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10 months ago in Power Electronics By Prajwal Sharma

Why does my buck converter output equal input voltage regardless of duty cycle?

I'm testing a buck converter. No matter what duty cycle I set, output voltage equals input. What's wrong?

All Answers (1 Answers In All)

By Nirav Answered 7 months ago

Your high-side switch is stuck on. The converter is in pass-through mode, not switching. Likely causes: 1) Gate drive failure—no signal to turn off the MOSFET. 2) Shoot-through—incorrect dead time causing both switches to conduct briefly, but if the high-side never turns off... 3) Faulty controller—no PWM output. Check gate signals with a scope. Ensure the freewheeling diode path is functional. Output should be V_out = D × V_in. If it's not switching, it's not regulating.

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