IR2101 BLDC Controller

[bodmin636]

Hi

I have designed an electric trolley that is powered by a 24v bldc motor with hall sensors. I am using a 16khz pwm to make the trolley silent running. It also has a brake function where if the trolley is going faster than the desired speed it ramps down the pwm until it reaches 0, it then applies pwm braking by shorting the phases to ground if the trolley is still going to fast. Motor can draw up to 16Amps and is current limited by the software.

Everything works well and as expected. BUT every now and again it will blow a pair of fets short circuit. I cannot reproduce this on my test bed but this happens on a few of the trolleys I have made and are being used. I have not been able to ascertain from the feedback from the users what they were doing when the trolleys fail.

Anybody have any ideas?

Fets are IRFB4110 and the schottky diodes are B160.

 

[KlausST]

Hi,

I can´t see current limitation.
A pure software solution won´t be possible.

The problem I see is when you ramp down / break. Did you measure the currents to verify if the software current limitation works?

Klaus

 

[bodmin636]

Hi,

I can´t see current limitation.
A pure software solution won´t be possible.

The problem I see is when you ramp down / break. Did you measure the currents to verify if the software current limitation works?

Klaus

Hi, The current limit is achieved by a ZXCT1109 which is monitored by the processor. I have confirmed this works.

 

[KlausST]

Hi,

I still can´t find ZXCT circuit...

Is it high side or low side.
Is it a common current measurement, or individual for each phase?....

Klaus

 

[bodmin636]

Hi,

I still can´t find ZXCT circuit...

Is it high side or low side.
Is it a common current measurement, or individual for each phase?....

Klaus

Sorry it is off the left of the diagram. It is a high side current measurement and is common for the whole circuit. In software it allows it to run for 30 secs at 12 amps or 2 secs at 16 amps before shutting down. As said this is all tested and works fine.

 

[KlausST]

Hi,

So it can't limit current during breaking. Am i correct?

Klaus

 

[bodmin636]

I guess so yes, I do not implement the current limit when braking. I made a mistake in my original post, I pwm the high side fet on all phases to brake not the low side.

So I suppose it could be drawing too much current when braking and as the current sense is not in each fet it cant be detected. correct?

 

[KlausST]

Hi,

So I suppose it could be drawing too much current when braking and as the current sense is not in each fet it cant be detected. correct?

I guess so.

Klaus

 

[FvM]

I don't understand your breaking action. I would expect recuperation into the battery, in this case the phase current can be a least estimated from the DC+ current measurement.

Another point is that the IR2110 bootstrap supply can't be maintained without continuous low side pwm.

 

[bodmin636]

I don't understand your breaking action. I would expect recuperation into the battery, in this case the phase current can be a least estimated from the DC+ current measurement.

Another point is that the IR2110 bootstrap supply can't be maintained without continuous low side pwm.

The brake works by turning off the low side driver and applying a pwm to all 3 high side drivers. The pwm varies depending on the amount of braking required. The trolley is powered by a lithium LiFePO4 battery with internal bms so I am not sure how much the battery recuperates.

Not sure what you mean about the bootstrap supply. I am using an IR2101 not IR2110 if that makes a difference