| 摘要 |
A charge pump circuit 31a of the present invention includes: a step-up capacitor Cc2 charged and discharged in repeated cycles; a charger (SW2a to SW2c) that makes a first end T2a of the step-up capacitor Cc2 conduct to an input voltage VR application terminal and makes a second end T2b of the step-up capacitor Cc2 conduct to a ground terminal GND; a first discharger (SW3a and SW3b) that makes the first end T2a of the step-up capacitor Cc2 conduct to a positive voltage output terminal T3 and makes T2b conduct to VR; a second discharger (SW4a and SW4b) that makes T2a conduct to GND and makes T2b conduct to a negative voltage output terminal T4; a first output capacitor Co1 connected to T3, and a second output capacitor Co2 connected to T4. Each time charging of the step-up capacitor is completed, outputting of a positive voltage by the first discharger and outputting of a negative voltage by the second discharger are alternated. It is preferable that a ratio of the charge period of the step-up capacitor Cc2 to the output periods of the output voltages VGH and VGL be variably controlled. It is preferable that, between the backgate of the SW2c and GND, a switch SW5a be connected that is kept on when the step-up capacitor Cc2 is charged and is kept off otherwise. |
