I am doing project on electrical vehicles. I need 400v from 120 v of batteries. I am testing my bidirectional converter in boost. I suddenly disconnect the load when the output volthage 350v. So the output voltage increase as witout load of boost converter. But it should to operate in buck mode when the voltage is 420v. When i disconnected the load at 350V suddenly. The boost converter configuration swithces burnt out. The voltage increases so rapidly that controller didnt take any decision to operate in buck mode. Can you tell me this is happened. Controller shoud take deciaion to operate it in buck. Should i not to remove the load suddenly on boost mode.

I need to operate the boost even the vehivles is stop. But its voltage will contanlty increase. What i have to do. Whar should i have to do for the unloaded condition in my vehicles.

  • \$\begingroup\$ Is this a shopping question or a design question? Is "my bidirectional converter" one of your own design? Or something you bought? Is there a schematic to see? Or not? \$\endgroup\$ – jonk Feb 10 '17 at 23:47
  • \$\begingroup\$ Put a small load on it\ big resistance \$\endgroup\$ – Voltage Spike Feb 11 '17 at 0:22
  • \$\begingroup\$ Big high-current inductors hold quite a bit of energy when you pass full load current through them. When you suddenly remove the load, the inductor is still full of energy and it wants to dump it somewhere. If it can't dump it into the intended load, the voltage across the inductor will keep rising until either it's dumped all it's energy into the output caps (raising the output voltage) or if the FETs are off, it'll keep cranking up the voltage until something gets fried. Needless to say, interrupting current in a big inductor is a good way to make high voltage spikes. \$\endgroup\$ – Sam Feb 11 '17 at 2:41
  • \$\begingroup\$ Dear Jonk . I built it myself . sorry \$\endgroup\$ – Fame313 Feb 11 '17 at 15:49
  • \$\begingroup\$ you are right dear @sam .. I want this converter for electical drive. i want to check if there is no load mean electrical vehicle is not being driven , \$\endgroup\$ – Fame313 Feb 11 '17 at 15:50

A boost converter stores energy in an inductor in the first part of the switching cycle. It releases that energy to the output capacitor in the second part of the cycle. Energy is transferred at the switching frequency and this becomes a power transfer.

So, a boost converter is a power regulator and doesn't regulate voltage without a feedback system that controls the duty cycle. If the load disappears the duty cycle must instantly become zero or the output voltage will continually rise until something breaks down.

Do you think that this might be happening?


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