| 摘要 |
PURPOSE:To increase a boosting speed by providing a MOSFET whose source connects to an output terminal of a boosting circuit and whose drain connects to a power terminal to the boosting circuit and connecting its gate to an output terminal of a differentiating circuit differentiating a boosting signal. CONSTITUTION:When a level of a boosting signal changes from L to H, an input voltage Vb of a differentiating circuit (a) changes from L to H, a capacitor C3 of the differentiating circuit (a) is charged accordingly, the voltage drives a gate of a MOSFET T1, and the MOSFET T1 is turned on untill the discharge of the capacitor C3 is finished, The discharge time is controlled to be less than a TD1(ON), a back Sate of the MOSFET T1 is connected to GND, then an output voltage VG1 of the boosting circuit rises steeply up to VCC-VT1, where VT1 is an ON voltage of the MOSFET T1 and boosted to the voltage VCC-VT1 or over, and the flowing to a power supply is prevented because the MOSFET T1 is turned off. Thus, the saturation time TR1(ON) untill the arrival to a saturation voltage VCP of the boosting circuit output is reduced. Thus, the boosting speed is quickened. |
