VOLTAGE BOOSTER CIRCUIT OF SMALL SIZE ELECTRONIC APPARATUS

PURPOSE:To obtain a DC boosting voltage and realize reduction in size of apparatus without increasing the number of additional parts by utilizing a first MOS transistor and a second MOS transistor having different types of conductivity and opening the printed circuit board of the second MOS transistor. CONSTITUTION:In a voltage booster circuit 30, when a PMOS transistor 31 is in the on state, a current flows into a coil 33 and an NMOS transistor 34 is in the off state. When the PMOS transistor 31 turns off, a negative voltage due to an inverse electromotive force of the coil 33 is generated at an external terminal 33. In this case, the NMOS transistor 34 becomes conductive to negatively charge a capacitor 36. With repetition of a clock signal T for voltage boosting, a charging capacitance of the capacitor 36 increases, a voltage of the external terminal 35 is negatively boosted and the inverse electromotive force of the coil 33 is balanced with the power consumed from the boosting power supply. Here, if capacitance of the capacitor 36 is sufficiently large, a boosting voltage VL can be considered as almost direct current.