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 voltage 350v. So the output voltage increase as without 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 switches burnt out. The voltage increases so rapidly that controller didn't take any decision to operate in buck mode. Can you tell me this is happened. Controller should take decision to operate it in buck.

Should I not to remove the load suddenly on boost mode?

I need to operate the boost even when the vehicles is stopped. But its voltage will constantly increase.

What do I need to do? What should I do for the unloaded condition in my vehicles?

  • 1
    \$\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, 2017 at 23:47
  • \$\begingroup\$ Put a small load on it\ big resistance \$\endgroup\$
    – Voltage Spike
    Feb 11, 2017 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, 2017 at 2:41
  • \$\begingroup\$ Dear Jonk . I built it myself . sorry \$\endgroup\$
    – Fame313
    Feb 11, 2017 at 15:49
  • 1
    \$\begingroup\$ If it's your own design, edit your question with a schematic. The biggest single question is how much energy is in the inductor at its maximum current, and if you dumped all that energy into the output caps, what would the voltage rise be? \$\endgroup\$
    – TimWescott
    Dec 23, 2021 at 3:24

1 Answer 1


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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