[SOLVED] l298 over heating problem

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amintlk

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hi to all
i made a driver with l298 and it work well , i parallel two channel ... my motor was 24v 300mA .. but recently i made another one just like last one ,but in new one my l298 get very hot .. the motors are same ... i have both of them now , in older one my l298 work without heating and in new one l298 get very hot and after a few second breakdown .. even if i use without load the l298 get very hot .. i've changed a lot of l298 ...
 

maybe u have shorted some connection in your new l298 driver while soldering ..
 

Thanks for your replay .. I use " older one's l298 " instead of " new one's l298 " , but it heated again .. so I don't think so .. I didn't use heatsink because the older one works well without heat sink ..

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Thanks for your replay
I check it a lot . And I clean up pcb .. there is no addition solder connection
 

did you change power source or motors when using the new l298?
 

Yeah post schematic, what do you mean breakdown? stopping the motor? is it heating much when motor is not running ?
 


Perhaps the layout differences caused the Bridge to oscillate. This can result in >4W peak per transition per driver 2V@2A. If using the max commutation speed of 40KHz, reduce that to 10KHz and show us both layouts and schematic with images.

if you measure with differential probes and a current shunt on the supply or 2 probes with very short ground leads across a 50mV shunt on V+ or 0.01Ohm for 5A peaks. Use low ESR caps only on V+.

If you don't have 0.01Ohm handy, use short thin wire and measure 0.01V voltage with 1A current limited lab supply to make one.
 



thanks all
i have linear power supply 0-30v 0-3A ... when i use this as power supply , l298 work correctly without heating , but when i use 220 to 24v trans , my l298 get very hot .. when i check pin4 (vs) with oscilloscop , there are big ripple , but i cant decrease ripplr , even i change capacitor from 1000uf to 3300uf , but the ripple doesn't decrease ... i disconnect motor from circuit , but doesn't change ..
 

Hmm....

Is your 'transformer' producing 24V RMS or is it a PSU producing regulated 24V DC?
I think your power source is responsible but it probably isn't the ripple that causes the problem, it is more likely to be excess voltage.

Brian.
 

check the direction of C1 cap.

After that verify D1, D2, D3 and D4. also the pins out 1,2,3 and 4.

The maximum voltage is 50V. either case it cant be the problem.
 

Working OK on 30V but not on 34V might have been a clue but on reflection I think there is a grounding issue. When running from a DC PSU it may not show but with two supplies from a single transformer secondary it might. One diode in each bridge rectifier is in parallel with one in the other bridge but one connects to 5V ground and the other to the L298 current sense resistor. I suspect the sense and grounds on the L298 are not wired correctly.

Brian.
 

There is also chances for wrongly wired PSU diodes. because both circuits sharing a single supply. What about the waveform in 5V pin?

Where will you exactly feed the DC input instead of AC?
 

May be the transformer can't able to supply sufficient current to the motor.

Check Vs there is any voltage drop while motor running.
 

I cannot read the part number of the "x4007" protection diodes at the motor. If they are 1N4007 mains rectifiers then they are much too slow at 40kHz.
Maybe a different batch of rectifiers was used for the circuit that fails.
 

Thanks all ..
Diode is ultra fast diode uf4007.. and my freq is 10k ..
My transformer is 2A and my motor is 300mA ..
I check 5v with oscop and it doesn't have ripple..
Problem it's not level of voltage , problem is ripple voltage in pin4 (vs pin )
When I test last one circuit with 24 transformer , l298 doesn't get hot but when I test new one circuit with this transformer, l298 get very hot
I'm not amateur but I feel so confuse

- - - Updated - - -

When I check RS 0.5 ohm resistor with oscilloscop my peak voltage is 1.5 volt .. it's too much
 

Post or describe scope current. does the peak resonate or just commutation spikes. What is PW50 or pulse width at 50% of current spikes? How does that compare with Voltage.

Does the Bridge see a capacitive load added ?

Something has changed in your design, unless there is a faulty connection or part.
 

Because you used TWO bridge rectifiers, the grounds in the circuit are all mixed up. Use only one bridge rectifier and connect all the grounds together like this:
 

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even if i use without load the l298 get very hot .. i've changed a lot of l298 ...
Click to expand...

new one l298 get very hot and after a few second breakdown
Click to expand...

even i change capacitor from 1000uf to 3300uf , but the ripple doesn't decrease ... i disconnect motor from circuit , but doesn't change
Click to expand...

This all denotes that there is a short circuit.!!!

the problem is there when there is no motor, so we can take it off from circuit.

now May be it can happen through didodes in output pin or through wrong connection of outputpins

If there is some wrong connection in output pins the motor will not work so that is not possible.

can you please measure the waveform in top rectifier output without connecting to pin 4 ?

Connecting the ground wires itself could solve the problem between rectifiers. the circuit in #19 shd work for you, if it is not then if you use two tranformer for rectifires and if you connect the ground wires surely it will work.
 

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