller that solves your whole purpose.

Thank you Sougata.
That's why I've asked if somedy knows a good diode to protect a mosfet that is running a Brushed motor rated at 24V 5A, supposing an intermittent use and regulated with PWM wave.
I searched for the SG3525. I've found the datasheet but also the providers said that it is out of stock.
Have you used it to control DC motors? If yes, could you share some schematic here?

Thank you.

[sougata]

Hi,

I had a crashed HDD last year. (Now I use RAID cause I am too lazy too backup '// Actually my projects never gets finished )

I found the PCB layout but seemed to have lost the schematic. Since SG3525 has complementary outputs with dead time. You need to couple (OR) both the outputs and drive the MOS.

The current sense input works on a pulse by pulse limiting followed by a soft start for persistent overload.

[mikebar]

Hi,

I had a crashed HDD last year. (Now I use RAID cause I am too lazy too backup '// Actually my projects never gets finished )

I found the PCB layout but seemed to have lost the schematic. Since SG3525 has complementary outputs with dead time. You need to couple (OR) both the outputs and drive the MOS.

The current sense input works on a pulse by pulse limiting followed by a soft start for persistent overload.

Thank you Sougata.
I'm sorry to strees you. Could I ask even a Paint-made schematic of what do you mean?
Maybe you mean take the signal from output A and B and connect to the input of an OR gate?
Then from the output of the OR gate, drive a logic mosfet. Correct?

I've found this info:
http://home.att.net/~wzmicro/3525.html

Is that a good application, in your opinion?

[sougata]

Hi,

My design was almost the same. I used two MOSFETs (common drain / common source) though. Reason:

• Better Current Handling
• Quicker Turn-OFFs -- Because when you use diode OR-ing you loose the low going edge that turns off the MOSFETs fast

Also I used an active Op-Amp amplifier for the current signal.

The link you posted should work absolutely fine.

[mikebar]

Hi,

My design was almost the same. I used two MOSFETs (common drain / common source) though. Reason:

• Better Current Handling
• Quicker Turn-OFFs -- Because when you use diode OR-ing you loose the low going edge that turns off the MOSFETs fast

Also I used an active Op-Amp amplifier for the current signal.

The link you posted should work absolutely fine.

Ok, I'll try it first.
Just a last question:
If I want to use an OR gate instead of the two diodes like you said, supposing that I'm feeding the chip with 24Volts, what is the output voltage level from ports A and B of the SG3525? I suppose close to 24volt as "1". So, in this case, wich kind of OR gate I should use?