the picture below shows my design about driving DC motor with H bridge. There is one problem, for example, I turn on the U1B and U1A(use PWM to turn on U1B and the U1A is always turn on when I make the motor run backward), the motor works. But when I measure the signal on pin 2 of U2A, it has noise. That is to say each time(PWM) U1B switches on->motor switches on->the VCC will go a little down->the transistor Q3 will on for a very little time. So it has risk that the MOSFET will be shorted. I have try to make the VCC a little larger(more than 20V), then the MOSFET burnt. If the Vcc not so high, the MOSFET won't burn.
Could you give me some advice?(Make the U2A not be disturbed， so as to protect the circuit) Thanks!