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Huge problem with l6203

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black-code

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l6203

hello all,..

I faced a very huge problem with l6203 in my project and i don't know any solution ,i hope someone can help me to overcome it.

I connected l6203 with atmega32 microcontroller to make a speed control for a dc motor with a two batteries 12 v connected in series to give 24 volt.

The microcontroller takes it's 5 v from a simple regulator 7805.


I used the above circuit for two motors with two h-bridges (l6203) and two microcontrollers each motor has it's microcontroller and h-bridge ( GND and VCC are common for all the circuit).

On connecting the power to the circuit the motors runs normally then suddenly one of the two bridges becomes very hot and then blowing out !!!!! :cry:

WHAT IS THE REASON PLEAAASE ??

I am very depressed for that because i don't want the reason for that.
I read l6203 datasheet, i found that there is a table saying that vref taking 13.5 volts typ. is this means that i must connect vref to 13.5 external voltage or what ??


Thanks.
 

Eugen_E

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l6203 schematic

You need to connect a decoupling capacitor near L6203, and also capacitors at pins 4, 8, according to the attached datasheet - Figure 17, page 12. I think because of the missing capacitors, the resulting spikes drive in conduction 2 near transistors at the same time blowing out the bridge.

Also check the maximum current required by the motor, and if the motor is blocked/ heavy loaded.
 

banjo

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l6203 circuit

I would agree with what Eugene has already posted. You need the bootstrap capacitors. I would suggest checking which MOSFET is shorted by using an ohmmeter with the power off and the motor disconnected. If the upper MOSFETS are the ones shorted, then it points toward the missing bootstrap capacitors. These capacitors are there to insure that the upper MOSFETs can be fully turned on. If the upper MOSFETs do not turn on really hard, then they have a significant on-resistance and the generate lots of heat.
If the lower MOSFETs are shorted, then I would suspect more of a spike condition due to decoupling capacitors.
If both upper and lower MOSFETs are shorted, it is possible that one side shorted and then destroyed the other side. At that point, it is not possible to really tell which section failed first.
 

black-code

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l6203 projects

Thanks for all Eugen_E and banjo.

But where i can put the decoupling capacitor, between vs of the h-bridge and gnd or where??
 

FvM

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h-bridge l6203

Just take a look at the datasheet. It clearly shows the bootstrap capacitors as well as decoupling betweeen Vs and Gnd.
 

black-code

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bridge l6203

FvM said:
Just take a look at the datasheet. It clearly shows the bootstrap capacitors as well as decoupling betweeen Vs and Gnd.

Thanks FVM but is the bootstrap decoupling capacitors all the problem ??

If i connect them the problem will be solved or there is another reason ??

Thanks.
 

FvM

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l6203 motor speed control

A missing decoupling capacitor must not be necessarily a problem, I don't want to say, it surely isn't. But the missing bootstrap capacitors are surely a serious issue as was already pointed out in the discussion. It effectively prevents operation of the upper bridge transistors as a switch and causes high losses that actually can damage the chip.
 

black-code

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l6203 circuit

Thanks fvm for help, i will add the bootstrap capacitors and see the results.

Thanks again.
 

Aminkh22

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My friend,
if you look at the datasheet as good, you find that you have to put two bootstrap capacitors (10nF or more) between boot1 , out1 and boot2 , out2.
for Vref you can put a capacitor (0.22uF) between ground and Vref. attention to capacitors voltages.
 

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