Patent ID: 7075356
Filing Date: 2006-07-11
Classification: H02M

Abstract:
1. A charge pump circuit, comprising: first and second diodes interposed in series between an input portion for receiving a power source input to an object to be stepped up and an output portion for outputting a stepped up voltage such that a forward direction of each diode is directed to a side of the output portion; a capacitor interposed on a connecting path between a connecting portion of the first diode on a side of the output portion and a ground, the first diode being disposed on a side of the input portion with respect to the second diode, the capacitor having two connecting portions; a first switch for conducting and cutting a connecting path between one of the connecting portions of the capacitor and the ground; a second switch for conducting and cutting a connecting path between the one connecting portion of the capacitor and the input portion; and a driver for conducting the first switch and the second switch alternately in phases opposite to each other; wherein: a constant current charging and discharging circuit, using a first follower circuit and a second follower circuit, is arranged to be along a first path, through which a current flows when a connecting path between the one connecting portion of the capacitor and the ground is conducted by the first switch and a current from the input portion charges the capacitor, and along a second path, through which a current flows when the connecting path between the one connecting portion of the capacitor and the input portion is conducted by the second switch and the capacitor is discharged; the first follower circuit comprises: the second follower circuit comprises: a third resistor; a fourth resistor; and a third diode, wherein the third resistor, the fourth resistor, and the third diode are directly connected to each other by a first connecting point, and the first connecting point is directly connected to a base of the first transistor.