| 摘要 |
PURPOSE:To provide a linear change for the period of an output voltage waveform to the input voltage, by charging quickly the capacity up to the prescribed voltage according to the input voltage of the MOSFET and then charging the capacity with a certain charge current. CONSTITUTION:At the moment when the MOSFET is changed to a cut-off state and shifted to the 1st state from the 2nd state, the potential at the poit 15 is V15 0 (point 21). The time during which the V15 increases up to the point 23 is the time T1 of the 1st state. When the threshold voltage of the MOSFET7 is set to VT7, the capacity 10 is charged quickly through the MOSFET7 up to the point 22 where V15=VIN (input potential)-VT7 is obtained. After this, the capacity is charged by the MOSFET5 up to the point 23. As the charge current of the quick charge is nearly constant, the time of change from point 22 to 23 is proportional to the difference of potential VA-(VIN-VT7) at V15. Thus the time T1 of the 1st state can also be regarded to be proportional to VA - (VIN-VT7). Accordingly, the period T of the output waveform has a linear change to the input voltage VIN. |
