| 摘要 |
PURPOSE:To ensure the stable drive of a semiconductor switch element without increasing the power loss of a resistance by short-circuiting a part of a series resistance when the charging voltage is less than a prescribed level. CONSTITUTION:When the voltage of a DC power supply 1 has a drop, the voltage of a capacitor C1 is also reduced less than the Zener voltage of a Zener diode DZIA. As a result, the non-inverted input voltage of a comparator 6 is reduced less than the inverted input. Therefore the output of the comparator 6 is set at level ''O'', and a current flows to a photodiode PD3. Thus a phototransistor PT3 is turned on. Then only an R5 has the charging resistance of the C1, and therefore the charging current increases. Thus the voltage of the C1 can be increased. In other words, a switch circuit using the PT3 is acutuated in response to the voltage of the C1 to switch the charging resistance. Thus a satisfactory charging resistance is always obtained. |
