A power circuit includes a control unit, a logic control circuit, a first driver amplifier, a second driver amplifier and a logic determination circuit. The control unit is used to output a pulse width modulation (PWM) signal and an enable (EN) signal. The logic control circuit receives the PWM signal and the EN signal, and outputs a first voltage signal and a second voltage signal. The first driver amplifier receives the first voltage signal, and outputs a first gate (UGATE) drive signal. The second driver amplifier receives the second voltage signal, and outputs a second gate (LGATE) drive signal. The logic determination circuit receives the PWM signal and the first and second gate drive signals. When the PWM signal and the first and second gate drive signals meet an abnormal logical relation, the logic determination circuit disables the logic control circuit.