problem with the power supply! Help!!

[stoyanoff]

I have a problem. I created a full-bridge with 4 IGBT transistors. So as you know when they work thier temperature raise. So I added aluminium coolers to every. Before that everything worked fine. But when I`ve added the coolers the problems with the power supply for the microcotroller start(+5V). I added a delay (5s) before the start of the program. So when the controller starts to open the IGBTs the +5V dorps down and restarts the PIC. I have 2 capacitators on the GND and Vcc pins of the controller(100nF non-electrolite and 100uF electrolite). I have voltage regulator(7805). 22uF cap befor the regulator and 1000uF after the 7805(both electrolite).
What can I do to stabelise the power supply??? Is the problem in the aluminium coolers???

 

[Orson Cart]

you have made an aerial with your heatsinks - the RFI is now getting in to your control...

you need to isolate the devices from the heatsinks (with suitable heat transfer insulator e.g. Denka BFG45) and then connect the heatsinks to a static point to stop capacitive coupling making them aerials again.

so for the low side devices connect the heatsinks to source/emitter, and for the high side devices connect the h-sinks to the collector/drain.

this should stop most of the RFI getting into your control.

 

[mpathma]

Hi,

Can you post your diagram. Hard to suggest.

M.Pathma

 

[stoyanoff]

The problem is not in the program! I`ve replaced almost all of the parts in the power supply. I`ve added 1 more capacitator (1000uF). But now in the first start the device works for around a minute. After that it resets and after this reset everything is OK. I suppose I need bigger caps in the power supply. I will try with 4700uF.
If you aks me these 2x1000uF should be anough. Any other suggestions??

 

[mtwieg]

You shouldn't need more than a few uF for the microcontroller. If it requires more, then something isn't working right.

Are the heatsinks you added to the H bridge electrically isolated from the H bridge? You'll have to post a schematic showing how your MCU and its power supply is related to the H bridge.

 

[mpathma]

You shouldn't need more than a few uF for the microcontroller. If it requires more, then something isn't working right.

Are the heatsinks you added to the H bridge electrically isolated from the H bridge? You'll have to post a schematic showing how your MCU and its power supply is related to the H bridge.

I agree, without it I will be giving you *wrong medicine* which can worst your case.

M.Pathma

 

[Orson Cart]

take the heatsinks off, again, and power up briefly - this will tell you if the problem is RFI from the 'sinks is the root problem.

 

[stoyanoff]

The heatsinks are connected to the collectors of the IGBTs - IRG4PH30K . I used a silicon paste. I`ve tried to remove them. The device worked a little bit better. I added an extra capacitator (100uF). Now the first time when I start it it works for around 30 second and resets. After that ususally it works fine. Any suggestions???

 

[mtwieg]

It's almost certainly a layout issue then. You'll have to describe in detail (schematic) showing how the microcontroller is interfacing to the H bridge.