| 摘要 |
PURPOSE:To prevent the fluctuations of oscillation frequency at the high voltage and prevent the time deviation of the crystal oscillation type electronic watch by performing changing-over of an oscillation frequency adjusting capacitor in a crystal oscillation circuit according to the results of the detection of a high voltage detection circuit. CONSTITUTION:When a silver battery 43 is at 1.57V, an overcharging preventing circuit 42 opens and the charging current is supplied from solar batteries 41. The P channel MOS 44f and N channel MOS 44c in a high voltage detection circuit 44 go ON according to the sampling pulses from a time counter circuit 47. At the time when the silver battery 43 is at 1.57V, the ON resistance of the P channel MOS 44f is large and the oscillation capacitor 46j in a crystal oscillation circuit 46 is used but when the silver battery 43 becomes 1.8V, the overcharging preventing circuit 42 closes to cut off the charging current and at the same time the ON resistance of the PMOS 44f becomes small and the oscillation capacitor 46j in the crystal oscillation circuit 46 is used, whereby the fluctuations of the oscillation frequency may be prevented. |
