# High output of NCP5104 (half bridge driver) is active in dead time zone. How can I solve it?

I try to drive BLDC motor. I have a problem in gate driver circuit. I use three NCP5104 gate driver. NCP5104 has 520ns internally fixed dead time. "The dead time is the time between the high side and low side output signal to avoid any cross conduction."@Delphesk But in my circuit, high output of NCP5104 (half bridge driver) is active in dead time zone. How can I solve it ?

• Back EMF. That voltage is generated by the motor. There is no "solve". Substitute a load resistor (or three, wired as a "Y" ) instead of the motor to see... – Brian Drummond Jan 10 at 12:18

What you are probably seeing is an effect of the back emf from your BLDC motor. It certainly doesn't mean that Q18 is "on" during the dead-band period. The bootstrapping in the driver chip is ensuring that $$\V_{GS}\$$ is zero in that dead-band period.