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Topic: High Powered Motor Design (Read 138 times) previous topic - next topic

laveur

Hey everyone,

I have this following design for controlling a 12V 4A motor (well really a fan but same thing):



The code is fairly simple, it starts off with the fan shut off. You press the button it comes on low, press again medium, press again its high. After that it shuts off again.

It started off working fine but lately when you turn it on it kills the high side driver of the IR2184 Driver IC.

I have a feeling it has to do with high in rush current. But I am not 100% sure it is.

Any thoughts on whats going on please let me know.

jackrae

Have you confirmed the possibility that Q2 isn't turning ON at the same time as Q1
Your code would be helpful in diagnosis

MorganS

That's a pretty fancy driver. I don't expect that it would ever turn on Q1 and Q2 at the same time.

However driving a fan in one direction only Q2 isn't doing anything. Except it's required by the bootstrap power supply for the VB pin. This is one of those devices that can't operate at 100% duty cycle as it needs PWM operation to pump up the capacitor on VB. The datasheet doesn't list a maximum or minimum duty cycle but I don't see how it generates that voltage inside the chip without oscillating.

For just driving a fan on and off and PWM control, there's much better chips that have everything integrated. Something like a BTS716G will drive up to 6 amps per channel and it detects short-circuits and other faults too. It's only available as a SMD part but it's big enough to solder by hand and you can buy one of my breakouts from OSH Park. (I get nothing from OSH Park if you use my design. You only pay for the PCB.)

There's no other components required: no diodes or capacitors, no pullups or anything. Plug it in backwards and it will just sit there waiting for you to correct your mistake, although it cannot prevent the reverse-battery flowing through to the load, so your fan may run backwards or explode if you try the experiment.
"The problem is in the code you didn't post."

Wawa

Not sure why you use a push/pull driver for your swamp-cooler fan.
That circuit could brake (slow down) the fan during the "off" parts of the PWM pulse.
Maybe ok for a motor, but not for a fan.

A single logic level mosfet should be able to PWM that 4Amp load low-side.
First diagram here.
Note that the IRF3205 is NOT logic level.
Leo..

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