To provide a fast charge means for a capacitor in a negative bias generation circuit. A capacitor is present in a down converter in a negative bias generation circuit. In order to perform fast charge, the capacitance of the capacitor is reduced and a necessary amount of charge is minimized. On the other hand, an external capacitance provided separately from the capacitor in the down converter is coupled directly to a power supply voltage and charged. After the capacitor in the down converter is charged, the external capacitance and the capacitor in the down converter are coupled in parallel. Due to this, it is made possible to aim at both the increase in charge speed and the improvement of resistance to ripple noise.